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. Txoj kev qhuav yog zom cov khoom xyaw ua ke thiab tom qab ntawd hlawv lawv 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 tsim los ntawm arc, txias crystallization, siv cov khoom siv ntuj tsim (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 evenly.
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 lenite los ntawm sintering txoj kev tsuas yog nyob ntawm cov khoom theem cov tshuaj tiv thaiv ntawm Al2O3 thiab SiO2, yog li kev txhim kho cov dispersion ntawm raw cov ntaub ntawv yuav accelerate tus txheej txheem ntawm tib theem cov tshuaj tiv thaiv. 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 micro-grained, 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.
Hauv kev tsim khoom lag luam, nws tsis tuaj yeem nqa ntau yam impurities, xws li Fe2O3, TiO2, CaO, MgO, Na2O, K2O, ntawm cov uas muaj kev phom sij tshaj plaws yog Na2O thiab K2O, uas inhibit qhov tsim ntawm mullite, thiab ua rau kev tsim khoom. ntawm ib tug loj tus naj npawb ntawm silica-nplua nuj iav theem, txo cov ntsiab lus mullite. Fe2O3 slows tus txheej txheem ntawm mullite fossilization thiab nce tus naj npawb ntawm cov iav theem. Thaum muaj ib qho me me ntawm TiO2, ib feem ntawm Ti ions nkag mus rau lub cim mullite los tsim cov kev daws teeb meem, txhawb kev tsim cov mullite thiab siv lead ua kev loj hlob thiab kev loj hlob, thaum TiO2 cov ntsiab lus siab dhau lawm, nws tseem ua lub luag haujlwm ntawm flux. Electromelting mullite yog npaj los ntawm melting lub compound nyob rau hauv ib tug arc rauv thiab txias mullite los ntawm yaj. Cov txheej txheem crystallization zoo ib yam li daim duab qhia theem ntawm Al2O3-SiO2 system.
When the Al2O3 of the compound is higher than 71.8% of the theoretical group in mullite, a mullite solid solution with excess Al2O3 is formed, that is, β-mullite, and only when the Al2O3>80% yuav tshwm sim corundum theem. Cov ntxhia theem muaj pes tsawg leeg ntawm fused mullite feem ntau yog mullite siv lead ua thiab iav theem. Piv nrog rau sintered mullite, fused mullite crystals tau tsim zoo, nrog cov nplej loj thiab tsawg dua, thiab cov siv lead ua loj yog ntau pua zaus ntawm sintered mullite, yog li qhov kub thiab txias ntawm cov khoom siv thiab kev yaig kuj yog qhov zoo.

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