Co-reporter:Yang Li, Rui Yao, Huanhuan Wang, Xiaoming Wu, Jinzhu Wu, Xiaohong Wu, and Wei Qin
ACS Applied Materials & Interfaces April 5, 2017 Volume 9(Issue 13) pp:11711-11711
Publication Date(Web):March 17, 2017
DOI:10.1021/acsami.7b02609
Highly conductive and optical transparent Al-doped ZnO (AZO) thin film composed of ZnO with a Zn–Al–O interface was fabricated by thermal atomic layer deposition (ALD) method. The as-prepared AZO thin film exhibits excellent electrical and optical properties with high stability and compatibility with temperature-sensitive flexible photoelectronic devices; film resistivity is as low as 5.7 × 10–4 Ω·cm, the carrier concentration is high up to 2.2 × 1021 cm–3. optical transparency is greater than 80% in a visible range, and the growth temperature is below 150 °C on the PEN substrate. Compared with the conventional AZO film containing by a ZnO–Al2O3 interface, we propose that the underlying mechanism of the enhanced electrical conductivity for the current AZO thin film is attributed to the oxygen vacancies deficiency derived from the free competitive growth mode of Zn–O and Al–O bonds in the Zn–Al–O interface. The flexible transparent transistor based on this AZO electrode exhibits a favorable threshold voltage and Ion/Ioff ratio, showing promising for use in high-resolution, fully transparent, and flexible display applications.Keywords: atomic layer deposition; AZO; flexible; oxygen vacancy; TFT;
Co-reporter:Yan Chen;Songtao Lu;Jia Zhou;Wei Qin;Ogechi Ogoke;Gang Wu
Journal of Materials Chemistry A 2017 vol. 5(Issue 1) pp:102-112
Publication Date(Web):2016/12/20
DOI:10.1039/C6TA08039A
Lithium sulfide (Li2S) has drawn special attention as a promising cathode material for emerging energy storage systems due to its high theoretical specific capacity and great compatibility with lithium metal-free anodes. However, Li2S cathodes urgently require a solution to increase their poor electrical conductivity and to suppress the dissolution of long-chain polysulfide (Li2Sn, 4 ≤ n ≤ 8) species into electrolyte. To this end, we report a free-standing Al2O3–Li2S–graphene oxide sponge (GS) composite cathode, in which ultrathin Al2O3 films are preferentially coated on Li2S by an atomic layer deposition (ALD) technique. As a result, a combination of high electron conductivity (from GS) and strong binding with Li2Sn (from ultrathin Al2O3 films) was designed for cathodes. The newly developed Al2O3–Li2S–GS cathodes are able to deliver a highly reversible capacity of 736 mA h gLi2S−1 (427 mA h gcathode−1) at 0.2C, which is much higher than that of corresponding cathodes without Al2O3 (59%). Also, the long-term cycling stability of Al2O3–Li2S–GS cathodes was demonstrated up to 300 cycles at 0.5C with an excellent capacity retention of 88%. In addition, combined with density functional theory calculations, the promotional mechanism of ultrathin Al2O3 films was elucidated using extensive characterization. The ultra-thin Al2O3 film with optimal thickness not only acts as a physical barrier to Li2S nanoparticles, but provides a strong binding interaction to suppress Li2Sn species dissolution.
Co-reporter:Songtao Lu;Huanhuan Wang;Jia Zhou;Wei Qin
Nanoscale (2009-Present) 2017 vol. 9(Issue 3) pp:1184-1192
Publication Date(Web):2017/01/19
DOI:10.1039/C6NR07868K
Although zinc oxide (ZnO), a low-cost and naturally abundant material, has a high theoretical specific capacity of 987 mA h g−1 for hosting lithium ions, its application as an anode material has been hindered by its rapid capacity fading, mainly due to a large volume change (around 228%) upon repeated charge–discharge cycles. Herein, using carbon black (CB) powder as a support, ZnO–carbon black (denoted as ZnO–CB) nanocomposites were successfully fabricated using the atomic layer deposition (ALD) method. This method was able to produce strong interfacial molecular bindings between ZnO nanoclusters and the carbon surface that provide stable and robust electrical contact during lithiation and delithiation processes, as well as ZnO nanoclusters rich in oxygen vacancies (OVs) for faster Li-ion transport. Overall, the nanocomposites were able to deliver a high discharge specific capacity of 2096 mA h g−1ZnO at 100 mA g−1 and stable cyclic stability with a specific capacity of 1026 mA h g−1ZnO maintained after 500 cycles. The composites also have excellent rate capability, and a reversible capacity at a high 1080 mA h g−1ZnO at 2000 mA g−1. The facile but unique synthesis method demonstrated in this work for producing nanostructures rich in OVs and nanocomposites with strong coupling via interfacial molecular bindings could be extended to the synthesis of other oxide based anode materials and therefore could have general significance for developing high energy density lithium ion batteries.
Co-reporter:Lu Han;Wei Qin;Jia Zhou;Jiahuang Jian;Songtao Lu;Guohua Fan;Peng Gao;Boyu Liu
Nanoscale (2009-Present) 2017 vol. 9(Issue 16) pp:5141-5147
Publication Date(Web):2017/04/20
DOI:10.1039/C7NR00581D
Metal modified C60 is considered to be a potential hydrogen storage medium due to its high theoretical capacity. Research interest is growing in various hybrid inorganic compounds-C60. While the design and synthesis of a novel hybrid inorganic compound-C60 is difficult to attain, it has been theorized that the atomic hydrogen could transfer from the inorganic compound to the adjacent C60 surfaces via spillover and surface diffusion. Here, as a proof of concept experiment, we graft Co9S8 onto C60via a facile high energy ball milling process. The Raman, XPS, XRD, TEM, HTEM and EELS measurements have been conducted to evaluate the composition and structure of the pizza-like hybrid material. In addition, the electrochemical measurements and calculated results demonstrate that the chemical “bridges” (C–S bonds) between these two materials enhance the binding strength and, hence, facilitate the hydriding reaction of C60 during the hydrogen storage process. As a result, an increased hydrogen storage capacity of 4.03 wt% is achieved, along with a favorable cycling stability of ∼80% after 50 cycles. Excluding the direct hydrogen storage contribution from Co9S8 in the hybrid paper, the hydrogen storage ability of C60 was enhanced by 5.9× through the hydriding reaction caused by the Co9S8 modifier. Based on these experimental measurements and theoretical calculations, the unique chemical structure reported here could potentially inspire other C60-based advanced hybrids.
Co-reporter:Lu Han, Wei Qin, Jiahuang Jian, Jiawei Liu, Xiaohong Wu, Peng Gao, Benjamin Hultman, Gang Wu
Journal of Power Sources 2017 Volume 358(Volume 358) pp:
Publication Date(Web):1 August 2017
DOI:10.1016/j.jpowsour.2017.05.026
•A binder-free sandwich-structured rGO/Co1−xS/rGO hybrid paper was obtained.•The Co1−xS was immobilized in between the rGO sheets by the chemical “bridges”.•The hydrogen storage ability of rGO was enhanced by 10× through spillover effects.Reduced graphene oxide (rGO) based two-dimensional (2D) structures have been fabricated for electrochemical hydrogen storage. However, the effective transfer of atomic hydrogen to adjacent rGO surfaces is suppressed by binders, which are widely used in conventional electrochemical hydrogen storage electrodes, leading to a confining of the performance of rGO for hydrogen storage. As a proof of concept experiment, a novel strategy is developed to fabricate the binder-free sandwich-structured rGO/Co1−xS/rGO hybrid paper via facile ball milling and filtration process. Based on the structure investigation, Co1−xS is immobilized in the space between the individual rGO sheets by the creation of chemical “bridges” (CS bonds). Through the CS bonds, the atomic hydrogen is transferred from Co1−xS to rGO accompanying a CH chemical bond formation. When used as an electrode, the hybrid paper exhibits an improved hydrogen storage capacity of 3.82 wt% and, most importantly, significant cycling stability for up to 50 cycles. Excluding the direct hydrogen storage contribution from the Co1−xS in the hybrid paper, the hydrogen storage ability of rGO is enhanced by 10× through the spillover effects caused by the Co1−xS modifier.Download high-res image (309KB)Download full-size image
Co-reporter:Jia Zhou
Journal of Materials Chemistry C 2017 vol. 5(Issue 18) pp:4505-4510
Publication Date(Web):2017/05/11
DOI:10.1039/C7TC00808B
The recently synthesized freestanding four-atom-thick double-layer sheet of ZnSe is a promising material for next-generation ultrathin optoelectronic nanodevices. In this theoretical work, we report two other novel double-layer sheets of ZnSe, with similar stability but distinct structures. These two new double-layer sheets of ZnSe could be considered by cutting along the wurtzite (WZ) bulk instead of the zinc blende (ZB) bulk. All these three layered sheets demonstrate a significantly strong quantum confinement effect, showing a large enhancement of the band gap compared with their three-dimensional (3D) bulks, by state-of-the-art calculations based on quasiparticle GW and the Bethe–Salpeter equation. Furthermore, the optical absorbance shows that the atomic arrangements of these three double-layer sheets of ZnSe play a significant role in the respective distinct photoabsorption behaviors, potentially important for a wealth of applications including solar water splitting.
Co-reporter:Yan Chen;Songtao Lu;Jia Zhou;Wei Qin
Advanced Functional Materials 2017 Volume 27(Issue 25) pp:
Publication Date(Web):2017/07/01
DOI:10.1002/adfm.201700987
Lithium sulfide (Li2S) has attracted increasing attention as a promising cathode because of its compatibility with more practical lithium-free anode materials and its high specific capacity. However, it is still a challenge to develop Li2S cathodes with low electrochemical overpotential, high capacity and reversibility, and good rate performance. This work designs and fabricates a practical Li2S cathode composed of Li2S/few-walled carbon nanotubes@reduced graphene oxide nanobundle forest (Li2S/FWNTs@rGO NBF). Hierarchical nanostructures are obtained by annealing the Li2SO4/FWNTs@GO NBF, which is prepared by a facile and scalable solution-based self-assembly method. Systematic characterizations reveal that in this unique NBF nanostructure, FWNTs act as axial shafts to direct the structure, Li2S serves as the internal active material, and GO sheets provide an external coating to minimize the direct contact of Li2S with the electrolyte. When used as a cathode, the Li2S/FWNTs@rGO NBF achieve a high capacity of 868 mAh g−1Li2S at 0.2C after 300 cycles and an outstanding rate performance of 433 mAh g−1Li2S even at 10C, suggesting that this Li2S cathode is a promising candidate for ultrafast charge/discharge applications. The design and synthetic strategies outlined here can be readily applied to the processing of other novel functional materials to obtain a much wider range of applications.
Co-reporter:Jia Zhou, Xiaohong Wu
Materials Today Chemistry 2017 Volume 4(Volume 4) pp:
Publication Date(Web):1 June 2017
DOI:10.1016/j.mtchem.2016.10.001
•Tetragonal doped ZnSe monolayers have been investigated by first-principles calculations.•The electronic and magnetic properties of novel three-atom-thick ZnSe monolayers with various dopants have been studied.•The pristine tetragonal ZnSe monolayer inclines as an n-type semiconductor by certain doping.Doping is a very important and effective method to be used to modulate the properties of two-dimensional (2D) materials. In this work, the electronic and magnetic properties of ultrathin tetragonal ZnSe monolayer doped by twenty different kinds of atoms neighboring Zn/Se were systemically investigated using first-principles calculations. Substitution at the Zn/Se sites was found to be easy if the monolayer was grown under Zn-/Se-poor conditions. Among non-metal dopants, only F atom is thermodynamically favored to replace Se atom, while a number of metal atoms (i.e. Ca, Sc, Ti, and Mn) are able to substitute Zn atom. It is suggested by theoretical calculations that pristine ZnSe monolayer inclines as an n-type semiconductor by certain doping. Our results open a new avenue for the modulation of the novel tetragonal ZnSe monolayer for a wealth of potential optoelectronic applications.Download high-res image (421KB)Download full-size image
Co-reporter:Hang Li, Songtao Lu, Yang Li, Wei Qin, Xiaohong Wu
Journal of Alloys and Compounds 2017 Volume 709(Volume 709) pp:
Publication Date(Web):30 June 2017
DOI:10.1016/j.jallcom.2017.03.084
•The substrate temperature greatly influenced the αs and ε of the prepared coating.•S-TiO2, TinO2n-1, (Mg and Zr)-Ti-O new phases were detected after the sputtering.•The αs and ε were regulated by temperature-selective sputtering of titanium oxide.•The wavelength inducing absorption depends on the atom reduced mass.The present work explores a magnetron sputtering route to deposit titanium oxide on MgO-ZrO2 plasma electrolytic oxidation (PEO) coating at different substrate temperatures for purpose of exploring crystallographic orientation and thermo-optical performance. By employing a Ti target as a sputtering cathode, the effects of the substrate temperature on the composition, lattice orientation, solar absorptance and infrared emittance of the prepared coatings were investigated. The XRD results indicated that the coating was composed of srilankite(S)-TiO2, Mg-Ti-O and Zr-Ti-O composite oxides, as well as Magnéli TinO2n-1 phases belonging to substoichiometric oxides of titanium. Furthermore, lattice and crystal preferable orientation were seen to be influenced by the substrate temperature. The reduction of the solar absorptance after the sputtering process was attributed to the high refractive index of titanium oxides. The infrared emittance was increased first and then decreased with the increase of the substrate temperature. This variation can be theoretically deduced from the lattice vibration theory. This method presents a promising application prospect in satisfying different thermo-optical design requirements of the spacecraft.Download high-res image (377KB)Download full-size image
Co-reporter:Yang Li;Hang Li;Qiyang Xiong;Xiaoming Wu;Jia Zhou;Jinzhu Wu;Wei Qin
Nanoscale (2009-Present) 2017 vol. 9(Issue 25) pp:8591-8599
Publication Date(Web):2017/06/29
DOI:10.1039/C7NR00127D
An environmentally friendly atomic layer deposition (ALD) method with excellent atomic scale roughness controllability is developed to fabricate a highly conformal, corrosion preventive and conducting Al doped ZnO (AZO) film on a plasma electrolytic oxidation (PEO) layer coated AZ31 magnesium alloy. Compared with the insulated PEO coated magnesium alloy, the electrical conductivity of the composite coating increases to 25 S m−1, and in the meantime the anticorrosion performance of the PEO/AZO coating is greatly improved compared to the bare Mg alloy. The enhanced electrical properties of the composite coating are due to the abundant oxygen deficiency in the AZO film generated during the ALD process. The improvement of the corrosion resistance is attributed to the changes in the bond angle and the distance between the surface coating molecule and adsorbent H2O molecule. As a result, the hydrophilic surface of PEO changes to the hydrophobic surface of AZO, providing a novel process to protect the surface of the magnesium alloy. It is believed that this technique may provide a novel and controllable strategy to expand the practical applications of magnesium alloys.
Co-reporter:Ming Wen;Hongping Wu;Xin Su;Juanjuan Lu;Zhihua Yang;Shilie Pan
Dalton Transactions 2017 vol. 46(Issue 15) pp:4968-4974
Publication Date(Web):2017/04/10
DOI:10.1039/C7DT00251C
Two alkali metal and alkaline-earth metal borates, ACaBO3 (A = Cs, Rb), were synthesized by a high temperature solution method. The powder SHG response of CsCaBO3 is approximately one time that of KH2PO4 (KDP), and its experimental band gap is 4.20 eV. The SHG density calculations indicate that the SHG effect originates from the synergistic effect of B–O and Ca–O groups. The two compounds crystallize in the cubic space group P213 and their structures feature a 3D framework composed of the CaO6 octahedra, the CsO9 polyhedra and the BO3 triangles. However, borates containing anisotropic planar BO3 triangles exhibit difficulty in forming an isotropic cubic structure. Through our investigation on all the ordered cubic structures with the BO3 or the B2O5 (composed of two BO3) groups, the MO6 octahedra play important role in their structure formations. This discovery is essential for the design of new cubic borates containing the BO3 triangles.
Co-reporter:Dequn Peng, Wei Qin, Xiaohong Wu
Polymer Degradation and Stability 2016 Volume 133() pp:211-218
Publication Date(Web):November 2016
DOI:10.1016/j.polymdegradstab.2016.08.011
Atomic oxygen (AO) in low Earth orbit (LEO) causes severe damages to the polymer materials used for the construction of spacecraft. To improve the AO resistance of cyanate ester (CE) which is ubiquitous in the space-structures, novel composites prepared by incorporating POSS, graphene and TiO2 (POSS-Graphene-TiO2, PGT) into CE matrix through a solution mixing method. The mass loss ratio of the resulting PGT/CE composites was significantly decreased in comparison to the pristine CE, which is due to the less surface damages. Chemical composition analysis shows that a surface passivation layer is formed on the PGT/CE composites upon exposure to the AO. Carbon fiber-reinforced PGT/CE composites (i.e., T700/PGT/CE) were fabricated. Compared with the T700/CE composite, the interlayer shear strength of the T700/PGT/CE composite was increased by 43% after the AO exposure. Our findings indicate that the PGT fillers contribute the improved AO resistance of the prepared carbon fiber/PGT/CE composites.
Co-reporter:Jinzhu Wu, Jun Dai, Yanbin Shao, Meiqi Cao and Xiaohong Wu
RSC Advances 2016 vol. 6(Issue 81) pp:77999-78007
Publication Date(Web):08 Aug 2016
DOI:10.1039/C6RA15074H
Molybdenum disulfide (MoS2) has emerged as a promising electrode material for supercapacitors. Elaboration of MoS2 with desired structures, morphologies and compositions as well as fabrication of MoS2-based hybrids are current research directions. Herein, we demonstrate engineering MoS2 with a multiphase structure including 2H and 1T phases as well as edge-rich nanospherical morphology via a hydrothermal route with the assistance of carbon dots (CDs) for the first time. The resultant MoS2 3D nanospheres are formed through the self-assembly of MoS2 2D nanosheets consisting of a few atomic layers stacked along the (002) direction with an enlarged interlayer spacing. The introduced CDs not only involve the growth of the few-layered multiphase MoS2 nanosheets but also mediate the formation of MoS2 nanospheres, whilst the residual CDs may intersperse onto the surfaces of MoS2 nanospheres. The novel MoS2 nanospheres-based electrode exhibits favorable electrochemical responses in an aqueous electrolyte, such as high specific capacitance (145 F g−1), good rate capability and excellent cyclic stability (90% capacity retention after 2000 cycles) owing to enhanced ionic intercalation and improved electrical conductivity associated with the specific structures and morphologies. This work would pave a new pathway through the structural, morphological and compositional design for improving the electrochemical properties of transition metal dichalcogenides (TMDs) applicable as alternative energy storage materials.
Co-reporter:Jia Zhou;Yang Li;Wei Qin
ChemPhysChem 2016 Volume 17( Issue 13) pp:1993-1998
Publication Date(Web):
DOI:10.1002/cphc.201600089
Abstract
The recently proposed three-atom-thick single-layer ZnSe sheet demonstrates a strong quantum confinement effect by exhibiting a large enhancement of band gap relative to the zinc blende (ZB) bulk phase. In this work, we aim at investigating the electronic and optical properties of this ultrathin tetragonal ZnSe single-layer sheet with various chalcogen dopant atoms, based on density functional theory (DFT). We find that these single-layer sheets with dopant atoms are still direct-band semiconductors with tunable band gaps, which can lead to strong light absorption and potential applications in solar energy harvesting. Theoretical optical absorbance results show that the S-doped ZnSe monolayer exhibits a higher absorption performance compared to other doped and undoped ZnSe monolayers. These findings pave a way for the modulation of novel ultrathin tetragonal ZnSe monolayers for a wealth of potential optoelectronic applications.
Co-reporter:Zan Li;Yang Li;Wei Qin
Journal of Materials Science: Materials in Electronics 2016 Volume 27( Issue 7) pp:6673-6680
Publication Date(Web):2016 July
DOI:10.1007/s10854-016-4614-2
AZO powders were sensitized through chemisorption method by octa-iso-pentyloxy phthalocyanine lead and characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The results showed that after sensitization process AZO photo physical properties improved greatly in visible regions. Photocatalytic degradation of methylene blue was studied under visible irradiation in aqueous solution and the pseudo first order model was used to obtain kinetic information of the photocatalytic degradation. The results indicated that photocatalytic activities of PbPc(iso-PeO)8-AZO were better than of AZO powders.
Co-reporter:Huanming Zhang, Chunling Zhu, Yujin Chen, Min Yang, Piaoping Yang, Xiaohong Wu, Lihong Qi and Fanna Meng
Journal of Materials Chemistry A 2015 vol. 3(Issue 4) pp:1421-1426
Publication Date(Web):27 Nov 2014
DOI:10.1039/C4TA05171H
A facile strategy was developed to fabricate net-like hematite nanoparticle/graphene oxide (GO) composite (NHG), in which the degree of oxidization of GO could be controlled by simply changing annealing time. NHG with GO of appropriate oxidization degree and content exhibited much higher photocatalytic activities than α-Fe2O3 nanorods and commercial α-Fe2O3.
Co-reporter:Huanhuan Wang, Songtao Lu, Yan Chen, Lu Han, Jia Zhou, Xiaohong Wu and Wei Qin
Journal of Materials Chemistry A 2015 vol. 3(Issue 47) pp:23677-23683
Publication Date(Web):15 Oct 2015
DOI:10.1039/C5TA06158J
Flexible lithium ion batteries with high energy density have recently received tremendous interest due to their potential applications in flexible electronic devices. Herein, we report a simple high energy ball-milling technique together with vacuum filtration to fabricate a highly flexible, conductive, robust and free-standing RGO/Co9S8 nanocomposite paper with high conductivity (121 S cm−1), tensile strength (50.4 MPa) and Young's modulus (3.5 GPa) which can be directly used as a free-standing anode for flexible LIBs without binders, conducting agents and metallic current collectors. The free-standing RGO/Co9S8 anode with a high mass active material loading of 66.7 wt% Co9S8 can deliver a high specific capacity of 1415 mA h gCo9S8−1 (944 mA h gelectrode−1) and maintain 573 mA h gCo9S8−1 (382.2 mA h gelectrode−1) after 500 cycles at a current density of 1C (1C = 545 mA g−1). More importantly, the rate capability was improved by introducing RGO. The RGO/Co9S8 anode exhibited impressive capacities of 1096.70 mA h gCo9S8−1 with a capacity recuperability of 69.4% as the current returned to 0.1C. These results demonstrate that the well designed nanocomposite is of great potential as an anode for flexible LIBs. As far as we know, such improved electrochemical performance can be attributed to the nanosized Co9S8 particles with a diameter of ∼25 nm homogeneously dispersed on the surface of high conductive graphene sheets that can be obtained owing to the milling impact stress, which enhances surface electrochemical reactivity and shortens the transport length of lithium ions and electrons. What's more, the large specific surface area of the graphene sheet enables the uniform distribution of Co9S8 and offers better ability to accommodate volume expansion/shrinkage of Co9S8 during repeated charge/discharge cycles.
Co-reporter:Li Zan, Qin Wei and Wu Xiaohong
RSC Advances 2015 vol. 5(Issue 69) pp:56325-56332
Publication Date(Web):19 Jun 2015
DOI:10.1039/C5RA06233K
A series of Al-doped ZnO (AZO) structures, including disk-like, flake-like, flower-like and dumbbell-like morphologies, have been synthesized by a hydrothermal method without any catalyst or template. The morphologies of these AZO structures can be conveniently controlled, by selecting the additives and controlling the experimental conditions, and the result has excellent reproducibility. Gas sensors based on AZO were fabricated and the gas sensing properties were investigated. The sensors showed high response values and reproducible response–recovery for 5–500 ppm ethanol at 332 °C, compared with NH3, CH3OH, H2, CO, HCHO, NOx and a specific mechanism was proposed.
Co-reporter:Dequn Peng, Wei Qin, Xiaohong Wu, Jinzhu wu and Yangyang Pan
RSC Advances 2015 vol. 5(Issue 94) pp:77138-77146
Publication Date(Web):28 Aug 2015
DOI:10.1039/C5RA11113G
Electron irradiation in outer space causes severe damage to the polymer materials of spacecrafts. An effective approach to prevent such damage is to incorporate nanoparticles into the polymeric materials. Herein, we fabricated modified cyanate ester (CE) and carbon/CE composites by the incorporation of reduced graphene oxide–TiO2 (rGO–TiO2) nanoparticles and studied their resistance performance to electronic radiation. Compared with the carbon/TiO2/CE composite, the interlayer shear strength of the resulting carbon/rGO–TiO2/CE composite increased by 10.4% and its mass loss reduced by 16.5%. Scanning electron microcopy (SEM) images showed that there are more cracks at the fiber and resin interfaces of carbon/CE than at the interfaces of carbon/rGO–TiO2/CE after irradiation. X-ray photoelectron spectroscopy (XPS) investigation showed that irradiation with 160 keV electrons could break the chemical bonds at the surface layer of the pristine CE resin, which is effectively prevented by the incorporation of rGO–TiO2 nanoparticles.
Co-reporter:Wei Qin, Baodong Fang, Songtao Lu, Zhida Wang, Yan Chen, Xiaohong Wu and Lu Han
RSC Advances 2015 vol. 5(Issue 17) pp:13153-13156
Publication Date(Web):19 Jan 2015
DOI:10.1039/C4RA15796F
A strategy of reinforced PPy wrapping over an acetylene black-coated sulfur composite (PPy–AB/S) was designed for synthesizing cathode materials of Li–S batteries with improved performance. It was found that the resulting PPy–AB/S cathodes were able to maintain 630 mA h g−1 even after 200 charge–discharge cycles at a rate of 0.5 C.
Co-reporter:Hang Li, Songtao Lu, Xiaohong Wu, Wei Qin
Surface and Coatings Technology 2015 Volume 269() pp:220-227
Publication Date(Web):15 May 2015
DOI:10.1016/j.surfcoat.2015.01.070
•Low αs/ε ratio thermal control coatings on Mg alloy were prepared by the PEO way.•The presence of Zr4 + ions greatly influenced the αs and ε of the PEO coating.•The coatings were mainly composed of MgO, t-ZrO2 and an Mg–O–Zr compound.The thermal control coatings with low absorbance–emissivity ratio were successfully fabricated on AZ31 Mg alloy by plasma electrolytic oxidation (PEO) technique. The influence of Zr(NO3)4 on the thermal control properties of the PEO coatings was studied in detail. The micro-structure, element distribution, phase and chemical composition of the prepared coatings were characterized by analytical techniques. The solar absorbance and emissivity of the coatings were respectively measured by a solar absorption/reflectometer and an ultraviolet–visible-near infrared spectrophotometer. The results revealed that the coatings were composed of MgO, t-ZrO2 and an Mg–O–Zr compound (Mg0.13Zr0.87O1.87), as well as some non-crystalline phosphorus. The EDS results showed the existence of Mg, O, Zr, P, Na and K elements on the porous coating with different shapes and sizes. The thickness, roughness and thermal control properties of the coatings were greatly affected by the content of Zr4 + ions in the electrolyte. When the concentration was 10 g/L, the coating possessed the lowest absorbance–emissivity ratio (about 0.46) and the maximum thickness. Herein, the solar absorbance was 0.405 and the emissivity reached 0.873. The thermal control coating obtained by this method will broaden the spatial application of Mg alloy.
Co-reporter:Yan Chen
The Journal of Physical Chemistry C 2015 Volume 119(Issue 19) pp:10288-10294
Publication Date(Web):April 27, 2015
DOI:10.1021/acs.jpcc.5b02596
Flexible lithium batteries with high energy density have recently received tremendous interest due to their potential applications in flexible electronic devices. Herein, we report a novel method to fabricate highly flexible and robust carbon nanotube–graphene/sulfur (CNTs–RGO/S) composite film as free-standing cathode for flexible Li/S batteries with increased capacity and significantly improved rate capability. The free-standing CNTs–RGO/S cathode was able to deliver a peak capacity of 911.5 mAh g–1sulfur (∼483 mAh g–1electrode) and maintain 771.8 mAh g–1sulfur after 100 charge–discharge cycles at 0.2C, indicating a capacity retention of 84.7%, which were both higher than the cathodes assembled without CNTs. Even after 100 cycles, the cathode showed a high tensile strength of 62.3 MPa. More importantly, the rate capability was improved by introducing CNTs. The CNTs–RGO/S cathode exhibited impressive capacities of 613.1 mAh g–1sulfur at 1C with a capacity recuperability of ∼94% as the current returned to 0.2C. These results demonstrate that the well-designed nanocomposites are of great potential as the cathode for flexible lithium sulfur (Li/S) batteries. Such improved electrochemical properties could be attributed to the unique coaxial architecture of the nanocomposite, in which the evenly dispersed CNTs enable electrodes with improved electrical conductivity and mechanical properties and better ability to avoid the aggregation and ensure the dispersive distribution of the sulfur species during the charge/discharge process.
Co-reporter:Wei Qin, Dequn Peng, Xiaohong Wu, Junhai Liao
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 2014 Volume 325() pp:115-119
Publication Date(Web):15 April 2014
DOI:10.1016/j.nimb.2014.01.022
TiO2 nano-particles were incorporated into cyanate ester (CE) resin to form TiO2/CE nano-composites. The effects of electron radiation on CE resin and on TiO2/CE nano-composites were investigated in a ground-based simulator that simulates space radiation conditions. Compared with CE resin, the addition of TiO2 nano-particles to the CE resin increased the bend strength and it improved the toughness before and after the electron radiation. The electron radiation damage mainly occurred in the CE resin matrix. The electric discharging resulted in the ablation of the CE resin surface when the charges were cumulated to a certain extent. The results of the mass loss and infrared (IR) experiments indicated that the electron irradiation in high vacuum broke the surface chemical bonds and that a cross-linking process occurred in the surface layer. The results of the electron paramagnetic resonance (EPR) showed that nano-TiO2 particles contribute a better resistance performance under 160-keV electron radiation.
Co-reporter:Wei Wang, Rui Wang, Wen Zhang, Lili Xing, Yanling Xu and Xiaohong Wu
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 34) pp:14347-14356
Publication Date(Web):17 Jun 2013
DOI:10.1039/C3CP51994E
First-principles theory was used to design a potassium-doped lithium niobate single crystal. The structural, electronic, optical and ferroelectric properties of the potassium-doped LiNbO3 single crystal model have been investigated using a generalized gradient approximation within density functional theory. It was found that substitution with potassium drastically changed the optical and electronic nature of the crystal and that the band gap slightly decreases. A series of LiNbO3 single crystals doped with x mol% K (x = 0, 3, 6, 9, 12 mol%) were successfully grown using the Czochralski method. The crystals were characterized using powder X-ray diffraction, UV-vis-infrared absorption spectroscopy and a ferroelectric property test. The experimental test results were consistent with the calculated predictions.
Co-reporter:Lili Xing, Yanling Xu, Rui Wang, Wei Xu, Shuo Gu, Xiaohong Wu
Chemical Physics Letters 2013 Volume 577() pp:53-57
Publication Date(Web):9 July 2013
DOI:10.1016/j.cplett.2013.05.050
•Controllable and white upconversion emissions are obtained.•Ideal white-light emissions can be obtained with pump power from 100 mW to 900 mW.•Energy transfer process of RE ions and pump power result in the color variation.•Great inspirations are given in realizing the target color of interest.Ho3+, Yb3+ and Tm3+ tri-doped LiNbO3 single crystals with various dopant concentrations were prepared by Czochralski method. Controllable and white upconversion emissions are generated under 980 nm excitation at room temperature. The variations of upconversion spectra and CIE coordinates with dopant concentrations and pump powers are studied in details on the basis of energy transfer processes. Ideal white-light emissions can be obtained even though the pump power is varied from 100 to 900 mW. Based on the present experiments, great inspirations are given in realizing the target color of interest by varying dopant concentrations and pump powers.
Co-reporter:Yunfei Qu;Rui Wang;Liang Liu;Jinchao Sun;Lili Xing;Ye Tao
Crystal Research and Technology 2013 Volume 48( Issue 12) pp:1031-1038
Publication Date(Web):
DOI:10.1002/crat.201300112
The effect of Yb3+ concentration on the fluorescence of 12CaO·7 Al2O3:Ho3+/Yb3+ polycrystals is investigated. The Raman spectra of pure C12A7 under 633-nm excitation show that the highest photon energy is 787.267 cm−1, which is not much bigger than general fluorides, so it can realize high efficiency upconversion. The upconversion emission spectra suggest that the green upconversion emission centered at 548 nm and the red upconversion emission at 662 nm correspond to the 5F4/5S25I8 and 5F55I8 transition of Ho3+ ions, respectively. The intensity of the upconversion luminescence and the ratio of red to green are changed with Yb3+ ion concentration. The pump dependence and luminescence decay dynamics spectra show the green and red upconversion emissions are populated by a two-photon process, and the upconversion mechanisms are analyzed. The relative luminous efficiencies of green and red emissions are 2.035% and 0.7%, respectively. The normalized efficiency obtained for green emission of Ho3+ at RT when the sample is excited by 980-nm light with an absorbed intensity of 7.5 W/cm2 is 0.27 cm2/W. This result is comparable to the values obtained in YF3 for the Yb3+, Er3+ green emission. The C12A7 with upconversion red and green light will be a promising luminous material.
Co-reporter:Wei Qin, Dequn Peng, Xiaohong Wu
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 2013 Volume 312() pp:126-130
Publication Date(Web):1 October 2013
DOI:10.1016/j.nimb.2013.07.017
The synergistic effects of electron and proton co-irradiation with an energy of 160 keV in ultrahigh vacuum environment on T700/cyanate composites was studied through examining the alteration of their interlayer shear strength (ILSS) and mass loss. The surface molecular structure and chemical composition of T700/cyanate composites before and after co-irradiation were studied by IR and XPS, respectively. The results indicate that under low co-irradiation fluence of less than 1.0 × 1016 e(p)/cm2, the cross-linking density of cyanate in the surface layer increased with fluence, resulting in increased ILSS of the composite. However a further increase in fluence caused the ILSS to decrease. Besides surface cross-linking, co-irradiation in high vacuum broke the surface chemical bonds. As a result, the mass loss and formation of a carbon-rich layer at thesurface of T700/cyanate composites took place.
Co-reporter:Songtao Lu, Wei Qin, Xiaohong Wu, Xiaodong Wang, Guimei Zhao
Materials Chemistry and Physics 2012 Volume 135(Issue 1) pp:58-62
Publication Date(Web):16 July 2012
DOI:10.1016/j.matchemphys.2012.04.015
This research investigates the effect of Fe2(SO4)3 on the thermal and optical properties of the ceramic coatings formed on AZ31 Mg alloy. The different ceramic coatings were obtained by plasma electrolytic oxidation (PEO) in electrolytes that contain varied concentrations of Fe2(SO4)3. The microstructure, element distribution, composition as well as the thermal and optical properties of the coatings were studied with scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray Diffraction (XRD), UV–VIS–NIR spectrophotometer and infrared reflectometer. The results show that all of the coatings prepared were mainly composed with MgO, with trace-amount of Fe3O4 presents and Fe seems entered into the MgO crystal structure. With the increasing of the concentration of Fe2(SO4)3, the solar absorptance and infrared emittance increased initially but then remain stable. We found that at the concentrations 8 g L−1, the coating has the highest solar absorptance (0.94) and infrared emittance (0.83). Our results show that coatings formed with this method could be useful as a thermal control coating in a variety of applications, such as in the spacecraft.Highlights► Thermal control coatings on AZ31 Mg alloy were prepared by the plasma electrolytic oxidation (PEO) method. ► The coatings were mainly composed with MgO, with trace-amount of Fe3O4 presents. ► The using of Fe3+ in the electrolyte improves the thermal and optical properties of the obtained MgO coating. ► The thermal control coating obtained by PEO has high solar absorptance (0.94) and infrared emittance (0.83).
Co-reporter:Xiaohong Wu, Qin Wei, Jiang Zhaohua
Thin Solid Films 2006 Volume 496(Issue 2) pp:288-292
Publication Date(Web):21 February 2006
DOI:10.1016/j.tsf.2005.08.354
Microporous titanium dioxide thin films have been fabricated on titanium plates by the micro-plasma oxidation method with the electrolyte of H2SO4. The influence of Fe3+ ions addition in the electrolyte on the photocatalytic activities was investigated. The results reveal that titanium dioxide thin films produced with Fe3+ addition electrolyte exhibit higher photoactivity than pure electrolyte for the oxidation of rhodamine B. The removal of rhodamine B reaches 90% for 30 min when Fe3+ addition concentrate is 0.2 g/L. Experimental results of X-ray diffraction and atom force microscopy show that the increase in activity is related to change in the lattice parameters and cell volume.
Co-reporter:Hang Li, Songtao Lu, Wei Qin, Lu Han, Xiaohong Wu
Acta Astronautica (November–December 2015) Volume 116() pp:126-131
Publication Date(Web):1 November 2015
DOI:10.1016/j.actaastro.2015.07.005
•Al-doped coating on AZ31 Mg alloy was prepared by plasma electrolytic oxidation.•PEO coating by Al doping improved the hardness and wear resistance of Mg alloy.•Wear mechanism of PEO coating at vacuum low-temperature is adhesion and abrasion.In this paper, Al-doped ceramic coatings with a thickness of 22–27 µm were prepared on AZ31 magnesium alloy by plasma electrolytic oxidation (PEO) in electrolytes that contain varied concentrations of NaAlO2, aiming to improve its wear resistance under vacuum low-temperature (−50 °C) condition. These obtained ceramic coating were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results show that the ceramic coatings with typical porous structure were mainly consisted of MgO and MgAl2O4 phases, indicating that the Al elements were participated into the coating during the PEO process. We found that at the concentrations 5 g/L NaAlO2, the coating has its highest surface hardness (6.2 GPa) and lowest friction coefficients (0.21) under vacuum low-temperature condition. Our results demonstrate that such PEO coatings are very promising to improve the wear properties under vacuum low-temperature condition.
Co-reporter:Dequn Peng, Wei Qin, Xiaohong Wu
Acta Astronautica (June–July 2015) Volume 111() pp:84-88
Publication Date(Web):1 June 2015
DOI:10.1016/j.actaastro.2015.02.004
•POSS–TiO2 organic–inorganic hybrid was synthesized and characterized.•The hybrid was incorporated into epoxy (EP) resin to form POSS–TiO2/EP nanocomposite.•The resistance to ultraviolet radiation of POSS–TiO2/EP was investigated.•The POSS–TiO2/EP exhibited excellent properties of anti-space ultraviolet radiation.Ultraviolet (UV) radiation is a severe space environmental factor, which is harmful to the durability of the polymeric materials of the spacecraft. For this reason, a novel POSS–TiO2/EP nanocomposite was synthesized by incorporating the POSS–TiO2 organic–inorganic hybrid into the epoxy (EP) resin. The effects of UV radiation on EP resin and on POSS–TiO2/EP nanocomposites were investigated in a ground-based simulator that simulates space radiation conditions. Compared with EP resin, the value of bend strength for 5.0 wt% POSS–TiO2/EP varied in a small range before and after UV radiation. Meanwhile, a typical tough feature was observed from the SEM photo for POSS–TiO2/EP nanocomposite after UV exposure. This result indicated that the POSS–TiO2/EP exhibited the excellent properties of anti-space ultraviolet radiation. The thermo gravimetric (TG) results showed that the addition of POSS–TiO2 improved the thermal-stability of EP resin matrix. The synthesized nanocomposites in this work could be used in the satellites to enhance their adaptability to the space environment and extend their service life.
Co-reporter:Hang Li, Songtao Lu, Wei Qin, Xiaohong Wu
Acta Astronautica (July 2017) Volume 136() pp:230-235
Publication Date(Web):1 July 2017
DOI:10.1016/j.actaastro.2017.03.021
•A thermal control coating with low αs and high ε on Mg alloy was prepared.•The participation of Zn ions greatly improved the ε of the PEO coating.•The coating was mainly composed of MgO and ZnO.Intense solar radiation and internal heat generation determine the equilibrium temperature of an in-orbit spacecraft. Thermal control coatings with low solar absorptance and high thermal emittance effectively maintain the thermal equilibrium within safe operating limits for exposed, miniaturized and highly integrated components. A novel ceramic coating with high thermal emittance and good adhesion was directly prepared on the Mg substrate using an economical process of controlled plasma electrolytic oxidation (PEO) in the electrolyte containing ZnSO4. XRD and XPS results showed that this coating was mainly composed of the MgO phase as well as an unusual ZnO crystalline phase. The adhesive strength between the coating and substrate determined by a pull-off test revealed an excellent adhesion. Thermal and optical properties test revealed that the coating exhibited a high infrared emittance of 0.88 (2–16 µm) and low solar absorptance of 0.35 (200–2500 nm). The result indicated that the formation of ZnO during the PEO process played an important role in the improvement of the coating emittance. The process developed provides a simple surface method for improving the thermal emittance of Mg alloy, which presents a promising application prospect in the thermal management of the spacecraft.
Co-reporter:Huanming Zhang, Chunling Zhu, Yujin Chen, Min Yang, Piaoping Yang, Xiaohong Wu, Lihong Qi and Fanna Meng
Journal of Materials Chemistry A 2015 - vol. 3(Issue 4) pp:NaN1426-1426
Publication Date(Web):2014/11/27
DOI:10.1039/C4TA05171H
A facile strategy was developed to fabricate net-like hematite nanoparticle/graphene oxide (GO) composite (NHG), in which the degree of oxidization of GO could be controlled by simply changing annealing time. NHG with GO of appropriate oxidization degree and content exhibited much higher photocatalytic activities than α-Fe2O3 nanorods and commercial α-Fe2O3.
Co-reporter:Jia Zhou and Xiaohong Wu
Journal of Materials Chemistry A 2017 - vol. 5(Issue 18) pp:NaN4510-4510
Publication Date(Web):2017/04/12
DOI:10.1039/C7TC00808B
The recently synthesized freestanding four-atom-thick double-layer sheet of ZnSe is a promising material for next-generation ultrathin optoelectronic nanodevices. In this theoretical work, we report two other novel double-layer sheets of ZnSe, with similar stability but distinct structures. These two new double-layer sheets of ZnSe could be considered by cutting along the wurtzite (WZ) bulk instead of the zinc blende (ZB) bulk. All these three layered sheets demonstrate a significantly strong quantum confinement effect, showing a large enhancement of the band gap compared with their three-dimensional (3D) bulks, by state-of-the-art calculations based on quasiparticle GW and the Bethe–Salpeter equation. Furthermore, the optical absorbance shows that the atomic arrangements of these three double-layer sheets of ZnSe play a significant role in the respective distinct photoabsorption behaviors, potentially important for a wealth of applications including solar water splitting.
Co-reporter:Ming Wen, Hongping Wu, Xin Su, Juanjuan Lu, Zhihua Yang, Xiaohong Wu and Shilie Pan
Dalton Transactions 2017 - vol. 46(Issue 15) pp:NaN4974-4974
Publication Date(Web):2017/03/09
DOI:10.1039/C7DT00251C
Two alkali metal and alkaline-earth metal borates, ACaBO3 (A = Cs, Rb), were synthesized by a high temperature solution method. The powder SHG response of CsCaBO3 is approximately one time that of KH2PO4 (KDP), and its experimental band gap is 4.20 eV. The SHG density calculations indicate that the SHG effect originates from the synergistic effect of B–O and Ca–O groups. The two compounds crystallize in the cubic space group P213 and their structures feature a 3D framework composed of the CaO6 octahedra, the CsO9 polyhedra and the BO3 triangles. However, borates containing anisotropic planar BO3 triangles exhibit difficulty in forming an isotropic cubic structure. Through our investigation on all the ordered cubic structures with the BO3 or the B2O5 (composed of two BO3) groups, the MO6 octahedra play important role in their structure formations. This discovery is essential for the design of new cubic borates containing the BO3 triangles.
Co-reporter:Huanhuan Wang, Songtao Lu, Yan Chen, Lu Han, Jia Zhou, Xiaohong Wu and Wei Qin
Journal of Materials Chemistry A 2015 - vol. 3(Issue 47) pp:NaN23683-23683
Publication Date(Web):2015/10/15
DOI:10.1039/C5TA06158J
Flexible lithium ion batteries with high energy density have recently received tremendous interest due to their potential applications in flexible electronic devices. Herein, we report a simple high energy ball-milling technique together with vacuum filtration to fabricate a highly flexible, conductive, robust and free-standing RGO/Co9S8 nanocomposite paper with high conductivity (121 S cm−1), tensile strength (50.4 MPa) and Young's modulus (3.5 GPa) which can be directly used as a free-standing anode for flexible LIBs without binders, conducting agents and metallic current collectors. The free-standing RGO/Co9S8 anode with a high mass active material loading of 66.7 wt% Co9S8 can deliver a high specific capacity of 1415 mA h gCo9S8−1 (944 mA h gelectrode−1) and maintain 573 mA h gCo9S8−1 (382.2 mA h gelectrode−1) after 500 cycles at a current density of 1C (1C = 545 mA g−1). More importantly, the rate capability was improved by introducing RGO. The RGO/Co9S8 anode exhibited impressive capacities of 1096.70 mA h gCo9S8−1 with a capacity recuperability of 69.4% as the current returned to 0.1C. These results demonstrate that the well designed nanocomposite is of great potential as an anode for flexible LIBs. As far as we know, such improved electrochemical performance can be attributed to the nanosized Co9S8 particles with a diameter of ∼25 nm homogeneously dispersed on the surface of high conductive graphene sheets that can be obtained owing to the milling impact stress, which enhances surface electrochemical reactivity and shortens the transport length of lithium ions and electrons. What's more, the large specific surface area of the graphene sheet enables the uniform distribution of Co9S8 and offers better ability to accommodate volume expansion/shrinkage of Co9S8 during repeated charge/discharge cycles.
Co-reporter:Yan Chen, Songtao Lu, Jia Zhou, Xiaohong Wu, Wei Qin, Ogechi Ogoke and Gang Wu
Journal of Materials Chemistry A 2017 - vol. 5(Issue 1) pp:NaN112-112
Publication Date(Web):2016/10/11
DOI:10.1039/C6TA08039A
Lithium sulfide (Li2S) has drawn special attention as a promising cathode material for emerging energy storage systems due to its high theoretical specific capacity and great compatibility with lithium metal-free anodes. However, Li2S cathodes urgently require a solution to increase their poor electrical conductivity and to suppress the dissolution of long-chain polysulfide (Li2Sn, 4 ≤ n ≤ 8) species into electrolyte. To this end, we report a free-standing Al2O3–Li2S–graphene oxide sponge (GS) composite cathode, in which ultrathin Al2O3 films are preferentially coated on Li2S by an atomic layer deposition (ALD) technique. As a result, a combination of high electron conductivity (from GS) and strong binding with Li2Sn (from ultrathin Al2O3 films) was designed for cathodes. The newly developed Al2O3–Li2S–GS cathodes are able to deliver a highly reversible capacity of 736 mA h gLi2S−1 (427 mA h gcathode−1) at 0.2C, which is much higher than that of corresponding cathodes without Al2O3 (59%). Also, the long-term cycling stability of Al2O3–Li2S–GS cathodes was demonstrated up to 300 cycles at 0.5C with an excellent capacity retention of 88%. In addition, combined with density functional theory calculations, the promotional mechanism of ultrathin Al2O3 films was elucidated using extensive characterization. The ultra-thin Al2O3 film with optimal thickness not only acts as a physical barrier to Li2S nanoparticles, but provides a strong binding interaction to suppress Li2Sn species dissolution.
Co-reporter:Wei Wang, Rui Wang, Wen Zhang, Lili Xing, Yanling Xu and Xiaohong Wu
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 34) pp:NaN14356-14356
Publication Date(Web):2013/06/17
DOI:10.1039/C3CP51994E
First-principles theory was used to design a potassium-doped lithium niobate single crystal. The structural, electronic, optical and ferroelectric properties of the potassium-doped LiNbO3 single crystal model have been investigated using a generalized gradient approximation within density functional theory. It was found that substitution with potassium drastically changed the optical and electronic nature of the crystal and that the band gap slightly decreases. A series of LiNbO3 single crystals doped with x mol% K (x = 0, 3, 6, 9, 12 mol%) were successfully grown using the Czochralski method. The crystals were characterized using powder X-ray diffraction, UV-vis-infrared absorption spectroscopy and a ferroelectric property test. The experimental test results were consistent with the calculated predictions.
