CVI处理短碳纤维在CFRC中分散性的评价(英文)

碳纤维增强水泥基复合材料（CFRC）是一种新发展起来的、很有潜力的功能材料。丙烯作前驱体，对短碳纤维在高温下（900-1300℃）进行100个小时左右的化学气相浸渍（CVI）表面处理。丙烯在高温下分解，生成热解碳，沉积在碳纤维表面。借助超声波预分散技术及新型分散剂羟乙基纤维素（hydroxyethyl cellulose，HEC）和超细颗粒硅灰的分散作用，实现了CVI处理碳纤维在水泥基体中的均匀分散。HEC水溶液的质量分数控制在1．56～1．77％之间为宜。分别运用扫描电镜法（SEM）、新拌料浆法（FM）、硬化试件电阻率测试法（ERM）及模拟试验法（SE）四种方法评价了CVI处理后短碳纤维的分散性。每种方法均有自身的优缺点和适应环境，四种方法中，模拟试验法（SE）是评价制备CFRC复合材料前期、碳纤维第一步分散的最方便的方法，此法不仅可节约时间和大量的原材料。而且可预测制备CFRC过程中应选择何种分散剂及碳纤维第二步分散的情况。

微波加热及其在陶瓷材料中的应用

微波加热制造陶瓷材料是近几年才开始应用于陶瓷材料研究与制造的最新技术。本文介绍了有关微波加热制造陶瓷材料的研究现状及重要成果，提出了这一技术进一步研究和推广应用亟待解决的问题。

纤维束丝数对平纹编织C/SiC复合材料力学性能的影响

通过对2种丝束平纹编织碳纤维布增强SiC(C/SiC)复合材料的力学性能实验,研究了纤维束丝数(1 k和3 k)对复合材料性能的影响。实验结果表明:1 k C/SiC复合材料的拉伸模量、拉伸强度、压缩模量、压缩强度、面内剪切强度和弯曲强度分别为90.8 GPa,281.8 MPa,135.8 GPa,452.2 MPa,464.3 MPa和126.8 MPa,分别比3 k C/SiC高39%,15.8%,25%,132%,29.3%和30.2%。纤维束粗细不同是导致纤维束弯曲度和复合材料孔隙率差异的主要原因,对压缩强度的影响最大,对拉伸强度的影响最小。

Effects of dip-coated BN interphase on mechanical properties of SiC_f/SiC composites prepared by CVI process

BN interphase was successfully synthesized on SiC fiber fabrics by dip-coating process using boric acid and urea as precursors under N2 atmosphere. The morphology of BN interphase was observed by SEM, and the structure was characterized by XRD and FT-IR spectra. The SiCf/SiC composites with dip-coated BN interphase were fabricated by chemical vapor infiltration （CVI） process, and the effects ofBN interphase on the mechanical properties of composites were investigated. The results show that the SiC fibers are fully covered by BN interphase with smooth surface and turbostratic structure （t-BN）, and the thickness is about 0.4 μm. The flexural strengths of SiCf/SiC composites with and without BN interphase are about 180 and 95 MPa, respectively. Compared with the as-received SiCf/SiC composites, the composites with BN interphase exhibit an obvious toughened fracture behavior. From the microstructural analysis, it can be confirmed that the BN interphase plays a key part in protecting the fibers from chemical attack during matrix infiltration and weakening interfacial bonding, which can improve the mechanical properties of SiCf/SiC composites remarkably.