What Are the Differences between Green Silicon Carbide and Black Silicon Carbide

Silicon carbide (SiC) is a high-performance non-metallic material that plays an important role in many industries. Green silicon carbide and black silicon carbide are its two main varieties.

Green SiC Powder vs. Black SiC Powder: What Are the Differences

Although they both belong to the basic category of α-SiC, they exhibit significant differences in production processes, physicochemical properties, and application fields. Understanding these differences can help us choose this special material more accurately.

--Production Process

Green SiC powder is produced by high-temperature smelting of high-purity quartz sand and high-purity petroleum coke. The quartz sand contains over 99.5% SiO₂, and the petroleum coke contains over 98% carbon, with extremely low impurity levels. The smelting process takes a longer time, usually 30-40 hours, to ensure that the raw materials fully react and generate high-purity silicon carbide crystals. Additionally, the smelted SiC undergoes steps to remove iron impurities and metal oxides, resulting in a higher final product purity.

Fig 1. Green SiC powder

Black SiC powder uses ordinary quartz sand and regular petroleum coke as raw materials, which have higher impurity levels, especially with significant amounts of metal oxides such as iron and aluminum. The smelting time is shorter, typically 20-30 hours, and the reaction is not as complete as that of green SiC. After smelting, metal oxides are generally not removed.

Fig 2. Black SiC powder

--Property Differences:

Property	Green SiC	Black SiC
Purity	Extremely high, typically ≥98.5%, some high-end products ≥99.5%	Typically between 95%-98%
Hardness Mohs hardness	9.5, close to diamond Mohs hardness	9.2-9.3, slightly lower than green SiC
Toughness	Lower, more brittle, easily shattered	Higher, less brittle, better impact resistance
Crystal Structure	Uniform crystal structure, few impurity distributions	Irregular crystal structure, more impurity distributions
Thermal Conductivity	Higher, good thermal stability	Slightly lower, but still has good thermal stability
Electrical Properties	Better insulation performance	Slightly higher than green silicon carbide
Color	Light green or bright green	Deep black or gray-black

Why Do They Have Different Colors

The color of silicon carbide is primarily determined by its purity and crystal structure. Green silicon carbide uses high-purity raw materials with extremely low impurity levels. As a result, the crystal structure is uniform, the grain size is smaller, and light scattering within the crystal is reduced. Additionally, the bandgap width of silicon carbide determines its strong absorption of blue and violet light while weakly absorbing green light. Therefore, it ultimately appears light green or bright green.

On the other hand, black silicon carbide uses ordinary raw materials with higher impurity levels. The crystal structure is irregular, the grain size is larger, and impurities form defects within the crystal, causing a large amount of light absorption, resulting in a deep black or gray-black color.

--Application Fields

Due to the differences in physicochemical properties, green SiC and black SiC also differ in their application fields.

Green silicon carbide, because of its high purity, high hardness, and excellent mechanical properties, is widely used for precision grinding of hard alloys, quartz glass, optical glass, and crystal wire cutting. Especially in the field of semiconductor material processing, green silicon carbide micropowder is an important raw material for producing single-crystal silicon and polycrystalline silicon cutting wafers, where the grain size and purity directly affect the cutting quality and efficiency. Additionally, green silicon carbide is also used in high-temperature and highly corrosive environments such as aircraft engines, gas turbines, and chemical equipment due to its good high-temperature resistance and chemical stability.

Black silicon carbide, due to its higher toughness and good wear resistance, performs excellently in grinding materials such as alloys, ceramics, marble, and jade. It is also used to manufacture high-hardness, wear-resistant tools and parts, such as grinding media, grinding wheels, and cutting discs. In the ceramics field, black silicon carbide can be combined with other ceramic materials to produce high-performance composite ceramics to meet specific engineering needs. Furthermore, black silicon carbide is widely used in refractory materials, aerospace, automotive manufacturing, and other fields.

Green SiC Powder vs. Black SiC Powder: How to Choose

This requires consideration of the usage scenario and budget. Generally speaking, their applicable scenarios are:

Green SiC powder: Suitable for high-precision, high-performance, and high-budget scenarios, such as precision machining, semiconductor materials, and advanced ceramics.
Black SiC powder: Suitable for general grinding, refractory materials, wear-resistant materials, and cost-sensitive scenarios.