SYNTHESIS AND CHARACTERIZATION OF CONTINUOUS FIBER-BONDED CERAMIC COMPOSITES

聚合物衍生的SiC系统纤维作为陶瓷基复合材料的增强纤维是令人感兴趣的。纤维含有大量的氧以及碳，超过SiC的化学计量比，并且处于非晶态。由于纤维在高温（1300摄氏度以上）下热力学不稳定，因此它们倾向于结晶成β-SiC，产生SiO和CO气体。这种热解导致纤维强度显著降低。然而，我们已经发现，纤维的热解被抑制明显的表面氧化膜的存在。本研究对这些纤维表面涂覆氧化物层后的热稳定性进行了详细的研究。然后，研究了氧化铝压坯中纤维的热解行为。在1300 ℃氧气气氛中对含氧13mass%的Si-Ti-C-O纤维进行热处理，得到了300- 500 nm的氧化物涂层。在1700 ℃氩气气氛中热压单向纤维层合片，制备出连续纤维结合陶瓷复合材料，用GRANT-IN -AID FOR SCIENTIC RESEARCH（（C）（2））公司的切割机将复合材料成型为多种形状，用SEM和TEM观察其表面、截面和微观结构。复合材料具有纳米结构。在1300 ℃ ~ 1500 ℃的氧气气氛中氧化，其增重分别为0.02，0.06和0.07%，具有良好的抗氧化性能。

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.