Cov teebmeem ntawm Hydroxyl pawg hauv Silica ntawm Thermodynamics, UV Transmission thiab Structure
Fused silica, nrog rau nws qhov zoo tshaj plaws optical transmittance, tsis tshua muaj thermal expansion coefficient, thiab cov hluav taws xob zoo heev, tau dhau los ua cov khoom tseem ceeb hauv cov teb xws li semiconductor lithography, inertial confinement fusion, siab -lub zog laser tshuab, thiab aerospace.
Nrog rau kev nce qib hauv siab -purity silica purification technologies thiab qhov tshwm sim ntawm kev ua haujlwm siab heev xws li qis-kub 3D luam ntawv thiab femtosecond laser vuam, nws daim ntawv thov tau nthuav dav ntxiv. Piv txwv li, cov khoom siv kho qhov muag ua los ntawm fused silica rau lithography tsis tsuas yog xav tau kev xa tawm siab hauv cheeb tsam ultraviolet sib sib zog nqus tab sis kuj yuav tsum muaj cov khoom kho qhov muag zoo, thermal, thiab txhua yam ruaj khov nyob rau hauv ntev - lub sij hawm raug rau siab - lub zog ultraviolet beams.
Lub macroscopic zog ntawm fused silica yog ze ze rau nws cov microscopic topological qauv thiab impurity defects. Ntawm lawv, pawg hydroxyl yog ubiquitous thiab unavoidable extrinsic defects thaum lub sij hawm npaj ntawm fused silica. Txawm hais tias doping nrog lwm yam impurities xws li txhuas kuj tseem cuam tshuam rau qhov siab -kub viscosity thiab deformation tsis kam ntawm fused silica, kev cuam tshuam ntawm pawg hydroxyl yog qhov nyuaj tshwj xeeb. Kev tshawb fawb los ntawm Araki et al. Txawm tias nthuav tawm tus cwj pwm microscopic ntawm nanoscale dej droplets ntawm fused silica nto, ntxiv enriching cov kev nkag siab ntawm nto hydroxyl yam ntxwv. Nyob ntawm cov txheej txheem kev npaj (xws li nplaim hydrolysis lossis hluav taws xob melting), cov ntsiab lus hydroxyl hauv fused silica tuaj yeem nyob ntawm qis dua 1 ppm mus rau saum 1000 ppm. Raws li qhov tsis tuaj yeem txawv teb chaws impurity, pawg hydroxyl ua lub luag haujlwm nyuaj hauv fused silica.
Hais txog kev ua haujlwm kho qhov muag, cov pab pawg hydroxyl tuaj yeem kho qhov tsis xws luag xws li oxygen-cov chaw tsis muaj zog (ODCs) thiab E' chaw, txhim kho cov khoom xa tawm hauv thaj av nqus ultraviolet. Ntawm qhov tod tes, nyob rau hauv cov ntsiab lus ntawm thermodynamic thiab mechanical zog, siab -hydroxyl fused silica qhia hydroxyl pawg los ntawm kev rhuav tshem cov silicon tas mus li -oxygen tetrahedral moj khaum los ntawm hydrolysis cov tshuaj tiv thaiv (≡Si–O–Si≡ + H₂O → 2≡ polymerization hauv kev ua haujlwm hauv lub network.) Daim ntawv cog lus no- cov nyhuv tawg ua rau txo cov iav viscosity thiab iav hloov kubTg; lub caij no, lub xub ntiag ntawm hydroxyl pawg tsis muaj zog rau elastic modulus thiab tawg lub zog ntawm cov khoom. Txawm hais tias cov ntaub ntawv uas twb muaj lawm tau sib cais thiab tshawb nrhiav qhov kho qhov muag lossis kev siv tshuab ntawm cov pab pawg hydroxyl, cov ntaub ntawv pov thawj kev sim hais txog yuav ua li cas hydroxyl concentration cuam tshuam rau macroscopic thermodynamic zog thiab kho qhov muag kis tus yam ntxwv ntawm fused silica tseem tsis muaj.
Hauv daim ntawv no, ob tus neeg sawv cev ua lag luam siab -purity hluavtaws fused silica qib, JGS1 thiab JGS3, raug xaiv los ua cov khoom tshawb fawb. Siv qhov sib txawv scanning calorimetry, elastic modulus kuaj, Raman spectroscopy, thiab nqus ultraviolet spectroscopy, cov teebmeem ntawm hydroxyl pawg ntawm cov qauv, thermal, mechanical, thiab optical zog ntawm fused silica tau kawm systematically. Lub hom phiaj yog los qhia meej txog cov kev cai ntawm cov pab pawg hydroxyl ntawm ntau yam khoom ntawm fused silica, yog li muab kev tshawb fawb hauv paus rau kev xaiv cov khoom siv thiab cov txheej txheem kev ua kom zoo ntawm siab -kev ua tau zoo fused silica nyob rau hauv kev ua haujlwm sib txawv.
1. Kev ntsuas cua sov
Daim duab 1 qhia txog qhov nkhaus ntawm qhov tshwj xeeb kub muaj peev xwm (Cp) piv rau qhov kub thiab txias rau fused silica nrog cov ntsiab lus hydroxyl sib txawv. Siv cov txheej txheem extrapolated pib, piv txwv li, noj qhov kev sib tshuam ntawm qhov txuas txuas ntxiv ua ntej qhov kev hloov pauv thiab qhov tangent ntawm txoj kab siab tshaj plaws nyob rau hauv cheeb tsam kev hloov pauv,Tg ntawm JGS1 tau ntsuas yog 1329 K, uas yog 64 K qis dua li ntawm JGS3 (Tg=1393 K). Qhov laj thawj tseem ceeb rau qhov tshwm sim no yog tias, piv nrog Si-O-Si lub moj khaum, cov qauv qhia Si-OH cuam tshuam qhov txuas ntxiv ntawm lub network topological ntawm fused silica.
Ntawm ib sab, raws li ib pab pawg neeg impurity, pawg hydroxyl rhuav tshem kev sib txuas ntawm silicon -oxygen tetrahedra, txo cov topological polymerization thiab viscosity ntawm lub network, yog li ua rau txo qis.Tg. Ntawm qhov tod tes, piv nrog kev sib txuas ntawm cov pa oxygen, O-H daim ntawv cog lus hauv Si-OH pawg muaj zog sib txuas tsis muaj zog thiab nthuav qhia tshwj xeeb khoov thiab hloov kev vibrational hom. Cov hom kev vibrational ntxiv no nqus tau cov cua sov ntau dua thaum cua sov thiab ncaj qha rau kev nce hauvCp. Nyob rau hauv luv luv, cov kev taw qhia ntawm hydroxyl pawg loosens cov iav nruj network, uas macroscopically manifests li txo thermal stability thiab qis dua.Tg.
2. Temperature-Dependent Elastic Modulus
Daim duab 2 qhia qhov nkhaus ntawm elastic modulus piv rau qhov kub thiab txias (300-1300 K) rau fused silica nrog cov ntsiab lus hydroxyl sib txawv. Cov txiaj ntsig kev sim qhia tau hais tias ob qho tib si kuaj pom muaj qhov ua tau zoo ntawm qhov kub thiab txias coefficient cuam tshuam thoob plaws tag nrho cov ntsuas kub. Cov yam ntxwv ntawm kev nce hardness nrog nce kub yog ib qho ntawm tetrahedral network fused silica, thiab nws cov txheej txheem feem ntau yog los ntawm cov evolution ntawm iav network qauv: nrog nce kub, thermal zog ntawm bridging oxygen atoms hloov cov nyiaj ntawm cov ces kaum ntawm Si-O-Si daim ntawv cog lus, txo cov ntim dawb ntawm lub iav network thiab ua rau cov txiaj ntsig tag nrho ntawm cov iav network. modulus.
Qhov tseem ceeb, txawm hais tias qhov ntsuas kub siab (1300 K) tseem nyob hauv qhov sub-Tg cheeb tsam ntawm cov qauv, feem ntau cuam tshuam cov khoom- xeev elastic teb es tsis yog viscoelastic ntws, Young's modulus ntawm JGS1 tsis tu ncua qis dua li ntawm JGS3 ntawm 300 K thiab 1300 K} Hydroxyl pawg ua haujlwm yog ua kom paub txog hydrolysis (≡Si–O–Si≡ + H₂O → 2≡Si–OH), uas txo cov network rigidity thiab yog li ua rau ib tug txo nyob rau hauv macroscopic elastic modulus. Ua ke nrog qisTg (1329 K) ntawm JGS1 ntsuas los ntawm DSC, nws muaj peev xwm inferred hais tias cov kev taw qhia ntawm hydroxyl pawg, thaum tsis hloov tus qauv ntawm nce elastic modulus nrog kub nyob rau hauv fused silica, tsis muaj zog qhov txhav thiab siab - kub thermal stability ntawm lub iav topological network.
3. Tus yam ntxwv zoo
Daim duab 3 piv rau Raman spectra ntawm fused silica nrog cov ntsiab lus hydroxyl sib txawv. Hauv thaj tsam 400-1200 cm⁻¹, ob qho tib si kuaj pom cov yam ntxwv ntawm cov khoom siv amorphous fused silica. Raws li cov ntaub ntawv, lub band nyob ze 440 cm⁻¹ sib haum mus rau symmetric stretching vibration (ω₁) ntawm Si-O-Si bridging oxygen bonds, xav txog qhov tseem ceeb rau -ntiv nplhaib qauv hauv lub iav topological network; bands nyob ze 800 thiab 1060 cm⁻¹ raug ntaus nqi rau qhov khoov kev co (ω₃) thiab asymmetric stretching vibration (ω₄) ntawm Si–O–Si, feem.
Qhov sib txawv tseem ceeb tshaj plaws yog tshwm sim hauv ob yam. Ua ntej, JGS1 qhia tau hais tias lub ncov muaj zog ntawm 3675 cm⁻¹, sib haum mus rau qhov kev co ntawm O-H daim ntawv cog lus hauv cov pawg silanol cais (Si-OH), ncaj qha lees paub qhov muaj siab ntawm chemically bonded hydroxyl pawg hauv cov qauv no. Thib ob, nyob rau hauv qhov qis- thaj tsam zaus ze 594 cm⁻¹, qhov kev siv ntawm cov yam ntxwv ncov (D₂ ncov) ntawm JGS1 yog qis dua li ntawm JGS3; cov qhab no raug xa mus rau kev vibration ntawm peb -cov tswv cuab siloxane nplhaib qauv. Qhov txo qis ntawm D₂ ncov qhia tau hais tias qhov kev taw qhia ntawm hydroxyl pawg nyiam ua rau peb cov -cov tswv cuab siloxane nplhaib cov qauv, so lub iav network thiab ua kom muaj kev ntxhov siab hauv zos hauv lub network.
Daim duab 4 nthuav tawm lub tshuab nqus tsev ultraviolet transmission spectra ntawm fused silica nrog cov ntsiab lus hydroxyl sib txawv. Cov txiaj ntsig tau pom tias JGS3 nthuav tawm qhov sib txawv ntawm qhov nqus ntawm 163 nm (7.6 eV), sib xws rau hom I oxygen-cov chaw tsis txaus (ODC-I). Qhov no qhia tau hais tias JGS3 tau tsim nyob rau hauv cov pa oxygen-ib puag ncig tsis txaus thiab tsis muaj cov pab pawg hydroxyl txaus los ua kom cov kab mob sib kis no lossis cov chaw tsis raug. Hauv qhov sib piv, qhov nqus dej ntawm JGS1 yog xiav -hloov los ntawm 7 nm (los ntawm 172 nm mus rau 165 nm), thiab tsis pom qhov nqus pom tseeb ntawm 160-180 nm. Qhov kev txhim kho hauv kev xa tawm no feem ntau yog los ntawm kev kho cov nyhuv ntawm hydroxyl pawg ntawm cov iav network topology thiab qhov tsis xws luag. Ua ntej, Raman spectra tau lees paub tias peb lub nplhaib - cov tswv cuab lub nplhaib hauv JGS1 raug txo qis (qis D₂ ncov), qhia tias kev taw qhia ntawm pawg hydroxyl txo qhov feem ntawm Si-O-Si daim ntawv cog lus. Qhov thib ob, thaum npaj, JGS1 tuaj yeem kho cov pa oxygen{24}} tsis muaj qhov tsis xws luag lossis dangling bond optical absorption centres hauv lub network los ntawm kev tsim Si-OH, yog li txo qis lub teeb nqus ntawm fused silica hauv thaj av nqus ultraviolet thiab ua rau xiav hloov pauv ntawm qhov nqus nqus ntawm ntug.
Cov ntsiab lus tseem ceeb
Txo thermal stability ntawm fused silica: Qhov ntsuasTg ntawm JGS1 yog 1329 K, 64 K qis dua li ntawm JGS3 (1393 K); tsis tas li ntawd, covCp ntawm JGS1 tsis tu ncua siab dua li ntawm JGS3 nyob rau hauv qhov ntsuas kub ntau. Qhov no yog vim qhov kev taw qhia ntawm cov pab pawg hydroxyl los ntawm kev rhuav tshem Si-O-Si lub moj khaum thaum lub sij hawm JGS1 fabrication, nrog rau ntxiv kev vibrational hom qhia los ntawm Si-OH pawg.
Anomalous temperature-dependent modulus behavior: Txawm hais tias ob qho tib si fused silica qib pom muaj qhov tsis zoo ntawm cov khoom siv ntxiv (dE/dT> 0) nruab nrab ntawm 300 K thiab 1300 K, lub elastic modulus ntawm JGS1 tsis tu ncua qis dua li ntawm JGS3 nyob rau hauv no ntau yam. Qhov no qhia tau hais tias hydroxyl kev taw qhia txo cov rigidity ntawm lub network topological qauv tab sis tsis hloov tus cwj pwm ntawm nce elastic modulus nrog kub nyob rau hauv fused silica.
Cov yam ntxwv thiab kho qhov muag: Raman spectra qhia tias qhov kev siv ntawm D₂ qhov tsis xws luag band (594 cm⁻¹) ntawm JGS1 yog txo qis, thiab lub tshuab nqus tsev ultraviolet spectra qhia tau hais tias qhov kev txiav tawm ntawm JGS1 yog xiav - hloov los ntawm 7 nm piv nrog JGS3 (los ntawm 172 nm rau 165 min absorption), 163nm ua. Qhov no qhia tau hais tias qhov kev taw qhia ntawm cov pab pawg hydroxyl txo qhov feem ntawm Si-O-Si daim ntawv cog lus thiab kho cov pa oxygen{10}} qhov tsis xws luag hauv lub network, yog li txo qis kev nqus ntawm fused silica hauv thaj av nqus ultraviolet.
