Ordinary Ceramics
- Main components: Clay, feldspar, quartz.
- Main crystalline phase: Mullite.
- Characteristics: Good processability and formability, low cost, high output. Besides being used in daily-use ceramics and porcelain, it is also widely used in electrical appliances, chemicals, construction, textiles, and other industrial sectors.
Alumina Ceramics
- Main components: Primarily Al₂O₃, containing a small amount of SiO₂.
- Classification: Based on Al₂O₃ content, it is divided into 75% alumina ceramics (also known as corundum-mullite ceramics), 95% alumina ceramics, and 99% alumina ceramics (also known as corundum ceramics).
- Characteristics: Good high-temperature resistance, usable up to 1950℃; excellent electrical insulation and wear resistance; microcrystalline corundum has extremely high hardness (second only to diamond).
- Applications: Widely used as refractory materials, such as refractory bricks, crucibles, thermocouple sleeves, cutting tools for quenched steel, metal drawing dies, spark plugs for internal combustion engines, rocket and missile fairings, and bearings, etc. Silicon nitride (Si·N·) ceramics
- Structure: A covalently bonded solid composed of Si·N· tetrahedra.
- Characteristics: High strength, specific strength, and specific modulus; hardness second only to diamond and boron carbide; low coefficient of friction; low coefficient of thermal expansion; high thermal shock resistance; high chemical stability.
- Applications: Used for parts with simple shapes and low precision requirements, such as cutting tools and high-temperature bearings; also used for parts with complex shapes and high dimensional accuracy requirements, such as mechanical seal rings.
Silicon carbide (SiC) ceramics
- Structure: A crystal bonded by highly energetic covalent bonds.
- Preparation: Formed by direct reduction of silica sand (SiO·) with coke at high temperatures.
- Characteristics: High high-temperature strength; excellent wear resistance, corrosion resistance, and creep resistance; high thermal conductivity, second only to beryllium oxide ceramics.
- Applications: Used in the manufacture of rocket nozzles, throats for casting metal, thermocouple sheaths, furnace tubes, gas turbine blades and bearings, pump seals, wire drawing dies, etc.
Zirconium Oxide Ceramics
- Crystal Transformation: Cubic phase – Tetragonal phase – Monoclinic phase. The transformation from tetragonal to monoclinic phase is very rapid, easily causing cracking in the product.
- Stabilization Treatment: Adding certain oxides (such as CaO, MgO, Y₂O₃, etc.) can form a stable cubic solid solution, called fully stabilized zirconia (FSZ); reducing the amount of added oxides, so that some oxides exist in the form of tetragonal phase, is called partially stabilized zirconia (PSZ).
- Characteristics: Partially stabilized zirconia has low thermal conductivity and good thermal insulation; a large coefficient of thermal expansion, close to that of metals used in engines; high bending strength and fracture toughness.
- Applications: In addition to use at room temperature, it has become a major candidate material for insulated diesel engines, such as engine cylinder liners, pushrods, piston caps, valve seats, cams, bearings, etc.