Tungsten oxide, also known as tungsten hua, chemical formula WO3. Pale yellow rhombic crystal, the color deepened when heated, and then returned to light yellow after cooling. Stable in air, melting point is 1473℃, boiling point is higher than 1750℃, relative density is 7. 16. Insoluble in water and inorganic acids except hydrofluoric acid, soluble in hot concentrated sodium hydroxide solution and ammonia water. Tungsten oxide is both an n-type semiconductor material and a “d0” oxide, which gives it many characteristics at the same time. Although it often exists in amorphous, monoclinic and hexagonal forms, its main frame is composed of tungsten-oxygen octahedron end to end.
According to the crystal shape and the surrounding environment, the octahedral element will be distorted in different ways, such as tilt and rotation, and the phenomenon that tungsten deviates from the octahedral body center is also accompanied. The existence of oxygen vacancy will have different effects on cell, bond length and electron structure, resulting in changes in charge distribution, energy gap and stoichiometric ratio. In addition, in its spatial skeleton, the pores enclosed by the tungsten-oxygen octahedron can be embedded with small cations to form tungsten-bronze. This process, in addition to showing increased electrical conductivity, results in the appearance of crystals such as monoclinic! The quartet! The symmetry of the cube keeps changing.
These special properties make tungsten oxide have catalytic, optical and electrical properties at the same time, and it is expected to be used in many fields such as photodecomposition of water, secondary lithium batteries and gas sensors. It is worth noting that the reversible transition process of tungsten oxide and tungsten bronze is always accompanied by the transfer of internal electrons and the change of tungsten valence, thus triggering the color change reaction and realizing the controllable adjustment of light transmission. This feature was first discovered in 1969 and has since been widely used in electrochromic applications such as smart Windows, rearview mirrors and large-area information displays.
The colored tungsten oxide is dark blue, which is suitable for daily household use due to its soft color and better light insulation performance. In addition, crystalline tungsten oxide also has a higher reflectivity to infrared after changing color, which can achieve similar thermal insulation effect with low radiation glass, thus helping to reduce indoor energy consumption. As a new functional material, tungsten oxide has many characteristics, such as low production cost, easy synthesis, low energy consumption, wide viewing Angle, high coloring efficiency, strong color contrast, long life, good stability, etc., which make it a research hotspot in the field of electrochromic.
Tungsten oxide is mainly used in the manufacture of metallic tungsten (reduced by hydrogen at high temperature), as well as hard tungsten ferroalloys, fire-resistant fabrics, piezoelectric ceramics and X-ray screens. It can also be used as colouring agent and analytical reagent for ceramic glaze. Examples of its application are as follows:
1. Prepare a tungsten oxide thin film with infrared barrier function.
Strong infrared blocking function of tungsten oxide film is described including matrix, formed on the substrate by amorphous tungsten oxide and tungsten oxide thin film of amorphous tungsten oxide mixture and form it is tungsten oxide film on the surface of the first layer, the valence state of tungsten elements in tungsten oxide film, the composition including tungsten ion and + 5 + 6 price price of tungsten ion.
Mentioned in the present invention has the function of infrared blocking of tungsten oxide film, including matrix formed on the substrate by amorphous tungsten oxide and tungsten oxide thin film of amorphous tungsten oxide mixture and form it is tungsten oxide film on the surface of the first layer, and amorphous tungsten oxide is mainly for more than 1500 nm infrared light has a good shielding effect, and amorphous tungsten oxide of 900-1200 nm infrared light has a good shielding effect.
2. For a tungsten oxide nanowire and tungsten oxide nanowire gas sensor.
Sodium tungstate solution was prepared by dissolving sodium tungstate in deionized water. Slowly drop hydrochloric acid to form light yellow micelle solution, centrifugal separation; The products are uniformly dispersed into potassium sulfate solution and transferred into a reaction kettle for hydrothermal reaction, that is, the tungsten oxide nanowires are prepared. An adhesive and a glass material are added to the tungsten oxide nanowires; Element sintering; Tungsten oxide nanowire gas sensor was prepared by the aging of components.
The invention simple preparation steps, process parameters in the process of preparation of easy to control, energy consumption of the whole process of preparation is very little, the preparation of tungsten oxide nanowires has large specific surface area and high thermal stability, tungsten oxide nanowires gas sensor for low concentration (1 to 100 parts per million (PPM) H2, CO and NH3 has high sensitivity, good repeatability and high stability.
The preparation of [2]
Tungsten concentrate (tungstate of manganese and iron) is alkalified, calcium chloride is converted, and then the acid is acidized to produce tungstate acid.
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