Co-reporter:Guiran Pan, Yimin Yao, Xiaoliang Zeng, Jiajia Sun, Jiantao Hu, Rong Sun, Jian-Bin Xu, and Ching-Ping Wong
ACS Applied Materials & Interfaces September 27, 2017 Volume 9(Issue 38) pp:33001-33001
Publication Date(Web):September 5, 2017
DOI:10.1021/acsami.7b10115
Inspired by the microstructures of naturally layered and highly oriented materials, such as natural nacre, we report a thermally conductive polymer composite that consists of epoxy resin and Al2O3 platelets deposited with silver nanoparticles (AgNPs). Owing to their unique two-dimensional structure, Al2O3 platelets are stacked together via a hot-pressing technique, resulting in a brick-and-mortar structure, which is similar to the one of natural nacre. Moreover, the AgNPs deposited on the surfaces of the Al2O3 platelets act as bridges that link the adjacent Al2O3 platelets due to the reduced melting point of the AgNPs. As a result, the polymer composite with 50 wt % filler achieves a maximum thermal conductivity of 6.71 W m–1 K–1. In addition, the small addition of AgNPs (0.6 wt %) minimally affects the electrical insulation of the composites. Our bioinspired approach will find uses in the design and fabrication of thermally conductive materials for thermal management in modern electronics.Keywords: Al2O3 platelets; layered polymer composites; natural nacre; silver nanoparticles; thermal conductivity;
Co-reporter:Yuan Zhang, Yougen Hu, Pengli Zhu, Fei Han, Yu Zhu, Rong Sun, and Ching-Ping Wong
ACS Applied Materials & Interfaces October 18, 2017 Volume 9(Issue 41) pp:35968-35968
Publication Date(Web):September 27, 2017
DOI:10.1021/acsami.7b09617
Flexible pressure sensors are one of the vital component units in the next generation of wearable electronics for monitoring human physiological signals. In order to improve the sensing properties of the sensors, we demonstrate flexible, tunably resistive pressure sensors based on elastic microstructured polydimethylsiloxane (PDMS) film via a simple, low-cost colloid self-assembly technology, which uses monodispersed polystyrene (PS) microspheres as monolayer and an ordered sacrificial template. The sensors exhibit high sensitivity of −15 kPa–1 under low pressure (<100 Pa), with fast response time (<100 ms), high stability over 1000 cycles of pressure loading/unloading, low-pressure detection limit of 4 Pa, and wide working pressure regime (<5 kPa) by optimizing the size of PS microspheres. Moreover, the multipixel arrays of the pressure sensor are fabricated to illustrate the sensing ability of space pressure distribution. The developed flexible pressure sensors are successfully used to detect human neck pulse, show great promise for monitoring human body motions, and have potential applications in wearable devices.Keywords: microdome-patterned films; polystyrene microspheres; resistive pressure sensors; self-assembly; tunable sensitivity;
Co-reporter:Xiaoliang Zeng, Jiajia Sun, Yimin Yao, Rong Sun, Jian-Bin Xu, and Ching-Ping Wong
ACS Nano May 23, 2017 Volume 11(Issue 5) pp:5167-5167
Publication Date(Web):April 12, 2017
DOI:10.1021/acsnano.7b02359
With the current development of modern electronics toward miniaturization, high-degree integration and multifunctionalization, considerable heat is accumulated, which results in the thermal failure or even explosion of modern electronics. The thermal conductivity of materials has thus attracted much attention in modern electronics. Although polymer composites with enhanced thermal conductivity are expected to address this issue, achieving higher thermal conductivity (above 10 W m–1 K–1) at filler loadings below 50.0 wt % remains challenging. Here, we report a nanocomposite consisting of boron nitride nanotubes and cellulose nanofibers that exhibits high thermal conductivity (21.39 W m–1 K–1) at 25.0 wt % boron nitride nanotubes. Such high thermal conductivity is attributed to the high intrinsic thermal conductivity of boron nitride nanotubes and cellulose nanofibers, the one-dimensional structure of boron nitride nanotubes, and the reduced interfacial thermal resistance due to the strong interaction between the boron nitride nanotubes and cellulose nanofibers. Using the as-prepared nanocomposite as a flexible printed circuit board, we demonstrate its potential usefulness in electronic device-cooling applications. This thermally conductive nanocomposite has promising applications in thermal interface materials, printed circuit boards or organic substrates in electronics and could supplement conventional polymer-based materials.Keywords: boron nitride nanotubes; cellulose nanofibers; interfacial thermal resistance; nanocomposites; thermal conductivity;
Co-reporter:Songfang Zhao, Jinhui Li, Duxia Cao, Guoping Zhang, Jia Li, Kui Li, Yang Yang, Wei Wang, Yufeng Jin, Rong Sun, and Ching-Ping Wong
ACS Applied Materials & Interfaces April 12, 2017 Volume 9(Issue 14) pp:12147-12147
Publication Date(Web):March 10, 2017
DOI:10.1021/acsami.6b13800
Stretchable and flexible sensors attached onto the surface of the human body can perceive external stimuli, thus attracting extensive attention due to their lightweight, low modulus, low cost, high flexibility, and stretchability. Recently, a myriad of efforts have been devoted to improving the performance and functionality of wearable sensors. Herein, this review focuses on recent remarkable advancements in the development of flexible and stretchable sensors. Multifunction of these wearable sensors is realized by incorporating some desired features (e.g., self-healing, self-powering, linearity, and printing). Next, focusing on the characteristics of carbon nanomaterials, nanostructured metal, conductive polymer, or their hybrid composites, two major strategies (e.g., materials that stretch and structures that stretch) and diverse design approaches have been developed to achieve highly flexible and stretchable electrodes. Strain sensing performances of recently reported sensors indicate that the appropriate choice of geometric engineering as well as intrinsically stretchable materials is essential for high-performance strain sensing. Finally, some important directions and challenges of a fully sensor-integrated wearable platform are proposed to realize their potential applications for human motion monitoring and human–machine interfaces.Keywords: conductive network; desirable feature; flexible and stretchable electrodes; sensing mechanism; wearable sensor;
Co-reporter:Yaqiang Ji, Jiao Liu, Xiaonan Liu, Matthew M.F. Yuen, Xian-Zhu Fu, Ying Yang, Rong Sun, Ching-Ping Wong
Electrochimica Acta 2017 Volume 248(Volume 248) pp:
Publication Date(Web):10 September 2017
DOI:10.1016/j.electacta.2017.07.100
•3D hierarchically porous Cu@Cu2O films are fabricated by a facile method.•Pd nanoparticles are in-situ grown on the 3D hierarchical porous Cu-Cu2O films.•Porous Cu@Cu2O-Pd electrodes demonstrate excellent electrocatalytic activity for glucose oxidation.3D hierarchically porous Cu@Cu2O films supported Pd nanoparticles with excellent electrocatalytic activity are synthesized through electrochemical deposition, anodic oxidation and redox growth. Enzyme-free glucose biosensors based on the porous Cu@Cu2O-Pd electrodes exhibit higher sensitivity (1.157 mA cm−2 mM−1) than those of the porous Cu@Cu2O films (0.607 mA cm−2 mM−1), porous Cu films (0.507 mA cm−2 mM−1) and Pd nanoparticles (0.107 mA cm−2 mM−1). The enhanced activity of the porous Cu@Cu2O-Pd nanostructures might be attributed to the unique hierarchical porous structures with highly exposed active sites and synergetic effect from metal oxide semiconductor Cu2O and noble metal Pd.Download high-res image (130KB)Download full-size image
Co-reporter:Wangping Huang, Jinhui Li, Songfang Zhao, Fei Han, Guoping Zhang, Rong Sun, Ching-Ping Wong
Composites Science and Technology 2017 Volume 146(Volume 146) pp:
Publication Date(Web):7 July 2017
DOI:10.1016/j.compscitech.2017.04.030
Copper nanowires (CuNWs) have been considered for the promising application as conductive element of stretchable conductors due to ultrahigh aspect ratio, outstanding conductivity, great flexibility and low-cost. However, controllable synthesis, surface oxidation, poor dispersity have always been main limitations to their application in stretchable conductors. Herein, highly conductive, stretchable and fully printable CuNWs-based composites (PNCNs) by infiltrating CuNWs into poly(styrene-blockbutadiene-block-styrene) (SBS) with a facile, cost-effective and scalable method were reported. CuNWs of high quality, chemical treatment by vacuum filtration way and special dispersion method facilitate fabrication of PNCNs of high performance. As-prepared PNCNs have superior electrical conductivity of 1858 S cm−1, high break elongation of 920%. Moreover, PNCNs are stable after 1000 cycles for a bend radius of 4.0 mm and electric performance was not affected by twisting. Importantly, PNCNs can be printed on paper to fabricate flexible circuits which exhibit excellent electric performance at different tension conditions.
Co-reporter:Yan-Jun Wan, Peng-Li Zhu, Shu-Hui Yu, Rong Sun, Ching-Ping Wong, Wei-Hsin Liao
Carbon 2017 Volume 122(Volume 122) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.carbon.2017.06.042
Large-sized graphene sheets (LG) and doping strategy were employed to fabricate lightweight and flexible graphene paper with exceptional electromagnetic interference (EMI) shielding performance. Compared with the smaller sized ones, LG with fewer defects and more conjugated carbon domain size as well as better alignment result in higher electrical conductivity and strength of graphene paper. The iodine doping further improves the carrier density of LG by formation of triiodide (I3−) and pentaiodide (I5−) through charge transfer process without deteriorating the mechanical property, thus leading to superior EMI shielding effectiveness (SE). The EMI SE of iodine doped LG film with thickness of 12.5 μm is up to ∼52.2 dB at 8.2 GHz, which is much higher than that of undoped LG with the same thickness (∼47.0 dB). More important, the improvements in EMI SE is contributed to the SE absorption, while the SE reflection is almost unchanged. The mechanisms of improved EMI shielding performance as well as mechanical property were investigated and discussed. The present study provides a facile way to fully develop graphene in lightweight and flexible EMI shielding materials and devices.Large-size graphene oxide sheets combined with doping strategy were employed to improve the carrier mobility and carrier density of graphene. Flexible iodine-doped graphene film with exceptional EMI shielding performance was fabricated and investigated. The doped graphene paper assembled by large-sized sheets possesses higher electrical conductivity and shows EMI shielding effectiveness (SE) as high as ∼ 52.2 dB with thickness of ∼12.5 μm, which is much higher than most of reported results with the same thickness and the improvement in EMI SE is contributed to the SE absorption, while the SE reflection is almost unchanged. Furthermore, the mechanical properties can be maintained very well after the doping process. This study opens a new idea to fully develop graphene in lightweight and flexible EMI shielding materials and devices.Download high-res image (239KB)Download full-size image
Co-reporter:Bo Zhao;Xian-Zhu Fu;Ching-Ping Wong
Sustainable Energy & Fuels (2017-Present) 2017 vol. 1(Issue 10) pp:2145-2154
Publication Date(Web):2017/11/21
DOI:10.1039/C7SE00399D
Efficient heat dissipation is a crucial issue for electrochemical energy storage devices like supercapacitors. A large amount of heat is generated during the charging and discharging processes, especially at high current densities. This significantly accelerates capacity fading and serious safety problems such as explosions might occur for energy storage devices, and it can also cause human discomfort and even skin burns for wearable electronic or implantable electronic devices if the heat does not dissipate efficiently. In this contribution, highly thermally conductive electrodes based on graphene–MnO2 films are developed, which demonstrate high thermal conductivity of 613.5 W m−1 K−1 relative to that of 1.1 W m−1 K−1 of the traditional MnO2 slurry electrodes. The high thermal conductivity film electrode-based supercapacitor not only exhibits excellent heat dissipation ability during the charging and discharging processes, which is beneficial for the thermal management of supercapacitor devices, but also good cycling performance and excellent rate capacity for a high specific capacity of about 218.8 F g−1 at a high current density of 10 A g−1.
Co-reporter:Tao Huang;Xiaoliang Zeng;Yimin Yao;Fanling Meng;Jianbin Xu;Chingping Wong
RSC Advances (2011-Present) 2017 vol. 7(Issue 38) pp:23355-23362
Publication Date(Web):2017/04/27
DOI:10.1039/C6RA28503A
In recent decades, significant attention has been focused on developing composite materials with high thermal conductivity utilizing h-BN, which has outstanding thermal conductivity. However, the enhancement in thermal conductivity by using h-BN is commonly limited because of high thermal resistance between h-BN and polymer materials. Herein, we fabricated novel h-BN–RGO hybrids (h-BN–RGO), by electrostatic assembly between h-BN and GO. It is found that the addition of h-BN–RGO hybrids into epoxy resins can enhance the thermal conductivity. The samples containing 26.04 vol% h-BN–RGO exhibit the highest thermal conductivity (3.45 W m−1 K−1), which is as high as 16 times that of neat epoxy resin (0.24 W m−1 K−1). The epoxy resins/h-BN–RGO composites also exhibit an enhanced dielectric constant (11.12) and low loss tangents (0.05). The energy density of the composites reaches 0.51 J cm−3 in the composites with 26.04 vol%, which is 79.6% higher than that of the pure epoxy. We attribute the enhanced thermal conductivity to the well-designed h-BN–RGO interface as well as the good dispersion of BN–RGO hybrids in epoxy resin. The energy density is mainly due to the absorbed effect of RGO nanosheets at the BN surface and its good dispersion in comparison with pure BN. This work offers a new insight into the methods for the improvement of thermal conductivity and energy storage characteristics, which has potential applications in integrated circuit packaging and structural energy storage.
Co-reporter:Fei Han;Jinhui Li;Songfang Zhao;Yuan Zhang;Wangping Huang;Guoping Zhang;Ching-Ping Wong
Journal of Materials Chemistry C 2017 vol. 5(Issue 39) pp:10167-10175
Publication Date(Web):2017/10/12
DOI:10.1039/C7TC03636A
Stretchable strain sensors, as crucial components in wearable intelligent devices, have become one of the recent research hotspots with promising potential in human-interactive, personal health monitoring, and flexible smartphones. Graphene-based materials have been reported for high-performance strain sensors. However, there still remain some limitations such as their high production cost and low sensitivity and stretchability. Herein, a highly stretchable and ultra-sensitive strain sensor based on nickel nanoparticles and a graphene-coated polyurethane sponge (Ni@GPUS) ternary hybrid material has been reported. Herein, Ni@GPUS was fabricated via a series of techniques including preparation of a graphene-coated polyurethane sponge, electrodeposition of nickel nanoparticles, and encapsulation by polydimethylsiloxane. The obtained sensors can be stretched up to 65% and exhibit a remarkable gauge factor of up to 3360.09. Furthermore, a fast signal response (<100 ms) and 1000 cycles of stretching and bending prove the rapid steady state response and long-term durability of the sensor, respectively. In addition, the working mechanisms of the sensor have been proposed. Moreover, the strain sensor was used as a bodily motion sensor to monitor finger bending and facial muscle tension, showing great potential in the fields of flexible, stretchable, and wearable electronics.
Co-reporter:Suibin Luo;Yanbin Shen;Shuhui Yu;Yanjun Wan;Wei-Hsin Liao;Ching-Ping Wong
Energy & Environmental Science (2008-Present) 2017 vol. 10(Issue 1) pp:137-144
Publication Date(Web):2017/01/18
DOI:10.1039/C6EE03190K
Herein, the designed 3D-BaTiO3 network in polymer composites results in enhanced permittivity and energy storage density. High permittivities of 200 (εeff/εm ∼ 55.4) and 34.5 are achieved in the composites with only 30 vol% and 16 vol% 3D-BaTiO3, respectively. The latter exhibits a discharged energy density that is over 16 times larger than the polymer matrix.
Co-reporter:Xiaoliang Zeng;Yucheng Xiong;Qiang Fu;Jianbin Xu;Dongyan Xu;Ching-Ping Wong
Nanoscale (2009-Present) 2017 vol. 9(Issue 30) pp:10585-10589
Publication Date(Web):2017/08/03
DOI:10.1039/C7NR03717A
The ability to control thermal conductivity is important in a wide variety of applications, especially in heat removal, heat insulation, and thermoelectric energy conversion. Herein, we reveal that the thermal conductivity of epoxy resin fibers increases on decreasing the fiber diameter and surpasses the bulk value (0.25 W m−1 K−1 at 300 K) for the fiber with a diameter of 211 nm. The variation of thermal conductivity in epoxy resin fibers can likely be attributed to their microstructure change—enhanced interface phonon scattering between amorphous and crystalline regions and the enhanced alignment of the molecular chain orientation.
Co-reporter:Zhen Chen, Bo Zhao, Xian-Zhu Fu, Rong Sun, Ching-Ping Wong
Journal of Electroanalytical Chemistry 2017 Volume 807(Volume 807) pp:
Publication Date(Web):15 December 2017
DOI:10.1016/j.jelechem.2017.11.041
•The CuO-Pd exhibits a nanorod morphology.•The CuO-Pd nanorods show higher catalytic activity than CuO towards glucose.•The CuO-Pd nanorods display better anti-interference towards glucose detection.CuO nanorods supported Pd nanoparticles (CuO-Pd) are fabricated as highly active electrocatalysts. The current density for CuO-Pd is ca. 3.7 times than that of CuO and ca. 129.3 times of Cu(OH)2-Pd precursor towards glucose detection. Moreover, the CuO-Pd nanorods also display low detection limit, high sensitivity, wide linear range, fast response, high stability and anti-interference performance for glucose detection. The excellent electrocatalytic performance of CuO-Pd nanorods might be ascribed to the synergistic effect of CuO and noble metal Pd, which is promising for applications as nonenzymatic glucose sensors.CuO nanorods supported Pd nanoparticles are developed as electrocatalysts for glucose detection with greatly high catalytic activity of 14.6 mA cm− 2 and sensitivity of 2.5369 mA cm− 2 mM− 1.Download high-res image (116KB)Download full-size image
Co-reporter:Jiajia Sun;Yimin Yao;Xiaoliang Zeng;Guiran Pan;Jiantao Hu;Yun Huang;Jian-Bin Xu;Ching-Ping Wong
Advanced Materials Interfaces 2017 Volume 4(Issue 17) pp:
Publication Date(Web):2017/09/01
DOI:10.1002/admi.201700563
With the rapid development of modern electronics toward miniaturization, high-degree integration, and multifunctionalization, increased heat is generated during the operation of devices, which seriously limits the performance, lifetime, and reliability of electronic devices. Polymer-based composites with high thermal conductivity have attracted much attention in solving the heat dissipation issue. However, conventional polymer-based composites can hardly achieve a thermal conductivity of over 10 W m−1 K−1, due to high interfacial thermal resistance. Herein, engineering interfacial thermal resistance in boron nitride nanosheet/nanofibrillated cellulose nanocomposites by constructing nanoscale silver “bridges” between fillers is reported, aiming at achieving a high thermal conductivity. The highest in-plane thermal conductivity is up to 65.7 ± 3.0 W m−1 K−1, which is one order magnitude higher than those of conventional polymer-based composites. By fitting the experimental data with theoretical models, it is quantitatively demonstrated that silver nanoparticles can help to sharply decrease the interfacial thermal resistance between adjacent boron nitride nanosheets. In addition, the small amount of silver hardly affects the electrical insulation of boron nitride nanosheet/nanofibrillated cellulose nanocomposites. This strategy can potentially pave the way for the design and preparation of highly thermally conductive materials in the future.
Co-reporter:Yun Huang;Jiantao Hu;Yimin Yao;Xiaoliang Zeng;Jiajia Sun;Guiran Pan;Jian-Bin Xu;Ching-Ping Wong
Advanced Materials Interfaces 2017 Volume 4(Issue 17) pp:
Publication Date(Web):2017/09/01
DOI:10.1002/admi.201700446
Highly thermally conductive polymer composites have received considerable attention, along with development of electronic devices toward being more integrated, miniaturized, and functionalized. However, traditional polymer composites cannot meet the requirement of achieving higher thermal conductivity at relatively low filler loading. Herein, manipulating orientation of silicon carbide nanowire (SiCNW) in epoxy composites by coating method is reported to achieve high in-plane thermal conductivity (10.10 W m−1 K−1) at extremely low filler loading (5 wt%), while it is only 1.78 and 0.30 W m−1 K−1 for epoxy/random SiCNW composite and epoxy/silicon carbide nanoparticle composite. Several models are employed to demonstrate that a good orientation and high aspect ratio of SiCNWs contribute to form heat transfer networks in the composites. This provides a promising future for thermal-management materials, which are widely applied to electronic packaging, aerospace field, and medical engineering.
Co-reporter:Yimin Yao, Xiaoliang Zeng, Fangfang Wang, Rong Sun, Jian-bin Xu, and Ching-Ping Wong
Chemistry of Materials 2016 Volume 28(Issue 4) pp:1049
Publication Date(Web):January 25, 2016
DOI:10.1021/acs.chemmater.5b04187
Owing to the miniaturization of power electronics and the development of portable and flexible devices, demands for highly thermally conductive, mechanically flexible, and electrically insulating composites have substantially increased. However, the conventional method to improve thermal conductivity usually yields both an undesired value (usually below 10 W m–1 K–1) and poor flexibility. Thus, a combination of all the desired properties together remains a technical challenge. Bioinspired engineering offers great promise in the synthesis and fabrication of thermal materials that are different from engineering through conventional approaches. Inspired by the interface and orientation of natural nacre, we report on thermally conductive and mechanically flexible papers based on boron nitride nanosheets (BNNSs) and graphene oxide (GO) via a simple vacuum-assisted filtration process. We experimentally show that the papers possess high thermal conductivity of 29.8 W m–1 K–1, excellent mechanical flexibility, and satisfactory electrical insulation. We attribute the high thermal conductivity to the well-designed BNNS–GO interface as well as the advantageous orientation in layered structure. This approach to constructing thermally conductive composites provides a creative opportunity for design and fabrication of high-performance materials in the near future, and this kind of paper has great potential application in next-generation commercial portable electronics.
Co-reporter:Songfang Zhao, Jinhui Li, Duxia Cao, Yongju Gao, Wangping Huang, Guoping Zhang, Rong Sun and Ching-Ping Wong
Journal of Materials Chemistry A 2016 vol. 4(Issue 27) pp:6666-6674
Publication Date(Web):13 Jun 2016
DOI:10.1039/C6TC01728B
Conductive elastomers, an irreplaceable component of stretchable electronics, have recently gained significant attention. Herein, we report highly conductive, sensitive, stretchable, and fully printed hybrid composites comprising carbon nanotubes (CNTs), silver nanoparticles (Ag NPs) and hydroxyl-poly(styrene-block-butadiene-block-styrene) (OH-SBS) polymers. The electrically conductive composites are fabricated via direct evaporation of CNT-dispersed OH-SBS suspension under mild heating conditions, followed via an iterative process of silver precursor absorption and reduction, generating large amounts of Ag NPs on both the surface and inner regions of the CNT-embedded composites. The obtained CNT–Ag NP embedded composites possess a superior electrical conductivity of 1228 S cm−1, a high break elongation of 540%, and a high gauge factor of 26500. The unique hierarchical multiscale hybrid architecture of CNT–Ag NPs and the utilization of OH-SBS enable the as-prepared composites to exhibit huge piezoresistive behavior with a broad range of tensile strains. Moreover, handwritten electric circuits with diverse geometries are designed, and the printed strain gauge sensor could successfully detect sign language via its strain-sensing behavior. We believe that our hierarchical multiscale hybrid design could pave the way for the simple fabrication of stretchable circuits for wearable electronics.
Co-reporter:Xiaoliang Zeng, Libo Deng, Yimin Yao, Rong Sun, Jianbin Xu and Ching-Ping Wong
Journal of Materials Chemistry A 2016 vol. 4(Issue 25) pp:6037-6044
Publication Date(Web):31 May 2016
DOI:10.1039/C6TC01501H
Flexible polymer-based dielectric materials that are used to store dielectric energy have widely been used in modern electronics and electric power systems, due to their relatively high energy density, light weight, low cost, etc. However, owing to the growing global environmental issues and a rapid consumption of nonrenewable polymer resources, there exists a strong desire to fabricate flexible dielectric materials using biodegradable materials. Here, we report on flexible dielectric papers based on biodegradable cellulose nanofibers (CNFs) and carbon nanotubes (CNTs) for dielectric energy storage. Highly ordered, homogeneous CNF/CNT papers have been fabricated using a facile vacuum-assisted self-assembly technique. The obtained paper possesses a high dielectric constant of 3198 at 1.0 kHz, thus leading to enhanced dielectric energy storage capability (0.81 ± 0.1 J cm−3), which is attributed to the presence of a low loading of CNTs (4.5 wt%). Moreover, the CNF/CNT papers are mechanically flexible and show improved mechanical strength. These findings enable feasible fabrication of high-performance flexible dielectric materials using ecofriendly materials.
Co-reporter:Yimin Yao, Xiaoliang Zeng, Rong Sun, Jian-Bin Xu, and Ching-Ping Wong
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 24) pp:15645-15653
Publication Date(Web):June 2, 2016
DOI:10.1021/acsami.6b04636
The rapid development of modern electronics and three-dimensional integration sets stringent requirements for efficient heat removal of thermal-management materials to ensure the long lifetime of the electronics. However, conventional polymer composites that have been used widely as thermal-management materials suffer from undesired thermal conductivity lower than 10 W m–1 K–1. In this work, we report a novel thermally conductive composite paper based on the thought of bioinspired engineering. The advantage of the bioinspired papers over conventional composites lies in that they possess a very high in-plane thermal conductivity up to 21.7 W m–1 K–1 along with good mechanical properties and high electrical insulation. We attribute the high thermal conductivity to the improved interfacial interaction between assembled components through the introduction of silver nanoparticles and the oriented structure based on boron nitride nanosheets and silicon carbide nanowires. This thought based on bioinspired engineering provides a creative opportunity for design and fabrication of novel thermally conductive materials, and this kind of composite paper has potential applications in powerful integrated microelectronics.
Co-reporter:Jinhui Li, Songfang Zhao, Xiaoliang Zeng, Wangping Huang, Zhengyu Gong, Guoping Zhang, Rong Sun, and Ching-Ping Wong
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 29) pp:18954-18961
Publication Date(Web):July 6, 2016
DOI:10.1021/acsami.6b05088
Wearable strain sensors with excellent stretchability and sensitivity have emerged as a very promising field which could be used for human motion detection and biomechanical systems, etc. Three-dimensional (3D) graphene foam (GF) has been reported before for high-performance strain sensors, however, some problems such as high cost preparation, low sensitivity, and stretchability still remain. In this paper, we report a highly stretchable and sensitive strain sensor based on 3D GF and polydimethylsiloxane (PDMS) composite. The GF is prepared by assembly process from graphene oxide via a facile and scalable method and possesses excellent mechanical property which facilitates the infiltration of PDMS prepolymer into the graphene framework. The as-prepared strain sensor can be stretched as high as 30% of its original length and the gauge factor of this sensor is as high as 98.66 under 5% of applied strain. Moreover, the strain sensor shows long-term stability in 200 cycles of stretching-relaxing. Implementation of the device for monitoring the bending of elbow and finger results in reproducibility and various responses in the form of resistance change. Thus, the developed strain sensors exhibit great application potential in fields of biomechanical systems and human-interactive applications.
Co-reporter:Yimin Yao, Xiaoliang Zeng, Guiran Pan, Jiajia Sun, Jiantao Hu, Yun Huang, Rong Sun, Jian-Bin Xu, and Ching-Ping Wong
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 45) pp:31248
Publication Date(Web):October 27, 2016
DOI:10.1021/acsami.6b10935
Polymer composites with high thermal conductivity have attracted much attention, along with the rapid development of electronic devices toward higher speed and better performance. However, high interfacial thermal resistance between fillers and matrix or between fillers and fillers has been one of the primary bottlenecks for the effective thermal conduction in polymer composites. Herein, we report on engineering interfacial structure of silicon carbide nanowire/cellulose microcrystal paper by generating silver nanostructures. We show that silver nanoparticle-deposited silicon carbide nanowires as fillers can effectively enhance the thermal conductivity of the matrix. The in-plane thermal conductivity of the resultant composite paper reaches as high as 34.0 W/m K, which is one order magnitude higher than that of conventional polymer composites. Fitting the measured thermal conductivity with theoretical models qualitatively demonstrates that silver nanoparticles bring the lower interfacial thermal resistances both at silicon carbide nanowire/cellulose microcrystal and silicon carbide nanowire/silicon carbide nanowire interfaces. This interfacial engineering approach provides a powerful tool for sophisticated fabrication of high-performance thermal-management materials.Keywords: interfacial engineering; microcrystal paper; silicon carbide nanowires; thermal conductivity
Co-reporter:Bo Zhao, Yi-Tao Xu, Sheng-Yun Huang, Kai Zhang, Matthew M.F. Yuen, Jian-Bin Xu, Xian-Zhu Fu, Rong Sun, Ching-Ping Wong
Electrochimica Acta 2016 Volume 202() pp:186-196
Publication Date(Web):1 June 2016
DOI:10.1016/j.electacta.2016.04.032
Three-dimensional (3D) reduced graphene oxide (RGO) frameworks confined hollow spherical SnO2-Fe2O3@RGO nano-shells (3D h-SnO2-Fe2O3@RGO) are successfully obtained by hydrothermal reduction of h-SnO2-Fe2O3@GO in graphene oxide (GO) suspension. As anode materials for lithium-ion batteries (LIBs), the novel 3D h-SnO2-Fe2O3@RGO architectures demonstrate great improvement in cycling performance (∼830 mAh g−1 after 100 cycles at 200 mA g−1) and rate capability (∼550 mAh g−1 at 1000 mA g−1for 10 cycles) over that of hollow SnO2 spheres (h-SnO2), h-SnO2-Fe2O3, and 3D RGO frameworks wrapped hollow spherical SnO2@RGO nano-shells (3D h-SnO2@RGO). The 3D porous frameworks and coating graphene nano-shells serve as efficient electron and ion conductive networks as well as buffer for the large volume variation of hollow SnO2-Fe2O3 during cycling. Moreover, the hollow spherical metal oxide mesoporous nano-shells could enlarge the surface area, retard the volume change, prevent aggregation of nanosized active materials and graphene nanosheets.
Co-reporter:Bo Zhao, Tao Wang, Li Jiang, Kai Zhang, Matthew M.F. Yuen, Jian-Bin Xu, Xian-Zhu Fu, Rong Sun, Ching-Ping Wong
Electrochimica Acta 2016 Volume 192() pp:205-215
Publication Date(Web):20 February 2016
DOI:10.1016/j.electacta.2016.01.211
Uniform NiO mesoporous nanowalls are easily fabricated on reduced graphene oxide (RGO) nanosheets coated three dimensional nickel foams (3D NF-G) through a simple aqueous deposition with successive annealing. The structure and morphology of the resulting NiO nanowalls supported on 3D NF-G composites (3D NF-G-NiO) are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX). The 3D NF-G-NiO composites are directly used as binder-free electrodes for supercapacitors and biosensors. For supercapacitor, the electrode delivers high specific capacitance of about 950 F g−1 at a current density of 5 A g−1 with excellent cycling stability. As glucose sensor, the 3D NF-G-NiO electrode can detect glucose with an ultrahigh sensitivity of 3.23 mAmM−1 cm−2 and a superior selectivity with a remarkable lower detection limit towards 10 μM.
Co-reporter:Chengliang Li, Shuhui Yu, Suibin Luo, Wenhu Yang, Zaochuan Ge, Haitao Huang, Rong Sun and Ching-Ping Wong
RSC Advances 2016 vol. 6(Issue 43) pp:36450-36458
Publication Date(Web):05 Apr 2016
DOI:10.1039/C6RA03469A
Cu nanoparticles with diameters of 15–25 nm were grown discretely on the surface of BaTiO3 (about 100 nm) via a hydrothermal method, and a polyethylene glycol 4000 layer was coated on the surface of the obtained BT–Cu hybrid particles. The PEG layer will serve as a robust interface layer to suppress the mobilization of charge carriers and protect Cu from oxidation. The BT–Cu particles were loaded as fillers in the matrix of polyvinylidene fluoride (PVDF) to fabricate the BT–Cu/PVDF composites. Microstructure and dielectric performance have been investigated. The results showed that the relative permittivity (εr) of the composites increased prominently with the loading amount and meanwhile the dielectric loss tangent was suppressed at a low level. For instance, the permittivity of BT–Cu/PVDF with the volume fraction of 53.7% reached 150 with a low loss of 0.16 at 1 kHz. The permittivities maintained high values of over 55 and the dielectric loss was less than 0.05 upto 1 GHz. Investigation on the polarization mechanisms has been conducted and the interfacial polarization between different phases should account for the high dielectric permittivity upto GHz. The energy storage characteristics were also studied.
Co-reporter:Leicong Zhang, Pengli Zhu, Fengrui Zhou, Wenjin Zeng, Haibo Su, Gang Li, Jihua Gao, Rong Sun, and Ching-ping Wong
ACS Nano 2016 Volume 10(Issue 1) pp:1273
Publication Date(Web):December 22, 2015
DOI:10.1021/acsnano.5b06648
In this study, a flexible asymmetrical all-solid-state supercapacitor with high electrochemical performance was fabricated with Ni/MnO2—filter paper (FP) as the positive electrode and Ni/active carbon (AC)—filter paper as negative electrode, separated with poly(vinyl alcohol) (PVA)–Na2SO4 electrolyte. A simple procedure, such as electroless plating, was introduced to prepare the Ni/MnO2–FP electrode on the conventional laboratory FP, combined with the subsequent step of electrodeposition. Electrochemical results show that the as-prepared electrodes display outstanding areal specific capacitance (1900 mF/cm2 at 5 mV/s) and excellent cycling performance (85.1% retention after 1000 cycles at 20 mA/cm2). Such a flexible supercapacitor assembled asymmetrically in the solid state exhibits a large volume energy density (0.78 mWh/cm3) and superior flexibility under different bending conditions. It has been demonstrated that the supercapacitors could be used as a power source to drive a 3 V light-emitting diode indicator. This study may provide an available method for designing and fabricating flexible supercapacitors with high performance in the application of wearable and portable electronics based on easily available materials.Keywords: electroless plating; filter paper; flexible supercapacitor; MnO2; polymer electrolyte;
Co-reporter:Jiawei Zhang;Guoping Zhang;Yongju Gao
Journal of Materials Science 2016 Volume 51( Issue 17) pp:7966-7976
Publication Date(Web):2016 September
DOI:10.1007/s10853-016-0066-6
A novel bridged organosilane precursor with star-shaped construction, [hexfluoropropane-2,2-diyl)dibenzyl-bridged organosilane (HFPDBO)], is prepared by facile organic synthesis method. The resultant HFPDBO precursor is mixed with porogen and acid catalyst to prepare periodic mesoporous organosilica (PMO) thin film via evaporation-induced self-assembly after spin-coating procedure. All the as-prepared HFPDB-based PMO thin film has been characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectrum, scanning electron microscopy,
transmission electron microscope, and small-angle X-ray diffraction, respectively. Thereinto, the HFPDB-based PMO thin film with weight ratio of porogen to precursor (0.75:1) possesses excellent dielectric property (1.58@1 MHz of dielectric constants), high mechanical property (5.54 ± 0.11 GPa of Young’s modulus) and hydrophobic property (90.1° of water contact angle) simultaneously. These low dielectric constant, high mechanical strength, and the hydrophobicity suggest potential application of the HFPDB-based PMO thin films as low-k materials in microelectronics.
Co-reporter:Wenhu Yang, Jian Wang, Suibin Luo, Shuhui YuHaitao Huang, Rong Sun, Ching-Ping Wong
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 51) pp:
Publication Date(Web):December 6, 2016
DOI:10.1021/acsami.6b11492
Overvoltage protection is becoming increasingly important because of miniaturization and multifunctionality of electronic devices. Flexible, easily processable materials with nonlinear and reversible I–V behavior are highly desired. In this study, hybrid nanoparticles of ZnO-decorated carbon nanotubes (CNT–ZnO) were synthesized via a sol–gel hydrothermal process employed in an epoxy matrix to prepare composites. Microstructure analysis demonstrated that ZnO nanoparticles were well-bonded to the surface of CNT. The CNT–ZnO/epoxy composites exhibited nonlinear I–V behavior under increasingly applied voltage with a nonlinear coefficient of 5.01 (10 wt % filler loading). More importantly, the composites possessed excellent reversibility from dielectric to conductor and vise versa in the recycling of increase and decrease of applied electric field, in contrast to the poor recoverability of pure CNT-filled epoxy. The mechanism of the nonlinear I–V behavior and reversibility was investigated and discussed. A simple circuit was fabricated, which verified well the protection function of the CNT–ZnO/polymer composites.Keywords: CNT−ZnO hybrids; device protection; nonlinear I−V behavior; polymer composites; voltage switchable dielectrics;
Co-reporter:Jian Wang, Shuhui Yu, Suibin Luo, Baojin Chu, Rong Sun, Ching-Ping Wong
Materials Science and Engineering: B 2016 Volume 206() pp:55-60
Publication Date(Web):April 2016
DOI:10.1016/j.mseb.2016.01.004
•Mechanism of nonlinear behavior of the CNT composites was systematically investigated.•There are one linear region (I) and two nonlinear regions (II and III) in the I–V curves.•This phenomenon was analyzed based on hopping, tunneling and Joule heating effects.Nonlinear current–voltage (I–V) behavior is a typical feature of polymeric composites containing conductor or semiconductor fillers, which are desired to handle the transient voltage and electrostatic discharge (ESD) of microelectronic devices. In this paper, the mechanism of nonlinear behavior of carbon nanotubes (CNTs) filled polymer composites in the applied electric field was explored. The I–V curves of the composites exhibited three regions. The variation of current at low voltages (region I) is linear. Under relatively higher voltages (region II), the variation is nonlinear and grows rapidly with voltage. As the voltage is further increased, the I–V curve is still non-linear (region III), but the growth rate is significantly slowed down. The I–V characteristics in the above three regions were analyzed systematically based on the calculation of the electrons hopping from the conduction band of CNTs to epoxy, the induced current under electric field, as well as Joule-heating and tunneling effect.
Co-reporter:Xiaoliang Zeng;Lei Ye;Kun Guo;Jianbin Xu;Ching-Ping Wong
Advanced Electronic Materials 2016 Volume 2( Issue 5) pp:
Publication Date(Web):
DOI:10.1002/aelm.201500485
Flexible substrates that host electronic components are an essential part of flexible electronics. The continuing miniaturization of these electronics requires flexible substrates with excellent flexibility, high thermal conductivity, and low dielectric constant. However, to combine these intended properties remains a daunting challenge. Here, a flexible fibrous epoxy substrate fabricated by an electrospinning technique is reported, which exhibits excellent flexibility, high thermal conductivity, and low dielectric constant. The thermal conductivity can be tuned by varying the diameter of fibers and can reach values as high as 0.8 W m−1 K−1, which is about three times higher than that of casted epoxy substrate fabricated by spin-coating. This excellent performance is attributed to polymer molecular chain alignment and fibrous structure that are formed during electrospinning. Demonstrative applications suggests its broad potential uses in future flexible electronics.
Co-reporter:Xiaoliang Zeng, Lei Ye, Shuhui Yu, Rong Sun, Jianbin Xu, and Ching-Ping Wong
Chemistry of Materials 2015 Volume 27(Issue 17) pp:5849
Publication Date(Web):August 18, 2015
DOI:10.1021/acs.chemmater.5b00505
As a structural analogue of graphene, boron nitride nanosheets (BNNSs) have attracted ever-growing research interest in the past few years, due to their remarkably mechanical, electrical, and thermal properties. The preparation of BNNS aerogels is considered to be one of the most effective approaches for their practical applications. However, it has remained a great challenge to fabricate BNNS aerogels with superelasticity by a facile method. Here, we report the preparation of BNNS aerogels via a facile method involving polymer-assisted cross-linking and freeze-casting strategies. The resulting aerogels exhibit a well-ordered and anisotropic microstructure, leading to anisotropic superelasticity, high compressive strength, and excellent energy absorption ability. The unique microstructure also endows the aerogels with ultralow dielectric constant (1.24) and loss (∼0.003). The successful fabrication of such fascinating materials paves the way for application of BNNSs in energy-absorbing services, catalyst carrier, and environmental remediation, etc.
Co-reporter:Tao Wang, Bo Zhao, Hong Jiang, Hai-Peng Yang, Kai Zhang, Matthew M. F. Yuen, Xian-Zhu Fu, Rong Sun and Ching-Ping Wong
Journal of Materials Chemistry A 2015 vol. 3(Issue 45) pp:23035-23041
Publication Date(Web):28 Sep 2015
DOI:10.1039/C5TA04705F
Ternary cobalt nickel sulfide (CoNi2S4) flower-like nanosheets are directly grown on three dimensional (3D) hierarchically porous nickel skeletons by one-step electro-deposition. The resultant 3D porous Ni/CoNi2S4 composites could serve as binder-free integrated electrodes for supercapacitors, which exhibit higher capacitance than those of 3D porous Ni/Co9S8, 3D porous Ni/Ni3S2, Ni foam/CoNi2S4 and smooth Ni/CoNi2S4 electrodes. Furthermore, the 3D porous Ni/CoNi2S4 electrodes demonstrate better electrochemical reversibility and excellent rate capability. The super electrochemical capacitive behavior might be attributed to the highly interconnected conductive networks of 3D hierarchically porous Ni scaffold supported CoNi2S4 flower-like nanosheets with a large specific area and highly active sites.
Co-reporter:Jinhui Li, Songfang Zhao, Guoping Zhang, Yongju Gao, Libo Deng, Rong Sun and Ching-Ping Wong
Journal of Materials Chemistry A 2015 vol. 3(Issue 30) pp:15482-15488
Publication Date(Web):16 Jun 2015
DOI:10.1039/C5TA03595C
Endowing graphene sponge with compressibility and conductivity offers the possibility to regenerate piezoresistivity and is therefore of great interest in the field of sensors. In this work, highly compressible three-dimensional graphene-only sponge (CGS) was prepared through a facile method by using ammonium sulfide and ammonia solutions under mild conditions. The morphologies and microstructures of the as-prepared CGSs can be controlled by adjusting the mass ratio of graphene oxide (GO) to ammonium sulfide which changed from a metallic sheen bulk with a leaf-shaped structure to a black sponge with a porous structure. Besides, by simply changing the concentrations of GO, CGSs with different porosity, conductivity as well as mechanical strength were obtained. Moreover, the resultant CGSs show ultralow density (as low as 4.9 mg cm−3), high porosity (as much as 99.8%), great compressibility (as much as the strain of 80%), and excellent stability (100 cycles) during compression. Furthermore, the sensitive variation of electrical resistance and cycle stability was validated under the compressive strain of 50% which make CGSs great candidates for pressure-responsive sensors, elastic conductors and other applications.
Co-reporter:Ying Guo, Yi-Tao Xu, Bo Zhao, Tao Wang, Kai Zhang, Matthew M. F. Yuen, Xian-Zhu Fu, Rong Sun and Ching-Ping Wong
Journal of Materials Chemistry A 2015 vol. 3(Issue 26) pp:13653-13661
Publication Date(Web):28 Apr 2015
DOI:10.1039/C5TA01891A
Novel urchin-like Pd@CuO–Pd yolk–shell nanostructures are synthesized through subsequent oxidation of Pd@Cu2O truncated octahedron core–shell precursors with a PdCl42− aqueous solution. The permeable hierarchical CuO shells are constructed by a radially standing 1D single-crystalline nanothorn with Pd nanoparticles. The Pd nanocube cores are encapsulated and confined in the void space of the urchin-like shells. The urchin-like yolk–shell Pd@CuO–Pd nanostructures demonstrate excellent electrocatalytic activity and selectivity for glucose oxidation. Enzyme-free glucose biosensors based on the urchin-like yolk–shell Pd@CuO–Pd electrocatalysts display a higher sensitivity (665.9 μA cm−2 mM−1) than those of the CuO nanoparticles (455.8 μA cm−2 mM−1), Cu2O nanoparticles (220.4 μA cm−2 mM−1), Pd@Cu2O truncated octahedra (179.1 μA cm−2 mM−1), Pd mixtures (65.5 μA cm−2 mM−1) and Pd nanocubes (1.42 μA cm−2 mM−1). The outstanding electrocatalytic performance of the urchin-like Pd@CuO–Pd yolk–shell nanostructures might be ascribed to two reasons: the unique hierarchical yolk–shell structures provide highly exposed active sites and act as an individualized nanoreactor to enhance the mass diffusion and transport of reactants at the electrode/electrolyte interface. Moreover, the nanocomposite of metal oxide semiconductor CuO and noble metal Pd would result in a synergetic effect to improve the electrocatalysis.
Co-reporter:Xiaoliang Zeng, Shuhui Yu, Lei Ye, Mingyang Li, Zhilong Pan, Rong Sun and Jianbin Xu
Journal of Materials Chemistry A 2015 vol. 3(Issue 1) pp:187-195
Publication Date(Web):28 Oct 2014
DOI:10.1039/C4TC01051E
Multiwalled carbon nanotubes (MWCNTs) have been widely used as mechanical reinforcement fillers for polymers during the past decades. However, the high electrical conductivity of MWCNTs hampers their applications in some specific fields. In this study, the MWCNT was encapsulated with an insulating silicon oxide (SiO2) layer to form core–shell structure MWCNT@SiO2 nanoparticles, which were used to fill bismaleimide-triazine (BT) resin. The obtained polymer nanocomposites possessed high mechanical strength, electrical insulation, improved thermal stability, and good optical transparency. These excellent properties were attributed to the strong interfacial interaction between MWCNT@SiO2 and the polymer, as well as the suppression of electron transport by the SiO2 layer on the MWCNT surface. The nanocomposites were employed to fabricate a printed circuit substrate, on which a frequency “flasher” circuit and the electrical components worked well. This work has demonstrated the possibility of using MWCNTs as mechanical reinforcement fillers in polymer nanocomposites, which simultaneously possess electrical insulation.
Co-reporter:Songfang Zhao, Yongju Gao, Jinhui Li, Guoping Zhang, Chunyi Zhi, Libo Deng, Rong Sun, and Ching-Ping Wong
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 12) pp:6716
Publication Date(Web):March 6, 2015
DOI:10.1021/acsami.5b00116
Coassemble diverse functional nanomaterials with carbon nanotubes (CNTs) to form three-dimensional (3D) porous CNTs hybrid architectures (CHAs) are potentially desirable for applications in energy storage, flexible conductors, and catalysis, because of diverse functionalities and synergistic effects in the CHAs. Herein, we report a scalable strategy to incorporate various functional nanomaterials with N-doped CNTs (N-CNTs) into such 3D porous CHAs on the polyurethane (PU) sponge skeletons via layer-by-layer (LbL) assembly. To investigate their properties and applications, the specific CHAs based on N-CNTs and Ag nanoparticles (NPs), denoted as PU-(N-CNTs/Ag NPs)n, are developed. The unique binary structure enables these specific CHAs conductors to possess reliable mechanical and electrical performance under various elastic deformations as well as excellent hydrophilicity. Moreover, they are employed as strain-gauge sensor and heterogeneous catalyst, respectively. The sensor could detect continuous signal, static signal, and pulse signal with superior sustainability and reversibility, indicating an important branch of electromechanical devices. Furthermore, the synergistic effects among N-CNTs, Ag NPs, and porous structure endow the CHAs with excellent performance in catalysis. We have a great expectation that LbL assembly can afford a universal route for incorporating diverse functional materials into one structure.Keywords: flexible conductor; heterogeneous catalysis; layer-by-layer assembly; man−machine interaction; strain-gauge sensor
Co-reporter:Hu-Ming Ren, Ying Guo, Sheng-Yun Huang, Kai Zhang, Matthew M.F. Yuen, Xian-Zhu Fu, Shuhui Yu, Rong Sun, and Ching-Ping Wong
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 24) pp:13685
Publication Date(Web):May 29, 2015
DOI:10.1021/acsami.5b03571
A facile one-step solution-phase chemical reduction method has been developed to synthesize Ag microsheets at room temperature. The morphology of Ag sheets is a regular hexagon more than 1 μm in size and about 200 nm in thickness. The hexagonal Ag microsheets possess a smoother and straighter surface compared with that of the commercial Ag micrometer-sized flakes prepared by ball milling for electrically conductive adhesives (ECAs). The function of the reagents and the formation mechanism of Ag hexagonal microsheets are also investigated. For the polyvinylpyrrolidone (PVP) and citrate facet-selective capping, the Ag atoms freshly reduced by N2H4 would orientationally grow alone on the {111} facet of Ag seeds, with the synergistically selective etching of irregular and small Ag particles by H2O2, to form Ag hexagonal microsheets. The hexagonal Ag microsheet-filled epoxy adhesives, as electrically conductive materials, can be easily printed on various substrates such as polyethylene terephthalate (PET), epoxy, glass, and flexible papers. The hexagonal Ag microsheet filled ECAs demonstrate lower bulk resistivity (approximately 8 × 10–5 Ω cm) than that of the traditional Ag micrometer-sized-flake-filled ECAs with the same Ag content of 80 wt % (approximately 1.2 × 10–4 Ω cm).Keywords: Ag hexagonal flake; electrically conductive adhesive; facet selective growth; nanoplate; printed electronic;
Co-reporter:Tao Wang, Ying Guo, Bo Zhao, Shuhui Yu, Hai-Peng Yang, Daniel Lu, Xian-Zhu Fu, Rong Sun, Ching-Ping Wong
Journal of Power Sources 2015 Volume 286() pp:371-379
Publication Date(Web):15 July 2015
DOI:10.1016/j.jpowsour.2015.03.180
•3D hierarchical porous Ni films are fabricated as effective current collectors.•NiCo2O4 nanosheets are in-situ grown on the 3D hierarchical porous Ni films.•The porous NiCo2O4/Ni electrodes demonstrate excellent capacitive performance.Three dimensional interconnected hierarchical porous Ni films are easily fabricated as effective current collectors through hydrogen bubble template electrochemical deposition. The binder-free integrated electrodes of spinel NiCo2O4 nanosheets directly coated the three dimensional porous Ni films are facilely obtained through successively electrochemical co-deposition of Ni/Co alloy layer then followed by subsequent annealing at 350 °C in air. Compared with NiCo2O4 nanosheets on smooth Ni foil or porous NiO/Ni film electrodes, the porous NiCo2O4/Ni integrated film electrodes for supercapacitors demonstrate remarkably higher area specific capacitance. The porous NiCo2O4/Ni film electrodes also exhibit excellent rate capability and cycling stability. The super electrochemical capacitive performances are attributed to the unique integrated architecture of NiCo2O4 nanosheets in-situ grown on three dimensional continuous hierarchical porous Ni collector collectors, which could provide large electrode-electrolyte interface area, high active sites, low contact resistance between current collector and active materials, fast electron conduction and ion/electrolyte diffusion.
Co-reporter:Songfang Zhao, Yongju Gao, Guoping Zhang, Libo Deng, Jinhui Li, Rong Sun, Ching-Ping Wong
Carbon 2015 Volume 86() pp:225-234
Publication Date(Web):May 2015
DOI:10.1016/j.carbon.2015.01.033
Flexible strain-gauge sensors are an essential component in electronic devices, and pressure sensing is also an important function. Here, we report an ultrastable and highly sensitive sensor based on covalently bonded nitrogen-doped carbon-nanotube-supported Ag (N-CNT/Ag) hybrid sponges with hierarchical binary-network architectures via a unidirectional freezing technique. The covalent bonding utilizing hyperbranched polyglycerol (HPG) as bridges endows the sponges with structural stability under compression, oscillation, and bending modes. Moreover, a large number of Ag nanoparticles (NPs) decorated using HPG as templates could also enable the N-CNTs/Ag sponges to possess linear current–voltage behavior. Furthermore, the Ag NPs on the compartmental films can be considered as interlocked nanodomes, which not only enhance compression stress but also generate huge variation of resistance through variation of contact area under mechanical deformation. These novel designs featuring interlocked geometry and covalent bonding allow the hybrid sponges to act as strain-gauge sensors with high gauge factor (1.4) and excellent stability.
Co-reporter:Bo Zhao, Sheng-Yun Huang, Tao Wang, Kai Zhang, Matthew M.F. Yuen, Jian-Bin Xu, Xian-Zhu Fu, Rong Sun, Ching-Ping Wong
Journal of Power Sources 2015 Volume 298() pp:83-91
Publication Date(Web):1 December 2015
DOI:10.1016/j.jpowsour.2015.08.043
•3D graphene foams encapsulated hollow SnO2@Co3O4 spheres was synthesized.•Core-shell hollow SnO2@Co3O4 spheres with mesoporous shells and high surface area.•3D graphene foams provided highly conductive networks and flexible buffering matrix.•The 3D architecture showed excellent performance for supercapacitors and LIBs.Hollow SnO2@Co3O4 spheres are fabricated using 300 nm spherical SiO2 particles as template. Then three-dimensional graphene foams encapsulated hollow SnO2@Co3O4 spheres are successfully obtained through self-assembly in hydrothermal process from graphene oxide nanosheets and metal oxide hollow spheres. The three-dimensional graphene foams encapsulated architectures could greatly improve the capacity, cycling stability and rate capability of hollow SnO2@Co3O4 spheres electrodes due to the highly conductive networks and flexible buffering matrix. The three-dimensional graphene foams encapsulated hollow SnO2@Co3O4 spheres are promising electrode materials for supercapacitors and lithium-ion batteries.Hollow SnO2@Co3O4 spheres encapsulated in three-dimensional graphene foams demonstrate excellent electrochemical performance for supercapacitors and lithium-ion batteries.
Co-reporter:Yi-Tao Xu, Ying Guo, Le-Xin Song, Kai Zhang, Matthew M.F. Yuen, Jian-Bin Xu, Xian-Zhu Fu, Rong Sun, Ching-Ping Wong
Electrochimica Acta 2015 Volume 176() pp:434-441
Publication Date(Web):10 September 2015
DOI:10.1016/j.electacta.2015.06.093
Cuprous oxide (Cu2O) sub-microspheres @ reduced graphene oxide (rGO) nanosheets core-shell composites with 3D architecture are successfully fabricated by a one-step method through co-reduction of irregular cupric citrate and graphene oxide nanosheets at room temperature. Comparing to the bare Cu2O sub-microspheres and the simple physical mixture of Cu2O and rGO (Cu2O-rGO-M), the Cu2O@rGO electrodes demonstrate dramatically improved capacity, cyclic stability and rate capability as anode materials for lithium ion batteries. At a low current density of 100 mA∙g−1, Cu2O@rGO electrodes deliver a discharge capacity of 534 mAh∙g−1 after 50 cycles, retaining 94% of the initial capacity. Under a higher current density of 1000 mA∙g−1, Cu2O@rGO electrodes exhibit a discharge capacity of 181 mAh∙g−1 after 200 cycles, approximately 4 times larger than that of bare Cu2O sub-microsphere electrodes. The rate capacity retention of Cu2O@rGO electrode is 74% at 200 mA∙g−1 and 38% at 1000 mA∙g−1 relative to 100 mA∙g−1, much better than that for Cu2O-rGO-M (52% and 34%) and bare Cu2O electrodes (13% and 3%,). The enhanced electrochemical performance for Cu2O@rGO might be ascribed to the rGO coating and 3D architecture. The outer coated rGO nanosheets could provide additional 3D conductive networks as well as serve as the buffer layers for accommodating the large volume change of the inner Cu2O sub-microspheres during the charge-discharge cycling.
Co-reporter:Hong Jiang, Yi-Tao Xu, Tao Wang, Peng-Li Zhu, Shuhui Yu, Yan Yu, Xian-Zhu Fu, Rong Sun, Ching-Ping Wong
Electrochimica Acta 2015 Volume 166() pp:157-162
Publication Date(Web):1 June 2015
DOI:10.1016/j.electacta.2015.03.089
•Flower-like NiHCF nanosheets are directly grown on the 3D conductive metal nanostructure substrate for neutral electrolyte supercapacitors.•The 3D hierarchical porous NiHCF/Ni film electrodes exhibit about 10-times larger specific capacitance than the smooth NiHCF/Ni film in KNO3 neutral electrolyte.•The improved electrochemical performance could be ascribed to the porous structure of the 3D NiHCF/Ni composites as well as the direct interconnection between the 3D hierarchical current collector and the flower-like NiHCF nanosheets.Nickel hexacyanoferrate (NiHCF) flower-like nanosheets coated three dimensional (3D) hierarchical porous Ni composite films are successfully prepared by the combination of hydrogen-bubble template electro-deposition and electrochemical polymerization methods. The novel 3D porous NiHCF/Ni composite films demonstrate excellent electrochemical performance as binder-free integrated electrodes for supercapacitors in KNO3 neutral electrolyte. Comparing to the NiHCF coated on smooth Ni film, the 3D hierarchical porous NiHCF/Ni film electrodes exhibit about 10 times larger specific capacitance in KNO3 neutral electrolyte. The 3D porous NiHCF/Ni film electrodes also illustrate good long-term stability for about 18,000 charge-discharge cycles. The improvement of electrochemical performance might be ascribed to the large specific area, highly conductive pathway and fast ion diffusion for the flower-like NiHCF nanosheets directly growth on the 3D hierarchical porous interconnected conductive scaffold current collectors.
Co-reporter:Xiaoliang Zeng, Lei Ye, Rong Sun, Jianbin Xu and Ching-Ping Wong
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 26) pp:16709-16714
Publication Date(Web):29 May 2015
DOI:10.1039/C5CP02192H
The viscoelasticity of boron nitride nanosheet (BNNS) aerogel has been observed and investigated. It is found that the BNNS aerogel has a high damping ratio (0.2), while it exhibits lightweight and negligible temperature dependence below 180 °C. The creep behavior of the BNNS aerogel markedly demonstrates its strain dependence on stress magnitude and temperature, and can be well simulated by the classical models.
Co-reporter:Ying Guo, Ling Zhang, Bo Zhao, Kai Zhang, Matthew M. F. Yuen, Jian-Bin Xu, Xian-Zhu Fu, Rong Sun and Ching-Ping Wong
RSC Advances 2015 vol. 5(Issue 107) pp:87987-87992
Publication Date(Web):12 Oct 2015
DOI:10.1039/C5RA14050A
Graphene oxide (GO) could be efficiently reduced to graphene on a Cu electrode through a novel electrocatalytic solid-to-solid reaction. Compared to glass carbon (GC) inertial electrodes, more oxygen-containing groups are removed on copper electrodes under the same electrochemical reduction conditions for de-oxygenation of GO nanosheets. Especially, Cu catalyst could electrochemically catalyze the elimination of sp3 carbon clusters in GO to restore sp2 CC conjugated network of graphene relative to GC electrode.
Co-reporter:Songfang Zhao, Yongju Gao, Jinhui Li, Guoping Zhang, Rong Sun and Ching-Ping Wong
RSC Advances 2015 vol. 5(Issue 70) pp:56974-56981
Publication Date(Web):23 Jun 2015
DOI:10.1039/C5RA08963H
A novel protocol to prepare multifunctional magnetic organic–inorganic nanostructured catalysts of Fe3O4@organosilicon/Ag with tailored properties is developed. Such nanostructure design endows the catalysts with superparamagnetism (11.6 emu g−1), excellent oxidation resistance, and catalytic activity. Fe3O4 nanoparticles (NPs) are encapsulated with porous organosilicon via improved self-assembly of a flexible-bridged organosilicon precursor without templates. Subsequently, dispersed Ag NPs are in situ grown on the porous microparticles via a silver mirror reaction. The as-prepared multifunctional catalysts are characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, a vibration sample magnetometer, X-ray diffraction, thermal gravimetric analysis, and nitrogen adsorption and desorption, respectively. The resultant hybrid microparticles possess micro- and nano-pores, and exhibit a small hysteresis loop and low coercivity. Meaningfully, they exhibit exceptional catalytic performance for the reduction of 4-nitrophenol in the presence of sodium borohydride and could be reused at least 9 times with excellent stability by means of convenient magnetic separation. The catalysts could be employed to reduce other dyes such as methylene blue, orange G and rhodamine B, and their corresponding reductions follow pseudo-first-order reactions. Therefore, the proposed structure design and scalable route for the synthesis of hierarchical catalysts can pave the way for synthesizing other catalyst systems to address the diverse reaction demands.
Co-reporter:Jianwen Xia, Guoping Zhang, Libo Deng, Haipeng Yang, Rong Sun and Ching-Ping Wong
RSC Advances 2015 vol. 5(Issue 25) pp:19315-19320
Publication Date(Web):10 Feb 2015
DOI:10.1039/C5RA00718F
A novel core–shell structure of Al2O3 nanoparticles (NPs) attached on poly(amic acid) (PAA) fiber has been successfully developed by facile coaxial electrospinning technology for the first time. The as-prepared PAA fiber went through imidization to prepare the Al2O3@polyimide (Al2O3@PI) film. The resultant films with different Al2O3 contents are characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, thermal gravimetric analysis, and dynamical mechanical analysis. The results indicated that the Al2O3 NPs could uniformly decorate the surface of fibers with a diameter of about 1 μm, which enhanced the thermal and mechanical properties of the fiber-based films. In particular, the flexible film with a high content of Al2O3 of 59.3 wt% presents a high storage modulus (2.11 GPa) and excellent thermal stability (474 °C at 5% mass loss) as well as superior in plane thermal conductivity of 9.66 W m−1 K−1. Finally, compared with pure PI film, the Al2O3@PI fiber-based film exhibits excellent thermal transfer ability in light emitting diode packaging. Therefore, the novel Al2O3@PI fiber-based film with integrated properties of insulation, thermal conductivity and flexibility can be used for wearable electronics and power devices.
Co-reporter:Hong Jiang, Ying Guo, Tao Wang, Peng-Li Zhu, Shuhui Yu, Yan Yu, Xian-Zhu Fu, Rong Sun and Ching-Ping Wong
RSC Advances 2015 vol. 5(Issue 17) pp:12931-12936
Publication Date(Web):16 Jan 2015
DOI:10.1039/C4RA15092A
Ni(OH)2 coated on Ni porous films are facilely fabricated by anode oxidation of 3D hierarchical porous Ni films which are prepared through a hydrogen bubble template electro-deposition method. The highly porous nickel films function as effective 3D conductive network current collectors and scaffolds to in situ form a thin layer of Ni(OH)2 active material. The electrochemical capacitive performances are investigated by cyclic voltammetry (CV) and the galvanostatic charge–discharge technique in 6 M KOH electrolyte. The 3D porous Ni(OH)2/Ni integrated electrodes demonstrate a much higher specific capacity of 828 mF cm−2 than 126 mF cm−2 for the smooth Ni(OH)2/Ni electrode at a current density of 10 mA cm−2. The 3D porous Ni(OH)2/Ni integrated electrodes also display a good capacity retention of 95% after 1000 cycles. The superior capacitive properties of 3D porous Ni(OH)2/Ni electrodes might result from the thin layer Ni(OH)2 active materials in situ formed on the highly 3D porous Ni metallic current collector with large surface area, low contact resistance between Ni(OH)2 active material and Ni current collector, and fast electron/ion conduction.
Co-reporter:Hui Li, Guoping Zhang, Libo Deng, Rong Sun and Xing Ou-Yang
RSC Advances 2015 vol. 5(Issue 9) pp:6413-6418
Publication Date(Web):16 Dec 2014
DOI:10.1039/C4RA12662A
Thermally responsive copolymer P(NIPAm-co-NMA) was prepared via a radical copolymerization and spun into nanofibers using electrospinning. After thermal crosslinking, the electrospun fibers were modified using KH590 and silver nanoparticles were introduced onto the fiber surface using a chemical plating method. The electrical resistance of the composite fibers containing 65.5% of silver at different temperatures was investigated and it was found that the resistance dropped by ∼60% as the temperature increased from 42 °C to 46 °C, which is consistent with the solubility transition of PNIPAm with the change of temperature as revealed by differential scanning calorimetry (DSC) measurement.
Co-reporter:Suibin Luo, Shuhui Yu, Fang Fang, Maobai Lai, Rong Sun and Ching-Ping Wong
RSC Advances 2015 vol. 5(Issue 5) pp:3377-3380
Publication Date(Web):04 Dec 2014
DOI:10.1039/C4RA12665C
In this study, the formation mechanism of Ag nanoparticles deposited on Barium Titanate (BT) surface was investigated. The surface oxygen vacancies of BT linked with the hydroxyl oxygen of ethylene glycol and catalyzed the reduction of silver nitrate, leading to promoted deposition of Ag nano particles on the BT surface.
Co-reporter:Jinhui Li;Guoping Zhang;Libo Deng;Kun Jiang;Songfang Zhao;Yongju Gao;Chingping Wong
Journal of Applied Polymer Science 2015 Volume 132( Issue 26) pp:
Publication Date(Web):
DOI:10.1002/app.42167
ABSTRACT
The modified novolac epoxy resins with furan pendant groups were prepared by novolac epoxy resin and furfuryl alcohol and then crosslinked by bifunctional maleimide via Diels–Alder (DA) chemistry to obtain the thermally reversible and self-healing novolac epoxy resins. The as-prepared crosslinked novolac epoxy resins were characterized by FT-IR, NMR, TGA, and DMA. The results indicate that the novel crosslinked novolac epoxy resins present higher storage modulus (2.37 GPa at 30°C) and excellent thermal stability (348°C at 5% mass loss). Furthermore, the thermal reversible and self-healing properties were studied in detail by DSC, SEM, thermal re-solution, and gel–solution–gel transition experiments. All the results reveal that the crosslinked novolac epoxy resins based on DA reaction can be used as smart material for the practical application of electronic packaging and structural materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42167.
Co-reporter:Jian Shi, Xiaolin Wu, Xianzhu Fu, Rong Sun
Thermochimica Acta 2015 Volume 617() pp:90-94
Publication Date(Web):10 October 2015
DOI:10.1016/j.tca.2015.08.022
•A novel self-assembly method was introduced to synthesize composite nanoPCMs.•The ratio of TEOS/MMA affects the thermal stability of nanoPCMs.A novel composite PCMs nanocapsules (nanoPCMs) with PMMA and SiO2 as hybrid shell material and paraffin as core were successfully synthesized by concerted reaction of interfacial polymerization, sol–gel and self-assembly methods. SEM images showed that the structure of nanocapsules was affected by the mass ratio of TEOS and MMA. When the mass ratios of TEOS/MMA were 1:3.5 and 1:5.75, the nanocapsules were spherical and homogeneous with the diameter around 120 nm. However, the nanocapsules were inhomogeneous and irregular when the mass ratio of TEOS/MMA was 1:12.5. Based on the results of DSC, moderate mass ratio of TEOS/MMA can improve thermal properties of nanocapsules. When the mass ratio of TEOS/MMA was 1:3.5, the thermal properties of paraffin@PMMA–SiO2 nanocapsules was improved with the average enthalpy about 71 J/g and encapsulated efficiency of paraffin was 57.4%, which was higher than paraffin@PMMA nanocapsules. Besides paraffin which was encapsulated in nanocapsules has a better thermal stability than that of unencapsulated, and the nanocapsules prepared with different mass ratio of MMA/TEOS can provide almost the same thermal stability.
Co-reporter:Xiaoliang Zeng, Shuhui Yu, Rong Sun, Jian-bin Xu
Composites Part A: Applied Science and Manufacturing 2015 Volume 73() pp:260-268
Publication Date(Web):June 2015
DOI:10.1016/j.compositesa.2015.03.015
Carbon nanotubes (CNTs) have been widely used as mechanical reinforcement agents of composites. However, their aggregations, weak interfacial interaction with polymer, as well as high electrical conductivity limit their use in some especial applications. In this paper, the silicon oxide (SiO2)-coated (CNT@SiO2) core–shell hybrids with different SiO2 thickness were prepared and employed to reinforce glass fibre-reinforced bismaleimide–triazine (BT) resin (GFRBT) composites. The results indicated the mechanical properties, including tensile strength and Young’s modulus increased with the increase of SiO2 thickness and CNT@SiO2 loading. Such enhanced mechanical properties were mainly attributed to the intrinsically nature of CNTs, homogeneous dispersion of the hybrids, as well as improved interfacial interaction. Meanwhile, the composites remained high electrical insulation (9.63 × 1012 Ω cm) due to the existence of SiO2 layer on CNT surface. This study will guide the design of functionalized CNTs and the construction of high-performance composites.
Co-reporter:Yimin Yao, Xiaoliang Zeng, Kun Guo, Rong Sun, Jian-bin Xu
Composites Part A: Applied Science and Manufacturing 2015 Volume 69() pp:49-55
Publication Date(Web):February 2015
DOI:10.1016/j.compositesa.2014.10.027
Rapidly increasing packaging density of electronic devices puts forward higher requirements for thermal conductivity of glass fibers reinforced polymer (GFRP) composites, which are commonly used as substrates in printed circuit board. Interface between fillers and polymer matrix has long been playing an important role in affecting thermal conductivity. In this paper, the effect of interfacial state on the thermal conductivity of functionalized Al2O3 filled GFRP composites was evaluated. The results indicated that amino groups-Al2O3 was demonstrated to be effective filler to fabricate thermally conductive GFPR composite (1.07 W/m K), compared with epoxy group and graphene oxide functionalized Al2O3. It was determined that the strong adhesion at the interface and homogeneous dispersion of filler particles were the key factors. Moreover, the effect of interfacial state on dielectric and thermomechanical properties of GFRP composites was also discussed. This research provides an efficient way to develop high-performance GFRP composites with high thermal conductivity for integrated circuit packaging applications.
Co-reporter:Yi-Tao Xu, Ying Guo, Chang Li, Xuan-Yu Zhou, Michael C. Tucker, Xian-Zhu Fu, Rong Sun, Ching-Ping Wong
Nano Energy 2015 Volume 11() pp:38-47
Publication Date(Web):January 2015
DOI:10.1016/j.nanoen.2014.10.011
Cu2O microspheres were successfully encapsulated by graphene oxide (GO) nano-sheets and used directly as the anode material for lithium ion batteries. The core–shell structured Cu2O@GO composite delivered a reversible capacity of 458 mA h g−1 at a current density of 100 mA g−1 after 50 cycles. Even at a high charge–discharge rate of 1000 mA g−1, Cu2O@GO still demonstrated a reversible capacity of 240 mA h g−1 after 200 cycles, significantly higher than those of the bare Cu2O microspheres (37 mA h g−1) and GO nano-sheets (11 mA h g−1). The rate capability evaluated by the ratio of capacity at 100 mA g−1/1000 mA g−1 current density was 49%, 25% and 9.8% for Cu2O@GO, bare Cu2O and GO, respectively. The greatly enhanced performance for GO nano-sheets wrapped Cu2O microspheres composite mainly resulted from the synergistic effect of Cu2O microspheres and GO nano-sheets core–shell composite: the flexible in-situ electrochemically reduced GO nano-sheet coating layer functioning as an efficient three dimensional (3D) conductive network and lithium storage active material; the Cu2O microsphere core functioning as a skeleton to support multilayer GO sheets and avoid GO nano-sheets aggregation.
Co-reporter:Yongju Gao;Songfang Zhao;Guoping Zhang;Libo Deng
Journal of Materials Science 2015 Volume 50( Issue 9) pp:3399-3408
Publication Date(Web):2015 May
DOI:10.1007/s10853-015-8898-z
Hierarchically porous organosilica microspheres have been facilely synthesized by improved self-assembly of flexible-bridged organosilica precursor without templates and harsh conditions. Subsequently, monodispersed silver nanoparticles (Ag NPs) are in situ grown on the porous microspheres via silver mirror reaction.
The as-prepared hybrid composites of Ag supported on porous microspheres are characterized by scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy, X-ray diffraction, thermal gravimetric analysis and nitrogen adsorption and desorption, respectively. These results indicate that not only Ag NPs (20–40 nm) are grown on the organosilica uniformly but also the content of Ag NPs immobilized in the hybrid materials can be well controlled by simply tuning the amount of the Ag(NH3)2OH. The resultant hybrid microspheres exhibit remarkable and durable performances for the reduction of 4-nitrophenol to 4-aminophenol by NaBH4 in aqueous solution. Moreover, the catalytic kinetic mode can be tuned by adjusting the parameter in catalytic reaction, and it can be recycled for seven successive cycles with excellent conversion of 100 % within 8 min. Therefore, the present structure design and scalable route for the synthesis of hierarchical catalyst can provide a highly efficient solution for the reduction of nitro-aromatic compounds in the view of environmentally friendly strategy.
Co-reporter:Jinhui Li, Guoping Zhang, Libo Deng, Songfang Zhao, Yongju Gao, Kun Jiang, Rong Sun and Chingping Wong
Journal of Materials Chemistry A 2014 vol. 2(Issue 48) pp:20642-20649
Publication Date(Web):17 Oct 2014
DOI:10.1039/C4TA04941A
Covalently bonded graphene oxide/polyurethane (GO/PU) composites with significant reinforcement and thermally healable properties were developed via in situ polymerization based on Diels–Alder (DA) chemistry. The PU prepolymer was prepared with GO, 4,4-diphenylmethane diisocyanate, and poly(tetramethylene glycol) and blocked by using furfuryl alcohol firstly. Then the prepolymer was cross-linked by using bifunctional maleimide via DA chemistry. SEM shows that the GO was dispersed uniformly in the PU matrix. The DA and retro-DA reactions were characterized by Fourier transform infrared spectroscopy and differential scanning calorimetry separately. Tensile tests showed that with the incorporation of 0.1 wt% of GO, the tensile modulus of GO/PU composites increased from 9.80 MPa to 21.95 MPa, and the tensile strength and elongation at break of the GO/PU composites increased by more than 367% and 210%, respectively. Furthermore, the composites had thermally healable ability which was inspected by using an atomic force microscope and the strain–stress test. The healing efficiency of 78% on average was achieved which was determined by the recovery of breaking stress and a healing mechanism was tentatively proposed. Therefore, the covalently bonded self-healing GO/PU composites could be used as smart materials and structural materials.
Co-reporter:Yu Zhang, Pengli Zhu, Liang Chen, Gang Li, Fengrui Zhou, Daoqiang (Daniel) Lu, Rong Sun, Feng Zhou and Ching-ping Wong
Journal of Materials Chemistry A 2014 vol. 2(Issue 30) pp:11966-11973
Publication Date(Web):24 Jun 2014
DOI:10.1039/C4TA01920B
Novel hierarchical architectures of porous copper (Cu) microspheres assembled with nanoparticles have been successfully synthesized by ingeniously selecting the precursor and complexant through a facile wet chemical reduction method. The resultant porous Cu microspheres have a size distribution of 700 ± 50 nm and have excellent monodispersity. The synergistic effect between the precursor of slightly soluble copper hydroxide and the complexants of polyacrylic acid and ethanol amine exactly induces the generation of unique porous hierarchical architectures. The obtained porous Cu microspheres were applied to reduce and degrade different organic dyes with high concentrations (4-nitrophenol, methylene blue, and rhodamine B) in the presence of NaBH4. Compared with solid Cu particles that have the same size, these porous Cu microspheres exhibit more excellent catalytic activity due to their hierarchical structures. Moreover, the catalyst with universal applicability could be easily separated from the catalytic system and sustainedly possess high stability in recycled reactions.
Co-reporter:Suibin Luo, Shuhui Yu, Rong Sun, and Ching-Ping Wong
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 1) pp:176
Publication Date(Web):December 9, 2013
DOI:10.1021/am404556c
Nano Ag-deposited BaTiO3 (BT-Ag) hybrid particles usable as fillers for flexible polymeric composites to obtain high dielectric constant, low conductivity, and low dielectric loss were developed. BT-Ag hybrid particles were synthesized via a seed-mediated growing process by a redox reaction between silver nitrate and ethylene glycol. Nano Ag particles with a size less than 20 nm were discretely grown on the surface of the 100 nm BaTiO3. The similar lattice spacing of the (1 1 1) planes of BT and Ag led to the hetero-epitaxial growth of Ag on the BT surface. The thickness of the coherent interface was about 3 nm. The adhesion of Ag to BT efficiently prevented the continuous contact between Ag particles in the polyvinylidene fluoride (PVDF) matrix and suppressed the formation of the conducting path in the composite. As a result, with a filler loading of 43.4 vol %, the composite exhibited a dielectric constant (Dk) value of 94.3 and dielectric loss (tan δ) of 0.06 at 1 kHz. An even higher Dk value of 160 at 1 kHz (16 times larger than that of PVDF) was obtained when the content of BT-Ag was further increased, with low conductivity (σ < 10–5 S m–1) and low dielectric loss (tan δ = 0.11), demonstrating promising applications in the electronic devices.Keywords: Ag-deposited BaTiO3; dielectric composites; hetero-epitaxial interface; polymer matrix;
Co-reporter:Yu Zhang, Pengli Zhu, Gang Li, Tao Zhao, Xianzhu Fu, Rong Sun, Feng Zhou, and Ching-ping Wong
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 1) pp:560
Publication Date(Web):December 13, 2013
DOI:10.1021/am404620y
Monodisperse copper nanoparticles with high purity and antioxidation properties are synthesized quickly (only 5 min) on a large scale (multigram amounts) by a modified polyol process using slightly soluble Cu(OH)2 as the precursor, l-ascorbic acid as the reductant, and PEG-2000 as the protectant. The resulting copper nanoparticles have a size distribution of 135 ± 30 nm and do not suffer significant oxidation even after being stored for 30 days under ambient conditions. The copper nanoparticles can be well-dispersed in an oil-based ink, which can be silk-screen printed onto flexible substrates and then converted into conductive patterns after heat treatment. An optimal electrical resistivity of 15.8 μΩ cm is achieved, which is only 10 times larger than that of bulk copper. The synthesized copper nanoparticles could be considered as a cheap and effective material for printed electronics.Keywords: antioxidative; copper nanoparticles; flexible conductors; large scale; monodisperse;
Co-reporter:Songfang Zhao, Guoping Zhang, Yongju Gao, Libo Deng, Jinhui Li, Rong Sun, and Ching-Ping Wong
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 24) pp:22823
Publication Date(Web):November 25, 2014
DOI:10.1021/am5069936
Flexible strain-driven sensor is an essential component in the flexible electronics. Especially, high durability and sensitivity to strain are required. Here, we present an efficient and low-cost fabrication strategy to construct a highly sensitive and flexible pressure sensor based on a conductive, elastic aerogel with pyramid design. When pressure is loaded, the contact area between the interfaces of the conductive aerogel and the copper electrode as well as among the building blocks of the nitrogen-doped carbon-nanotube-supported Ag (N-CNTs/Ag) aerogel monoliths, changes in reversible and directional manners. This contact resistance mechanism enables the hybrid aerogels to act as strain-driven sensors with high sensitivity and excellent on/off swithching behavior, and the gauge factor (GF) is ∼15 under strain of 3%, which is superior to those reported for other aerogels. In addition, robust, elastomeric and conductive nanocomposites can be fabricated by injecting polydimethylsiloxane (PDMS) into alginate/N-CNTs/Ag aerogels. Importantly, the building blocks forming the aerogels retain their initial contact and percolation after undergoing large-strain deformation, PDMS infiltration, and cross-linking of PDMS, suggesting their potential applications as strain sensors.Keywords: conductive hybrid aerogel; contact resistance; flexible; pyramid design; strain-driven
Co-reporter:Pengli Zhu, Qi Zheng, Rong Sun, Wenjie Zhang, Jihua Gao, Chingping Wong
Journal of Alloys and Compounds 2014 Volume 614() pp:289-296
Publication Date(Web):25 November 2014
DOI:10.1016/j.jallcom.2014.06.065
•BT coated by NZFO (BNCP) has been successfully prepared.•The outer BT phase could inhibit the grain growth of NZFO in the composites.•This structure is help to get the uniform ferromagnetic-ferroelectric composites.•BNCP composites with NZFO:BT (1.5:1) shows the best comprehensive performance.In this paper, we report the preparation of BaTiO3(BT)/Ni0.5Zn0.5Fe2O4(NZFO) ceramics which own the microstructure of BT coated by NZFO through the co-precipitation procedure (BNCP). X-ray diffraction measurements are used to demonstrate the phase change with different molar ratio of NZFO:BT, and their dielectric and magnetic properties of the composite has been investigated by a RF Impedance/Material Analyzer and M–H loop measurement. The results indicate that the BNCP composite ceramics with NZFO:BT molar ratio at 1.5:1 owns the largest Q (the quality factor) and product of μi × Q and shows nice comprehensive performance in multiferroic field. In addition, this inner BT phase endow the ceramic composites higher cut-off frequency fr and broaden the frequency scope of the composites with higher permeability which could greatly benefit its application.
Co-reporter:Yi-Tao Xu, Ying Guo, Le-Xing Song, Kai Zhang, Matthew M. F. Yuen, Xian-Zhu Fu, Rong Sun and Ching-Ping Wong
RSC Advances 2014 vol. 4(Issue 101) pp:58005-58010
Publication Date(Web):30 Oct 2014
DOI:10.1039/C4RA08608B
Reduced graphene oxide nano-sheets encapsulated copper spherical particles (Cu@rGO) were obtained through a simple electrostatic self-assembly process followed by chemical reduction. The oxidation resistance of Cu spherical particles was considerably enhanced by the coating of rGO nano-sheets. XRD results show that the core–shell structured Cu@rGO did not exhibit any sign of oxidation in air after storage at room temperature for 70 days or after heat treatment at 130 °C for 1.5 h. Furthermore, the rGO wrapped on the surface of Cu particles could transfer the two-dimensional rGO nano-sheets into three-dimensional (3D) networks. The Cu@rGO particles with 3D structure might have promising potential applications in thermal management, electrically conductive interconnection, electrodes, etc.
Co-reporter:Xianwen Liang, Tao Zhao, Yougen Hu, Pengli Zhu, Rong Sun, Dao qiang (Daniel) Lu and Chingping Wong
RSC Advances 2014 vol. 4(Issue 88) pp:47536-47539
Publication Date(Web):30 Sep 2014
DOI:10.1039/C4RA09317H
High-purity silver nanowires (AgNWs) with an average width of 60 ± 5 nm and a typical length of 10–20 μm were synthesized conveniently at a relatively high AgNO3 concentration of 0.3 M through a CuCl2 and stainless steel co-mediated polyol reduction method.
Co-reporter:Sheng-Yun Huang, Kai Zhang, Matthew M. F. Yuen, Xian-Zhu Fu, Rong Sun and Ching-Ping Wong
RSC Advances 2014 vol. 4(Issue 64) pp:34156-34160
Publication Date(Web):25 Jul 2014
DOI:10.1039/C4RA05176A
Free-standing and flexible graphene–silver (GE–Ag) composite paper has been successfully fabricated through an evaporation of graphene oxide–AgNO3 aqueous aerosol followed by a chemical reduction. The size, thickness and shape of the GE–Ag paper can be tuned according to the Teflon substrate used. The GE–Ag paper presents the advantages of good flexibility, high electrical conductivity (159 Ω per sq) and good thermal conductivity in the vertical direction (3.3 W mK−1), which are more optimal than the pure GE paper.
Co-reporter:Ying Liu, Yu Wang, Liping Wang, Ying-Ying Gu, Shu-Hui Yu, Zhou-Guang Lu and Rong Sun
RSC Advances 2014 vol. 4(Issue 9) pp:4754-4762
Publication Date(Web):03 Dec 2013
DOI:10.1039/C3RA46224B
A series of Eu3+-doped double tungstate and molybdate red phosphors, LiLn(MO4)2:Eu3+ (Ln = La, Eu, Gd, Y; M = W, Mo), have been successfully synthesized by a simple Pechini method. The procedure involves formation of homogeneous, and transparent, metal–citrate gel precursors using citric acid as a chelating ligand to form metal complexes and ethylene glycol as a cross-linker for polyesterification with the complexes, followed by calcination to promote thermal decomposition of the gel precursors to yield the final LiLn(MO4)2 nanoparticles. The as-synthesized nanoparticles were characterized by thermogravimetric/differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) as well as kinetic decay. The results indicate that the obtained LiLn(MO4)2:Eu3+ samples crystallize in the isostructure with tetragonal space group I41/a (no. 88). A room temperature PL spectrum shows that Eu3+-doped LiLn(MO4)2 powders exhibit an excellent luminescent properties under a near ultraviolet excitation wavelength of 395 nm, suitable for near UV type LEDs. By comparing with other counterparts, it is found that LiEu(WO4)2 and LiEu(MoO4)2 display the highest emission intensity. In addition, the phosphor of composition LiY0.95Eu0.05(WO4)2 shows promising application for white light emission with a decay time of 0.585 ms.
Co-reporter:Maobai Lai, Shuhui Yu, Rong Sun
Materials Letters 2014 Volume 122() pp:45-48
Publication Date(Web):1 May 2014
DOI:10.1016/j.matlet.2014.01.167
•Polyether polyols were employed to enhance the molecular polarity of epoxy resin.•PEG brought more polar oxygen atoms and produced more ester groups in cured epoxy resin.•The permittivity of matrix was effectively enhanced by 23%.•For BT/ER composites, enhancement of the permittivity was even more prominent.•The dielectric loss of matrix and composites was nearly unchanged.Bariumtitanate/epoxy resin (BT/ER) composite with high permittivity was obtained through graft modification on the ER matrix. Polyether polyols were employed to enhance the molecular polarity, which brought more polar oxygen atoms and produced more ester groups in the cured epoxy resin. The permittivity of epoxy matrix film was effectively enhanced (increased from 3.91 to 4.82 at 103 Hz) while the dielectric loss was nearly unchanged. The permittivity of the composite films containing the same amount of BT fillers improved from 18.91 to 28.73. Meanwhile, the increment of dielectric loss was not obvious. Both of the modified matrix and composite films showed excellent thermal stability.
Co-reporter:Maobai Lai, Siwang Kou, Shuhui Yu, Rong Sun, Ching-Ping Wong
Chemical Physics Letters 2014 Volume 612() pp:280-284
Publication Date(Web):18 September 2014
DOI:10.1016/j.cplett.2014.08.042
Highlights
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Graphite oxide was introduced to obtain GO/PI composites with a colossal permittivity.
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At 1 kHz, the permittivity of the composite with 3 wt% GO loading was up to 7179.
- •
During the oxidation process of GO, functional groups were grafted with the carbon framework.
- •
PI was further grafted to GO, inducing the formation of a large conjugation of GO/PI.
- •
The conjugation provided approach for electrons transportation, enhancing the polarizability and permittivity.
Co-reporter:Chongnan Peng, Guoping Zhang, Xiaozhong Gong, Rong Sun
Materials Science in Semiconductor Processing 2014 Volume 18() pp:46-51
Publication Date(Web):February 2014
DOI:10.1016/j.mssp.2013.08.017
Rod-like and hierarchical ZnO nanomaterials were fabricated via a single-step refluxing route in water–methanol mixed solution without any surfactant or template at low temperature. The as-prepared ZnO nanomaterials were characterized by scanning electronic microscopy, X-ray diffractometry and thermogravimetric analysis. By adjusting reaction temperature, precursor concentration and reaction time, ZnO nanomaterials with different morphologies were synthesized. By keeping the reaction temperature above 90 °C, wurtzite ZnO has been grown. With increasing concentration of Zn2+ ions from 0.03 M, 0.06 M to 0.09 M, the morphology of ZnO changes from long rod to short rod and finally hierarchical structures. The specific surface area of hierarchical ZnO was also investigated, and the results show that the hierarchical ZnO has a larger specific surface area (47.75 m² g−1) than that previous reported.
Co-reporter:Li-Fei Lai, Xing-Song Su, Xian-Zhu Fu, Rong Sun, Ching-Ping Wong
Surface and Coatings Technology 2014 Volume 259(Part C) pp:759-766
Publication Date(Web):25 November 2014
DOI:10.1016/j.surfcoat.2014.09.039
•C/W co-doped NiCr thin film improved the electrical properties.•C/W co-doped NiCr thin film exhibited high corrosion resistance.•C and W co-doped NiCr thin film was a promising embedded resistor material.C and W co-doped NiCr alloy flexible thin films were prepared using closed magnetic field unbalanced magnetron sputtering method on a copper foil substrate. The microstructure, electrical properties, and corrosion resistance of the co-doped NiCr thin film were investigated and analyzed as embedded resistor materials. After co-doping, the alloy thin film embedded resistor materials exhibited considerably lower temperature coefficient of resistance (TCR), larger sheet resistance and higher corrosion resistance comparing to the NiCr alloy thin film embedded resistor materials.
Co-reporter:Songling Li;Pengli Zhu;Tao Zhao
Journal of Sol-Gel Science and Technology 2014 Volume 70( Issue 3) pp:366-370
Publication Date(Web):2014 June
DOI:10.1007/s10971-014-3291-y
Antimony doped tin dioxide (ATO) nanoparticles with different Sb doping contents were prepared by freeze-drying the precursor gel and then calcined procedure. The obtained ATO nanoparticles were characterized by X-ray diffraction, scanning electron microscope, optical and electrical techniques. Results indicated that ATO with 10 mol% Sb doping is optimal, with which had the lowest resistivity and highest transmittance in visible region as well as narrow particle size distribution. Thermal insulation properties of ATO/waterborne polyurethane (WPU) films coating on the glass substrates with different thickness were studied on a DIY heat insulating measurement box and showed that the glass coated with ATO/WPU films possessed better heat-insulating effect than empty glass
.
Co-reporter:Libo Deng ; Robert J. Young ; Rong Sun ; Guoping Zhang ; Daoqiang Daniel Lu ; Hui Li ;Stephen J. Eichhorn
The Journal of Physical Chemistry C 2014 Volume 118(Issue 41) pp:24025-24033
Publication Date(Web):September 16, 2014
DOI:10.1021/jp504176b
Single-walled carbon nanotubes (SWNTs) have been exfoliated in a poly(vinyl alcohol) (PVA) matrix using electrospinning. Raman features of SWNTs with single chirality were studied systematically in terms of the band frequency, intensity, and full width at half-maximum (fwhm). Polarized Raman spectroscopy was used to investigate the orientation of SWNTs, and it was found they were highly aligned along the fiber axis. The response of the nanotube G′-band to external strain for SWNT has been found to be dependent on the nanotube chirality, which suggests nonuniform efficiency of mechanical reinforcement for different nanotube species. The preparation and characterization methods demonstrated in this study have led to a better understanding of the effects of aggregation state, chirality, and external strain on the properties of nanotubes that are incorporated in a polymer matrix.
Co-reporter:Libo Deng, Anna E. Lewandowska, Robert J. Young, Guoping Zhang, Rong Sun, Stephen J. Eichhorn
Reactive and Functional Polymers 2014 Volume 85() pp:235-238
Publication Date(Web):December 2014
DOI:10.1016/j.reactfunctpolym.2014.09.001
Electrospun cellulose nanofibres have been graphitized in the presence of silica (SiO2) nanoparticles. The structure of the resultant SiC/C hybrids was characterised using transmission electron microscopy, X-ray diffraction and Raman spectroscopy. Bamboo-like silicon carbide (SiC) nanostructures were observed emanating from the nanofibres treated at 1500 °C which were thought to grow through a vapour–liquid–solid process. The formation of SiC was also thought to lead to a higher degree of graphitization for the electrospun cellulose fibres. These porous and graphitized nanofibres might find applications in electrochemical energy storage.
Co-reporter:Ruiqiang Chen;Dr. Pengli Zhu;Libo Deng;Tao Zhao; Rong Sun; Chingping Wong
ChemPlusChem 2014 Volume 79( Issue 5) pp:743-750
Publication Date(Web):
DOI:10.1002/cplu.201300398
Abstract
Aluminum-doped zinc oxide (AZO) nanorods were successfully prepared by a convenient solvothermal route. The crystal structure and morphology of AZO were characterized by XRD, SEM, and high-resolution TEM. The length and diameter of AZO nanorods decreased with increasing Al content. The optical and electrical properties of AZO were studied by UV/Vis spectroscopy and a four-point probe. The optical band gap of AZO increased initially because of the Burstein–Moss effect and then decreased as the Al content increased owing to the defects of AZO. The electrical resistivity of AZO nanorods varied conversely because of the change of electron and defect concentration (native and impurity defects). The native defect types, which were singly charged zinc and oxygen vacancies, were confirmed by photoluminescence spectroscopy. Moreover, not only the properties but also the growth mechanisms of AZO nanorods were affected by the defect concentrations of singly charged zinc vacancies and substituted Al, which were caused by increasing Al content. Finally, the AZO exhibited the smallest electrical resistivity with 1.5 at. % Al doping content, which was four orders of magnitude smaller than that of ZnO.
Co-reporter:Maobai Lai, Shuhui Yu, Rong Sun, Xiaoliang Zeng, Suibin Luo, Ching-Ping Wong
Composites Science and Technology 2013 Volume 89() pp:127-133
Publication Date(Web):13 December 2013
DOI:10.1016/j.compscitech.2013.09.011
With the development of electronics industry, polymeric dielectric materials with high energy storage density have become increasingly important for the miniaturization of electronic components. In this research work, enhanced permittivity was obtained by graft modification of the epoxy resin matrix. Polyethylene glycol (PEG) and chrome acetylacetonate (Cr Acac) were employed as graft modification reagents. Methyl tetrahydrophthalic anhydride (MeTHPA) was used as curing agent for epoxy resin, which also acted as a precursor for the graft modification reagents. The permittivity of the graft-modified epoxy resin was improved by 30%. With the modified epoxy resin as matrix and nano-sized barium titanate (BaTiO3, BT) as fillers, the dielectric composite film showed a high permittivity of 37.75 and a low tangent loss of 0.022 at the frequency of 1 kHz. In contrast, the composite film without modification showed a much lower permittivity of 24.83. FTIR and UV spectra analysis indicates that graft modification with PEG has induced a number of ester groups, which possess strong dipole polarity. The graft modification with Cr Acac created a new conjugate system with a strong polar center and high inducible polarizability. The two effects led to improved permittivity of the derived epoxy resin and composites. Beside that, it is also likely that a synergistic effect existed between the two modification reagents, which further enhanced the polarity of the cured epoxy resin.
Co-reporter:Ruiqiang Chen;Pengli Zhu;Tao Zhao;Xianzhu Fu;Fengrui Zhou
European Journal of Inorganic Chemistry 2013 Volume 2013( Issue 20) pp:3491-3496
Publication Date(Web):
DOI:10.1002/ejic.201300156
Abstract
Hierarchical nanostructured Al-doped ZnO (AZO) powders were successfully prepared through a mild solution route. The crystal structure and morphology of AZO were determined by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The morphology of the samples changed from random flower-like nanostructures to uniform flower-like hierarchical nanostructures with different Al doping contents. The optical and electrical properties of AZO were studied by UV/Vis spectroscopy and four-point probe. The optical band gap of AZO increased initially but then decreased as the Al content was increased owing to the Burstein–Mass effect and the many-body effect. Conversely, the electrical resistivity of the AZO powders first decreased and then increased with the Al doping content increasing because of changes in the electron and dopant concentrations. AZO exhibited the smallest electrical resistivity with an Al doping content of 1.0 at-%, which is two orders of magnitude smaller than the electrical resistivity of ZnO.
Co-reporter:Lifei Lai, Wenjin Zeng, Xianzhu Fu, Rong Sun, Ruxu Du
Surface and Coatings Technology 2013 Volume 218() pp:80-86
Publication Date(Web):15 March 2013
DOI:10.1016/j.surfcoat.2012.12.030
Ni–Cr (80/20 at.%) alloy was deposited on the copper foil substrate by DC magnetron sputtering process. Taguchi method was applied to optimize the deposition parameters including sputtering power, substrate temperature, and argon pressure. Sputtering power was found to be the most prominent factor that influenced the electrical properties of Ni–Cr alloy film by employing the range analysis. Embedded thin film resistor (ETFR) with a high resistivity of 6.69 × 10− 4 Ω.cm and a low temperature coefficient of resistance of 374.78 ppm/K was obtained under the optimized deposition conditions. A feasible way was demonstrated to fabricate high-quality Ni–Cr alloy on copper foil as ETFR materials.Highlights►High-quality Ni–Cr alloy sputtered on copper foil was made and investigated. ►Taguchi method was applied in the selection of the optimal deposition conditions. ►A high resistivity of 6.69 × 10− 4 Ω.cm was achieved. ►A low temperature coefficient of resistance of 374.78 ppm/K was attainted. ►A feasible way was introduced to fabricate Ni–Cr alloy as ETFR materials.
Co-reporter:Lifei Lai, Xianzhu Fu, Rong Sun, Ruxu Du
Surface and Coatings Technology 2013 Volume 235() pp:552-560
Publication Date(Web):25 November 2013
DOI:10.1016/j.surfcoat.2013.08.023
•Different substrates led to different microstructure and resistivity of NiCr film.•The different substrates had little effect on the TCR of NiCr thin films.•Copper substrate was more suitable for NiCr thin film embedded resistors.NiCr (80/20 at.%) alloy thin film was deposited on the copper foil, glass and silicon substrates by DC magnetron sputtering method, respectively. The structure, stress and resistivity of NiCr thin films were affected by the different substrates. The preferred orientations of NiCr thin film were Ni (011) and Cr (011) on the copper foil substrate with rough surface, while only Ni (111) on the glass and silicon substrates. And the internal stress of NiCr thin film was tensile stress on the copper foil, while compressive stress on the glass and silicon substrates. These differences then resulted in larger resistivity of NiCr thin film deposited on copper foil than glass or silicon substrate. However, the temperature coefficient of resistance (TCR) of NiCr thin film was slightly influenced by the different substrates.
Co-reporter:Lifei Lai, Wenjin Zeng, Xianzhu Fu, Rong Sun, Ruxu Du
Journal of Alloys and Compounds 2012 Volume 538() pp:125-130
Publication Date(Web):15 October 2012
DOI:10.1016/j.jallcom.2012.05.102
Ni–Cr (80/20 at.%) alloy was deposited on the copper foil substrate as embedded thin film resistor (ETFR) materials by DC magnetron sputtering method. Electrical properties and microstructure of Ni–Cr ETFR under different annealing conditions were investigated. Results indicated that the ETFR exhibited the smallest temperature coefficient of resistance (TCR) after annealing at 250 °C for 540 s in N2. The structure, stress, composition and surface morphology of ETFR materials were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS) and atomic force microscopy (AFM). The rarely reported hexagonal Ni (0 1 1), (0 0 2) and (1 0 3) in Ni–Cr thin film were found in Ni–Cr (80/20 at.%) ETFR materials. The chemical states on the surface of the ETFR materials after annealing were mainly Cr2O3. The segregation of chromium during annealing can affect the resistivity and temperature coefficient of resistance (TCR). The different surface morphology of ETFR in annealing will affect the resistivity.Highlights► Annealing effect on the properties of embedded Ni–Cr thin film resistor. ► A good annealing condition was achieved. ► The rarely observed hexagonal Ni (0 1 1), (0 0 2) and (1 0 3) were found. ► The segregation of chromium in thin film can affect the resistivity and TCR. ► The results obtained would be helpful in achieving a good embedded resistor.
Co-reporter:Wenhu Yang, Shuhui Yu, Rong Sun, Ruxu Du
Ceramics International 2012 Volume 38(Issue 5) pp:3553-3562
Publication Date(Web):July 2012
DOI:10.1016/j.ceramint.2011.12.071
Abstract
A systematic study was carried out on the magnetic, dielectric and microwave absorption properties of the two-phase FeAlSi/epoxy and three-phase FeAlSi/BaTiO3/epoxy composites through experimental and simulation method. A percolation effect was observed in the dielectric, but not in the magnetic behavior of the FeAlSi/epoxy composites when the FeAlSi content was high. The 2D modeling shows that the high electric energy density is responsible for the high permittivity near the percolation threshold (49 vol%). On the other hand, the permeability of the composites matches well with the effective medium theory model (EMT), indicating that the permeability of FeAlSi/epoxy composite is more associated with the filler size and shape. Theoretical calculations show that the increment of the FeAlSi and BaTiO3 loading, as well as the thickness will cause the absorption peak position to shift to low frequencies. The microwave absorption of these composites can be mainly attributed to the dielectric loss and magnetic loss.
Co-reporter:Hu Yougen;Zhao Tao;Zhu Pengli;Sun Rong
Colloid and Polymer Science 2012 Volume 290( Issue 5) pp:401-409
Publication Date(Web):2012 March
DOI:10.1007/s00396-011-2555-0
This article presents a facile method for the preparation of polystyrene/silver (PS/Ag) composite microspheres. In this approach, monodisperse PS spheres were synthesized via dispersion polymerization and modified by sulfonation to obtain sulfonated PS spheres with sulfonic acid groups on the surfaces, and then adsorbed Sn2+ ions by electrostatic interaction and used as templates. PS/Ag composite microspheres were prepared successively by addition of [Ag(NH3)2]+ complex ions to the templates dispersion, adsorbing to the surfaces of templates, and then reduction of [Ag(NH3)2]+ complex ions to Ag nanoparticles by sodium potassium tartrate. The results showed that monodisperse PS spheres with sulfonic acid groups on the surfaces were coated by an incomplete and nonuniform coverage of Ag nanoparticles in the absence of Sn2+ ions. In the presence of Sn2+ ions, however, complete and uniform Ag nanoparticles coatings were obtained on the entire PS sphere. And the deposition density and size of Ag nanoparticles can be controlled by [Ag(NH3)2]+ concentration. The resulting PS/Ag composite microspheres were characterized by SEM, TEM, XRD, TGA, and UV-vis. Preliminary catalytical tests indicated these PS/Ag composite microspheres showed good catalytic properties.
Co-reporter:Wenhu Yang, Shuhui Yu, Rong Sun, Ruxu Du
Acta Materialia 2011 Volume 59(Issue 14) pp:5593-5602
Publication Date(Web):August 2011
DOI:10.1016/j.actamat.2011.05.034
Abstract
The microstructure and dielectric properties of composites comprising polyvinylidene fluoride (PVDF) and calcium copper titanate (CCTO) particles have been investigated. Nano- and microsized CCTO were employed separately and investigated comparatively. The effective dielectric constant (εr) of the composite containing 40 vol.% nanosized CCTO filler is over 106 at 102 Hz and room temperature, which is substantially higher than that of the composite containing microsized CCTO, of which the εr value is 35.7 (with 40 vol.%). The εr and loss tangent (tan δ) decrease with temperature for the composite containing nanosized CCTO, while the one with microsized CCTO shows the opposite tendency. For the composite with nanosized CCTO, the conductivity decreases sharply with increasing temperature in the low frequency range (100–104 Hz) and slightly increases in the high frequency range, while the conductivity of the composite with microsized CCTO is nearly independent of temperature. The theoretical calculations demonstrate that the activation energies of the composites containing nano- or microsized CCTO are −0.52 and 0.051 eV, indicating active interfaces and insulated grain boundaries in these two composites, respectively. Theoretical analysis also shows that the dielectric performance of the composite with nanosized CCTO does not follow the conventional mixing rules and the giant dielectric constant comes mainly from the interfacial polarization. The dielectric property of the composite containing microsized CCTO matches well with the Maxwell–Garnett and effective medium theory models, indicating insulate interfaces between the fillers and the matrix. The results obtained in this study indicate that the composite containing microsized CCTO may be suitable for embedded device applications, while the one with nanosized CCTO may find a new application in the temperature sensor field.
Co-reporter:Xiaolin Wu, Yihai Wang, Pengli Zhu, Rong Sun, Shuhui Yu, Ruxu Du
Materials Letters 2011 Volume 65(Issue 4) pp:705-707
Publication Date(Web):28 February 2011
DOI:10.1016/j.matlet.2010.11.022
The technique of UV–vis spectrum can offer the ability for characterizing phase transition process and structure characteristics of phase change materials. Experiment testing absorbance change of UV–vis spectrum has been conducted on the phase transition process of PMMA–SiO2@paraffin microcapsules with copper-chelating as the ion probe. The phase transition process has successfully measured that there was little change in absorbance of UV–vis spectrum, which should be caused by the heat absorbance of the phase change materials. After the phase change was completed, the spectrum absorbance of microcapsules had a sudden drop. The special UV–vis spectrum of PMMA–SiO2@paraffin microcapsules should be caused by the changes of charge distribution or molecular interaction of ion probe Cu(II) chelating in microcapsules. The UV–vis spectrum can be used to study the phase change process of the Cu(II)–PMMA–SiO2@paraffin microcapsules as well as other similar configurations with Cu(II) chelating as the ion probe.Cu(II)–PMMA–SiO2@paraffin microcapsules have special UV–vis spectrum caused by the changes of charge distribution or molecular interaction of copper-chelating in shell.Research Highlights► UV–vis spectrum was used to prove the core–shell structure and study the microstructure change of microcapsules. ► UV-vis spectrum was used to detect phase change process. ► The microcapsules were modified by opper(II) chelate.
Co-reporter:Xiaoliang Zeng, Shuhui Yu, Rong Sun, Ruxu Du
Materials Chemistry and Physics 2011 Volume 131(1–2) pp:387-392
Publication Date(Web):15 December 2011
DOI:10.1016/j.matchemphys.2011.09.060
Bismaleimide-triazine resin/barium titanate (BT/BaTiO3) nanocomposite films were prepared by mixing the nano-BaTiO3 particles into BT resin, followed by films casting and thermal cure. The surface modification of BaTiO3 nanoparticles with silane coupling agent results in excellent dispersion and enhances the interaction between BaTiO3 and the BT matrix. The derived nanocomposite films exhibit improved dielectric constant, while the dielectric loss remains at a low level (<0.05). For the nanocomposite film containing 70 wt% of BaTiO3, the effective dielectric constant at room temperature reaches 23.63, which is about 7 times larger than that of pure BT resin, and the dielectric loss is only 0.0212 at 100 Hz. The dielectric properties of the nanocomposite films are nearly frequency-independent, which is attributed to the excellent dispersion of BaTiO3 nanoparticles in the BT matrix. The interaction between BaTiO3 and BT affects not only the phase transition of BaTiO3, but also the thermal behavior of BT. Moreover, the nanocomposite films exhibit improved thermal resistance. The highest glass transition temperature (Tg) is 261 °C, indicating good reliability as dielectric materials in applications.Highlights► The bismaleimide-triazine resin/BaTiO3 nanocomposite films were prepared. ► We examine the dielectric and thermal properties. ► Increasing BaTiO3 will increase the dielectric constant while the loss remains low. ► The highest glass transition temperature is 261 °C.
Co-reporter:Tao Zhao, Rong Sun, Shuhui Yu, Zhijun Zhang, Limin Zhou, Haitao Huang, Ruxu Du
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2010 Volume 366(1–3) pp:197-202
Publication Date(Web):20 August 2010
DOI:10.1016/j.colsurfa.2010.06.005
In this work, size-controlled silver nanoparticles were prepared with liquid phase chemical method in the ethylene glycol/polyvinylpyrrolidone media. Crystal structure, size, thermal properties and surface chemistry state of the silver nanoparticles were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), thermal analysis (TA) and X-ray photoelectron spectroscopy (XPS). The particle size can be conveniently adjusted to 80 nm, 50 nm, 30 nm and 10 nm by controlling the experimental parameters such as the ratio of PVP to AgNO3, and the amount of ammonia added as complexing agent. The as-obtained silver nanoparticles can be dispersed in water, ethanol and other polar solvents, which has attractive applications in electrical and biological fields.
Co-reporter:Yan-Jun Wan, Peng-Li Zhu, Shu-Hui Yu, Rong Sun, Ching-Ping Wong, Wei-Hsin Liao
Carbon (May 2017) Volume 115() pp:
Publication Date(Web):May 2017
DOI:10.1016/j.carbon.2017.01.054
Ultralight cellulose fiber/thermally reduced graphene oxide (CF/RGO) hybrid aerogel with super-elasticity and excellent electromagnetic interference (EMI) shielding capability was fabricated through lyophilization and carbonization process. CF/RGO aerogel with 5 mm thickness exhibits high EMI shielding effectiveness (SE) of ∼47.8 dB after annealing at 1000 °C with 5% hydrogen-argon mixture atmosphere. The superior SE is mainly ascribed to the cellular structure and good electrical conductivity of aerogel. The density of CF/RGO aerogel is as low as 2.83 mg/cm3, leading to ultrahigh specific shielding effectiveness (up to 33780 dB cm2/g). The volume/shape of obtained monolithic carbon material can be preserved very well after thermal treatment. The effects of RGO content and annealing conditions on EMI shielding and mechanical properties were investigated. Moreover, the hybrid aerogel possesses excellent mechanical resilience even with large strain (80% reversible compressibility) and outstanding cycling stability. In addition, adjustable EMI shielding capability could be realized by simple mechanical compression. These results demonstrate a promising and facile approach to fabricate low-cost and volume-preserving porous carbon material with superior and tunable EMI shielding performance for potential applications in aerospace and wearable electronic devices.
Co-reporter:Libo Deng, Anna E. Lewandowska, Robert J. Young, Guoping Zhang, Rong Sun, Stephen J. Eichhorn
Reactive and Functional Polymers (December 2014) Volume 85() pp:235-238
Publication Date(Web):1 December 2014
DOI:10.1016/j.reactfunctpolym.2014.09.001
Electrospun cellulose nanofibres have been graphitized in the presence of silica (SiO2) nanoparticles. The structure of the resultant SiC/C hybrids was characterised using transmission electron microscopy, X-ray diffraction and Raman spectroscopy. Bamboo-like silicon carbide (SiC) nanostructures were observed emanating from the nanofibres treated at 1500 °C which were thought to grow through a vapour–liquid–solid process. The formation of SiC was also thought to lead to a higher degree of graphitization for the electrospun cellulose fibres. These porous and graphitized nanofibres might find applications in electrochemical energy storage.
Co-reporter:Yan-Jun Wan, Peng-Li Zhu, Shu-Hui Yu, Wen-Hu Yang, Rong Sun, Ching-Ping Wong, Wei-Hsin Liao
Composites Science and Technology (22 March 2017) Volume 141() pp:
Publication Date(Web):22 March 2017
DOI:10.1016/j.compscitech.2017.01.010
Novel barium titanate (BT) layer coated and thermally reduced graphene oxide (TGO) hybrid sheets (BT@TGO) were successfully synthesized by a facile sol-gel method combining with thermal treatment process (600 °C) under nitrogen atmosphere. The BT precursors attached on graphene oxide (GO) sheets were crystallized into perovskite structure with high permittivity and GO sheets were thermally reduced heavily at such high temperature simultaneously. The hybrids were used as filler to fabricate high performance dielectric polyvinylidene fluoride (PVDF) composites by solution blending method and their dielectric performances were studied. It was found that addition of BT@TGO decreases the electrical conductivity when compared with TGO/PVDF composites and pure PVDF, and BT@TGO/PVDF composites exhibit not only high dielectric constant but also low dielectric loss. For instance, at 103 Hz, the dielectric constant of PVDF composites containing 8.0 wt% BT@TGO is up to ∼56.3 at room temperature, which is over 5 times than that of pure PVDF polymer (∼10.3). More importantly, the dielectric loss is suppressed and only 0.058, which should be attributed to the effective encapsulation of insulating BT layer with high permittivity on the TGO surface. In addition, the improved thermal stability and crystallization behavior of BT@TGO/PVDF composites were also investigated.
Co-reporter:Songfang Zhao, Jinhui Li, Duxia Cao, Yongju Gao, Wangping Huang, Guoping Zhang, Rong Sun and Ching-Ping Wong
Journal of Materials Chemistry A 2016 - vol. 4(Issue 27) pp:NaN6674-6674
Publication Date(Web):2016/06/13
DOI:10.1039/C6TC01728B
Conductive elastomers, an irreplaceable component of stretchable electronics, have recently gained significant attention. Herein, we report highly conductive, sensitive, stretchable, and fully printed hybrid composites comprising carbon nanotubes (CNTs), silver nanoparticles (Ag NPs) and hydroxyl-poly(styrene-block-butadiene-block-styrene) (OH-SBS) polymers. The electrically conductive composites are fabricated via direct evaporation of CNT-dispersed OH-SBS suspension under mild heating conditions, followed via an iterative process of silver precursor absorption and reduction, generating large amounts of Ag NPs on both the surface and inner regions of the CNT-embedded composites. The obtained CNT–Ag NP embedded composites possess a superior electrical conductivity of 1228 S cm−1, a high break elongation of 540%, and a high gauge factor of 26500. The unique hierarchical multiscale hybrid architecture of CNT–Ag NPs and the utilization of OH-SBS enable the as-prepared composites to exhibit huge piezoresistive behavior with a broad range of tensile strains. Moreover, handwritten electric circuits with diverse geometries are designed, and the printed strain gauge sensor could successfully detect sign language via its strain-sensing behavior. We believe that our hierarchical multiscale hybrid design could pave the way for the simple fabrication of stretchable circuits for wearable electronics.
Co-reporter:Jinhui Li, Guoping Zhang, Libo Deng, Songfang Zhao, Yongju Gao, Kun Jiang, Rong Sun and Chingping Wong
Journal of Materials Chemistry A 2014 - vol. 2(Issue 48) pp:NaN20649-20649
Publication Date(Web):2014/10/17
DOI:10.1039/C4TA04941A
Covalently bonded graphene oxide/polyurethane (GO/PU) composites with significant reinforcement and thermally healable properties were developed via in situ polymerization based on Diels–Alder (DA) chemistry. The PU prepolymer was prepared with GO, 4,4-diphenylmethane diisocyanate, and poly(tetramethylene glycol) and blocked by using furfuryl alcohol firstly. Then the prepolymer was cross-linked by using bifunctional maleimide via DA chemistry. SEM shows that the GO was dispersed uniformly in the PU matrix. The DA and retro-DA reactions were characterized by Fourier transform infrared spectroscopy and differential scanning calorimetry separately. Tensile tests showed that with the incorporation of 0.1 wt% of GO, the tensile modulus of GO/PU composites increased from 9.80 MPa to 21.95 MPa, and the tensile strength and elongation at break of the GO/PU composites increased by more than 367% and 210%, respectively. Furthermore, the composites had thermally healable ability which was inspected by using an atomic force microscope and the strain–stress test. The healing efficiency of 78% on average was achieved which was determined by the recovery of breaking stress and a healing mechanism was tentatively proposed. Therefore, the covalently bonded self-healing GO/PU composites could be used as smart materials and structural materials.
Co-reporter:Yu Zhang, Pengli Zhu, Liang Chen, Gang Li, Fengrui Zhou, Daoqiang (Daniel) Lu, Rong Sun, Feng Zhou and Ching-ping Wong
Journal of Materials Chemistry A 2014 - vol. 2(Issue 30) pp:NaN11973-11973
Publication Date(Web):2014/06/24
DOI:10.1039/C4TA01920B
Novel hierarchical architectures of porous copper (Cu) microspheres assembled with nanoparticles have been successfully synthesized by ingeniously selecting the precursor and complexant through a facile wet chemical reduction method. The resultant porous Cu microspheres have a size distribution of 700 ± 50 nm and have excellent monodispersity. The synergistic effect between the precursor of slightly soluble copper hydroxide and the complexants of polyacrylic acid and ethanol amine exactly induces the generation of unique porous hierarchical architectures. The obtained porous Cu microspheres were applied to reduce and degrade different organic dyes with high concentrations (4-nitrophenol, methylene blue, and rhodamine B) in the presence of NaBH4. Compared with solid Cu particles that have the same size, these porous Cu microspheres exhibit more excellent catalytic activity due to their hierarchical structures. Moreover, the catalyst with universal applicability could be easily separated from the catalytic system and sustainedly possess high stability in recycled reactions.
Co-reporter:Jinhui Li, Songfang Zhao, Guoping Zhang, Yongju Gao, Libo Deng, Rong Sun and Ching-Ping Wong
Journal of Materials Chemistry A 2015 - vol. 3(Issue 30) pp:NaN15488-15488
Publication Date(Web):2015/06/16
DOI:10.1039/C5TA03595C
Endowing graphene sponge with compressibility and conductivity offers the possibility to regenerate piezoresistivity and is therefore of great interest in the field of sensors. In this work, highly compressible three-dimensional graphene-only sponge (CGS) was prepared through a facile method by using ammonium sulfide and ammonia solutions under mild conditions. The morphologies and microstructures of the as-prepared CGSs can be controlled by adjusting the mass ratio of graphene oxide (GO) to ammonium sulfide which changed from a metallic sheen bulk with a leaf-shaped structure to a black sponge with a porous structure. Besides, by simply changing the concentrations of GO, CGSs with different porosity, conductivity as well as mechanical strength were obtained. Moreover, the resultant CGSs show ultralow density (as low as 4.9 mg cm−3), high porosity (as much as 99.8%), great compressibility (as much as the strain of 80%), and excellent stability (100 cycles) during compression. Furthermore, the sensitive variation of electrical resistance and cycle stability was validated under the compressive strain of 50% which make CGSs great candidates for pressure-responsive sensors, elastic conductors and other applications.
Co-reporter:Ying Guo, Yi-Tao Xu, Bo Zhao, Tao Wang, Kai Zhang, Matthew M. F. Yuen, Xian-Zhu Fu, Rong Sun and Ching-Ping Wong
Journal of Materials Chemistry A 2015 - vol. 3(Issue 26) pp:NaN13661-13661
Publication Date(Web):2015/04/28
DOI:10.1039/C5TA01891A
Novel urchin-like Pd@CuO–Pd yolk–shell nanostructures are synthesized through subsequent oxidation of Pd@Cu2O truncated octahedron core–shell precursors with a PdCl42− aqueous solution. The permeable hierarchical CuO shells are constructed by a radially standing 1D single-crystalline nanothorn with Pd nanoparticles. The Pd nanocube cores are encapsulated and confined in the void space of the urchin-like shells. The urchin-like yolk–shell Pd@CuO–Pd nanostructures demonstrate excellent electrocatalytic activity and selectivity for glucose oxidation. Enzyme-free glucose biosensors based on the urchin-like yolk–shell Pd@CuO–Pd electrocatalysts display a higher sensitivity (665.9 μA cm−2 mM−1) than those of the CuO nanoparticles (455.8 μA cm−2 mM−1), Cu2O nanoparticles (220.4 μA cm−2 mM−1), Pd@Cu2O truncated octahedra (179.1 μA cm−2 mM−1), Pd mixtures (65.5 μA cm−2 mM−1) and Pd nanocubes (1.42 μA cm−2 mM−1). The outstanding electrocatalytic performance of the urchin-like Pd@CuO–Pd yolk–shell nanostructures might be ascribed to two reasons: the unique hierarchical yolk–shell structures provide highly exposed active sites and act as an individualized nanoreactor to enhance the mass diffusion and transport of reactants at the electrode/electrolyte interface. Moreover, the nanocomposite of metal oxide semiconductor CuO and noble metal Pd would result in a synergetic effect to improve the electrocatalysis.
Co-reporter:Tao Wang, Bo Zhao, Hong Jiang, Hai-Peng Yang, Kai Zhang, Matthew M. F. Yuen, Xian-Zhu Fu, Rong Sun and Ching-Ping Wong
Journal of Materials Chemistry A 2015 - vol. 3(Issue 45) pp:NaN23041-23041
Publication Date(Web):2015/09/28
DOI:10.1039/C5TA04705F
Ternary cobalt nickel sulfide (CoNi2S4) flower-like nanosheets are directly grown on three dimensional (3D) hierarchically porous nickel skeletons by one-step electro-deposition. The resultant 3D porous Ni/CoNi2S4 composites could serve as binder-free integrated electrodes for supercapacitors, which exhibit higher capacitance than those of 3D porous Ni/Co9S8, 3D porous Ni/Ni3S2, Ni foam/CoNi2S4 and smooth Ni/CoNi2S4 electrodes. Furthermore, the 3D porous Ni/CoNi2S4 electrodes demonstrate better electrochemical reversibility and excellent rate capability. The super electrochemical capacitive behavior might be attributed to the highly interconnected conductive networks of 3D hierarchically porous Ni scaffold supported CoNi2S4 flower-like nanosheets with a large specific area and highly active sites.
Co-reporter:Xiaoliang Zeng, Libo Deng, Yimin Yao, Rong Sun, Jianbin Xu and Ching-Ping Wong
Journal of Materials Chemistry A 2016 - vol. 4(Issue 25) pp:NaN6044-6044
Publication Date(Web):2016/05/31
DOI:10.1039/C6TC01501H
Flexible polymer-based dielectric materials that are used to store dielectric energy have widely been used in modern electronics and electric power systems, due to their relatively high energy density, light weight, low cost, etc. However, owing to the growing global environmental issues and a rapid consumption of nonrenewable polymer resources, there exists a strong desire to fabricate flexible dielectric materials using biodegradable materials. Here, we report on flexible dielectric papers based on biodegradable cellulose nanofibers (CNFs) and carbon nanotubes (CNTs) for dielectric energy storage. Highly ordered, homogeneous CNF/CNT papers have been fabricated using a facile vacuum-assisted self-assembly technique. The obtained paper possesses a high dielectric constant of 3198 at 1.0 kHz, thus leading to enhanced dielectric energy storage capability (0.81 ± 0.1 J cm−3), which is attributed to the presence of a low loading of CNTs (4.5 wt%). Moreover, the CNF/CNT papers are mechanically flexible and show improved mechanical strength. These findings enable feasible fabrication of high-performance flexible dielectric materials using ecofriendly materials.
Co-reporter:Xiaoliang Zeng, Shuhui Yu, Lei Ye, Mingyang Li, Zhilong Pan, Rong Sun and Jianbin Xu
Journal of Materials Chemistry A 2015 - vol. 3(Issue 1) pp:NaN195-195
Publication Date(Web):2014/10/28
DOI:10.1039/C4TC01051E
Multiwalled carbon nanotubes (MWCNTs) have been widely used as mechanical reinforcement fillers for polymers during the past decades. However, the high electrical conductivity of MWCNTs hampers their applications in some specific fields. In this study, the MWCNT was encapsulated with an insulating silicon oxide (SiO2) layer to form core–shell structure MWCNT@SiO2 nanoparticles, which were used to fill bismaleimide-triazine (BT) resin. The obtained polymer nanocomposites possessed high mechanical strength, electrical insulation, improved thermal stability, and good optical transparency. These excellent properties were attributed to the strong interfacial interaction between MWCNT@SiO2 and the polymer, as well as the suppression of electron transport by the SiO2 layer on the MWCNT surface. The nanocomposites were employed to fabricate a printed circuit substrate, on which a frequency “flasher” circuit and the electrical components worked well. This work has demonstrated the possibility of using MWCNTs as mechanical reinforcement fillers in polymer nanocomposites, which simultaneously possess electrical insulation.
Co-reporter:Xiaoliang Zeng, Lei Ye, Rong Sun, Jianbin Xu and Ching-Ping Wong
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 26) pp:NaN16714-16714
Publication Date(Web):2015/05/29
DOI:10.1039/C5CP02192H
The viscoelasticity of boron nitride nanosheet (BNNS) aerogel has been observed and investigated. It is found that the BNNS aerogel has a high damping ratio (0.2), while it exhibits lightweight and negligible temperature dependence below 180 °C. The creep behavior of the BNNS aerogel markedly demonstrates its strain dependence on stress magnitude and temperature, and can be well simulated by the classical models.
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