Ni/Al_2O_3催化制备碳/碳复合材料研究

Greatly Reducing Cost in CVI Fabrication of C/C Composites

提出了催化化学气相渗透(CCVI)法制备碳/碳复合材料的新工艺,即在针刺碳布预制体中添加3.5%～4%Ni/Al2O3负载型金属催化剂,以丙烯作碳源气体,在750～900℃下,经过100h的沉积,碳/碳复合材料的密度达到1.68 g/cm3.该材料经高温处理后,氧化失重率低、氧化起始温度高.应用扫描电镜(SEM)、X射线衍射分析(XRD)和偏光显微镜(PLM)观察了基体碳的形貌,初步探讨了催化沉积碳和抗氧化机理.

There exist many fast CVI （chemical vapor infiltration） equipments for fabricating C/C （carbon/carbon） composites sample, one at a time. We aim to reduce the fabrication cost greatly while retaining the advantage of conventional CVI equipment to fabricate several C/C composites samples at the same time; furthermore we aim to make these samples much more oxidation resistant. In this study, a new densification process of C/C composites is investigated by what we call catalytic chemical vapor infiltration （CCVI）. Ni/Al2O3 catalysts with different weight percentages of nickel are added in the carbon fiber cloth substrate. Propylene, which is carried in flowing hydrogen, deposits on the substrate as source under catalysis of Ni/Al2O3 at 750-900℃. Being deposited for 100 h, the density of C/C composites can reach 1.68 g/cm^3, and its rate of depositing is at least three times faster than that of the case in which catalyst is not used; thus, the fabrication cost is greatly reduced. After high temperature heat treatment, the weight loss of C/C composites prepared by CCVI is small, and, more importantly, the sample＇s initial oxidation temperature is 155℃ higher than that of the case in which catalyst is not used. The surface morphology of pyrolytic carbon is characterized by scanning electronic microscopy （SEM） and polarized light microscopy （PLM） respectively. The mechanism of the catalytic deposition and increase of resistance against oxidation is studied preliminarily.