Views:16 Author:Site Editor Publish Time: 2018-12-26 Origin:Site
The powder particle size and uniformity of tungsten powder and copper powder will affect the sintering effect of tungsten-copper alloy electrode to a certain extent. The reduction of powder particle size will make the comprehensive properties of materials such as density, hardness and electrical and thermal conductivity extremely great. Improvement. In the traditional powder metallurgy method (Powder Metallurgy, PM), the composite material obtained by the press sintering process using metal powder (or metal oxide powder) as a raw material has a coarse powder particle size. In contrast, the nano-tungsten copper material has a high surface energy. During the sintering process, the movement of the atom is driven by a high interfacial energy, so that some tiny pores in the interface are further shrunk to prevent the diffusion of the pores. Therefore, research on nano-tungsten-copper alloys is beneficial to achieve sintering densification at lower temperatures.
Although the preparation process of nano-tungsten-copper alloy generally looks similar to the traditional powder metallurgy process, it is divided into three processes: milling preparation-press molding-sintering, but the specificity of nanoparticles also makes nano-tungsten-copper alloy. There is a certain difference between the preparation and the traditional method. In general, the preparation methods of nano-tungsten-copper alloys, which are more common and widely used, are Sol-Gel, Metal Alloying (MA), mechanical-thermochemical synthesis and fog. Drying, etc.
Metal Alloying (MA) is a high-energy ball mill that mills a certain proportion of tungsten-copper mixed powder for a longer period of time to obtain a nano-powder with a particle size close to 20 nm-30 nm. The prepared nano powder is pressed into the green body and sintered in a hydrogen atmosphere for a period of time to obtain a nano tungsten copper alloy having a relatively high relative density.
The so-called sol-gel method (Sol-Gel) uses a compound containing a high chemical component as a precursor, and uniformly mixes, hydrolyzes, and condenses these materials in a liquid phase to form a stable transparent sol system in a solution. The sol slowly polymerizes between the aged rubber particles to form a gel of a three-dimensional network structure, and the gel network is filled with a solvent that loses fluidity to form a gel. The gel is dried and sintered to prepare a material of molecular or nano-substructure. In the current academic field, researchers have successfully prepared high-performance molybdenum-copper and tungsten-copper powders by this method, but this method also has certain defects, such as difficulty in controlling impurities and water vapor during hydrogen reduction. The content, and the existence of these problems will have a certain impact on the subsequent sintering process.