ABSTRACT
In recent years it has become clear that advancements in system and device performance are critically dependent upon development of advanced materials with enhanced physical and mechanical properties [1,2]. No longer can metallic materials meet all of these requirements, particularly when high hardness and exposure to high temperature are necessary. For such challenging applications, ceramic materials are especially suitable. Compared to metals, ceramics typically have higher melting points and lower density. However, conventional ceramics have very low fracture toughness (i.e., brittle) leading to their poor reliability. To utilize the unique capabilities of ceramics, a great deal of research is going on in order to improve upon their reliability by fabricating composites with the addition of second or more phases in the matrix. By "composites" we mean an intimate mixture of materials, formed into a desired shape. The composite contains a "primary" or "matrix" phase (in the present case a ceramic called a "ceramic matrix composite," CMC) in which other phases with appropriate properties are added; here "appropriate" means, for example, materials of enhanced levels of properties such as higher strength or stiffness. By doing this, an enhanced combination of properties are obtained in the composite material, compared to those of the original matrix material.
