What distinguishes the quality of kaolin from what it is and what is its criterion for judging

Judgment and standard of good or bad kaolin:

The chemical composition of kaolin contains a large amount of Al2O3, SiO2 and a small amount of Fe2O3, TiO2 and trace amounts of K2O, Na2O, CAO and MGO. Kaolin is the basis of ceramic embryo body molding, with good plasticity and bonding, can effectively reduce the deformation and cracking of the embryo body, has high fire resistance and whiteness, can enhance mechanical strength, can improve thermal and chemical stability and sintering performance, in ceramic glaze and other processes have a good suspension and adsorption effect. The product also has the advantages of high aluminum oxide content, low harmful impurities such as iron, manganese and titanium, stable quality of raw ore and concentrate of ore deposits, etc., and is a high-quality kaolin.

Kaolin is a non-metallic mineral, which is a clay and clay rock dominated by kaolinite clay minerals. Because it is white and delicate, it is also called dolomites. It is named after Gaoling Village, Jingdezhen, Jiangxi Province.

Its pure kaolin is white and delicate, soft soil, and has good physical and chemical properties such as plasticity and fire resistance. Its mineral composition is mainly composed of kaolinite, halloysite, mica, illite, montmorillonite, quartz, feldspar and other minerals. Kaolin is widely used, mainly used in papermaking, ceramics and refractory materials, followed by coatings, rubber fillers, enamel glazes and white cement raw materials, and a small amount of plastics, paints, pigments, grinding wheels, pencils, daily cosmetics, soaps, pesticides, medicine, textiles, petroleum, chemicals, building materials, national defense and other industrial sectors.

Kaolin is a soft clay mineral and a non-clay mineral with kaolinite subgroup minerals as the main component. Kaolinite minerals are mainly composed of tiny flake or tubular kaolinite group minerals less than 2 m Al4 Si4O10 (OH)8. Due to its aluminosilicate chemical composition, layered structure and particulate properties, it has many special properties that are not found in general minerals.

The wide range of uses of kaolin is inseparable from its excellent physical properties. Pure kaolin has high whiteness, soft quality, easy to disperse and suspend in water, good plasticity and high adhesion, excellent electrical insulation properties, good acid resistance solution, very low cation exchange capacity, high refractory and other physical and chemical properties.

Pure kaolin has high whiteness, soft quality, easy to disperse and suspend in water, good plasticity and high adhesion, and excellent electrical insulation properties; It has good acid solubility, very low cation exchange capacity, good fire resistance and other physical and chemical properties. Therefore, kaolin has become an essential mineral raw material for dozens of industries such as papermaking, ceramics, rubber, chemicals, coatings, pharmaceuticals and national defense. There are also reports that kaolin is also used in Japan to replace steel in the manufacture of cutting tools, lathe drill bits and internal combustion engine housings.

Especially in recent years, the rapid development of modern science and technology has made the application of kaolin more extensive, and some high-tech fields have begun to use kaolin as a new material, and even the high-temperature porcelain parts of atomic reactors, space shuttles and spacecraft are also made of kaolin.

Whiteness is one of the main parameters of kaolin process performance, and kaolin with high purity is white. The whiteness of kaolin is divided into natural whiteness and whiteness after calcination.

The color of kaolin is mainly related to the metal oxides or organic matter it contains. Generally, it contains Fe2O3, which is rose red and brownish yellow; Containing Fe2+, light blue, light green; Contains mNO2 and is light brown; It contains organic matter and is light yellow, gray, cyan, black and other colors. The presence of these impurities reduces the natural whiteness of kaolin, and iron and titanium minerals can also affect the whiteness of calcination, causing stains or scars on porcelain.

Al2O3·2SiO2·2H2O relative molecular weight 258

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Oxides of silicon, aluminum, iron, titanium, potassium, sodium andLoss on ignition

Kaolin. Mineral-like species are made of kaolinite.

Kaolinite cluster minerals such as daffite, perlite, and halloysite are composed of mineral components, and the main mineral component is kaolinite. It belongs to the 1:1 type layered silicate, and the crystal is mainly composed of silicon-oxygen tetrahedron and aluminum-hydroxide-octahedron, in which the silicon-oxygen tetrahedron is connected along the two-dimensional direction in the way that the sparrow shares the apex angle to form a hexagonal arrangement of grid layers.

Features:

During the firing process of dried kaolin adobe, a series of physicochemical changes occur (dehydration, decomposition, formation of mullite.

Fusible impurities melt to form glass phase filled in the void between the particles, etc.), and the performance of product shrinkage is also divided into two types: linear shrinkage and bulk shrinkage.

Like drying shrinkage, the firing shrinkage is too large, which is easy to lead to cracking of the sedan body. In addition, if a large amount of quartz is mixed in the blank during roasting, it will undergo a crystal transformation (trigonal hexagonal), which will expand its volume and also produce reverse shrinkage.