I. Silicon carbide structure and properties
Silicon carbide SiC contains silicon and carbon. It is a typical polymorphic compound, mainly including α-SiC (high temperature stable type) and β-SiC (low temperature stable type). There are more than 200 polymorphs, among which 3C-SiC of β-SiC and 2H-SiC, 4H-SiC, 6H-SiC, and 15R-SiC of α-SiC are more representative.
Figure SiC polymorph structure When the temperature is below 1600℃, SiC exists in the form of β-SiC, which can be made from a simple mixture of silicon and carbon at a temperature of about 1450℃. When it is higher than 1600℃, β-SiC slowly transforms into various polymorphs of α-SiC. 4H-SiC is easy to generate at around 2000℃; 6H and 15R polytypes are easy to generate at high temperatures above 2100℃; 6H-SiC can also remain very stable at temperatures above 2200℃, so it is more common in industrial applications. Pure silicon carbide is a colorless and transparent crystal. Industrial silicon carbide is colorless, light yellow, light green, dark green, light blue, dark blue and even black, with the degree of transparency decreasing in turn. The abrasive industry divides silicon carbide into two categories according to color: black silicon carbide and green silicon carbide. Colorless to dark green ones are classified as green silicon carbide, and light blue to black ones are classified as black silicon carbide. Both black silicon carbide and green silicon carbide are α-SiC hexagonal crystals. Generally, silicon carbide ceramics use green silicon carbide powder as raw materials.
2. Silicon carbide ceramic preparation process
Silicon carbide ceramic material is made by crushing, grinding and grading silicon carbide raw materials to obtain SiC particles with uniform particle size distribution, and then pressing the SiC particles, sintering additives and temporary adhesives into a green blank, and then sintering at high temperature. However, due to the high covalent bond characteristics of Si-C bonds (~88%) and low diffusion coefficient, one of the main problems in the preparation process is the difficulty of sintering densification. The preparation methods of high-density silicon carbide ceramics include reaction sintering, pressureless sintering, atmospheric pressure sintering, hot pressing sintering, recrystallization sintering, hot isostatic pressing sintering, spark plasma sintering, etc.
However, silicon carbide ceramics have the disadvantage of low fracture toughness, that is, greater brittleness. For this reason, in recent years, multiphase ceramics based on silicon carbide ceramics, such as fiber (or whisker) reinforcement, heterogeneous particle dispersion strengthening and gradient functional materials have appeared one after another, improving the toughness and strength of monomer materials.
3. Application of silicon carbide ceramics in the photovoltaic field
Silicon carbide ceramics have excellent corrosion resistance, can resist the erosion of chemical substances, extend service life, and will not release harmful chemicals, which meets environmental protection requirements. At the same time, silicon carbide boat supports also have better cost advantages. Although the price of silicon carbide materials themselves is relatively high, their durability and stability can reduce operating costs and replacement frequency. In the long run, they have higher economic benefits and have become the mainstream products in the photovoltaic boat support market.
When silicon carbide ceramics are used as key carrier materials in the production process of photovoltaic cells, the boat supports, boat boxes, pipe fittings and other products made have good thermal stability, are not deformed at high temperatures, and have no harmful precipitated pollutants. They can replace the currently commonly used quartz boat supports, boat boxes, and pipe fittings, and have significant cost advantages. Silicon carbide boat supports are made of silicon carbide as the main material. Compared with traditional quartz boat supports, silicon carbide boat supports have better thermal stability and can maintain stability in high temperature environments. Silicon carbide boat supports perform well in high temperature environments and are not easily affected by heat and deformed or damaged. They are suitable for production processes that require high temperature treatment, which is conducive to maintaining the stability and consistency of the production process.
Service life: According to the data report analysis: The service life of silicon carbide ceramics is more than 3 times that of boat supports, boat boxes, and pipe fittings made of quartz materials, which greatly reduces the frequency of replacement of consumables.
Post time: Oct-21-2024