Yulei ZHANG
,
Hejun LI
,
Qiangang FU
,
Kezhi LI
,
Dangshe HOU
,
null
材料科学技术(英文)
In order to improve the anti-oxidation property of carbon/carbon (C/C) composites, a novel SiC-Si-ZrSiO4 multiphase oxidation protective coating was produced on the surface of C/SiC coated carbon/carbon composites by a pack cementation technique. The phase composition and microstructure of the as-prepared coatings were characterized by XRD (X-ray diffraction), SEM (scanning electron microscopy) and EDS (energy dispersive spectroscopy). Oxidation behavior of the multiphase coated C/C composites was also investigated. It showed that the as-prepared coating characterized by excellent oxidation resistance and thermal shock resistance could effectively protect C/C composites from oxidation at 1773 K for 57 h in air and endure the thermal cycle between 1773 K and room temperature for 12 times, whereas the corresponding weight loss is only 1.47%. The excellent oxidation protective ability of the SiC-Si-ZrSiO4 coating could be attributed to the C/SiC gradient inner layer and the multiphase microstructure of the coating.
关键词:
Carbon/carbon composites
,
null
,
null
Kezhi LI
,
Chuang WANG
,
Hejun LI
,
Gengsheng JIAO
,
Jian WEI
材料科学技术(英文)
The influence of dispersion of carbon fibers in carbon-fiber-reinforced cement-based composites (CFRC) on the mechanical properties of the composites was discussed. The microstructure of the fracture surface of the CFRC samples was observed with a scanning electron microscope (SEM). The electromagnetic interference (EMI) was evaluated indirectly by reflectivity in the Naval Research Laboratory (NRL) testing system. The reflectivity of the electromagnetic radiation by the composites was measured in the frequency range of 8.0–8.2 GHz for different carbon fiber contents of 0.2%, 0.4%, 0.6%, 0.8%, and 1.0% (in wt pct), respectively. The results showed that the reflectivity decreased with the growing fiber content till the percentage of 0.6%. The minimum reflectivity was -23 dB, far less than ¡10 dB, and the composites were strong wave absorbers. After this percentage, the curve increased abruptly as the fiber content proceeded. The electromagnetic waves were gradually reflected. When the fiber content reached 1.0% finally, the maximum reflectivity -7.5 dB appeared and there was stronger reflection. The shielding mechanism includes mainly reflection, absorption, and multiple reflections.
关键词:
Carbon fibers
,
fibers
,
Cement-based
,
EMI
,
Reflectiv