Publish Time: 2022-08-08 Origin: Site
Steel, coking, non-ferrous metals, and glass industries. With the continuous expansion of the application range of Fused Silica Ceramic, the preparation of its products has also put forward higher and higher requirements. Regarding the preparation of quartz ceramics, the two most important processes are forming and sintering. The pros and cons of each step will affect the performance of the final ceramic product. So what are the factors that affect the sintering of Fused Silica Ceramic? Let's see together.
The following is a list of contents:
Influence of forming method
Influence of sintering atmosphere
Influence the f sintering method
The effect of powder particle fineness
By selecting the appropriate Fused Silica Ceramic forming method according to the needs, a green body with uniform microstructure and uniform distribution of each phase can be obtained. By controlling and eliminating defects in the forming process, the sintering temperature and the green body shrinkage rate can be effectively reduced, and the densification can be an accelerated process, reducing the amount of machining of sintered products. In grouting, the dehydration of silica gel is difficult and the generated water vapor hurts sintering. Therefore, the sintering system should be slowly heated at low temperature and rapidly heated at high temperature, so that the green body can be fully dehydrated at low temperature. The sintering temperature and holding time should be determined according to the purity of the fused silica raw material and the particle size of the slurry. The raw material of Fused Silica Ceramic is very pure, the amount of impurities mixed in, the firing temperature can be higher, the purity of quartz glass is poor, and the firing temperature can be lower. In injection molding, the slurry contains 2% to 5% of organic binder, which needs to be removed during the firing process. Therefore, it is necessary to study the temperature at which the thermal decomposition of organic matter begins, the thermal decomposition rate at different temperatures, and the maximum temperature for complete burning, to formulate a reasonable burning process. Corresponding measures should be taken for parts of different sizes and shapes, which is an important link to ensure the quality of the blank and improve productivity.
The sintering atmosphere has a great influence on the structure of Fused Silica Ceramic, and a suitable sintering atmosphere is helpful for densification. It is reported that quartz products fired in an oxidizing atmosphere are more likely to form cristobalite. Therefore, to reduce the composition of cristobalite in Fused Silica Ceramic, it is advisable to fire in a neutral atmosphere or a reducing atmosphere.
Correct selection of sintering method is the key to making Fused Silica Ceramic have ideal structure and predetermined properties. A suitable sintering method can effectively reduce the sintering temperature. The normal pressure sintering of SiO2 ceramics is about 1200℃, the hot pressing sintering can obtain products with a density close to the theoretical density at a temperature lower than 1200℃, and the high-temperature isostatic pressing sintering can achieve densification at a lower temperature. The sintering of quartz ceramics is solid-phase sintering with diffusion mass transfer, and cristobalization is a major obstacle in sintering. Due to the crystallization of cristobalite crystals, the strength of the green body decreases, and the thermal expansion increases sharply, so the excellent thermal shock resistance of the material is lost. At the same time, to prevent cristobalization, it is advisable to adopt a sintering process of rapid heating, rapid cooling, and shortening the holding time at high temperatures as much as possible.
The effect of powder particle fineness
During sintering, fine particles lead to the acceleration of the sintering process by increasing the sintering driving force, shortening the atomic diffusion distance, and increasing the solubility of the particles in the liquid phase. At the same time, to prevent the occurrence of secondary recrystallization, fine and uniform raw material powder particles are required to avoid the abnormal growth of crystal grains caused by large grain nucleation in the base phase of fine particles. The particle size of Fused Silica Ceramic is not as fine as possible, it must conform to a certain particle gradation.
The above is the relevant content about the factors that affect the sintering of Fused Silica Ceramic. If you are interested in Fused Silica Ceramic, you can contact us. Our website is https://www.yufengrefractory.com/. I look forward to your arrival very much and hope to cooperate with you.