The Study On Reflection And Absorption Of Infrared Radiation Coating Using In Silicon Single Crystal Furnace

Two kinds of coatings are investigated in this paper: one coating is high-reflection of infrared radiant coating and the other coating is high absorption of infrared radiant coating. The high-reflective coating is used on the surface of the graphite insulation tube of the thermal field to replace or reduce the original graphite felt insulation materials, so that part of the heat that is radiated to the graphite insulation tube by a heater can be reflected to heat space. The high absorptive coating is used on the surface of crystal pulling furnace, which rapidly absorbs the heat that is given off during the solidification process of monocrystalline, then the heat is conducted by the recycled water of the furnace, thus the temperature gradient is increased and coagulation rate and quality are improved.Reflectivity and absorption experiments have been carried out for the selected materials to find out the ingredient recipes of the coatings relative with high reflectivity and large absorptivity.By means of orthogonal experimental design, analyzing the effect of reflective coatings with different proportions of filler on its reflectance according to experiments, the effects order of factors has been obtained: hollow bead has the max influence, followed by the ZrO₂, TiO₂ and Cr₂O₃. Based on this formulations, the addition of each filler were changed in the experiments and the best formula is Al₂O₃ 50g, ZnO 30g, SiO₂ 20g, hollow beads 30g, ZrO₂ 12g, TiO₂ 7g and Cr₂O₃ 11g, the reflection rate is 92%.Again through orthogonal experimental design method, based on the ingredient recipes of the absorptive coating, the infrared absorption experiments of the coating have been carried out under sintering at different temperatures, time and additives content so as to seek out that the optimal sintering process is 1280℃×2h and the amount of additives is 25g. Ultimately the final best formula of absorptive coating is SiC50g, Fe3O435g, nano-graphite powder 15g, additives 25g. When coating thickness is 300μm, the absorptivity is 89.9%.On the basis of the above experiments, further tests have been carried out to verify the effects of reflective and absorptive coatings on the high temperature Experimental results showed that: when the temperature ranging from 400℃to 800℃, the difference temperature of cylinder with reflective coating between the internal and the outer is 270²80℃, and the inner temperature is 60⁸0℃higher than the one without such coating. The difference temperature between the internal and the outer of the no coating cylinder is 85⁹5℃.The internal temperature of the cylinder with absorptive coating is 15²0℃lower than the one without such coating while the outer temperature of the former is 15²0℃higher than the latter one.Thermal efficiency of the thermal field in single crystal growth furnace has been calculated with the heat transfering theory, and the results show that: amount of radiation heat transfer with a coating reflecting the infrared radiation is 32875W/m less than the one uncoated.