Quartz ceramics is the use of special production process means processing of amorphous silicon dioxide produced by the sintered body with excellent resistance to thermal shock. In addition, the quartz ceramic green body shrinkage less than 6%, easy and accurate measurements made products, is a good prospect of development and utilization of heat resistant ceramic material.
If the pure quartz or fused silica glass waste as raw material, in accordance with the traditional process can not be made of dense ceramic sintered body, that is, less than 2% water absorption of the quartz ceramic. Large size square quartz ceramic crucibles for solar cells is the production of polysilicon ingots used in the main consumption of materials, due to extremely harsh conditions of use of crucible purity, strength, appearance defects, inherent quality, high temperature performance, thermal stability, vibration, size, precision of There is very strict requirements.
The only control the international quartz ceramic slip casting and gel casting technology, manufactures a U.S. company, so only a few have a domestic polysilicon ingot furnace manufacturers are dependent on imports, the price alone crucible up to 700 U.S. dollars, silicon wafer production plant with annual output of 10MW four 240kg ingot furnaces need to consume 668 quartz ceramic crucibles calculations. According to the existing domestic production capacity is estimated that the number of crucible need to import up to more than 6800, with expansion up to 15,000 after the total demand only. Many manufacturers are studying a way for the structure of quartz ceramics crucible dense uniform, the overall uniformity of good performance, good thermal stability and ingot products during the crucible of heat Cracking capacity crucible sintering process. The following describes a manufacturing process of quartz ceramics.
Quartz ceramic products are mainly raw materials used for fused silica fragments, its chemical composition: SiO2 98.25%; Al2O3 0.15%; FeO3 0.13% free carbon 0.21%; on ignition 0.17%. Selection of raw materials for industrial mineral additives or chemical reagents, such as: Magnesium, silicon and boron calcium stones, Ling Mei ore, lithium carbonate, industrial alumina. The fused silica material crushing to all passed 100 mesh sieve, and then 200 mesh sieve for sifting, screening material for the finely ground under the head when the material, sieve the material for the two materials.
Within the broken bits into the ball milling, ball milling of rubber lined to agate balls as grinding media. Meet the requirements fineness mud, with plaster models, slip casting, stripping dried green body. Impregnated green body at about 1100 ? calcined to form a high strength, dipping liquid for the slurry put it aside for 24 hours after the melting of the upper plastic body. The introduction of additives for the formulation does not affect the performance of the mud forming take the additives mixed with the raw material, after grinding, after high temperature synthesis 980 1000 ?. After crushing the first sintered material, together with finely ground. Firing temperature to formulate a strict curve, firing temperature is 1200 ?, only the fire is being re heat 5 minutes.
Fine grinding of raw materials, the feeding methods of grouting Green density and sintering effects. Experiments show that the sintering of quartz ceramics mechanism is mainly the surface of solid phase diffusion and the proliferation of green body, therefore, improve the green body density and increase the proportion of fine particles of quartz ceramics is conducive to densification. Use of secondary raw material crushing feeding methods are conducive to raising the Green density and sintered green body. This is because the time between feeding in most of the particles as particles, the second intermediate size particle content when feeding less, then slip casting process can produce a more dense accumulation of poly, there is a high Green density.
Green density, the contact area between particles on the large, for the sintering provided favorable conditions for proliferation. At the same time, an appropriate extension of milling time, increase the surface area of particles in green body, but also can promote the sintering of dense green body. But the milling time is too long, may change the particle size distribution of raw materials and reasonable, Green density, but reduced, should be strictly monitored.
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