PREPARING C/ C COMPOSITES BY CVI WITHMULTI-FACTOR COUPLINGPHYSICAL FIELDS AND DISCUSSING THE DYNAMIC PROCESS
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摘要: 采用多元耦合物理场CVI 工艺, 用炭毡作为增强体, 在增强体中设计导电层, 产生温度场和电磁场梯度, 在自行设计的CVI 炉中增密C/ C 复合材料, 对温度、系统压力和气体流量等工艺进行了优化; 采用偏光显微镜研究了热解炭的显微结构; 用X射线衍射研究了材料的石墨化度; 探讨了本工艺中的有内热源和无内热源的二元传热机制, 多元耦合物理场的有机耦合对“消耗传质”的抑制作用, 以及电磁场对沉积的影响和3 种典型的生长模型。研究表明, 多元耦合物理场CVI 增密速度快, 初始密度为0.2 g/ cm3 , 尺寸为260 mm ×60 mm ×20 mm 的增强体, 在920 ℃、4 kPa 条件下沉积20 h , 试样可增密到1.71 g/ cm3 ; 可获得粗糙层结构(RL) 、光滑层结构(SL) 、带状结构(Banded st ructure) 等热解炭的结构, 在960 ℃、0.1 kPa 条件下可获得较高织构的粗糙层结构。
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关键词:
- 多元耦合物理场CVI /
- C/ C 复合材料 /
- 快速致密 /
- 传质传热 /
- 沉积模型
Abstract: Installing special elect ric layer in preforms of carbon felt , C/ C composites were fabricated by chemicalvapor infilt ration (CVI) with multi-factor coupling physical fields , and the infilt ration conditions were optimized.The textures of pyrolytic carbons were observed using polarized light microscopy ( PLM) , and the graphitization degree of these C/ C composites was analyzed by XRD ; The effect of elect romagnetic field on the CVI and dynamicprocess of dual convective heat of outer thermogenesis and inner thermogenesis and mass rest rainning of consumingt ransfer , and three of deposition models were discussed. The result s show that the rate of deposition of pyrolyticcarbon is improved with multi-factor coupling physical fields , and the porous carbon-carbon preforms (260 mm ×60 mm ×20 mm) can be densified in one-cycle. C/ C composites with density of more than 1.7 g/ cm3 are obtainedwithin 20 h. Though optimizing the infilt ration conditions , some kinds of microst ructure of pyrolytic carbons can beobtained , ranging f rom rough laminar , smooth laminar , isot ropic and banded st ructure. Under the infilt ration conditions of 960 ℃and 0.1 kPa , the rough laminar of higher texture can be obtained. -
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