Why do alumina ceramic components have spots and how to prevent?

alumina ceramic tube

Alumina ceramic is a kind of ceramic material with a-al2o3 as the main crystal phase, because of its own high melting point, high hardness, heat resistance, corrosion resistance, and electrical insulation characteristics, it can be used in more stringent conditions. Alumina ceramics, with low price and mature production process, is one of the largest and most widely used ceramic materials, mainly used in the field of cutting tools, wear-resistant parts, and bioceramics. In addition, it is also widely used in energy, aerospace, chemical electronics, and other aspects. Especially 95% alumina and 99% aluminas, whether in structural ceramics or electronic ceramics are one of the most widely used ceramic materials.

In the production process of alumina ceramic parts, such as alumina ceramic tubes, alumina plates, and alumina rods there are often black, brown, and pink spots on the surface of the ceramic part, as well as on the inside. This spot is one of the main reasons for the unqualified alumina ceramic products.

The main impurities of black and brown spots are Fe, and the main impurities of pink spots are Fe, Cr, and Ni. By analyzing the composition of the spots and tracing the production process, it can be preliminary determined that the black and brown spots are mainly caused by mixing mechanical iron particles in advanced ceramic production. And pink spots from the composition analysis can be judged to be caused by stainless steel material fine particles.

Now we know the reason why alumina ceramic components have spots, how do we prevent and solve it?

• Raw materials: choose raw materials with good quality and low iron content as far as possible, and remove iron by magnetic separation when necessary.
• Grinding: pay attention to observing whether the ball mill lining brick falls off and timely repair.
• Granulation: slurry conveying with magnetic separation to remove iron, hot blast furnace, and hot air filtration to avoid hot air system rust into the material. The granulated powder is magnetically separated to remove iron before final product packaging.
• Piping: All piping should be lined with polyurethane whenever possible.