Black silicon carbide Introduction

Silicon carbide is divided into black and green silicon carbide. Silicon carbide, also known as Moissanite. In contemporary C, N, B and other non-oxide refractory materials in high-tech, silicon White fused aluminum oxide carbide is the most widely used and most economical one. Can be called emery or refractory sand. Where: Black silicon carbide is quartz sand, petroleum coke and quality silica as the main raw material, smelting electric arc furnace. Its hardness between corundum and diamond, corundum higher mechanical strength, brittle and sharp. Silicon carbide, metallic luster, containing more than SiC 95%, greater than the intensity of green silicon carbide, but lower hardness, is mainly used for grinding cast iron and non-metallic materials

Advantages fused mullite

Porous ceramic fibers, adhesives, mullite precursor gel, mullite nanocrystals Introduction mullite has good properties, such as high melting point, a small expansion, thermal shock resistance, true specific gravity is low, creep resistance high and good chemical stability [] -21. From a porous material mullite fibers prepared with high porosity, lightweight, low thermal conductivity, high permeability, synthetic diamond non-brittle, etc., with a wide range of applications in the chemical, metallurgy, environmental protection and other areas will have great social and economic significance _3_. In fiber porous ceramic fibers rely architecture into the hole between the point of contact with the adhesive connection between the fibers, so the degree of solid adhesive bonding for excellent performance full of ceramic fiber base, end-use properties of the product from a decisive role. Considering the substrate used for forming porous mullite ceramic fibers, such as a binder with a sintered mullite crystalline phase, its crystalline phase cubic boron nitride and microstructure fibers with mullite and consistent with the same thermal expansion factor, after forming the porous ceramic having better performance. This paper used mullite fibers bonded with a porous ceramic mullite ceramics preparation and structure analysis.

Use of silicon carbide

Silicon carbide has four major application areas, namely: functional ceramics, advanced refractories, abrasives and metallurgical materials. SiC coarse material has been able to supply a large number, can not be considered high-tech products, while high-tech nano-silicon carbide powder steel fiber for concrete reinforcement is impossible to form a short application of economies of scale.
⑴ as an abrasive, can be used for abrasives, such as grinding wheel, Whetstone, grinding, sand tile and so on.
⑵ as metallurgical deoxidizer and high temperature materials.
⑶ high purity single crystal can be used sandblasting material for the manufacture of semiconductor manufacturing silicon carbide fibers.
Main purpose: for 3-12 inch monocrystalline silicon, polycrystalline silicon, gallium arsenide, quartz and other wire cutting. Solar photovoltaic industry, the semiconductor industry, piezoelectric crystal engineering of industrial processing of materials.
For semiconductors, lightning, circuit elements, high-temperature applications, UV detector, structural materials, astronomy, disc brakes, clutch, diesel particulate filter, filaments pyrometer, ceramic film, cutting tools, heating elements, nuclear fuel , jewelery, steel, protective gear, catalyst carrier body and other fields.

Synthetic diamond

Artificially non-diamond carbon structure into a diamond structure carbon , and are formed by nucleation and growth of monocrystalline and polycrystalline diamond, or the fine-grained diamond sintered polycrystalline diamond at high pressure and temperature . An important example of this is the high pressure applied in the current research on the production .
From the viewpoint of thermodynamics , the decision diamond structure of graphite and other non- carbonaceous material into a diamond can Phase Transition of the latter must be less than the free energy mold for grinding wheel of the former . This phase transition under conditions of high pressure , high temperature or other components participating conducted . Certain pressure , temperature and component concentration can make the system can change, so that the valence electrons can be right at the statistical level of weight change accordingly . This electron transfer , and may be bonded to form a new state of the electronic structure, i.e., the phase transition occurred . If the energy change in favor of the occurrence of this change in the electronic structure of the solid , the pressure and temperature in the solid state phase transition occurs , or may occur in the molten or vapor state . This change steel fiber for concrete reinforcement of condition occurs in the melt , the statistical characteristics of the right bonding valence electron distribution corresponding decrease weight , the effect tends to disappear remote ordered atomic coordination number changes ; statistical weight and the weight of electronic excited state chemotaxis at increasing the role of short-range order corresponding enhancement. This condition occurs in the gas change is elemental electron energy level bonding between atoms or molecules of the compound tends to disappear and all the electrons are transferred to a single atom or molecule level up , so that the electron is re- excited state statistical weight more is increased. Thus, the synthetic diamond may be in a solid state , but also in the melt state and the vapor state conditions , depending on pressure, temperature and component concentration changes can be caused by factors within the system . From the kinetic point of view, but also requires a change in the rate of change in the appropriate carbonaceous materials such as graphite into diamond when . Phase change rate of the diamond nucleation rate and growth rate at the same time when the maximum value is the maximum .

Fused zirconia mullite nature

Also known as fused zirconia mullite fused mullite brick, commonly known as iron or iron brick tiles, consisting mainly of the mineral  refractory materials  (60% to 70%) of fused cast refractories, is a weak acid refractories. The main component of an alumina content of 65% to 75%, a silica content of about 25% of the total oxides of the other 5% to 8%. Cast of relatively dense  crefractory materials brick, refractoriness of 1730 ~ 1800 ℃, load softening temperature of the beginning of 1700 ℃, high temperature strength and wear resistance, corrosion resistance is strong. A low coefficient of thermal expansion. Thermal conductivity is higher, therefore, thermal shock resistance than other cast brick well. High bauxite, alumina and fireclay industries as raw materials, furnace melting, casting, annealing and made. Mainly used in glass melting furnaces and other industrial kilns

Refractories are generally composed of a number of body

Wherein the mineral phase can be divided into two categories , i.e. the crystal phase and the glass phase .
The main phase is the main structure of the products constituting the crystalline phase and the higher melting point . Nature of the main phase , during which the number and combination of state Fused zirconia mullite directly determines the nature of the products .
Matrix is the large crystals of the refractory aggregate or substances present in the gap . Matrix on the nature of products ( such as high temperature resistance characteristics and resistance to invasion ornaments ) plays a decisive impact. When using the products, often starting with damage from the matrix section , the use of adjustments and changes in matrix components products are effective measures to improve product White fused aluminum oxide  performance process .
The vast majority of refractory products ( except for a few extra high refractory products outside ) , their main phase and matrix components can be divided into two categories : one is a multi-component refractory products containing crystalline phase and glass phase , such as clay , silica bricks ; Another multi-ingredient products containing only crystalline phase , mostly fine matrix crystals, such as brick, chrome magnesia brick and other basic refractories . These articles in high temperature firing , a certain amount of liquid , but does not form a liquid phase upon cooling the glass , but the formation of a crystalline matrix , the main crystal phase cemented together , the matrix component is different from the main phase crystal .
Microstructure There are two types of refractory products . A is a silicate ( silicate mineral crystal or vitreous ) binding was cemented type crystal particles , the crystal particles from the other is directly integrated into the crystalline network interlace , e.g. purity brick, this type of structure directly bonded high temperature properties ( temperature mechanical strength , slag resistance or thermal shock resistance , etc. ) products far superior than the previous one ; therefore have to have broad prospects for development .

Green silicon carbide replacement process Precautions

Any wheel wear problems have some wear and tear of its requirements, wear a certain extent it is necessary brown fused aluminum oxide to replace the new wheel. Not in order to save material, it requires the use of ultra-wear, which is a very unsafe illegal behavior. A general rule, when the wheel wear to a larger diameter than the diameter of 10mm chuck should be replaced with new wheel. Valid questions from the Treasury brought out a new wheel is not necessarily qualified wheel, new wheel even buy from the manufacturers are not necessarily qualified wheel. Any wheel has its certain expiration date, within the validity period of use, it is qualified wheel; than Glass beads valid use, it is not necessarily qualified wheel. Rules of order "wheel should be within the validity period, resin and rubber bonded grinding wheel rotating storage must be approved by the test, those who pass the year before use." Texture problems with the process, if you find a local wheel cracks, should immediately stop using and re-replacement of the grinding wheel, grinding wheel to avoid crushing injury accident.

White alumina

Alumina is a white aluminum oxide powder as raw material in electric arc furnace at high temperature smelting together, the main chemical ingredient of Al2O3 content is generally higher than 98%, higher brown fused aluminum oxide than corundum hardness, toughness lower than corundum, better cutting performance. It is made ​​by grinding, suitable for grinding hardened alloy steel, high speed steel, high carbon steel. Fine-grained powder suitable for high-precision optics polishing and polishing. Others include precision grinding wheels, precision glass, crystal polishing, and fine ceramics can be used