Processing & Application of Powder Quartz
The quartz mined from the mine is processed, and the product with a fineness of less than 120 mesh becomes quartz sand, and the product with a fineness of more than 120 mesh is called quartz powder. It does not require mechanical grinding to obtain high-purity ultra-fine quartz powder, which is called powder quartz, which is different from vein quartz and quartzite.
The physical and chemical properties of powder quartz
- Particle morphology and particle size composition
Powder quartz particle shape: nearly equiaxed hexagonal polyhedron shape. Due to the effect of weathering and leaching, dissolution pits of varying degrees are formed on the surface of the particles. Corrosion passivation makes the particles have the characteristics of high sphericity (the three axes are nearly equal) and low roundness (with edges), which are called "quasi-spherical" particles.
The particle size distribution of powdered quartz is relatively narrow. The main particle size of 400 mesh products is distributed in the range of 5-20μm, the content is greater than 70%, the median particle size is about 14μm, and the particle size is normal.
- Mineral composition and chemical composition
Powder quartz composition: microcrystalline quartz, a very small amount of impurities such as kaolin, mica and plant debris.
The chemical composition of powder quartz: SiO2, Fe2O3, Al2O3, CaO, MgO, K2O, Na2O, TiO2, etc.; spectral analysis results show that powder quartz does not contain Cu, Mn and toxic elements, and other trace elements are close to or below the detection limit.
- Physicochemical properties
Powder Quartz: White, light white powder, Baidu is 50%~75%, brightness is 60%~80%; the dry powder has good dispersibility, no agglomeration, and the hand feels fine and smooth. Density: 2.55~2.65g/cm3, bulk density 1.96g/ml, sedimentation volume 0.6~0.9mg/g, Mohs hardness 7, refractive index 1.544.
The PH value is 6.3, the isoelectric point is PH value of 2~3.7, and the surface is negatively charged in the solution of PH value>3.7; the thermal stability temperature of powdered quartz is 573℃, the melting point is 1730℃, and it has excellent electrical insulation and chemical properties. Inertness and good acid corrosion resistance.
Mineralization Mechanism of Fine Quartz
- Geological characteristics of the deposit
It has the characteristics of both sedimentary deposits and weathered deposits. The ore body is similar in shape to general weathered disabled deposits. The ore body is simple "hat-shaped", layered, layered or belt-like.
- Geological conditions of mineralization
Most of the deposits exist in the Upper Paleozoic Devonian, Carboniferous and Permian strata. The generation of fine quartz ore is related to the regulation of carbonate rock formation, as well as siltstone and high calcareous quartzite. Fine quartz is a weathered crust type deposit, formed by weathered steps of parent rock.
Characterization and modification of powdered quartz
The mineral surface has surface reactive functional groups due to dangling bonds, which are called "surface sites".
Mineral-water interface effect: surface crystal growth and dissolution, surface precipitation and surface reaction. Mineral surface reactions: surface adsorption, oxidation-reduction and ex-situ catalytic reactions. These surface reactions are mainly determined by the reactivity of the mineral surface and various properties of the aqueous medium. The surface reactivity of minerals is usually related to surface properties such as mineral composition, surface structure and micro-topography.
Modification of powdered quartz: change the compatibility of the filler with organic polymers, reduce the viscosity of the filler-polymer mixed system, increase the filler, improve the infiltration and dispersibility of the filler in the polymer, eliminate chemical and mechanical damage points, improve the product Physical and mechanical properties.
Modification method of powdered quartz: dry method and wet method. The wet process is complex, high in cost, and less industrialized. Modification process: powdered quartz → preheating and stirring → (modification aid preparation →) modification aid → heating and drying → (coupling agent preparation →) silane coupling agent → surface modification → screening and degranulation → modification Pink quartz
Processing and Application of Powder Quartz
Natural powdered quartz generally has high purity and few impurities, and can be used without grinding. It is often used as a natural powdered siliceous material and is widely used in electrical insulation, waterproof and corrosion resistant, precision investment casting and new building materials. Powdered quartz is also used as the most common inorganic filler for epoxy resins in rubber, plastics and paint extender pigments.
Powdered quartz can be used in abrasive industry, glass industry, ceramic industry, paint manufacturing industry, rubber and plastic industry, coating industry, refractory materials, microporous calcium silicate insulation materials, etc.
In the abrasive industry, natural silica abrasive is one of the indispensable abrasive materials in the machining of precision parts in the machinery industry. It is widely used for sanding and matting and direct grinding of various high-finish mechanical parts.
In the glass industry, ordinary flat glass requires a SiO2 content of more than 96%. The SiO2 content of powdered quartz after grading desliming can reach 98%. It can be used for the production of flat glass only by sieving and removing the fine-grained powder.
In the ceramic industry, paint and pharmaceutical industry, rubber and plastic industry, powdered quartz products can be directly used after beneficiation processing and classification. The powder quartz used for ordinary ceramics is required to be above 98.5%, and the powder quartz after elutriation can almost meet these requirements. Some products using powdered quartz as raw materials are superior in performance to products made using veined quartz as raw materials. It can improve the strength and insulation of ceramics, as well as the durability and smoothness of paint. It can also make synthetic rubber and plastic products have high acid and alkali resistance.
There are also applications in the field of coatings, such as the use of modified powdered quartz in anti-radon coatings to replace heavy calcium used in traditional anti-radon coatings, reducing coating production costs and increasing the industrial added value of powdered quartz.
Powdered quartz is mainly used in refractory materials to produce high-density silica bricks and regulated refractory mud. The raw ore of powdered quartz has the characteristics of wide particle size distribution and low silicon content and low alumina. It is an ideal raw material for high-density silica bricks. The softening point is as high as 170°C, which is suitable for glass furnaces with higher melting temperatures. The siliceous refractory clay prepared with powdered quartz has high thermal strength, can significantly improve the masonry performance of silica bricks, prolong the service life of the furnace body, and reduce the masonry cost.
Precision casting is also called investment casting. Powdered quartz is mainly used as a filler for investment coatings. Investment coatings are prepared from sodium silicate, surfactants, water and powdered quartz. Powder quartz is mainly used as refractory material in investment coatings and improves the gloss of the casting surface. Therefore, the quality of powdered quartz directly affects the quality of the surface of the casting and the yield of casting.
The microporous calcium silicate insulation material is mainly synthesized by the hydrothermal gel reaction of siliceous raw materials and lime slurry. It has light bulk density, low thermal conductivity, high operating temperature, low heat loss... It is widely used in electric power, petroleum, chemical soil, light industry, construction and metallurgy and other fields. Commonly used raw materials have low SiO2 content, poor thermal insulation effect, and high cost of vein quartz. Powdered quartz is an ideal raw material for the synthesis of microporous calcium silicate.
Article source: China Powder Network