Silicon carbide (SiC), also known as carborundum, is a compound of silicon and carbon with chemical formula SiC. It occurs in nature as the extremely rare mineral moissanite. Silicon carbide powder has been mass-produced since 1893 for use as an abrasive. Grains of silicon carbide can be bonded together by sintering to form very hard ceramics that are widely used in applications requiring high endurance, such as car brakes, car clutches and ceramic plates in bulletproof vests. Electronic applications of silicon carbide as light-emitting diodes (LEDs) and detectors in early radios were first demonstrated around 1907, and today SiC is widely used in high-temperature/high-voltage semiconductor electronics. Large single crystals of silicon carbide can be grown by the Lely method; they can be cut into gems known as synthetic moissanite. Silicon carbide with high surface area can be produced from SiO2 contained in plant material.

1 . Abrasive and cutting tools

In the arts, silicon carbide is a popular abrasive in modern lapidary due to the durability and low cost of the material. In manufacturing, it is used for its hardness in abrasive machining processes such as grinding, honing, water-jet cutting and sandblasting. Particles of silicon carbide are laminated to paper to create sandpapers and the grip tape on skateboards.

In 1982 an exceptionally strong composite of aluminium oxide and silicon carbide whiskers was discovered. Development of this laboratory-produced composite to a commercial product took only three years. In 1985, the first commercial cutting tools made from this alumina and silicon carbide whisker-reinforced composite were introduced by the Advanced Composite Materials Corporation (ACMC) and Greenleaf Corporation.

2 . Structural material

In the 1980s and 1990s, silicon carbide was studied in several research programs for high-temperature gas turbines in Europe, Japan and the United States. The components were intended to replace nickel superalloy turbine blades or nozzle vanes. However, none of these projects resulted in a production quantity, mainly because of its low impact resistance and its low fracture toughness.

Like other hard ceramics (namely alumina and boron carbide), silicon carbide is used in composite armor (e.g. Chobham armor), and in ceramic plates in bulletproof vests. Dragon Skin, which is produced by Pinnacle Armor, uses disks of silicon carbide.

Silicon carbide is used as a support and shelving material in high temperature kilns such as for firing ceramics, glass fusing, or glass casting. SiC kiln shelves are considerably lighter and more durable than traditional alumina shelves.

3 . Automobile parts

Silicon-infiltrated carbon-carbon composite is used for high performance "ceramic" brake discs, as it is able to withstand extreme temperatures. The silicon reacts with the graphite in the carbon-carbon composite to become carbon-fiber-reinforced silicon carbide (C/SiC). These discs are used on some road-going sports cars, supercars, as well as other performance cars including the Porsche Carrera GT, the Bugatti Veyron, the Chevrolet Corvette ZR1, Bentleys, Ferraris, Lamborghinis, some specific high performance Audis, and the McLaren P1.[37] Silicon carbide is also used in a sintered form for diesel particulate filters. SiC is also used as an oil additive to reduce friction, emissions, and harmonics.

4 . Electric systems

The earliest electrical application of SiC was in lightning arresters in electric power systems. These devices must exhibit high resistance until the voltage across them reaches a certain threshold VT, at which point their resistance must drop to a lower level and maintain this level until the applied voltage drops below VT.

It was recognized early on that SiC had such a voltage-dependent resistance, and so columns of SiC pellets were connected between high-voltage power lines and the earth. When a lightning strike to the line raises the line voltage sufficiently, the SiC column will conduct, allowing strike current to pass harmlessly to the earth instead of along the power line. Such SiC columns proved to conduct significantly at normal power-line operating voltages and thus had to be placed in series with a spark gap. This spark gap is ionized and rendered conductive when lightning raises the voltage of the power line conductor, thus effectively connecting the SiC column between the power conductor and the earth. Spark gaps used in lightning arresters are unreliable, either failing to strike an arc when needed or failing to turn off afterwards, in the latter case due to material failure or contamination by dust or salt. Usage of SiC columns was originally intended to eliminate the need for the spark gap in a lightning arrester. Gapped SiC lightning arresters were used as lightning-protection tool and sold under GE and Westinghouse brand names, among others. The gapped SiC arrester has been largely displaced by no-gap varistors that use columns of zinc oxide pellets.

5 . Power electronic devices

Silicon carbide is a semiconductor in research and early mass-production providing advantages for fast, high-temperature and/or high-voltage devices. First devices available were Schottky diodes, followed by Junction-gate FETs and MOSFETs for high-power switching. Bipolar transistors and thyristors are currently developed.[29] A major problem for SiC commercialization has been the elimination of defects: edge dislocations, screw dislocations (both hollow and closed core), triangular defects and basal plane dislocations. As a result, devices made of SiC crystals initially displayed poor reverse blocking performance though researchers have been tentatively finding solutions to improving the breakdown performance. Apart from crystal quality, problems with the interface of SiC with silicon dioxide have hampered the development of SiC-based power MOSFETs and insulated-gate bipolar transistors. Although the mechanism is still unclear, nitridation has dramatically reduced the defects causing the interface problems. In 2008, the first commercial JFETs rated at 1200 V were introduced to the market, followed in 2011 by the first commercial MOSFETs rated at 1200 V.[citation needed] Beside SiC switches and SiC Schottky diodes (also Schottky barrier diode – SBD) in the popular TO-247 and TO220 packages, companies started even earlier to implement the bare chips into their power electronic modules. SiC SBD diodes found wide market spread being used in PFC circuits and IGBT power modules. Conferences such as the International Conference on Integrated Power Electronics Systems (CIPS) report regularly about the technological progress of SIC power devices. Major challenges for fully unleashing the capabilities of SiC power devices are:

gate drive: SiC devices often require gate drive voltage levels that are different from their silicon counterparts and may be even unsymmetic, e.g. +20V and -5V.

 packaging: SiC chips (Die (integrated circuit)) may have a higher power density that silicon power devices and are able to handle higher temperatures exceeding the silicon limit of 150°C. New die attach technologies as sintering are required to efficiently get the heat out of the devices and ensure a reliable interconnection.
 

6 . LEDs

The first LED action was demonstrated in 1907 using SiC and the first commercial LEDs were again based on SiC. Yellow LEDs made from 3C-SiC were manufactured in the Soviet Union in the 1970s,and blue ones (6H-SiC) worldwide in the 1980s.[46] The production was soon stopped because gallium nitride showed 10–100 times brighter emission. This difference in efficiency is due to the unfavorable indirect bandgap of SiC, whereas GaN has a direct bandgap which favors light emission. However, SiC is still one of the important LED components – it is a popular substrate for growing GaN devices, and it also serves as a heat spreader in high-power LEDs.

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Tungsten alloy shield is used to shield the radioactive material, thus making a shielding device to avoid radiation damage. The main advantage of using a tungsten alloy shield  compared with being made ​​of lead :

1: The greater tdensity,and the better radiation ability. 11.34 density is the density of lead, tungsten alloy density is 16.5 to 19.0.

2: Non-toxic and more environmentally friendly. Lead itself and its compounds are toxic to human tissues, is likely to cause heavy metal pollution in the course of heavy metal poisoning, will produce secondary bremsstrahlung. The tungsten alloy tungsten itself is not toxic and will not output radioactive substances, environmentally harmless.

3:Rich reserves of tungsten, tungsten alloy and relatively easy processing.

4: Thickness small. The same shielding effect, the thickness of the tungsten heavy alloy is only two-thirds of the lead.


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Gamma radiation is an electromagnetic wave, it's even shorter than the wavelength of X-rays, high energy, with a strong penetrating ability. It will destroy the cellular and molecular structure of organisms, cause harm to humans.

1: Tungsten nickel alloy to gamma-ray absorption coefficient of 137 Cs0.661MeV is 0.0987cm^-1,and semi-absorption thickness is 0.376cm.

2: Tungsten nickel alloy to gamma ray absorption coefficient of 60Co 1.33MeV  is 0.0470cm^-1. Semi-absorption thickness is 0.827659574cm.

3: Tungsten nickel alloy to absorption coefficient of 226Ra  is 0.1843cm^-1. Semi-absorption thickness is 3.203472599cm.


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Tungsten alloy green bullets, also known as environmental green bullets.tungsten alloy  has the characteristics of hardness, wear resistance, high density, high temperature strength, chemical stability, corrosion resistance and other significant advantages. Tungsten alloy not only can replace lead bulletsas the main raw material , and tungsten alloy bullet performance is also better than the lead head bullets, its intensity should head over lead bullets. United States military has completed a "clean" development work bullets, and now this has been replaced by lead bullet head bullet, but this green bullet tungsten alloy head than lead bullets cost is slightly higher.

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