About Inorganic Materials – Cerium Oxide
Cerium oxide is an inorganic substance with the chemical formula CeO₂. It appears as a pale yellow or yellowish-brown powder. It has a density of 7.13 g/cm₃ and a melting point of 2397°C. It is insoluble in water and alkali, but slightly soluble in acid. At 2000°C and 15 MPa, cerium oxide can be reduced with hydrogen to produce cerium trioxide. At temperatures between 2000°C and pressures above 5 MPa, cerium oxide exhibits a yellowish-reddish color, sometimes even pink. It is used as a polishing material, catalyst, catalyst carrier (additive), UV absorber, fuel cell electrolyte, automobile exhaust absorber, and electronic ceramics.
Ⅰ.Uses
Oxidant. Catalyst for organic reactions. Rare earth metal standard for steel analysis. Redox titration analysis. Decolorize glass. Glass enamel sunscreen. Heat-resistant alloy.
Used as an additive in the glass industry, as a grinding material for plate glass, and in cosmetics as a UV inhibitor. It has been expanded to include polishing eyeglass glass, optical lenses, and cathode ray tubes, providing decolorization, clarification, and absorption of ultraviolet and electron beams.
Ⅱ.Rare Earth Effects
1.Rare Earth Polishing Effects
Rare earth polishing powders offer the advantages of fast polishing speed, high finish quality, and long service life. Compared to traditional iron oxide polishing powders, they are environmentally friendly and easy to remove from contaminants. Cerium oxide polishing powders can polish lenses in one minute, while iron oxide polishing powders would take 30 to 60 minutes. Therefore, rare earth polishing powders offer the advantages of low dosage, fast polishing speed, and high polishing efficiency. They can also improve polishing quality and the operating environment. Rare earth glass polishing powders are typically made from cerium-rich oxides. Cerium oxide is an extremely effective polishing compound because it can polish glass simultaneously through chemical decomposition and mechanical friction. Rare earth cerium polishing powders are widely used in polishing cameras, video camera lenses, television picture tubes, eyeglass lenses, and other applications. my country has dozens of rare earth polishing powder factories, with over ten boasting production capacity exceeding 100 tons. Baotou Tianjiao Qingmei Rare Earth Polishing Powder Co., Ltd., a Sino-foreign joint venture, is one of my country’s largest rare earth polishing powder manufacturers, with an annual production capacity of 1,200 tons. Its products are sold domestically and internationally.
2.Glass Decolorization
All glass contains iron oxide, which can be introduced into the glass through raw materials, sand, limestone, and cullet in the glass batch. It exists in two forms: divalent iron, which turns the glass dark blue, and trivalent iron, which turns it yellow. Decolorization involves oxidizing the divalent iron ions to trivalent iron, as trivalent iron has only one-tenth the intensity of its divalent counterpart. A color corrector is then added to neutralize the color to a light green.
The rare earth elements used for glass decolorization are primarily cerium oxide and neodymium oxide. Rare earth glass decolorizers replace traditional white arsenic decolorizers, improving efficiency while avoiding arsenic contamination. Cerium oxide has the advantages of high-temperature stability, low cost, and non-absorption of visible light for glass decolorization.
3.Glass Coloring
Rare earth ions exhibit stable, vibrant colors at high temperatures and are used to create various colored glass by adding them to liquids. Rare earth oxides such as neodymium, praseodymium, erbium, and cerium are excellent glass colorants. When transparent glass with these colorants absorbs visible light between 400 and 700 nanometers, it exhibits beautiful colors. These colored glasses can be used to create indicator light covers for aviation, navigation, and various transportation vehicles, as well as various high-end artistic decorations.
When neodymium oxide is added to soda-lime and lead glass, the depth of the glass’s color depends on the thickness, neodymium content, and the intensity of the light source. Thin glass appears pale pink, while thicker glass appears bluish-purple. This phenomenon is known as neodymium dichroism. Praseodymium oxide produces a green similar to chromium. Erbium oxide, used in photochromic glass and crystal glass, produces a pink hue. Cerium oxide combined with titanium dioxide creates a yellow hue. Praseodymium oxide and neodymium oxide can be used in praseodymium-neodymium black glass.
4.Rare Earth Clarifiers
Cerium oxide, instead of traditional arsenic oxide, is used as a glass clarifier to remove bubbles and trace coloring elements. This is particularly effective in producing colorless glass bottles, resulting in a crystal-white glass with excellent transparency, enhanced glass strength, and improved heat resistance. It also eliminates arsenic pollution to the environment and glass itself.
Additionally, cerium oxide can be added to everyday glass, such as architectural and automotive glass, and crystal glass, to reduce UV transmittance. This application has been widely adopted in Japan and the United States. With the improvement of living standards in my country, it is also expected to find a strong market. Neodymium oxide, added to cathode ray tube glass, eliminates red light dispersion and enhances clarity. Specialty glasses with rare earth additions include: lanthanum glass, with its high refractive index and low dispersion, is widely used in the manufacture of various lenses and advanced camera and camcorder lenses, especially those for high-altitude photography equipment; cerium radiation-proof glass, used in automotive glass and television glass; and neodymium glass, an ideal material for large lasers, primarily in controlled nuclear fusion devices.
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