The physical and chemical properties of nano silicon carbide and the four application fields

Overview of nano silicon carbide

Silicon carbide is an inorganic substance with a chemical formula of SiC. It is made by smelting raw materials such as quartz sand, petroleum coke (or coal coke), and wood chips (salt is needed to produce green silicon carbide) through a resistance furnace at high temperature. Silicon carbide also exists in nature, a rare mineral, moissanite. Among the non-oxide high-tech refractory materials such as C, N, and B, silicon carbide is the most widely used and most economical one, which can be called gold steel grit or refractory grit. The silicon carbide produced in China's industry is divided into black silicon carbide and green silicon carbide, both of which are hexagonal crystals, with a specific gravity of 3.20 to 3.25, and a microhardness of 2840 to 3320kg/mm2.

Development History

Silicon carbide is a kind of carbide accidentally discovered in the laboratory by American Acheson during the electrofusion diamond experiment in 1891. At that time, it was mistaken for a mixture of diamonds, so it was named emery. It was researched by Acheson in 1893. The industrial method of smelting silicon carbide, which is commonly referred to as the Acheson furnace, has been used until now. The resistance furnace with carbonaceous material as the furnace core is energized to heat the mixture of quartz SiO2 and carbon to generate silicon carbide.

Several events about silicon carbide

In 1905, silicon carbide was first discovered in a meteorite.

In 1907, the first silicon carbide crystal light-emitting diode was born.

In 1955, a major breakthrough in theory and technology, LELY proposed the concept of growing high-quality carbonization, and since then used SiC as an important electronic material.

In 1958, the first World Silicon Carbide Conference was held in Boston for academic exchanges.

In 1978, silicon carbide was mainly researched by the former Soviet Union in the 1960s and 1970s. By 1978, the grain purification and growth method of "LELY improved technology" was adopted for the first time.

From 1987 to now, a silicon carbide production line was established based on the research results of CREE, and suppliers began to provide commercial silicon carbide bases.

There are two basic varieties of silicon carbide, black silicon carbide and green silicon carbide, both of which belong to α-SiC. ① Black silicon carbide contains about 95% SiC, and its toughness is higher than that of green silicon carbide. It is mostly used to process materials with low tensile strength, such as glass, ceramics, stone, refractory materials, cast iron and non-ferrous metals. ②Green silicon carbide contains more than 97% SiC and has good self-sharpening properties. It is mostly used for processing cemented carbide, titanium alloy and optical glass, as well as for honing cylinder liners and fine grinding high-speed steel tools. In addition, there is cubic silicon carbide, which is a yellow-green crystal prepared by a special process. The abrasive tool used to make is suitable for super-finishing of bearings. The surface roughness can be processed from Ra32～0.16 microns to Ra0.04～ 0.02 microns.

The physical and chemical properties of nano silicon carbide

Due to its stable chemical properties, high thermal conductivity, low thermal expansion coefficient, and good wear resistance, silicon carbide has many other uses besides being used as abrasives. For example, silicon carbide powder is applied to the impeller or cylinder of a water turbine by a special process. The inner wall can increase its wear resistance and prolong its service life by 1 to 2 times; the high-grade refractory material made of it has heat shock resistance, small size, light weight, high strength, and good energy-saving effect. Low-grade silicon carbide (containing about 85% SiC) is an excellent deoxidizer, which can speed up the steelmaking speed, and facilitate the control of chemical composition and improve the quality of steel. In addition, silicon carbide is also widely used to make silicon carbide rods for electric heating elements.

Silicon carbide has a very high hardness, with a Mohs hardness of 9.5, second only to the world's hardest diamond (10). It has excellent thermal conductivity, is a semiconductor, and can resist oxidation at high temperatures.

There are at least 70 crystalline forms of silicon carbide. α-Silicon carbide is the most common kind of isomorphous crystal, which is formed at a high temperature higher than 2000 °C and has a hexagonal crystal structure (wurtzite-like). β-Silicon Carbide has a cubic crystal structure, similar to diamond, and is formed below 2000 °C. The structure is shown in the figure on the page. Although in the application of heterogeneous catalyst support, it is eye-catching because of its higher unit surface area than the α type, while another type of silicon carbide, μ-silicon carbide is the most stable and has a more pleasant sound when colliding. But until today, these two types have not yet been commercially applied.

Because of its 3.2g/cm3 specific gravity and high sublimation temperature (about 2700 °C), silicon carbide is very suitable as a raw material for bearings or high-temperature furnaces. It will not melt under any pressure that can be reached, and has a relatively low chemical activity. Due to its high thermal conductivity, high breakdown electric field strength and high maximum current density, many people try to use it to replace silicon in the application of semiconductor high-power components. In addition, it has a strong coupling effect with microwave radiation, and all its high sublimation points make it practical for heating metals.

Pure silicon carbide is colorless, while the industrially produced brown to black is due to impurities containing iron. The rainbow-like luster on the crystal is due to the silicon dioxide protective layer on the surface. To

Material structure

Pure silicon carbide is a colorless and transparent crystal. Industrial silicon carbide is light yellow, green, blue or even black due to the type and content of impurities, and its transparency varies with its purity. The crystal structure of silicon carbide is divided into hexagonal or rhombohedral α-SiC and cubic β-SiC (called cubic silicon carbide). α-SiC forms many different variants due to the different stacking sequences of carbon and silicon atoms in its crystal structure, and more than 70 kinds have been found. β-SiC transforms into α-SiC above 2100°C. The industrial manufacturing method of silicon carbide is to use high-quality quartz sand and petroleum coke to be refined in a resistance furnace. The refined silicon carbide blocks are crushed, acid-base washed, magnetic separation and sieving or water selection to make products of various particle sizes

Application of nano silicon carbide

Silicon carbide has four main application areas, namely: functional ceramics, advanced refractories, abrasives and metallurgical raw materials. Coarse silicon carbide materials can already be supplied in large quantities and cannot be regarded as a high-tech product, and the application of nano-scale silicon carbide powder with extremely high technical content is unlikely to form economies of scale in a short time.

⑴ As an abrasive, it can be used to make abrasive tools, such as grinding wheels, oilstones, grinding heads, sand tiles, etc.

⑵ As a metallurgical deoxidizer and high temperature resistant material.

⑶ High-purity single crystals can be used to manufacture semiconductors and silicon carbide fibers.

Main application: used for wire cutting of 3-12 inch monocrystalline silicon, polycrystalline silicon, potassium arsenide, quartz crystal, etc. Engineering processing materials for the solar photovoltaic industry, semiconductor industry, and piezoelectric crystal industry.

Used in semiconductors, lightning rods, circuit components, high temperature applications, UV detectors, structural materials, astronomy, disc brakes, clutches, diesel particulate filters, filament pyrometers, ceramic films, cutting tools, heating elements, nuclear fuels , Jewelry, steel, protective gear, catalyst carrier and other fields.

Abrasives

Mainly used for making grinding wheels, sandpaper, belts, whetstones, grinding blocks, grinding heads, grinding pastes, and grinding and polishing of monocrystalline silicon, polycrystalline silicon and piezoelectric crystals in the electronics industry in photovoltaic products.

Chemical industry

It can be used as a deoxidizer for steelmaking and an improver for cast iron structure, as a raw material for the manufacture of silicon tetrachloride, and is the main raw material for the silicone resin industry. Silicon carbide deoxidizer is a new type of strong composite deoxidizer, which replaces the traditional silicon powder and carbon powder for deoxidation. Compared with the original process, various physical and chemical properties are more stable, and the deoxidation effect is good. It shortens the deoxidation time, saves energy and improves Steelmaking efficiency, improvement of steel quality, reduction of consumption of raw and auxiliary materials, reduction of environmental pollution, improvement of working conditions, and improvement of the overall economic benefits of electric furnaces are all of great value.

"Three-resistant" material

Using silicon carbide has the characteristics of corrosion resistance, high temperature resistance, high strength, good thermal conductivity, and impact resistance. On the one hand, silicon carbide can be used in various smelting furnace linings, high temperature furnace components, silicon carbide plates, lining plates, supports, and saggers. , Silicon carbide crucible, etc.

On the other hand, it can be used for high-temperature indirect heating materials in the non-ferrous metal smelting industry, such as vertical distillation furnaces, rectification furnace trays, aluminum electrolytic cells, copper melting furnace linings, arc plates for zinc powder furnaces, thermocouple protection tubes, etc. ; Used to make high-grade silicon carbide ceramic materials such as wear resistance, corrosion resistance and high temperature resistance; it can also be used to make rocket nozzles, gas turbine blades, etc. In addition, silicon carbide is also one of the ideal materials for solar water heaters on highways and aviation runways.

Non-ferrous metals

The use of silicon carbide has high temperature resistance, high strength, good thermal conductivity, and impact resistance. It can be used as high temperature indirect heating material, such as hard pot distillation furnace, rectification furnace tray, aluminum electrolytic tank, copper melting furnace lining, and arc for zinc powder furnace Pattern plate, thermocouple protection tube, etc.

Steel

Using silicon carbide's corrosion resistance, thermal shock resistance, wear resistance, and good thermal conductivity, it is used in large blast furnace linings to increase the service life. To

Metallurgical beneficiation

The hardness of silicon carbide is second only to diamond, and it has strong wear resistance. It is an ideal material for wear-resistant pipes, impellers, pump chambers, cyclones, and hopper linings. Its wear resistance is 5 times the service life of cast iron and rubber. -20 times is also one of the ideal materials for aviation flight runways.

Building Material Ceramic Grinding Wheel Industry

The use of its thermal conductivity, thermal radiation, high thermal strength, and the manufacture of thin-plate kiln furniture can not only reduce the capacity of the kiln furniture, but also increase the capacity and product quality of the kiln, and shorten the production cycle. It is ceramic glazed baking and sintering. Ideal indirect material. 

Energy saving

Using good heat conduction and thermal stability as a heat exchanger, the fuel consumption can be reduced by 20%, the fuel can be saved by 35%, and the productivity can be increased by 20-30%, especially in the discharge pipeline used in the mine dressing plant, its wear resistance It is 6-7 times that of ordinary wear-resistant materials.

The particle size and composition of the abrasive are in accordance with GB/T2477-83. The determination method of abrasive particle size composition is in accordance with GB/T2481-83.

Jewelry

Synthetic Moissanite, also known as synthetic moissanite, synthetic moissanite (chemical composition SiC), has a dispersion of 0.104, which is larger than diamond (0.044), a refractive index of 2.65-2.69 (diamond 2.42), and has the same diamond luster as diamond , "Fire Color" is stronger, closer to diamonds than any imitations in the past.

Sandblasting and rust removal

This product is made of brown corundum powder through high-strength pressure extrusion, high-temperature sintering and molding, moderate hardness, clean and clean, not easy to break. Repeated use, sandblasting effect is good.

1. The surface of steel, steel pipe, steel structure stainless steel products is matt treatment, sandblasting and rust removal treatment before spraying.

2. Used for cleaning various molds.

3. It can remove the tensile stress of various mechanical parts and increase the fatigue life.

4. Cleaning and removing edge thorns before tinning on semiconductor devices and plastic encapsulation tubes.

5. Shot peening intensified finishing of medical equipment, textile machinery and various hardware products.

6. Cleaning and removing burr residues of various metal pipes and non-ferrous metal precision castings.

Nano silicon carbide price

The price of nano-silicon carbide will vary randomly with the production cost, transportation cost, international situation and market supply and demand of nano-silicon carbide. Tanki New Materials Co., Ltd. aims to help various industries and chemical wholesalers find high-quality, low-cost nanomaterials and chemicals by providing a full set of customized services. If you are looking for nano silicon carbide products, please feel free to send an inquiry to get the latest price of nano silicon carbide.

Nano silicon carbide supplier

As a global supplier of nano silicon carbide, Tanki New Materials Co., Ltd. has extensive experience in the performance, application and cost-effective manufacturing of advanced engineering materials. The company has successfully developed a series of powder materials (including boron carbide, hard alloy aluminum, titanium carbide, etc.), high-purity targets, functional ceramics and structural devices, and provides OEM services.