Papers by Author: Zeng Min Shen

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Authors: Xue Jun Zhang, Hao Pei, Zeng Min Shen
Abstract: Carbon fiber paper was modified by adding carbon nanotubes to make it reach the demand of gas diffusion layer (GDL) by the process of impregnation with phenolic resin solution dispersed with carbon nanotubes, molding, and carbonization. The properties of modified carbon fiber paper, thickness, density, porosity, gas permeability, specific resistance and tensile strength, were characterized. The results indicate that surface treatment is helpful to disperse carbon nanotubes in phenolic resin. Phenolic resin is used to bond the carbon fibers, and carbon nanotube could reduce the specific resistance of the carbon fiber paper. When carbon nanotube content is 5 %, modified carbon fiber paper is prepared with thickness of 0.30 mm, density of 0.43 g/cm3, porosity of 77 %, gas permeability of 2400 mL•mm/(cm2•h•mmAq), specific resistance of 0.020 Ω•cm and tensile strength of 15 MPa, which basically qualifies for the application requirement.
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Authors: Xue Jun Zhang, Hao Pei, Zeng Min Shen
Abstract: Gas diffusion layer is a very important component in fuel cell, and carbon fiber paper is widely used as substrate of gas diffusion layer. This paper has developed one way to produce carbon fiber paper from carbon fiber felt with or without pretreatment. The properties and microstructure of carbon fiber paper were also stdied. The results show that the pretreatment of carbon fiber felt is helpful to prepare carbon fiber paper with good properties. The content of carbon derived from resin during pretreatment has effects on density, thickness, porosity, gas permeability, porosity and tensile streagth of carbon fiber paper. Carbon fiber paper made from carbon fiber felt with pretreatment has better interface adhension than that of carbon fiber paper made from carbon fiber felt without pretreatment. Carbon fiber paper was produced with thickness of 0.28mm, density of 0.43g/cm3, porosity of 77%, gas permeability of 2500 mL•mm/(cm2•hr•mmAq), specific resistance of 0.017Ω•cm and tensile strength of 18MPa, which is a promising materials for fuel cell electrode.
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Authors: Hong Mei Chai, Dong Lin Zhao, Zeng Min Shen
Abstract: The carbon nanotube/PMMA/PVAc composite film was prepared by solution casting. The carbon nanotube (CNT) and graphitized carbon nanotube (GCNT) were employed as conductive fillers in the composite films. The conductivity of the GCNT/PMMA/PVAc film is better than that of CNT/PMMA/PVAc film. The electrical percolation thresholds were at 5wt% and 2wt% respectively in the CNT/PMMA/PVAc film and GCNT/PMMA/PVAc film. The volume electric resistivities of CNT/PMMA/PVAc and GCNT/PMMA/PVAc composite film are at 0.044⋅m and 0.007⋅m respectively at 15wt% carbon nanotube. The significant difference of resistivity for the both types of composite film was due to different structure and crystallinity of CNT and GCNT.
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Authors: Dong Lin Zhao, Hong Mei Chai, Yun Fang Liu, Zeng Min Shen
Abstract: Thin films of poly(methyl methacrylate) (PMMA),poly(vinyl acetate) (PVAc) and carbon nanotube composites were produced by different coating methods. The best way to produce the carbon nanotube / PMMA / PVAc composite film with conductive network is dispersing carbon nanotubes in PMMA and PVAc by ultrasonic and by solution casting. Electrical resistance responses of carbon nanotube / PMMA / PVAc composite sensors against various organic vapors at low concentrations are investigated. The experimental results indicate that the composites have high selectivity to various organic vapors at the same concentration. In addition, the electric resistance response of the composites against organic vapors takes place in step with their vapor adsorption procedure. Compatible blends of poly(methyl methacrylate) and poly(vinyl acetate) would be a good candidate to produce a series of electrically conducting carbon nanotubes composite film whose resistance is sensitive to the nature and concentration of an analyte in the vapor phase. The results indicate that the carbon nanotube / PMMA / PAVc composite film can be used as a novel organic vapor sensor to detect, quantify and discriminate various organic vapors.
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Authors: Dong Lin Zhao, Xia Li, Wei Dong Chi, Zeng Min Shen
Abstract: The filling of multi-walled carbon nanotubes (MWNTs) with metallic silver nanowires via wet chemistry method was investigated. The carbon nanotubes were filled with long continuous silver nanowires. The carbon nanotubes were almost opened and cut after being treated with concentrated nitric acid. Silver nitrate solution filled carbon nanotubes by capillarity. Carbon nanotubes were filled with silver nanowires after calcinations by hydrogen. The diameters of silver nanowires were in the range of 20-40nm, and lengths of 100nm-10μm. We studied the micromorphology of the silver nanowires filled in carbon nanotubes by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Based on the experimental results, a formation mechanism of the Ag nanowire-filled carbon nanotubes was proposed. And the microwave permittivity of the carbon nanotubes filled with metallic silver nanowires was measured in the frequency range from 2 GHz to 18 GHz. The loss tangent of the carbon nanotubes filled with metallic silver nanowires is high. So the carbon nanotubes filled with metallic silver nanowires would be a good candidate for microwave absorbent.
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Authors: Xia Li, Dong Lin Zhao, Zeng Min Shen
Abstract: The filling of multi-walled carbon nanotubes with metallic silver nanowires via wet chemistry method was investigated. The carbon nanotubes were filled with long continuous silver nanowires. The carbon nanotubes were almost opened and cut after being treated with concentrated nitric acid. Silver nitrate solution filled carbon nanotubes by capillarity. Carbon nanotubes were filled with silver nanowires after calcinations by hydrogen. The diameters of silver nanowires were in the range of 20-40 nm, and lengths of 100 nm - 10 μm. We studied the micromorphology of the silver nanowires filled in carbon nanotubes by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Based on the experimental results, a formation mechanism of the Ag nanowire-filled carbon nanotubes was proposed.
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Authors: Dong Lin Zhao, Ren Hai Qiao, Cheng Zhong Wang, Zeng Min Shen
Abstract: The carbon nanotubes (CNTs) were prepared by catalytic decompose of benzene using floating transition method at 1100-1200°C. Benzene was used as carbon source and ferrocene as catalyst with thiophene. The carbon nanotubes are straight with diameter 20-50 nm, internal diameter 10-30 nm and length 50-1000 μm. The carbon nanotube and continuous carbon fiber (T300) reinforced unidirectional epoxy resin matrix composites was fabricated. The volune fraction of continuous carbon fiber (first filler) in the composites without second filler (carbon nanotube) was 60%. The mechanical properties of the composites were investigated under bending, shear, and impact loading. The flexural strength and modulus of the composites increased firstly and then decreased with the increasing of carbon nanotube contents in epoxy resin matrix. The flexural strength of the composites reached the maximum value of 1780 MPa when the weight percent of carbon nanotube in epoxy resin matrix was 3%.
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Authors: Cui Lin Han, Dong Lin Zhao, Lei Zhang, Zeng Min Shen
Abstract: Three-dimensional needled carbon/silicon carbide (C/SiC) composites with pyrolytic carbon interfacial layer were fabricated by precursor pyrolysis. The microstructure and mechanical property of the three-dimensional needled C/SiC composites were investigated. A thin pyrolysis carbon layer (0.2m) was firstly deposited on the surface of carbon fiber as the interfacial layer with C3H6 at 850 °C and 0.1 MPa by chemical vapor infiltration. Polycarbosilane and divinylbenzene were selected as a precursor to silicon carbide ceramics and a cross-linking reagent for PCS, respectively. The density of the composites was 1.94 g cm-3. The flexural strength of the three-dimensional needled C/SiC composites was 135 MPa. The three-dimensional needled C/SiC composites with pyrolytic carbon interfacial layer exhibit good mechanical properties and a typical failure behavior involving fibers pull-out and brittle fracture of sub-bundle.
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Authors: Fen Gao, Dong Lin Zhao, Zeng Min Shen
Abstract: Ni-Zn spinel ferrite and Cu-doped spinel ferrite were prepared by a conventional ceramic processing method. Microwave absorption, complex permittivity and permeability of the (Ni0.5Zn0.5)Fe2O4 and (Ni0.4Cu0.2Zn0.4)Fe2O4 spinel ferrites within the frequency range of 0.5-18 GHz were investigated. The reflection loss calculation results show that the Ni-Zn spinel ferrite and Cu-doped Ni-Zn spinel ferrite are good electromagnetic wave absorbers in the microwave range. The single layer (Ni0.4Cu0.2Zn0.4)Fe2O4 spinel ferrite absorber with a thickness of 9.2 mm achieved a reflection loss below -10 dB (90% absorption) at 0.5-2.3 GHz, and the minimum value is -35.63 dB at 1.1 GHz. When the first layer and second layer are (Ni0.5Zn0.5)Fe2O4 and (Ni0.4Cu0.2Zn0.4)Fe2O4 spinel ferrites respectively, the laminated absorbers with double spinel ferrite layers with a thickness of 3 mm achieved a reflection loss below -10 dB at 9.9-12.3 GHz, and the minimum value is -35.3 dB at 11.7 GHz.
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