Titanium carbonitride material has excellent characteristics such as high melting point, high strength, strong wear resistance, corrosion resistance and oxidation resistance. It has the advantages of tic and tin. In addition to being very suitable for high-end precision processing and near net forming processing, on the basis of maintaining the characteristics of tic, the brittleness of TiC has been significantly improved due to the introduction of n. With the increase of N content, the hardness decreases and the toughness increases. Because of its excellent comprehensive properties, titanium carbonitride based ceramics have been widely used in cutting fields, high temperature resistant materials, measuring tools, petroleum and chemical industry, clock appearance and other fields.
Preparation of titanium carbonitride powder
1. High temperature solution method
Ti(C, N) powders are prepared by high temperature solid solution method, which is usually formed by a certain amount of TiN and TiC powders mixed uniformly at 1700 ~ 1800℃, or by solid solution in Ar or N2 atmosphere at higher temperature. In order to restrain grain growth and improve powder activity and sintering performance, the solution temperature can be appropriately reduced. Even if the solution temperature is reduced, the high temperature solution method has some disadvantages, such as high reaction temperature, high energy consumption, difficult to obtain high purity powder, and difficult to accurately control the N/C ratio.
2. High temperature nitriding of TiN and C powder
High temperature nitriding method is usually based on TiN powder and C powder as raw materials, mixed in high temperature and N2 or Ar atmosphere for a long time to get Ti(C, N) powder. Frederic et al. used nano-sized TiN powder +10wt% carbon black to hold for 3h at 1430℃ in Ar air flow, and formed Ti(C, N) powder with solid phase, exhibiting regular shape sub-micron particles. Similarly, high temperature nitriding has the disadvantages of high reaction temperature, low production efficiency, high energy consumption and high production cost.
3. TiO2 carbon thermal reduction nitriding
Carbon thermal reduction nitride is a process of synthesis of Ti(C, N) powder by high temperature reduction in N2 with TiO2 and C powder as raw materials. The size and morphology of the product of carbon thermal reduction can be controlled by process parameters, which is widely used in industrial large-scale production.
4. Sol-gel method
The sol-gel method is to use TiO(OH)2 sol as Ti source, mix and disperse carbon black in liquid phase, and get Ti(C, N) powder by high temperature heat treatment under N2 after a series of reactions. Some researchers obtained Ti(Cx, N1-X) from the gel formed by mixing TiO(OH)2 sol with nano carbon black after drying and reacting at 1400 ~ 1600℃ under N2 atmosphere, in which 1-x=0.2 ~ 0.7, the average particle size of Ti(Cx, N1-x) ultrafine powder was less than 100nm. The x value can be improved by increasing the C/Ti ratio of raw materials, increasing the reaction temperature, prolonging the holding time and reducing the nitrogen flow rate.
5. ammonia solution
In ammonolysis, TiCl4 is usually dissolved in an appropriate solvent and added with additives at room temperature. After being mixed evenly, TiCl4 reacts with NH3 to generate a evenly mixed intermediate of Ti's amine group compound and additives. Then the intermediate is mixed with NH4Cl solution to precipitate and remove the amine in the intermediate. Ti(C, N) powders were prepared by pyrolysis at 1200 ~ 1600℃ in vacuum or Ar atmosphere. The characteristic of ammoniation method is that the preparation temperature is lower than the traditional preparation method (high temperature solution method, 1800℃). The Ti(C, N) powder obtained has the advantages of high specific surface area, small particle size, concentrated particle size distribution and high purity, but the cost is high and the process is complicated.
6. High temperature self-propagating reaction
The high temperature self-propagating reaction method is to evenly mix Ti powder and C powder, prepress forming to get the blank, and then in the device containing N2 "ignite" reaction at high temperature, so as to get the bulk product, through the fragmentation refinement can get Ti(C, N) powder.
7. Plasma chemical vapor deposition
Ti(C, N) plasma chemical vapor deposition is usually used to activate TiCl4 reaction gas by plasma to promote its chemical reaction on the surface of the substrate or near the surface space to generate Ti(C, N) solid film. Later, in order to avoid TiCl4 corrosion of the reaction vessel and pollution to the environment, chlorine free Ti organic matter is often used to replace TiCl4. This type of Ti - containing organic compounds mainly include tetramethyl titanate, tetraethyl titanate, tetraisopropyl titanium, tetrabutyl titanate and titanium amine, etc.
8. High energy ball milling-induced self-propagating synthesis
As a powder processing method, high-energy ball milling can not only uniformly mix and activate powder to reduce sintering reaction temperature and promote alloying, but also induce self-propagating reaction to synthesize nano Ti(C, N) powder at room temperature. The technique of high energy ball milling induced self-propagating synthesis of Ti(C, N) integrates powder mixing and reaction, overcomes the traditional high temperature conditions, and can directly obtain Ti(C, N) powder.
Application of titanium carbonitride
1. Ti(C, N) base ceramic cutting tools
Ti (C, N) fund of ceramic is a kind of very important structural materials, with its, compared to the preparation of the cutting tool with WC cemented carbide processing in develop high red hardness, similar intensity, low corrosion resistance, thermal conductivity and coefficient of friction, has the high life or in the life the same situation can use high cutting speed, The machined workpiece has a good surface finish. It is understood that Japan's Ti(C, N) fund ceramic tool materials have accounted for more than 30% of the market share of all tool materials.
2. Ti(C, N) fund ceramic coating
Ti(C, N) base ceramics can be made into wear-resistant coatings and die materials. Ti(C, N) coating has excellent mechanical and tribological properties. As a hard wear resistant coating, Ti(C, N) coating has been widely used in cutting tools, drills and molds, and has broad application prospects. Its preparation technology mainly includes plasma chemical vapor deposition, medium temperature chemical vapor deposition, traditional CVD method and so on. Ti(C, N) fund ceramics as mold materials, compared with die steel, has no phase change, high temperature resistance, low friction coefficient and good adhesion resistance, and has a certain strength and toughness, is a potential mold materials.
3. Multiphase ceramic materials
Ti(C, N) can be combined with other ceramics to form composite materials, such as Ti(C, N)/Al2O3, Ti(C, N)/SiC, Ti(C, N)/Si3N4, Ti(C, N)/TiB2 and other multiphase ceramic materials. As reinforcement, Ti(C, N) can improve the strength and fracture toughness of materials. It can also improve electrical conductivity.
4. Refractory materials
The addition of non - oxides to refractories will bring some excellent properties. Some studies show that the existence of titanium carbonitride can obviously improve the performance of refractory.
5. Synthesis of Ti(C, N) whiskers
As early as 2011, The 2d titanium carbide material was first prepared by Drexel University, and it was found that this material has many special properties, including high strength, high conductivity and molecular filtration ability. The property of titanium carbide was that it could block and absorb electromagnetic interference more effectively than any known material at the time, including the foil used in most electronic devices today.
When Drexel went on to examine other members of the family, they found that titanium nitride had even more excellent properties, making it a more promising candidate for shielding electromagnetic interference. This also means that titanium nitride can be used to individually coat components inside devices to contain their electromagnetic radiation, even when they are placed close together. Companies like Apple have been trying this containment strategy for years, but the success rate is limited by the thickness of the copper foil. This strategy is likely to become the new standard as device designers strive to make devices ubiquitous by making them smaller, less visible and more integrated.
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