1.1 Alumina Crystal Structure
Alumina muaj cov qauv sib txawv, uas tau muab faib ua ob pawg raws li kev npaj ntawm O2-: cubic structure (fcc) lossis hexagonal close-packed structure (hcp). Hauv ob pawg loj no, kev faib tawm ntxiv tuaj yeem ua raws li Al3+, ntawm cov uas (cubic), η (cubic), θ (monoclinic), thiab δ (orthorhombic) cov qauv yog raws li fcc lattice, thaum (trigonal), κ (orthorhombic), thiab χ (hexagonal).
Lub -Al2O3 siv lead ua qauv muaj O2- txheej txheem nyob rau hauv hexagonal ze- cov qauv ntim, nrog rau seem seem tsim octahedral interstitial qhov chaw, thiab Al3+ sau 2/3 ntawm qhov chaw interstitial, yog li xyuas kom meej tias cov tshuaj formula ntawm alumina yog -Al2O3. Lub hauv paus ntsiab lus ntawm Al 3+ nyob rau hauv octahedral interstitial sites txaus siab rau Pauling txoj cai, uas yog, qhov kev ncua deb ntawm Al3+ nyob rau hauv tib txheej thiab nruab nrab ntawm txheej yuav tsum tau khaws cia kom deb li deb li sai tau [1].
-Al2O3 tau muab faib ua flake-zoo li -Al2O3 thiab spherical -Al2O3. Flake-zoo li -Al2O3 nthuav tawm ob- qauv qauv dav dav hauv qhov chaw, nrog cov tuab me me thiab txoj kab uas hla loj- rau- tuab piv. Nws feem ntau yog npaj los ntawm peb txoj kev: ntub chemistry, khoom - xeev cov tshuaj tiv thaiv, thiab molten ntsev txoj kev. Tus kheej kheej -Al2O3 qauv yog tsim nyob rau hauv peb- qhov chaw seem, thiab nws txoj kev loj hlob nyob rau hauv ob-dimensional kev taw qhia yuav tsum tau suppressed thaum lub sij hawm npaj, yog li cov txheej txheem xws li homogeneous nag lossis daus, hydrothermal txoj kev, drip ball method, template method, spraying method, and plasma electrolysis is mainly. Spherical -Al2O3 yog qhov nyuaj dua los npaj.
Lub -Al2O3 siv lead ua qauv yog tus yam ntxwv los ntawm lub cubic kaw ntim ntawm O2-, yog li tsim cov qauv octahedral. Cov qauv no txuas ntxiv hloov mus rau hauv cov qauv spinel, nyob rau hauv uas 32 cubic kaw-packed O atoms ua lub tsev cell. Hauv cov qauv spinel, 32 O atoms tsim 8 tetrahedral voids thiab 16 octahedral voids, nyob rau hauv uas 67/3 txhuas atoms yog randomly faib nyob rau hauv lub voids, thaum 8/3 vacancy muaj nyob [2].
Tus yam ntxwv ntawm -Al2O3 siv lead ua qauv nyob rau hauv nws qhov chaw siab tshwj xeeb thiab cov chaw ua haujlwm dav dav. Ntawm qhov kub thiab txias catalytic, cov khoom no nthuav tawm kev ruaj ntseg zoo. Yog li ntawd, -Al2O3 catalysts muaj dav daim ntawv thov kev cia siab nyob rau hauv kev lag luam thiab kev tshawb fawb kev tshawb fawb vim lawv siab xaiv.
-Al2O3 yog cov siv lead ua ruaj khov tshaj plaws ntawm alumina, thiab lwm cov ntaub ntawv siv lead ua tsis ruaj khov thiab hu ua cov theem hloov pauv. Cov theem kev hloov pauv no thaum kawg yuav hloov mus rau qhov ruaj khov -Al2O3 qauv nyob rau hauv qee yam xwm txheej, yog li -Al2O3 kuj yog theem kawg ntawm kev hloov pauv ntawm alumina. Yog li ntawd, tsuas yog -Al2O3 muaj nyob rau hauv qhov, nyob rau hauv daim ntawv ntawm tej yam ntuj tso minerals xws li ntuj corundum, ruby, thiab sapphire. Cov qauv no tseem hu ua corundum siv lead ua qauv [3-4].
1.2 Alumina Ceramics
Alumina ceramics yog cov khoom siv ua haujlwm siab -cov khoom siv ceramic. Vim lawv lub cev thiab tshuaj lom neeg zoo heev, lawv tau siv dav hauv qhov chaw hnyav xws li kub, siab zog, hnav tsis kam, thiab rwb thaiv tsev siab. Lawv cov keeb kwm kev loj hlob tuaj yeem taug qab mus rau qhov kawg ntawm xyoo pua 19th. Vim lawv lub zog siab thiab nruj, alumina ceramics yog ib qho ntawm cov oxide ceramics nrov tshaj plaws. Nyob rau tib lub sijhawm, vim lawv cov khoom siv hluav taws xob, hluav taws xob, thiab kho qhov muag, alumina ceramics tau siv nyob rau hauv ntau qhov kev lag luam niaj hnub no.
Alumina ceramics muaj siab hardness, nrog Rockwell hardness ntawm HRA80-90, uas yog thib ob tsuas yog pob zeb diamond. Qhov hnav tsis kam ntawm alumina ceramics yog sib npaug rau 266 npaug ntawm manganese hlau thiab 171.5 npaug ntawm siab -chromium cam khwb cia hlau. Raws li tib yam kev ua haujlwm, nws tuaj yeem txuas ntxiv lub neej kev pabcuam ntawm cov khoom siv tsawg kawg kaum zaug. Qhov ceev ntawm alumina ceramic khoom yog 3.7 ~ 3.95 g / cm³, tsuas yog ib nrab ntawm cov hlau, uas tuaj yeem txo cov khoom siv thauj khoom zoo heev. Nyob rau tib lub sijhawm, nws kuj muaj qhov zoo xws li thermal conductivity, zoo resistivity thiab thermal stability, thiab me me dielectric tas li. Nws yog cov khoom siv rau lub cim tshiab ntawm microelectronic cov cuab yeej thiab cov tshuab thiab tau dhau los ua cov khoom tseem ceeb rau cov khoom siv hluav taws xob hauv thaj chaw xws li aerospace, 5G kev sib txuas lus, siab - fais fab semiconductors, thiab high-power LED teeb [5].
High-purity ultrafine alumina hmoov npaj tshuab yog ib qho tseem ceeb ntawm kev txwv txoj kev loj hlob sai ntawm cov khoom siv alumina ceramic tshwj xeeb thiab tseem yog qhov txuas tseem ceeb hauv kev txo nqi thiab nce kev ua haujlwm hauv kev tsim khoom. Kev tsim kho cov txheej txheem tshiab rau kev npaj siab -cov hmoov ceramic zoo yog qhov tseem ceeb rau kev tsim cov ntaub ntawv ceramic thiab lwm yam high-tech fields.
2
Alumina hmoov Npaj Technology
2.1 Kev faib tawm ntawm Alumina Precursors
Kev npaj ntawm alumina feem ntau cuam tshuam nrog thermal decomposition ntawm alumina hydrates, uas yog precipitated los ntawm cov kev daws teeb meem uas muaj Al{0}} ions los yog organometallic compounds. Cov kev tshawb fawb tau pom tias cov txheej txheem hloov dua siab tshiab no (xws li lub cev qhuav dej ntawm boehmite rau -Al2O3) yog cov tshuaj tiv thaiv topotactic, tso cai rau lub microscopic morphology ntawm lub precursor khaws cia hauv alumina. Yog li ntawd, cov yam ntxwv ntawm alumina yog ze ze rau lub hydrate precursor.
Raws li qhov sib txawv ntawm cov qauv thiab cov ntsiab lus dej, alumina precursors feem ntau suav nrog gibbsite, bayerite, nordstrandite, thiab diaspore, ntawm cov diaspore ntxiv muab faib ua diaspore thiab boehmite. Gibbsite yog cov khoom tseem ceeb ntawm bauxite nyob rau hauv cov cheeb tsam sov. Raws li cov khoom kawg ntawm kev lag luam Bayer txheej txheem, nws yog tsim nyob rau hauv loj scale los ntawm alkaline nag lossis daus ntawm Al3+ thiab yog dav siv raws li ib tug nplaim hluav taws, additive rau polymers thiab ntawv, tshuaj txhuam hniav muab tub lim, thiab stabilizer rau titanium dioxide. Cov qauv siv lead ua ntawm gibbsite belongs rau lub monoclinic system, nrog txhuas -oxygen octahedra txuas los ntawm cov npoo los ua cov txheej txheem txheej, thiab cov txheej txheem ntawm ob - txheej stacking tuaj yeem qhia tau tias yog AB BA AB BA.... Boehmite, tseem hu ua pseudo-boehmite. Nws tuaj yeem ua ke hydrothermally siv gibbsite raws li cov khoom siv raw, los yog tau los ntawm kev tswj roasting ntawm bayerite. Boehmite belongs rau lub orthorhombic system, nrog txhuas -oxygen octahedra txuas los ntawm cov npoo thiab txheej txheem nyob rau hauv ib tug stepped, thiab nws cov txheej yog txuas nrog hydrogen bonds. Nyob rau hauv lub octahedral qauv, oxygen atoms yog teem raws li ABC ABC ....
Ntawm ntau yam aluminium hydroxide precursors, pseudo-boehmite yog ib hom hydrate nrog crystallinity tsawg. Nws yog tus cwj pwm los ntawm qhov tshwj xeeb ntawm thaj chaw, ntau qhov pores, qhov zoo ntawm qhov chaw, yooj yim dispersion hauv dej thiab hydroxyl- muaj cov kuab tshuaj, thiab cov gel solubility zoo nyob rau hauv acidic tej yam kev mob. Cov yam ntxwv no ua rau pseudo-boehmite dav siv los ua catalyst carrier thiab binder, thiab nws kuj yog ib qho tseem ceeb ntawm cov khoom nruab nrab rau kev tsim cov alumina activated [6].
2.2 Alumina Powder Txoj Kev Npaj
2.2.1 Gas Phase Method
Cov roj theem txoj kev ncaj qha siv cov pa roj los yog vaporizes reactants los ntawm cov cua kub sib txawv, ua rau cov tshuaj tiv thaiv physicochemical tshwm sim hauv lub xeev gaseous, thiab thaum kawg condensing los tsim ultrafine hmoov. Hom qauv no muaj cov tshuaj tiv thaiv me me, tswj tau yooj yim ntawm agglomeration, zoo particle dispersibility, me me particle loj, thiab nqaim faib; qhov tsis zoo yog qhov tsis tshua muaj txiaj ntsig, thiab cov nqi tsim khoom yog qhov nyuaj los tswj.
Hauv cov txheej txheem roj, cov khoom siv raw yuav tsum tau ua kom vaporized ua ntej cov tshuaj tiv thaiv, uas siv ntau lub zog, thiab cov tshuaj tiv thaiv yuav tsum muaj ntau cov roj inert nrog cov av qis heev, uas ua rau tus nqi qis rau cov roj theem txoj kev.
Chemical vapor deposition (CVD) yog ib txoj hauv kev siv roj ntau rau kev npaj nano-alumina. Txoj kev no siv aluminium chloride thiab dej vapor rau hauv cov tshuaj tiv thaiv chamber los tsim cov alumina nanopowder. Cov txheej txheem CVD feem ntau suav nrog nplaim CVD, laser pyrolysis CVD, thiab lwm yam. Han Shizhong et al. [7] npaj siab-purity alumina hmoov nrog qhov nruab nrab particle loj ntawm 5.6 nm los ntawm cov ntshav organometallic CVD, reacting nyob rau hauv ib puag ncig oxygen ntawm 1000℃thiab 5.3 kPa kom tau spherical nano{10}}alumina hmoov.
2.2.2 Liquid Phase Method
Cov txheej txheem ua kua theem yuav cuam tshuam cov ntsev txhuas hauv cov kuab tshuaj, sib cais cov kuab tshuaj thiab cov kuab tshuaj los ntawm evaporation, sublimation, ntxiv cov precipitant, hydrolysis, thiab lwm txoj hauv kev kom tau txais cov khoom ntawm qee yam duab thiab qhov loj me, uas yog, npaj lub precursor ntawm Al2O3 hmoov, thiab thaum kawg cua sov thiab decomposing lub precursor.
Ua ntej, cov khoom txhuas muaj nyob rau hauv cov tshuaj hauv daim ntawv ionic thiab tuaj yeem yaj hauv cov kuab tshuaj los yog cov kuab tshuaj organic xws li trichloromethyl, ethanol, thiab toluene los ntawm txhuas ntsev xws li txhuas sulfate, aluminium sec-butoxide, thiab sodium metaaluminate. Tom qab ntawd, cov txhuas ions tuaj yeem muab tso rau hauv daim ntawv ntawm covalent oxides los ntawm txoj kev xws li hydrolysis thiab evaporation ntawm txhuas ntsev, los yog siv precipitants xws li ammonium carbonate, sodium hydroxide, urea, thiab sulfuric acid. Thaum kawg, cov precipitate yog ntxuav thiab qhuav los yog calcined ntawm qhov kub thiab txias kom tau txais alumina crystal daim ntawv [8-9].
Txau Pyrolysis Technology
Spray pyrolysis thev naus laus zis, tseem hu ua nplaim hluav taws xob pyrolysis thev naus laus zis, yog ib txoj hauv kev los npaj ultrafine alumina hmoov raws li ultrasonically generated micron -sized aerosol droplets uas yog rhuab thiab decomposed ntawm 400℃~ 800℃. Laine et al. [10] ua tiav purified multiphase alumina hmoov siv tshuaj tsuag pyrolysis thev naus laus zis, tau txais siab -purity nano- alumina hmoov nrog ib qho me me ntawm 50 nm ~ 80 nm thiab - theem purity ntawm 50% ~ 85%.
Txoj kev Alkoxide Hydrolysis
Txoj kev alkoxide hydrolysis yuav npaj cov tshuaj los ntawm cov dej uas tsim nyog -soluble aluminium ntsev raws li stoichiometric proportions, ces xaiv ib tug precipitant uas muaj peev xwm react nrog hlau ions los ua ib tug precipitate, thiab thaum kawg cua sov thiab dehydrating lub precipitate kom tau ultrafine hmoov [11]. Cov txheej txheem alkoxide hydrolysis muaj xws li sulfur-emission-dawb txhuas ammonium sulfate txoj kev thiab txoj kev txhuas ammonium carbonate, thiab lwm yam. [12-13].
Zhong Lianyun et al. [14] siv analytically ntshiab txhuas nitrate thiab ammonium bicarbonate ua cov ntaub ntawv tseem ceeb los npaj nano-Al2O3 hmoov los ntawm co- txoj kev los nag. Qhov nruab nrab particle loj ntawm cov nano npaj tau -Al2O3 hmoov yog 20 nm ~ 30 nm. Ntxiv cov surfactant PEG6000 txhim kho qhov ua tau zoo ntawm kev tawg ntawm -Al2O3 hmoov.
Txhim kho Bayer txheej txheem
Cov txheej txheem Bayer siv cov kev hloov pauv hauv kev solubility ntawm aluminium oxide nyob rau hauv alkaline tov, siv concentrated sodium hydroxide tov los hloov aluminium hydroxide mus rau sodium aluminate, ces sib cais cov insoluble tshuaj los ntawm nag lossis daus, thiab thaum kawg re-precipitating aluminium hydroxide los ntawm dilution thiab ntxiv ntawm txhuas hydroxide noob crystals, thiab tom qab ntawd los ntawm dehydroasting hmoov.
Nyob rau hauv xyoo tas los no, los ntawm kev ua kom zoo dua qub ntawm cov txheej txheem Bayer, cov txheej txheem tshiab uas muaj peev xwm ua kom muaj txiaj ntsig zoo tau raug tsim [15]. Txoj kev txhim kho Bayer feem ntau txhim kho kev npaj ntawm sodium hydroxide thiab tshem tawm sodium, ua desilication thiab tshem tawm hlau ntawm sodium aluminate, thiab tswj cov txheej txheem decomposition kom tau siab -purity aluminium hydroxide. Thaum lub sijhawm txheej txheem no, aluminium hydroxide precipitates maj mam, txo qhov tshwm sim ntawm cov crystal nuclei txawv txav thiab tseem txo cov kev koom ua ke ntawm sodium thiab silicon impurities. Thaum kawg, siab -purity alumina yog tau los ntawm siab -kub calcination thiab sib tsoo.
Sol-Gel Method
Txoj kev sol-gel yog ib txoj hauv kev yooj yim thiab siv tau zoo rau kev sib xyaw nano-alumina. Tsis zoo li txoj kev nag lossis daus, uas pib hloov mus rau sol thiab gel, txhuas ntsev thiab siab -purity amine los yog ammonium ntsev daws tau txais hydrolysis los yog polymerization los ua ib tug precursor gel, uas yog cawv- ntxuav, laus, thiab thaum kawg calcined kom tau alumina hmoov.
Qee cov kws tshawb fawb kuj tau txhim kho kev txhim kho raws li cov txheej txheem sol-gel. Piv txwv li, Zhu Zuoyuan [16] tau txais cov txheej txheem hybrid ntawm hlau alkoxide hydrolysis thiab sol-gel txoj kev los npaj siab -purity ultrafine alumina hmoov. Ua ntej, txhuas hmoov nrog purity Ntau dua los yog sib npaug rau 2N tau rhuab los ua cov tshuaj txhuas alkoxide, insoluble particulate impurities raug tshem tawm los ntawm microfiltration, thiab tom qab kev laus, hydrolysis tau nqa tawm. Cov gel qhuav tau txais los ntawm distillation, thiab thaum kawg siab -purity alumina hmoov tau los ntawm siab -kub calcination.
Txoj kev Aluminium Alkoxide
Txoj kev aluminium alkoxide belongs rau thev naus laus zis iteration ntawm alkoxide hydrolysis txoj kev. Nws koom nrog ntxiv cov hlau txhuas flakes rau isopropanol tov rau cov tshuaj tiv thaiv los tsim cov txhuas isopropoxide, tom qab ntawd hydrolyzing aluminium isopropoxide los tsim cov hydrated alumina, thiab tom qab cov kauj ruam xws li kev laus, pom, ziab, thiab lub cev qhuav dej, thaum kawg tau txais alumina hmoov nrog kev ua haujlwm siab sintering.
Yang Conglin et al. [17] siv hlau txhuas thiab carbon cawv ua raw khoom los ua ke siab -purity aluminium alkoxide, thiab npaj hydrated alumina los ntawm alkoxide hydrolysis, tshem tawm cov txheej txheem nqus distillation nrog cov cuab yeej siv siab, thiab thaum kawg tau 5N-qib siab-purity ultrafine alumina hmoov ntau dua 9% purcination, ntau dua 9% hmoov los yog 9% cality. thiab particle loj ntawm 0.1 µm ~ 0.3 µm. Alumina hmoov npaj los ntawm txoj kev no muaj siab purity, thiab cov txheej txheem kev npaj yog yooj yim nrog muaj zog controllability ntawm cov khoom.
2.2.3 Txheej Txheej Txheej Txheej
Cov txheej txheem txheej txheem yog ib txoj hauv kev uas ob lossis ntau dua cov hmoov sib tov thiab ncaj qha cuam tshuam nyob rau hauv qee qhov kub thiab cua kom tsim tau nano-alumina.
Mechanical Crushing Method
Cov txheej txheem crushing siv ntau yam ultrafine crushers (siab- lub zog pob zeb, lub ntiaj teb pob zeb, ntauwd mills, dav hlau mills, thiab lwm yam). Ntawm lawv, siab - lub zog pob zeb tau siv dav. Lawv mechanically crushed alumina hmoov nyob rau hauv dej los yog cawv media los npaj siab -purity ultrafine alumina hmoov. Los ntawm kev vibration thiab kev sib hloov ntawm lub pob zeb, lub zog yog muab rau cov khoom siv raw, ua rau cov ntaub ntawv raw muaj kev cuam tshuam los ntawm cov pob tawv tawv, crushed rau hauv cov khoom zoo, los yog ua kom muaj kev cuam tshuam cov tshuaj lom neeg, yog li npaj cov hmoov ultrafine.
Txoj Kev Detonation
Txoj kev detonation kuj tseem siv tau los ua ib qho khoom siv -theem txheej txheem los npaj alumina hmoov. Txoj kev no ua cov tshuaj tiv thaiv combustion hauv qhov tsis tu ncua - ntim cov hlab ntsha thiab tsim cov roj ntau ntau. Yog li ntawd, cov tshuaj tiv thaiv tam sim no feem ntau tshwm sim nyob rau hauv kev kub siab, suppressing lub saturated vapor siab ntawm cov reactants thiab nce lub sij hawm hloov kub nyob rau hauv ib txwm siab, uas yog conducive mus rau lub ruaj khov tsim ntawm ib zaug xwb -theem metastable alumina hmoov. Txoj kev detonation muaj qhov yuav tsum tau ua rau cov khoom siv ntau lawm, kev tswj cov txheej txheem tsim khoom nyuaj, tsis tshua muaj txiaj ntsig, thiab tus nqi tsim khoom kuj siab.
Peng et al. [18] tau txais cov txiaj ntsig sib txawv los ntawm kev tswj cov pH tus nqi ntawm glycine- txhuas nitrate system. Cov txiaj ntsig tau pom tias ib puag ncig alkaline tuaj yeem tswj tau cov qoob loo loj, txo qhov kev faib ua feem ntawm amorphous theem, thiab nce qhov chaw tshwj xeeb, thaum agglomeration ntawm txawv degrees tshwm sim hauv ib puag ncig nrog pH tsawg dua lossis sib npaug li 6.
3
Cov ntsiab lus
High-purity ultrafine alumina hmoov, vim nws cov khoom siv lub cev thiab tshuaj lom neeg siab heev, tau nthuav dav heev rau daim ntawv thov scenarios ntawm alumina hmoov thiab yog ib qho tseem ceeb raw khoom nyob rau hauv niaj hnub advanced manufacturing. Tam sim no, txoj kev tsim khoom tseem ceeb ntawm siab -purity ultrafine alumina hmoov nyob rau hauv Suav teb muaj qhov tsis zoo xws li cov txheej txheem nyuaj, kev tswj tsis tau yooj yim, tus nqi siab, thiab muaj kuab paug loj. Nrog rau kev txhim kho txuas ntxiv ntawm Tuam Tshoj txoj kev lag luam, qhov kev thov rau siab -purity ultrafine alumina yuav nce ntxiv, thiab cov kev xav tau yav tom ntej rau cov cuab yeej precision, kev npaj, kev tswj technology, kev txuag hluav taws xob, thiab kev tiv thaiv ib puag ncig kuj tseem yuav siab dua thiab siab dua.