Color And Properties Of Silicon Carbide

Color and properties of silicon carbidePure silicon carbide is colorless and transparent crystal, industrial silicon carbide has fog color, light yellow, light green, dark green, light blue, dark blue and even black, the degree of transparency decreases in turn. Silicon carbide is generally divided into black silicon carbide (commonly used code C in China) and green silicon carbide (code GC) two categories. Which from the fog color to the dark green SiC are classified into green silicon carbide; Dark blue to black are classified as black silicon carbide.The reason for the color of silicon carbide is not fully understood. It is generally believed that it is related to the existence of various impurities. When more carbon is dissolved in the crystal, the SiC crystal is black; Aluminum has a great influence on the color of SiC, which can make the crystal brownish-black or black; Boron can also make SiC crystal black; The presence of iron has no effect on the formation of green silicon carbide; Some rare earth oxides (such as Ce2O3, etc.) can be green or dark green in SiC crystals. In addition, the dispersion of nitrogen atoms in SiC crystals can make the crystals turn green. The higher the concentration of nitrogen atoms, the darker the color of SiC crystals. Color and properties of sicThere is a certain statistical relationship between the color of silicon carbide and the type of crystallization. Green silicon carbide is basically 6H type, some contain 5%~10% of 15R type; Black silicon carbide is also mainly 6H type, but contains more 15R and 4H type (see Table 2-3-1). Color and properties of silicon carbide.

From the chemical composition, it can be seen that black silicon carbide contains free Si, C (graphite-like), Fe203, MgO, Al203 and other impurities are usually higher than green silicon carbide (see Table 2-3-2). But this is not good, black silicon carbide in the SiC content is higher than green silicon carbide is also a common thing; Colorless transparent silicon carbide is not necessarily high in SiC, and often contains more SiO2. Silicon carbide color and characteristics

Black and green silicon carbide have slightly different mechanical properties. It is generally believed that compared with the two, green silicon carbide is harder and more brittle, and black silicon carbide is tougher and slightly softer. There is a group of comparative data: green SiC Vickers microhardness 32000~34000MPa, microbrittleness index 7.5~9; Black SiC is 31000~328000 MPa and 6.2~8.0.Green SiC is different from black SiC manufacturing process characteristics are: ① the use of purer raw materials; ② salt is added to the ingredients. Silicon carbide refractories generally use black silicon carbide as raw materials, one is its high toughness, and the other is cheaper than green silicon carbide in price.Green and black silicon carbide fine powder is mainly identified by chemical analysis, the former SiO2, Fe203, low content, the latter is high. Color and properties of silicon carbide