Ultra High Temperature Ceramics (UHTC)

With diboride, BB bond and MB bond are very strong and exist in all directions, so high hardness, temperature stability and isotropic Young's modulus of this material can be obtained. However, since corrosion means a large limit of ZrB 2, it has been thoroughly studied. Oxidation of ZrB 2 occurs at all temperatures in the presence of air. ZrB 2 (c) + 5 / 2O 2 (g) → ZrO 2 (c) + B 2 O 3 (1) Reaction 31 This is to be overcome by adding SiC as described herein You can do.

Structural problems are caused mainly by processes called oxidation and ablation. This occurs when very hot air and gas removes the surface layer from the metallic material of the aircraft or from objects moving at such a high speed. In order to solve this problem, materials called Ultra High Temperature Ceramics (UHTC) are required in aircraft engines and hypersonic aircraft such as rockets, reentry spacecraft and defense projectiles. However, at the present time even the traditional UHTC can not meet the relevant ablation requirements for driving at such extreme speeds and temperatures. However, compared with existing UHTC, researchers at the University of Manchester and the Royce Institute, in collaboration with Central South University, designed and manufactured a new type of cemented carbide coating that can withstand temperatures up to 3,000 ° C.

Flying countries by hypersonic flight has not yet been realized. The main problem here is fever. At Mach 5 or higher speed, it can reach ultra high temperature of 3600F to 5400F. At these extremely high temperatures, what happens is to remove the layer from the metal. Even the most toughest tile can not deal with this situation. However, the Chinese recently designed 12 times better carbide-based ceramic coating than ordinary ceramic coating. This can make hypersonic flight a reality

Ceramic is wonderful. It is very sturdy, has amazing heat absorption capacity, and is stable at high temperature. Even if not, ceramics may be an excellent raw material for materials and biomaterials. Commonly manufactured ceramic structures allow it to easily propagate even very small structural defects therein, "diffusing" the cracks through the ceramic solid layer.

In general, ceramics are stronger than metals at high temperatures, but because they are brittle and susceptible to defects, consistency and reliability as structural materials are questioned. Phase ceramics, also called MAX phase, can heal crack injury automatically by unique healing mechanism. Microcracks caused by wear and thermal stress fill the oxide formed by the MAX phase component (usually element A) while exposed to high temperature air. Crack filling of Ti 3 AlC 2 was first demonstrated by oxidation at 1200 ° C. in air. Ti 2 AlC and Cr 2 AlC also show this capability and it is expected that more ternary carbides and nitrides can self-recover spontaneously. This process is repeatable until the elements are exhausted and distinguishes MAX phases from other self-healing materials that require external repair agents (external repair) to fill single cracks.