Common ceramic material properties and the use of
(A) Introduction
Late 20th century with many new technologies (such as electronic technology, space technology, laser technology, computer technology, etc.) rise, as well as basic theory (such as mineralogy, metallurgy, physics, etc.) and testing techniques (such as electron microscopy, X-ray diffraction techniques and a variety of spectrum analyzers, etc.) development, people between structure and properties of materials with a deeper understanding of the relationship. By controlling the chemical composition and microstructure, developed a number of ceramic materials with different properties, such as various functional ceramics (electronic materials, fiber optics, sensitive ceramic material) and high temperature structural ceramics. Compared with the traditional ceramic materials have been hundreds of times its strength improve, coupled with the ceramic material itself has excellent high temperature, wear resistance, corrosion resistance, insulation and other characteristics, so that in many important fields has been more and more widely used.
Ceramic materials are mainly used on the process comprising: a metal (with a similar transition metals or metal) and boron, carbon, silicon, nitrogen, oxygen and other non-metallic elements of the compound, and a compound composed of non-metallic elements, such as boron and silicon, carbides and nitrides.
According to the composition of its elements can be divided into: oxide ceramics, nitride ceramics, carbide ceramics, ceramic silicides and borides ceramics. In addition, in recent years, the glass ceramics as structural materials have also been widely used.
(Two) oxide ceramics
Atoms oxide ceramic material based ionic bond, there is some covalent bond, it has many excellent properties. Most oxide has a high melting point, good electrical insulation properties, in particular excellent chemical stability and resistance to oxidation, in the process areas have been more widely used.
(1) alumina ceramics
Also known as corundum alumina ceramic porcelain, generally α-A1203 main phase. A1203 and additives according to the type of content, a different series. As can be divided into different levels according A1203 75 porcelain, 85 porcelain, 95 porcelain, 99 porcelain; according to its main crystalline phase can be divided into mullite, corundum - mullite corundum ceramics and porcelain; according to the different additives divided chrome corundum, corundum and other titanium.
Al203 ceramic refractory oxide is chemically most stable one of the highest mechanical strength; A1203 ceramics and reflect most of the molten metal does not occur, and only Mg, Ca, Zr and Ti are at a temperature above its reduction; hot sulfuric acid to dissolve A1203, hot HCl, HF has some of its corrosive effect; A1203 ceramics of the vapor pressure and decompression are minimal. Since A1203 ceramic excellent chemical stability, can be widely used acid pump impeller, pump, pump cover, sleeve, lined pipes conveying acid and valves.