邓海亮
,
李克智
,
李贺军
,
杨宗伦
,
曹伟锋
,
卢锦花
新型炭材料
采用薄膜沸腾CVI以双热源加热的方法在900~1200℃下热解二甲苯前驱体增密二维针刺炭毡预制体,30~35 h内制备出密度1.70 g/cm3~1.73 g/cm3的C/C复合材料。研究致密化过程中热解炭基体的沉积速率变化规律,应用排水法和偏光显微镜分别测试材料的密度及热解炭层的厚度。结果表明,当沉积温度由900~1000℃升高至1100~1200℃时,沉积前沿的厚度拓宽,热解炭的初始沉积速率增大,但高沉积温度下预制体边缘将优先完成致密化,导致材料的平均密度由1.72~1.73 g/cm3降低至1.70,致密化均匀性变差,材料轴向和径向方向的密度偏差高于0.04 g/cm3。上热源开多个轴向通孔可使沉积前沿的厚度减小,前驱体在预制体内的传输效率提高,进而改善较高沉积温度下材料的致密化效果。
关键词:
C/C复合材料
,
化学气相渗透
,
致密化特性
Wei XIONG
,
Xiaoying QIN
,
Li WANG
材料科学技术（英）
Densification behavior of nanocrystalline Mg2Si (n-Mg2Si) with grain size about 30–50 nm was investigated by hot-pressing at 400℃. The results indicated that the densification process of n-Mg2Si exhibited three linear segments: p<0.3 GPa, 0.3 GPa1.2 GPa determined by Heckel formula, among which the third fast increasing segment in high pressure range p>1.2 GPa has seldom been reported in conventional coarse-grained polycrystalline materials. Nevertheless, in the whole pressure range (0.125–1.500 GPa) investigated the densification behavior of n-Mg2Si can be well described by a Kawakita formula p/C=(1/a)p+1/(ab) with constant a=0.452 being in good agreement with the initial porosity of the com
关键词:
Nanocrystalline Mg2Si
,
null
,
null
