1. What is fused silica ceramic
Fused silica ceramics can also be called quartz glass ceramics or fused silica refractories. People generally call them quartz ceramics. It is made of fused quartz blocks or quartz glass. And the sintered body fired through a series of processes such as firing, the products with appearance requirements will also be cold processed to produce finished products.
Second, the advantages and disadvantages of fused silica ceramic performance
advantage:
①The coefficient of linear expansion is small, which is the same as or similar to that of quartz glass. It has good volume stability, and the refractory furnace made of fused silica ceramic brick can keep no expansion gap.
②The thermal shock stability is good, and it can be maintained at 1300 ℃ and 20 ℃ air or water for about 35 times, and it still does not break. It is different from the quartz glass that only needs a few cold and hot cycles to be destroyed.
③ Like quartz glass, it has good chemical stability and good acid resistance. Except that HF and concentrated phosphoric acid above 300 ℃ have an erosive effect on it, other hydrochloric acid, sulfuric acid and nitric acid have almost no effect on it.
④Viscosity is high under high temperature environment, good erosion resistance at high temperature, even at 2000 ℃ its viscosity is 100 times higher than ordinary glass melt.
⑤ The flexural and compressive strength will increase greatly with the rise of temperature. As the temperature rises, the plasticity will increase and the brittleness will decrease.
⑥It has good electrical properties and large resistance. Its dielectric constant (3.0 ~ 3.5) and dielectric loss tangent angle (<0.0004) change with temperature are much lower than corundum and high-temperature ceramics. It can be used as an insulating material and is also a radome. High-quality materials.
Disadvantages:
① There are problems such as low bulk density, high apparent porosity, loose structure, poor density and uniformity, etc., which results in low mechanical strength and flexural strength several tens of times lower than alumina ceramics.
② Crystallization is easy to occur during firing at high temperature or when it is used, and the glass phase is converted to the crystal phase. This property limits the increase in firing temperature, making it difficult to obtain a dense and high-strength preparation, which affects the performance of the product.
3. Application of fused silica ceramics
After decades of development and improvement, the performance of quartz ceramics has been improved, and the application field has also expanded from traditional refractory materials to glass, metallurgy, atomic energy, aerospace, defense and military industry (application fields include but are not limited to the following examples ):
①Deep processing of glass
Quartz ceramic rollers have become an irreplaceable key component in the horizontal glass tempering furnace, and the roller-type horizontal tempered glass furnace commonly used at home and abroad to produce tempered glass. In the glass horizontal tempering furnace, the rollers must transport the glass that is still in a softened state under high temperature conditions, so the high temperature strength, thermal shock stability, dimensional accuracy, surface finish, and wear resistance of the glass can be tolerated during the entire production process. There are very strict and strict requirements on the nature of the glass and whether there is pollution on the glass. These requirements also coincide with the performance characteristics of the quartz ceramic roller. It can be predicted that the quartz ceramic roller will have a relatively broad market prospect in the development of China's tempered glass industry.
②Float glass industry
Quartz glass has the advantages of small thermal conductivity, small thermal expansion coefficient, good thermal stability and not easy to adhere to tin ash impurities, which can improve the surface quality of the glass, so many large-size quartz glass products are widely used in the production of float glass. For example, gate bricks, cover bricks, breast wall bricks, support bricks, pressure bricks, etc.
③Metallurgy
In the steel casting operation, in order to effectively prevent the longitudinal cracking of the continuous cast steel slab, it is necessary to cast using the immersion nozzle protection method. The disadvantage of this method is that the conditions of the immersion nozzle are very harsh. The head of the immersion nozzle is used. Need to be inserted into the molten steel and protective slag, so that the inside and outside of the nozzle are at high temperature and heated at the same time, and the other part is fully exposed to the air. As a result, the material requirements of the immersion nozzle are strict, the thermal stability is good, the thermal conductivity is low, and it can be corroded by the molten steel and the slag. The quartz ceramic can meet these requirements at the same time, becoming one of the preferred materials for the immersion nozzle. .
④Electrical industry
Quartz ceramics have the advantages of high breakdown voltage, low dielectric constant, low loss tangent, good thermal shock stability, low thermal conductivity, and high temperature performance at room temperature or high temperature. They are stable in atomic equipment and are the only Materials that prevent neutron radiation are also excellent electrical insulators and light wave reflectors. In the electrical industry, quartz ceramics are widely used as insulating covers for gas discharge chambers, high-power resistance furnace heaters, diversion heaters, thermal protection diversion covers, arc extinguishers, light source devices for light quantum generators, gases Laser discharge cell components and electric heating components.
⑤Defense military industry
The excellent performance of quartz ceramics makes it one of the main candidate materials for missile radomes in the defense military industry. The quartz ceramic radome after fiber reinforcement and improvement not only will not be affected in terms of electrical performance, the dielectric performance is stable, and the strength is also increased by 14% compared with the original. The quartz ceramic missile radome can meet the requirements of radar wave transmission, small loss and small distortion, and can also meet the requirements of missile aerodynamic shape, resistance to aerodynamic heating and structural strength. In addition, because of its high temperature viscosity, the damage speed when passing through the atmosphere at high speeds above 2500 ° C is only 0.0025mm / s, so quartz ceramics can also be used as heat insulation materials for space vehicles and nozzles and heads of rocket engines Department and front room and other components.