Xue Jun Zhang

Carbon Fiber Paper Modified with Carbon Nanotube for Proton Exchange Membrane Fuel Cell

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.

Activated Carbon Fiber for Super-Capacitor Electrode

Activated carbon fibers(ACFs) were prepared from general pitch-based carbon fiber by steam activation and catalytic activation method, respectively. The surface area and pore structure of the resultant ACFs were analyzed by N2 adsorption, and electrochemical performances as electrodes of super capacitors were characterized by galvanostatic, cyclic voltammograms and AC impedance spectrum analysis. The results show that ACFs prepared by both methods have similar BET surface area, while their pore size and distribution are different. Compared with steam activation, catalytic activation results in ACFs with high mesoporosity of 40%. The electrode performances show that the specific capacitances of ACFs prepared by catalytic activation method could be 213 F/g, two times of that of ACFs prepared by steam activation method, and more mesopores are the reason for the good capacitance performance.

Polyacrylonitrile-Based Activated Carbon Fiber/SnO2 Composites via Different Synthetic Methods

Polyacrylonitrile-based activated carbon fiber (PAN-ACF)/SnO2 composites were synthesized by sol-gel and in-situ chemical synthesis method, respectively, and characterized by XRD, TGA, and SEM. The electrochemical properties of the resultant composites as negative electrodes in lithium-ion battery were also studied to investage the influence of different synthetic methods on the structure and electrochemical properties of the composites. The results show that the SnO2 in the composites prepared by both methods has a tetragonal rutile structure but the structure and electrochemical properties are different. With the similar composition, the composites prepared by in-situ method have uniform distribution of SnO2 particles, and exhibit better cyclic performance than those made by sol-gel method. The capacity of PAN-ACF/SnO2 composites with SnO2 content of 42.9% prepared by in-situ method remains 401.2 mAh g-1 after 50 charge/discharge cycles at a current density of 50 mAh g-1.

Epoxy Modified Polyurethanes Coated High Modulus Carbon Fiber: Synthesis and Properties Studies

With toluene 2, 4-diisocyanate (TDI), polyethylene glycol (PEG) and 2,3-Epoxy-1-prop -anol (glycidol) used as the raw materials, two epoxy terminated polyurethanes (EPU) was synthesized by prepolymerization and closed end. Moreover, EPU with high toughhess is chosen as a coating agent for carbon fiber with three ethylene tetramine (TETA) as curing agen. The influence of the content of crosslinking agent in the coating layer on properties of composites and the mechanism of interface toughness are investigated. The chemical structure and thermal property of the EPU were studied with FTIR, 1HNMR and TGA, respectively. It proves that the thermal stability of EPU is more stable than epoxy coating. The interlaminar shear strength (ILSS) of the sized high modulus carbon fiber/epoxy composites is improved to 71MPa, which increased by 19.4% compared with the composites reinforced by unsized high modulus carbon fiber, and DMTA show that using EPU as a new kind of polymer coating for carbon fiber is a feasible method to improve the interfacial performance of high modulus carbon fiber/epoxy composites.

Study of the Surface Morphology and the Microstructure of PAN-Based Carbon Fibers

The microstructure of two kinds of self-made PAN-based high-modulus carbon fibers (HMCF-1, HMCF-2) was studied by scanning electron microscopy (SEM), Raman spectroscopy, X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM), and was compared with that of T800 and M55J. The correlation of XRD and HRTEM in terms of graphite crystallite sizes and interlayer spacing of graphite layer was also investigated. The results show that the diameters of T800, HMCF-1 and HMCF-2 are almost the same (~5.20μm) and all of them are lager than that of M55J (~4.86μm). The crystal sizes and the degree of graphitization are in the order of HMCF-2>HMCF-1>M55J>T800, while the regularity of the lattice fringes of HMCF-2 is better than those of others.

Synthesis of Latent Curing Agent for Epoxy Resin

A new kind of latent curing agent (LCA) for epoxy resin was synthesized by the reaction of Ethylenediamine with Butylacrylate in equal molar ratios, and the chemical structure and thermal property of the LCA were studied with FTIR and TGA, respectively. Moreover, LCA was also used to modify the epoxy sizing agent for high modulus carbon fiber. The results show that the wettability of sized carbon fiber tends to increase due to the increase of the polymer film on the surface of the carbon fiber, and interlaminar shear strength (ILSS) of the sized high modulus carbon fiber/epoxy composites is improved to 78MPa, which is increased by 8.6% compared with the composites reinforced by high modulus carbon fiber with unmodified sizing agent, indicating that using LCA modified epoxy resin as polymer coating for carbon fiber is a feasible method to improve the interfacial performance of high modulus carbon fiber/epoxy composites.

Effect of Zinc Ion on the Electrochemical and Thermal Performance of Polyaniline/Activated Carbon Composites Prepared by In Situ Emulsion Polymerization

Using dodecyl benzenesulfonic acid (DBSA) as surfactant, composites of polyaniline (PANI)/activated carbon (AC) with core-shell structures were prepared by in situ emulsion polymerization in the presence of different concentrations of zinc ion. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis and Fourier-transform IR (FT-IR) spectroscopy were used to analyze morphologies and structures of the composites. Thermal stability of the composites was investigated by thermogravimetric analysis (TGA).The electrochemical properties of PANI/AC composites were studied by galvanostatic charge/discharge tests. The composites exhibited different electrochemical and thermal behavior, which was found to be a function of the concentration of zinc ion.

Carbon Cloth Diffusion Layer for Fuel Cell Electrode

This paper has developed one way to produce flexible carbon cloth from artificial cotton cloth carbonized at 1000°C with using (NH4)2HPO4 as impregnation agent and phenolic resin as modification agent. The effects of (NH4)2HPO4 and phenolic resin on bulk resistivity, tensile strength, density, thickness and microstructure of the resultant carbon cloth were investigated. The results show that (NH4)2HPO4 impregnation is helpful to increase the carbon yield of artificial cotton cloth and decrease the bulk resistivity. The fibers in the carbon cloth are bond by carbonized phenolic resin, leading to higher tensile strength and lower bulk resistivity. When mass content of (NH4)2HPO4 was 5% and phenolic resin 54%, flexible and porous carbon cloth was prepared with thickness of 0.27mm, density of 0.34g/cm3, bulk resistivity of 0.06Ω·cm and tensile strength of 2.33MPa, which is promising materials for diffusion layer in fuel cell.

Preparation and Characterization of Mesoporous Activated Carbon Fiber

General purpose pitch-based carbon fiber (PCF) was pretreated with steam to develop pores on the surface of fiber. After immersed in cobalt salt solution, PCF was used as raw materials to prepare activated carbon fiber (ACF) through steam activation process. The effect of pretreatment of carbon fiber on specific surface area, mesopore volume and pore size distribution was investigated by N2 adsorption, and morphology of the resultant ACF was observed with scanning electron microscope(SEM). The results show that pretreatment of PCF enlarges specific surface area and mesopore ratio of ACF remarkably. The best ACF obtained in experiment is the one with specific surface area of 2670 m2/g and mesoporosity of 61.8%. Cobalt has evident catalysis in preparing ACF from activation of PCF, while specific surface area and pore size of ACF get smaller with cobalt salt immersion when pretreatment is too strong.

Supercapacitor Electrode Materials Based on Activated Carbon /Polyaniline Doped with Nickel Salt

Two types of supercapacitor electrode materials have been synthesized: AC/PANI, activated carbon composites polyaniline by in-situ polymerization of aniline on the surface of activated carbon, and Ni-AC/PANI, the AC/PANI composite dopes with nickel. The microstructure of composites has been examined by scanning electron microscope (SEM). Fourier transform infrared spectroscopy (FI-IR) has been used to determine the molecular structure and chemical bond of the composites. The nickel content has been measured by atomic absorption spectrometry (AAS). The electrochemical performance of the composite has been characterized by cyclic voltammery and galvanostatic charge-discharge in 6mol•L-1 KOH solution using Hg/HgO as reference electrode. Due to the doping of nickel salt, Ni-AC/PANI shows desired microstructure, good high-current charge-discharge performance and good electrochemical behavior with an capacitance of 535F•g-1, 38.2% higher than that of AC/PANI.