Preparation method of nano-tungsten powder

A nano-tungsten powder and powder technology, applied in the preparation of nano-tungsten metal powder, based on the nitride conversion method to prepare nano-scale ultra-fine tungsten powder, can solve the problem of reducing the melting point and high-temperature mechanical properties of tungsten products, and cannot prepare large-scale products , not suitable for industrial production and other problems, to achieve the effect of cheap raw materials, good sintering activity, and small particle size of powder

Inactive Publication Date: 2011-04-20
SHANGHAI INST OF CERAMIC CHEM & TECH CHINESE ACAD OF SCI
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  • Abstract
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  • Claims
  • Application Information

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Problems solved by technology

However, the above-mentioned methods have their own disadvantages. The molding equipment of the ultra-high pressure molding method is complicated, the cost is high, and large-sized products cannot be prepared, and the risk is high, so it is not suitable for industrial production.
Adding an activator is easy to form a brittle phase, which destroys the purity of tungsten and reduces the melting point and high-temperature mechanical properties of tungsten products.
The third method is to process micron-sized tungsten powder into nano-sized, and use the high lattice distortion of nano-sized powder to increase the sintering driving force, thereby increasing the density of the material. Avoid introducing impurities
In addition, gas-phase reduction of tungsten oxide (WO 3 ) is also a common method for preparing nano-tungsten powder, however, due to hydrogen reduction of tungsten oxide will generate WO 2 (OH) 2 (g) Mesophase, which reduces the reaction rate and leads to the growth of W particles

Method used

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Examples

Experimental program
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Effect test

Embodiment 1

[0030] Weigh 10mmol of ammonium metatungstate and 50mmol of citric acid, dissolve them in 100ml of deionized water to obtain a clear mixed solution; perform complexation reaction in a water bath at 70°C for 5 hours; filter and dry at 120°C for 12 hours to obtain a tungsten oxide precursor body; calcined at 650°C for 3 hours in an air atmosphere to obtain WO 3 Powder.

[0031] will get WO 3 The powder is placed in a tube furnace, nitrogenated with ammonia gas, the flow rate of ammonia gas is controlled at 3L / min, the temperature is 700°C, the heating rate is 2°C / min, and the temperature is kept for 2 hours to obtain W 2 N powder.

[0032] will get W 2 Place the N powder in a graphite crucible, heat it to 900°C in a carbon tube furnace under the condition that the air pressure is lower than 200Pa and keep it warm for 1 hour to obtain nano-tungsten powder with an average particle size of 20nm.

Embodiment 2

[0034] The only difference between this embodiment and embodiment 1 is: the obtained W 2 The N powder is directly placed in a tube furnace, and then reduced by passing hydrogen gas. The flow rate of hydrogen gas is 150ml / min, the heat treatment temperature is 850°C, and the time is 2 hours, and the nano-tungsten powder is obtained.

[0035] The rest of the content is exactly the same as described in Example 1.

[0036] It is known through detection and analysis that the average particle size of the nano-tungsten powder prepared in this embodiment is 40nm.

Embodiment 3

[0038] The only difference between this embodiment and embodiment 1 is: the obtained W 2 N powder is placed in a graphite crucible, and nitrogen gas is introduced into a carbon tube furnace, and the reactant is heated to 900°C and kept for 3 hours to obtain nano-tungsten powder.

[0039] The rest of the content is exactly the same as described in Example 1.

[0040] It is known through detection and analysis that the average particle size of the nano-tungsten powder prepared in this embodiment is 30nm.

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Abstract

The invention discloses a preparation method of nano-tungsten powder. The preparation method comprises the following steps: preparing ammonium metatungstate and citric acid into clear mixed aqueous solution; performing complex reaction at the temperature of 60 to 90 DEG C; filtering and drying to obtain the precursor of tungsten oxide; calcining in air to obtain tungsten oxide (WO3) powder; introducing ammonia gas to the tungsten oxide powder for nitridation to obtain tungsten nitride (W2N) powder; and finally performing thermal treatment on the tungsten nitride powder to obtain the nano-tungsten powder. The preparation process disclosed by the invention is simple and practical and has the high operability and is easy in implementation of scale production; the prepared powder has small particle size of which the average particle size is 20-50 nm; the particle size distribution is uniform; and the degree of aggregation is low and high sintering activity is realized. The technology disclosed by the invention can promote the progress of high-quality tungsten material in China and the performance level, and provide means for transforming advantages in tungsten ore resources into industrial and economical advantages.

Description

technical field [0001] The invention relates to a method for preparing nano-tungsten metal powder, in particular to a method for preparing nano-scale ultrafine tungsten powder based on a nitride conversion method, and belongs to the technical field of nano-powder preparation. Background technique [0002] Tungsten has excellent physical and chemical properties such as high melting point, low vapor pressure, high hardness, high specific gravity, small thermal expansion coefficient, and good corrosion resistance. in X-ray technology. Tungsten is the best material for incandescent filaments and spiral filaments. The high working temperature (2200-2500°C) can ensure high luminous efficiency, and the small evaporation rate can ensure the long life of the filaments. The annual domestic demand for lighting filaments is as high as 450 tons. . Tungsten wire can be used to manufacture direct-heated cathodes and grids of electronic oscillating tubes, cathodes of high-voltage rectifie...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B22F9/20C22B34/36
Inventor 阚艳梅孙世宽张国军
Owner SHANGHAI INST OF CERAMIC CHEM & TECH CHINESE ACAD OF SCI
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