Physical and Chemical Objectives of Ultrafine Calcined Kaolin

Ultrafine calcined kaolin is an important industrial non-metallic mineral deposit, with the scientific name of hydrous Aluminium silicate (aluminosilicate clay mineral deposit), and its chemical composition is Al2O3 2SiO2 2H2O. It is a light gray fine-grained powder with a triclinic crystal structure and a quasi hexagonal configuration. The specific gravity is 2.8, the hardness is 1.0 Mohs, and the refractive index is 1.56. It is a slightly acidic mineral substance, but still has good acid and alkaline resistance. In addition to possessing the characteristics of general mineral powder, it has a significant insulation effect on infrared radiation, but is prone to moisture absorption and should be dry before use.

How to dry kaolin

The dryness performance of kaolin refers to the performance of kaolin mud during the drying process. Including dryness shortening, dryness intensity, and dryness sensitivity.

Kaolin dry shortening refers to the shortening of kaolin clay after dehydration and drying. Kaolin clay generally dehydrates and becomes dry at temperatures ranging from 40-60 ℃ to no more than 110 ℃. Due to the discharge of water, the particle distance is shortened, and the length and volume of the sample are shortened. Dry shortening is divided into line shortening and body shortening, indicated by the percentage change in length and volume of kaolin mud after drying to constant weight. The drying line of kaolin is generally shortened by 3-10%. The finer the particle size, the larger the specific surface area, the better the plasticity, and the greater the dry shortening. The shortening of the same type of kaolin varies depending on the amount of water added, with more having a greater shortening. In ceramic technology, if the dry shortening is too large, the body is prone to deformation or cracking.

The drying strength of kaolin refers to the flexural strength of the mud after being dried to constant weight.

The dryness sensitivity of kaolin refers to the degree to which deformation and cracking tendencies may occur when the body is dry. High sensitivity, easy to deform and crack during dry processes. Generally, kaolin with high dry sensitivity (dry sensitivity coefficient K>2) is prone to defects; The lower (dry sensitivity coefficient K<1) is safer in dry environments.