New Refractory Uses For Silicon Nitride Reported

Silicon Nitride and Related Materials

“…These facts, coupled with the high creep resistance of a material free from glass, an ability to withstand thermal shock based on a low thermal expansion (ϳ3 ϫ 10 Ϫ6 K Ϫ1 ), and resistance to attack by a wide range of molten metals, made the material immediately attractive for thermocouple sheaths and for handling molten aluminum. 9 Moreover, because the material was formed from two of the most readily available elements in the earth's crust, silicon and nitrogen, it should have been relatively inexpensive-factors outweighed in practice, however, by the energy costs of a slow, high-temperature process and the difficulties of achieving microstructural quality. 60 RBSN was selected as a major material of the early ARPA ceramic-turbine development program for use in the hottest zones of a ceramic gas-turbine engine (although the highest mechanical stresses were at the cooler rotor center).…”

“…By 1955, Si 3 N 4 was an accepted refractory material, with applications including a bonding phase for SiC and oxide refractories, a mold wash resisting attack by molten nonferrous metals, and a thermocouple sheath material withstanding Ͼ50 cycles of rapid (10 s) heating to 2500°F (1371°C), more than 4 times better than an equivalent Al 2 O 3 article. 9 The development of Si 3 N 4 ceramics as potential hightemperature structural engine materials markedly accelerated in the early 1960s, the outcome of a deliberate and structured search for new materials with good high-temperature properties, of which resistance to thermal shock was most important. This work led to the development, successful testing, and, in some cases, commercial marketing, of a wide range of Si 3 N 4 components for internal (piston and gas turbine) combustion engines.…”

Nitride Ceramics

“…The chemical formula was given as Si 3 N 4 but it remained a chemical curiosity to researchers, mainly in Germany, until over forty years later, when refractories utilising silicon nitride as a bond for silicon carbide and other materials were developed (Wroten, 1954). At the same time, silicon nitride with good thermal stability was developed for use as thermocouple tubes, crucibles for molten metals and also rocket nozzles (Collins and Gerby, 1955). This type of material was formed by nitriding silicon powder compacts and was later termed reaction-bonded silicon nitride (RBSN).…”

Formation of a nanocomposite from plasma enhanced chemical vapour deposition multilayer structures

“…Crystalline silicon nitride is one of the most studied ceramic materials because of its qualities as a refractory electrical insulator, its high-temperature strength, good thermal shock resistance and chemical inertness [1,2]. The most common polymorphs of crystalline silicon nitride are the a and b phases, which both have hexagonal crystal structures.…”