What is WO3?

WO3 stands for tungsten trioxide, an inorganic compound that is typically found as a yellow powder. It is insoluble in water, soluble in alkalis, and slightly soluble in acids (excluding hydrofluoric acid). Its molecular weight is 231.85, with the CAS number 1314-35-8 and EINECS number 215-231-4.

  1. Physical Properties of WO3

Color and Form:

  • WO3 usually appears as a yellow powder, but its color can change from light to dark upon heating.

Density and Melting Point:

  • The density of WO3 is 7.16 g/cm³.
  • Its melting point is 1473°C, and its boiling point is 1750°C. It sublimates significantly at around 850°C and appears green when molten.

Crystal Structure:

  • The crystal structure of WO3 changes with temperature:
    • Above 740°C: Tetragonal system
    • Between 330°C and 740°C: Orthorhombic system
    • Between 17°C and 330°C: Monoclinic system
    • Between -50°C and 17°C: Triclinic system
  • The monoclinic structure is the most common.
  1. Chemical Properties of WO3

Solubility:

  • WO3 is insoluble in water but dissolves in alkali and concentrated hot sodium hydroxide solutions. It is slightly soluble in acids (except hydrofluoric acid).

Stability:

  • WO3 is stable in air but may react violently under specific conditions, such as with halogen compounds.
  1. Applications of WO3

Hard Metals and Material Manufacturing:

  • WO3 is primarily used in the calcination-reduction process to produce tungsten powder and tungsten carbide powder, which are then used to manufacture hard metal products such as cutting tools and molds.
  • It is also used to make pure tungsten products, tungsten bars, tungsten wires, and tungsten electrodes.
  • Additionally, WO3 is utilized in counterweights and radiation shielding materials.

Energy and Environmental Protection:

  • WO3 is an effective photocatalyst and can be used for photocatalytic degradation of organic pollutants, showing potential for water treatment applications.
  • In the energy sector, WO3 nanowires have significant prospects as anode materials in rechargeable lithium-ion batteries.

Biomedical Applications:

  • WO3 has potential applications in biomedicine, such as in bioimaging, drug delivery, and photothermal therapy. However, these applications are still under research and exploration.

Other Applications:

  • In the marine industry, WO3 is used as a key ingredient in anti-corrosion paints and coatings.
  • It is also used in small quantities as a yellow pigment in ceramics.
  1. Health and Safety

Health Hazards:

  • WO3 is considered low in toxicity but can be irritating to the eyes and skin. Symptoms such as general weakness, fever, and measles-like rashes in workers involved in tungsten steel melting might be related to WO3 inhalation.

Safety Measures:

  • When handling WO3, appropriate protective equipment should be worn to avoid direct contact and inhalation. In case of contact, immediate first aid should be administered, and medical attention should be sought.

WO3, as an important inorganic compound, has a wide range of applications across various fields. However, its health and safety risks should be managed carefully during its use.

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