Yawg Zhang siv nws txoj haujlwm tag nrho ntawm Lub Tsev Kawm Ntawv Aerospace Materials Institute. Ua ntej so haujlwm, nws nyiam ua si yog coj nws cov tub ntxhais kawm mus rau lub tsev rau khoom kom paub cov khoom siv. Nws qhib lub thoob yas dawb uas tsis muaj dab tsi, khawb ib diav hmoov dawb zoo, creamy nrog ib rab diav kuaj, thiab maj mam pov nws rau hauv qab lub teeb. Cov hmoov av maj mam poob rau hauv lub teeb ci, ci ntsa iab maj mam. "Tsis txhob saib tsis taus cov hmoov dawb no," Yawg Zhang ib txwm hais, ntsia nws lub qhov muag. "Seb cov dav hlau thiab cov foob pob hluav taws uas peb tsim puas tuaj yeem tiv taus cov huab cua saum ntuj qee zaum nyob ntawm lub peev xwm ntawm 'hmoov' no. "
Cov "hmoov dawb" uas nws hais txog yogalumina hmoov. Nws suab zoo li qub - puas yog nws tsuas yog ua los ntawm bauxite xwb? Tab sis hmoov alumina siv hauv aerospace txawv kiag li ntawm alumina qib kev lag luam. Nws qhov huv yog yuav luag plaub cuaj tom qab lub cim lej; nws qhov loj me ntawm cov khoom me me yog ntsuas hauv nanometers thiab micrometers; nws cov morphology - txawm tias yog cov pob zeb, cov flakes, lossis koob - raug txiav txim siab zoo. Hauv Lao Zhang cov lus, "Qhov no yog cov khoom noj zoo uas 'ntxiv cov calcium' rau lub teb chaws cov khoom siv hnyav."
Raws li qhov khoom no ua tau hauv kev lag luam aerospace, muaj ntau yam kev siv. Cia peb pib nrog qhov "hardcore" tshaj plaws - muab cov dav hlau "armor." Dab tsi yog qhov kev ntshai tshaj plaws ntawm txhua yam uas ya saum ntuj, txawm tias nws yog lub dav hlau pej xeem lossis lub dav hlau tub rog sib ntaus sib tua? Kub heev thiab hnav thiab tsim kua muag. Cov hniav turbine cav tig ntawm qhov ceev ceev hauv cov pa roj tawm ntawm ntau txhiab degrees Celsius; cov hlau ib txwm yuav mos thiab yaj ntev dhau los. Yuav ua li cas? Cov kws ua haujlwm tau los nrog ib qho kev daws teeb meem zoo heev: txheej cov hniav nrog cov txheej ceramic tshwj xeeb. Cov khoom siv tseem ceeb ntawm cov txheej no feem ntau yog hmoov alumina.
Vim li cas ho xaiv nws? Ua ntej, nws tiv taus cua sov, nrog rau qhov chaw yaj tshaj 2000 degrees Celsius, ua rau nws yog ib qho zoo heev "ris tsho tiv thaiv cua sov." Qhov thib ob, nws tawv thiab tiv taus hnav, tiv thaiv cov hniav los ntawm kev yaig ntawm cov hmoov av hauv cov cua ceev ceev. Zoo dua, los ntawm kev kho qhov loj me ntawm cov hmoov alumina thiab ntxiv lwm yam khoom, qhov porosity, toughness, thiab lo rau cov hlau substrate ntawm lub txheej tuaj yeem tswj tau. Raws li tus neeg ua haujlwm hauv chaw ua haujlwm qub tau hais tso dag, "Nws zoo li siv ib txheej ntawm cov tshuaj pleev thaiv hnub ceramic zoo rau cov hniav turbine - nws yog ob qho tib si tiv thaiv hnub thiab tiv taus khawb." Qhov "tshuaj pleev thaiv hnub" no tseem ceeb npaum li cas? Nws tso cai rau cov hniav turbine ua haujlwm ntawm qhov kub siab dua, thiab rau txhua kaum degrees qhov kub ntawm lub cav nce ntxiv, lub zog nce ntxiv ntau, thaum kev siv roj txo qis. Rau cov dav hlau uas ya kaum txhiab mais, kev txuag roj thiab kev txhim kho kev ua tau zoo yog astronomical. Yog tias lub txheej tiv thaiv cua sov yog "kev siv sab nraud," ces lub luag haujlwm ntawm hmoov alumina hauv cov ntaub ntawv sib xyaw yog "kev ntxiv sab hauv."
Cov dav hlau niaj hnub, cov satellites, thiab cov rockets siv cov khoom sib xyaw ua ke los txo qhov hnyav. Txawm li cas los xij, cov khoom sib xyaw ua ke no muaj qhov tsis zoo - lawv tsis tiv taus kev hnav, yooj yim rau qhov kub siab, thiab tsis muaj qhov tawv txaus. Cov kws tshawb fawb ntse tau siv cov hmoov alumina, tshwj xeeb tshaj yog nano-sizedalumina hmoov, sib npaug rau hauv cov roj hmab, zoo li thaum koj zom cov hmoov. Qhov kev sib xyaw ua ke no muaj cov txiaj ntsig zoo kawg nkaus: qhov nyuaj ntawm cov khoom siv, kev tiv taus kev hnav, kev tiv taus cua sov, thiab txawm tias qhov ruaj khov ntawm qhov ntev tag nrho zoo dua qub.
Piv txwv li, cov plag tsev hauv dav hlau, qee yam khoom sab hauv, thiab txawm tias qee qhov khoom tsis muaj lub nra hnyav siv cov khoom sib xyaw ua ke alumina no. Qhov no tsis yog tsuas yog ua rau lawv sib dua thiab muaj zog dua xwb tab sis kuj ua rau lub zog qeeb qeeb, txhim kho kev nyab xeeb zoo heev. Cov cuab yeej precision txhawb nqa ntawm cov satellites, uas xav tau kev hloov pauv me me hauv qab qhov kub thiab txias heev, kuj tseem tshuav ntau rau cov khoom no. Nws zoo li "txhaj tshuaj" ib lub pob txha rau hauv cov yas yooj ywm, muab nws ob qho tib si lub zog thiab kev ywj pheej.
Hmoov alumina kuj muaj "kev txawj zais cia," tseem ceeb heev hauv kev lag luam aerospace - nws yog cov khoom siv rwb thaiv cua sov zoo heev thiab tiv taus ablation.
Thaum lub dav hlau rov qab nkag mus rau hauv huab cua los ntawm qhov chaw, nws zoo li poob rau hauv lub cub tawg plasma ntawm ntau txhiab degrees. Lub plhaub sab nraud ntawm lub capsule rov qab nkag yuav tsum muaj ib txheej tiv taus cua sov uas "txiav nws tus kheej rau qhov zoo dua." Hmoov alumina ua lub luag haujlwm tseem ceeb hauv kev tsim ntau yam khoom tiv taus cua sov. Thaum ua ke nrog lwm cov khoom, nws tsim ib txheej ceramic tawv, porous, thiab insulating heev ntawm qhov chaw. Txheej no maj mam ablates ntawm qhov kub siab, nqa cua sov thiab tswj qhov kub hauv chav nyob hauv qhov ntau ntawm kev ciaj sia rau cov astronauts los ntawm nws tus kheej noj. "Txhua zaus kuv pom lub capsule rov qab los tsaws zoo, thiab txheej sab nraud ntawm cov khoom tiv taus cua sov yog charred dub, kuv xav txog cov mis alumina-based uas peb rov ua dua," hais tias ib tug engineer laus uas saib xyuas cov khoom tiv taus cua sov. "Nws hlawv, tab sis nws lub luag haujlwm tau ua tiav zoo kawg nkaus."
Dhau ntawm cov ntawv thov hardcore "pem hauv ntej" no,alumina hmoovyog qhov tseem ceeb ib yam nkaus "tom qab qhov xwm txheej." Piv txwv li, hauv kev tsim cov khoom siv precision rau dav hlau thiab rockets, ntau cov alloys muaj zog siab yuav tsum tau sintered. Thaum lub sijhawm sintering, cov khoom siv hmoov metallurgy yuav tsum tau txhawb nqa hauv lub cub tawg kub siab siv cov "shims" lossis "firing plates." Cov phaj no yuav tsum tiv taus cua sov, tsis deformable, thiab tsis lo rau cov khoom. Firing plates ua los ntawm high-purity alumina ceramic ua qhov kev xaiv zoo tshaj plaws. Ntxiv mus, hauv kev sib tsoo thiab polishing cov txheej txheem ntawm qee qhov ultra-precision qhov chaw, high-purity alumina micropowder yog ib qho kev nyab xeeb thiab ua haujlwm tau zoo polishing nruab nrab.
Tau kawg, cov khoom muaj nqis zoo li no tsis tuaj yeem siv tsis saib xyuas. Puas yog qhov huv si txaus? Puas yog qhov faib tawm ntawm cov khoom me me sib npaug? Puas muaj kev sib sau ua ke? Puas yog qhov dispersibility zoo? Txhua qhov ntsuas cuam tshuam rau kev ua tau zoo ntawm cov khoom kawg. Hauv kev lag luam aerospace, txawm tias qhov yuam kev me me tuaj yeem ua rau muaj kev puas tsuaj loj heev. Yog li ntawd, txij li kev xaiv cov khoom siv raw thiab kev hloov kho cov txheej txheem mus rau cov txheej txheem siv, txhua kauj ruam yog raws li cov qauv tswj hwm nruj, yuav luag xav tau.
Sawv ntawm lub chaw tsim khoom dav hlau niaj hnub no, ntsia lub cev dav hlau uas ci ntsa iab txias txias hauv qab lub teeb, koj paub tias lub cev dav hlau nyuaj no ya saum ntuj yog qhov tshwm sim ntawm ntau yam khoom siv zoo li hmoov alumina, txhua yam ua nws lub luag haujlwm kom tag nrho. Nws tsis yog lub hauv paus tseem ceeb, tab sis nws ua kom lub cev muaj zog; nws tsis muab lub zog loj heev, tab sis nws tiv thaiv lub hauv paus ntawm lub cev tsav; nws tsis txiav txim siab ncaj qha mus rau txoj kev, tab sis nws ua kom muaj kev nyab xeeb ntawm kev ya dav hlau.
Txij li cov txheej txheej uas tiv taus kub siab mus rau cov ntaub ntawv sib xyaw ua ke, thiab txawm tias cov txheej txheej uas tiv taus kub uas tiv taus tus kheej, daim ntawv thov ntawmalumina hmoovHauv kev lag luam aerospace, nws txuas ntxiv mus tob zuj zus mus rau qhov sib dua, muaj zog dua, thiab tiv taus ntau dua rau qhov chaw ib puag ncig hnyav. Yav tom ntej, nrog rau kev tsim cov ntaub ntawv alumina nrog kev ntshiab dua thiab cov qauv tshwj xeeb dua (xws li nanowires thiab nanosheets), nws yuav ua lub luag haujlwm tsis tau xav txog hauv kev tswj hwm thermal, kev tshem tawm cua sov ntawm cov khoom siv hluav taws xob, thiab txawm tias kev tsim khoom hauv qhov chaw.
Cov hmoov dawb no, ntsiag to thiab ruaj khov, muaj lub zog loj heev uas txhawb nqa tib neeg txoj kev tshawb nrhiav saum ntuj ceeb tsheej. Nws ua rau peb nco qab tias thaum peb mus txog cov hnub qub, peb tsis yog tsuas yog xav tau lub zeem muag loj thiab lub zog loj xwb, tab sis kuj xav tau cov "tis uas tsis pom" uas ntsiag to thiab ruaj khov uas ua rau cov khoom siv yooj yim ua haujlwm tau zoo tshaj plaws. Lub sijhawm tom ntej koj saib lub dav hlau ya saum ntuj lossis saib qhov kev ua yeeb yam zoo kawg nkaus ntawm lub foob pob hluav taws, koj yuav nco ntsoov tias hauv lub cev hlau thiab cov khoom sib xyaw, muaj "lub siab dawb," ntsiag to tiv thaiv kev nyab xeeb thiab kev ua tau zoo ntawm txhua lub dav hlau.