Views: 3 Author: Site Editor Publish Time: 2022-09-08 Origin: Site
Zirconium powder is an important product in zirconium series. Because of its excellent suction performance, it has been widely used in ammunition, fireworks, electric vacuum and other industries. Zirconium powder can be prepared by metal thermal reduction, hydrogenation and dehydrogenation and electrolysis. In production, the preparation method is often determined according to the user's requirements for product purity, impurity content, particle size and particle shape.
The methods of preparing zirconium powder commonly used in industry are metal thermal reduction, hydrogenation and dehydrogenation and electrolysis. The specific process is described as follows.
Thermal reduction of metals
Calcium reduction method
Zirconia powder prepared by calcium reduction of zirconia is made of ZrO2 as raw material, calcium chloride as auxiliary agent, and then with an appropriate amount of reducing agent -- pure calcium metal, and then mixed, sealed, vacuum filled with argon, and then reduced at the temperature of 1 000℃~1 100℃. The reactant is a mixture of zirconium powder, calcium chloride, calcium oxide and excess calcium, which can be obtained by leaching it with hydrochloric acid, washing, crushing, filtering, drying and screening. The zirconium powder obtained by this method does not contain hydrogen, but its particle size is relatively coarse.
Calcium hydride reduction
To make zirconium powder from zirconia reduced by calcium hydride, calcium must be hydrogenated, ground to powder, and then mixed with ZrO2. After mixing, the powder is reduced at 1 000℃ in a bomb sealed reactor. The reaction product is the mixture of zirconium powder containing a small amount of hydrogen, calcium oxide and a little excess calcium. The TOTAL CONTENT OF ZIRCONium PREPARED by the above two methods is close to 99%, and the content of chloride ion is less, especially the ZIRCONium powder prepared by calcium hydride reduction is more suitable for electric vacuum industry.
Sodium reduction method
The zirconium powder prepared by sodium reduction of potassium zirconium fluoride is made of K2ZrF6 as raw material, and then combined with an appropriate amount of potassium chloride and sodium chloride molten salt, and then reduced at about 860℃. After acid leaching, washing, grinding and drying of the reaction product, zirconium powder can be obtained. The advantages of reducing potassium zirconium fluoride with sodium are that the equipment is simple and easy to operate, and the sodium fluoride generated by the reaction is easy to be separated by washing. Moreover, because the zirconium powder precipitated by reduction is dispersed in molten salt, the oxidation is less, and the reduction process can be carried out in the open equipment.
Hydrogenation and dehydrogenation
Zirconium powder preparation by hydrogenation and dehydrogenation.
Art is simple, the product particle size is fine, and the ignition point is also higher than pure zirconium powder because of hydrogen, relatively safe. But instead of ZrO2,K2ZrF6 and other zirconium compounds, zirconium sponge or zirconium metal is used as raw materials in this method. In production, zirconium sponge is first broken into grains (metal is cut into debris), hydrogenated at 600℃~700℃, and then put into the furnace after grinding and drying, and dehydrogenation at 700℃ temperature, zirconium powder can be prepared.
Zirconium powder prepared by electrolytic potassium zirconium fluoride molten salt system is also a common production method.
Zirconium powder is widely used in industry. For example, zirconium powder obtained by hydrogenation and dehydrogenation can be used as inspirator, detonator and heating sheet and combustion agent of electric vacuum tube. The thermal battery is the heat source of the rocket missile control system. Zirconium powder reacts with barium chromate in the thermal battery to release heat, which quickly activates the battery and makes the device enter the working state quickly. It is reported that only in the 1980s, the United States developed thermal batteries using zirconium powder there are nearly 450 kinds, the annual output of more than 500,000, mostly used in the military industry, the annual amount of zirconium powder reached 50 T.
Zirconium powder prepared by reducing zirconia with calcium hydride is usually used in large vacuum tubes with good effect. Large tube is an important part of a radio, communication and radar facilities, the role of zirconium powder in large tube is to absorb the residual gas in pipe, in use process to keep the high vacuum degree, reduce the number of grid electronic thermal emission, and advantage of the characteristics of its high melting point, low vapor, keep the transparency of glass vacuum tube, is advantageous to the tube heat dissipation, It can keep the tube in normal working condition for a long time and solve the disadvantage of cathode poisoning of the tube.
Zirconium powder obtained by hydrogenation and dehydrogenation method contains a small amount of hydrogen, which can be used as an electric vacuum aspirator, a detonator and a combustion agent for a hot battery heating sheet.