A team of researchers was recently successful in synthesizing one of the first transparent samples of a famous industrial ceramic. This resulted into a super-hard window abstracted out of cubic silicon nitride that can be used potentially for extreme temperatures such as power mills and so much more. Cubic silicon nitride is formed under very high pressure and is one of the second most hard and transparent nanoceramic that is right next to diamond. It has super ability to bear with highest temperatures. The lead author of this paper, Dr. Norisama Nishiyama who works at Deutsches Elektronen-Synchroton (DESY) who is currently also an associate professor at Tokyo Institute of Technology, says, “Silicon nitride is a very popular ceramic in industry. It is mainly used for ball bearings, cutting tools and engine parts in automotive and aircraft industry.”
Ceramic is known for being a highly stable substance given its silicon nitrogen bonds’ strength. At a pleasing temperature, silicon nitride has a hexagonal crystal structure, but the sintered ceramic of this state is an opaque one. When pressures exceed 130 thousand times of the normal atmospheric pressure, the silicon nitride attains a crystal structure that has cubic symmetry called spinel-type by specialists. It gets this name from the structure of a very famous gemstone. Artificial spinel is most popularly used in form of transparent ceramic in the industry.
Nishiyama further explains, “The cubic phase of silicon nitride was first synthesized by a research group at Technical University of Darmstadt in 1999, but knowledge of this material is very limited.” His team utilized a Large Volume Press (LVP) for exposing the hexagonal silicon nitride to high temperatures and pressures. When the pressure reached an approx. value of 150 thousand times of regular atmospheric pressure and a temperature equaling to 1800 degree centigrade, a transparent piece of cubic silicon nitride was finally formed that has diameter of some 2 millimeters. Nishiyama adds that it is one of the hardest transparent ceramics that has been built till date.
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