Restoration method:

The reduction method of metal oxides and salts is one of the most widely used powder preparation methods. Solid carbon can be used to reduce iron powder and tungsten powder, and tungsten, molybdenum, iron, copper, cobalt, nickel and other powders can be produced by hydrogen or ammonia decomposition; By converting natural gas and coal gas, iron powder can be produced, while rare metal powders such as tantalum, niobium, titanium, zirconium, thorium, and uranium can be produced using metals such as sodium, calcium, and magnesium as reducing agents. The basic principle of the reduction method of metal oxides and salts is that the affinity of the reducing agent used for oxygen is greater than that of the corresponding metal in the oxide and salt used, so it can take away the oxygen in the metal oxide or salt and reduce the metal. Due to the varying effects of different metal elements on oxygen, the stability of oxide formation also varies. The stability of oxides can be characterized by the magnitude of Δ G during the oxidation reaction process. The smaller the Δ G value during the reaction process, the higher the stability of its oxide, that is, the greater its affinity for oxygen.

Its advantages are simple operation, easy control of process parameters, high production efficiency, low cost, and suitable for industrial production; The disadvantage is that it is only suitable for metal materials that are prone to react with hydrogen and become brittle and brittle after hydrogen absorption.

Metal thermal reduction and reduction methods:

Metal thermal reduction is a process where the raw material being reduced can be solid, gaseous, or molten salt. The latter two have corresponding characteristics of gas-phase reduction and liquid-phase precipitation. The commonly used metal thermal reducing agent method in industry includes reducing TiO2, ThO2, UO2, etc. with calcium; Reduce TiCl4, ZrCl4, TaCl5, etc. with magnesium; Reduce TiCl4, ZrCl4, K2ZrF6, K2TaF7, etc. with sodium; Preparation of nickel chromium stainless steel powder by co reduction of chromium oxide and nickel oxide with calcium hydride (CaH2).

Reduction method refers to the use of carbon, boron carbide, silicon, nitrogen, and refractory metal oxides to obtain carbides and borides. The method of nitrides.

Electrolysis method:

Electrolysis is a method of depositing and precipitating metal powder at the cathode by electrolyzing molten salt or an aqueous solution of salt. Almost all metal powders can be produced by electrolysis, and copper powder, silver powder, and tin powder are particularly suitable for production. Electrolytic powder production can be divided into aqueous solution electrolysis, organic electrolyte electrolysis, molten salt electrolysis, and liquid metal cathode electrolysis.

Its advantage is that the metal powder produced has a high purity, and the purity of general elemental powder can reach over 99.7%; In addition, electrolysis can effectively control the particle size of powders and produce ultrafine powders. However, electrolytic powder production consumes a large amount of electricity and incurs high milling costs. Electrolytic aqueous solutions can produce metal (alloy) powders such as Cu, Ni, Fe, Ag, Sn, Fe Ni, etc. Electrolytic molten salts can produce metal powders such as Zr, Ta, Ti, Nb, etc.

Hydroxyl method:

Synthesize certain metals (iron, nickel, etc.) with carbon monoxide to form metal carbonyl compounds, which are then reheated and decomposed into metal powder and carbon monoxide. The powder produced in this way is very fine and of high purity, but the cost is high. It is mainly used in industry to produce fine and ultrafine powders of nickel and iron, as well as alloy powders such as Fe Ni, Fe Co, Ni Co, etc.

Chemical displacement method:

Chemical displacement method is based on the activity of metals, using highly active metals to displace less active metals from metal salt solutions, and further processing and refining the resulting metal (metal powder particles) using other methods. This method is mainly applied to the preparation of inert metal powders such as Cu, Ag, Au, etc.