The silicon carbide material
Silicon carbide is an important raw material in modern industries. There are applications including advanced SiC ceramic, abrasive, non-slip, semiconductor, etc. Let’s see how it is developed.
The atomic rank NO. of carbon and silicon are 6 and 14. Respectively, they are in the second and third periods of the carbon group elements in the periodic table. This positional relationship means they have similar properties in some respects.
Carbon is ubiquitous in our lives, and carbon-containing compounds are the material basis of life. Silicon is also abundant in the earth’s crust, especially its application in semiconductors and modern communications, which has promoted the development of human civilization.
In the world of chemistry, carbon and silicon are like brothers of the same family. They have coexisted for billions of years on the earth, but have not formed a strong friendship of life and death. Silicon carbide ore in nature is very rare.
In 1824, Swedish scientist Jons Jakob Berzelius observed the existence of silicon carbide (SiC) when synthesizing diamond, which opened the prelude to human research on silicon carbide materials. Until 1891, American E.G. Acheson accidentally got silicon carbide when he was doing fused diamond experiments. At that time, scientists thought that material was a mixture of diamonds. So they called silicon carbide emery.
In 1893, Acheson developed a method for industrial smelting of silicon carbide, which is often referred to as the Acheson furnace, which has been in use today. This method is the same as the resistance furnace with carbonaceous material as the core body, and the mixture of quartz SiO2 and carbon is heated by electricity to generate silicon carbide.
The elements C and Si, have joined forces to make silicon carbide a material with many excellent chemical and physical properties:
superior chemical inertness
high hardness
high strength
low thermal expansion coefficient
high thermal conductivity
kind of semiconductor
Pure silicon carbide is a kind of transparent crystal. Industrial silicon carbide is pale yellow, green, blue, or even black due to the type and content of impurities. In the meantime, the transparency varies with its purity. The crystal structure of silicon carbide is divided into hexagonal or rhombohedral α-SiC and cubic β-SiC (cubic silicon carbide). The α-SiC constitutes many different variants due to the different stacking structures of C and Si. There are more than 70 types of SiC.
The common application of silicon carbide material is silicon carbide ceramics. It has the characteristics of high hardness, high corrosion resistance, and high-temperature strength. Today, the application of silicon carbide has developed from the earliest abrasives to many fields such as bearings, semiconductors, aerospace, and chemistry. Due to the high contact surface area between chemicals and the inner wall of the microchannel, the microreactor has very strict requirements on the material of the inner wall. Microchannel reactors have also become an important application of silicon carbide.