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Eight standard synthetic methods of titanium carbide (TiC)

wallpapers Industry 2020-11-05
TiC has a high melting point, high electrical conductivity, small thermal expansion coefficient, high hardness, excellent oxidation resistance, and chemical stability. It can be introduced into refractory materials in additives to produce high strength, good thermal shock resistance, and composite refractory material with good molten iron erosion performance will be a material with excellent development prospects.
The synthesis methods of TiC mainly include the following:

(1) Direct carbonization method of metal titanium powder or TiH2 powder

Metal titanium powder or TiH2 powder direct carbonization method, which is the traditional method of preparing TiC. The process is to use the sponge-like titanium powder obtained by sodium reduction or a mixture of titanium powder (with a particle size of at least 5μm or less) and carbon black obtained by decomposition of titanium hydride (the carbon content of the mixture is 5% to 10% more than the theoretical amount, and (Dry mixing by ball mill) molding under the pressure of about 100MPa. Then put it into a graphite container, use a carbonization induction heating furnace, heat it to 1500~1700℃ in a high-purity (dew point below -35℃) airflow to make the titanium powder react with carbon black. The reaction temperature and holding time depend on the type of raw material, particle size, reaction performance, and other factors determined, especially the titanium powder obtained by decomposition of titanium hydride, with vigorous activity. It is easy to get titanium carbide close to the theoretical carbon content (20.05%) by keeping it at 1500°C for 1 hour.

(2) Self-propagating high-temperature synthesis (SHS)

The self-propagating high-temperature synthesis process is a new material preparation process that uses the immense heat released by the solid-phase reaction to maintain the response's spontaneous and continuous progress, thereby turning the reactants into products. The use of the SHS method to synthesize refractory compound powder is a relatively mature technology, so it has been widely used in the synthesis of TiC, and there are many research reports on this aspect. Compared with the traditional carbonization method, the production efficiency of TiC synthesized by SHS is increased by 1.5 to 3 times, which is suitable for mass production and can obtain higher product purity.

(3)Carbothermal reduction method of TiO2

Usually, TiO2 is used as raw material, carbon black is used as a reducing agent, and TiC is synthesized through mechanical mixing and reaction under a high-temperature vacuum or argon atmosphere. The reaction can also be carried out under a hydrogen atmosphere, but at this time, the reaction temperature must be as high as 2250°C. The composition of the TiC powder can be controlled by adjusting the reaction time and temperature. Recently, Rasit et al. used TiO2 powder as the raw material, deposited C on the TiO2 powder by decomposing propylene. Then argon gas was passed through the tube furnace at 1550℃ for carbonization and reduction for 4 hours to obtain high-purity, sub-micron loose TiC. Powder.

(4) Chemical vapor deposition method

Use gaseous TiCl4 and CH4 (or other hydrocarbons) to react at a temperature of 800 to 1200 ℃ to precipitate solid TiC. This method is often used to deposit TiC films on metal surfaces to enhance their hardness and wear resistance. To strengthen the reaction, H2 is usually introduced into the system. This method can produce ultrafine TiC powder. Recently, Borsella E. et al. used a CO2 laser beam to irradiate a mixture of TiCl4 and hydrocarbons to synthesize TiC powder and prepare it by adding SiH4. SiC/TiC composite powder is added.

(5) Microwave carbothermic reduction method

Under airtight conditions, the process of microwave heating is used to synthesize titanium carbide powder. The pressure of CO gas generated during the reaction has a significant influence on the synthesis temperature. The higher the CO gas pressure, the higher the synthesis temperature and the lower the synthesis rate. Conversely, the lower the CO gas pressure, the lower the synthesis temperature, and the higher the synthesis rate. During the synthesis process, if the reaction's CO gas can be discharged in time, the nano-level TiC powder with a high synthesis rate, refined crystal grains, and light accumulation can be synthesized at lower temperatures.

(6) Synthesis method in the molten metal bath

Utilizing the low solubility of TiC in iron group metals, titanium, and carbon dissolved in the molten metal can react to form TiC and precipitate from the molten metal. The reaction is carried out in an electric vacuum furnace above 2000 ℃; Cliche .G uses this method to directly synthesize TiC with high purity and low nitrogen and oxygen content in liquid metal iron or nickel.

(7) Mechanical alloying method

The mechanical alloying process is a method of alloying materials through stable state reaction through high-energy ball milling. Since the American Nickel Company invented the technique in 1969, its application research has been extensively carried out. In recent years, there are many research reports on the preparation of TiC by mechanical alloying. The process is characterized by elemental Ti powder or TiO2 powder and graphite powder as raw materials. The high-energy ball mill's steel balls produce a strong impact, stirring and mixing on the mixed powder. The crushing effect makes the raw material powder reach the atomic level tightly, and then the appropriate heat treatment can synthesize TiC powder. This method can significantly reduce the reaction temperature, but it must be carried out in a vacuum or a controlled atmosphere.

(8) Mechanically induced self-propagating reaction (MSR)

Mechanically induced self-propagating reaction (MSR) or mechanical alloying method for combustion synthesis, the reaction process is generally divided into three stages; the first stage is the incubation period, which is the formation of Ti/C composite particles; the second stage is the MSR reaction stage, Like the crystal size of the first stage decreases and the contact area of ​​the reactants increases, the temperature at which the reactants undergo MSR reaction decreases, and the adiabatic reaction temperature of Ti and C is very high. Once the response is initiated, it can follow the SHS mode immediately. Violent reaction, the ball milling machine energy, causes the temperature of the whole powder surroundings. The collision temperature between the balls increases and the sum of the MSR reaction's ignition temperature is greater than the MSR reaction's ignition temperature. The reaction occurs: the third stage, the grain continues to be accepted as the ball mill progresses.

Trunnano is one of the world's largest producers of titanium carbide powder. If you have any questions or needs, please contact Dr. Leo by email: brad@ihpa.net.

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