Thermal properties of quartz glass tube
1. temperature since the quartz glass tube is a glass tube, the structure of disorderly arrangement, so it has no melting point, because the viscosity at high temperature of quartz glass tube, even reached the softening point of 1713 DEG C viscosity still has 108 lakes, and 20 DEG C as hard asphalt, at 1850-1900 DEG C, a viscosity of 104-105 poise, quartz glass tube until vaporization (2100 DEG C) will not become very dilute. According to the United States, the viscosity of the strain point is 1014.5 mooring, the annealing point is 1013 mooring, and the softening point is 108 mooring. The deformation point of quartz glass tube is 1075 C, annealing point 1180 C, softening point 1730 C, hot processing temperature range: viscosity 105-8 mooring, 1700-1850 centigrade. The high continuous temperature of quartz glass tube: 1100 C, short time can be used at 1450 C.
The minimum heat coefficient of 2. hot quartz glass tube, heat it with high temperature, can withstand without bursting (also called cold and hot well), quartz glass tube sheet is heated to 1500 DEG, 20 DEG C water rapidly into not burst. The product industry stipulates that heating the quartz glass tube tube to 1100 degrees and holding it for 15 minutes, and immediately putting it into 20 + 5 centigrade, the water will quench rapidly, and no cracks, gaps and caving larger than 3mm will happen. The average thermal coefficient of quartz glass tube is 0-100 C 5.1 x 10-7, 0-200 C is 5.8 x 10-7, 0-300 C is 5.9 x 10-7, 0-600 centigrade is 5.4 x 10-7, 0-900 degree is 4.8.
3. the volatilization of volatilization of quartz glass tube at high temperature is related to the surface area. At 1800, the vapor pressure of SiO2 is 0.1mmHg, 2000 C is 0.4mmHg, and 2500 C is 10mmHg. The quartz glass tube is heated to 2000 DEG SiO2 will decompose or sublime SiO2, SiO+1/2 O2, so when 1900-2000 DEG C for processing the flame, a smoke zone in strong heat outside the region formed in the air, smoke SiO and O2 synthesis of SiO2 condensation on the surface of the quartz tube, even the furnace mouth also has such a smoke.
The average specific heat of 4. specific heat and thermal conductivity of quartz glass tube is 0-100 DEG C is 772 J /kg.k0, 0-500 DEG C to 964 J /kg.k0, 0-900 DEG C to 1052 J /kg.k0, thermal conductivity of quartz glass tube was 20 DEG C for 1.38W/kg.m, 200 degrees 1.55W/kg.m, 400 degrees for 1.84 W/kg.m, 950 DEG C for 2.68 W/kg.m.
The crystallization properties of 5. quartz glass tube (also known as the crystallization properties of quartz glass tube or devitrification) tended to be silica at high temperature crystal (quartz), this is called recrystallization, also known as the "lost", from the beginning of recrystallization nucleation, quartz glass tube is very pure, no nucleation in glass tube almost so, the recrystallization usually occurs at the surface, surface contamination (e.g., cleaning is not good, straight touch surface etc.), heating clean impurities especially alkali metal ions (K, Na, Li) and alkaline earth metal ions (Ca, Mg), these ions will recrystallization temperature of 200-300 DEG C, and recrystallization speed and temperature, the higher the temperature the higher the crystallization speed. The quartz glass tube industry stipulates: the quartz glass tube in the semiconductor industry is kept for 6 hours at 1400 + 5 degrees, the average thickness of the crystalline layer should be < 100 micron m. When the electric light source is used for quartz glass tube, it is kept for 0.5 hours at 1200 degrees, the transmittance of the unit thickness sample at 500nm wavelength should not be less than 85%.
The high temperature of 6. color quartz glass tube fused quartz glass tube tube which is heated to 900-1000 DEG C, some plant products will become colored quartz glass tube tube, said high temperature (heat discoloration discoloration), mainly because of metal impurity content in quartz glass tube caused by high pressure, vacuum furnace products, may also be carbon (C the content of the cause). And the valence state of metal impurities in quartz glass tube also has a relationship, the consensus is that: iron, cobalt, nickel and manganese influence, but the rock song glass tube cobalt, nickel and manganese content is very small, so focus on the iron content, iron content of GE quartz glass tube has been reduced to below 0.3ppm. So they are not thermochromism thermochromism, provisions of quartz glass tube industry, the product is heated to 1000 DEG C under heat for 2 hours, the thickness of the sample units in the heat treatment at a wavelength of 290nm before and after the change of the average transmittance of T shall not be greater than 4%.

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