Preparing Tungsten Trioxide Nanoparticles Using Gas Phase Synthesis

Tungsten trioxide (WO₃) is an important n-type semiconductor oxide with a variety of crystal structures. It has been extensively studied due to its unique physical and chemical properties, and has been used in electrochromism, photochromism, catalysts, and sensing materials. In order to further utilize the excellent properties of WO₃ and broaden its application fields, one technical approach is to reduce its grain size, namely nanostructured tungsten oxide.

Gas phase synthesis is one of the most effective methods for preparing nanostructures. Various forms of solids can be precipitated by vapor deposition technique. The precipitates are in the form of thin films, whiskers and particles, and the vapor deposition method does not require high concentration of the reactants, and the purity of the product is high. However, with conventional vapor deposition, the yield of the product is very limited, and continuous production cannot be achieved due to the collection of the product under high vacuum or high temperature. APT·xH₂O was used as raw material, high temperature calcination combined with vapor deposition synthesis, argon gas as carrier gas, and the tungsten trioxide nanopowder is collected in low temperature zone. The continuous preparation of various morphologies of tungsten trioxide nanoparticles is achievable.

The method includes the following steps:

Step 1, a quartz glass tube with an air inlet and an air outlet is taken, and a carbon cloth is placed around the inner wall of the quartz glass tube near the air outlet end, then the quartz glass tube with the carbon cloth is placed horizontally in the tube furnace.

Step 2, the tube furnace is preheated to a specified temperature.

In step 3, the ceramic crucible containing ammonium paratungstate (APT) is pushed into the above glass tube to be heated to a constant temperature zone of a specified temperature, and argon gas is blown.

Step 4, maintain the temperature for 40 minutes to 60 minutes, the tube furnace is closed and the argon gas is stopped.

Step 5, the carbon cloth is removed, and the reaction product deposited thereon is collected to obtain multi-morphological tungsten trioxide nanoparticles, and the ceramic crucible is moved out.

Step 6, repeat steps 1-5 for several times: re-place the carbon cloth around the inner wall of the glass tube, move the sputum containing ammonium paratungstate to the constant temperature zone, reopen the argon gas, and start the next reaction to achieve continuous production.

This method combines the high-temperature calcination and vapor deposition, using argon as carrier gas and collecting carbon powder in low temperature region, can continuously produce various forms of tungsten trioxide nanoparticles, and solve the problem of low yield in traditional methods for preparing nanostructured tungsten trioxide. The process has simple and easy operation, low production cost, and has great application prospects.

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