Name: Titanium nitride
Appearance: The powder is generally yellowish brown, the ultra-fine titanium nitride powder is black, and the titanium nitride crystal is yellow and has a metallic luster.
Melting point: 2930℃
Density: 5.43 ~ 5.44g/cm3
Microhardness: 2160kg/mm2
Mohs hardness: 8 ~ 9
Coefficient of thermal expansion: 6.81*10-6/℃ (room temperature)
Thermal conductivity: 29.31W/(m*K)(room temperature)
Resistivity: 22*10-6Ω*cm (room temperature)
Molecular weight: 61.89

Chemical properties: Titanium nitride has high chemical stability. Under normal circumstances, it does not work with water, water vapor, hydrochloric acid, sulfuric acid, etc., but it has a certain solubility in hydrofluoric acid. If hydrofluoric acid co-exists with oxidants such as HF+HNO3,HF+KMnO4, etc., titanium nitride can be completely dissolved. In a strong alkali solution, titanium nitride decomposes to release ammonia gas.
TiN has a typical nacL-type structure, belonging to a face-centered cubic lattice. The top of the face-centered cube is nitrogen atom, and the titanium atom is located in the (1/2,0,0) spatial position of the face-centered cube. TiN is a non-stoichiometric compound, and its stable composition ranges from TiN0.6 to TiN1.16, and the nitrogen content can change within a certain range without causing changes in TiN structure. TiN powder is generally yellowish brown, ultrafine TiN powder is black, and TiN crystal is golden yellow. The lattice constant of TiN is a= 4.23nm, the lattice constant of TiC is a= 4.238nm, and the lattice constant of TiO is a= 4.15nm. The lattice parameters of these three substances are very close, so the nitrogen atoms in TiN molecule can be replaced by oxygen and carbon atoms in any ratio to form a solid solution. The physical and chemical properties of titanium nitride are determined by the content of nitrogen, when the content of nitrogen is reduced, the lattice parameters of titanium nitride are increased, and the hardness will be micro-increased, but the shock resistance of titanium nitride will be reduced.
Synthesis method:
(1) Metal titanium powder or TiH2 direct nitriding method
With titanium powder in nitrogen or hydrogen atmosphere, at 1273~1673K nitriding 1~4h, the product is crushed after repeated operation several times, can get stoichiometric titanium nitride powder, the equation is:
2Ti+N2=2TiN
It can also be nitrided with the metal hydride TiH2, which can react below 1273K, the equation is:
2TiH2+N2=2TiN+2H2
The advantage of this method is that it is simple to operate and can obtain high-quality titanium nitride powder, but the disadvantage is that the raw material price is too high, can not be mass-produced, and this process is easy to produce powder sintering phenomenon, resulting in losses.
(2) TiO2 carbonothermal reduction nitriding method
The carbon thermal reduction nitriding method of TiO2 uses TiO2 as raw material and carbon graphite as reducing agent to react with N2 to produce TiN. The synthesis temperature is 1380~1800℃, and the reaction time is about 15h. In this reaction environment, carbon not only reacts with oxygen, but also reacts with titanium to form TiC, because the lattice of titanium carbide, titanium nitride and titanium oxide are very close, and the three are easy to form a solid solution.
The TiN obtained by this method is generally not high in purity, and the content of O and C is high. In order to obtain TiN with low content of O and C, higher reaction temperature and longer reaction time are needed.
In addition, some experts also use another method, that is, magnesium powder and titanium oxide at a lower temperature under a certain proportion of mixed reaction to produce titanium nitride.
(3) Microwave carbothermal reduction method
Microwave carbothermic reduction is a REDOX reaction with inorganic carbon as reducing agent at high temperature. In China, Liu Binghai et al. prepared titanium nitride powder by this method. The specific operation is as follows: Using titanium oxide as raw material, the carbon is heated by microwave until the temperature reaches 1200℃, and the reduction reaction is maintained at this temperature for 1h, and the titanium nitride powder is obtained.
The titanium nitride powder obtained by this method has higher purity compared with the conventional method, and has the advantages of low synthesis temperature (100 ~ 200℃ lower than the original), short period (1/15 of the conventional method) and so on.
(4) Chemical vapor deposition method
The chemical vapor deposition method uses gaseous TiCl4 as raw material, H2 as reducing agent and N2 to produce TiN, and the synthesis temperature is 1100~1500℃. The coating of metal and ceramic surface is used in this process to enhance the hardness and wear resistance of ceramics and metals.
This synthetic TiN has high purity, but low production efficiency and high cost. This process is a common method for coating TiN film on the surface of metals, ceramics and other items to make them beautiful
(5) Self-propagating high temperature synthesis method
Self-propagating high temperature synthesis is also called combustion synthesis. In this method, titanium powder (billet) is directly ignited in nitrogen (limited to a certain pressure), and titanium powder is burned in nitrogen to obtain TiN products. This process has been extensively studied and commercialized in Russia, the United States, and Japan.
According to domestic research reports in this regard, Wang Weimin et al. used this process to prepare TiN ceramic powder, and studied the influence of process parameters such as compact density, diluent and nitrogen partial pressure on synthesis. Liu Suying and others have also studied this process.
(6) mechanical alloying method
Mechanical alloying method is to place titanium powder in the system of ammonia or nitrogen, and use a high-energy ball mill to make them interact under the strong collision and agitation of the mill ball to obtain nano titanium nitride, which is a new synthesis method. In China, Liu Zhijian et al. used TiH1.924 powder instead of Ti powder to react with nitrogen, and adopted this high-energy ball milling process. After high-energy ball milling in flowing ammonia for 100h, almost all TiH1.924 was converted into TiN, and the conversion rate was greatly improved. And Zhou Li et al. later used the same method to prepare nano titanium nitride powder, the reaction time is only 9h.
(7) Molten salt synthesis method
The synthesis of molten salt has not been reported in the preparation of titanium nitride, but it is a good research direction to study the preparation of titanium nitride by this method. This method is to use a low melting point of molten salt as the reaction medium, the reactant can be dissolved in the molten salt, the whole reaction is completed in the atomic level environment, after the completion of the reaction, with the appropriate solvent to dissolve the salt, filter the product can be obtained.
The product obtained by this method has high purity, simple operation, short reaction time, no harsh requirements on reaction temperature, easy control of product morphology and particle size, and no agglomeration phenomenon.
(8) Sol-gel method
Sol-gel method is to mix the reactants evenly in the liquid phase, and then carry out the process of hydrolysis and condensation, the reactants will form transparent sol in the solution, the sol will form gel after aging and slow polymerization process, and the gel will be dried and cured to get the material we need.
Application field:
(1) Titanium nitride has high biocompatibility and can be applied to clinical medicine and stomatology. The material is non-toxic and FDA compliant, so it is also commonly used in medical devices, such as maintaining the sharpness of the edges of scalpel blades and orthopedic bone saws, or directly as implants (especially hip replacement implants) and other medical implants.
(2) Titanium nitride has a low friction coefficient and can be used as a high-temperature lubricant. The coating is also used in aerospace and military applications, as well as to protect the sliding surfaces of the suspension of bicycles and motorcycles, and even the shock absorbers of remote control toy cars.
(3) titanium nitride has a metallic luster and can be used as a simulated gold decoration material, which has a good application prospect in the gold decoration industry; Titanium nitride can also be used as gold paint in jewelry industry; It can be used as a potential material to replace WC, so that the application cost of materials is greatly reduced.
(4) Has super hardness and wear resistance, can be used to develop a new type of tool, this new type of tool than ordinary carbide tool durability and service life are significantly improved. Titanium nitride coatings are widely used on metal edges to maintain corrosion resistance in mechanical molds, such as drills and milling cutters, often improving their life by increasing three or more factors.
(5) Titanium nitride is a new type of multi-functional ceramic material. The addition of a certain amount of titanium nitride to the TiC-Mo-Ni series of cermet will significantly refine the hard phase grains, so that the physical properties of the ceramics have been greatly improved at room temperature or under high temperature conditions, and then the high temperature corrosion resistance and oxidation resistance of cermet have been greatly improved; The strength, toughness and hardness of ceramics can be enhanced by adding TiN powder to ceramics in a certain proportion. Nano-titanium nitride is added to TiN/Al2O3 composite phase nano-ceramics, and it is mixed evenly by various methods (such as mechanical mixing method), and the conductive network is formed inside the ceramic material containing nano-titanium nitride particles. This material can be used as an electronic component in the semiconductor industry.
(6) Adding a certain amount of TiN to magnesia-carbon bricks can greatly improve the slag erosion resistance of magnesia-carbon bricks.
(7) Titanium nitride is an excellent structural material that can be used for steam jet thrusters and rockets. Titanium nitride is also used in the field of bearings and sealing rings, highlighting the excellent application effect of titanium nitride.
(8) Based on the excellent conductive properties of titanium nitride, it can be made into various electrodes and contact materials.
(9) Titanium nitride has a high superconducting critical temperature and can be used as an excellent superconducting material.
(10) Titanium nitride has a melting point higher than most transition metal nitrides and a density lower than most metal nitrides, making it a unique refractory.
(11) The glass coated with titanium nitride film is still a new "thermal mirror material", when the thickness of the film is greater than 90nm, the infrared reflectivity is greater than 75%, improving the thermal insulation performance of the glass. The color of titanium nitride film can also be adjusted at will, with the reduction of nitrogen content, the film will show gold, bronze, pink and other colors, very beautiful. At present, due to the development of nitrogen-containing cermet tools, the demand for titanium nitride powder has increased sharply. Moreover, the international gold decoration technology has developed very fast, and the application of titanium nitride in this respect has a very broad prospect. Titanium nitride can be used as a film plated on glass, in the case of infrared reflectivity greater than 75%, when the thickness of titanium nitride film is greater than 90nm, it can effectively improve the insulation performance of glass. In addition, adjusting the percentage of nitrogen in titanium nitride can change the color of titanium nitride film, so as to achieve the ideal aesthetic effect. Titanium nitride (TiN) is a fairly stable compound, does not react with iron, chromium, calcium and magnesium and other metals at high temperatures, TiN crucible in CO and N2 atmosphere does not work with acidic slag and alkaline slag, so TiN crucible is an excellent container for studying the interaction between liquid steel and some elements. TiN loses nitrogen when heated in a vacuum and produces titanium nitride with lower nitrogen content.
(12) Titanium nitride films can be used in the field of microelectronics as a conductive barrier between active devices and metal contacts. When the film is diffused into metallic silicon, its conductivity (30-70μΩ·cm) is sufficient to form a good conductive connection.
TiN has attractive golden color, high melting point, high hardness, good chemical stability, small wetting with metal structural materials, and has high electrical conductivity and superconductivity.
It can be applied to high-temperature structural materials and superconducting materials. Titanium nitride is a new type of multi-functional cermet material with high melting point, high hardness and small friction coefficient, which is a good conductor of heat and electricity. First, titanium nitride is an excellent structural material for high-strength cermet tools, steam jet thrusters, and rockets. In addition, titanium nitride has a low friction coefficient and can be used as a high-temperature lubricant. Titanium nitride as bearings and sealing rings can show excellent results. Titanium nitride has high electrical conductivity and can be used as electrodes for molten salt electrolysis, point contacts, film resistors and other materials. Titanium nitride is an excellent superconducting material with high critical temperature of superconductivity. Especially eye-catching is that the titanium nitride coating and its sintered body have satisfactory gold and can be used as a gold substitute decoration material with good imitation gold effect, decorative value and anti-corrosion, prolong the life of the handicraft. At present, due to the development of nitrogen-containing cermet tools, the need for titanium nitride powder has increased sharply, and the international gold decoration technology has developed quite fast. Not only because the titanium nitride coating is cheap, but also because it is better than the vacuum coating in terms of corrosion resistance and friction resistance.