共查询到19条相似文献,搜索用时 93 毫秒
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温度对CLVD致密化工艺中毡基C/C复合材料性能的影响 总被引:3,自引:0,他引:3
对不同温度下化学液气相渗透工艺(CLVD)制备的C/C复合材料物理性能和力学性能变化进行了研究,揭示了温度在此工艺中的关键作用以及对材料性能的影响,在850℃-1100℃,C/C复合材料的质量增加,表观密度及总孔隙率均随时间呈线性变化;其化学反应的活化能为117.4kJ/mol,说明沉积化学反应成为控制反应机制,三点弯曲测试表明,C/C复合材料弯曲强度在此区间内随温度升高先增大后减小,弯曲模量却一直减小,这主要是材料中缺陷多少和分布均匀性以及材料微观结构变化造成的。 相似文献
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炭/炭复合材料致密化工艺研究现状 总被引:1,自引:1,他引:0
综述了炭/炭复合材料制备过程中所采用致密化工艺的研究现状,详细分析了液相浸渍和化学气相渗积(CVI)的工艺原理。液相浸渍工艺需要进行多次反复浸渍,较为繁杂;等温CVI工艺简单、产品性能稳定,但制备周期长、效率较低。在此基础上发展了强制流动热梯度CVI、感应加热梯度快速致密化技术、等离子体增强CVI、直热式化学气相渗积法(HCVI)等工艺,本文同时对这些工艺的原理及优缺点进行了阐述。 相似文献
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以天然气为碳源前驱体、N2作为载气,采用等温、等压化学气相渗透(CVI)工艺,对初始密度为0.42g/cm3的预制体针刺毡进行致密得到C/C复合材料,本文研究了载气条件对C/C复合材料的致密化效率、微观结构及性能的影响。研究结果表明,沉积温度1050℃、沉积压力4KPa条件下,沉积120h后送N2(天然气与N2的比例为5∶1),300h致密化后C/C复合材料的密度可达到1.46g/cm3,表观和内层的密度差异仅为0.07g/cm3;复合材料表面可看到明显的预制体孔隙,未出现结壳情况;弯曲强度可达到107.8MPa,断口形貌以假塑性断裂为主,纤维与热解碳之间结合良好;在1000℃下垂直纤维方向的最大热膨胀系数仅为0.925×10-6/℃,说明复合材料具有优异的热力学性能。 相似文献
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热梯度CVI制备炭/炭复合材料及其研究进展 总被引:1,自引:0,他引:1
按预制件内部的温度分布不同,可以认为,均热法及热梯度法是化学气相沉积制备炭/炭复合材料的两种基本工艺。对于圆筒或圆盘形工件,热梯度CVI具有增密快,炭的有效利用率高,可实现工业规模化生产的优点,是一种很有前景的CVI工艺。本文介绍了热梯度CVI制备炭/炭复合材料的工艺原理、工艺特点及其最新研究进展。 相似文献
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《Journal of the European Ceramic Society》2020,40(3):642-650
Groups of carbon/carbon (C/C) and tantalum carbide (TaC)-coated C/C composite specimens were studied under exposure to atomic oxygen (AO). Low earth orbit ground-based simulator was employed. Degradation mechanisms were investigated by scanning electron microscopy, X-ray photoelectron spectroscopy, and energy dispersive spectrometry. The results indicated that compared to C/C composite, TaC-coated C/C composite exhibited improvements in resistance properties against AO flux, such as 16.7% better strength retention ratio and 57% less mass ablation than non-coated C/C after 40 h of AO exposure. Moreover, AO preferentially consumed tantalum (Ta) atoms than carbon atoms of TaCx till atomic ratio was in the same proportion. Production of swollen tantalum oxide and crack healing components were obtained under the oxidation effect of high-speed AO. Swelling textures due to exposure were developed following an apical dominance growth behavior. The damage mechanisms of AO on TaC-coated C/C were revealed as chemical reaction first followed by mechanical effect. 相似文献
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Remani Sreeja Palani Prabhakaran Shyin Cheriyan Suchithra Deepa Devapal Payyadakam Veetil Prabhakaran 《International Journal of Applied Ceramic Technology》2023,20(5):2796-2806
Silicon carbide (SiC) foam prepared by polymer infiltration and pyrolysis (PIP) process was further densified with β-SiC by chemical vapor infiltration (CVI) technique. Scanning electron microscopy and high-resolution transmission electron microscopy images confirmed the presence of highly entangled and branched in situ grown SiC wires of uniform diameter (∼500 nm) over the struts of open-cell SiC foam. A uniform rate increase in diameter from nanometer to micron range (∼11 μm) was observed with an increase in the CVI reaction period. X-ray diffraction results showed the formation of highly crystalline β-SiC structure along the <111> direction with stacking faults. The formation of SiC wires was explained by the vapor–liquid–solid mechanism and evenness of the surface and uniform growth rate of SiC confirmed the homogeneous concentration of gaseous species during CVI reaction. The compressive strength increased with relative density, with maximum values of 5.5 ± 1.26 MPa for ultimate SiC foam (ρ = 400 kg/m3) prepared by hybrid PIP/CVI technique. The thermo-oxidative stability of the resultant foam was evaluated up to 1650°C under air and shows excellent thermal stability compared to SiC foam prepared by PIP route. The densified SiC foam can find potential applications in the field of hot gas filters, catalyst supports, microwave absorption properties, and heat insulation for high-temperature applications. 相似文献
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In this research, in order to improve the mechanical strength and oxidation resistance of a catalyst support, we studied the
formation of SiC layer on the pore surfaces of activated carbons by permeating and depositing SiC from a reaction between
hydrogen and dichlorodimethylsilane (DDS). The porous structure should be kept during deposition. A fluidized bed reactor
and activated carbons of size of 20-40 mesh were used. By studying characteristics of deposits under various deposition conditions,
we confirmed that the best conditions of manufacturing catalyst support are a lower pressure and a lower concentration. In
this work, at the conditions of 5 torr of total pressure and 3% of DDS concentration, during the 10 hr processing time, deposition
occurred on the pore walls before plugging pores. The results from the mathematical modeling were compared with the experimental
results. 相似文献
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CVI法制备SiCp/SiC复合材料的微结构与性能研究 总被引:2,自引:0,他引:2
本文对用CVI法制备的SiCp/SiC复合材料的微结构与性能进行了研究.通过造粒使颗粒成为类似纤维束的均匀团聚体,通过预制成型使颗粒成为类似纤维预制体的坯体后进行化学气相渗透(CVI).由这种工艺制备的复合材料弯曲强度达到163MPa;成分包括α-SiC、6HSiC及石墨化的碳.它具有适当弱界面层增韧和非均匀复合效应等增韧途径. 相似文献
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采用阳离子交换树脂作为炭载体的前驱体,经过镍离子交换,再经热解后制备了一种纳米镍/炭(n—Ni/C)复合材料。以XRD、SEM、TEM、EDS为主要分析手段研究了热解条件对纳米镍在n—Ni/C复合材料中的形貌、大小和分布情况的影响。结果表明:通过热解条件可以控制n—Ni/C复合材料中纳米镍的粒径;TEM和SEM—EDS观察表明热解所得n—Ni/C复合材料中的纳米镍颗粒大小均匀、分散性好。差热分析(DTA)研究结果表明加入n-Ni/C可增加高氯酸铵(AP)的表观放热量,降低AP的高温分解峰,最大可达95℃。 相似文献