Tungsten trioxide is light yellow orthorhombic crystal powder. It is mainly used for making high melting point alloys and hard alloys, making tungsten wires and fireproof materials, etc.
Tungsten trioxide is mainly prepared through the following six methods in factories or laboratories. Hydrothermal synthesis method, precipitation method, sol-gel method, microemulsion method, gas-liquid reaction method, and template method, etc.
Below, Jinbangch will introduce these six preparation methods in detail, including the advantages and disadvantages of their preparation process, etc.
1. Hydrothermal synthesis method
The hydrothermal method refers to using an aqueous solution as the reaction system in a special autoclave and forming a relatively high-temperature and high-pressure reaction environment by heating and pressurizing the reaction system. This is an effective method for inorganic synthesis and material processing by dissolving and recrystallizing normally insoluble or insoluble substances. For example, use HCl to acidify the Na2WO4 solution, and conduct a hydrothermal reaction at 130-200°C for 1-5 days, and finally tungsten trioxide with uniform particle size distribution can be obtained.
Metals or their precursors can be directly synthesized, avoiding the step of calcination and conversion into oxides in general liquid phase synthesis. Therefore, the formation of hard agglomerates is greatly reduced or even avoided, and the prepared powder has the advantages of complete grain development, small particle size, uniform distribution, and good dispersibility. And it can effectively control the particle size, particle size distribution, and shape of the powder.
2. Precipitation method
The precipitation method is usually to mix substances with different chemical compositions in a solution state. The basic principle is to add an appropriate precipitant to the salt solution to obtain a precursor precipitate, and the precipitate is dried and burned to form a nanopowder.
It is mainly divided into the co-precipitation method and the chemical precipitation method.
For example. Using the sol-co-precipitation method, using the mixture of WC16 and TiCl4 as raw materials, adding ammonia and surfactant to form W(OH)6 and Ti(OH)4, centrifuging and calcining to obtain 3~9nm tungsten trioxide. Using the chemical precipitation method, (NH4)10W12O41•5H2O is used as raw material to prepare H2WO4, and then dehydrated and calcined to obtain tungsten trioxide ceramic powder with a more uniform particle size.
The crystallization of the obtained powder tends to be complete, the particle size distribution is uniform, and the particle size is small.
The prepared powder is prone to agglomeration, which is not conducive to detection.
3. Sol-gel method
The sol-gel method is a method in which a metal-organic compound, a metal-inorganic compound, or a mixture of the two is solidified through a solution, sol, or gel, and then undergoes a heat treatment process to form oxides or other compounds. For example, using Na2WO4 as raw material, adding hydrochloric acid to make a sol, and then adding cetyltrimethylammonium bromide (CTAB) surfactant to obtain aggregates, drying, and calcining. Finally, tungsten trioxide powder with a particle size of 31-45nm is obtained.
The obtained powder has a small particle size, good uniformity, and high purity, and is easy to carry out industrial production.
It is difficult to control the sol-gel transition, the product is easy to form hard agglomerates after drying, and the synthesis cycle is often long.
4. Microemulsion method
The microemulsion method is a new method developed in recent years to prepare microsols, which are often composed of surfactants, co-surfactants, solvents and water (or aqueous solutions). In this system, two immiscible continuous media are divided into tiny spaces by surfactant amphiphile molecules to form microreactors. The reactants react in the system to form solid phase particles, and the size of the microemulsion particles can be controlled from several to tens of nanometers. For example, stir n-butanol, CTAB, and cyclohexane. Add Na2WO4 aqueous solution, and get microemulsion after stirring. Under the condition of ultrasonic oscillation, after adding the microemulsion solubilized with hydrochloric acid, centrifuge and separate a small amount of white colloidal precipitate after aging for several hours, and then wash the precipitate with an appropriate amount of absolute ethanol/acetone mixture and distilled water in sequence . The precipitate was dried at 105°C and ground into a white powder. Spherical particles with an average particle size of 40-65nm after calcination.
The obtained powder does not need to be heated, the experimental device is simple, the operation is convenient, and the product components and particle sizes are controllable.
High cost with slight agglomeration.
5. Gas-liquid reaction method
The gas-liquid reaction method refers to a method in which a gas is introduced into a salt solution to obtain a precursor precipitate, and the precipitate is dried to form an ultrafine powder. For example, take Na2WO4 as raw material, add ethanol/distilled water and stir to dissolve. The suspension generated by passing HCl gas was left to stand, centrifuged, washed, dried and then ground to obtain tungsten trioxide powder with uniform particle size distribution, good dispersibility and irregular shape, with an average particle size below 100nm.
The safety performance is better, and the obtained powder is smaller in size and better in dispersibility.
The process is complicated and takes a long time.
6. Template method
The template method usually uses a porous material with a pore size of nanometers as a template, combined with technologies such as electrochemical removal, precipitation, sol-gel and vapor precipitation. The material atoms or ions are deposited on the pore wall of the template to form the desired nanostructure, and then the template is removed to obtain a nanomaterial with the template’s standard shape and size.
For example, feed nitrogen into the Na2WO4 solution, stir and add HCl, and redissolve the washed precipitate with oxalic acid solution to obtain tungsten trioxide sol. Immerse the AAO template in it for a period of time, take it out and wash it, calcinate and cool it, and obtain highly ordered nanotube-shaped tungsten trioxide powder.
The method is simple, the repetition rate is high, the predictability is good, the product shape is uniform and the performance is stable.
Templates are more expensive.
In the end
The above are the six methods for preparing tungsten trioxide. Each method has its advantages and disadvantages. It is recommended to choose an appropriate method during preparation. Now, Jinbangch provides high-quality tungsten trioxide, which is superior to other brands in terms of purity, quality, and price. If you need a large amount of tungsten trioxide, welcome to contact us. Of course, you can get free samples of tungsten trioxide.