The thermal radiation properties of pyrolytic carbon(PyC)protective coatings for monocrystalline silicon furnace prepared by different processes were tested.The changes of normal emissivity of carbon materials caused ...The thermal radiation properties of pyrolytic carbon(PyC)protective coatings for monocrystalline silicon furnace prepared by different processes were tested.The changes of normal emissivity of carbon materials caused by PyC protective coatings were discussed,and the influence of phase structure and surface appearance on the thermal radiation properties was investigated.The results show that the thermal radiation properties of PyC protective coatings with the wave band of 5-25μm are better than C/C substrate,further,normal spectral emissivity of CVD PyC coating remains basically at 0.85-0.90,and the normal total emissivity can reach0.89,which shows high thermal radiation performance.For resin PyC coating and CVD PyC coating,the degree of graphitization are 44.53%and 16.28%respectively,and the R value of Raman spectrum are 0.964and 1.384 respectively.Relatively disorder graphite structure of the latter causes various vibration modes,and the spectral emissivity is better,so the thermal radiation property of CVD PyC coating is excellent.A lot of spherical particles exists on the surface of the CVD PyC coating,and the more interface and spacing of particles reduce the number of particles per unit volume.Therefore,the scattering of thermal radiation is strongly strengthened,and the spectral emissivity is higher.展开更多
Aiming to obtain microwave absorbing materials with excellent mechanical and microwave absorption properties, carbon fiber reinforced Si3N4 ceramics(Cf-Si3N4) with pyrolytic carbon(PyC)/SiC interphases were fabricated...Aiming to obtain microwave absorbing materials with excellent mechanical and microwave absorption properties, carbon fiber reinforced Si3N4 ceramics(Cf-Si3N4) with pyrolytic carbon(PyC)/SiC interphases were fabricated by gel casting. The influences of carbon fibers content on mechanical and microwave absorption properties of as-prepared Si3N4 based ceramics were investigated. Results show that chemical compatibility between carbon fibers and Si3N4 matrix in high temperature environment can be significantly improved after introduction of Py C/SiC interphases. As carbon fibers content increases from 0 to 4 wt%, flexural strength of Si3N4 based ceramics decreases slightly while fracture toughness obviously increases. Moreover, both the real and imaginary parts of complex permittivity increase with the rising of carbon fibers content within the frequency range of 8.2–12.4 GHz. Investigation of microwave absorption shows that the microwave attenuation ability of Cf-Si3N4 ceramics with Py C/SiC interphases is remarkably enhanced compared with pure Si3N4 ceramics. Effective absorption bandwidth(<-10 d B) of10.17–12.4 GHz and the minimum reflection less of-19.6 d B are obtained for Si3N4 ceramics with 4 wt%carbon fibers in 2.0 mm thickness. Cf-Si3N4 ceramics with Py C/SiC interphases are promising candidates for microwave absorbing materials with favorable mechanical property.展开更多
The effect of pyrolytic carbon(PyC) thickness on the tensile property of mini T800 carbon fiber reinforced SiC matrix composites(C/SiC) was studied. PyC interphase was prepared by chemical vapor infiltration(CVI) proc...The effect of pyrolytic carbon(PyC) thickness on the tensile property of mini T800 carbon fiber reinforced SiC matrix composites(C/SiC) was studied. PyC interphase was prepared by chemical vapor infiltration(CVI) process using C3H6–Ar as gas source, the PyC thickness was adjusted from 0 to 400 nm, and then the SiC matrix was prepared by CVI process using methyltrichlorosilane(MTS)–H2–Ar as precursor and gas source. The results showed that the tensile strength of mini T800-C/SiC increased first and then decreased with the increase of the PyC thickness. When the thickness of PyC was 100 nm, the average strength reached the maximum value of 393 ± 70 MPa. The Weibull modulus increased from 2.0 to 8.06 with the increase of PyC thickness, and the larger the Weibull modulus, the smaller the dispersion, which indicated that the regulation of PyC thickness was conducive to improve tensile properties.展开更多
High-density polyethylene/carbon black foaming conductive composites were prepared from acetylene black（ACEY） and super conductive carbon black（HG-1P） as conductive filler, low-density polyethylene（LDPE） as the ...High-density polyethylene/carbon black foaming conductive composites were prepared from acetylene black（ACEY） and super conductive carbon black（HG-1P） as conductive filler, low-density polyethylene（LDPE） as the second component, ethylene-vinyl acetate（EVA） and ethylene propylene rubber（EPR） as the third component, azobisformamide（AC） as foamer, and dicumyl peroxide（DCP） as cross-linker. The structure and resistivity-temperature behavior of high-density polyethylene（HDPE）/CB foaming conductive composites were investigated. Influences of carbon black, LDPE, EVA, EPR, AC, and DCP on the foaming performance and resistivity-temperature behavior of HDPE/CB foaming conductive composites were also studied. The results reveal that HDPE/CB foaming conductive composite exhibits better switching characteristic; ACET-filled HDPE foaming conductive composite displays better positive temperature coefficient（PYC） effect; whereas super conductive carbon black（HG-1P）-filled HDPE foaming conductive composite shows better negative temperature coefficient（NTC） effect.展开更多
基金Sponsored by the National High Technology Research and Development Program of China(863 Program)(Grant No.2009AA035301)the ChinaPostdoctoral Science Foundation(Grant No.2012M511544)
文摘The thermal radiation properties of pyrolytic carbon(PyC)protective coatings for monocrystalline silicon furnace prepared by different processes were tested.The changes of normal emissivity of carbon materials caused by PyC protective coatings were discussed,and the influence of phase structure and surface appearance on the thermal radiation properties was investigated.The results show that the thermal radiation properties of PyC protective coatings with the wave band of 5-25μm are better than C/C substrate,further,normal spectral emissivity of CVD PyC coating remains basically at 0.85-0.90,and the normal total emissivity can reach0.89,which shows high thermal radiation performance.For resin PyC coating and CVD PyC coating,the degree of graphitization are 44.53%and 16.28%respectively,and the R value of Raman spectrum are 0.964and 1.384 respectively.Relatively disorder graphite structure of the latter causes various vibration modes,and the spectral emissivity is better,so the thermal radiation property of CVD PyC coating is excellent.A lot of spherical particles exists on the surface of the CVD PyC coating,and the more interface and spacing of particles reduce the number of particles per unit volume.Therefore,the scattering of thermal radiation is strongly strengthened,and the spectral emissivity is higher.
基金supported by the National Natural Science Foundation of China (Grant No. 51604107)the Natural Science Foundation of Hunan Province (Grant No. 2019JJ50115 and 2019JJ50768)
文摘Aiming to obtain microwave absorbing materials with excellent mechanical and microwave absorption properties, carbon fiber reinforced Si3N4 ceramics(Cf-Si3N4) with pyrolytic carbon(PyC)/SiC interphases were fabricated by gel casting. The influences of carbon fibers content on mechanical and microwave absorption properties of as-prepared Si3N4 based ceramics were investigated. Results show that chemical compatibility between carbon fibers and Si3N4 matrix in high temperature environment can be significantly improved after introduction of Py C/SiC interphases. As carbon fibers content increases from 0 to 4 wt%, flexural strength of Si3N4 based ceramics decreases slightly while fracture toughness obviously increases. Moreover, both the real and imaginary parts of complex permittivity increase with the rising of carbon fibers content within the frequency range of 8.2–12.4 GHz. Investigation of microwave absorption shows that the microwave attenuation ability of Cf-Si3N4 ceramics with Py C/SiC interphases is remarkably enhanced compared with pure Si3N4 ceramics. Effective absorption bandwidth(<-10 d B) of10.17–12.4 GHz and the minimum reflection less of-19.6 d B are obtained for Si3N4 ceramics with 4 wt%carbon fibers in 2.0 mm thickness. Cf-Si3N4 ceramics with Py C/SiC interphases are promising candidates for microwave absorbing materials with favorable mechanical property.
基金supported by the National Natural Science Foundation of China (Nos. 51702261, 51821091, and 51802263)the Natural Science Foundation of Shaanxi Province (Project No. 2019JQ-634)the Fundamental Research Funds for the Central Universities。
文摘The effect of pyrolytic carbon(PyC) thickness on the tensile property of mini T800 carbon fiber reinforced SiC matrix composites(C/SiC) was studied. PyC interphase was prepared by chemical vapor infiltration(CVI) process using C3H6–Ar as gas source, the PyC thickness was adjusted from 0 to 400 nm, and then the SiC matrix was prepared by CVI process using methyltrichlorosilane(MTS)–H2–Ar as precursor and gas source. The results showed that the tensile strength of mini T800-C/SiC increased first and then decreased with the increase of the PyC thickness. When the thickness of PyC was 100 nm, the average strength reached the maximum value of 393 ± 70 MPa. The Weibull modulus increased from 2.0 to 8.06 with the increase of PyC thickness, and the larger the Weibull modulus, the smaller the dispersion, which indicated that the regulation of PyC thickness was conducive to improve tensile properties.
文摘High-density polyethylene/carbon black foaming conductive composites were prepared from acetylene black（ACEY） and super conductive carbon black（HG-1P） as conductive filler, low-density polyethylene（LDPE） as the second component, ethylene-vinyl acetate（EVA） and ethylene propylene rubber（EPR） as the third component, azobisformamide（AC） as foamer, and dicumyl peroxide（DCP） as cross-linker. The structure and resistivity-temperature behavior of high-density polyethylene（HDPE）/CB foaming conductive composites were investigated. Influences of carbon black, LDPE, EVA, EPR, AC, and DCP on the foaming performance and resistivity-temperature behavior of HDPE/CB foaming conductive composites were also studied. The results reveal that HDPE/CB foaming conductive composite exhibits better switching characteristic; ACET-filled HDPE foaming conductive composite displays better positive temperature coefficient（PYC） effect; whereas super conductive carbon black（HG-1P）-filled HDPE foaming conductive composite shows better negative temperature coefficient（NTC） effect.
