This work tests the effect on microstructure, flexural strength, flexural moduli, plus the electrical and thermal conductivity of carbon/carbon composites with Mesocarbon Microbeads (MCMBs) content ranging 0 -30% by weight during carbonization. These composites were reinforced by oxidative PAN Base fiber felts, and matrix precursor was resol-type-phenolic resin. MCMBs with a weight fraction of 0 -30% were added to the matrix to elucidate the effect. Liquid-phase impregnation was applied to reinforce matrix carbon. Cured composites were stabilized at 230°C, then heat-treated at 400, 600, 800, 900 and 1000°C for carbonization. The measured flexural strength after heattreated at 1000°C was 51.20, 49.59, 43.55, and 38.76 MPa for MCMBs with 0, 10, 20, and 30% added to composites; mean flexural moduli were l.73, 1.24, 0.73, and 0.57 MPa, respectively. Adding MCMBs reduced both strength and modulus because of cracks and avoids caused by different shrinkage between resin and MCMBs; adding 30 wt % MCMBs raised thermal conductivity of C/C composites from 1.55 to 1.78 W/mK and reduced electric resistivity from 1.8 ϫ 10 Ϫ2 to 5.97 ϫ 10 Ϫ3 ⍀ cm.
Carbon/carbon (C/C) composites were prepared from oxidative PAN fiber felts, a resol-type phenolic resin, and mesophase pitch derived from coal tar. In this study, the effects on mesocarbon microbeads (MCMBs), flexural strength, flexural moduli, electric conductivity, and thermal conductivity of C/C composites with a mesophase content ranging from 0 to 30 wt % were examined during pyrolysis. The results show that the C/C composite with the addition of 10 -30 wt % mesophase had a higher density, greater stacking size, and higher preferred orientation than the C/C composites without any mesophase during heat treatment. These composites also exhibited an improvement in flexural strength from 19.7 to 30.3%. The flexural moduli of these composites with mesophase added increased by 15.1 to 31.3% compared to that with no mesophase added. These composites also showed improved electric conductivity, from 15.1 to 43.7%, and thermal conductivity, from 12 to 31.3%.
Bamboo is a typical natural composite material, and its special structure and excellent properties provide important information for the biomimetic design of composites. To strengthen the fiber content of bamboo distributed in a gradient, a bimimetic nano-Al 2 O 3 composite coating was designed and prepared on the surface of metal parts using a nanocomposite electrodeposition method. The optimal technology parameters were obtained, such as current density, PH value, nano-Al 2 O 3 content in electrolyte, and style of stirring etc after the experiments. The microstructure of the biomimetic nanocomposite gradient coating was very dense, and the contents of nano-Al 2 O 3 were distributed in the gradient. The microhardness of the composite coating changed from the surface to the inside in the gradient also. Moreover, the wetting angle between water and composite coating obviously increased and reached 97°at room temperature.
ABSTRACT:After vapor-grown carbon-fibers (VGCF) were added to resol-type phenolic resin, their influence on microstructure, thermal conductivity, flexural strength, and physical properties of the resin was characterized in this work. Resin with content 0 -10 wt % VGCF was heat-treated at 230 -2500°C. As a result, it was observed that adding VGCF into resin during pyrolysis not only reduced weight loss but also limited shrinkage of resin. Moreover, adding VGCF to resin promoted the degree of arranging carbon basal planes and chemical densification of the structure of final heat-treated resins. At 2500°C, the graphitized resin with 10 wt % VGCF enhanced flexural strength and thermal conductivity over 300%, while decreasing weight loss around 20% versus graphitized phenol-formaldehyde resin developed from the original resin.
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