Molybdenum?powder prepared by traditional technology is often used to be raw material of molybdenum sintered products, the common preparation methods include reduction method, fluidized bed reduction method, hydroxyl thermal decomposition method etc.
1.0 Reduction method
1.1 Ammonium molybdate roasting→two-stage reduction. This method is the main method used in industrial production, the purity of Mo powder produced is high, the particle size is usually in micron level.
1.2 Ammonium molybdate two-stage reduction method. Without calcination, ammonium molybdate is directly reduced once (500℃~ 650℃) to generate mo2, after it is screened and then reduced twice (900℃~ 1100℃) to get Mo powder.
1.3 Ammonium molybdate single reduction method.?Mo?powder is produced by one-step reduction?using ammonium molybdate as raw material, due to high temperature and high partial pressure of water vapor, the particle size of Mo?powder grows up, and molybdenum powder with particle size of about 5μM is obtained. 2μm~4.2μm Mo?powder can be obtained by adding different size and proportion of Mo?powder into ammonium molybdate.
1.4 Molybdenum oxide hydrogen reduction method. Mo3 one-stage reduction method?is simple, but the process is difficult to control, the particle size of Mo?powder is coarse and the quality is poor, if?the sintered product is?prepared using this type of?Mo?powder as raw material, the sintered billet is not dense enough and the elongation is not good, so it can not be used to prepare molybdenum wire etc.
2.0 Fluidized bed reduction method
In the fluidized bed, the gas-solid contact is sufficient, the temperature in the bed is quite uniform, so the reaction speed is fast, the particle size and morphology of the product can be well controlled. The Mo powder produced by this method is equiaxed and has good fluidity, which is good to subsequent sintering products.
3.0 Hydroxyl thermal decomposition method
Mo powder with particle size of 2μm~4μm?can be prepared by steam pyrolysis of hydroxyl molybdenum in hydrogen atmosphere at 350℃~1000℃. 60%~70% of the Mo powder is spherical powder with unsmooth surface and convex points, and contains 3.4%~3.9% carbon and 5.8% oxygen. Decarburization is carried out in wet hydrogen atmosphere, and then deoxidation is made with pure and dry hydrogen at 1100℃.
