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  powder...

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...

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, esp...

Because the grain uniformity of hard alloy mainly depends on the particle size distribution of WC powder, the particle size distribution of WC powder is hereditary in tungsten powder . Therefore, the preparation technology of tungsten powder and tungsten carbide powder by submicron size and narrow size is very important. The key technical indexes of fine grain, submicron, ultrafine or nanocrystalline cemented carbide for WC powder are the purity, particle size and particle size distribution, and it is clearly stipulated that there is no type of type III coarse in WC powder. Some scholars have adopted the following technical schemes to prepare submicron tungsten powder or tungsten carbide powder, including the following steps: (1) Ammonium paratungstate (APT) is pyrolyzed to ammonium metatungstate (AMT) and dissolved in ammonia solution or deionized water and filtered to obtain ammonium tungstate solution, or using ammonium paratungstate (APT) production line after ion exchange or cryst...

At present, the general method of preparing tungsten oxide is liquid phase method. In the process of preparing tungstic acid in liquid phase, the tungstic acid particles are automatically coalesced because of the unstable thermodynamics. In addition, the free water molecules on the surface of the particles form hydrogen bonds with the free hydroxyl groups, and then form a hydrogen chain with the water molecules on the surface of the adjacent particles to produce a bridging action. Some scholars have proposed a method of adjusting the length of tungsten oxide nanorod by oxygen, with a surface functionalized carbon nanotube with a diameter of 2-200 nm and a layer of 1-30 layers as the carrier, tungsten metal salt as the tungsten source, the addition of hydrochloric acid in the carbon nanorod glycol suspension and tungsten metal salt system, and the principle of making the weak acid with strong acid to make tungstate granules. It directly forms on the surface of the carbon nanotubes and ...

The wolframite is brittle and easy to smash and produce fine slime, and most of them have fine embedded granularity and more useful metal minerals. The gangue minerals are closely related to tungsten minerals, and the separation is difficult. Many fine grain tungsten can not be recycled. Then it forms tailings. Some scholars have proposed a comprehensive mineral processing scheme for recycling wolframite from tailings, including the following steps: (1) Centrifuge gravity separation and tail preconcentration, after the wolframite tailings are adjusted to pulp, the centrifugal concentrator is used to preconcentration and discarding tailings, and the concentrate and tailings of centrifugal gravity separation are obtained. (2) The concentrate is floated by the first coarse second sweep process, and the flotation tailings and sulfide ore concentrate are obtained. (3) Magnetic separation of flotation tailings by magnetic separation is carried out, and magnetic separation concentrate and ma...