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Method for preparing nano-tungsten powder from calcium tungstate

A technology of nano-tungsten powder and calcium tungstate, applied in the field of powder metallurgy, can solve the problems of high contact resistance of nano-powder particles, slow solid-state reduction process, low product purity, etc., to alleviate resource crisis, uniform size and high purity. Effect

Active Publication Date: 2011-11-02
WUHAN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, due to the slow solid-state reduction process and the large contact resistance between nanopowder particles, it is difficult to completely restore the cathode raw materials in a short time, resulting in high energy consumption, low current efficiency, low product purity, and the presence of calcium tungstate and carbon. There are shortcomings such as interference of impurities, and impurities such as calcium tungstate are difficult to remove by simple methods such as washing with water

Method used

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  • Method for preparing nano-tungsten powder from calcium tungstate
  • Method for preparing nano-tungsten powder from calcium tungstate

Examples

Experimental program
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Effect test

Embodiment 1

[0026] Weigh 2g of calcium tungstate powder, press it into a thin slice with a diameter of 15mm under 6MPa, place the thin slice in an electric furnace for sintering, the heating program is 4K / min to 750°C, and then keep it warm for 2 hours. After natural cooling, take out the thin slice and wrap it with a tungsten wire. It is connected with a metal wire to make a cathode for electrolysis. Weigh 300g of calcium chloride and 150g of sodium chloride respectively into an alumina crucible, and place it in a closed reactor. The electric furnace is raised to 250°C at 4K / min, and after 48 hours of heat preservation, it is raised to 850°C at 4K / min under the protection of argon, kept at 20 minutes, and cooled to 750°C after the mixed salt is completely melted. Insert the graphite anode and the nickel sheet cathode into the molten salt and apply a voltage of 2.7-2.8V for pre-electrolysis for 4-8 hours to remove residual moisture and impurities in the molten salt. Then take out the nic...

Embodiment 2

[0029] Weigh 2g of dried calcium tungstate powder, wrap it with foamed nickel and connect it with a metal wire to make a cathode for electrolysis. 2 - After 12 hours of electrolysis at a constant voltage of 3.0-3.6V in NaCl mixed salt. Reduce the cell voltage to 2.5V, raise the temperature of the electric furnace to 900°C, and slowly take out the reaction electrode after holding for 10 minutes. After being completely cooled, put it into a 50ml beaker filled with deionized water and soak for 1 hour. After removing the nickel foam shell, the product is cleaned with deionized water and centrifuged until the supernatant cannot detect chloride ions with silver nitrate, and then the product Put it into a vacuum drying oven at 80°C for 2 hours to obtain nano-tungsten powder.

[0030]

Embodiment 3

[0032] Weigh 2g of calcium tungstate powder, press it into a sheet with a diameter of 15mm under 6MPa, wrap it with tungsten wire and connect it with the tungsten wire to make a cathode for electrolysis; use metal calcium or calcium alloy as the anode, CaCl 2 -NaCl mixed salt is used as the electrolyte, the temperature is controlled at 600-700°C, the two electrodes are first short-circuited for 1 hour, and then a voltage of 0.1-0.5V is applied between the two electrodes for 8 hours of constant voltage electrolysis. Afterwards, take out the anode and place it in a low-temperature zone, raise the temperature of the molten salt to 850°C, and slowly take out the reaction electrode after keeping the temperature for 20 minutes. Wash the product after it is completely cooled, and dry it in vacuum to obtain nano-tungsten powder with a carbon content of less than 0.005%.

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Abstract

The invention provides a method for preparing nano-tungsten powder from calcium tungstate. The method comprises the following steps: allowing the calcium tungstate to be closely contacted with conductive metal to form a cathode for electrolysis, taking a soluble or insoluble material as an anode matched with the cathode, and taking a mixture of CaCl<2> and other alkali metals or alkaline-earth metals as electrolyte; placing the electrolyte in a heatable sealed electrolytic cell for heating to remove moisture in the electrolyte, and then heating to reaction temperature for electrolysis under protection of inert atmosphere; heating the electrolyte after the reaction, soaking the cathode in molten salt under inert atmosphere, and washing so as to remove residual impurities; and taking out the obtained cathode product, soaking the product in deionized water so as to remove the surface residual electrolyte, and finally carrying out vacuum drying to obtain the nano-tungsten powder. By utilizing the method, defects such as poor quality of deposited tungsten powder, slow electrolytic speed at the later stage of the direct solid-state reduction process and the like in the existing molten salt electrolysis technology are overcome.

Description

technical field [0001] The invention belongs to the field of powder metallurgy and relates to a method for preparing nanometer tungsten powder from calcium tungstate. Background technique [0002] Tungsten is a rare metal with an ultra-high melting point, stable chemical properties, excellent wear resistance and heat resistance. It is widely used in metallurgy, machinery, military industry, aerospace and many other fields. The tungsten ore resources for mining on the earth include wolframite (Fe, Mn)WO 4 (30%) and scheelite CaWO 4 (70%) Two. In countries with more advanced mining technology, such as Canada and Russia, the mining ratio of black tungsten ore and scheelite is 40% to 60%; while in some areas with less developed technology, especially accounting for more than half of tungsten ore resources In China, due to the disadvantages of scheelite mining, such as difficulty in beneficiation and leaching, compared with wolframite, tungsten mining is mainly wolframite, wh...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C25C5/04
Inventor 汪的华汤丁丁朱华尹华意
Owner WUHAN UNIV
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