Synthesis ntawm mullite
Cov txheej txheem synthesis ntawm mullite tuaj yeem muab faib ua sintering txoj kev thiab hluav taws xob melting txoj kev. Sintering txoj kev tuaj yeem muab faib ua txoj kev qhuav thiab ntub txoj kev raws li txoj kev ntawm raw khoom npaj. Cov txheej txheem qhuav yog zom cov khoom xyaw ua ke thiab tom qab ntawd hlawv nws los ntawm qhov cub tawg lossis qhov cub tom qab nias pob los yog compact. Cov txheej txheem ntub dej yog zom cov khoom sib xyaw rau hauv slurry nrog dej, ces nias thiab lim kom lub cev qhuav dej rau hauv cov ncuav mog qab zib, thiab nqus cov av nkos rau hauv cov av nkos los yog av nkos thiab tom qab ntawd hlawv.
Txoj kev siv hluav taws xob melting yog ntxiv cov khoom siv sib xyaw rau hauv qhov cub hluav taws xob, yaj hauv qhov kub siab uas tsim los ntawm arc, txias crystallization, kev siv cov khoom xyaw ntuj raw khoom (xws li bauxite, thiab lwm yam) tuaj yeem crushed ncaj qha rau.<1.5mm particles without grinding, and then mixed with other powdered raw materials in the mixer.
Synthesis ntawm mullite los ntawm sintering feem ntau yog nqa tawm ntawm 1650 ~ 1700 degree. Lub ntsiab yam tseem ceeb cuam tshuam rau cov synthesis ntawm mullite los ntawm sintering yog purity ntawm raw khoom, fineness ntawm raw khoom thiab calcination kub. Lub synthesis ntawm mullite los ntawm sintering txoj kev tsuas yog nyob ntawm Al? O? Cov tshuaj tiv thaiv theem ntawm SiO2 thiab sio2 tau ua tiav, yog li kev txhim kho cov khoom tawg ntawm cov khoom siv raw yuav ua kom cov txheej txheem ntawm cov tshuaj tiv thaiv theem. Hauv particular, cov khoom<8μm have a great effect on the formation and sintering of synthetic mullite. It can be seen that the full mixing and fine grinding of raw materials is an important process condition to promote the solid phase of the synthesis of mullite. Mullite generally begins to form at 1200 ° C and ends at 1650 ° C. At this time, it is microcrystalline, and the crystallization develops well when the temperature exceeds 1700℃. It can be seen that the combustion temperature directly affects the formation and crystal development of mullite. Therefore, heating to a certain firing temperature and extending a certain holding time are necessary conditions for the synthesis of mullite. The purity of the raw materials used to synthesize mullite is very strict, and a small amount of impurities will reduce the content of mullite. In industrial production, it is inevitable to bring a variety of impurities, mainly Fe? O? TiO? , CaO, MgO, Na? O·K? O, the most harmful of which is Na? O, K? O, they inhibit the formation of mullite and lead to the production of a large number of silicon-rich glass phases, reducing mullite content. Fe? O? It will slow down the mullite process and increase the amount of glass phase. Be TiO? When a small amount of Ti ions exist, part of Ti ions enter the mullite lattice to form a solid solution, promoting the formation of mullite and crystal development and growth, when the TiO2 content is too high, it still acts as a flux.
Electromelting mullite yog npaj los ntawm melting lub compound nyob rau hauv ib tug hluav taws xob arc rauv, thiab lub mullite yog txias tawm ntawm lub yaj. Cov txheej txheem crystallization zoo ib yam li Al? O? -SiO? Cov txheej txheem crystallization ntawm qhov system theem daim duab zoo ib yam. Thaum twg Al? O? Thaum lub theoretical muaj pes tsawg leeg ntawm mullite siab tshaj 71.8%, yaj tshaj Al yog tsim. O? Kev daws teeb meem ntawm mullite, beta-mullite, tsuas yog Al? O? Cov theem corundum tsuas yog tshwm sim ntawm 80%. Cov ntxhia theem muaj pes tsawg leeg ntawm fused mullite feem ntau yog mullite siv lead ua thiab iav theem. Tuam Tshoj hluav taws xob yaj mullite kev lag luam tus qauv YB/T104-2004 "Electric yaj mullite" cov khoom hluav taws xob yaj mullite raws li Al? O? Cov ntsiab lus tau muab faib ua DM-1 thiab DM-2 qib, thiab cov xwm txheej cuam tshuam tuaj yeem pom nyob rau hauv cov qauv sib xws hauv tebchaws. Piv nrog rau sintered mullite, fused mullite muaju tau tsim zoo nrog cov nplej loj thiab tsawg dua qhov tsis xws luag, thiab cov siv lead ua loj yog ntau pua zaus ntawm sintered mullite, yog li qhov kub thiab txias cov cuab yeej thiab kev yaig kuj yog qhov zoo.
