Co-reporter:Yaxin Liu, Dongzhi Yang, Ruomeng Yu, Jin Qu, Yongzheng Shi, Hongfei Li, and Zhong-Zhen Yu
The Journal of Physical Chemistry C November 16, 2017 Volume 121(Issue 45) pp:25172-25172
Publication Date(Web):October 21, 2017
DOI:10.1021/acs.jpcc.7b07848
The degradation efficiency and recyclability of photocatalysts are the key for their practical applications. Tetrahedral silver phosphate (Ag3PO4) is a superior visible-light photocatalyst, while graphene oxide (GO) sheets with high specific surface area and abundant functional groups are expected to further enhance the photocatalytic efficiency and improve the recyclability of Ag3PO4. Herein, we demonstrate an eco-friendly and kinetically controlled approach to synthesize Ag3PO4/GO hybrids. Tetrahedral Ag3PO4 are grown in situ on the GO sheets in mixed solvents, and their microstructures are controlled by the slow dissolution and ionization of H3PO4 and the adjustment of the volume ratios of ethanol/water solvents. The hybrid with 5 wt % of GO exhibits an extraordinary photocatalytic efficiency and satisfactory recyclability for the degradation of organic dyes. Approximately 99% of methylene blue could be degraded in 4 min, and the degradation percentage is still as high as 97% even after 5 cycles of photocatalytic degradations. The mechanism of reinforcement of the photocatalytic performance was also studied. This hybridization of tetrahedral Ag3PO4 with GO sheets provides an efficient solution to the photocorrosion of Ag3PO4 and is an efficient approach for synthesizing Ag3PO4-based semiconducting hybrids as highly efficient and recyclable photocatalysts.
Co-reporter:Ya-Qiong Jing, Chen-Xi Gui, Jin Qu, Shu-Meng Hao, Qian-Qian Wang, and Zhong-Zhen Yu
ACS Sustainable Chemistry & Engineering May 1, 2017 Volume 5(Issue 5) pp:3641-3641
Publication Date(Web):January 20, 2017
DOI:10.1021/acssuschemeng.6b02650
The abilities of adsorption and separation of electron hole pairs are two important factors in photodegradation, and a balance between them is required to obtain an excellent photodegradation performance. As a new photocatalyst, silver silicate has a poor conductivity that hinders its photodegradation ability. Herein, silver silicate (AgSiOx)@carbon nanotube (CNT) and AgSiOx@reduced graphene oxide (RGO) nanocomposites are prepared for the first time to improve the photodegradation performance of AgSiOx. The influences of CNT and RGO contents on improving the photodegradation efficiency of AgSiOx are different due to the differences in the concentration of oxygen-containing groups and the electrical conductivity. The photodegradation efficiency of AgSiOx@CNT nanocomposites first increases and then decreases with increasing the concentration of CNTs, while the removal efficiency of pollutants by AgSiOx@RGO nanocomposites increases with the GO concentration owing to the residual oxygen-containing functional groups on RGO. The AgSiOx@CNT nanocomposite with a trace amount of CNTs (0.1 wt %) shows fairly effective photodegradation activity, and its photodegradation process is completed in 10 min with a higher removal efficiency and rate constant than reported.Keywords: Carbon nanotube; Photodegradation; Reduced graphene oxide; Silver silicate; Visible light;
Co-reporter:Ting Xu, Hongyang Yang, Dongzhi Yang, and Zhong-Zhen Yu
ACS Applied Materials & Interfaces June 28, 2017 Volume 9(Issue 25) pp:21094-21094
Publication Date(Web):May 24, 2017
DOI:10.1021/acsami.7b01176
In this work, a bicomponent scaffold with a core–shell and islandlike structure that combines the respective advantages of polylactic acid (PLA) and chitosan (CS) was prepared via electrospinning accompanied by automatic phase separation and crystallization. The objective of this research was to design nanosized topography with highly bioactive CS onto PLA electrospun fiber surface to improve the cell biocompatibility of the PLA fibrous membrane. The morphology, inner structure, surface composition, crystallinity, and thermodynamic analyses of nanofibers with various PLA/CS ratios were carried out, and the turning mechanism of a core–shell or islandlike topography structure was also speculated. The mineralization of hydroxyapatite and culture results of preosteoblast (MC3T3-E1) cells on the modified scaffolds indicate that the outer CS component and rough nanoscale topography on the surface of the nanofibers balanced the hydrophilicity and hydrophobicity of the fibers, enhanced their mineralization ability, and made them more beneficial for the attachment and growth of cells. Moreover, CS and “islandlike” protrusions on the fiber surface increased the alkaline phosphatase activity of the MC3T3-E1 cells seeded on the fibrous membrane and provided a more appropriate interface for cell adhesion and proliferation. These results illustrate that this kind of PLA/CS membrane has the potential in tissue engineering. More importantly, our study provides a new approach to designing PLA scaffolds, with combined topographic and bioactive modification effects at the interface between cells and materials, for biomedicine.Keywords: chitosan; core−shell; electrospun; island; polylactic acid; tissue engineering;
Co-reporter:Ruomeng Yu, Yongzheng Shi, Dongzhi Yang, Yaxin Liu, Jin Qu, and Zhong-Zhen Yu
ACS Applied Materials & Interfaces July 5, 2017 Volume 9(Issue 26) pp:21809-21809
Publication Date(Web):June 7, 2017
DOI:10.1021/acsami.7b04655
Multifunctional graphene oxide (GO)/chitosan (CS) aerogel microspheres (GCAMs) with honeycomb-cobweb and radially oriented microchannel structures are prepared by combining electrospraying with freeze-casting to optimize adsorption performances of heavy metal ions and soluble organic pollutants. The GCAMs exhibit superior adsorption capacities of heavy metal ions of Pb(II), Cu(II), and Cr(VI), cationic dyes of methylene blue (MB) and Rhodamine B, anionic dyes of methyl orange and Eosin Y, and phenol. It takes only 5 min to reach 82 and 89% of equilibrium adsorption capacities for Cr(VI) (292.8 mg g–1) and MB (584.6 mg g–1), respectively, much shorter than the adsorption equilibrium time (75 h) of a GO/CS monolith. More importantly, the GCAMs maintain excellent adsorption capacity for six cycles of adsorption–desorption. The broad-spectrum, rapid, and reusable adsorption performance makes the GCAMs promising for highly efficient water treatments.Keywords: adsorption; aerogels; graphene oxide; recyclability; water treatment;
Co-reporter:Xing-Hua Li;Xiaofeng Li;Kai-Ning Liao;Peng Min;Tao Liu;Aravind Dasari
ACS Applied Materials & Interfaces December 7, 2016 Volume 8(Issue 48) pp:33230-33239
Publication Date(Web):November 7, 2016
DOI:10.1021/acsami.6b12295
Dispersion and spatial distribution of graphene sheets play crucial roles in tailoring mechanical and functional properties of their polymer composites. Anisotropic graphene aerogels (AGAs) with highly aligned graphene networks are prepared by a directional-freezing followed by freeze-drying process and exhibit different microstructures and performances along the axial (freezing direction) and radial (perpendicular to the axial direction) directions. Thermal annealing at 1300 °C significantly enhances the quality of both AGAs and conventional graphene aerogels (GAs). The aligned graphene/epoxy composites show highly anisotropic mechanical and electrical properties and excellent electromagnetic interference (EMI) shielding efficiencies at very low graphene loadings. Compared to the epoxy composite with 0.8 wt % thermally annealed GAs (TGAs) with an EMI shielding effectiveness of 27 dB, the aligned graphene/epoxy composite with 0.8 wt % thermally treated AGAs (TAGAs) has an enhanced EMI shielding effectiveness of 32 dB along the radial direction with a slightly decreased shielding effectiveness of 25 dB along the axial direction. With 0.2 wt % TAGA, its epoxy composite exhibits a shielding effectiveness of 25 dB along the radial direction, which meets the requirement of ∼20 dB for practical EMI shielding applications.Keywords: anisotropic graphene aerogel; directional freezing; electrical conductivity; electromagnetic interference shielding; epoxy;
Co-reporter:Yu-Jiao Zhang, Jin Qu, Shu-Meng Hao, Wei Chang, Qiu-Yu Ji, and Zhong-Zhen Yu
ACS Applied Materials & Interfaces December 6, 2017 Volume 9(Issue 48) pp:41878-41878
Publication Date(Web):November 10, 2017
DOI:10.1021/acsami.7b13558
Increasing demands for lithium-ion batteries (LIBs) with high energy density and high power density require highly reversible electrochemical reactions to enhance the cyclability and capacities of electrodes. As the reversible formation/decomposition of the solid electrolyte interface (SEI) film during the lithiation/delithiation process of Fe3S4 could bring about a higher capacity than its theoretical value, in the present work, synthesized Fe3S4 nanoparticles are sandwich-wrapped with reduced graphene oxide (RGO) to fabricate highly reversible and long cycling life anode materials for high-performance LIBs. The micron-sized long slit between sandwiched RGO sheets effectively prevents the aggregation of intermediate phases during the discharge/charge process and thus increases cycling capacity because of the reversible formation/decomposition of the SEI film driven by Fe nanoparticles. Furthermore, the RGO sheets interconnect with each other by a face-to-face mode to construct a more efficiently conductive network, and the maximum interfacial oxygen bridge bonds benefit the fast electron hopping from RGO to Fe3S4, improving the depth of the electrochemical reactions and facilitating the highly reversible lithiation/delithiation of Fe3S4. Thus, the resultant Fe3S4/RGO hybrid shows a highly reversible charge capacity of 1324 mA h g–1 over 275 cycles at a current density of 100 mA g–1, even retains 480 mA h g–1 over 500 cycles at 1000 mA g–1, which are much higher than reported values.Keywords: anode; Fe3S4; lithium ion batteries; reduced graphene oxide; solid electrolyte interface film;
Co-reporter:Renhui Sun;Hao-Bin Zhang;Ji Liu;Xi Xie;Rui Yang;Yue Li;Song Hong
Advanced Functional Materials 2017 Volume 27(Issue 45) pp:
Publication Date(Web):2017/12/01
DOI:10.1002/adfm.201702807
AbstractHighly conductive polymer nanocomposites are greatly desired for electromagnetic interference (EMI) shielding applications. Although transition metal carbide/carbonitride (MXene) has shown its huge potential for producing highly conductive films and bulk materials, it still remains a great challenge to fabricate extremely conductive polymer nanocomposites with outstanding EMI shielding performance at minimal amounts of MXenes. Herein, an electrostatic assembly approach for fabricating highly conductive MXene@polystyrene nanocomposites by electrostatic assembling of negative MXene nanosheets on positive polystyrene microspheres is demonstrated, followed by compression molding. Thanks to the high conductivity of MXenes and their highly efficient conducting network within polystyrene matrix, the resultant nanocomposites exhibit not only a low percolation threshold of 0.26 vol% but also a superb conductivity of 1081 S m−1 and an outstanding EMI shielding performance of >54 dB over the whole X-band with a maximum of 62 dB at the low MXene loading of 1.90 vol%, which are among the best performances for electrically conductive polymer nanocomposites by far. Moreover, the same nanocomposite has a highly enhanced storage modulus, 54% and 56% higher than those of neat polystyrene and conventional MXene@polystyrene nanocomposite, respectively. This work provides a novel methodology to produce highly conductive polymer nanocomposites for highly efficient EMI shielding applications.
Co-reporter:Yongzheng Shi, Dongzhi Yang, Yuan Li, Jin Qu, Zhong-Zhen Yu
Applied Surface Science 2017 Volume 426(Volume 426) pp:
Publication Date(Web):31 December 2017
DOI:10.1016/j.apsusc.2017.06.302
•PAN@TiO2/Ag membranes with high visible light response are fabricated.•TiO2/Ag heterojunctions are formed using dopamine as a binder and reductant.•Nanosized Ag enhances visible light absorption and inhibits recombination of e−/h+.•PAN@TiO2/Ag membrane exhibits stable reusability.Although TiO2-based photocatalysts have exhibited a great potential for degradation of organic pollutants, it is still necessary to simultaneously enhance their visible-light-driven photocatalytic efficiency and physical recyclability. Herein, highly efficient, visible-light-driven photocatalytically active, and recyclable nanofibrous membranes with thin TiO2/Ag heterojunction layer are prepared using electrospun polyacrylonitrile (PAN) nanofibrous membrane as the substrate. By regulating the concentration and hydrolysis process of Ti precursors, TiO2 nanoparticles steadily grow on the PAN nanofibers with high-specific surface area to form a continuous mesoporous shell with the thickness of 20 nm for efficient degradation of organic pollutants. Furthermore, to form a stable heterojunction structure, Ag nanoparticles are deposited on the TiO2 surface by using dopamine as a binder and reductant. The presence of Ag nanoparticles leads to an obvious red-shift from 380 nm to 490 nm, which improves the utilization efficiency of visible light, and reduces the electron/hole recombination rate simultaneously. The resulting PAN@TiO2/Ag membranes hold enhanced photocatalytic activity for methylene blue degradation within 1 h under visible light irradiation, and satisfactory recyclability, which endow them with a great potential for adsorption and photocatalytic applications.Download high-res image (115KB)Download full-size image
Co-reporter:Ji Liu, Hao-Bin Zhang, Yafeng Liu, Qiwei Wang, Zhangshuo Liu, Yiu-Wing Mai, Zhong-Zhen Yu
Composites Science and Technology 2017 Volume 151(Volume 151) pp:
Publication Date(Web):20 October 2017
DOI:10.1016/j.compscitech.2017.08.005
Highly efficient and lightweight electromagnetic interference (EMI) shielding materials have gained tremendous interests due to the urgent requirement for smart electronic devices and aerospace applications. Herein, we demonstrate a highly efficient hydrazine-induced foaming approach to fabricate magnetic, highly electrically conductive, and lightweight graphene/iron pentacarbonyl (IP) porous films for broadband EMI shielding application. The chitosan introduced effectively optimizes the microcellular structures by improving the interfacial adhesion between graphene sheets and thus enhances the electrical conduction of the porous films with IP flakes. The resultant porous structure not only reduces the density of the films, but also improves the electromagnetic radiation attenuation by repeated scattering of the incident microwave. The presence of magnetic IP flakes endows the porous film with magnetic property and enhanced EMI shielding performance by combining the dielectric and magnetic losses. Thus, the porous film with a small thickness of 0.3 mm and a low density of 0.12 g/cm3 exhibits an excellent broadband EMI shielding performance of >38 dB in the frequency range of 8.2–59.6 GHz with a total bandwidth of 51.4 GHz. These results indicate that the lightweight porous film with outstanding magnetic and electrical properties could be used as multifunctional high-performance EMI shielding materials.
Co-reporter:Yu Chen, Hao-Bin Zhang, Mu Wang, Xin Qian, Aravind Dasari, Zhong-Zhen Yu
Composites Science and Technology 2017 Volume 152(Volume 152) pp:
Publication Date(Web):10 November 2017
DOI:10.1016/j.compscitech.2017.09.022
Highly porous graphene aerogels enhanced with phenolic resol resin are prepared by a hydrothermal synthesis followed by high-temperature annealing. The introduced phenolic resol resin and its pyrolysis derivative effectively combine the sheets together and thus the three-dimensional networks of the enhanced aerogels are well retained even after compounding with epoxy resin. The synthesized aerogels are highly efficient in endowing epoxy with high electrical conductivity, excellent electromagnetic interference (EMI) shielding efficiency and satisfactory mechanical reinforcement. With only 0.33 wt% of the annealed aerogel, its epoxy nanocomposite exhibits a high electrical conductivity of 73 S/m and an excellent EMI shielding effectiveness of 35 dB, which are among the best results for polymer nanocomposites with even higher loadings. Especially, the EMI shielding performance is comparable to or even higher than that of the nanocomposite filled with chemical vapor deposition-synthesized graphene foam. Furthermore, the aerogel also leads to notable 67% and 20.2% increases in flexural strength and flexural modulus, respectively. Therefore, the phenolic resin-enhanced graphene aerogel holds a great potential in producing high-performance polymer nanocomposites for EMI shielding application.
Co-reporter:Kun-Le Jia, Jin Qu, Shu-Meng Hao, Fei An, Ya-Qiong Jing, Zhong-Zhen Yu
Journal of Colloid and Interface Science 2017 Volume 506(Volume 506) pp:
Publication Date(Web):15 November 2017
DOI:10.1016/j.jcis.2017.07.040
Construction of a heterostructure to prolong the life of electron-hole pairs is a very important approach to endow it with excellent photodegradation performances. Particularly, one-pot synthesis of heterostructures with the same component but different crystal structures to form a proper band gap is still challenging. Herein, bismuth silicate (BSO) heterostructures are synthesized using a one-pot hydrothermal approach without adding any other inorganic components. The crystal phase, morphology, surface state, and photochemical properties of the BSO materials are precisely tuned to fabricate two kinds of bismuth silicate heterostructures: rod-like Bi2SiO5/Bi12SiO20 and flower-like Bi2SiO5/Bi4Si3O12 heterostructures. Thanks to the two heterostructures and clean surface, the optimized BSO material exhibits a highly active photocatalytic performance with a remarkable cycling stability. It photodegrades Rhodamine B under visible light irradiation as fast as 15 min with the reaction rate constants k and ks to be 0.399 min−1 and 0.698 min−1 L m−2, respectively, which is up to 189 times faster than reported.Download high-res image (113KB)Download full-size image
Co-reporter:Fang-Lan Guan;Fei An;Jing Yang;Xiaofeng Li 李晓锋
Chinese Journal of Polymer Science 2017 Volume 35( Issue 11) pp:1381-1390
Publication Date(Web):09 August 2017
DOI:10.1007/s10118-017-1972-z
To enhance the mechanical properties of three-dimensional graphene aerogels with aramid fibers, graphene/organic fiber aerogels are prepared by chemical reduction of graphene oxide in the presence of organic fibers of poly(p-phenylene terephthalamide) (PPTA) and followed by freeze-drying. Thermal annealing of the composite aerogels at 1300 °C is adopted not only to restore the conductivity of the reduced graphene oxide component but also to convert the insulating PPTA organic fibers to conductive carbon fibers by the carbonization. The resultant graphene/carbon fiber aerogels (GCFAs) exhibit high electrical conductivities and enhanced compressive properties, which are highly efficient in improving both mechanical and electrical performances of epoxy composites. Compared to those of neat epoxy, the compressive modulus, compressive strength and energy absorption of the electrically conductive GCFA/epoxy composite are significantly increased by 60%, 59% and 131%, respectively.
Co-reporter:Yu Chen;Hao-Bin Zhang;Yanbing Yang;Mu Wang;Anyuan Cao
Advanced Functional Materials 2016 Volume 26( Issue 3) pp:447-455
Publication Date(Web):
DOI:10.1002/adfm.201503782
Light-weight and high-performance electromagnetic interference (EMI)-shielding epoxy nanocomposites are prepared by an infiltration method using a 3D carbon nanotube (CNT) sponge as the 3D reinforcement and conducting framework. The preformed, highly porous, and electrically conducting framework acts as a highway for electron transport and can resist a high external loading to protect the epoxy nanocomposite. Consequently, a remarkable conductivity of 148 S m−1 and an outstanding EMI shielding effectiveness of around 33 dB in the X-band are achieved for the epoxy nanocomposite with 0.66 wt% of CNT sponge, which is higher than that achieved for epoxy nanocomposites with 20 wt% of conventional CNTs. More importantly, the CNT sponge provides a dual advantage over conventional CNTs in its prominent reinforcement and toughening of the epoxy composite. Only 0.66 wt% of CNT sponge significantly increases the flexural and tensile strengths by 102% and 64%, respectively, as compared to those of neat epoxy. Moreover, the nanocomposite shows a 250% increase in tensile toughness and a 97% increase in elongation at break. These results indicate that CNT sponge is an ideal functional component for mechanically strong and high-performance EMI-shielding nanocomposites.
Co-reporter:Jing Yang, Enwei Zhang, Xiaofeng Li, Yunhua Yu, Jin Qu, and Zhong-Zhen Yu
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 3) pp:2297
Publication Date(Web):December 29, 2015
DOI:10.1021/acsami.5b11337
Three dimensional reduced graphene oxide (RGO)/Ni foam composites are prepared by a facile approach without using harmful reducing agents. Graphene oxide is reduced by Ni foam directly in its aqueous suspension at pH 2 at room temperature, and the resultant RGO sheets simultaneously assemble around the pillars of the Ni foam. The RGO/Ni foam composite is used as a binder-free supercapacitor electrode and exhibits high electrochemical properties. Its areal capacitance is easily tuned by varying the reduction time for different RGO loadings. When the reduction time increases from 3 to 15 days, the areal capacitance of the composite increases from 26.0 to 136.8 mF cm–2 at 0.5 mA cm–2. Temperature is proven to be a key factor in influencing the reduction efficiency. The composite prepared by 5 h reduction at 70 °C exhibits even better electrochemical properties than its counterpart prepared by 15 day reduction at ambient temperature. The 5 h RGO/Ni foam composite shows an areal capacitance of 206.7 mF cm–2 at 0.5 mA cm–2 and good rate performance and cycling stability with areal capacitance retention of 97.4% after 10000 cycles at 3 mA cm–2. Further extending the reduction time to 9 h at 70 °C, the composite shows a high areal capacitance of 323 mF cm–2 at 0.5 mA cm–2. Moreover, the good rate performance and cycling stability are still maintained.Keywords: binder-free; electrochemical performance; graphene oxide; Ni foam; supercapacitor electrode
Co-reporter:Renhui Sun, Hao-Bin Zhang, Jian Yao, Dongzhi Yang, Yiu-Wing Mai, Zhong-Zhen Yu
Carbon 2016 Volume 107() pp:138-145
Publication Date(Web):October 2016
DOI:10.1016/j.carbon.2016.05.041
Hierarchical carbon nanotube (CNT)@graphene (CNT@G) hybrid is regarded as a promising nanomaterial for various potential applications. The formation of well-defined catalyst nanoparticles on graphene substrate is essential for further nanostructure constructions. Herein, we report an efficient and green method to synthesize Fe nanoparticles that are uniformly anchored on the inert surfaces of graphene by supercritical carbon dioxide-assisted deposition of Fe2O3 followed by in situ carbothermal reduction with graphene as the reducing agent. The successful synthesis of the Fe nanoparticles is confirmed by in situ X-ray diffraction characterization. The reduction mechanism of Fe2O3 nanoparticles with graphene is well-analyzed based on the thermogravimetry-mass spectroscopy results. Furthermore, CNT@G hybrid is thus synthesized by chemical vapor deposition of the in situ formed Fe nanoparticles that are anchored on graphene sheets and used as the catalyst for the growth of CNTs. By controlling the oxidation conditions, graphene hybrids decorated with γ-Fe2O3 and α-Fe2O3 nanoparticles are also easily fabricated. This work helps understand the carbothermal reduction of graphene and provides a novel, efficient and green route for the synthesis of graphene hybrids.
Co-reporter:Jing Yang, Enwei Zhang, Xiaofeng Li, Yiting Zhang, Jin Qu, Zhong-Zhen Yu
Carbon 2016 Volume 98() pp:50-57
Publication Date(Web):March 2016
DOI:10.1016/j.carbon.2015.10.082
•Phase change composites show high thermal conductivity, good shape stability and large latent heat of fusion.•Cellulose/graphene nanoplatelet (GNP) aerogel benefits the encapsulation of polyethylene glycol and prevents its leakage.•Highly porous cellulose network and low loading of defect-free GNPs are responsible for the high latent heat of fusion.As phase change composites, high thermal conductivity, large latent heat of fusion and good shape stability are all required for practical applications. By combining defect-free graphene nanoplatelets (GNPs) and microcrystalline cellulose, lightweight cellulose/GNP aerogels are fabricated and their highly porous but strong three-dimensional networks benefit the encapsulation of polyethylene glycol (PEG) and prevent the leakage of PEG above its melting point. Phase change composites are prepared by vacuum-assisted impregnating of PEG into the cellulose/GNP aerogels, which exhibit high thermal conductivity, good shape stability and high latent heat of fusion. Even compressed upon the melting point of PEG, the phase change composites keep their shapes stable without any leakage. With only 5.3 wt% of GNPs, the composite exhibits a high thermal conductivity of 1.35 W m−1 K−1, 463% higher than that of the composite without GNPs. The highly porous cellulose network and the low loading of highly thermally conductive GNPs are responsible for the high loading of PEG in the composite with a satisfactory latent heat of fusion of 156.1 J g−1.
Co-reporter:Renhui Sun, Hua Yao, Hao-Bin Zhang, Yue Li, Yiu-Wing Mai, Zhong-Zhen Yu
Composites Science and Technology 2016 Volume 137() pp:16-23
Publication Date(Web):12 December 2016
DOI:10.1016/j.compscitech.2016.10.017
Although graphene can significantly improve the thermal conductivity of polymers due to its high aspect ratio and excellent thermal conductance, it causes serious reduction in electrical insulation and thus limits the wide applications of its polymer composites in the thermal management of electronics and systems. To solve this problem, electrically insulating Al2O3 is used to decorate high quality (defect-free) graphene nanoplatelets (GNPs). Aided by supercritical carbon dioxide (scCO2), numerous Al2O3 nanoparticles are formed on the inert GNP surfaces by fast nucleation and hydrolysis of Al(NO3)3 precursor followed by calcination at 600 °C. Alternatively, by controlling nucleation and hydrolysis of Al2(SO4)3 precursor with a buffer solution, Al2(SO4)3 slowly nucleates and hydrolyzes on GNPs to form aluminum hydroxide, which is then converted to Al2O3 nanolayers without phase separation by calcination. Compared to the Al2O3@GNP hybrid with the assistance of scCO2, the hybrid prepared with the help of a buffer solution is highly efficient in conferring epoxy with excellent thermal conductivity while retaining its electrical insulation. Epoxy composite with 12 wt% of Al2O3@GNP hybrid exhibits a high thermal conductivity of 1.49 W/(mK), which is 677% higher than that of neat epoxy, indicating its high potential as thermally conductive and electrically insulating fillers for polymer-based functional composites.
Co-reporter:Fang-Lan Guan, Chen-Xi Gui, Hao-Bin Zhang, Zhi-Guo Jiang, Yue Jiang, Zhong-Zhen Yu
Composites Part B: Engineering 2016 Volume 98() pp:134-140
Publication Date(Web):1 August 2016
DOI:10.1016/j.compositesb.2016.04.062
Thermally conductive epoxy composites with eco-friendly flame retardancy are prepared by using spherical alumina (Al2O3), magnesium hydroxide and graphene nanoplatelets (GNPs) as thermally conductive fillers. Highly filled alumina particles do not seriously increase the viscosity of the epoxy monomer due to their spherical shape and smooth surface and thus the compounding keeps a good processibility; The incorporation of small amounts of layered GNPs efficiently increases the thermal conductivity of epoxy/Al2O3 composites because of the synergistic effect between layered GNPs and spherical Al2O3 on forming a thermally conductive network within epoxy matrix. Interestingly, the addition of a small amount of eco-friendly magnesium hydroxide endows the thermally conductive epoxy composites with a satisfactory flame retardancy. The epoxy composite with 68% Al2O3, 7% modified GNPs (m-GNPs) and 5% magnesium hydroxide is determined as the optimum composition with a high thermal conductivity of 2.2 W/(mK), 11 times of that of neat epoxy. Its satisfactory flame retardancy is confirmed by the high limiting oxygen index of 39% and UL-94 rating of V-0 with no dripping. The compact, dense and uniform char layers derived from well-dispersed m-GNPs act as efficient barrier layers and contribute to the flame retardant properties of the epoxy composites.
Co-reporter:Chen-Xi Gui, Shu-Meng Hao, Yuan Liu, Jin Qu, Cheng Yang, Yunhua Yu, Qian-Qian Wang and Zhong-Zhen Yu
Journal of Materials Chemistry A 2015 vol. 3(Issue 32) pp:16551-16559
Publication Date(Web):03 Jul 2015
DOI:10.1039/C5TA03408F
Layered nickel silicate provides massive interlayer space similar to graphite for the insertion and extraction of lithium ions and sodium ions; however, the poor electrical conductivity limits its electrochemical applications in energy storage devices. Herein, carbon nanotube@layered nickel silicate (CNT@NiSiOx) coaxial nanocables with flexible nickel silicate nanosheets grown on conductive carbon nanotubes (CNTs) are synthesized by a mild hydrothermal method. CNTs serve as conductive cables to improve the electron transfer performance of nickel silicate nanosheets, resulting in reduced contact and charge-transfer resistances. In addition to a high specific surface area, short ion diffusion distance and good electrical conductivity, one-dimensional coaxial nanocables have a stable structure to sustain volume change and avoid structure destruction during the charge–discharge process. As an anode material for lithium storage, the first cycle charge capacity of the CNT@NiSiOx nanocables reaches 770 mA h g−1 with the first cycle coulombic efficiency as high as 71.5%. Even after 50 cycles, the charge capacity still reaches 489 mA h g−1 at a current density of 50 mA g−1, which is nearly 87% and 360% higher than those of the NiSiOx/CNT mixture and nickel silicate nanotube, respectively. As anode materials for sodium storage, the coaxial nanocables exhibit a high initial charge capacity of 576 mA h g−1, which even retains 213 mA h g−1 at 20 mA g−1 after 16 cycles.
Co-reporter:Qian-Qian Wang, Jin Qu, Yuan Liu, Chen-Xi Gui, Shu-Meng Hao, Yunhua Yu and Zhong-Zhen Yu
Nanoscale 2015 vol. 7(Issue 40) pp:16805-16811
Publication Date(Web):10 Sep 2015
DOI:10.1039/C5NR05719A
The combination of active materials with electrically conductive carbon materials and their contact efficiency are crucial for improving the electrochemical performances of active materials. Here, nickel silicate (NiSiOx) nanoplates are planted in situ on the surface of reduced graphene oxide (RGO) nanosheets to form a two dimensional face-to-face nanocomposite of NiSiOx/RGO for lithium storage. The face-to-face structure enhances the contact efficiency of NiSiOx with RGO, and thus leads to a higher reversible capacity and better rate performance of the NiSiOx/RGO nanocomposite than both carbon nanotube (CNT)@NiSiOx nanocables and NiSiOx. The layered NiSiOx/RGO nanocomposite exhibits a high reversible specific capacity of 797 mA h g−1, which is 62% and 806% higher than those of CNT@NiSiOx nanocables and NiSiOx alone, respectively.
Co-reporter:Xin Qi, Jin Qu, Hao-Bin Zhang, Dongzhi Yang, Yunhua Yu, Cheng Chi and Zhong-Zhen Yu
Journal of Materials Chemistry A 2015 vol. 3(Issue 30) pp:15498-15504
Publication Date(Web):16 Jun 2015
DOI:10.1039/C5TA03087K
We report a facile and efficient approach to prepare graphene and FeCl3-intercalated few-layer graphene (FeCl3-FLG) with stage 1 FeCl3-graphite intercalation compounds (GICs) as a precursor by a non-oxidation process. The enlarged interlayer spacing by the intercalation of FeCl3 greatly weakens the interaction among graphite sheets and thus facilitates the exfoliation of FeCl3-GICs. By ultrasonic treatment, FeCl3-GICs are well exfoliated to graphene sheets (<2 nm) with a high yield of 100%, while the ultrasonication of pristine graphite is less efficient with a low yield (about 32%) of graphene sheets. By simply controlling the sonication time, FeCl3-FLG consisting of graphene sheets and sandwiched FeCl3 is also prepared, which exhibits a high capacity of 989 mA h g−1 after 50 cycles, fairly higher than that of the sonicated graphite (503 mA h g−1) and the theoretical value of graphite (372 mA h g−1). Furthermore, FeCl3-FLG still retains a reversible capacity as high as 539 mA h g−1 even at a current density of 1000 mA g−1. Therefore, the high reversible capacity, remarkable cycling stability and superior capability make FeCl3-FLG promising as anode materials for large-scale and high-capacity lithium ion batteries.
Co-reporter:Xin Zhi, Hao-Bin Zhang, Yong-Fei Liao, Qi-Hui Hu, Chen-Xi Gui, Zhong-Zhen Yu
Carbon 2015 Volume 82() pp:195-204
Publication Date(Web):February 2015
DOI:10.1016/j.carbon.2014.10.062
Co-reporter:Yu Chen, Yongli Wang, Hao-Bin Zhang, Xiaofeng Li, Chen-Xi Gui, Zhong-Zhen Yu
Carbon 2015 Volume 82() pp:67-76
Publication Date(Web):February 2015
DOI:10.1016/j.carbon.2014.10.031
Polystyrene (PS) composites with satisfactory electromagnetic interference (EMI) shielding performance were prepared by solution blending of PS with thermally exfoliated and reduced graphene oxide (TGO) and modified Fe3O4 nanoparticles. For comparison, Fe3O4@reduced graphene oxide (RGO) hybrid and its PS composites were also prepared. The morphologies of Fe3O4@RGO hybrid and Fe3O4 nanoparticles were studied in terms of microstructure and magnetic properties. Surface modification of Fe3O4 nanoparticles enhances their compatibility with PS and thus their uniform dispersion in the PS matrix. Much higher electrical conductivity and EMI shielding effectiveness are achieved for PS/TGO/Fe3O4 composites in comparison to those of PS/Fe3O4@RGO composites. Interestingly, PS/TGO/Fe3O4 composites exhibit obviously improved EMI shielding effectiveness in relative to that of PS/TGO composite although their electrical conductivities are similar. The EMI shielding effectiveness of PS/TGO/Fe3O4 composite is more than 30 dB in the frequency range of 9.8–12 GHz with only 2.24% of graphene. The effect of Fe3O4 size on the composite properties is investigated and the EMI shielding mechanism is discussed.
Co-reporter:Yu Chen, Hao-Bin Zhang, Yaqin Huang, Yue Jiang, Wen-Ge Zheng, Zhong-Zhen Yu
Composites Science and Technology 2015 Volume 118() pp:178-185
Publication Date(Web):30 October 2015
DOI:10.1016/j.compscitech.2015.08.023
Magnetic and electrically conductive epoxy nanocomposites are fabricated by compounding thermally reduced graphene oxide (TGO) and magnetic carbonyl iron (CI) using a solvent-free and efficient centrifugal mixing method. The addition of TGO sheets not only forms an interconnected conducting network within the epoxy matrix, but also prevents the aggregation of heavy CI components. The incorporation of CI components leads to obvious increases in permeability, magnetic loss, and electromagnetic interference (EMI) shielding properties. Among different shapes of CI components, spherical CI particles result in the best EMI shielding performance. The ternary nanocomposites exhibit excellent shielding effectiveness (>36 dB within 9.5–12 GHz) and a maximum value of ∼40 dB at 11.7 GHz, much higher than that (∼20 dB) of epoxy/TGO nanocomposite with the same content of TGO. Wave absorption loss is confirmed to be the main EMI shielding mechanism for the epoxy nanocomposites. The high EMI shielding performance makes the epoxy nanocomposites promising for EMI shielding applications.
Co-reporter:Chen-Xi Gui, Qian-Jie Li, Ling-Ling Lv, Jin Qu, Qian-Qian Wang, Shu-Meng Hao and Zhong-Zhen Yu
RSC Advances 2015 vol. 5(Issue 26) pp:20440-20445
Publication Date(Web):13 Feb 2015
DOI:10.1039/C5RA02596F
Core–shell structured MgO@mesoporous silica spheres are synthesized by a two-step programmed method. MgO@mesoporous silica exhibits a high BET specific surface area of 567 m2 g−1 and a pore volume of 1.08 cm3 g−1. The stable mesoporous silica coating not only serves as a strong shell to improve the mechanical stability of MgO, but also enriches the adsorbates in the mesopores to reach a higher adsorption rate. The core–shell MgO@mesoporous silica spheres exhibit excellent removal capabilities of 3297 mg g−1 for Pb2+ and 420 mg g−1 for methylene blue, which are much higher than those of MgO itself.
Co-reporter:Chen-Xi Gui, Qian-Qian Wang, Shu-Meng Hao, Jin Qu, Pei-Pei Huang, Chang-Yan Cao, Wei-Guo Song, and Zhong-Zhen Yu
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 16) pp:14653
Publication Date(Web):July 29, 2014
DOI:10.1021/am503997e
A sandwichlike magnesium silicate/reduced graphene oxide nanocomposite (MgSi/RGO) with high adsorption efficiency of organic dye and lead ion was synthesized by a hydrothermal approach. MgSi nanopetals were formed in situ on both sides of RGO sheets. The nanocomposite with good dispersion of nanopetals exhibits a high specific surface area of 450 m2/g and a good mass transportation property. Compared to MgSi and RGO, the mechanical stability and adsorption capacity of the nanocomposite is significantly improved due to the synergistic effect. The maximum adsorption capacities for methylene blue and lead ion are 433 and 416 mg/g, respectively.Keywords: adsorption; lead ion; magnesium silicate; nanocomposite; reduced graphene oxide
Co-reporter:Fang-Yuan Yuan, Hao-Bin Zhang, Xiaofeng Li, Hui-Ling Ma, Xiao-Zeng Li, Zhong-Zhen Yu
Carbon 2014 Volume 68() pp:653-661
Publication Date(Web):March 2014
DOI:10.1016/j.carbon.2013.11.046
We report an efficient one-step approach to reduce and functionalize graphene oxide (GO) during the in situ polymerization of phenol and formaldehyde. The hydrophilic and electrically insulating GO is converted to hydrophobic and electrically conductive graphene with phenol as the main reducing agent. Simultaneously, functionalization of GO is realized by the nucleophilic substitution reaction of the epoxide groups of GO with the hydroxyl groups of phenol in an alkali condition. Different from the insulating GO and phenol formaldehyde resin (PF) components, PF composites are electrically conductive due to the incidental reduction of GO during the in situ polymerization. The electrical conductivity of PF composite with 0.85 vol.% of GO is 0.20 S/m, nearly nine orders of magnitude higher than that of neat PF. Moreover, the efficient reduction and functionalization of GO endows the PF composites with high thermal stability and flexural properties. A striking increase in decomposition temperature is achieved with 2.3 vol.% of GO. The flexural strength and modulus of the PF composite with 1.7 vol.% GO are increased by 316.8% and 56.7%, respectively.
Co-reporter:Gongqing Tang, Zhi-Guo Jiang, Xiaofeng Li, Hao-Bin Zhang, Aravind Dasari, Zhong-Zhen Yu
Carbon 2014 Volume 77() pp:592-599
Publication Date(Web):October 2014
DOI:10.1016/j.carbon.2014.05.063
Three dimensional (3D) graphene aerogel was prepared by in situ reduction-assembly method. Paraphenylene diamine (PPD) was used as reducing and functionalizing agent of graphene oxide in an aqueous medium with ammonia. The synthesized 3D graphene-PPD aerogel has highly porous structure, low density, high electrical conductivity and good mechanical properties. Further, epoxy/aerogel composites were prepared by vacuum-assisted impregnation process, which exhibited good electrical conductivity and compressive properties.
Co-reporter:Zhixian He, Baoqing Zhang, Hao-Bin Zhang, Xin Zhi, Qihui Hu, Chen-Xi Gui, Zhong-Zhen Yu
Composites Science and Technology 2014 Volume 102() pp:176-182
Publication Date(Web):6 October 2014
DOI:10.1016/j.compscitech.2014.08.004
Styrene–maleic anhydride copolymer (SMA) was used as a compatibilizer to improve the interfacial interaction between graphene sheets and polystyrene matrix. SMA mediated graphene sheets are closely encapsulated by a polymer layer and uniformly dispersed compared to the graphene sheets without SMA. The presence of SMA not only improves the melt modulus and its frequency-independence, but also results in an earlier transition from liquid-like to solid-like, indicating the formation of a percolated conducting network at a low content of graphene with the assistance of SMA. Accordingly, the different frequency dependences of electrical conductivity also lead to a much lower threshold of 0.17 vol.% for SMA modified nanocomposites compared to 0.52 vol.% for the unmodified counterparts, further confirming the earlier formation of a graphene network in the matrix. The improved rheological and electrical properties of the polystyrene nanocomposites are attributed to the homogeneous dispersion of the graphene sheets and the enhanced interfacial interaction between the graphene sheets and the polystyrene matrix.
Co-reporter:Xue Pu, Hao-Bin Zhang, Xiaofeng Li, Chenxi Gui and Zhong-Zhen Yu
RSC Advances 2014 vol. 4(Issue 29) pp:15297-15303
Publication Date(Web):14 Mar 2014
DOI:10.1039/C4RA00518J
Graphene oxide was reduced and functionalized simultaneously by reacting with 3-aminopropyltriethoxysilane (APTES) without the use of conventional reducing agents. Silica was subsequently formed in situ on APTES functionalized graphene (A-graphene) sheets by a sol–gel approach using tetraethyl orthosilicate as the precursor of silica. The covalently bonded APTES on A-graphene enhances the compatibility between A-graphene and silica nanoparticles. The silica-coated A-graphene (S-graphene) sheets were incorporated to improve the thermal conductivity of epoxy. The presence of silica nanoparticles not only enhances the interfacial interaction between S-graphene and the epoxy matrix, but also alleviates the modulus mismatch between the fillers and the matrix and thus benefits the interfacial thermal conductance. The thermal conductivity of the epoxy nanocomposite with 8 wt% S-graphene is improved by 72% in comparison with that of neat epoxy, while the electrically insulating feature of the nanocomposite is retained.
Co-reporter:Hui-Ling Ma, Hao-Bin Zhang, Xiaofeng Li, Xin Zhi, Yong-Fei Liao, and Zhong-Zhen Yu
Industrial & Engineering Chemistry Research 2014 Volume 53(Issue 12) pp:4697-4703
Publication Date(Web):2017-2-22
DOI:10.1021/ie4039899
Electrically conductive polycarbonate (PC) nanocomposites are prepared by blending PC with thermally exfoliated graphene and p-phenylenediamine (PPD)-functionalized and reduced graphene oxide (GO-PPD). The filler dispersion in the PC matrix is evaluated with scanning electron microscopy, transmission electron microscopy, and rheological measurements. Compared to thermally exfoliated graphene, GO-PPD exhibits a better compatibility with the PC matrix and thus a more homogeneous dispersion due to the presence of PPD in GO-PPD. After being freely foamed with supercritical carbon dioxide as the foaming agent, the PC/GO-PPD nanocomposite foams show improved cell structures with higher cell density, smaller cell size, and more regular shapes; these should be attributed to the uniform dispersion of GO-PPD sheets in the matrix, which act as nucleation sites for foaming. Interestingly, the conducting network formed by GO-PPD sheets survives even after mold-limited foaming of PC/GO-PPD nanocomposites, and therefore the nanocomposite foams exhibit similar or even higher electrical conductivity in comparison to their solid counterparts.
Co-reporter:Juan Hu, Hao-Bin Zhang, Song Hong, Zhi-Guo Jiang, Chenxi Gui, Xiaofeng Li, and Zhong-Zhen Yu
Industrial & Engineering Chemistry Research 2014 Volume 53(Issue 6) pp:2270-2276
Publication Date(Web):January 16, 2014
DOI:10.1021/ie4035785
To simultaneously improve electrical conductivity and toughness of polyamide 6 (PA 6), carbon black (CB) nanoparticles and maleic anhydride grafted polyethylene–octene copolymer (POE-g-MA) were compounded with PA 6 by melt compounding, and the influences of CB and POE-g-MA components on the electrical conductivity and mechanical properties of PA 6 nanocomposites were investigated. The addition of CB improves the electrical conductivity and Young’s modulus of PA 6. With 40 wt % POE-g-MA and 15 wt % CB, the nanocomposite exhibits a high notched impact energy of 73.9 kJ/m2 and an electrical conductivity of 7.1 × 10–6 S/m. Interestingly, the presence of POE-g-MA reduces the electrical percolation threshold of the PA 6 nanocomposites due to the selective localization of CB in the PA 6 matrix. Compared to PA 6/CB binary nanocomposites, the ternary nanocomposites exhibit both higher electrical conductivity and supertoughness.
Co-reporter:Dong Yan, Xiaofeng Li, Yue Jiang, Hao-Bin Zhang, Bing-Bing Jia, Hui-Ling Ma, Zhong-Zhen Yu
Materials Letters 2014 Volume 118() pp:212-216
Publication Date(Web):1 March 2014
DOI:10.1016/j.matlet.2013.12.080
•Thermally conductive PF composites were prepared by compounding PF resin with carbon fillers.•Synergistic effect on thermal conductivity is achieved by replacing graphite with carbon fibers.•Carbon fibers provide higher thermal conductivity and better reinforcement than MWNTs.Thermally conductive phenol formaldehyde resin (PF)/graphite composites were prepared and the effects of a small amount of carbon fibers and multi-walled carbon nanotubes on the through-plane and in-plane conductivities of the composites were investigated. The use of graphite flakes increases the thermal conductivity of PF resin. The increase in in-plane thermal conductivity is much higher than that in through-plane thermal conductivity due to the layered structure of graphite. By replacing 10 wt% of graphite with carbon fibers, the through- and in-plane thermal conductivities of the PF composite are as high as 8.6 W/(mK) and 31.5 W/(mK), respectively. The partial replacement also improves the flexural properties of the composites.
Co-reporter:Gongqing Tang;Zhi-Guo Jiang;Xiaofeng Li
Chinese Journal of Polymer Science 2014 Volume 32( Issue 8) pp:975-985
Publication Date(Web):2014 August
DOI:10.1007/s10118-014-1488-8
Simultaneous functionalization and reduction of graphene oxide (GO) is realized by refluxing of GO suspension with polyetheramine (D2000) followed by thermal treatment at 120 °C. Compared to GO, the D2000-treated GO (GO-D2000) becomes hydrophobic, thermally stable and highly conductive with an electrical conductivity of 11 S/m, which is almost 8 orders of magnitude higher than that of GO. Due to the high conductivity and improved dispersion of GO-D2000, its epoxy nanocomposites exhibit a sharp transition from electrically insulating to conducting with a low percolation threshold of 0.71 vol%. With 3.6 wt% GO-D2000, the glass transition temperature of the epoxy nanocomposite is 27 K higher than that of neat epoxy.
Co-reporter:Gongqing Tang, Zhi-Guo Jiang, Xiaofeng Li, Hao-Bin Zhang, Song Hong, Zhong-Zhen Yu
Composites Part B: Engineering 2014 Volume 67() pp:564-570
Publication Date(Web):December 2014
DOI:10.1016/j.compositesb.2014.08.013
Simultaneous reduction and surface functionalization of graphene oxide (GO) was achieved by refluxing GO with a diamine, polyetheramine (D230) at 95 °C followed by thermal treatment at 120 °C. The D230-treated GO (GO-D230) exhibits a high electrical conductivity of 1.0 S/m, much higher than that of GO, due to the chemical and thermal reduction. The incorporation of GO-D230 significantly improves the electrical conductivity of epoxy, exhibiting a sharp transition from electrically insulating to conducting with a low percolation threshold of 0.78 vol%. With 2.7 vol% of GO-D230, the electrical conductivity of its epoxy nanocomposite is 1.0 × 10−4 S/m, nearly 11 orders of magnitude higher than that of neat epoxy; meanwhile, compared to the low Young’s modulus and tensile strength of the rubbery epoxy, those of the nanocomposite are increased by 536% and 269%, respectively.
Co-reporter:Xiu-Zhi Tang, Xiaofeng Li, Zongwei Cao, Jinglei Yang, Huan Wang, Xue Pu, Zhong-Zhen Yu
Carbon 2013 Volume 59() pp:93-99
Publication Date(Web):August 2013
DOI:10.1016/j.carbon.2013.02.058
A green and efficient approach for the synthesis of graphene decorated with silver nanoparticles is demonstrated by simultaneously reducing both graphene oxide (GO) sheets and silver ions with glucose as the reducing agent and poly(N-vinyl-2-pyrrolidone) (PVP) as the surface modifier. Different silver-containing materials are obtained by changing the synthesis temperature. The oxygen-containing groups of the substrate influence its decoration with the in situ formed silver nanoparticles. The combination of glucose and a silver–ammonia solution, as well as maintaining a good dispersion of GO by using PVP are crucial for the decoration of graphene with silver nanoparticles. The materials exhibit a distinct surface-enhanced Raman scattering effect.
Co-reporter:Yuxia Shen, Hao-Bin Zhang, Hongkun Zhang, Weijie Ren, Aravind Dasari, Guang-Shi Tang, Zhong-Zhen Yu
Carbon 2013 Volume 56() pp:132-138
Publication Date(Web):May 2013
DOI:10.1016/j.carbon.2012.12.088
Solvothermally reduced and functionalized graphene (SRFG) was obtained by refluxing graphene oxide in dimethyl formamide at 140 °C. The resultant simultaneous nitrogen-doping and presence of dangling bonds on SRFG prompted us to study the evolution of structural changes with refluxing time. It is shown that the removal of oxygen-containing functional groups leaves dangling bonds during the solvothermal reduction, which are responsible for the nitrogen-doping with longer refluxing time. The relationship between the defects of SRFGs and their lithium ion storage performances are also discussed.
Co-reporter:Hui-Ling Ma, Youwei Zhang, Qi-Hui Hu, Shunlun He, Xiaofeng Li, Maolin Zhai, Zhong-Zhen Yu
Materials Letters 2013 Volumes 102–103() pp:15-18
Publication Date(Web):July 2013
DOI:10.1016/j.matlet.2013.03.094
•The reduction of graphene oxide is realized with a green approach using glucose as a reducing agent.•The compatibility of the reduced graphene oxide (RGO) with PVA is improved by the use of PVP.•The tensile properties of PVA are greatly improved with the PVP-stabilized RGO.Poly(vinyl alcohol) (PVA) nanocomposite films with enhanced mechanical properties were prepared by solution blending of glucose-reduced graphene oxide (RGO) with aqueous solution of PVA. Poly(N-vinyl-2-pyrrolidone) (PVP) was selected as the surfactant to improve the stability of the aqueous suspension of RGO. With 0.7 wt% of PVP-stabilized RGO (P-RGO), the tensile strength of PVA increases from 105 MPa to 154 MPa and the Young's modulus increases from 3.3 GPa to 4.9 GPa. These substantial improvements are attributed to the good dispersion of P-RGO nanosheets in PVA matrix and the strong hydrogen-bonding interaction between P-RGO nanosheets and PVA macromolecular chains. P-RGO nanosheets were confirmed to be randomly dispersed in PVA matrix based on the modified Halpin-Tsai model.
Co-reporter:Dong Yan, Xiaofeng Li, Hui-Ling Ma, Xiu-Zhi Tang, Zhong Zhang, Zhong-Zhen Yu
Composites Part A: Applied Science and Manufacturing 2013 Volume 49() pp:35-41
Publication Date(Web):June 2013
DOI:10.1016/j.compositesa.2013.02.002
Multiwalled carbon nanotubes (MWNTs) were incorporated into polyamide 12 (PA12) and PA12/polyethylene-octene elastomer grafted with maleic anhydride (POE-g-MA) components by melt compounding. The addition of MWNTs improves electrical, dynamic mechanical and thermal properties of PA12. In the presence of 20 wt.% POE-g-MA, PA12/POE-g-MA/MWNT ternary nanocomposites exhibit substantially improved electrical conductivities as compared to PA12/MWNT binary nanocomposites with the same loading of MWNTs. The electrical conductivity shows 5–6 orders of magnitude increase in the percolation threshold region due to the volume exclusion effect of POE-g-MA. Variation of the compo unding sequence of the three components results in large difference in electrical conductivity of the ternary nanocomposites at the low loading of 2 wt.% MWNTs, while the difference becomes slight at high MWNT loading of 4 wt.%.
Co-reporter:Fang-Yuan Yuan, Hao-Bin Zhang, Xiaofeng Li, Xiao-Zeng Li, Zhong-Zhen Yu
Composites Part A: Applied Science and Manufacturing 2013 Volume 53() pp:137-144
Publication Date(Web):October 2013
DOI:10.1016/j.compositesa.2013.05.012
Tetrapod-shaped zinc oxide (T-ZnO) whiskers and boron nitride (BN) flakes were employed to improve the thermal conductivity of phenolic formaldehyde resin (PF). A striking synergistic effect on thermal conductivity of PF was achieved. The in-plane thermal conductivity of the PF composite is as high as 1.96 W m−1 K−1 with 30 wt.% BN and 30 wt.% T-ZnO, which is 6.8 times higher than that of neat PF, while its electrical insulation is maintained. With 30 wt.% BN and 30 wt.% T-ZnO, the flexural strength of the composite is 312.9% higher than that of neat PF, and 56.2% higher that of the PF composite with 60 wt.% BN. The elongation at break is also improved by 51.8% in comparison with that of the composite with 60 wt.% BN. Such a synergistic effect results from the bridging of T-ZnO whiskers between BN flakes facilitating the formation of effective thermal conductance network within PF matrix.
Co-reporter:Youwei Zhang, Hui-Ling Ma, Qilu Zhang, Jing Peng, Jiuqiang Li, Maolin Zhai and Zhong-Zhen Yu
Journal of Materials Chemistry A 2012 vol. 22(Issue 26) pp:13064-13069
Publication Date(Web):10 May 2012
DOI:10.1039/C2JM32231E
We demonstrate a facile and environmentally friendly approach to prepare well-dispersed graphene sheets by γ-ray induced reduction of a graphene oxide (GO) suspension in N,N-dimethyl formamide (DMF) at room temperature. GO is reduced by the electrons generated from the radiolysis of DMF under γ-ray irradiation. The reduced GO by γ-ray irradiation (G-RGO) can be re-dispersed in many organic solvents, and the resulting suspensions are stable for two weeks due to the stabilization of N(CH3)2+ groups on G-RGO. Additionally, G-RGO is efficient in improving the conductivity of polystyrene (PS). Its PS nanocomposites exhibit a sharp transition from electrically insulating to conducting with a low percolation threshold of 0.24 vol% and a high electrical conductivity of 45 S m−1 is obtained with only 2.3 vol% of G-RGO. The superior electrical conductivity is attributed to the uniform dispersion of the G-RGO sheets in the PS matrix.
Co-reporter:Ruiqiong Liu, Songmiao Liang, Xiu-Zhi Tang, Dong Yan, Xiaofeng Li and Zhong-Zhen Yu
Journal of Materials Chemistry A 2012 vol. 22(Issue 28) pp:14160-14167
Publication Date(Web):21 May 2012
DOI:10.1039/C2JM32541A
Polyacrylamide (PAM)/graphene oxide (GO) nanocomposite hydrogels (PGH) with GO nanosheets as cross-linkers were synthesized via in situ free radical polymerization of acrylamide in an aqueous suspension of GO. The tensile properties of the hydrogels were investigated in terms of type and content of cross-linkers. Compared to conventional PAM hydrogels (PBH) cross-linked chemically with N,N′-methylenebisacrylamide, PGH exhibits high tensile strength, high toughness and especially a large elongation at break. The tensile strength of PGH is about 4.5 times higher than that of PBH, and the elongation at break is over 3000%, nearly one order higher than that of PBH even when the content of GO is only 0.0079 wt%. By analyzing the cross-linked structure of PGH and the theoretical calculation on the number of cross-linked polymer chains per unit volume of gels, a structure model was thus proposed.
Co-reporter:Hui-Ling Ma, Youwei Zhang, Qi-Hui Hu, Dong Yan, Zhong-Zhen Yu and Maolin Zhai
Journal of Materials Chemistry A 2012 vol. 22(Issue 13) pp:5914-5916
Publication Date(Web):22 Feb 2012
DOI:10.1039/C2JM00145D
Ethylenediamine-reduced graphene oxide (ED-RGO) sheets were prepared by simple refluxing of graphene oxide (GO) solution with ethylenediamine (ED), which effectively reduced toxic Cr(VI) to less toxic Cr(III) by an indirect reduction mechanism with the assistance of π electrons on the carbocyclic six-membered ring of ED-RGO.
Co-reporter:Hui-Ling Ma, Hao-Bin Zhang, Qi-Hui Hu, Wen-Juan Li, Zhi-Guo Jiang, Zhong-Zhen Yu, and Aravind Dasari
ACS Applied Materials & Interfaces 2012 Volume 4(Issue 4) pp:1948
Publication Date(Web):March 15, 2012
DOI:10.1021/am201654b
A facile and efficient approach was developed to simultaneously functionalize and reduce graphene oxide (GO) with p-phenylene diamine (PPD) by simple refluxing. This was possible by the nucleophilic substitution reaction of epoxide groups of GO with amine groups of PPD aided by NH3 solution. As a consequence, electrical conductivity of GO-PPD increased to 2.1 × 102 S/m, which was nearly 9 orders of magnitude higher than that of GO. Additionally, after the incorporation of GO-PPD in polystyrene (PS), the composites exhibited a sharp transition from electrically insulating to conducting behavior with a low percolation threshold of ∼0.34 vol %, which was attributed to the improved dispersion and the reduction of GO-PPD. Thermal stability of the PS/GO-PPD composite was also ∼8 °C higher than that of PS.Keywords: chemical reduction; electrical conductivity; graphene oxide; p-phenylene diamine; polystyrene; thermal stability;
Co-reporter:Dong Yan, Hao-Bin Zhang, Yu Jia, Juan Hu, Xian-Yong Qi, Zhong Zhang, and Zhong-Zhen Yu
ACS Applied Materials & Interfaces 2012 Volume 4(Issue 9) pp:4740
Publication Date(Web):August 13, 2012
DOI:10.1021/am301119b
Electrically conductive polyamide 12 (PA12)/graphene binary nanocomposites with a low percolation threshold of 0.3 vol % were prepared by melt compounding. A rapid increase in electrical conductivity from 2.8 × 10–14 S/m of PA12 to 6.7 × 10–2 S/m was achieved with ∼1.38 vol % graphene. It is shown that graphene sheets were homogeneously dispersed in PA12 matrix. Furthermore, polyethylene-octene rubber grafted with maleic anhydride (POE-g-MA) was used to further enhance the electrical conductivity of PA12/graphene nanocomposites. Three compounding sequences were adopted to tailor the microstructure and properties of the ternary nanocomposites. Both highest electrical conductivity and storage modulus were obtained when most graphene sheets were located in PA12 matrix rather than in POE-g-MA phase.Keywords: electrical conductivity; graphene; melt compounding; nanocomposites; polyamide 12; selective localization;
Co-reporter:Hao-Bin Zhang, Wen-Ge Zheng, Qing Yan, Zhi-Guo Jiang, Zhong-Zhen Yu
Carbon 2012 Volume 50(Issue 14) pp:5117-5125
Publication Date(Web):November 2012
DOI:10.1016/j.carbon.2012.06.052
Graphene sheets with different oxygen contents were prepared to functionalize the electrically insulating polymethylmethacrylate (PMMA). The influences of surface chemistry of graphene on rheological, electrical and electromagnetic interference (EMI) shielding properties of its PMMA composites were investigated. The appearance of frequency-independent storage modulus at low frequency suggests a solid-like viscoelastic behavior and the formation of an interconnected network of graphene in the matrix. Due to the favorable interfacial interactions arising from polarity matching, the graphene with a C/O ratio of 13.2 (graphene-13.2) shows a better dispersion in PMMA than those with lower C/O ratios, and thus its PMMA composites exhibit lower rheological and electrical percolation thresholds. The EMI shielding properties of the graphene/PMMA composites exhibit similar dependence on the oxygen content of graphene. A high EMI shielding effectiveness of ∼30 dB was obtained for the PMMA composite with 4.2 vol.% of graphene-13.2 with microwave absorption as the dominant EMI shielding mechanism.
Co-reporter:Yuxia Shen, Tao Jing, Weijie Ren, Jiewei Zhang, Zhi-Guo Jiang, Zhong-Zhen Yu, Aravind Dasari
Composites Science and Technology 2012 Volume 72(Issue 12) pp:1430-1435
Publication Date(Web):23 July 2012
DOI:10.1016/j.compscitech.2012.05.018
Graphene oxide (GO) was reduced with biocompatible glucose and polyvinylpyrrolidone (PVP) and incorporated in polylactic acid (PLA). The thermal reduction of GO during the compression molding of PLA was also studied to delineate the reduction efficiencies from thermal and chemical processes. Results indicate that glucose is more effective in the reduction of GO (rGO-g) with a much higher electrical conductivity than PVP and thermally treated GO. Even rGO-g was also highly efficient in improving the electrical conductivity of PLA. The composite with ∼1.25 vol.% of rGO-g exhibited a high conductivity of ∼2.2 S/m due to the chemical reduction of GO with glucose and the thermal reduction of rGO-g during the compression molding process.
Co-reporter:Dan Zheng, Guangshi Tang, Hao-Bin Zhang, Zhong-Zhen Yu, Fazel Yavari, Nikhil Koratkar, Szu-Hui Lim, Mun-Wai Lee
Composites Science and Technology 2012 Volume 72(Issue 2) pp:284-289
Publication Date(Web):18 January 2012
DOI:10.1016/j.compscitech.2011.11.014
Electrically conductive and thermally stable polyamide 6 (PA 6) nanocomposites were prepared through one-step in situ polymerization of ε-caprolactam monomer in the presence of electrically insulating and thermally unstable graphene oxide (GO) nanosheets. These nanocomposites show a low percolation threshold of ∼0.41 vol.% and high electrical conductivity of ∼0.028 S/m with only ∼1.64 vol.% of GO. Thermogravimetric analysis and X-ray photoelectron spectroscopy results of GO before and after thermal treatment at the polymerization temperature indicate that GO was reduced in situ during the polymerization process. X-ray diffraction patterns and scanning electron microscopy observation confirm the exfoliation of the reduced graphene oxide (RGO) in the PA 6 matrix. The low percolation threshold and high electrical conductivity are attributed to the large aspect ratio, high specific surface area and uniform dispersion of the RGO nanosheets in the matrix. In addition, although GO has a poor thermal stability, its PA 6 nanocomposite is thermally stable with a satisfactory thermal stability similar to those of neat PA 6 and PA 6/graphene nanocomposite. Such a one-step in situ polymerization and thermal reduction method shows significant potential for the mass production of electrically conductive polymer/RGO nanocomposites.
Co-reporter:Feifei Sheng;Xiu-Zhi Tang;Sheng Zhang;Xuejia Ding;Zhaobin Qiu
Polymers for Advanced Technologies 2012 Volume 23( Issue 2) pp:137-142
Publication Date(Web):
DOI:10.1002/pat.1833
Abstract
A thermally stable imidazolium organoclay was synthesized to improve the flame retardancy performance of polyamide 66 (PA 66). To enhance flame retardancy of the PA 66/organoclay nanocomposite, the thermally stable organoclay was coated with monomethylol melamine (MMM) before melt-compounding with PA 66. Transmission electron microscopy and X-ray diffraction results confirmed the partial exfoliation of the organoclay in the PA 66 matrix. The use of the thermally stable organoclay did not affect the thermal stability of PA 66. The cone calorimeter results showed that the PA 66/orgnaoclay nanocomposite exhibited a greatly reduced heat release rate and a longer ignition time. However, the PA 66/organoclay binary nanocomposite had no rating in the UL-94 vertical burning test because it did not extinguish until the entire polymer component was burnt. The PA 66 nanocomposite with 15 wt% of MMM-coated organoclay performed better in the ignition resistance test than the PA 66/organoclay nanocomposite containing 15 wt% of melamine. Copyright © 2011 John Wiley & Sons, Ltd.
Co-reporter:Hao-Bin Zhang, Ji-Wen Wang, Qing Yan, Wen-Ge Zheng, Cao Chen and Zhong-Zhen Yu
Journal of Materials Chemistry A 2011 vol. 21(Issue 14) pp:5392-5397
Publication Date(Web):28 Feb 2011
DOI:10.1039/C1JM10099H
We report a vacuum-assisted method for thermal exfoliation and in situreduction of graphite oxide in large quantity at a temperature as low as 135 °C. The resulting graphene sheets contain only few-layered sheets with an average thickness of 0.9 nm, and their specific surface area (758 m2 g−1) is comparable to that of conventional graphene generated at 1050 °C at atmospheric pressure (700 m2 g−1). The in situ thermal reduction during the exfoliation process was confirmed by the increased C/O atomic ratio compared to that of graphite oxide. The restoration of the graphitic sp2 network makes it highly efficient in improving the electrical conductivity of polymers at a low graphene loading.
Co-reporter:Xiu-Zhi Tang, Zongwei Cao, Hao-Bin Zhang, Jing Liu and Zhong-Zhen Yu
Chemical Communications 2011 vol. 47(Issue 11) pp:3084-3086
Publication Date(Web):04 Feb 2011
DOI:10.1039/C0CC05613H
A rapid and efficient one-step approach to prepare graphene–Ag nanocomposites by simultaneous reduction of graphene oxide (GO) and silver ions with formaldehyde as the reducing agent within several minutes was demonstrated.
Co-reporter:Xian-Yong Qi, Dong Yan, Zhiguo Jiang, Ya-Kun Cao, Zhong-Zhen Yu, Fazel Yavari, and Nikhil Koratkar
ACS Applied Materials & Interfaces 2011 Volume 3(Issue 8) pp:3130
Publication Date(Web):July 11, 2011
DOI:10.1021/am200628c
We compared the electrical conductivity of multiwalled-carbon-nanotube/polystyrene and graphene/polystyrene composites. The conductivity of polystyrene increases from ∼6.7 × 10–14 to ∼3.49 S/m, with an increase in graphene content from ∼0.11 to ∼1.1 vol %. This is ∼2–4 orders of magnitude higher than for multiwalled-carbon-nanotube/polystyrene composites. Furthermore, we show that the conductivity of the graphene/polystyrene system can be significantly enhanced by incorporation of polylactic acid. The volume-exclusion principle forces graphene into the polystyrene-rich regions (selective localization) and generates ∼4.5-fold decrease in its percolation threshold from ∼0.33 to ∼0.075 vol %.Keywords: electrical conductivity; graphene; percolation threshold; polylactic acid; polystyrene; selective localization; volume exclusion;
Co-reporter:Hao-Bin Zhang, Qing Yan, Wen-Ge Zheng, Zhixian He, and Zhong-Zhen Yu
ACS Applied Materials & Interfaces 2011 Volume 3(Issue 3) pp:918
Publication Date(Web):March 2, 2011
DOI:10.1021/am200021v
Functional polymethylmethacrylate (PMMA)/graphene nanocomposite microcellular foams were prepared by blending of PMMA with graphene sheets followed by foaming with subcritical CO2 as an environmentally benign foaming agent. The addition of graphene sheets endows the insulating PMMA foams with high electrical conductivity and improved electromagnetic interference (EMI) shielding efficiency with microwave absorption as the dominant EMI shielding mechanism. Interestingly, because of the presence of the numerous microcellular cells, the graphene−PMMA foam exhibits greatly improved ductility and tensile toughness compared to its bulk counterpart. This work provides a promising methodology to fabricate tough and lightweight graphene−PMMA nanocomposite microcellular foams with superior electrical and EMI shielding properties by simultaneously combining the functionality and reinforcement of the graphene sheets and the toughening effect of the microcellular cells.Keywords: electrical conductivity; electromagnetic interference shielding; graphene; microcellular foam; polymethylmethacrylate
Co-reporter:Wenjuan Li, Xiu-Zhi Tang, Hao-Bin Zhang, Zhi-Guo Jiang, Zhong-Zhen Yu, Xu-Sheng Du, Yiu-Wing Mai
Carbon 2011 Volume 49(Issue 14) pp:4724-4730
Publication Date(Web):November 2011
DOI:10.1016/j.carbon.2011.06.077
Simultaneous surface functionalization and reduction of graphene oxide (GO) was realized by simple refluxing of GO with octadecylamine (ODA) without the use of any reducing agents. The presence of the long octadecyl chain made the hydrophilic GO hydrophobic, evidenced by the selective dispersion of the ODA-functionalized GO (GO–ODA) in chloroform solvent rather than in water. Interestingly, different from the insulating GO, GO–ODA became electrically conductive due to the reduction in the presence of ODA. The electrical conductivity of GO–ODA was further increased by incidental thermal reduction during the compression-molding of its polystyrene (PS) composites at 210 °C, which exhibited a sharp transition from electrically insulating to conducting with a low percolation threshold. The high conductivity of the PS/GO–ODA composites is attributed to the improved dispersion and the reduction of GO–ODA in comparison with GO.
Co-reporter:Xiu-Zhi Tang, Wenjuan Li, Zhong-Zhen Yu, Mohammad A. Rafiee, Javad Rafiee, Fazel Yavari, Nikhil Koratkar
Carbon 2011 Volume 49(Issue 4) pp:1258-1265
Publication Date(Web):April 2011
DOI:10.1016/j.carbon.2010.11.044
In this study 2-amino-4,6-didodecylamino-1,3,5-triazine (ADDT) was synthesized from cyanuric chloride and covalently functionalized onto graphene oxide nanosheets. The chemical structure of the alkylated melamine and the functionalized graphene oxide (GO) nanosheets were characterized with 1H NMR, FT-IR, XPS, TGA and TEM. The results indicate that two chlorine atoms on the triazine ring of cyanuric chloride were substituted by two long alkyl chains. Covalent functionalization of ADDT onto the graphene oxide nanosheets was confirmed with both FT-IR and XPS results. The reduced mass loss rate along with enhanced residue formation (TGA results) indicates significant improvement in thermal stability for GO-ADDT compared to GO. Moreover good solubility of GO-ADDT in organic solvents suggests the potential of GO-ADDT as a nanoadditive for polymeric systems.
Co-reporter:Chang-Rong Yu, Da-Ming Wu, Ying Liu, Hui Qiao, Zhong-Zhen Yu, Aravind Dasari, Xu-Sheng Du, Yiu-Wing Mai
Composites Science and Technology 2011 Volume 71(Issue 15) pp:1706-1712
Publication Date(Web):24 October 2011
DOI:10.1016/j.compscitech.2011.07.022
Functional polypropylene (PP) nanocomposites were prepared by melt compounding with multiwalled carbon nanotubes (MWNT) as the electrically conductive component and barium titanate (BT) spherical nanoparticles as the ferroelectric component. To make PP electrically conductive, more than 3 wt.% MWNT is required. Surface modification of either MWNT or BT with titanate coupling agent further improves the electrical conductivity of the PP/MWNT/BT ternary nanocomposites. Interestingly, by modifying both MWNT and BT, 2 wt.% MWNT are sufficient to make the ternary nanocomposite electrically conductive. In addition, the incorporation of MWNT greatly increases the dielectric permittivity of PP/BT nanocomposites. However, to retain a low dielectric loss, the MWNT loading should be slightly less than the percolation threshold of the nanocomposites. The improved electrical conductivity and dielectric properties make the ternary nanocomposites attractive in practical applications.Highlights► Surface modification further improves the conductivity of PP/MWNT/BT nanocomposites. ► The reduced viscosity and volume-exclusion are beneficial for improving conductivity. ► The addition of MWNT increases the dielectric permittivity of PP/BT nanocomposites.
Co-reporter:Zhou Wang;Xiu-zhi Tang 于中振;Peng Guo
Chinese Journal of Polymer Science 2011 Volume 29( Issue 3) pp:368-376
Publication Date(Web):2011 May
DOI:10.1007/s10118-011-1037-7
Graphene oxide was prepared by ultrasonication of completely oxidized graphite and used to improve the flame retardancy of epoxy. The epoxy/graphene oxide nanocomposite was studied in terms of exfoliation/dispersion, thermal stability and flame retardancy. X-ray diffraction and transmission electron microscopy confirmed the exfoliation of the graphene oxide nanosheets in epoxy matrix. Cone calorimeter measurements showed that the time to ignition of the epoxy/graphene oxide nanocomposite was longer than that of neat epoxy. The heat release rate curve of the nanocomposite was broadened compared to that of neat epoxy and the peak heat release rate decreased as well.
Co-reporter:Yingjuan Huang, Yawei Qin, Yong Zhou, Hui Niu, Zhong-Zhen Yu and Jin-Yong Dong
Chemistry of Materials 2010 Volume 22(Issue 13) pp:4096
Publication Date(Web):June 15, 2010
DOI:10.1021/cm100998e
This paper reports the first example of preparation of polypropylene/graphene oxide (PP/GO) nanocomposites via in situ Ziegler−Natta polymerization. A Mg/Ti catalyst species was incorporated into GO via surface functional groups including −OH and −COOH, giving a supported catalyst system primarily structured by nanoscale, predominantly single GO sheet. Subsequent propylene polymerization led to the in situ formation of PP matrix, which was accompanied by the nanoscale exfoliation of GO, as well as its gradual dispersion. Morphological examination of the ultimate PP/GO nanocomposites by TEM and SEM techniques revealed effective dispersion in nanoscale of GO in PP matrix. High electrical conductivity was discovered with thus prepared PP/GO nanocomposites; for example, at a GO loading of 4.9 wt %, σc was measured at 0.3 S·m−1.
Co-reporter:F. Yavari, M. A. Rafiee, J. Rafiee, Z.-Z. Yu, and N. Koratkar
ACS Applied Materials & Interfaces 2010 Volume 2(Issue 10) pp:2738
Publication Date(Web):September 23, 2010
DOI:10.1021/am100728r
We report the synthesis and fatigue characterization of fiberglass/epoxy composites with various weight fractions of graphene platelets infiltrated into the epoxy resin as well as directly spray-coated on to the glass microfibers. Remarkably only ∼0.2% (with respect to the epoxy resin weight and ∼0.02% with respect to the entire laminate weight) of graphene additives enhanced the fatigue life of the composite in the flexural bending mode by up to 1200-fold. By contrast, under uniaxial tensile fatigue conditions, the graphene fillers resulted in ∼3−5-fold increase in fatigue life. The fatigue life increase (in the flexural bending mode) with graphene additives was ∼1−2 orders of magnitude superior to those obtained using carbon nanotubes. In situ ultrasound analysis of the nanocomposite during the cyclic fatigue test suggests that the graphene network toughens the fiberglass/epoxy-matrix interface and prevents the delamination/buckling of the glass microfibers under compressive stress. Such fatigue-resistant hierarchical materials show potential to improve the safety, reliability, and cost effectiveness of fiber-reinforced composites that are increasingly the material of choice in the aerospace, automotive, marine, sports, biomedical, and wind energy industries.Keywords: carbon nanotubes; fatigue life; graphene; hierarchical nanocomposites
Co-reporter:Szu-Hui Lim, Zhong-Zhen Yu, Yiu-Wing Mai
Composites Science and Technology 2010 Volume 70(Issue 13) pp:1994-2002
Publication Date(Web):15 November 2010
DOI:10.1016/j.compscitech.2010.07.023
Tensile tests were conducted on nylon 6/organoclay nanocomposites, with and without POE-g-MA rubber particles, over a range of temperatures and strain rates 10−4–10−1 s−1. It was shown that the 0.2% offset yield strength varied with both temperature and strain rate which could be described by the Eyring equation thus providing results on the activation energy and activation volume for the physical processes involved. In addition, their tensile deformation mechanisms were characterized using the tensile dilatometry technique to differentiate the dilatational processes (e.g., voiding/debonding caused by the organoclay and rubber particles or matrix) and shear yielding (e.g., matrix with zero volume change). Dilatometric responses indicated that the presence of POE-g-MA rubber particles did not alter the shear deformation mode of neat nylon 6. In contrast, the presence of organoclay layers changed the tensile yield deformation behavior of nylon 6 matrix from dominant shear yielding to combined shear yield plus dilatation associated with delaminations of nanoclay platelets. In nylon 6/organoclay/POE-g-MA ternary nanocomposite, the volume strain response indicated that the POE-g-MA rubber particles promoted shear deformation and suppressed delamination of the organoclay layers. Supports for the deformation mechanisms deduced from the tensile dilatometry tests were corroborated by optical microscopy and transmission electron microscopy micrographs of the studied materials.
Co-reporter:Szu-Hui Lim, Aravind Dasari, Gong-Tao Wang, Zhong-Zhen Yu, Yiu-Wing Mai, Qiang Yuan, Songlin Liu, Ming Shyan Yong
Composites Part B: Engineering 2010 Volume 41(Issue 1) pp:67-75
Publication Date(Web):January 2010
DOI:10.1016/j.compositesb.2009.03.006
This study focuses on achieving high stiffness/strength and high fracture toughness in nylon 6/organoclay nanocomposites prepared via melt compounding by incorporating a maleic anhydride grafted polyethylene–octene elastomer (POE-g-MA) as a toughening agent. Mechanical test results indicated that the ternary nanocomposites exhibited higher stiffness than nylon 6/POE-g-MA binary blends at any given POE-g-MA content. More importantly, the brittle–ductile transition of nylon 6/POE-g-MA blends was not impaired in the presence of organoclay for the compositions prepared in this study. TEM analysis shows that organoclay layers and elastomer particles were dispersed separately in nylon 6 matrix. In the binary nanocomposite, no noticeable plastic deformation was observed around the crack tip. In the ternary nanocomposites, the presence of organoclay in the matrix provided maximum reinforcement to the polymer, while their absence in the elastomer particles allowed the latter to promote high fracture toughness via particle cavitation and subsequent matrix shear yielding. The partially exfoliated clay layers also delaminated and hence, adding to the total toughness of the nanocomposites.
Co-reporter:Hao-Bin Zhang, Wen-Ge Zheng, Qing Yan, Yong Yang, Ji-Wen Wang, Zhao-Hui Lu, Guo-Ying Ji, Zhong-Zhen Yu
Polymer 2010 Volume 51(Issue 5) pp:1191-1196
Publication Date(Web):2 March 2010
DOI:10.1016/j.polymer.2010.01.027
Graphene nanosheets were prepared by complete oxidation of pristine graphite followed by thermal exfoliation and reduction. Polyethylene terephthalate (PET)/graphene nanocomposites were prepared by melt compounding. Transmission electron microscopy observation indicated that graphene nanosheets exhibited a uniform dispersion in PET matrix. The incorporation of graphene greatly improved the electrical conductivity of PET, resulting in a sharp transition from electrical insulator to semiconductor with a low percolation threshold of 0.47 vol.%. A high electrical conductivity of 2.11 S/m was achieved with only 3.0 vol.% of graphene. The low percolation threshold and superior electrical conductivity are attributed to the high aspect ratio, large specific surface area and uniform dispersion of the graphene nanosheets in PET matrix.
Co-reporter:Aravind Dasari, Qing-Xin Zhang, Zhong-Zhen Yu and Yiu-Wing Mai
Macromolecules 2010 Volume 43(Issue 13) pp:5734-5739
Publication Date(Web):June 2, 2010
DOI:10.1021/ma100633y
This paper deals with a novel concept of induction of well-distributed submicrometer voids in polypropylene (PP) and PP/CaCO3 nanocomposites during processing to alleviate their brittleness without sacrificing Young’s modulus and yield strength. The role of these voids in initiating/participating in the plastic deformation processes during tensile and double-notch four-point-bend (DN-4-PB) tests is investigated. It is shown that the voids act in a similar way as the cavitated rubber particles in rubber-toughened polymer systems; that is, plastic growth (of the pre-existent voids) in the PP matrix occurs upon deformation and subsequently triggers large plastic deformation of the surrounding matrix in the form of isolated and domainlike craze structures.
Co-reporter:Aravind Dasari, Zhong-Zhen Yu, Yiu-Wing Mai
Polymer 2009 50(16) pp: 4112-4121
Publication Date(Web):
DOI:10.1016/j.polymer.2009.06.026
Co-reporter:Aravind Dasari, Zhong-Zhen Yu, Yiu-Wing Mai, Guipeng Cai, Huaihe Song
Polymer 2009 50(6) pp: 1577-1587
Publication Date(Web):
DOI:10.1016/j.polymer.2009.01.050
Co-reporter:Aravind Dasari, Zhong-Zhen Yu, Yiu-Wing Mai
Materials Science and Engineering: R: Reports 2009 63(2) pp: 31-80
Publication Date(Web):15 January 2009
DOI:10.1016/j.mser.2008.10.001
It is realized that the addition of a small percentage of rigid nanoparticles to polymers significantly improves many of their mechanical properties, especially stiffness and strength. Such improvements are often attributed to the availability of large numbers of nanoparticles with huge interfacial areas compared to their macro- and micro-scale counterparts. In particular, from the tribological viewpoint, the small size of nanoparticles with homogenous dispersion in the matrix and good interfacial adhesion between nanoparticles and matrix are thought to be necessary requirements for a polymer nanocomposite. Material removal will be less since the nano-additives have similar sizes to the segments of surrounding polymer chains. Despite these positive effects due to the addition of nanoparticles, there are still some critical questions that are unanswered. Here, we review the fundamentals, recent progress and advances that have been made on the tribological aspects of polymer nanocomposites, particularly focusing on their wear (in dry sliding and unlubricated conditions) and scratch damage. The review shows that (a) it is not valid to assume that nano-fillers always improve wear/scratch (and friction) properties; and (b) material properties like modulus, hardness, fracture toughness or extent of wear rate or scratch penetration depth are not the sole indicators to compare and/or rank candidate materials. Several facets of wear/scratching or material response to the sliding processes require thorough understanding in order to determine parameters that control the surface integrity and material removal from polymer nanocomposites. This review also shows the apparent contradictions and false impressions on several material systems in many studies owing to poor characterizations of polymer nanocomposites and lack of quantitative descriptions of the observed phenomena.
Co-reporter:Yue Jiang, Renhui Sun, Hao-Bin Zhang, Peng Min, Dongzhi Yang, Zhong-Zhen Yu
Composites Part A: Applied Science and Manufacturing (March 2017) Volume 94() pp:
Publication Date(Web):March 2017
DOI:10.1016/j.compositesa.2016.12.009
Graphene-coated tetrapod ZnO whisker (T-ZnO) hybrids are fabricated by chemical modification of T-ZnO with an aminosilane, covalent coating with graphene oxide (GO) sheets, and reduction of the GO component by UV irradiation or thermal annealing. Compared to the moderately reduced hybrid by UV irradiation, the thermally annealed hybrid at 1000 °C (TGO1000@T-ZnO) is highly efficient in improving both thermal and electrical conductivities of epoxy. A high thermal conductivity of 5.06 W/(m K) is achieved for the epoxy composite with 65 vol.% TGO1000@T-ZnO hybrid. The epoxy composite with 65 vol.% TGO1000@T-ZnO also exhibits a high electrical conductivity of 27.2 S/m due to the efficiently formed electrically conducting network with only ∼4 wt.% well-distributed TGO sheets that are coated on T-ZnO substrates. The excellent thermal and electrical conductivities are attributed to the efficient conductance pathways formed by the skeleton of ZnO whiskers and the enhanced phonon and electron transfers by TGO sheets.
Co-reporter:Xiu-Zhi Tang, Zongwei Cao, Hao-Bin Zhang, Jing Liu and Zhong-Zhen Yu
Chemical Communications 2011 - vol. 47(Issue 11) pp:NaN3086-3086
Publication Date(Web):2011/02/04
DOI:10.1039/C0CC05613H
A rapid and efficient one-step approach to prepare graphene–Ag nanocomposites by simultaneous reduction of graphene oxide (GO) and silver ions with formaldehyde as the reducing agent within several minutes was demonstrated.
Co-reporter:Chen-Xi Gui, Shu-Meng Hao, Yuan Liu, Jin Qu, Cheng Yang, Yunhua Yu, Qian-Qian Wang and Zhong-Zhen Yu
Journal of Materials Chemistry A 2015 - vol. 3(Issue 32) pp:NaN16559-16559
Publication Date(Web):2015/07/03
DOI:10.1039/C5TA03408F
Layered nickel silicate provides massive interlayer space similar to graphite for the insertion and extraction of lithium ions and sodium ions; however, the poor electrical conductivity limits its electrochemical applications in energy storage devices. Herein, carbon nanotube@layered nickel silicate (CNT@NiSiOx) coaxial nanocables with flexible nickel silicate nanosheets grown on conductive carbon nanotubes (CNTs) are synthesized by a mild hydrothermal method. CNTs serve as conductive cables to improve the electron transfer performance of nickel silicate nanosheets, resulting in reduced contact and charge-transfer resistances. In addition to a high specific surface area, short ion diffusion distance and good electrical conductivity, one-dimensional coaxial nanocables have a stable structure to sustain volume change and avoid structure destruction during the charge–discharge process. As an anode material for lithium storage, the first cycle charge capacity of the CNT@NiSiOx nanocables reaches 770 mA h g−1 with the first cycle coulombic efficiency as high as 71.5%. Even after 50 cycles, the charge capacity still reaches 489 mA h g−1 at a current density of 50 mA g−1, which is nearly 87% and 360% higher than those of the NiSiOx/CNT mixture and nickel silicate nanotube, respectively. As anode materials for sodium storage, the coaxial nanocables exhibit a high initial charge capacity of 576 mA h g−1, which even retains 213 mA h g−1 at 20 mA g−1 after 16 cycles.
Co-reporter:Xin Qi, Jin Qu, Hao-Bin Zhang, Dongzhi Yang, Yunhua Yu, Cheng Chi and Zhong-Zhen Yu
Journal of Materials Chemistry A 2015 - vol. 3(Issue 30) pp:NaN15504-15504
Publication Date(Web):2015/06/16
DOI:10.1039/C5TA03087K
We report a facile and efficient approach to prepare graphene and FeCl3-intercalated few-layer graphene (FeCl3-FLG) with stage 1 FeCl3-graphite intercalation compounds (GICs) as a precursor by a non-oxidation process. The enlarged interlayer spacing by the intercalation of FeCl3 greatly weakens the interaction among graphite sheets and thus facilitates the exfoliation of FeCl3-GICs. By ultrasonic treatment, FeCl3-GICs are well exfoliated to graphene sheets (<2 nm) with a high yield of 100%, while the ultrasonication of pristine graphite is less efficient with a low yield (about 32%) of graphene sheets. By simply controlling the sonication time, FeCl3-FLG consisting of graphene sheets and sandwiched FeCl3 is also prepared, which exhibits a high capacity of 989 mA h g−1 after 50 cycles, fairly higher than that of the sonicated graphite (503 mA h g−1) and the theoretical value of graphite (372 mA h g−1). Furthermore, FeCl3-FLG still retains a reversible capacity as high as 539 mA h g−1 even at a current density of 1000 mA g−1. Therefore, the high reversible capacity, remarkable cycling stability and superior capability make FeCl3-FLG promising as anode materials for large-scale and high-capacity lithium ion batteries.
Co-reporter:Hui-Ling Ma, Youwei Zhang, Qi-Hui Hu, Dong Yan, Zhong-Zhen Yu and Maolin Zhai
Journal of Materials Chemistry A 2012 - vol. 22(Issue 13) pp:NaN5916-5916
Publication Date(Web):2012/02/22
DOI:10.1039/C2JM00145D
Ethylenediamine-reduced graphene oxide (ED-RGO) sheets were prepared by simple refluxing of graphene oxide (GO) solution with ethylenediamine (ED), which effectively reduced toxic Cr(VI) to less toxic Cr(III) by an indirect reduction mechanism with the assistance of π electrons on the carbocyclic six-membered ring of ED-RGO.
Co-reporter:Youwei Zhang, Hui-Ling Ma, Qilu Zhang, Jing Peng, Jiuqiang Li, Maolin Zhai and Zhong-Zhen Yu
Journal of Materials Chemistry A 2012 - vol. 22(Issue 26) pp:NaN13069-13069
Publication Date(Web):2012/05/10
DOI:10.1039/C2JM32231E
We demonstrate a facile and environmentally friendly approach to prepare well-dispersed graphene sheets by γ-ray induced reduction of a graphene oxide (GO) suspension in N,N-dimethyl formamide (DMF) at room temperature. GO is reduced by the electrons generated from the radiolysis of DMF under γ-ray irradiation. The reduced GO by γ-ray irradiation (G-RGO) can be re-dispersed in many organic solvents, and the resulting suspensions are stable for two weeks due to the stabilization of N(CH3)2+ groups on G-RGO. Additionally, G-RGO is efficient in improving the conductivity of polystyrene (PS). Its PS nanocomposites exhibit a sharp transition from electrically insulating to conducting with a low percolation threshold of 0.24 vol% and a high electrical conductivity of 45 S m−1 is obtained with only 2.3 vol% of G-RGO. The superior electrical conductivity is attributed to the uniform dispersion of the G-RGO sheets in the PS matrix.
Co-reporter:Ruiqiong Liu, Songmiao Liang, Xiu-Zhi Tang, Dong Yan, Xiaofeng Li and Zhong-Zhen Yu
Journal of Materials Chemistry A 2012 - vol. 22(Issue 28) pp:NaN14167-14167
Publication Date(Web):2012/05/21
DOI:10.1039/C2JM32541A
Polyacrylamide (PAM)/graphene oxide (GO) nanocomposite hydrogels (PGH) with GO nanosheets as cross-linkers were synthesized via in situ free radical polymerization of acrylamide in an aqueous suspension of GO. The tensile properties of the hydrogels were investigated in terms of type and content of cross-linkers. Compared to conventional PAM hydrogels (PBH) cross-linked chemically with N,N′-methylenebisacrylamide, PGH exhibits high tensile strength, high toughness and especially a large elongation at break. The tensile strength of PGH is about 4.5 times higher than that of PBH, and the elongation at break is over 3000%, nearly one order higher than that of PBH even when the content of GO is only 0.0079 wt%. By analyzing the cross-linked structure of PGH and the theoretical calculation on the number of cross-linked polymer chains per unit volume of gels, a structure model was thus proposed.
Co-reporter:Hao-Bin Zhang, Ji-Wen Wang, Qing Yan, Wen-Ge Zheng, Cao Chen and Zhong-Zhen Yu
Journal of Materials Chemistry A 2011 - vol. 21(Issue 14) pp:NaN5397-5397
Publication Date(Web):2011/02/28
DOI:10.1039/C1JM10099H
We report a vacuum-assisted method for thermal exfoliation and in situreduction of graphite oxide in large quantity at a temperature as low as 135 °C. The resulting graphene sheets contain only few-layered sheets with an average thickness of 0.9 nm, and their specific surface area (758 m2 g−1) is comparable to that of conventional graphene generated at 1050 °C at atmospheric pressure (700 m2 g−1). The in situ thermal reduction during the exfoliation process was confirmed by the increased C/O atomic ratio compared to that of graphite oxide. The restoration of the graphitic sp2 network makes it highly efficient in improving the electrical conductivity of polymers at a low graphene loading.
