Low-Cost Molybdenum Disilicide Matrix Composites

碳纤维增强碳化硅晶须增强二硅化钼（MoSi2）基复合材料已被确定为氧化环境下高温结构应用的优秀候选者。但这些材料的室温断裂韧性和高温屈服蠕变强度仍可大幅度提高，加工问题有待解决。在第一阶段的提案中，Ultramet提议证明几种MoSi2基复合材料制造方法的可行性，这些方法能够消除加工缺陷的主要来源，并大大提高工艺的可重复性和成本效益，同时提高机械性能。采用化学气相沉积（CVD）技术制备具有多种合金显微组织的mosi2涂层晶须和mosi2浸润碳织物，并进行性能测量。这些结果将与SiC/MoSi2、C/C和C/SiC材料的现有数据进行比较，并对成本、可靠性、可制造性和性能进行分析。MoSi2复合材料最直接的应用是发动机热段部件和工业炉具设备是另一个潜在的市场。此外，随着美国环保署即将出台大幅减排的要求，将需要更多的新材料，如MoSi2，以承受与清洁燃烧、低氮氧化物技术相关的更高温度。

Carbon fiber-reinforced in SiC whisker-reinforced molybdenum disilicide (MoSi2) matrix composites have been identified as excellent candidates for high temperature structural applications in oxidizing environments. However, the room temperature fracture toughness and high temperature yield and creep strength of these materials can still be drastically improved, and processing issues must be resolved. In this Phase I proposal, Ultramet proposes to demonstrate the feasibility of several fabrication methods for MoSi2 matrix composites that are capable of eliminating the major sources of processing flaws and of greatly increasing process repeatability and cost-effectiveness, while enhancing mechanical properties. MoSi2-coated whiskers and MoSi2-infiltrated carbon fabric will be fabricated by chemical vapor deposition (CVD) with several alloy microstructures, followed by properties measurements. These results will be compared to available data for SiC/MoSi2, C/C, and C/SiC materials, and an analysis of cost, reliability, fabricability, and performance will be conducted. The most immediate application for MoSi2 composites for engine hot section components, and industrial furnace equipment is another potential market. Also, with upcoming EPA requirements for drastically reduced emissions, new materials such as MoSi2 will be required in much greater quantities to withstand the higher temperatures associated with clean-burning, low-Nox technology.