Jinglei Yang

Flexible polyurethane composites prepared by incorporation of polyethylenimine-modified slightly reduced graphene oxide

Co-reporter:Xiu-Zhi Tang, Chenzhong Mu, Wenyu Zhu, Xiaoli Yan, Xiao Hu, Jinglei Yang

Carbon 2016 Volume 98() pp:432-440

Publication Date(Web):March 2016

DOI:10.1016/j.carbon.2015.11.030

•Slightly reduced graphene oxide was functionalized by highly branched polyethylenimine (PEI) as a dual-role modifier to increase active sites on fillers and to act as antibacterial agent.•The flexible polyurethane film was obtained with highly enhanced mechanical properties and thermal stability, and excellent bacterial antiadhesive performance.•Surface chemistry and morphology of PU composites were studied and the high-density amine groups presented in the PEI chains is proposed to be the main reason for the desirable bacterial antiadhesive performance.Contributed by the highly reactive, antibacterial, and readily reducible polyethylenimine (PEI), polyurethane (PU) composites incorporated with slightly reduced graphene oxide (SRGO) modified with PEI (SRGO-PEI) were prepared by in situ polymerization. X-ray photoelectron spectroscopy confirmed that SRGO-PEI was only slightly reduced under mild reducing conditions, because the carbon-to-oxygen atomic ratios increased slightly, from 2.56 to 4.00. The Fourier transform infrared spectra and the results of X-ray diffraction indicated that the PEI on SRGO-PEI were not only covalently grafted but also intercalated into SRGO interlayers. The mechanical properties and thermal stability of PU/SRGO-PEI were highly enhanced because of the chemical bonds formed between SRGO-PEI and PU matrices. With the incorporation of 1.0-wt% SRGO-PEI, the elongation at break, tensile strength, and Young's modulus of PU/SRGO-PEI increased by 32.7%, 251.1%, and 172.7%, respectively. Moreover, the adhesion of bacteria on functionalized GO/PU composites was reported for the first time. The PU/SRGO-PEI composites exhibited enhanced bacterial antiadhesive property when compared with that of pure PU and PU/GO. This desirable antibacterial property of SRGO-PEI is proposed to be mainly contributed by the presence of high-density amine groups in the PEI chains.

Strengthening and failure mechanisms of individual carbon nanotube fibers under dynamic tensile loading

Co-reporter:Pengfei Wang, Xin Zhang, Reinack Varghese Hansen, Gengzhi Sun, He Zhang, Lianxi Zheng, T.X. Yu, Guoxing Lu, Jinglei Yang

Carbon 2016 Volume 102() pp:18-31

Publication Date(Web):June 2016

DOI:10.1016/j.carbon.2016.02.009

Rate-dependent mechanical properties of individual carbon nanotube (CNT) fibers are essential for developing advanced anti-collision composites. In this work, a free-falling Hopkinson tension bar was designed to measure the dynamic tensile strength of CNT fiber. The strength of pure CNT fiber is found to be more sensitive to strain rate than that of composite CNT fiber. The dynamic failure morphologies of pure and composite CNT fiber were compared with their quasi-static responses. It was observed that the pure CNT fiber tends to break off at the weakest point, leading to unraveling of fiber along the twisted direction. On the other hand, the infiltrated polymer tends to change the failure mode and rate sensitivity of CNT fibers. Furthermore, high speed deformation analysis under dynamic loading revealed that pure CNT fiber tends to fail at the weakest point while the composite CNT fiber breaks into several fragments.

Tuneable electrochromism in weavable carbon nanotube/polydiacetylene yarns

Co-reporter:Reinack Varghese Hansen, Li Zhong, Khiam Aik Khor, Lianxi Zheng, Jinglei Yang

Carbon 2016 Volume 106() pp:110-117

Publication Date(Web):September 2016

DOI:10.1016/j.carbon.2016.05.029

Weavable color-change materials are useful in smart textiles. Here we demonstrate static and programmable color change on flexible polydiacetylene (PDA) coated carbon nanotube (CNT) yarns through 3D hopping-conduction-induced electrochromism. The color change could be achieved using pre-patterning and further specified through defining the current paths. Mild heating before polymerization was used to gain control over the critical transition voltage and ZnO nanoparticles were introduced to anchor PDA and facilitate reversibility of the electrochromic transition. In-situ absorbance and Raman spectroscopy, Raman mapping and surface characterization with X-ray spectroscopy revealed that mild heating increased the critical transition voltage while PDA anchoring on ZnO improved the reversibility. The ability to tune CNT/PDA electrochromism through inexpensive structural alterations is promising for applications in smart textiles where complex patterns can be instantaneously realized and controlled with electrical stimulus.

Effects of nano-silica contents on the properties of epoxy nanocomposites and Ti-epoxy assembles

Co-reporter:Peigang He, Mingyue Huang, Bin Yu, Stephan Sprenger, Jinglei Yang

Composites Science and Technology 2016 Volume 129() pp:46-52

Publication Date(Web):6 June 2016

DOI:10.1016/j.compscitech.2016.04.014

In order to get a strong Ti-epoxy bond, nano-silica was added to epoxy as the reinforcement, and the effects of the presence of nano-silica on the properties of epoxy nanocomposites and Ti-epoxy assembles were investigated. The results showed that, although glass transition temperature of nanocomposites decreased with the increase in silica addition, mechanical properties of the nanocomposites such as flexural strength, fracture toughness, and hardness rose to the highest values when silica content was 15 wt%. However, the shear strength of the Ti-epoxy assemble was 45.38 MPa when the silica content was 2.5 wt%, from a low of 31.75 MPa for pure epoxy bonded assemble, increasing by 42.9%. With further increase in silica content, the shear strength decreased gradually. The remarkable increase in the shear strength with 2.5 wt% silica addition should be attributed to the improved wettability between epoxy and Ti surface, which resulted in much higher bonding strength between them.

Epigallocatechin gallate decorated carbon nanotube chemiresistors for ultrasensitive glucose detection

Co-reporter:Hari Krishna Salila Vijayalal Mohan, Reinack Hansen Varghese, Chee How Wong, Lianxi Zheng, Jinglei Yang

Organic Electronics 2016 Volume 28() pp:210-216

Publication Date(Web):January 2016

DOI:10.1016/j.orgel.2015.10.032

•Electronic detection of glucose using highly aligned CNT chemiresistors.•Reaction between EGCG and H2O2 forms the basis of sensing.•EGCG-CNT capable of detecting glucose in low concentrations (10 nM to 1 μM).•Results bode well for bloodless glucose detection.The concentration of glucose in biological fluids is in the micromolar range, the detection of which requires devices with high sensitivity and low limit of detection (LOD). Here, we report the real-time electronic detection of glucose using an antioxidant found in green tea, namely, epigallocatechin gallate (EGCG), decorated on carbon nanotubes (CNTs) and tested in a chemiresistor configuration. The detection principle relies on the spontaneous reaction of EGCG with hydrogen peroxide, a reactive oxygen species released during glucose oxidation, which is translated electrically as a change in CNT conductance. Our results suggest that the response of EGCG decorated CNTs was far superior to that of the bare CNT based device. The sensor detected glucose ranging from 10 nM to 1 μM with LOD of ∼8.7 nM, which is much lower than the commercially available finger-pricking based glucose sensors. This could pave the way for developing simple resistivity-based sensors capable of glucose detection in biological fluids other than blood, such as sweat and saliva.We report the detection of glucose at very low concentrations by using aligned CNTs coated with EGCG in a chemiresistor configuration. The low limit of detection and high selectivity towards glucose bodes well for blood-less glucose detection.

Water resistant reactive microcapsules for self-healing coatings in harsh environments

Co-reporter:Dawei Sun, He Zhang, Xiu-Zhi Tang, Jinglei Yang

Polymer 2016 Volume 91() pp:33-40

Publication Date(Web):17 May 2016

DOI:10.1016/j.polymer.2016.03.044

•Double-shelled microcapsules were synthesized via shortened in-situ polymerization.•Resultant capsules showed excellent survivability in various aqueous solutions.•Fresh/Treated capsules in coating can self heal scratch after soaking in salt water.Double-shelled microcapsules containing liquid 4,4′-bis-methylene cyclohexane diisocyanate (HMDI) with outstanding water resistance are successfully synthesized via combination of interfacial and in-situ polymerization reactions in an oil-in-water emulsion. The diameter and shell thickness of microcapsules increased under lower agitation rate. The relative residue of core content of microcapsules remains more than 90% after 24 days in both ambient open air and water. Manually scratched polymer coatings with both fresh and conditioned microcapsules showed satisfactory anticorrosion performance in salt water via self-healing functionality. In addition, self-healing coatings with fresh microcapsules after immersion in ambient water for 30 days still possessed superior anticorrosion performance.

Tribological behaviors of binary and ternary epoxy composites functionalized with different microcapsules and reinforced by short carbon fibers

Co-reporter:N.W. Khun, H. Zhang, D.W. Sun, J.L. Yang

Wear 2016 s 350–351() pp: 89-98

Publication Date(Web):15 March 2016

DOI:10.1016/j.wear.2016.01.007

Double-layered reactive microcapsules with excellent thermal and non-polar solvent resistance for self-healing coatings

Co-reporter:Dawei Sun, Jinliang An, Gang Wu and Jinglei Yang

Journal of Materials Chemistry A 2015 vol. 3(Issue 8) pp:4435-4444

Publication Date(Web):06 Jan 2015

DOI:10.1039/C4TA05339G

Double-layered polyurea microcapsules containing hexamethylene diisocyanate (HDI) with outstanding shell tightness have been successfully synthesized via interfacial polymerization reaction in an oil-in-water emulsion. The resultant capsules were systematically characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. The reaction parameters including reaction temperature (40 °C, 50 °C, 60 °C), reaction duration (1 h, 1.5 h, 2 h and 2.5 h), amount of Suprasec 2644 (2.4 g, 3 g and 3.6 g) and emulsification time (15 min, 45 min and 75 min) were investigated and evaluated in terms of core fraction and quality of microcapsules. The core fraction of microcapsules was reduced with an increase of reaction temperature, reaction duration, mass of Suprasec 2644 and emulsification time, while the quality of microcapsules fluctuated. The thermal and organic solvent resistances were assessed by using TGA and titration. The results showed that the microcapsules had 1.6% weight loss compared with pure HDI with 90% weight loss after 60 min isothermal treatment at 100 °C. After immersion in various solvents for 24 days, the microcapsules released as low as ∼3% of core in weakly polar solvents (i.e. hexane and xylene), about 5–60% in polar aprotic solvents (i.e. ethyl acetate, acetone, DMF and DMSO), and 60–90% in water and polar protic solvents (i.e. isopropanol and ethylene glycol). Both fresh and hexane-treated HDI capsules showed excellent anticorrosion performance in scratched coatings via self-healing functionality, indicating promising practical application in industrial coating and paint systems.

Polyvinylpyrrolidone-stabilized magnetic nickel nanochains for cancer hyperthermia and catalysis applications

Co-reporter:Jian Wu, Wei Zhou, Qingmei Cheng and Jinglei Yang

RSC Advances 2015 vol. 5(Issue 29) pp:22965-22971

Publication Date(Web):23 Feb 2015

DOI:10.1039/C4RA10545A

In this study, we report a novel polyvinylpyrrolidone-stabilized magnetic nickel nanochain (Ni-NC@PVP) using a simple solvothermal method for potential cancer hyperthermia and catalytic applications. The water-soluble Ni-NC@PVP exhibits excellent magnetic hyperthermia properties and low toxicity. In order to investigate the apoptotic hyperthermia efficacy of Ni-NC@PVP in skin cancer cells, we also explore the interaction of Ni-NC@PVP with cancer cells, which exhibits excellent antitumor efficacy on B16 cells. In addition, as a magnetically separable catalyst, it also shows excellent catalytic activity and durability for the selective hydrogenation of acetophenone to 1-phenylethanol. The enhanced performance demonstrates the possibility for designing new multifunctional nanomaterial with improved performances for biomedical therapies and green catalysis.

Improved chemical stability of silver by selective distribution of silver particles on reduced graphene oxide nanosheets

Co-reporter:Xiu-Zhi Tang, Xuelong Chen, Gang Wu, Xiao Hu and Jinglei Yang

RSC Advances 2015 vol. 5(Issue 61) pp:49257-49262

Publication Date(Web):26 May 2015

DOI:10.1039/C5RA04508H

The chemical stability of particles on reduced graphene oxide (RGO) nanosheets is an important issue for the RGO/particles hybrid materials. Here we report that the chemical stability of environmentally sensitive silver can be significantly improved by controlling the distribution of silver particles on RGO nanosheets. By switching the sequence of “deoxygenation” and “deposition”, two kinds of RGO/silver hybrids are prepared. The structure and chemical state of silver particles on RGO are investigated by X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis, ultraviolet-visible spectroscopy, Raman spectra, transmission electron microscopy and scanning electron microscope. It is found that the graphene/Ag hybrid prepared by “deposition” and then “deoxygenation” can still exhibit obvious surface enhanced Raman scattering (SERS) signals after 10-month storage, compared with the hybrid material fabricated in inverse order. The selective distribution of silver particles and non-uniform dispersion of electrons on RGO nanosheets are responsible for the different performances. This study provides a new insight into preparing chemically stable RGO/particle hybrid materials.

Surface modifications of Ti alloy with tunable hierarchical structures and chemistry for improved metal–polymer interface used in deepwater composite riser

Co-reporter:Peigang He, Ke Chen, Jinglei Yang

Applied Surface Science 2015 Volume 328() pp:614-622

Publication Date(Web):15 February 2015

DOI:10.1016/j.apsusc.2014.12.081

Highlights

•: Nano to macro size hierarchical structures were formed on Ti6Al4V alloy by different surface treatments.
•: Valence state of the Ti ion together with the hierarchical strcture of the oxide layer determined the wetting dynamics of epoxy to the treated Ti6Al4V alloy.
•: Shear strengths of Ti-epoxy assembled specimens depend on the interfacial bonding states of both epoxy-oxide layer and oxide-Ti substrate.

Grafting Low Contents of Branched Polyethylenimine onto Carbon Fibers to Effectively Improve Their Interfacial Shear Strength with an Epoxy Matrix

Co-reporter:Xiu-Zhi Tang;Bin Yu;Reinack Varghese Hansen;Xuelong Chen;Xiao Hu

Advanced Materials Interfaces 2015 Volume 2( Issue 12) pp:

Publication Date(Web):

DOI:10.1002/admi.201500122

The mechanical properties of carbon fiber (CF) reinforced composites are greatly dependent on the interfacial strength between the CFs and matrix. To improve the interfacial adhesion of carbon fiber/epoxy composites, branched polyethylenimine (PEI) is grafted onto the CFs treated in a mixed acid at optimized process time. The chemical compositions and bonds of functionalized CFs are characterized by thermal gravimetric analysis, Fourier-transform infrared, and X-ray photoelectron spectroscopy. The surface structures and morphologies of various CFs are analyzed by Raman spectroscopy and scanning electron microscopy, respectively. Microbond test is adopted to evaluate the interfacial shear strength (IFSS) between the CFs and epoxy matrix. The results show that the CFs modified by low molecular weight PEI are better than those modified by high molecular weight PEI. The IFSS of PEI modified CFs can reach a maximum of 107.2 ± 14.3 MPa at a low functionalization degree compared with 78.1 ± 11.6 MPa of unmodified CFs. The branched structure and high density of active amine groups on the PEI chains are responsible for the improved interfacial strength.

Salicylideneanilines encapsulated mesoporous silica functionalized gold nanoparticles: a low temperature calibrated fluorescent thermometer

Co-reporter:Jian Wu, Qingmei Cheng, Wei Zhou, Zhihong Wei and Jinglei Yang

RSC Advances 2015 vol. 5(Issue 94) pp:77056-77061

Publication Date(Web):28 Aug 2015

DOI:10.1039/C5RA09626J

In this study, a novel temperature responsive fluorescent sensor, 4-(2-hydroxybenzylideneamino)benzoic acid (HBA), encapsulated in the nanochannels of mesoporous silica functionalized with gold nanoparticles (GMS) was synthesized and studied. The fluorescence intensity of HBA–GMS showed excellent linear temperature sensitivity over a wide range, from cryogenic to room temperature (100–298 K). Meanwhile, GMS was used as an immobilization matrix to improve light harvesting and calibrate the HBA fluorescence intensity at different temperatures because of the stable and insensitive fluorescence signal of the gold nanoparticle intercalated into the walls of GMS. In addition, it was found that HBA–GMS exhibits excellent biocompatibility and low toxicity for cellular imaging due to the robust GMS support. These results suggest that the assembled mesostructure provides a promising, intelligent, and calibrated fluorescent thermometer with potential applications as a sensor and in cryogenic bio-detection and therapy fields.

Effects of primer and annealing treatments on the shear strength between anodized Ti6Al4V and epoxy

Co-reporter:Peigang He, Mingyue Huang, Stefan Fisher, Chee Yoon Yue, Jinglei Yang

International Journal of Adhesion and Adhesives 2015 Volume 57() pp:49-56

Publication Date(Web):March 2015

DOI:10.1016/j.ijadhadh.2014.10.004

The effects of primer and annealing treatments on the shear strength between anodized Ti6Al4V and epoxy were investigated. Primer coating improved the shear strength between anodized Ti alloy and epoxy by up to 81.3% using concurrent curing compared with that of control specimens. After annealing of anodized Ti alloy and applying primer, the shear strength of the specimen was further increased by 6.4% due to the formation of stable TiO2 transferred from TiO in the anodization process. SEM analysis revealed the specimen without primer and annealing treatments showed adhesive failure between epoxy–alloy interface and discontinuous cohesive failure of epoxy. Primer coating initiated a new interfacial failure mode between the oxide layer and alloy due to the improved bonding strength between epoxy and oxide layer. In addition, annealing and primer treatments generated large tracts of epoxy continuous cohesive failure, showing good agreement with its higher shear strength and work of fracture.

On the study of electrochromism in multiwalled carbon nanotube–polydiacetylene composites

Co-reporter:Reinack Varghese Hansen, Mingyue Huang, Zhaoyao Zhan, Gengzhi Sun, Jinglei Yang, Lianxi Zheng

Carbon 2015 90() pp: 222-230

Publication Date(Web):August 2015

DOI:10.1016/j.carbon.2015.04.027

Multiwalled carbon nanotubes (MWCNTs) have been shown to induce electrochromism in polydiacetylene (PDA) formed from the diacetylene monomer 10,12-petacosadiynoic acid (PCDA). This study investigates changes in the backbone of both partially and highly polymerized 10,12-PCDA monomers brought about by the unique electrical transport of underlying MWCNT sheets. The real time variation in absorbance with voltage revealed a clear transition from the blue to red state in both types of composites, but the Raman peaks responded differently: Raman peaks from carbon double and triple bonds in PDA did not shift under current flow in the partially polymerized composites but shifted by 21.75 and 17.85 cm−1 respectively, in the highly polymerized composites. These results suggest that stress in the PDA backbone was not crucial for forming the red phase when electrical stimulus was involved. Polarized Raman experiments revealed significant alignment changes in the composites as a result of current flow. It is proposed that a widening of PDA band gap due to π-orbital de-stacking is the principle behind electrically induced blue to red transition in MWCNT–PDA composites.

Long-term moisture effects on the interfacial shear strength between surface treated carbon fiber and epoxy matrix

Co-reporter:Bin Yu, Zhenyu Jiang, Jinglei Yang

Composites Part A: Applied Science and Manufacturing 2015 Volume 78() pp:311-317

Publication Date(Web):November 2015

DOI:10.1016/j.compositesa.2015.08.027

In recent years, carbon fiber reinforced polymer (CFRP) composites have found increasing applications in marine and offshore area, where the CFRP components are subjected to a persistent attack of moisture. The performance degradation of composites under those critical service conditions becomes a key issue. In this work, silane coating and multiwalled carbon nanotubes were applied on carbon fibers to enhance the fiber/matrix interfacial bonding strength. The long-term effects of moisture on the interfacial shear strength (IFSS) of the composites in underwater environments, such as de-ionized water and simulated seawater, have been studied using single fiber microbond method. The silane coating and carbon nanotube-modified silane coating are found to contribute 14.5% and 26.3% increase in IFSS of the CFRP in dry air, and well maintain this improvement during a 120-day immersion test in de-ionized water and simulated seawater.

Improvement of impact-resistant property of glass fiber-reinforced composites by carbon nanotube-modified epoxy and pre-stretched fiber fabrics

Co-reporter:Pengfei Wang;Xin Zhang;Guohui Lim;Haosiang Neo

Journal of Materials Science 2015 Volume 50( Issue 18) pp:5978-5992

Publication Date(Web):2015 September

DOI:10.1007/s10853-015-9145-3

Glass fiber-reinforced plastic composites (GFRPs) are often suffered to impact loadings; it is essential to improve its damage-resistant properties and understand the energy absorption mechanisms. In this work, the low-velocity impact behaviors of GFRPs were investigated in consideration of epoxy resins modified with 0, 0.4, and 0.75 % multi-walled carbon nanotubes (MWCNTs) by weight content and pre-stretched fabric at 0, 1.27, and 2.47 kg weight. In comparison with pure GFRPs sample, MWCNT-modified specimens are effective in improving the impact resistance under impact energies at 9, 16, and 22 J in terms of reduced damage factor and enhanced perforation threshold. Microscopic fractographic analysis indicated that the incorporation of MWCNTs in epoxy matrix offered additional mechanisms through breakage, bridging, and pull-out of carbon nanotubes to favor load transfer effect, prevent crack propagation, and thus dissipate more energy. The dynamic thermo-mechanical analysis proved that MWCNTs improved the storage modulus and glass transition temperature of the composites. In addition, the pre-stretched GFRP composites showed more impact resistant than the non-stretched ones through instant load transfer effect.

A Versatile Approach towards Multifunctional Robust Microcapsules with Tunable, Restorable, and Solvent-Proof Superhydrophobicity for Self-Healing and Self-Cleaning Coatings

Co-reporter:Gang Wu;Jinliang An;Xiu-Zhi Tang;Yong Xiang

Advanced Functional Materials 2014 Volume 24( Issue 43) pp:6751-6761

Publication Date(Web):

DOI:10.1002/adfm.201401473

Numerous microencapsulation techniques have been developed to encase various chemicals, for which specific processing parameters are required to address the widely differing features of the encapsulated materials. Microencapsulation of reactive agents is a powerful technique that has been extensively applied to self-healing materials. However, the poor solvent compatibility and insufficient thermal stability of microcapsules continue to pose challenges for long-term storage, processing, and service in practical applications. Here, an easily modifiable and highly versatile method is reported for preparing various chemicals filled poly(urea-formaldehyde) microcapsules that exhibit superior tightness against solvents and heat and that possess widely tunable, repetitiously self-restorable, and solvent-proof superhydrophobicity. In addition, the low-cost fabrication of biomimetic multifunctional smart coatings is demonstrated for self-healing anticorrosion and self-cleaning antifouling applications by directly dispersing the superhydrophobic microcapsules into and onto a polymer matrix. The methodology presented in this study should inspire the development of multifunctional intelligent materials for applications in related fields.

Robust microcapsules with polyurea/silica hybrid shell for one-part self-healing anticorrosion coatings

Co-reporter:Gang Wu, Jinliang An, Dawei Sun, Xiuzhi Tang, Yong Xiang and Jinglei Yang

Journal of Materials Chemistry A 2014 vol. 2(Issue 30) pp:11614-11620

Publication Date(Web):18 Apr 2014

DOI:10.1039/C4TA01312C

Silica/polyurea hybrid microcapsules loaded with hexamethylene diisocyanate (HDI) as core materials were prepared via a combined strategy of interfacial polymerization and an in situ sol–gel process in an oil-in-water emulsion. They were clearly characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The resultant microcapsules have diameters of 57–328 μm, shell thicknesses of 1–8 μm, and core fractions of 51.2–65.6%. The diameter and shell thickness were linearly related to the agitation rate in the double logarithm coordinates, and the core fraction were linearly related to the agitation rate, indicating that the structure and component of the microcapsules can be controlled effectively. The resistant properties against thermal and solvent attacks were assessed by using thermogravimetric analysis and titration. The results show that the microcapsules had outstanding thermal stability with initial evaporation temperature (defined at 5% of weight loss), increased by around 58 °C compared with that of pure core material, and good resistance to xylene with less than 25.9 ± 0.7 wt% reduction of core content after immersion for 100 h. Self-healing anticorrosion coatings based on microcapsules were fabricated on a steel substrate. Preliminary results indicated significant corrosion retardancy occurred in the coatings under an accelerated corrosion process, showing the great potential of our microcapsules in the development of catalyst-free, one-part, self-healing coatings for corrosion control.

Enhanced interphase between epoxy matrix and carbon fiber with carbon nanotube-modified silane coating

Co-reporter:Bin Yu, Zhenyu Jiang, Xiu-Zhi Tang, Chee Yoon Yue, Jinglei Yang

Composites Science and Technology 2014 Volume 99() pp:131-140

Publication Date(Web):30 July 2014

DOI:10.1016/j.compscitech.2014.05.021

Multiwalled carbon nanotubes are incorporated into the silane coating on fiber surface to enhance the interfacial bonding of carbon fiber reinforced epoxy composite. The results of microbond tests show that the interfacial shear strength of the prepared hybrid composites can be significantly increased by up to 26.3% compared with that of common composite. In contrast, the addition of carbon nanotubes into epoxy matrix demonstrates a distinctly weaker effect on enhancing the interphase between neat silane coated carbon fiber and matrix. This discrepancy can be attributed to the densification of CNT forest within the interphase during the forming of nanocomposite coating. Based on our experimental study, the carbon nanotube-based modification of silane coating on fiber surface is considered as a more efficient approach than the widely reported carbon nanotube-based tuning of matrix for hybrid composites, at the aspects of reinforcing effect, cost saving and process complexity.

Salt spray and EIS studies on HDI microcapsule-based self-healing anticorrosive coatings

Co-reporter:Mingxing Huang, Jinglei Yang

Progress in Organic Coatings 2014 Volume 77(Issue 1) pp:168-175

Publication Date(Web):January 2014

DOI:10.1016/j.porgcoat.2013.09.002

•Systematical study on HDI microcapsule based self-healing anticorrosive coatings.•Optimal formulation of HDI microcapsule in coatings with best corrosion protection.•Kinetic analysis of corrosion-healing process in the formulated coatings.•Simplified statistical model established to explain the scratch-sealing mechanism.Anticorrosive property of hexamethylene diisocyanate microcapsule-based self-healing coatings was systematically investigated by salt spray and EIS measurements. The influences of microcapsule diameter, weight fraction and coating thickness on the anticorrosive performance of the scratched samples were studied under salt spray condition, which revealed the thicker coatings with larger microcapsules at 10 wt.% demonstrated the best anticorrosion behavior. Additionally, the kinetics of self-healing process characterized by EIS measurement was parametrically analyzed in an equivalent circuit when the scratched coating was exposed to salt solution. A simplified model was established to explain the influences of these factors with consideration of scratch dimension.

Fabrication and characterization of mini alumina ceramic turbine rotor using a tailored gelcasting process

Co-reporter:Mingyue Huang, Peigang He, Jinglei Yang, Fei Duan, Seng Chuan Lim, Mee Sin Yip

Ceramics International 2014 Volume 40(Issue 6) pp:7711-7722

Publication Date(Web):July 2014

DOI:10.1016/j.ceramint.2013.12.112

A mini alumina ceramic turbine rotor has been successfully fabricated using a tailored colloidal process based on gelcasting technology. A specialized forming, drying and sintering approach was developed for the complex-shaped component with both large volume (90 mm in diameter and 20 mm in height) and submillimeter geometry (0.42 mm at the blade tip with curvature), to assure a highly dense product without warpage and cracks. The effects of solid content and temperature on the rheological behaviors of the prepared slurry were investigated to identify the best pourability. A novel approach using radius of curvature and overlapped area was adopted to compare the blade contour similarity under different sintering strategies and solid contents. In addition, the different physical and mechanical properties between main body and blade regions were discussed and their microstructures were analyzed. The preparation route for highly dense alumina rotor with minimum contour distortion was finally summarized.

Impact Behaviour of GLAREs with MWCNT Modified Epoxy Resins

Co-reporter:H. Zhang;S. W. Gn;J. An;Y. Xiang;J. L. Yang

Experimental Mechanics 2014 Volume 54( Issue 1) pp:83-93

Publication Date(Web):2014 January

DOI:10.1007/s11340-013-9724-7

In this study, GLAREs (Glass Reinforced Aluminum Laminates) with 3/2 configuration were fabricated in-house with multi-walled carbon nanotubes (MWCNTs) modified epoxy resins. Uniform dispersion of MWCNTs in epoxy resin was achieved via a two-step dispersion method with concentration up to 2.0 wt%. The influence of MWCNTs on the flexural property and the impact performance of GLAREs was investigated through the three-point bending and drop weight Dynatup impact testings, respectively. The incorporation of MWCNTs into epoxy evidently improved the flexural strength and modulus. In comparison with pure epoxy bonded GLARE, the modified GLAREs generally showed improvement of impact resistance. The improvement was more obvious at low concentration of MWCNT due to better dispersion of nanotubes in the resin and reasonable wettability of glass fibres and aluminium to the modified resin. Diversified failure mechanisms including plastic deformation and rupture of metal layers, breakage of fibres and matrix, delamination between composite and metal layers, and delamination between composite plies were observed. In addition, debonding, pull-out, and bridging effects of carbon nanotubes were observed, which proved the contribution of MWCNTs to the improved impact resistance of the modified GLAREs.

Tribological properties of short carbon fibers reinforced epoxy composites

Co-reporter:Nay Win Khun;He Zhang;Lee Hoon Lim;Chee Yoon Yue;Xiao Hu

Friction 2014 Volume 2( Issue 3) pp:226-239

Publication Date(Web):2014 September

DOI:10.1007/s40544-014-0043-5

Short carbon fiber (SCF) reinforced epoxy composites with different SCF contents were developed to investigate their tribological properties. The friction coefficient and wear of the epoxy composites slid in a circular path against a steel pin inclined at 45° to a vertical axis and a steel ball significantly decreased with increased SCF content due to the solid lubricating effect of SCFs along with the improved mechanical strength of the composites. The scanning electron microscope (SEM) observation showed that the epoxy composites had less sensitive to surface fatigue caused by the repeated sliding of the counterparts than the epoxy. The tribological results clearly showed that the incorporation of SCFs was an effective way to improve the tribological properties of the epoxy composites.

Wear resistant epoxy composites with diisocyanate-based self-healing functionality

Co-reporter:N.W. Khun, D.W. Sun, M.X. Huang, J.L. Yang, C.Y. Yue

Wear 2014 Volume 313(1–2) pp:19-28

Publication Date(Web):15 May 2014

DOI:10.1016/j.wear.2014.02.011

•Study investigates the sliding wear of HDI based self-healing epoxies.•Released liquid HDI slightly lowers friction due to its lubricating effect.•High capsule content greatly reduces wear due to self-healing of released HDI.Hexamethylene diisocyanate (HDI) filled microcapsules were developed and incorporated in epoxy matrices to form a new type of wear resistant epoxy composites. The tribological properties of the epoxy composites were systemically investigated. The friction and wear of the composites slid against a Cr6 steel ball at different sliding speeds under various normal loads decreased with increased microcapsule content because of the lubricating effect of released HDI liquid from ruptured microcapsules during the wear test and the self-healing process of the released HDI liquid with the moisture to form new polyurea layers on the wear track. It can be concluded that the incorporation of microencapsulated HDI liquid is an effective way to lessen the wear of the epoxy composites during sliding via the self-healing process with a concurrent self-lubricating effect of the released HDI liquid.Wear-healing kinetics of epoxy under sliding wear loading condition.

Etched glass bubbles as robust micro-containers for self-healing materials

Co-reporter:He Zhang and Jinglei Yang

Journal of Materials Chemistry A 2013 vol. 1(Issue 41) pp:12715-12720

Publication Date(Web):03 Sep 2013

DOI:10.1039/C3TA13227G

Etched glass bubbles (GBs) with through-holes at the micron level were fabricated by etching them using dilute hydrofluoric acid (HF) in a specially designed mixer. The semi-segmented mixer under mechanical agitation produces circulation of the GBs in solution, purposely completing the processes of the etching reaction on the GBs, filling the etched GBs with solution, and depositing the well etched GBs in the mixer bottom for collection. Highly reactive primary amine and diisocyanate monomer were separately infiltrated into the etched GBs and formulated as self-healing materials with satisfactory healing performance, indicating the robustness and versatility of the etched GBs.

Mechanical and tribological properties of epoxy matrix composites modified with microencapsulated mixture of wax lubricant and multi-walled carbon nanotubes

Co-reporter:Nay Win Khun;He Zhang;Erjia Liu

Friction 2013 Volume 1( Issue 4) pp:341-349

Publication Date(Web):2013 December

DOI:10.1007/s40544-013-0028-9

The mechanical and tribological properties of epoxy composites modified with microencapsulated wax lubricant and multi-walled carbon nanotubes (MWCNTs) were investigated. The increased soft microcapsules embedded in the epoxy matrices were responsible for the reduced micro-hardness and Young’s modulus of the epoxy composites. It was found that the friction of the epoxy composites greatly decreased with increased microcapsule content due to combined lubricating effects of the both wax lubricant and MWCNTs. As a result, the wear of the epoxy composites apparently decreased with increased microcapsule content.

Facile microencapsulation of HDI for self-healing anticorrosion coatings

Co-reporter:Mingxing Huang and Jinglei Yang

Journal of Materials Chemistry A 2011 vol. 21(Issue 30) pp:11123-11130

Publication Date(Web):30 Jun 2011

DOI:10.1039/C1JM10794A

Polyurethane (PU) microcapsules containing hexamethylene diisocyanate (HDI) as core materials are facilely manufactured via interfacial polymerization reaction of commercial methylene diphenyl diisocyanate (MDI) prepolymer and 1,4-butanediol in an oil-in-water emulsion. The resultant capsules have diameters of 5–350 μm and shell thickness of 1–15 μm, both linearly related to the agitation rate in the double logarithm coordinates. The typical core fraction of microcapsules and the yield of synthesis are around 60 wt% and 70 wt%, respectively, while varying with reaction conditions. The effects of parameters including reaction duration and temperature, surfactant concentration, agitation rate, and environmental factors on the formation of microcapsules were systematically investigated and optimized. Quality assessments of each batch of microcapsules were performed using thermogravimetric analysis and scanning electron microscopy. Anticorrosion coatings mixed with synthesized microcapsules were prepared on a steel substrate. Preliminary results indicated significant corrosion retardancy happened in the self-healing coatings under an accelerated corrosion process, showing the great potential of this facile microencapsulation technique in development of catalyst-free, one-part self-healing coatings for corrosion control.

Enhanced fracture toughness of carbon fabric/epoxy laminates with pristine and functionalized stacked-cup carbon nanofibers

Co-reporter:Pengfei Wang, Wanshuang Liu, Xin Zhang, Xuehong Lu, Jinglei Yang

Engineering Fracture Mechanics (November 2015) Volume 148() pp:73-81

Publication Date(Web):1 November 2015

DOI:10.1016/j.engfracmech.2015.09.010

The fracture toughness of carbon fiber reinforced plastic laminates was investigated in term of modifying the epoxy matrix with the pristine and functionalized stacked-cup carbon nanofibers. The results showed that the highest enhancements in Mode I (13.6%) and Mode II (45.3%) fracture toughness were achieved by adding 0.5 wt% and 1.0 wt% functionalized nanofibers, respectively. The toughening mechanism was analyzed based on the morphology evaluations of the fracture surfaces. The evidence of bridging, pull-out, peeling-off and unravelling of nanofibers were clearly observed, which contributed to dissipating more energy for crack propagation, resulting in the improvement of fracture toughness.

Etched glass bubbles as robust micro-containers for self-healing materials

Co-reporter:He Zhang and Jinglei Yang

Journal of Materials Chemistry A 2013 - vol. 1(Issue 41) pp:NaN12720-12720

Publication Date(Web):2013/09/03

DOI:10.1039/C3TA13227G

Etched glass bubbles (GBs) with through-holes at the micron level were fabricated by etching them using dilute hydrofluoric acid (HF) in a specially designed mixer. The semi-segmented mixer under mechanical agitation produces circulation of the GBs in solution, purposely completing the processes of the etching reaction on the GBs, filling the etched GBs with solution, and depositing the well etched GBs in the mixer bottom for collection. Highly reactive primary amine and diisocyanate monomer were separately infiltrated into the etched GBs and formulated as self-healing materials with satisfactory healing performance, indicating the robustness and versatility of the etched GBs.

Robust microcapsules with polyurea/silica hybrid shell for one-part self-healing anticorrosion coatings

Co-reporter:Gang Wu, Jinliang An, Dawei Sun, Xiuzhi Tang, Yong Xiang and Jinglei Yang

Journal of Materials Chemistry A 2014 - vol. 2(Issue 30) pp:NaN11620-11620

Publication Date(Web):2014/04/18

DOI:10.1039/C4TA01312C

Silica/polyurea hybrid microcapsules loaded with hexamethylene diisocyanate (HDI) as core materials were prepared via a combined strategy of interfacial polymerization and an in situ sol–gel process in an oil-in-water emulsion. They were clearly characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The resultant microcapsules have diameters of 57–328 μm, shell thicknesses of 1–8 μm, and core fractions of 51.2–65.6%. The diameter and shell thickness were linearly related to the agitation rate in the double logarithm coordinates, and the core fraction were linearly related to the agitation rate, indicating that the structure and component of the microcapsules can be controlled effectively. The resistant properties against thermal and solvent attacks were assessed by using thermogravimetric analysis and titration. The results show that the microcapsules had outstanding thermal stability with initial evaporation temperature (defined at 5% of weight loss), increased by around 58 °C compared with that of pure core material, and good resistance to xylene with less than 25.9 ± 0.7 wt% reduction of core content after immersion for 100 h. Self-healing anticorrosion coatings based on microcapsules were fabricated on a steel substrate. Preliminary results indicated significant corrosion retardancy occurred in the coatings under an accelerated corrosion process, showing the great potential of our microcapsules in the development of catalyst-free, one-part, self-healing coatings for corrosion control.

Double-layered reactive microcapsules with excellent thermal and non-polar solvent resistance for self-healing coatings

Co-reporter:Dawei Sun, Jinliang An, Gang Wu and Jinglei Yang

Journal of Materials Chemistry A 2015 - vol. 3(Issue 8) pp:NaN4444-4444

Publication Date(Web):2015/01/06

DOI:10.1039/C4TA05339G

Double-layered polyurea microcapsules containing hexamethylene diisocyanate (HDI) with outstanding shell tightness have been successfully synthesized via interfacial polymerization reaction in an oil-in-water emulsion. The resultant capsules were systematically characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. The reaction parameters including reaction temperature (40 °C, 50 °C, 60 °C), reaction duration (1 h, 1.5 h, 2 h and 2.5 h), amount of Suprasec 2644 (2.4 g, 3 g and 3.6 g) and emulsification time (15 min, 45 min and 75 min) were investigated and evaluated in terms of core fraction and quality of microcapsules. The core fraction of microcapsules was reduced with an increase of reaction temperature, reaction duration, mass of Suprasec 2644 and emulsification time, while the quality of microcapsules fluctuated. The thermal and organic solvent resistances were assessed by using TGA and titration. The results showed that the microcapsules had 1.6% weight loss compared with pure HDI with 90% weight loss after 60 min isothermal treatment at 100 °C. After immersion in various solvents for 24 days, the microcapsules released as low as ∼3% of core in weakly polar solvents (i.e. hexane and xylene), about 5–60% in polar aprotic solvents (i.e. ethyl acetate, acetone, DMF and DMSO), and 60–90% in water and polar protic solvents (i.e. isopropanol and ethylene glycol). Both fresh and hexane-treated HDI capsules showed excellent anticorrosion performance in scratched coatings via self-healing functionality, indicating promising practical application in industrial coating and paint systems.

Facile microencapsulation of HDI for self-healing anticorrosion coatings

Co-reporter:Mingxing Huang and Jinglei Yang

Journal of Materials Chemistry A 2011 - vol. 21(Issue 30) pp:NaN11130-11130

Publication Date(Web):2011/06/30

DOI:10.1039/C1JM10794A

Polyurethane (PU) microcapsules containing hexamethylene diisocyanate (HDI) as core materials are facilely manufactured via interfacial polymerization reaction of commercial methylene diphenyl diisocyanate (MDI) prepolymer and 1,4-butanediol in an oil-in-water emulsion. The resultant capsules have diameters of 5–350 μm and shell thickness of 1–15 μm, both linearly related to the agitation rate in the double logarithm coordinates. The typical core fraction of microcapsules and the yield of synthesis are around 60 wt% and 70 wt%, respectively, while varying with reaction conditions. The effects of parameters including reaction duration and temperature, surfactant concentration, agitation rate, and environmental factors on the formation of microcapsules were systematically investigated and optimized. Quality assessments of each batch of microcapsules were performed using thermogravimetric analysis and scanning electron microscopy. Anticorrosion coatings mixed with synthesized microcapsules were prepared on a steel substrate. Preliminary results indicated significant corrosion retardancy happened in the self-healing coatings under an accelerated corrosion process, showing the great potential of this facile microencapsulation technique in development of catalyst-free, one-part self-healing coatings for corrosion control.

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