Monday, July 22, 2024
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Silicon carbide is an excellent abrasive

Silicon carbide is an excellent abrasive. More than one hundred grinding wheels and other abrasive products have been produced and made. Years, history. Today, the material has been developed as a typical industrial-grade ceramic with very good mechanical properties. It is used in abrasives, refractories, ceramics and many high-performance applications. The application of silicon carbide (SiC) is accelerating the development of power semiconductors in various fields from electric vehicles to solar photovoltaics and industrial engines, but where does this material come from? What's special? When silicon carbide was first used as the basis of radio detectors more than a century ago, why did it take so long to gain favor in the semiconductor industry?
Stardust on boots
The earth's crust contains about 28% silicon and 0.03% carbon, so you might think that after a long journey in the country, you will find that there is enough silicon carbide (SiC) to stick some semiconductor chips on the sole of the boot. If you walk past a meteor impact crater, you may find some spots-the only naturally occurring SiC is moissanite, fragments of supernovae or ejections of carbon-rich red giant stars, which are collected in space and eventually formed in meteorites Micron-sized particles. It is indeed stardust.
SiC LED is ahead of transistors
In the early 20th century, experimenters discovered that crystals of various substances such as germanium would produce "asymmetric current" or rectification. This kind of crystal has been used in "crystal" radio. When trying to use silicon carbide, strange phenomena occur. The crystal emits yellow light, sometimes green, orange or even blue. The first LED was discovered 40 years ago in the transistor.
As an LED, SiC was quickly replaced by gallium arsenide and gallium nitride, and its luminous performance increased 10 to 100 times. However, as a material, SiC is still attracting attention in the electronics field. Its thermal conductivity is 3.5 times that of silicon, and it can be heavily doped to obtain high conductivity while still maintaining high electric field breakdown. Mechanically, it is very hard, inert and has a very low thermal expansion coefficient and a high rated temperature. SiC will not even melt-it will sublime at about 2700°C.
Copy the first experiment showing the LED effect of SiC
We may have never noticed the existence of SiC, but in 1891, the American inventor Edward G Acheson tried to find a way to produce artificial diamonds by heating clay (aluminum silicate) and carbon. He noticed that the luminous hexagonal crystals attached to the carbon arc lamp used for heating were called composite emery, which he believed was a form of crystalline alumina like corundum. He may think that he is the second best because rubies and sapphires are types of corundum, but he realizes that he has something new. This compound is almost as hard as diamond and can be in chip or powder form on an industrial scale. 

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