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Chemical vapor infiltration of carbon fiber felts with uniform initial bulk density of 0.47 g·cm-3 was investigated at the ethanol partial pressures of 5-20 kPa,as well as the temperatures of 1050,1100,1150 and 1200°C.Ethanol,diluted by nitrogen,was employed as the precursor of pyrolytic carbon.Polarized light microscopy(PLM),scanning electron microscopy and X-ray diffraction were adopted to study the texture of pyrolytic carbon deposited at various temperatures.A change from medium-to high-textured pyrolytic carbon was observed in the sample infiltrated at 1050°C.Whereas,homogeneous high-textured pyrolytic carbons were deposited at the temperatures of 1100,1150 and 1200°C.Extinction angles of 19°-21° were determined for different regions in the samples densified at the temperatures ranging from 1100 to 1200°C.Scanning electron microscopy of the fracture surface after bending test indicated that the prepared carbon/carbon composite samples exhibited a pseudo-plastic fracture behavior.In addition,fracture behavior of the carbon/carbon samples was obviously effected by their infiltration temperature.The fracture mode of C/C composites was transformed from shearing failure to tensile breakage with increasing infiltration temperature. Results of this study show that ethanol is a promising carbon source to synthesize carbon/carbon composites with homogeneously high-textured pyrolytic carbon over a wide range of temperatures(from 1100 to 1200°C).
Chemical vapor infiltration of carbon fiber felts with uniform initial bulk density of 0.47 g · cm -3 was investigated at the ethanol partial pressures of 5-20 kPa as well as the temperatures of 1050,1100,1150 and 1200 ° C. Ethanol, diluted by nitrogen, was employed as the precursor of pyrolytic carbon. Polarized light microscopy (PLM), scanning electron microscopy and X-ray diffraction were adopted to study the texture of pyrolytic carbon deposited at various temperatures. A change from medium-to high- textured pyrolytic carbon was observed in the sample infiltrated at 1050 ° C.Whereas, homogeneous high-textured pyrolytic carbons were deposited at the temperatures of 1100,1150 and 1200 ° C.Extinction angles of 19 ° -21 ° were determined for different regions in the samples densified at the temperatures ranging from 1100 to 1200 ° C. Scanning electron microscopy of the fracture surface after bending test indicated that the prepared carbon / carbon composite samples rendered a pseudo-plastic fracture beh avior.In addition, the fracture behavior of the carbon / carbon samples was obviously effected by their infiltration temperature. The fracture mode of C / C composites was transformed from shearing failure to tensile breakage with increasing infiltration temperature. Results of this study show that ethanol is a promising carbon source to synthesize carbon / carbon composites with homogeneously high-textured pyrolytic carbon over a wide range of temperatures (from 1100 to 1200 ° C).