Let me introduce you to the characteristics of non alumina ceramics
Non-alumina ceramics is a general term for ceramics made from metal carbides, nitrides, sulfides, silicides, borides, etc. With the continuous development of science and technology, materials are required to have a great many characteristics. Non-alumina ceramic materials have achieved remarkable development in recent decades, which has greatly promoted the progress of modern high-tech. They play a huge role in promoting the progress of human society and have made indelible contributions to economic development and national defense construction.
Characteristic：
① The raw materials are rarely found in nature, and artificially synthesized raw materials are required.
② When synthesizing the raw materials and sintering the ceramics, oxides are likely to be generated, and the processes must be carried out under a protective atmosphere (such as Ar and N₂).
③ Non-oxides generally have covalent bonds with very strong bond energy, so they are refractory or difficult to sinter.
Different from alumina ceramics, the atoms in non-alumina ceramics are mainly bonded together by covalent bonds. Therefore, they have high hardness, modulus, and creep resistance, and can maintain these properties to a large extent at high temperatures, which is unparalleled by oxide ceramics. The disadvantage is that the sintering of non-alumina ceramics is generally difficult. High-density products can only be obtained under extremely high temperatures (1500-2500 °C) and in the presence of sintering aids. Sometimes, hot-pressing sintering method must also be used to achieve the desired density (>95%). This results in the production cost of non-alumina ceramics generally being higher than that of alumina ceramics.
Some of these ceramic materials, such as Si₃N₄, SiC, etc., are likely to be applied in high-efficiency engines and gas turbines, which has aroused the great interest of scientific researchers. This is because it is closely related to the energy issues that industrialized countries with advanced technologies are urgently seeking to solve. However, as new types of materials, these non-alumina ceramics are also materials with unique charm.
Among non-oxides, carbides and nitrides are remarkable as structural materials. This is because most of the types of atomic bonds in these materials are covalent bonds, so they have strong resistance to deformation at high temperatures.
Non-oxides are different from alumina. They rarely exist in nature and require artificial synthesis of raw materials, which are then processed into products according to ceramic manufacturing techniques. During the synthesis process of the raw materials, it is essential to avoid contact with oxygen. Otherwise, oxides will be produced first instead of the expected nitrides or carbides. Therefore, both the synthesis of these non-oxide raw materials and their sintering must be carried out in a protective gas (nitrogen or inert gas) to prevent the formation of oxides, which could affect the high-temperature properties of the materials.