Corundum is a crystalline form of aluminum oxide (Al₂O₃) that is well - known for its hardness and various industrial applications. There are different types of corundum, each with unique properties and uses. As a white corundum supplier, I am often asked about the differences between white corundum and other types of corundum. In this blog, I will explore these differences in detail.
Chemical Composition
The primary chemical component of all corundum types is aluminum oxide. However, the purity and the presence of trace elements vary among different types.
White corundum is characterized by its high purity. It typically contains over 99% aluminum oxide (Al₂O₃). The high purity gives it a white color, as there are very few impurities to introduce other colors. This high - purity composition makes white corundum an excellent choice for applications where chemical stability and a clean working environment are required.
In contrast, brown corundum, one of the most common types of corundum, has a lower purity. It usually contains around 95 - 97% aluminum oxide, with the remaining percentage consisting of impurities such as titanium dioxide (TiO₂), silicon dioxide (SiO₂), and iron oxide (Fe₂O₃). These impurities give brown corundum its characteristic brown color and also affect its physical and chemical properties.
Synthetic corundum can be engineered to have different chemical compositions depending on its intended use. Synthetic corundum is often produced to mimic the properties of natural corundum or to have enhanced characteristics. For example, some synthetic corundum may be doped with specific elements to improve its hardness or optical properties.
Physical Properties
Hardness
All corundum types are relatively hard, with a Mohs hardness of around 9, second only to diamond. However, due to its high purity, white corundum has a more uniform crystal structure, which can result in a slightly higher effective hardness in some applications. This makes it suitable for precision grinding and polishing tasks where a consistent cutting edge is required.
Brown corundum, with its impurities, has a more complex crystal structure. While it is still very hard, the presence of impurities can cause micro - fractures under high - stress conditions. This property makes brown corundum more suitable for rough grinding applications where a self - sharpening effect is beneficial.
Color
As mentioned earlier, color is a clear visual indicator of the differences between corundum types. White corundum's white color is a result of its high purity, making it ideal for applications where color contamination is a concern, such as in the production of white or light - colored products.
Brown corundum's brown color is due to the presence of iron and other impurities. This color is not an issue for most industrial applications where the final product's color is not critical, such as in general - purpose grinding wheels.
Density
The density of corundum can also vary slightly depending on its type. White corundum generally has a density in the range of 3.9 - 4.0 g/cm³. Brown corundum, with its lower purity and the presence of lighter impurities, has a slightly lower density, typically around 3.8 - 3.9 g/cm³.
Manufacturing Process
The manufacturing processes of different corundum types also contribute to their differences.
White corundum is produced by melting high - purity alumina powder in an electric arc furnace at extremely high temperatures (around 2000 - 2200°C). The molten material is then cooled slowly to form large, uniform crystals. This process ensures the high purity and consistent quality of white corundum. After the initial formation, the white corundum is crushed, screened, and further processed into various sizes, such as White Fused Alumina Grain and White Corundum Micro Powder.
Brown corundum is made from bauxite, a naturally occurring ore that contains aluminum oxide along with other impurities. The bauxite is first calcined to remove moisture and then smelted in an electric arc furnace. During the smelting process, the impurities are partially removed, but some still remain in the final product. The resulting brown corundum is then crushed and screened to obtain the desired particle sizes.
Synthetic corundum can be produced through various methods, such as the Verneuil process, the Czochralski process, or the flux - growth method. These methods allow for precise control of the chemical composition and crystal structure of the synthetic corundum, making it possible to tailor its properties for specific applications.
Applications
Abrasive Applications
In the abrasive industry, the differences in properties between white corundum and other corundum types lead to different applications.
White corundum is widely used in precision grinding and polishing operations. Its high purity and consistent hardness make it suitable for grinding hard and brittle materials, such as carbide tools, ceramics, and optical glass. The fine - grained White Corundum Micro Powder is often used for high - precision polishing of surfaces, where a smooth and scratch - free finish is required.
Brown corundum is commonly used in general - purpose grinding applications. It is used in grinding wheels for grinding steel, cast iron, and other metals. The self - sharpening property of brown corundum due to its impurities allows it to maintain its cutting ability during long - term use, making it a cost - effective choice for large - scale grinding operations.
Refractory Applications
Refractory materials are used in high - temperature environments, such as in furnaces and kilns.
White corundum's high purity and chemical stability make it an excellent refractory material. It can withstand high temperatures without significant chemical reactions or deformation. It is used in the lining of high - temperature furnaces, such as those used in the steel and glass industries.
Brown corundum can also be used in refractory applications, but its lower purity may limit its performance in extremely high - temperature and corrosive environments. However, it is still a popular choice for some less - demanding refractory applications due to its lower cost.
Cost and Availability
Cost is an important factor when considering different corundum types. White corundum, due to its high - purity raw materials and more complex manufacturing process, is generally more expensive than brown corundum. However, its superior properties make it a worthwhile investment for applications where precision and quality are crucial.
Brown corundum is more readily available and less expensive. Its raw material, bauxite, is abundant in nature, and the manufacturing process is relatively straightforward. This makes brown corundum the preferred choice for applications where cost is a major consideration and where the properties of white corundum are not strictly necessary.
Synthetic corundum's cost can vary widely depending on its production method and the specific properties it is engineered to have. In some cases, synthetic corundum may be more expensive than natural corundum if it has been designed with advanced properties, but in other cases, it can be cost - competitive due to mass - production techniques.
Conclusion
In summary, white corundum differs from other types of corundum in terms of chemical composition, physical properties, manufacturing process, applications, cost, and availability. As a white corundum supplier, I understand the unique requirements of different industries and can provide high - quality white corundum products that meet those needs. Whether you are in the precision grinding, polishing, or refractory industry, our White Fused Alumina Grain and White Corundum Micro Powder can offer the performance and quality you expect.
If you are interested in learning more about our white corundum products or would like to discuss your specific requirements, please feel free to contact us for a detailed consultation and to start the procurement process. We look forward to working with you to find the best corundum solutions for your business.
References
- "Industrial Minerals and Their Uses" by John D. Webster
- "Ceramics: Science and Technology" by J. Reed
- "Abrasive Technology Handbook" by R. K. Jain