Alumina

Aluminium oxide tshwm sim nyob rau hauv ib puag ncig ntuj nyob rau hauv daim ntawv ntawm cov pa alumina, nws tshuaj mis - AL2O3. Nyob rau hauv no hom ntawm muaju twb tsis muaj xim uas muaj nyob rau ntawm lub ib tug kub ntawm 2044 ° C pib rau yaj, thiab thaum twg lub theem ntawm 3530 ° C haus.

Nyob rau hauv tej yam ntuj tso ncig tsuas ruaj khov kev hloov kho yam khoom uas txhuas oxide muaj ib tug ntom ntawm 3.99 g / cm3. Qhov no yog ib tug heev khoom qauv teej tug mus rau lub cuaj theem ntawm Mohs rooj. Tus nqi ntawm cov refractive index yog raws li nram no: rau cov zoo tib yam duab tshav - 1.765 thiab 1.759 rau lub extraordinary. Nyob rau hauv tej yam ntuj tso ncig Alumina feem ntau muaj ntau yam hlau oxides, txawm li cas los, cov mineral Corundum yuav tau sib txawv ntxoov nws cov xim. Piv txwv li, yog cov neeg sapphires, rubies thiab lwm yam precious pob zeb. Raws li xws li, lub alumina yuav npaj thiab laboratory-tshuaj qauv. Rau lub hom phiaj no, A12O3 metastable daim ntawv thiab lawv decomposed thermally. Tsis tas li ntawd, raws li qhov uas txoj kev kuaj txoj kev siv txhuas oxide , txhuas hydroxide.

Standard kev hloov kho compound yog tetragonicheskuyu lattice muaj nyob rau hauv nws muaj pes tsawg leeg txog 1-2% dej. Yuav tau amorphous nyob rau hauv cov qauv alumina - alumina gel, uas gelevidny tshuaj ntawm AL (OH) 3 yog dewatered kom tau ib tug ntxeem tau cov ntaub ntawv uas cov pob tshab loj.

Aluminium oxide yog kiag li insoluble nyob rau hauv dej, tiam sis yuav tsum zoo yaj nyob rau hauv cryolite, rhuab mus rau ib tug kub. Amphoteric substance. Characteristically xws li ib tug vaj tse ntawm lub tsim alumina li cov ntxeev dependence ntawm nws tsim kub thiab tshuaj ua si. Raws li dag (i.e., tau nyob ib tug kub ntawm tshaj 1200 ° C) thiab tej yam ntuj tso Corundum nyob rau hauv ib tug dog dig puag ncig sau zoo ib puas feem pua tiav tshuaj inertness thiab tsis muaj kev hygroscopicity.

Oxide txhuas tshuaj zog pib muaj kev koom ib ce muaj zog ntawm kub nyob ib ncig ntawm 1000 ° C, thaum nws pib mus sai heev nrog tshuaj xws li ntau yam alkali carbonates ntawm alkali hlau. Thaum zoo li no sis aluminates raug tsim. Lub qeeb qeeb compound reacts nrog SiO2, raws li zoo raws li ntau hom acidic slags. Raws li ib tug tshwm sim ntawm cov kev sib tshuam yog tau aluminosilicates.

Alumina gel thiab alumina uas yog npaj los ntawm calcination ntawm txhuas hydroxides thaum twg muaj tsawg kawg yog 550 ° C, muaj ib tug heev hygroscopicity, yav tom ntej nkag mus rau hauv tshuaj tshua thiab nquag nrog acidic thiab alkaline daws teeb meem.

Feem ntau, raws li ib tug raw khoom rau cov txhuas oxide yog siv bauxite, alunite thiab nepheline. Thaum cov ntsiab lus ntawm cov tshuaj yeeb dej caw nyob rau hauv lo lus nug nyob rau hauv lawv ntau tshaj li 6-7% lawm yog lub ntsiab txoj kev - los ntawm Bayer, thiab nyob ib sab cov ntsiab lus ntawm kev siv ore sintering txoj kev nrog txiv qaub los yog dej qab zib. Bayer txheej txheem yog ib ua crushed pob zeb nyob rau hauv lub pob mills, ua raws li bauxite yog kho nrog alkaline daws teeb meem ntawm ib tug kub ntawm 225-250 ° C. Muaj pes tsawg leeg li tau twb diluted nrog aqueous sodium aluminate tov thiab lim. Nyob rau hauv tus txheej txheem ntawm filtering ib tug slurry uas muaj alumina, uas nws cov khoom sib haum mus rau tus txheej txheem, yog decomposed nyob rau hauv centrifuges. Tej technology tso cai rau kom muab tau 50% tawm los ntawm lub substance. Tsis tas li ntawd, siv ntawm no txoj kev ua rau nws ua tau rau kom cov niam dej cawv rau siv nyob rau hauv tom ntej hauj lwm los ntawm leaching ntawm bauxite.

Feem ntau, lub resulting hluavtaws txoj kev txhuas oxide yog siv raws li lub intermediate cov khoom siv rau qhov kev npaj ntawm ntshiab txhuas. Nyob rau hauv kev lag luam, nws yog siv raws li ib tug raw khoom rau cov refractory cov ntaub ntawv, tej hub abrasive thiab txiav cov cuab yeej. Niaj hnub nimno technology nquag thov ib muaju ntawm txhuas oxide nyob rau hauv cov sij hawm, PCB, hniav nyiaj hniav kub.