corundum yog dab tsi?

Corundum (Al2O3) muaj ntau cov khoom siv raw, suav txog li 25% ntawm qhov hnyav ntawm lub ntiaj teb crust. Nws yog pheej yig thiab muaj ntau yam zoo heev. Muaj ntau ntau cov crystals sib txawv ntawm Al2O3, thiab muaj ntau tshaj kaum hom variants qhia, tab sis muaj peb lub ntsiab, xws li α-Al2O3, β-Al2O3, thiab γ-Al2O3.

Tabular corundum

γ-Al2O3 yog cov qauv spinel, uas tsis ruaj khov ntawm qhov kub thiab txias thiab tsis tshua siv los ua ib qho khoom siv. β-Al2O3 yog ib qho tseem ceeb ntawm aluminate uas muaj alkali hlau lossis alkaline ntiaj teb hlau. Nws cov tshuaj muaj pes tsawg leeg tuaj yeem kwv yees los ntawm RO·6Al2O3 thiab R2O·11Al2O3, hexagonal lattice, ntom 3.30 ~ 3.63g / cm3, 1400 ~ 1500 Nws pib decompose ntawm ℃ thiab hloov mus rau α-Al2O3 ntawm 1600 ℃. α-Al2O3 yog daim ntawv kub kub, nrog rau qhov kub thiab txias kom siab li qhov melting point, thiab qhov ntom ntawm 3.96 ~ 4.01g / cm3, uas muaj feem xyuam rau cov ntsiab lus impurity. Chav tsev cell yog ib tug ntse prism, uas muaj nyob rau hauv daim ntawv ntawm ntuj corundum, ruby thiab sapphire nyob rau hauv cov xwm. α-Al2O3 muaj cov qauv kev cog lus, kev ua haujlwm qis, cov khoom siv hluav taws xob zoo, thiab cov khoom siv zoo heev. Mohs hardness yog 9. α-Al2O3 belongs rau hexagonal siv lead ua system, corundum qauv, a = 4.76, c = 12.99.

Al2O3 muaj zog txhua yam. Lub purer lub Al2O3 muaj pes tsawg leeg, lub zog ntau dua. Lub zog txhua yam tuaj yeem siv los ua cov cuab yeej plooj (porcelain) thiab lwm yam khoom siv tshuab. Lub resistivity ntawm Al2O3 yog siab, hluav taws xob rwb thaiv tsev kev ua tau zoo, lub resistivity ntawm chav tsev kub yog 1015Ω·cm, thiab lub zog dielectric yog 15kV / mm. Siv nws cov rwb thaiv tsev thiab lub zog, nws tuaj yeem ua rau hauv cov substrates, lub qhov (socket), lub txim hluav taws xob, lub plhaub hluav taws xob, thiab lwm yam. Al2O3 muaj hardness siab, Mohs hardness ntawm 9, ntxiv rau zoo heev hnav tsis kam, yog li nws yog dav siv los tsim cov cuab yeej, sib tsoo log, abrasives, kos duab tuag, bearings, bearings bushes thiab dag gems. Al2O3 muaj lub siab melting point thiab corrosion kuj. Nws muaj qhov melting point ntawm 2050 ° C. Nws muaj kev tiv thaiv zoo rau kev yaig ntawm cov hlau molten xws li Be, Sr, Ni, Al, V, Ti, Mn, Fe, CO thiab sodium hydroxide, iav, thiab slag. Nws kuj muaj kev ua haujlwm siab; Nws tsis cuam tshuam nrog Si, P, Sb, Bi nyob rau hauv ib qho chaw inert, yog li nws tuaj yeem siv los ua cov khoom siv refractory, cov raj rauv, iav kos duab crucibles, hollow pob, fibers thiab thermocouple tiv thaiv npog, thiab lwm yam.

Al2O3 muaj tshuaj lom neeg ruaj khov zoo heev. Ntau cov sulfides, phosphides, arsenides, chlorides, nitrides, bromides, iodides, qhuav fluorides, sulfuric acid, hydrochloric acid, nitric acid, thiab hydrofluoric acid tsis cuam tshuam nrog Al2O3. Yog li ntawd, nws tuaj yeem ua rau cov hlau ntshiab thiab ib leeg siv lead ua kev loj hlob crucibles, tib neeg cov pob qij txha, pob txha pob txha, thiab lwm yam. Al2O3 muaj cov khoom siv kho qhov muag thiab tuaj yeem ua rau cov khoom siv hluav taws xob xa mus ua Na vapor teeb raj, microwave fairings, infrared windows thiab laser. oscillation Cheebtsam. Lub ionic conductivity ntawm Al2O3 yog siv los ua cov khoom siv rau hnub ci hlwb thiab cov roj teeb cia. Al2O3 kuj feem ntau siv hauv ceramic nto metallization tshuab.

Lub ntsiab crystalline theem ntawm alumina-based fused corundum yog corundum theem nrog qhov loj ntawm 1.0-1.5mm thiab interlaced crystals. Cov seem yog cov kab ntawm rutile, alumina thiab aluminium titanate, thiab nyob rau hauv lub corundum theem los yog nruab nrab ntawm cov siv lead ua theem. Ib qho me me ntawm iav theem. Hauv Suav teb, tom qab ntau tshaj kaum xyoo ntawm kev siv zog tsis tu ncua, cov txheej txheem smelting ntawm bauxite-based fused corundum tau ua tiav zoo, nrog rau txhua xyoo muaj peev xwm ntau dua 110,000 tons. Bauxite-based fused corundum tau ua tiav siv los ua cov khoom siv raw rau ntau yam cib raug rho tawm haujlwm thiab cov ntaub ntawv tsis zoo li refractory. Piv txwv li, nws tuaj yeem hloov pauv qhov ntom ntom corundum nyob rau hauv qhov cub tawg castables, thiab siv los ua cov khoom siv matrix thiab cov khoom siv granular los tsim cov creep tsawg. High alumina bricks yog siv los hloov dawb corundum nyob rau hauv lwm yam Al2O3-SiO2 refractories los npaj cov khoom ua tau zoo.

Brown corundum smelting yog raws li lub hauv paus ntsiab lus uas txhuas muaj ib tug ntau affinity rau oxygen tshaj hlau, silicon, titanium, thiab lwm yam. Los ntawm kev tswj tus nqi ntawm cov txo tus neeg sawv cev, lub ntsiab impurities nyob rau hauv bauxite yog txo los ntawm txo smelting, thiab txo impurities daim ntawv. ferrosilicon alloys. Nws yog cais los ntawm corundum yaj kom tau cov xim av corundum nrog cov siv lead ua zoo raws li qhov yuav tsum tau ua thiab Al2O3 cov ntsiab lus ntau dua 94.5%. Fe2O3 raug txo kom tsim ferrosilicon alloy thiab tshem tawm thaum lub sij hawm smelting txheej txheem, tab sis ib tug me me ntawm hlau oxide thiab alumina ua spinel tseem tshuav nyob rau hauv cov khoom. TiO2 yog ib feem txo rau hauv ferrosilicon alloy thaum lub sij hawm smelting txheej txheem, thiab ib feem ntawm nws tseem nyob rau hauv cov xim av corundum, uas yog lub ntsiab tseem ceeb ntawm cov xim ntawm cov xim av corundum. CaO thiab MgO yog qhov nyuaj los txo qis thaum lub sij hawm smelting, thiab feem ntau ntawm CaO thiab MgO nyob rau hauv cov ntaub ntawv raw tseem muaj nyob rau hauv cov khoom. Txawm hais tias Na2O thiab K2O tuaj yeem volatilize ntawm qhov kub thiab txias thaum lub sij hawm smelting, lawv tsis tuaj yeem txo thiab nyob twj ywm hauv cov xim av corundum, uas muaj kev cuam tshuam zoo rau qhov zoo.

Brown corundum

Cov khoom siv raw ntawm cov xim av corundum yog tsim los ntawm α-alumina crystal grains thiab ib qho me me ntawm cov iav theem, α-alumina crystals yog tsim los ntawm Al2O3 cov tshuaj muaj Ti2O3, thiab cov iav theem feem ntau yog tsim los ntawm titanium dioxide thiab silicon dioxide thiab lwm yam. Cov kab oxidation uas twb muaj lawm nyob rau hauv hluav taws xob arc rauv. Cov oxides no tsim cov theem iav, thiab lawv tsuas muaj cov solubility tsawg hauv cov qauv siv lead ua ntawm alumina nplej. Ti2O3 tsuas yog oxide uas Ti tuaj yeem yaj hauv cov nplej alumina. TiO2 yog cov thermodynamically ruaj khov oxide ntawm Ti. Thaum lub sij hawm smelting thiab txo cov xim av corundum, ib feem ntawm TiO2 yog txo rau sub-oxidation ntawm titanium. (Ti2O3), siab tshaj 1000 ℃, oxygen tuaj yeem xa mus rau hauv Ga-alumina nplej, oxidize Ti2O3 rau hauv TiO2 ruaj khov dua thiab tom qab ntawd qhwv rau hauv α-alumina nplej, yog li feem ntau ntawm titanium dioxide yog α-alumina Cov kua siv lead ua kua. nplej muaj.

TiO2 ntau dhau hauv cov xim av corundum tsis tuaj yeem nyob hauv lub iav theem, tab sis reacts nrog alumina los ua txhuas titanate (TiO2·Al2O3). Aluminium titanate yog theem peb ntawm kev sib tshuam ntawm α-alumina nplej thiab iav theem; Lub toughness ntawm xim av corundum nce nrog kev loj hlob ntawm TiO2 crystal nuclei. TiO2 theem sib npaug sib cais hauv α-alumina crystal grains toughens α-alumina hais. Xim av corundum cov tshuaj Ti2O3 ua rau xim av corundum tshwm xiav.

Ti2O3 tsuas yog oxide uas Ti tuaj yeem yaj hauv cov nplej alumina. TiO2 yog cov thermodynamically ruaj khov oxide ntawm Ti. Thaum lub sij hawm smelting thiab txo cov xim av corundum, ib feem ntawm TiO2 yog txo rau sub-oxidation ntawm titanium. (Ti2O3), siab tshaj 1000 ℃, oxygen tuaj yeem xa mus rau hauv Ga-alumina nplej, oxidize Ti2O3 rau hauv TiO2 ruaj khov dua thiab tom qab ntawd qhwv rau hauv α-alumina nplej, yog li feem ntau ntawm titanium dioxide yog α-alumina Cov kua siv lead ua kua. nplej muaj. TiO2 ntau dhau hauv cov xim av corundum tsis tuaj yeem nyob hauv lub iav theem, tab sis reacts nrog alumina los ua txhuas titanate (TiO2·Al2O3). Aluminium titanate yog theem peb ntawm kev sib tshuam ntawm α-alumina nplej thiab iav theem; Lub toughness ntawm xim av corundum nce nrog kev loj hlob ntawm TiO2 crystal nuclei. TiO2 theem sib npaug sib faib nyob rau hauv α-alumina crystal grains toughens α-alumina hais. Xim av corundum cov tshuaj Ti2O3 ua rau xim av corundum tshwm xiav.