Ceramic Matrix Composites

(1) Definition and Compositional Characteristics of Ceramic Matrix Composites

Ceramic Matrix Composites (CMCs) are a class of novel materials characterized by their designable properties. They are fabricated using appropriate composite processing techniques, utilizing ceramic materials as the matrix and ceramic fibers, whiskers, platelets, or particles as the reinforcing phase.

(2) Classification of Ceramic Matrix Composites

Based on their functional performance characteristics, ceramic matrix composites can be classified into structural ceramic matrix composites and functional ceramic matrix composites.

Structural ceramic matrix composites primarily leverage their mechanical properties and high-temperature resistance, and are used to fabricate load-bearing components.

Their key characteristics include light weight, high strength, high stiffness, high specific modulus, high-temperature resistance, low thermal expansion, thermal insulation, and corrosion resistance.

Functional ceramic matrix composites primarily utilize their physical properties—such as acoustic, optical, electrical, magnetic, and thermal characteristics. They typically consist of a functional phase (either monofunctional or multifunctional) and a matrix; the matrix serves not only to bind and shape the material but also influences the overall performance of the composite ceramic. A multifunctional phase can endow the composite ceramic with multiple functions and may even give rise to novel functions through synergistic composite effects.

Based on the chemical characteristics of the matrix material, ceramic matrix composites can be classified into oxide ceramic matrix composites and non-oxide ceramic matrix composites. Oxide matrices primarily comprise simple oxides—such as SiO₂, Al₂O₃, and ZrO₂—and complex oxides, such as 3Al₂O₃•2SiO₂ (Mullite). Non-oxide matrices primarily consist of carbon (C); carbides—such as SiC, ZrC, and TaC; nitrides—such as Si₃N₄, BN, and AlN; and borides—such as TiB₂ and ZrB₂.

Based on the morphological characteristics of the reinforcing phase, ceramic matrix composites can be further classified into zero-dimensional (particulate), one-dimensional (fibrous), two-dimensional (platelet or planar fiber fabric), and three-dimensional (three-dimensional fiber fabric) composites.

The ceramic fibers commonly used as reinforcing phases include carbon (C) fibers, SiO₂ fibers (quartz fibers), SiC fibers, Si₃N₄ fibers, BN fibers, and Al₂O₃ fibers. Fibers, high-silica fibers, glass fibers, etc.