High temperature structural ceramic materials manufactured by the CNTD process

Controlled Nucleation Thermochemical Deposition (CNTD) has emerged from classical chemical deposition (CVD) technology. This paper describes the techniques of thermochemical grain refinement. The effects of such refinement on mechanical properties of materials at room temperature and at elevated temperatures are outlined. Emphasis is given to high temperature structural ceramic materials such as SiC, Si₃N₄, AiN, and TiB₂ and ZrB₂. An example of grain refinement accompanied by improvements in mechanical properties is SiC. Grain sizes of 500 to 1000 Å have been observed in CNTD SiC with room temperature MOR of 1380 to 2070 MPa (4 pt bending) and MOR of 3450 to 4140 MPa (4 pt bending) at 1350°C. Various applications of these materials to the solution of high temperature structural problems are described.