A preparation method of chromium nitride

abstract

The present invention relates to a preparation method of chromium nitride. The method is as follows: 95-99% chromium metal powder, 0.5-3% montmorillonite and 0.5-3% water are mixed according to the mass percentage and then pelletized. The diameter of the ball is 1-2cm, and the pelletizing time is 20-30min. The gas is introduced into the ball, and the pressure and temperature are controlled. After cooling, the material is at room temperature to obtain chromium nitride. The advantages of this technology are as follows: 1) the whole preparation method is simple and easy to operate; 2) In the technical scheme, the process of balling first and then reaction is adopted. The purpose of balling is to increase the contact area between chromium powder and gas, accelerate the reaction speed and make the reaction sufficient; 3) In this technical scheme, montmorillonite is selected as the binder for chromium powder pelleting. Montmorillonite is an inorganic polymer thickener, which plays a skeleton role, so that the metal chromium powder dispersed in montmorillonite in each ball can fully contact and react with nitrogen or ammonia or their mixture, improve the conversion rate, shorten the reaction time and reduce the cost.

1. A method for preparing chromium nitride, which is characterized in that the method is as follows: 95-99% chromium metal powder, 0.5-3% montmorillonite and 0.5-3% water are mixed according to the mass percentage, and then pelletized. The diameter of the ball is 1-2cm, and the pelletizing time is 20-30min. The gas is introduced, heated, and the pressure and temperature are controlled. After cooling, the material is at room temperature to obtain chromium nitride.

2. The method for preparing chromium nitride according to claim 1, wherein the gas introduced is nitrogen or ammonia or a mixture thereof.

3. The method for preparing chromium nitride according to claim 2, wherein after the gas is introduced

The reaction temperature is set at 800-1000 ℃, and the reaction time is 1-2 hours.

4. The method for preparing chromium nitride according to claim 3, wherein the heating method is microwave heating.

5. The method for preparing chromium nitride according to claim 4, characterized in that after the reaction is completed, the product is cooled to 200 ℃ in the gas, taken out, cooled to room temperature, 16-18 ℃ in winter and 24-26 ℃ in summer to obtain chromium nitride.

6. The method for preparing chromium nitride according to claim 5, wherein

98% chromium metal powder, 1% montmorillonite and 1% water were mixed and pelletized.



Background technology

[0002] chromium nitride has many excellent characteristics, such as high hardness, high melting point, low friction coefficient and good conductivity. Because of its super hardness, good corrosion resistance and oxidation resistance, chromium nitride is often used as protective coating and superhard material. It is widely used in various fields of industry, such as aviation, petroleum, chemical industry, machinery, textile, high-temperature ceramics, automobile, metallurgy, electronic industry and so on.

[0003] in the prior art, the preparation methods of chromium nitride mainly include: high-energy ball milling method, benzene heating method, high-temperature self propagating method, arc discharge plasma method, ammonolysis method, microwave-assisted method, etc. After preliminary search, the patent 103318855a uses metal chromium powder in the atmosphere of oxygen and nitrogen, the synthesis temperature is 800-1200 ℃, the temperature is kept for 2-20h, and the temperature is cooled to room temperature to obtain chromium nitride. The invention directly reacts with 200 mesh chromium powder. After the chromium powder is precipitated in the chamber, the nitrogen does not completely contact with the chromium powder at the bottom, reducing the conversion rate. In addition, in the oxygen atmosphere, part of the chromium powder reacts with oxygen to produce chromium oxide, which reduces the purity of the product. Therefore, there is an urgent need for a new technical solution to solve the above technical problems.







summary of the invention

[0004] the present invention aims at the technical problems existing in the prior art, and provides a preparation method of chromium nitride. The technical scheme has high conversion rate, improves production efficiency, and greatly reduces production costs of enterprises.

[0005] in order to achieve the above objectives, the technical scheme of the present invention is as follows: a method for preparing chromium nitride is characterized in that the method is as follows: 95-99% chromium metal powder, 0.5-3% montmorillonite and 0.5-3% water are mixed according to the mass percentage, and then pelletized. The diameter of the ball is 1-2cm, and the pelletizing time is 20-30min. The gas is introduced, and the pressure and temperature are controlled. After cooling, the material is brought to room temperature to obtain chromium nitride. The technical scheme firstly involves pelletizing. The purpose of pelletizing is to increase the contact area between chromium powder and gas, accelerate the reaction speed and make the reaction full. Secondly, the materials can be fully reacted, with high conversion rate, increased output and reduced enterprise cost. In this technical scheme, montmorillonite is selected as the binder for chromium powder pelleting. Montmorillonite is an inorganic polymer thickener, which generally has a three-layer layered structure or an expanded lattice structure, so that montmorillonite not only plays a bonding role, but also plays a skeleton role, so that the metal chromium powder dispersed in montmorillonite in each ball can fully contact and react with nitrogen or ammonia or their mixture to improve the conversion rate, Shorten reaction time and reduce cost.

[0006] as an improvement of the present invention, the gas introduced is nitrogen or ammonia or a mixture of the two. The addition of nitrogen or ammonia or mixed gas can be used as a nitrogen source for nitriding reaction, and can also improve the reaction atmosphere and reduce the oxidation loss of metal chromium powder.

[0007] as an improvement of the present invention, after the gas is introduced, the pressure is set to 2-5atm, and the reaction temperature is set to

800-1000 ℃, and the reaction time is 1-2 hours. The reaction is carried out in an atmosphere of 2-5atm. Increasing the pressure of the reaction gas is conducive to the passage of nitrogen or ammonia or their mixture through the micropores in the ball and into the center of the ball, so that the reaction is more complete. In the whole reaction system, there are many factors conducive to the reaction. For example, the reactants are porous pellets, and the reaction is conducted in a positive pressure atmosphere. Therefore, the time and temperature of the reaction process are reduced accordingly, which will reduce the manufacturing cost and improve the manufacturing efficiency.

[0008] as an improvement of the present invention, the heating method is microwave heating. The material can be heated evenly, the temperature control is accurate, the heating speed is fast, and the environment is clean.

[0009] as an improvement of the present invention, after the reaction is completed, it is cooled to 200 ℃ in the gas, the product is taken out, cooled to room temperature, 16-18 ℃ in winter and 24-26 ℃ in summer to obtain chromium nitride

As an improvement of the present invention, the preferred embodiment of the technical scheme is to mix 98% chromium metal powder, 1% montmorillonite and 1% water according to the mass percentage and then make pellets.

[0010] compared with the prior art, the advantages of this technology are as follows: 1) the whole preparation method is simple and easy to operate; 2) In the technical scheme, the process of balling first and then reaction is adopted. The purpose of balling is to increase the contact area between chromium powder and gas, accelerate the reaction speed and make the reaction sufficient; 3) In this technical scheme, montmorillonite is selected as the binder for chromium powder pelleting. Montmorillonite is an inorganic polymer thickener, which generally has a three-layer layered structure or an expanded lattice structure, so that montmorillonite not only plays a bonding role, but also plays a skeleton role, so that the metal chromium powder dispersed in montmorillonite in each ball can fully contact and react with nitrogen or ammonia or their mixture to improve the conversion rate, Shorten reaction time and reduce cost; 4) The technical scheme has low cost and is convenient for large-scale promotion and application.

Specific implementation

[0011] in order to deepen the understanding and understanding of the present invention, the present invention will be further described and introduced in combination with specific embodiments.

[0012] example 1:

After mixing 1960g of metal chromium powder, 20g of montmorillonite and 20g of water, use a pelletizer to make balls. The diameter of the balls is 2cm and the pelletizing time is 30min. After the balls are made, put them into a graphite crucible. Put the graphite crucible into a heating furnace and carry out gas-solid reaction in a nitrogen atmosphere. Microwave heating is used to control the temperature at 800 ℃ for 2 hours, and nitrogen is continuously introduced. Control the nitrogen pressure in the furnace to 4atm. After the reaction is completed, it is cooled to 200. D egree. C. in a nitrogen stream, the product is taken out, and cooled to room temperature to obtain chromium nitride. Through XRD detection, only the characteristic peak spectrum of chromium nitride is found in the product, and no other impurity peak spectrum is found. The product has uniform particle size and oxygen content less than 1.38%.

[0013] example 2:

After mixing 1960g of metal chromium powder, 20g of montmorillonite and 20g of water, use a pelletizer to make a ball. The diameter of the ball is 1cm, and the pelletizing time is 20min. After the ball is made, put it into a graphite crucible. Put the graphite crucible into the heating furnace and conduct the gas-solid reaction in the ammonia atmosphere. Microwave heating is used to control the temperature at 1000 ℃ for 1.5 hours, and ammonia gas is continuously introduced. Control the ammonia pressure in the furnace to 2 ATM. After the reaction is completed, it is cooled to 200 ° C in the ammonia gas stream, the product is taken out, and cooled to room temperature to obtain chromium nitride. Through XRD detection, only the characteristic peak spectrum of chromium nitride is found in the product, and no other impurity peak spectrum is found. The product has uniform particle size and oxygen content less than 1.46%.

[0014] example 3:

After mixing 1960g of metal chromium powder, 20g of montmorillonite and 20g of water, use a pelletizer to make a ball. The diameter of the ball is 1.5cm, and the pelletizing time is 25min. After the ball is made, put it into a graphite crucible. Put the graphite crucible into the heating furnace and conduct the gas-solid reaction in the 1:1 mixed atmosphere of nitrogen and ammonia. Microwave heating is used to control the temperature at 900 ℃ for 2 hours, and a 1:1 mixture of nitrogen and ammonia is continuously introduced. Control the gas pressure in the furnace to 3 ATM. After the reaction is completed, it is cooled to 200 ° C in the mixed gas flow, the product is taken out, and cooled to room temperature to obtain chromium nitride. Through XRD detection, only the characteristic peak spectrum of chromium nitride is found in the product, and no other impurity peak spectrum is found. The product has uniform particle size and oxygen content less than 1.21%.