Tungsten Oxide

Nano tungsten trioxide is a typical N-type semiconductor gas sensing material, it has a large surface area, stable chemical properties, a wide band gap, a variety of toxic gases have good sensitivity, can effectively improve gas sensor sensitivity and response speed, is a good gas-sensitive film material. The preparation and synthesis of nano tungsten trioxide thin film by gas phase method is mainly to convert the synthesized tungsten trioxide crystal into the state of gas phase of tungsten trioxide through steps of sublimation, evaporation and decomposition. By setting the experimental conditions, the tungsten trioxide is transformed into tungsten trioxide saturated vapor. Finally, as the temperature decreases, saturated steam will crystallize in cold to grow as nanostructured tungsten trioxide crystals. The preparation of nano tungsten trioxide gas-sensitive film gas method includes two kinds of chemical and physical methods. Chemical vapor deposition (CVD) principle is the use of g

Sol gel method is widely used abroad, a kind of nano material preparation method, its principle is the prepared precursor (such as inorganic salt or metal alkoxide) dissolved in small molecule solvent in solution by mixing made uniform, solute and solvent hydrolysis reaction, hydrolysis condensation the reaction of nano particles and the formation of integrated sol. On the basis of the prepared sol, different processes can be used to prepare nano thin films and ultrafine powders with different properties. There are several ways to prepare tungsten trioxide thin films by sol-gel method: 1. Tungstic acid hydrochloric acid method; 2. Tungsten powder peroxide polytungstic acid method; 3. Tungstic acid colloid solution is prepared by ion exchange; 4. Polymer method. The traditional sol-gel method mostly controls the particle size of powders by controlling pH value, temperature and adding surfactants. Recently, some scholars have successfully controlled the particle size of WO 3  powders by

Nano tungsten trioxide is an excellent N-type semiconductor gas sensor, compared with the traditional materials, nano-tungsten trioxide gas sensor, high sensitivity, faster response speed and faster recovery is the most studied in recent years gas sensitive raw materials. There are methods for the synthesis of nano tungsten oxide films or gas phase method and solid phase method, liquid phase method. Electrodeposition is a gas phase method for preparing nano tungsten trioxide thin film, it is in a certain electrolyte and operating conditions, the metal or alloy from the compound solution, non aqueous solution or molten salt electrochemical deposition. The basic process of electrodeposition in preparing WO 3  thin films is: first, dissolve the W powder in a certain proportion with H 2 O 2 , then remove the excess H 2 O 2 , get the electrolyte solution and deposit it naturally, then use Pt as the working electrode and the other as the counter electrode. The WO 3  thin film can be obtained

Synthetic nano tungsten trioxide or thin film methods are usually gas phase method, solid phase method, liquid phase method. Sputtering method is a preparation of nano tungsten trioxide film gas phase preparation method. The most widely used sputtering method is magnetron sputtering. Some foreign scholars use metal W as a target, and use a mixed gas of Ar and O 2  to prepare a WO 3  thin film which is more gas-sensitive to NO x  by magnetron sputtering. In addition, there are scholars using DC magnetron sputtering device, the target is 99.95% W, in a vacuum degree of 2 × 10-6mbar reaction chamber, Ar (50%) - O 2  (50%) the mixed gas is subjected to direct current radio frequency excitation and discharge to deposit the WO 3  thinly on the substrate to obtain a WO 3  thin film. The electrochromic properties are also studied. Compared with other coating methods, the sputtering coating method has the following advantages: (1) Any substance can be spattered, especially high melting point, l