Papers by Author: Qi Zhong Huang

Abstract: Using the dry method-prepared polyacrylonitrile based carbon fibers as raw the material, carbon paper applied for proton exchange membrane fuel cells was prepared by the processes of molding, high temperature carbonization, chemical vapor deposition (CVD), and graphitization. The effects of resin carbon content and subsequent heat-treatment process parameters on the properties of carbon paper were studied. The results show that: the resin carbon content is an important factor to affect the density, thickness, through-plane resistivity and porosity of carbon paper. When the resin carbon content is 20%, the thickness of carbon paper is 0.20mm, the density is 0.41g/cm³, and the porosity is 74.5%, in line with requirements of the fuel cell. When the heating time is 4 hours, the porosity is 71.9%.

Abstract: Isotropic pyrocarbon was deposited on self-heating plate at 1100°C and atmospheric pressure via a novel deposition reactor. Two graphite papers were mounted horizontally in chemical vapor deposition furnace, which were used as self- heating plates with alternating current flowing through them. And the upper surface of the lower self-heating plate also was used as substrate of pyrocarbon deposition. The microstructure of the deposit was investigated by polarized light microscopy, scanning electron microscope, transmission electron microscopy and laser Raman spectra, respectively. The results showed that there were some irregular clusters of globular structure and onion-like structure in the deposits. The thickness and density of deposit were13-15 mm and 1.88 g/cm³ in 30h. A novel deposition model of electromagnetic effect on intermediate product has been developed in order to establish a better description of the deposition process.

Abstract: The effect of microstructure and its distribution of pyrolytic carbon in different deposition stage in carbon-carbon composites infiltrated by multi-factor physical fields chemical vapor infiltration (CVI) on the mechanical has been studied by polarized -light microscopy, Raman spectra, scanning electron microscope and three-point bending tests. The temperature and the change of the [A_S/V_R]-ratio with progressive infiltration are key parameters for the formation of microstructure and its distribution of pyrolytic carbon around the same fiber. SL pyrolytic carbon corresponds to brittle failure mode and smooth two-step fracture surface due to its low and uniform texture，although the abnormal graphitization occurs in the carbon fiber near the fiber/matrix interface. In contrast, RL matrix can function for achievement of nonbrittle fracture behavior with a zig-zag-like fracture surface and a relatively high value of flexural strength due to high and nonuniform texture.

Abstract: A novel rapid chemical vapor infiltration (CVI) processing defined by multi-physics fields CVI was used to fabricate carbon/carbon (C/C) composites. Liquid petrol gas is used as carbon source and the parameters were experimental tested and optimized. Because of the influence of multi-physics fields, a new surface morpha is grown under control parameters. It is called “Dot Structure”. The structure of pyrocarbon is analyzed and characterized by XRD, SEM with EDS, and Raman spectrum. At the end, a simple model of point discharge for growth of pyrocarbon is proposed. The deposited pyrocarbon based on multi-physics fields chemical vapor infiltration is expected to provide an improve performance in rapid C/C composites fabrication.

Abstract: The C/C composite was rapidly fabricated by Multi-factor coupling fields CVI in a home-made reactor with propylene as carbon source and carbon felt as porous preform. The effect of the temperature and pressure on microstructure and properties of the C/C composites was investigated. Microstructure and morphology of the C/C composites were characterized with optical microscopy, SEM, XRD and Raman spectroscopy. The results show the C/C composite has rough laminar pyrolytic carbon and higher density at conditions of 650°C and 12kPa in 12h. The observed regenerative cones were formed by amplified layers on defects. A new type of pyrocarbon was observed with graphitization degree 77.9% and crystallite size 30.5 nm and Optical and SEM morphologies reveal its peculiar structure. It is called “dot structure” pyrocarbon and its formation mechanism is simple proposed.