Qhov Kev Sib Tw Hluav Taws Xob - Vim li cas Magnesium Oxide Ua lossis tawg Cryogenic Cua sov
Hauv txhua lub tshuab rhaub dej kub yog cov khoom siv uas cov neeg siv feem ntau tsis pom tab sis qhov ntawd txiav txim siab tag nrho cov cuab yeej kev ntseeg tau: magnesium oxide (MgO). Cov hmoov dawb no muab cov hluav taws xob rwb thaiv tsev ntawm cov hlau tsis kam thiab cov hlau sheath thaum tseem ua cua sov los ntawm cov hlau mus rau hauv lub plhaub. Hauv kev siv tus qauv, MgO ua haujlwm zoo. Tab sis ntawm -30℃thiab qis dua, nws dhau los ua ib qho tseem ceeb tshaj plaws - thiab nyuaj - teeb meem engineering.
Qhov teeb meem noo noo
MgO yog hygroscopic - nws absorbs noo noo los ntawm huab cua. Thaum lub sijhawm tsim khoom, yog tias MgO raug rau huab cua ntub, nws khaws cov dej molecules. Nyob rau hauv ib lub tshuab cua sov uas yooj yim epoxy seals, noo noo kuj tuaj yeem nkag mus qeeb qeeb thaum lub sijhawm ua haujlwm.
Nyob rau hauv chav tsev kub, qhov no noo noo tsuas yog ib qho teeb meem - nws me ntsis txo cov rwb thaiv tsev tiv thaiv tab sis feem ntau tsis ua rau tsis ua hauj lwm. Tab sis ntawm sub- xoom qhov kub thiab txias, kaw cov dej khov. Dej nthuav tawm li ntawm 9% thaum nws tig mus rau dej khov. Nyob rau hauv lub compacted MgO rwb thaiv tsev, qhov kev nthuav dav no tsim lub siab uas tuaj yeem tawg cov rwb thaiv tsev. Thaum lub cua sov tom qab sov, cov dej khov yaj, thiab cov kab nrib pleb dhau los ua txoj hauv kev rau hluav taws xob los yog luv luv.
Kev daws nyob rau hauvhermetic sealing. Hloov chaw yooj yim epoxy seals uas tso cai rau cov dej nkag mus rau lub sijhawm, cov khoom siv hluav taws xob zoo tshaj plaws siv cov iav - mus rau - cov ntsaws ruaj ruaj hlau lossis cov khoom siv ceramic. Cov no tsim kom ruaj khov, nqus tsev vacuum-tight barriers uas tiv thaiv kom tsis txhob ya raws nkag mus rau lub rhaub txhua. Kev ntsuam xyuas qhia tau hais tias hermetically kaw cov cua sov ua kom muaj kev tiv thaiv kev tiv thaiv siab tshaj 1000 MΩ tom qab siv ntau xyoo, thaum cov khoom siv kaw cov cua sov poob rau 10-100 MΩ - 10-100x qhov sib txawv ntawm dielectric kev ncaj ncees.
Thermal contraction
MgO shrinks raws li qhov kub thiab txias - los ntawm kwv yees li 0.5% ntawm chav tsev kub rau -196 degree. Qhov no tej zaum yuav tsis zoo li ntau, tab sis nyob rau hauv ib tug nruj packed cua sov nrog tsawg clearances, txawm lub me me contraction tsim kev ntxhov siab. Yog tias MgO ntom ntom tsis sib npaug los yog qhov loj me me faib tsis zoo, qhov kev cog lus tuaj yeem ua rau cov rwb thaiv tsev tawg lossis cais tawm ntawm lub hnab.
Qhov tseem ceeb yogsiab - ntom ntim. Cov cua sov txheem ua tiav 85-90% ntawm qhov theoretical siab tshaj plaws ceev rau MgO. Cryogenic-rated heaters siv tshwj xeeb hydraulic nias thiab vibration cov txheej txheem kom ua tiav 95-98% ntom. Qhov siab dua no txo cov voids qhov twg cov dej noo tuaj yeem sau tau thiab qhov chaw thermal contraction tuaj yeem ua rau qhov khoob. Nws kuj tseem txhim kho thermal conductivity, txawm hais tias nyob rau hauv cov kev pab cuam cryogenic qhov no yog qhov tseem ceeb tsawg dua li kev ncaj ncees.
Thermal shock tsis kam
Hauv sub-zero daim ntawv thov, lub tshuab cua sov tau hloov pauv sai - los ntawm -30℃ambient mus rau ntau pua degrees ua haujlwm kub hauv vib nas this. Qhov kev poob siab thermal no ua rau MgO rwb thaiv tsev hnyav heev. Siab-qhov ceev, nplua-grained MgO tuaj yeem tswj qhov kub thiab txias hloov sai li 100℃ib feeb. Tsawg-density rwb thaiv tsev yuav tawg nyob rau hauv tib yam kev mob.
Cov qauv nplej ntawm MgO tseem ceeb npaum li qhov ceev. Cov tuam txhab hwm hwm xaiv MgO nrog qhov tshwj xeeb particle loj faib thiab cov duab zoo rau kev ua haujlwm thermal shock. Qhov no tsis yog ib yam dab tsi uas tuaj yeem muab ntxiv tom qab - nws yuav tsum tau tsim kho rau hauv cov khoom txij thaum pib.
Txias- qhov kawg tsim thiab qhov kub thiab txias gradient
Kev hloov pauv los ntawm qhov cua sov ntawm lub tshuab cua sov mus rau qhov txias txias - qhov twg qhov kev tawm mus - yog qhov tseem ceeb rau kev ruaj ntseg ntawm rwb thaiv tsev. Hauv cheeb tsam kev hloov pauv no, qhov ntsuas kub poob los ntawm ntau pua degrees mus rau ambient -30℃hla ib qho luv luv. MgO rwb thaiv tsev nyob rau hauv cheeb tsam no muaj kev ntxhov siab tshaj thermal.
Kev txias kom zoo-kawg tsim txuas ntxiv qhov tsis muaj cua sov rau 25-50mm hauv cov ntawv thov cryogenic, piv rau 5-10mm hauv cov cua sov txheem. Qhov no muab qhov hloov pauv hloov pauv hloov pauv uas txo cov kev ntxhov siab thermal ntawm cov rwb thaiv tsev thiab cov ntsaws ruaj ruaj. Nws kuj tseem khaws cov kev sib txuas ntawm lub davhlau ya nyob twg saum toj -40 degree, qhov twg cov qauv txhuas hlau rwb thaiv tsev nyob ruaj khov.
Internal noo noo getters
Qee lub tshuab cua sov cryogenic suav nrog cov khoom siv desiccant hauv lub rhaub kom nqus cov dej seem seem ntawm kev tsim khoom lossis cov dej noo uas nkag mus rau cov ntsaws ruaj ruaj thaum lub sijhawm. Cov getters no muab ib txheej ntxiv ntawm kev tiv thaiv, txawm tias lawv muaj peev xwm tsawg. Lawv yog cov tseem ceeb tshaj plaws hauv cov cua sov uas tsim los rau 10+ xyoo kev pab cuam lub neej.
Kev ntsuas ntawm qhov kub thiab txias
Rwb thaiv tsev uas ntsuas zoo kawg nkaus ntawm chav tsev kub yuav poob ntawm -30℃. Qhov no yog vim li cas cryogenic-rated heaters yuav tsum tau kuaj ntawm qhov kub thiab txias thaum lub sijhawm tsim khoom. Kev kuaj paug ib nrab tuaj yeem kuaj pom qhov tsis ua haujlwm ntawm qhov hluav taws xob tsis ua haujlwm - cov voids me me lossis cov kab nrib pleb uas ua rau muaj kev ntxhov siab hauv zej zog. Qhov kev ntsuam xyuas rhiab no pom kev tsim khoom sib txawv uas cov qauv hluav taws xob tsis zoo.
Lub luag haujlwm ntawm watt ceev
Acartridge rhaubnrog acartridge heater ceevntawm 5-7 W / cm² txo qis thermal stress ntawm MgO rwb thaiv tsev dua ib chav tsev siab dua. Cov kub sab hauv qis txhais tau tias tsawg dua thermal expansion thiab contraction, tsawg thermal shock thaum pib, thiab tsis tshua muaj kev ntxhov siab ntawm cov ntsaws ruaj ruaj. Cov rwb thaiv tsev nyob ruaj khov ntev dua, tswj nws lub zog dielectric thiab thermal conductivity ntau xyoo ntawm kev pabcuam.
Kev tsim vaj tsev ntawm MgO rwb thaiv tsev rau cov kev pabcuam cryogenic yog ib thaj chaw tshwj xeeb uas sib txuas cov ntaub ntawv kev tshawb fawb, kev tsim khoom precision, thiab kev sim nruj. Qhov sib txawv ntawm lub rhaub dej kub uas kav ntau xyoo thiab ib qho uas tsis ua haujlwm hauv lub lis piam feem ntau los rau cov ntsiab lus tsis pom - qhov ntom ntawm MgO, qhov zoo ntawm cov ntsaws ruaj ruaj, thiab qhov tsim ntawm qhov txias txias -kawg hloov. Cov ntawv thov sib txawv xav tau qib sib txawv ntawm rwb thaiv tsev ncaj ncees. Kev ntsuam xyuas kev ua haujlwm ntawm kev ua haujlwm - qhov kub thiab txias, thermal cycling zaus, kev ya raws - yog qhov tseem ceeb rau kev qhia txog cov txheej txheem rwb thaiv tsev zoo.
