Quartz, geology terminology, generally refers to low temperature quartz (α-quartz), is the most widely distributed mineral minerals in quartz. Generalized quartz also includes high temperature quartz (β-quartz), Ke Shiying and so on. The main ingredient is SiO2, colorless and transparent, often contain a small amount of impurity composition, and become translucent or opaque crystal, hard texture. Quartz is a physical property and chemical properties are very stable mineral resources, crystal is a triad of oxide minerals.
Quartz is a stable mineral at room temperature, insoluble in water and sulfuric acid, hydrochloric acid, nitric acid. Hardness 7, specific gravity of about 2.65, melting point 1713 ℃. Glossy glassy, sometimes faty. Texture is purely colorless; with impurities are red, yellow, blue, black, brown, purple, green; transparent to opaque, crisp. Fracture was shell-like or mixed. Crystal was hexagonal columnar, column with stripes. There is a difference between left and right Quartz crystals. Twin crystals are common. Quartz is a non-plastic material, and its clay in the high temperature generated mullite crystal to give porcelain higher mechanical strength and chemical stability, and can increase the translucent body, is the preparation of white glaze good raw materials.
The role of quartz in porcelain billet
(1) quartz raw materials are barren raw materials, it has a ceramic body in the heating at room temperature have an important impact. Before sintering, the quartz in the blank material on the plasticity of the role of the transfer agent, and can Quartz reduce the shrinkage in drying, shorten the drying time and prevent the deformation of the body (including deformation and collapse).
(2) quartz in the firing process, the emergence of crystal transformation, volume expansion, can offset the partial shrinkage of the body. As the quartz crystal transition will cause changes in volume, so in the heating and cooling process should be carefully controlled cooling and heating rate, to avoid cracking products.
(3) When firing, the heating expansion of quartz properly counteracts the sintering of the billet, and when the glass phase is present in a large amount, the quartz becomes the skeleton of the ceramic, which prevents the body from bending during firing And other defects.
(4) high temperature chemical affinity is very strong, with a variety of other oxide compounds, high temperature liquid viscosity is very high, increase the green body binding capacity.
(5) to increase the mechanical strength and transparency of the body.
The role of quartz in enamel
(1) Quartz in the glaze, the more fusible CaO, Na2O, K2O, MgO melt to produce transparent quartz glass, so that glazed bright, improve the glaze gloss.
(2) quartz in the glaze in the thermal expansion coefficient is small, good heat resistance.
(3) quartz softening temperature is high, high temperature liquid viscosity.
(4) quartz can increase the mechanical strength of glazed, improve the glaze hardness, so that porcelain wear, and chemical stability Ye Hao, not affected by the erosion of acid.
(5) make the glaze transparent and bright.
Quartz In the production of glazed tiles, the amount of quartz in the green body is generally 10-20%, in a firing glazed tile body in the amount of less, usually 10-15%, in the amount of glaze frit 20-40%. The white body requires a higher purity for quartz, while the colored green body can be made of less pure quartz. In a burnt wall tiles of the body is often not directly added to the quartz, but by the introduction of clay with clay.