SYNTHESIS AND CHARACTERIZATION OF CONTINUOUS FIBER-BONDED CERAMIC COMPOSITES

聚合物衍生的碳化硅系统纤维作为陶瓷基复合材料的增强纤维具有重要的应用价值。这些纤维含有大量的氧和碳，超过了碳化硅的化学计量比，处于无定形状态。由于纤维在高温(1300ﾟC以上)下热力学不稳定，它们容易结晶成β-碳化硅，产生SiO和CO气体。这种热解会导致纤维强度显著降低。然而，我们发现表面氧化膜的存在明显地抑制了纤维的热解。在这项研究工作中，详细地研究了这些纤维包覆氧化层的热稳定性。在此基础上，研究了氧化铝坯体纤维的热解行为。氧质量分数为13%的Si-Ti-C-O纤维在1300ﾟC的氧气气流中进行热处理，得到了300-500 nm的氧化层。将其单向层状纤维片材在Ar气氛中1700ﾟ℃下进行热压，制备了连续纤维粘结陶瓷复合材料，利用格兰特-IN-AID公司购买的切割机((C)(2))，用扫描电子显微镜和透射电子显微镜观察了复合材料的表面、截面和微观结构。复合材料具有纳米级的结构。该复合材料在1300ﾟ-1500ﾟC氧气气氛中氧化，其增重率分别为0.02、0.06和0.07%，具有优良的抗氧化性能。

Polymer-derived SiC system fibers are of interest as reinforced fibers for ceramic-matrix composites. The fibers contain substantial amounts of oxygen as well as carbon, beyond the stoichiometric ratio of SiC,and are in an amorphous state. As the fibers are thermodynamically unstable at elevated temperatures (above 1300ﾟC), they have a tendency to crystallize into beta-SiC,generating SiO and CO gases. Such pyrolysis, results in remarkable reduction of fiber strength. However, we have found that the pyrolysis of the fibers are suppressed appreciable by the presence of the surface oxide film. In this research works, the thermal stability of these fibers coated with oxide layrs were investigated in detail. And then, the pyrolytic behavior of these fibers of alumina compact body was investigated. The pyrolysis of these fibers was suppressed by the presence of alumina powders.Si-Ti-C-O fibers with 13mass% oxygen were heat-treated in a stream of oxygen gas at 1300ﾟC,and the fibers coated with oxide layr of 300-500nm were obtained. Their unidirectional laminated fibers sheets were hot-pressed at 1700ﾟC in Ar, and continuous fiber-bonded ceramic composites were prepared.The composites were formed into several kind of shapes to observe its surface, cross-section and microstructure using SEM and TEM,with the cutting machine bought by GRANT-IN -AID FOR SCIENTIC RESEARCH ((C)(2)). The composites contained of nano-scale structure. The composites were oxidized at 1300ﾟ-1500ﾟC in oxygen atmosphere, and their mass gains were 0.02,0.06 and 0.07% respectively, and the composites are considered to be excellent for oxidation resistance.We continue to investigate the synthesis and severe environment properties of the developed fiber-bonded ceramic composites in detail.