Cov kws tshawb fawb tau pom cov txheej txheem tshiab uas siv lasers los tsim cov ceramics uas tuaj yeem tiv taus ultra- kub kub, nrog rau kev siv xws li nuclear fais fab technologies mus rau spacecraft thiab dav hlau tso systems. Cov txheej txheem tuaj yeem siv los tsim cov txheej txheem ceramic, cov vuas lossis cov txheej txheem peb - qhov ntev, uas tso cai rau kev ua kom muaj zog ntxiv thaum tsim khoom siv tshiab thiab thev naus laus zis.
"Sintering yog cov txheej txheem uas cov khoom siv raw - yog hmoov lossis kua - tau hloov mus rau hauv cov khoom siv ceramic," hais tias Cheryl Xu, co-tus sau ntawv ntawm cov kev tshawb fawb no thiab tus xibfwb ntawm kev siv tshuab thiab kev siv tshuab aerospace ntawm North Carolina State University. "Rau txoj haujlwm no, peb tau tsom mus rau ultra- kub ceramic hu ua hafnium carbide (HfC). Raws li kev lig kev cai, sintering HfC yuav tsum muab cov ntaub ntawv raw rau hauv qhov cub uas tuaj yeem ncav cuag qhov kub ntawm tsawg kawg 2,200 degrees Celsius - txheej txheem uas yog lub sij hawm-siv thiab lub zog siv zog.
"Peb cov txheej txheem nrawm dua, yooj yim dua thiab xav tau lub zog tsawg dua."
Cov txheej txheem tshiab ua haujlwm los ntawm kev siv 120-watt laser rau saum npoo ntawm cov kua polymer precursor nyob rau hauv ib qho chaw inert, xws li lub tshuab nqus tsev chamber los yog chamber uas muaj argon. Lub laser sinters cov kua, tig mus rau hauv cov khoom ceramic. Qhov no tuaj yeem siv rau hauv ob txoj kev sib txawv.
Ua ntej,Cov kua dej ua ntej tuaj yeem siv los ua cov txheej txheej rau cov qauv hauv qab, xws li cov pa roj carbon sib xyaw siv hauv cov thev naus laus zis xws li missiles thiab tsheb tshawb nrhiav chaw. Lub precursor yuav siv tau rau saum npoo ntawm cov qauv thiab ces sintered nrog lub laser.
"Vim tias cov txheej txheem sintering tsis tas yuav nthuav tawm tag nrho cov qauv rau cov cua sov ntawm lub cub tawg, cov txheej txheem tshiab tuav cov lus cog tseg rau kev tso cai rau peb siv ultra{0}} kub kub ceramic coatings rau cov ntaub ntawv uas tej zaum yuav puas los ntawm sintering nyob rau hauv lub cub tawg," Xu hais.
Qhov thib obtxoj kev uas cov engineers tuaj yeem siv cov txheej txheem sintering tshiab suav nrog kev tsim khoom ntxiv, tseem hu ua 3D luam ntawv. Tshwj xeeb, txoj kev laser sintering tuaj yeem siv ua ke nrog cov txheej txheem uas zoo ib yam li stereolithography.
Nyob rau hauv cov txheej txheem no, ib tug laser yog mounted rau ntawm lub rooj uas zaum nyob rau hauv ib da dej ntawm cov kua precursor. Txhawm rau tsim peb - qauv qauv, cov kws tshawb fawb tsim cov qauv digital ntawm cov qauv thiab tom qab ntawd "slice" cov qauv ntawd rau hauv txheej. Txhawm rau pib, lub laser kos cov profile ntawm thawj txheej ntawm cov qauv hauv cov polymer, sau cov profile zoo li xim hauv daim duab. Raws li lub laser "sau" hauv cheeb tsam no, thermal zog hloov cov kua polymer rau hauv ceramic. Lub rooj tom qab ntawd txo qis me ntsis ntxiv rau hauv lub da dej polymer, thiab cov hniav cheb hla saum toj mus rau saum npoo. Lub laser ces sinters txheej thib ob ntawm cov qauv, thiab cov txheej txheem no rov ua nws tus kheej kom txog thaum koj muaj cov khoom tiav ua los ntawm sintered ceramic.
"Nws yog qhov tseeb me ntsis ntawm oversimplification hais tias lub laser yognkaus xwbXu hais tias sintering cov kua ua ntej, "Nws yog qhov tseeb dua hais tias lub laser ua ntej hloov cov kua polymer rau hauv cov khoom polymer thiab tom qab ntawd hloov cov khoom polymer rau hauv ceramic. Txawm li cas los xij, tag nrho qhov no tshwm sim sai heev - nws yog qhov tseem ceeb ntawm ib qho - cov txheej txheem kauj ruam."
Hauv cov ntaub ntawv pov thawj- ntawm- lub tswv yim kev sim, cov kws tshawb fawb tau pom tias cov txheej txheem laser sintering tsim crystalline, theem- ntshiab HfC los ntawm cov kua polymer ua ntej.
"Qhov no yog thawj zaug peb paub txog qhov twg ib tug neeg muaj peev xwm tsim HfC ntawm qhov zoo ntawm cov kua polymer ua ntej," Xu hais. "Thiab ultra- kub kub ceramics, raws li lub npe qhia, muaj txiaj ntsig zoo rau ntau yam kev siv uas cov thev naus laus zis yuav tsum tiv taus qhov kub thiab txias, xws li kev tsim hluav taws xob nuclear."
Cov kws tshawb fawb kuj tau ua pov thawj tias laser sintering tuaj yeem siv los tsim HfC cov txheej txheem zoo ntawm cov pa roj carbon-fiber reinforced carbon composites (C/C). Yeej, cov txheej txheem ceramic tau txuas nrog cov qauv hauv qab thiab tsis tev tawm.
"Lub HfC txheej ntawm C / C substrates tau pom muaj zog adhesion, kev tiv thaiv ib puag ncig, thiab muaj peev xwm siv tau los ua kev tiv thaiv thermal thiab txheej oxidation resistant," Xu hais. "Qhov no yog qhov tshwj xeeb tshaj yog vim tias, ntxiv rau cov ntawv siv hypersonic, cov qauv carbon / carbon yog siv rau hauv lub foob pob hluav taws, nres discs thiab aerospace thermal tiv thaiv systems xws li lub qhov ntswg cones thiab tis ua ntug."
Cov txheej txheem laser sintering tshiab kuj tseem ua tau zoo dua li cov pa sintering ntau txoj hauv kev.
Xu hais tias "Peb cov txheej txheem tso cai rau peb los tsim ultra- kub kub ceramic qauv thiab txheej txheej hauv vib nas this lossis feeb, thaum cov txheej txheem siv sijhawm ntau teev lossis hnub," Xu hais. "Thiab vim hais tias laser sintering yog sai thiab heev nyob rau hauv lub zos, nws siv ho tsawg zog. Dab tsi ntxiv, peb mus kom ze ua tau ib tug ntau dua yield. tshwj xeeb tshaj yog, laser sintering converts tsawg kawg yog 50% ntawm cov precursor loj rau hauv ceramics. Cov qauv siv feem ntau hloov tsuas yog 20-40% ntawm cov precursor.
Xu hais tias, "Thaum kawg, peb cov txheej txheem yog qhov txav tau yooj yim," Xu hais. "Yog lawm, nws yuav tsum tau ua nyob rau hauv ib qho chaw inert, tab sis thauj lub tshuab nqus tsev vacuum thiab additive manufacturing khoom yog yooj yim npaum li thauj ib tug haib, loj - teev cub.
"Peb zoo siab rau qhov kev nce qib hauv ceramics thiab tau qhib rau kev ua haujlwm nrog cov pej xeem thiab cov neeg koom tes los hloov cov thev naus laus zis no los siv rau hauv cov ntawv thov," Xu hais.
Daim ntawv, "Synthesis of Hafnium Carbide (HfC) of One-Step Selective Laser Reaction Pyrolysis from Liquid Polymer Precursor," yog luam tawm hauvPhau ntawv Journal ntawm American Ceramic Society. Co-tus neeg sau ntawv ntawm daim ntawv no yog Tiegang Fang, tus xibfwb ntawm kev siv tshuab thiab aerospace engineering ntawm NC State. Co- thawj tus sau ntawv yog Shalini Rajpoot, tus kws tshawb fawb tom qab kawm tiav ntawm NC State, thiab Kaushik Nonavinakere Vinod, Ph.D. tub kawm nyob NC State.
Kev tshawb fawb tau ua tiav nrog kev txhawb nqa los ntawm Center for Additive Manufacture of Advanced Ceramics, uas yog nyob ntawm University of North Carolina ntawm Charlotte.
