Cov qauv ntawm iav
Lub zog physicochemical ntawm iav tsis yog tsuas yog txiav txim siab los ntawm nws cov tshuaj muaj pes tsawg leeg, tab sis kuj tseem cuam tshuam nrog nws cov qauv.Tsuas yog los ntawm kev nkag siab txog kev sib raug zoo ntawm cov qauv, muaj pes tsawg leeg, cov qauv thiab kev ua tau zoo ntawm iav, nws tuaj yeem ua rau iav cov ntaub ntawv lossis cov khoom lag luam uas tau txiav txim siab physicochemical los ntawm kev hloov cov tshuaj muaj pes tsawg leeg, thermal keeb kwm lossis siv qee txoj kev kho lub cev thiab tshuaj.
Cov yam ntxwv ntawm iav
iav yog ib ceg ntawm amorphous khoom, uas yog cov khoom siv amorphous nrog cov khoom siv kho tshuab.Nws feem ntau hu ua "supercooled kua".Hauv qhov xwm txheej, muaj ob lub xeev ntawm cov khoom tseem ceeb: lub xeev zoo thiab lub xeev tsis zoo.Lub npe hu ua nonproductive xeev yog lub xeev ntawm cov khoom uas tau txais los ntawm ntau txoj kev thiab tus cwj pwm los ntawm kev tsis sib haum xeeb.Glassy xeev yog ib yam khoom uas tsis yog tus qauv.Cov atoms hauv iav tsis muaj qhov ntev-ntev xaj nyob rau hauv qhov chaw zoo li siv lead ua, tab sis lawv zoo ib yam li cov kua thiab muaj qhov luv-ntau txiav txim.Cov iav muaj peev xwm tuav tau ib yam zoo li cov khoom, tab sis tsis zoo li cov kua ntws hauv qab nws qhov hnyav.Cov iav iav muaj cov yam ntxwv tseem ceeb hauv qab no.
(1) Kev npaj ntawm cov khoom ntawm isotropic glassy yog qhov tsis xwm yeem thiab tsis sib xws.Yog li ntawd, thaum tsis muaj kev ntxhov siab nyob rau hauv lub khob, nws lub cev thiab tshuaj muaj zog (xws li hardness, elastic modulus, thermal expansion coefficient, thermal conductivity, refractive index, conductivity, thiab lwm yam) yog tib yam nyob rau hauv tag nrho cov lus qhia.Txawm li cas los xij, thaum muaj kev ntxhov siab hauv lub khob, cov qauv kev sib xws yuav raug rhuav tshem, thiab cov iav yuav pom anisotropy, xws li pom tseeb qhov sib txawv ntawm qhov muag pom.
(2) Metastability
Qhov laj thawj yog vim li cas lub iav nyob rau hauv lub xeev metastable yog tias cov iav tau txais los ntawm kev txias sai ntawm cov yaj.Vim qhov nce ntxiv ntawm viscosity thaum lub sij hawm txias, cov khoom tsis muaj sij hawm los tsim cov txheej txheem tsis tu ncua, thiab lub zog sab hauv ntawm lub cev tsis yog tus nqi qis tshaj, tab sis hauv lub xeev metastable;Txawm li cas los xij, txawm hais tias lub khob nyob rau hauv lub zog siab dua, nws tsis tuaj yeem hloov pauv mus rau hauv cov khoom vim nws cov viscosity siab ntawm chav tsev kub;Tsuas yog nyob rau hauv tej yam kev mob sab nraud, uas yog hais tias, peb yuav tsum kov yeej lub peev xwm barrier ntawm cov ntaub ntawv los ntawm glassy xeev mus rau crystalline lub xeev, lub iav yuav tsum tau sib cais.Yog li ntawd, los ntawm qhov pom ntawm thermodynamics, lub iav lub xeev tsis ruaj khov, tab sis los ntawm qhov pom ntawm kinetics, nws ruaj khov.Txawm hais tias nws muaj qhov nyiam ntawm nws tus kheej tso cov cua sov hloov mus rau hauv cov khoom siv lead ua nrog lub zog sab hauv, qhov tshwm sim ntawm kev hloov mus rau hauv lub xeev siv lead ua yog qhov me me ntawm chav tsev kub, yog li cov iav nyob hauv lub xeev metastable.
(3) Tsis muaj qhov ntsuas kub ruaj khov
Kev hloov pauv ntawm cov khoom siv iav los ntawm cov khoom mus rau cov kua yog ua tiav nyob rau hauv qhov kub thiab txias (hloov qhov kub ntau), uas txawv ntawm cov khoom siv crystalline thiab tsis muaj qhov chaw ruaj khov.Thaum cov khoom hloov pauv los ntawm yaj mus rau cov khoom, yog tias nws yog cov txheej txheem crystallization, cov theem tshiab yuav raug tsim nyob rau hauv lub cev, thiab crystallization kub, cov khoom thiab ntau lwm yam yuav hloov sai sai.
Raws li qhov kub thiab txias, qhov viscosity ntawm cov yaj nce, thiab thaum kawg cov iav yog tsim.Cov txheej txheem solidification yog ua tiav nyob rau hauv ib tug dav kub ntau yam, thiab tsis muaj tshiab crystals yog tsim.Qhov kub ntau ntawm kev hloov pauv ntawm yaj mus rau cov iav khov yog nyob ntawm cov tshuaj muaj pes tsawg leeg ntawm iav, uas feem ntau hloov pauv hauv kaum mus rau ntau pua degrees, yog li iav tsis muaj qhov chaw ruaj khov, tab sis tsuas yog qhov kub ntawm qhov muag.Hauv qhov no, iav maj mam hloov los ntawm viscoplastic mus rau viscoelastic.Cov txheej txheem hloov maj mam hloov ntawm cov cuab yeej no yog lub hauv paus ntawm iav nrog kev ua haujlwm zoo.
(4) Txuas ntxiv thiab thim rov qab ntawm cov khoom hloov pauv
Cov cuab yeej hloov txheej txheem ntawm cov khoom siv iav los ntawm lub xeev melting mus rau lub xeev ruaj khov yog nruam thiab thim rov qab, nyob rau hauv uas muaj ib feem ntawm thaj tsam kub uas yog yas, hu ua "transformation" lossis "abnormal" cheeb tsam, uas cov khoom muaj kev hloov pauv tshwj xeeb.
Nyob rau hauv cov ntaub ntawv ntawm crystallization, cov khoom hloov raws li qhia nyob rau hauv lub nkhaus ABCD, t.Nws yog lub melting point ntawm cov khoom.Thaum lub iav yog tsim los ntawm supercooling, cov txheej txheem hloov raws li qhia hauv abkfe nkhaus.T yog lub iav hloov pauv kub, t yog qhov muag kub ntawm lub iav.Rau oxide iav, viscosity sib haum rau ob qhov tseem ceeb no yog hais txog 101pa·s thiab 1005p·s.
Cov qauv kev xav ntawm cov iav tawg
"Cov qauv iav" yog hais txog kev teeb tsa geometric ntawm ions lossis atoms hauv qhov chaw thiab cov qauv qub uas lawv tsim hauv iav.Kev tshawb fawb ntawm cov qauv iav tau tsim cov kev mob siab rau thiab kev txawj ntse ntawm ntau tus kws tshawb fawb iav.Thawj qhov kev sim piav qhia lub ntsiab ntawm iav yog g.tamman's supercooled kua hypothesis, uas tuav cov iav yog supercooled kua, Cov txheej txheem ntawm iav solidifying los ntawm yaj mus rau cov khoom tsuas yog ib qho txheej txheem ntawm lub cev, uas yog, nrog rau qhov kub thiab txias, molecules ntawm iav maj mam mus txog vim qhov txo qis ntawm kinetic zog. , thiab kev sib cuam tshuam quab yuam maj mam nce, uas ua rau cov qib iav nce, thiab thaum kawg tsim cov khoom ntom ntom thiab tsis sib xws.Ntau tus neeg tau ua haujlwm ntau heev.Cov kev xav zoo tshaj plaws ntawm cov qauv iav niaj hnub no yog: cov khoom lag luam kev xav, random network kev tshawb xav, gel txoj kev xav, tsib lub kaum sab xis symmetry txoj kev xav, polymer txoj kev xav thiab lwm yam.Ntawm lawv, qhov kev txhais lus zoo tshaj plaws ntawm iav yog qhov kev xav ntawm cov khoom thiab random network.
Crystal txoj kev xav
Randell l muab tso rau pem hauv ntej siv lead ua txoj kev xav ntawm iav qauv hauv xyoo 1930, vim hais tias cov qauv hluav taws xob ntawm qee lub iav zoo ib yam li cov muaju ntawm tib cov muaj pes tsawg leeg.Nws xav tias iav yog tsim los ntawm microcrystalline thiab amorphous khoom.Cov microproduct muaj cov atomic kev npaj tsis tu ncua thiab pom tseeb ciam nrog cov khoom siv amorphous.Lub microproduct loj yog 1.0 ~ 1.5nm, thiab nws cov ntsiab lus tso nyiaj ntau dua 80%.Qhov kev taw qhia ntawm microcrystalline yog qhov tsis zoo.Nyob rau hauv kev kawm txog kev annealing ntawm silicate optical iav, Lebedev pom tau tias muaj ib qho kev hloov tam sim ntawd nyob rau hauv lub nkhaus ntawm iav refractive index nrog kub ntawm 520 ℃.Nws piav qhia qhov tshwm sim no raws li kev hloov pauv ntawm quartz "microcrystalline" hauv iav ntawm 520 ℃.Lebedev ntseeg hais tias iav yog tsim los ntawm ntau "crystals", uas txawv ntawm microcrystalline, kev hloov los ntawm "crystal" mus rau amorphous cheeb tsam tau ua tiav ib kauj ruam, thiab tsis muaj ib qho kev ciam teb ntawm lawv.
Post lub sij hawm: May-31-2021