What are the main processes for preparing tungsten particles

As an important functional material, tungsten particles are widely used in electronics, military industry, nuclear industry and composite materials. The preparation process directly affects the particle size, morphology, purity and performance of tungsten particles, and thus determines their application effect. The current preparation process of tungsten particles mainly includes a variety of technical routes such as mechanical crushing, chemical reduction, vapor deposition and electrolytic deposition.

Mechanical crushing method

The mechanical crushing method is the most traditional and widely used method for preparing tungsten particles. This process uses high-energy ball milling equipment to physically crush large pieces of tungsten materials to obtain fine tungsten particles. The mechanical crushing method has the advantages of simple process, easy equipment and low cost. The particle size and morphology of tungsten particles can be controlled by adjusting the grinding time, grinding media and rotation speed. Tungsten particles prepared by mechanical crushing often have irregular shapes and a wide particle size distribution, which is suitable for occasions where the particle morphology is not required. However, this method is easy to introduce impurities and cause particle agglomeration, and requires subsequent classification and surface treatment.

Chemical reduction method

The chemical reduction method uses a tungsten-containing precursor (such as tungstate solution) under the action of a reducing agent to generate tungsten particles. This method can accurately control the particle size and morphology of the particles, and the prepared tungsten particles have high purity and uniform particle size distribution. Commonly used reducing agents include hydrogen, ammonia and carbon, and reaction conditions such as temperature, atmosphere and reduction time have a significant effect on particle performance. Tungsten particles prepared by chemical reduction are mostly spherical and suitable for use in catalysts, electronic packaging materials and other fields. The disadvantages of this process are that the reaction conditions are relatively harsh, the equipment requirements are high, and the production efficiency is relatively low.

Vapor deposition method

Vapor deposition method is a method for preparing tungsten nanoparticles with high precision, mainly including chemical vapor deposition (CVD) and physical vapor deposition (PVD). During the CVD process, the tungsten precursor gas decomposes at high temperature, and tungsten atoms are deposited on the surface of the substrate to form particles. This method can control the particle size and morphology of the particles, and the obtained tungsten particles are of high purity and good crystallinity. PVD deposits the atoms of the tungsten target into particles by evaporation or sputtering. The particle size of tungsten particles prepared by vapor deposition method has a wide range, which can be adjusted from nanometers to micrometers, and is suitable for the preparation of high-performance tungsten films and powder materials. The equipment of the vapor deposition method is complex and the cost is high, which is suitable for high-end application fields.

Electrolytic deposition method

The electrolytic deposition method uses the principle of electrochemistry to deposit tungsten particles on the cathode surface through tungsten ions in the electrolytic solution. This method can accurately adjust the particle size and morphology, and the reaction process is environmentally friendly, which is suitable for the preparation of ultrafine tungsten particles. The electrolytic deposition method is highly sensitive to parameters such as solution composition, current density and temperature. By optimizing the process parameters, uniform and well-dispersed tungsten particles can be prepared. This method has a long preparation cycle and has certain difficulties in large-scale production.

Spray drying method

The spray drying method is to atomize the tungsten-containing solution or suspension into tiny droplets, and quickly evaporate the solvent through hot air to form dry tungsten particles. This process is suitable for the preparation of spherical and well-dispersed tungsten powders, and the particle size distribution is uniform. The spray drying method combined with chemical reduction or sol-gel technology can prepare nano-scale tungsten particles, which are widely used in the field of functional materials. The process equipment is simple and the production efficiency is high, but it has high requirements for solution stability and process control.