1. Definition of Advanced Ceramic Materials

    Advanced ceramic materials, also known as precision ceramic materials, refer to high-performance products manufactured using exquisite, high-purity, ultrafine inorganic compounds as raw materials and advanced preparation techniques.

    According to the requirements of engineering technology for product performance, manufactured products can have advantages su

ch as piezoelectric, ferroelectric, conductive, semiconductor, magnetic, or high strength, high toughness, high hardness, wear resistance, corrosion resistance, high temperature resistance, high thermal conductivity, insulation, or     good biocompatibility.

    2. Classification of advanced ceramic materials

According to different uses, advanced ceramic materials can be divided into structural ceramics, tool ceramics, and functional ceramics.

(1) Structural ceramics

    The main materials of structural ceramics include alumina ceramics (Al2O3), silicon nitride ceramics (Si3N4), silicon carbide     ceramics (SiC), hexagonal boron nitride ceramics (BN), etc.

1) Aluminum oxide ceramics (Al2O3)

    The main component of alumina ceramics is Al2O3, with a general content greater than 45%. Aluminum oxide ceramics have various excellent properties. High temperature resistance, generally suitable for long-term use at 1600 ℃, corrosion resistance, high strength, its strength is 2-3 times that of ordinary ceramics, and up to 5-6 times higher. Its disadvantage is that it is brittle and cannot accept sudden changes in environmental temperature. It has a wide range of uses and can be used as crucibles, engine spark plugs, high-temperature refractory materials, thermocouple sleeves, sealing rings, etc. It can also be used as cutting tools and molds.

2) Silicon nitride ceramics (Si3N4)

    The main component of silicon nitride ceramics is Si3N4, which is a high-temperature ceramic with high strength, high hardness, wear resistance, corrosion resistance, and self-lubricating properties. Its coefficient of linear expansion is the smallest among various ceramics, with a usage temperature of up to 1400 ℃. It has excellent corrosion resistance, except for hydrofluoric acid, it can withstand corrosion from various acids, as well as alkali and various metals. It also has excellent electrical insulation and radiation resistance. Can be used as high-temperature bearings, sealing rings for use in corrosive media, thermocouple sleeves, and also as metal cutting tools.

3) Silicon carbide ceramics (SiC)

    The main component of silicon carbide ceramics is SiC, which is a high-strength and high hardness high-temperature resistant ceramic that can maintain high bending strength even when used at 1200 ℃~1400 ℃. It is currently the ceramic with the highest high-temperature strength. Silicon carbide ceramics also have good thermal conductivity, oxidation resistance, conductivity, and high impact toughness. It is a good high-temperature structural material that can be used for components such as rocket tail nozzles, thermocouple sleeves, and furnace tubes that work at high temperatures; By utilizing its thermal conductivity, heat exchanger materials can be made at high temperatures; Utilize its high hardness and wear resistance to produce grinding wheels, abrasives, etc.

4) Hexagonal boron nitride ceramics (BN)

    The main component of hexagonal boron nitride ceramics is BN, with a crystal structure of hexagonal crystal system. The structure and properties of hexagonal boron nitride are similar to graphite, so it is called "white graphite". It has low hardness and can be machined with self-lubricating properties. It can be made into self-lubricating high-temperature bearings, glass forming molds, etc.

(2) Tool ceramics

The main materials of structural ceramics include hard alloy, natural diamond (diamond), cubic boron nitride (CBN), etc.

1) Hard alloy

    The main components of hard alloy are carbides and binders, with carbides mainly including WC, TiC, TaC, NbC, VC, etc. The binder is mainly cobalt (Co). Compared with tool steel, hard alloy has high hardness (up to 87~91HRA) and good thermal hardening (excellent wear resistance around 1000 ℃). When used as a tool, the cutting speed is 4-7 times higher than that of high-speed steel, and the service life is 5-8 times longer. Its disadvantages are high hardness and brittleness, making it difficult to machine. Therefore, it is often made into blades and welded onto the tool holder for use. Hard alloy is mainly used for mechanical machining tools; Various molds, including stretching molds, drawing molds, and cold heading molds; Mining tools, geology, and petroleum exploration use various types of drill bits.

2) Diamond Natural Diamond (Diamond)

    Natural diamond (diamond) is a precious decoration, while synthetic diamond is widely used in industry. Diamond is the hardest material in nature and also has a very high elastic modulus; Diamond has the highest thermal conductivity among known materials; Diamond has excellent insulation performance. Diamond can be used as drill bits, cutting tools, grinding tools, drawing dies, and trimming tools; Diamond tools can achieve mirror finish through ultra precision machining. However, diamond cutting tools have poor thermal stability and a high affinity for iron group elements, so they cannot be used to process iron and nickel based alloys. Instead, they mainly process non-ferrous metals and non-metals and are widely used in the processing of ceramics, glass, stones, concrete, gemstones, agates, and other materials.

3) Cubic boron nitride (CBN)

    Cubic boron nitride (CBN) has a cubic crystal structure and high hardness, second only to diamond. Its thermal and chemical stability is better than diamond, and it can be used for cutting difficult to machine materials such as quenched steel, wear-resistant cast iron, thermal spray materials, and nickel. Can be made into cutting tools, grinding tools, drawing dies, etc.

4) Other tool ceramics

    Other tool ceramics include alumina, zirconia, silicon nitride and other ceramics, but their comprehensive performance and engineering applications are inferior to the above three tool ceramics.

(3) Functional ceramics

    Functional ceramics usually have special physical properties and involve various fields. The characteristics and applications of commonly used functional ceramics are shown in the table.

Common functional ceramics:

3. Development history of advanced ceramic materials

  technology and large-scale integrated technology circuits cannot do without piezoelectric, ferroelectric, and magnetic ceramics; The memory system of electronic computers requires ferromagnetic ceramics with square hysteresis loops; The high-speed hard disk rotation system requires ceramic bearings; In the launch of rockets and missiles, the nose cone and transparent ceramic antenna cover are key components that must withstand the friction and erosion of high-temperature airflow. The material is required to have high high-temperature strength and good oxidation resistance, and only ceramic materials can meet these requirements; As a new energy source for magneto fluid generators, it is necessary to use ceramics as electrode materials; High temperature fuel cells and high-energy batteries require the use of ceramic block ion conductors as separator materials, etc.

  At present, advanced ceramics have formed a huge high-tech industry. The total sales of advanced ceramic products worldwide exceed 30 billion US dollars, with an annual growth rate of over 10%. The United States and Japan are in a leading position in this field. Advanced ceramic materials are playing an increasingly important role in high-tech industries, traditional industry transformation, and national defense and military industry due to their excellent high-temperature mechanical properties and unique optical, acoustic, electrical, magnetic, thermal, or functional composite effects.

--------Extracted from public information, content for reference only