(UPDATE)Precision Ceramic

Carbide

  Tantalum carbide is a non-oxide ceramic material that is often used because it is better than ordinary ceramics.

Because of its hardness, heat resistance, oxidation resistance, corrosion resistance and high thermal conductivity, in recent years, tantalum carbide has been widely used in structural parts in mechanical engineering and seals in chemical engineering, etc., even in strong acid and strong Environments with extreme conditions such as alkali, high wear, high temperature, and aerospace.

 Zirconia

  Atmospheric pressure sintering of tantalum carbide is composed of α-SiC crystals, and the bulk density can reach 98% of the theoretical density.

(3.1g/cm3), the density is 1/5 of tungsten carbide hard alloy, the hardness is second only to diamond drill, anti-particle grinding

The performance of the damage is very good. S-SiC and graphite pairing are currently the pair of seals with the highest PV value.

High-purity atmospheric-pressure sintered niobium carbide (>98% SiC) can resist the corrosion of various chemical media such as acid and alkali at high temperature.

Eclipse, S-SiC has a very high specific strength, and is also excellent in high temperature oxidation resistance and high temperature mechanical properties.

Alumina

  In addition to precision ceramics, it should have high strength, hardness, high temperature resistance, acid and alkali corrosion resistance and high chemical stability.

Under the conditions, zirconia also has higher toughness than ordinary ceramics, making zirconia also used in various industries.

Industry, such as shaft seal bearings, cutting components, molds, automotive parts, etc., even for the human body, like

Among the artificial hip joints.

Aluminium nitride (AlN)

Aluminium nitride (AlN)is a solid nitride of aluminium. It has a high thermal conductivity of up to 285 W/(m·K), and is an electrical insulator. Its wurtzite phase (w-AlN) has a band gap of ~6 eV at room temperature and has a potential application in optoelectronics operating at deep ultraviolet frequencies

It can be stabilized to 2200 ° C and the strength will gradually decrease with increasing temperature.

It has good thermal conductivity and a small coefficient of thermal expansion and is a good thermal shock resistant material.

It has strong resistance to molten metal corrosion and is an ideal tantalum material for casting pure iron, aluminum or aluminum alloy. Aluminum nitride is also an electrical insulator with good dielectric properties and is also expected to be used as an electrical component.

The aluminum nitride coating on the gallium arsenide surface prevents it from being ion implanted during the annealing process. Aluminum nitride is also a catalyst for converting hexagonal boron nitride into cubic boron nitride. It reacts slowly with water at room temperature. It can be synthesized from aluminum powder at 800 to 1000 ° C in an ammonia or nitrogen atmosphere. The product was a white to grayish blue powder. The synthesis was carried out at 1600 to 1750 ° C by an Al 2 O 3 -C-N 2 system, and the product was an off-white powder. Or aluminum chloride and ammonia are obtained by gas phase reaction. The coating can be synthesized from the AlCl3-NH3 system by vapor deposition.

Silicon Nitride (Si3N4)

Cerium nitride (Si3N4) is a very hard solid material that can be obtained by heating silicon powder in nitrogen or reacting silicon halide with ammonia. Si3N4 is the main component of tantalum nitride ceramics, and it has relatively high vibration resistance compared to other ceramics.

Due to its high temperature resistance, corrosion resistance, wear resistance and unique electrical properties, tantalum nitride ceramics are used in aerospace military, mechanical engineering, communications, electronics, automotive, energy, chemical and biological fields.

Especially in the field of high-temperature structural ceramics, tantalum nitride ceramics have the best comprehensive properties, the most potential applications and new materials eager to replace nickel-based alloys, and have been widely used in high temperature fields.

The characteristics are as follows:

  1. Heat resistance. Under normal pressure, Si3N4 has no melting point and directly decomposes around 1870 °C. It has oxidation resistance at 1400 ° C and can be used at temperatures up to 1200 ° C (over 1200 ° C).
  2.  the coefficient of thermal expansion is small (2.8-3.2) × 10-6 / ° C, high thermal conductivity, good thermal shock resistance, thermal shock from room temperature to 1000 ° C will not break.
  3. the friction coefficient is small (0.1), and it has self-lubricity (the friction coefficient of the oiled metal surface is 0.1~0.2).
  4. chemical stability, corrosion resistance, in addition to hydrofluoric acid does not react with other inorganic acids, in 800 ° C, 800 ° C above the dry atmosphere does not react with oxygen, the formation of yttrium oxide film on the surface with increasing temperature The high cerium oxide film is gradually stabilized, and a dense cerium oxide film can be formed under oxygen of about 1000 °C. It can be stable at temperatures up to 1400 °C.
  5. the hardness and wear resistance of tantalum nitride, Mohs hardness is second only to diamond, cubic boron nitride, boron carbide, tantalum carbide, anti-mechanical impact.
  1. Tantalum nitride is a difficult-to-dense covalent bond compound. Sometimes additives need to be added. The density is about 3.4 (different molding methods have different densities, and the density of hot press forming is higher. The density of steel is about 7.85. The density of titanium alloy is about 4.5, the unit is g / cm3).
  2. Fragile, can be toughened with tantalum nitride fiber to stabilize its high temperature strength.

boron carbide

Alias ​​black diamond, molecular formula B4C, usually grayish black powder. It is one of the three hardest materials known (the other two are diamond, cubic boron nitride)

Used in tank armor, body armor and many industrial applications. Its Mohs hardness is 9.3

Boron carbide can absorb large amounts of neutrons without forming any radioisotopes, so the main use of ideal neutron absorbers and nuclear power plant neutron absorbers is to control the rate of nuclear fission. Boron carbide is mainly made into a controllable rod in the field of nuclear reactors, but sometimes it is powdery due to an increase in surface area.

Due to its low density, high strength, high temperature stability and good chemical stability. Used in wear resistant materials, ceramic reinforced phases, especially lightweight armor, reactor neutron absorbers, etc. In addition, compared with diamond and cubic boron nitride, boron carbide is easy to manufacture and low in cost, so it is more versatile and can replace expensive diamonds in some places, usually used for grinding, grinding, drilling and the like.

Hard black shiny crystals. Hardness is lower than industrial silicon carbide, but higher. Fragility is lower than most pottery. Has a large thermal energy neutron capture cross section. Strong chemical resistance. Free from the attack of hot hydrogen fluoride and nitric acid. Soluble in molten alkali, insoluble in water and acid. Relative density (D204) 2.508~2.512 melting point 2350 °C. Boiling point 3500 ° C

Boron nitride

Boron nitride is chemically resistant and is not attacked by mineral acids and water. The boron-nitrogen bond is broken in the hot concentrated base. Oxidation in the air begins above 1200 °C. The melting point is 3000 ° C, and when it is slightly lower than 3000 ° C, sublimation begins. The decomposition begins at a vacuum of about 2700 °C. Slightly soluble in hot acid, insoluble in cold water, relative density 2.25. The compressive strength is 170 MPa. The maximum use temperature in an oxidizing atmosphere is 900 ° C, and the maximum use temperature in an inert reducing atmosphere is 2800 ° C, but the lubricity is poor at normal temperature. Most of the properties of boron carbide are superior to carbon materials. For hexagonal boron nitride: low coefficient of friction, good high temperature stability, good thermal shock resistance, high strength, high thermal conductivity, low expansion coefficient, high electrical resistivity, corrosion resistance, microwave penetration or through infrared.

Leave a Comment

Your email address will not be published. Required fields are marked *