CVI处理短碳纤维在CFRC中分散性的评价

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.

Evaluation on Dispersion of CVI Treated Carbon Fibers in CFRC

Short carbon fibers were treated through Chemical Vapor Infiltration (CVI) process at high temperatures between 900 and 1300℃. Propylene was used as precursor and it was decomposed to produce pyrocarbon that was deposited on the surface of carbon fibers. A new dispersant hydroxyethyl cellulose (HEC) was employed to disperse CVI treated carbon fibers in the cement matrix. Its mass fraction lay in between 1.56 and 1.77% in aqueous solution. Four methods of the scanning electron microscopy, the fresh mixture, the electrical resistivity of hardened samples, and the simulation experiment were, respectively, applied to evaluate their dispersion degree. Each method has its own advantages and disadvantages and it therefore catered for different conditions. Of the four evaluation methods, the simulation experiment one was the most convenient way to determine the first-step dispersion state prior to the preparation of carbon-fiber-reinforced cement-based composites and it was helpful for predicting the second-step dispersion state of carbon fibers in the cement matrix because it economized a large quantity of raw materials and time.