C/SiC复合材料表面SiC/Zr-Si-C/SiC复合涂层的制备及性能研究

为提高C/SiC复合材料的抗氧化性能,设计了致密的CVD-SiC涂层和多孔的熔盐法Zr-Si-C涂层相间的涂层体系.通过实验测试,建立了该涂层的生长模型,并考核了材料在1773 K的抗氧化性能.氧化结果显示,材料在氧化2h后的失重率为仅0.67;,弯曲强度保留率为99.7;,不同组成相间的结构涂层呈现出优异的抗氧化性能.     

SiC/SiC复合材料的原位合成与表征

采用常压烧结原位反应合成的方法制备了SiC/SiC复合材料,碳和硅是以滤纸和酚醛树脂为C源,采取滤纸表面涂覆Si粉树脂悬浮液的方法引入.采用XRD,SEM以及EDAX分别分析了材料的组成和微观机构,并重点分析了复合材料中SiC纳米线的生成与生长机理.结果表明,在温度为1430℃时,制备的SiC纳米线表面光滑,尺寸均一,长径比大于103,其生长机制为VS机制,由此开发了一种一步法制备SiC/SiC复合材料的新方法.     

SiC/SiC复合材料高温力学性能研究

以聚碳硅烷为连续SiC陶瓷基体相的先驱体,三维四向SiC纤维预制体为增强相,采用聚合物先驱体浸渍裂解工艺制备了SiC纤维增强SiC陶瓷基(SiC/SiC)复合材料,分析表征了复合材料的组成、结构和力学性能.结果表明,SiC/SiC复合材料室温弯曲强度和断裂韧性分别为400 MPa和16.5 MPa·m1/2,优异的室温力学性能可以保持到1350℃.随着温度增加,弯曲强度基本不变,1350℃时因界面层受到破坏而断裂韧性稍有下降.     

SiCf/SiC复合材料表面梯度抗氧化SiC涂层研究

SiC纤维增强SiC陶瓷基复合材料(简称SiCf/SiC复合材料)具有低密度、高温稳定性、抗氧化性、高耐腐蚀性等特点,在航天及航空发动机热结构部件及核聚变反应堆炉第一壁结构等方面有巨大的潜在用途.目前受工艺条件制约,SiCf/SiC复合材料中用来增强的SiC纤维纯度不高,C/Si原子比大于1.3,而采用传统先驱体浸渍裂解工艺(简称PIP)制备的基体材料除了纯度不高外,还含有孔隙和缺陷,不能满足高温氧化环境中服役要求.本文通过化学气相沉积工艺(CVD)在SiCf/SiC复合材料表面制备出一种高纯、低缺陷、耐高温、低氧扩散系数且与基体材料具有良好匹配性的SiC抗氧化梯度涂层,通过SEM分析基体与膜层的结合情况及涂层的微观形貌,通过XRD考察涂层的梯度组份及氧化前后涂层成份变化,进而探讨梯度涂层抗氧化机理.     

碳化硅单晶生长用高纯碳化硅粉体的研究进展

碳化硅(SiC)以其宽带隙、高临界击穿场强、高热导率、高载流子饱和迁移率等优点,被认为是目前较具发展前景的半导体材料之一.近年来,物理气相传输(PVT)法在制备大尺寸、高质量SiC单晶衬底方面取得了重大突破,进一步推动了SiC在高压、高频、高温电子器件领域的应用.SiC粉体是PVT法生长SiC单晶的原料,其纯度会直接影...     

SiC微粉添加量对SiC耐磨材料结构和性能的影响

以紧密堆积的三级配SiC颗粒(粒径为325 μm、212 μm、80 μm,质量比为17∶7∶1)为基础配方,将Owt;、1wt;、2wt;、3wt;和4wt;且粒径为5μm的SiC微粉添加到SiC耐磨材料中,经1600℃保温3h烧制,研究了SiC微粉添加量对SiC耐磨材料结构和性能的影响.结果表明:SiC微粉可促进SiC耐磨材料的烧结致密化,并改善其力学性能,当其添加量为3wt;时,试样的综合性能较优,其体积密度和显气孔率分别为2.63 g/cm3和7.62;,硬度、抗折强度和磨损量分别为2458 HV、183 Mpa和0.26 g/min.SiC耐磨材料烧结性能和力学性能的提高可归因子SiC微粉充填在SiC颗粒间,缩短了扩散传质路径,且较小粒径的SiC微粉具有较大的表面能,烧结时易于晶粒重排,保证了烧结网络的连续性,增大了颗粒间的结合程度.     

SiC单晶片的取向研磨

优质晶体生长常常需要籽晶或衬底偏离常规结晶取向.为便于按任意偏向角度研磨晶片,本实验室设计并应用了晶片取向研磨夹具及相应的研磨工艺.本文介绍了该夹具和工艺的工作原理、技术要点以及对技术指标的鉴定情况.测试结果表明,研磨取向误差范围可控制在5;之内,研磨片厚度偏差小于5 μm、粗糙度Ra=0.12 μm.     

成型压力对SiCnf增韧SiC陶瓷基复合材料微观结构和性能的影响

研究采用不同成型压力制备不同体积分数的SiC纳米纤维预制体,并通过前驱体浸渍裂解和反应熔渗联用工艺制备了SiC纳米纤维增韧SiC陶瓷基复合材料.研究了成型压力对SiC陶瓷基复合材料结构和性能的影响.结果表明,通过模压成型可实现高体积分数的SiC纳米纤维预制体的制备.当成型压力为40 MPa时,预制体SiC纳米纤维体积分...     

Size dependent photoluminescence of SiC nanocrystals

The paper presents the results of porous SiC study using photoluminescence and scanning electronic microscopy. It is shown that the intensity of defect-related PL bands (2.08, 2.27, 2.44 and 2.63 eV) increases monotonically with the rise of PSiC thickness from 2.1 up to 12.0 μm. These luminescence centers are assigned to surface defects which appear at the PSiC etching process. Photoluminescence intensity stimulation for surface defects is attributed to rise of defect concentrations with increasing of porous layer thickness and to realization of the hot carrier ballistic mechanism at surface defect excitation. Intensity enhancement for exciton-related PL bands (2.79, 2.98 and 3.26 eV ) is attributed to increasing the exciton recombination rate as result of exciton weak confinement in big size SiC NCs of different polytypes (6H–PSiC with inclusions of 15R- and 4H–PSiC).     

Comparative study of electroluminescence from annealed amorphous SiC single layer and amorphous Si/SiC multilayers

Si quantum dots (Si QDs) films were prepared by annealing amorphous SiC single layer and amorphous Si/SiC multilayers fabricated in plasma enhanced chemical vapor deposition system. The microstructures were characterized by Raman spectroscopy as well as Fourier transforms infrared spectroscopy for both samples. It was found that Si QDs with average size of 2.7 nm were formed after annealing and the electroluminescence (EL) band centered at 650 nm can be observed at room temperature. The EL intensity from the Si/SiC multilayers was obviously improved by one order of magnitude and the corresponding EL band width was reduced compared with that from SiC single layer film. The improved electroluminescence behavior can be attributed to the formation of the denser Si QDs, good size distribution and the strong confinement effect of carriers in multilayerd structures.