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Stearic acid (SA) yog siv los ua cov khoom siv hloov pauv theem (PCM) hauv cov khoom siv khaws cia lub zog. Hauv kev tshawb fawb no, txoj kev sol-gel tau siv los microencapsulate SiO2 plhaub surfactant. Ntau yam ntawm SA (5, 10, 15, 20, 30, thiab 50 g) tau encapsulated hauv 10 mL ntawm tetraethyl orthosilicate (TEOS). Cov khoom siv hloov pauv theem synthesized microencapsulated (MEPCM) tau piav qhia los ntawm Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thiab scanning electron microscopy (SEM). Cov txiaj ntsig ntawm kev piav qhia qhia tau tias SA tau encapsulated los ntawm SiO2. Kev tshuaj xyuas Thermogravimetric (TGA) qhia tau tias MEPCM muaj kev ruaj khov thermal zoo dua li CA. Siv differential scanning calorimetry (DSC), nws tau pom tias tus nqi enthalpy ntawm MEPCM tsis hloov pauv txawm tias tom qab 30 lub voj voog cua sov-txias. Ntawm tag nrho cov qauv microencapsulated, 50 g ntawm SA uas muaj MEPCM muaj qhov kub siab tshaj plaws ntawm kev yaj thiab khov, uas yog 182.53 J / g thiab 160.12 J / g, raws li. Tus nqi ua haujlwm ntawm pob khoom tau suav los ntawm kev siv cov ntaub ntawv thermal thiab qhov ua haujlwm zoo tshaj plaws tau pom rau tib cov qauv uas yog 86.68%.
Kwv yees li ntawm 58% ntawm lub zog siv hauv kev lag luam kev tsim kho yog siv los ua kom sov thiab txias cov tsev1. Yog li ntawd, qhov tseem ceeb tshaj plaws yog tsim cov tshuab hluav taws xob zoo uas suav nrog kev ua qias tuaj rau ib puag ncig2. Cov thev naus laus zis cua sov uas siv cov khoom hloov pauv theem (PCM) tuaj yeem khaws cov zog siab ntawm qhov kub qis hloov pauv3,4,5,6 thiab tuaj yeem siv dav hauv cov teb xws li kev hloov pauv cua sov, kev khaws cia lub zog hnub ci, kev tsav dav hlau thiab cua txias7,8,9. PCM nqus cov zog thermal los ntawm sab nraud ntawm lub tsev thaum nruab hnub thiab tso tawm lub zog thaum hmo ntuj10. Yog li ntawd, cov khoom hloov pauv theem raug pom zoo ua cov khoom khaws cia lub zog thermal. Tsis tas li ntawd, muaj ntau hom PCMs xws li khoom khov-khoom khov, khoom khov-kua, kua-pas thiab khoom khov-pas11. Ntawm lawv, cov khoom hloov pauv theem nrov tshaj plaws thiab siv ntau zaus yog cov khoom khov-khoom khov hloov pauv theem thiab cov khoom khov-kua hloov pauv theem. Txawm li cas los xij, lawv daim ntawv thov nyuaj heev vim muaj kev hloov pauv loj heev ntawm cov khoom siv kua-pas thiab khoom khov-pas hloov pauv theem.
PCM muaj ntau yam kev siv vim nws cov khoom: cov uas yaj ntawm qhov kub qis dua 15 ° C tuaj yeem siv rau hauv cov tshuab cua txias kom tswj tau qhov kub txias, thiab cov uas yaj ntawm qhov kub siab dua 90 ° C tuaj yeem siv rau hauv cov tshuab cua sov kom tiv thaiv hluav taws12. Nyob ntawm daim ntawv thov thiab qhov ntau ntawm cov ntsiab lus yaj, ntau yam khoom siv hloov pauv theem tau raug tsim los ntawm cov tshuaj lom neeg organic thiab inorganic sib txawv13,14,15. Paraffin yog cov khoom siv hloov pauv theem feem ntau siv nrog cua sov latent siab, tsis xeb, kev nyab xeeb thiab ntau qhov chaw yaj16,17,18,19,20,21.
Txawm li cas los xij, vim yog qhov tsis tshua muaj cua sov ntawm cov ntaub ntawv hloov theem, lawv yuav tsum tau muab tso rau hauv lub plhaub (txheej sab nraud) kom tiv thaiv kev xau ntawm cov khoom siv hauv paus thaum lub sijhawm hloov theem22. Tsis tas li ntawd, qhov yuam kev ua haujlwm lossis kev nyuaj siab sab nraud tuaj yeem ua rau lub txheej sab nraud puas tsuaj (cladding), thiab cov khoom siv hloov theem molten tuaj yeem cuam tshuam nrog cov ntaub ntawv tsim kho, ua rau muaj kev xeb ntawm cov hlau uas tau muab tso rau hauv, yog li txo qhov kev pabcuam ntawm lub tsev23. Yog li ntawd, nws yog ib qho tseem ceeb kom ua cov ntaub ntawv hloov theem encapsulated nrog cov ntaub ntawv plhaub txaus, uas tuaj yeem daws cov teeb meem saum toj no24.
Kev siv microencapsulation ntawm cov khoom hloov pauv theem tuaj yeem ua rau muaj kev hloov pauv cua sov thiab txo qhov kev cuam tshuam ib puag ncig, thiab tswj kev hloov pauv ntim. Ntau txoj kev tau tsim rau PCM encapsulation, uas yog interfacial polymerization25,26,27,28, hauv qhov chaw polymerization29,30,31,32, coacervation33,34,35 thiab cov txheej txheem sol-gel36,37,38,39. Formaldehyde resin tuaj yeem siv rau microencapsulation40,41,42,43. Melamine-formaldehyde thiab urea-formaldehyde resins yog siv ua cov ntaub ntawv plhaub, uas feem ntau tso tawm cov tshuaj lom formaldehyde thaum lub sijhawm ua haujlwm. Yog li ntawd, cov ntaub ntawv no raug txwv tsis pub siv rau hauv cov txheej txheem ntim khoom. Txawm li cas los xij, cov ntaub ntawv hloov pauv theem zoo rau ib puag ncig rau kev khaws cia lub zog thermal scalable tuaj yeem tsim tau siv cov nanocapsules hybrid raws li cov roj fatty acids thiab lignin 44.
Zhang et al 45 et al synthesize lauric acid los ntawm tetraethyl orthosilicate thiab xaus lus tias raws li qhov ntim piv ntawm methyltriethoxysilane rau tetraethyl orthosilicate nce, latent cua sov txo qis thiab qhov hydrophobicity ntawm qhov chaw nce. Lauric acid tej zaum yuav yog cov khoom siv tseem ceeb thiab muaj txiaj ntsig zoo rau kapok fibers46. Tsis tas li ntawd, Latibari et al. 47 synthesize stearic acid-based PCMs siv TiO2 ua cov khoom siv plhaub. Zhu et al. npaj n-octadecane thiab silicone nanocapsules ua PCMs muaj peev xwm 48. Los ntawm kev tshuaj xyuas cov ntaub ntawv, nws nyuaj rau nkag siab txog cov tshuaj pom zoo rau kev tsim cov khoom siv hloov pauv theem microencapsulated zoo thiab ruaj khov.
Yog li ntawd, raws li cov kws sau ntawv paub, qhov ntau ntawm cov khoom siv hloov pauv theem siv rau microencapsulation yog qhov tseem ceeb rau kev tsim cov khoom siv hloov pauv theem microencapsulated zoo thiab ruaj khov. Kev siv cov khoom siv hloov pauv theem sib txawv yuav tso cai rau peb piav qhia txog cov khoom sib txawv thiab kev ruaj khov ntawm cov khoom siv hloov pauv theem microencapsulated. Stearic acid (fatty acid) yog ib qho khoom siv zoo rau ib puag ncig, tseem ceeb rau kev kho mob thiab kev lag luam uas tuaj yeem siv los khaws lub zog thermal vim nws muaj tus nqi enthalpy siab (~ 200 J / g) thiab tuaj yeem tiv taus qhov kub txog li 72 ° C. Tsis tas li ntawd, SiO2 tsis yog hluav taws kub, muab lub zog kho tshuab siab dua, thermal conductivity thiab tshuaj lom neeg zoo dua rau cov ntaub ntawv tseem ceeb, thiab ua haujlwm ua cov khoom siv pozzolanic hauv kev tsim kho. Thaum cement sib xyaw nrog dej, PCMs tsis zoo encapsulated tuaj yeem tawg vim yog kev hnav khoom siv thiab qhov kub siab (kub ntawm hydration) tsim nyob rau hauv cov qauv pob zeb loj. Yog li ntawd, kev siv microencapsulated CA nrog SiO2 plhaub tuaj yeem daws qhov teeb meem no. Yog li ntawd, lub hom phiaj ntawm txoj kev tshawb fawb no yog los tshawb nrhiav kev ua tau zoo thiab kev ua haujlwm zoo ntawm PCMs uas tau tsim los ntawm cov txheej txheem sol-gel hauv kev siv hauv kev tsim kho. Hauv txoj haujlwm no, peb tau kawm txog ntau yam ntawm SA (ua cov khoom siv hauv paus) ntawm 5, 10, 15, 20, 30 thiab 50 g encapsulated hauv SiO2 plhaub. Ib qho nyiaj ruaj khov ntawm tetraethylorthosilicate (TEOS) hauv ib qho ntim ntawm 10 ml tau siv los ua cov tshuaj ua ntej rau kev tsim ntawm SiO2 plhaub.
Cov kua qaub stearic acid uas muaj zog (SA, C18H36O2, qhov kub yaj: 72°C) ua cov khoom tseem ceeb tau yuav los ntawm Daejung Chemical & Metals Co., Ltd., Gyeonggi-do, Kaus Lim Qab Teb. Tetraethylorthosilicate (TEOS, C8H20O4Si) ua cov tshuaj ua ntej tau yuav los ntawm Acros Organics, Geel, Belgium. Tsis tas li ntawd, ethanol tag nrho (EA, C2H5OH) thiab sodium lauryl sulfate (SLS, C12H25NaO4S) tau yuav los ntawm Daejung Chemical & Metals Co., Ltd, Gyeonggi-do, Kaus Lim Qab Teb, thiab tau siv ua cov kuab tshuaj thiab cov surfactants, raws li. Dej distilled kuj siv ua cov kuab tshuaj.
Cov SA sib txawv tau sib xyaw nrog cov feem sib txawv ntawm sodium lauryl sulfate (SLS) hauv 100 mL dej distilled siv lub tshuab sib nqus stirrer ntawm 800 rpm thiab 75 ° C rau 1 teev (Rooj 1). Cov SA emulsions tau muab faib ua ob pawg: (1) 5, 10 thiab 15 g ntawm SA tau sib xyaw nrog 0.10 g ntawm SLS hauv 100 ml dej distilled (SATEOS1, SATEOS2 thiab SATEOS3), (2) 20, 30 thiab 50 g ntawm SA tau sib xyaw nrog 0.15, 0.20 thiab 0.25 g ntawm SLS tau sib xyaw nrog 100 ml dej distilled (SATEOS4, SATEOS5 thiab SATEOS6). 0.10 g SLS tau siv nrog 5, 10 thiab 15 g SA los tsim cov emulsions sib xws. Tom qab ntawd, nws tau pom zoo kom nce tus lej ntawm SLS rau SATEOS4, SATEOS5 thiab SATEOS6. Rooj 1 qhia txog qhov sib piv ntawm CA thiab SLS siv los tau txais cov tshuaj emulsion ruaj khov.
Muab 10 ml TEOS, 10 ml ethanol (EA) thiab 20 ml dej distilled rau hauv lub beaker 100 ml. Txhawm rau kawm txog kev ua haujlwm ntawm cov khoom sib txawv ntawm SA thiab SiO2 plhaub, cov coefficient synthesis ntawm txhua tus qauv tau sau tseg. Cov khoom sib xyaw tau do nrog lub tshuab sib nqus stirrer ntawm 400 rpm thiab 60 ° C rau 1 teev. Cov tshuaj precursor tom qab ntawd tau ntxiv rau hauv cov emulsion SA uas tau npaj tseg, do kom zoo ntawm 800 rpm thiab 75 ° C rau 2 teev, thiab lim kom tau txais cov hmoov dawb. Cov hmoov dawb tau ntxuav nrog dej distilled kom tshem tawm cov seem SA thiab ziab hauv lub qhov cub nqus tsev ntawm 45 ° C rau 24 teev. Yog li ntawd, tau txais SC microencapsulated nrog lub plhaub ntawm SiO2. Tag nrho cov txheej txheem ntawm kev tsim thiab kev npaj ntawm microencapsulated SA tau qhia hauv Daim Duab 1.
Cov microcapsules SA nrog lub plhaub SiO2 tau npaj los ntawm txoj kev sol-gel, thiab lawv cov txheej txheem encapsulation tau qhia hauv Daim Duab 2. Kauj ruam thawj zaug suav nrog kev npaj SA emulsion hauv cov kua dej nrog SLS ua surfactant. Hauv qhov no, qhov kawg hydrophobic ntawm SA molecule khi rau SLS, thiab qhov kawg hydrophilic rau cov dej molecules, tsim cov emulsion ruaj khov. Yog li, cov hydrophobic moieties ntawm SLS tau tiv thaiv thiab npog qhov chaw ntawm SA droplet. Ntawm qhov tod tes, hydrolysis ntawm TEOS cov kua tshwm sim qeeb los ntawm cov dej molecules, ua rau muaj hydrolyzed TEOS nyob rau hauv lub xub ntiag ntawm ethanol (Daim Duab 2a) 49,50,51. Hydrolyzed TEOS dhau los ntawm qhov kev sib xyaw ua ke, thaum lub sijhawm uas n-hydrolyzed TEOS tsim silica clusters (Daim Duab 2b). Cov silica clusters tau encapsulated los ntawm SA52 nyob rau hauv lub xub ntiag ntawm SLS (Daim Duab 2c), uas yog hu ua microencapsulation txheej txheem.
Daim duab kos ntawm microencapsulation ntawm CA nrog lub plhaub ntawm SiO2 (a) hydrolysis ntawm TEOS (b) condensation ntawm hydrolyzate thiab (c) encapsulation ntawm CA nrog lub plhaub ntawm SiO2.
Kev tshuaj xyuas tshuaj ntawm cov SA loj thiab cov SA me me tau ua tiav los ntawm kev siv Fourier transform infrared spectrometer (FT-IR, Perkin Elmer UATR Two, USA) thiab cov spectra tau kaw cia rau hauv qhov ntau ntawm 500 txog 4000 cm-1.
Ib lub tshuab X-ray diffractometer (XRD, D/MAX-2500, Rigaku, Nyiv Pooj) tau siv los tshuaj xyuas cov theem SA loj thiab cov khoom siv microcapsule. Kev tshuaj xyuas cov qauv X-ray tau ua tiav hauv qhov ntau ntawm 2θ = 5°–95° nrog qhov ceev ntawm 4°/min, siv hluav taws xob Cu-Kα (λ = 1.541 Å), cov xwm txheej ua haujlwm ntawm 25 kV thiab 100 mA, hauv hom kev tshuaj xyuas tas mus li. Cov duab X-ray tau tsim hauv qhov ntau ntawm 2θ = 5–50°, vim tias tsis muaj qhov siab tshaj plaws tau pom tom qab 50° hauv txhua qhov qauv.
Kev ntsuas X-ray photoelectron spectroscopy (XPS, Scienta Omicron R3000, Tebchaws USA) tau ua tiav siv Al Kα (1486.6 eV) ua qhov chaw X-ray kom nkag siab txog lub xeev tshuaj lom neeg ntawm cov SA loj nrog rau cov ntsiab lus uas muaj nyob hauv cov khoom siv encapsulation. Cov XPS spectra uas tau sau tau raug calibrated rau C 1s peak siv exotic carbon (binding energy 284.6 eV). Tom qab kho keeb kwm yav dhau los siv txoj kev Shirley, cov peaks siab daws teeb meem ntawm txhua lub ntsiab lus tau deconvoluted thiab haum rau Gaussian / Lorentzian functions siv CASA XPS software.
Cov morphology ntawm bulk SC thiab microencapsulated SC tau kuaj xyuas siv scanning electron microscopy (SEM, MIRA3, TESCAN, Brno, Czech Republic) nruab nrog lub zog-dispersive X-ray spectroscopy (EDS) ntawm 15 kV. Ua ntej SEM imaging, cov qauv tau coated nrog platinum (Pt) kom tsis txhob muaj kev cuam tshuam them.
Cov khoom siv thermal (qhov chaw yaj/kho thiab cua sov latent) thiab kev ntseeg tau (kev voj voog thermal) tau txiav txim siab los ntawm kev ntsuas calorimetry sib txawv (DSC, TA Instrument, Discovery DSC, Newcastle, USA) ntawm tus nqi cua sov/txias ntawm 10 °C/feeb ntawm 40 °C. thiab 90 °C nrog kev ntxuav nitrogen tas mus li. Kev tshuaj xyuas qhov hnyav tau ua tiav siv lub TGA analyzer (TA Instrument, Discovery TGA, New Castle, USA) hauv kev ntws tas mus li ntawm nitrogen pib ntawm qhov kub ntawm 40–600 °C, nrog tus nqi cua sov ntawm 10 °C/feeb.
Daim Duab 3 qhia txog FTIR spectra ntawm bulk SC thiab microencapsulated SC (SATEOS1, SATEOS2, SATEOS3, SATEOS4, SATEOS5 thiab SATEOS6). Cov ncov absorption ntawm 2910 cm-1 thiab 2850 cm-1 hauv txhua qhov qauv (SA thiab microencapsulated SA) yog vim muaj kev co ntawm cov pawg –CH3 thiab –CH2, feem 10,50. Lub ncov ntawm 1705 cm-1 sib raug rau kev co ntawm C=O bond. Cov ncov ntawm 1470 cm-1 thiab 1295 cm-1 yog vim muaj kev co ntawm cov –OH functional group, thaum cov ncov ntawm 940 cm-1 thiab 719 cm-1 sib raug rau kev co ntawm cov –OH functional group thiab cov yield. -plane deformation vibration, feem 10,50. Cov ncov nqus ntawm SA ntawm 2910, 2850, 1705, 1470, 1295, 940 thiab 719 cm-1 kuj tau pom nyob rau hauv txhua qhov microencapsulated SA. Tsis tas li ntawd, qhov ncov tshiab pom ntawm 1103 cm-1 sib raug rau qhov antisymmetric stretching vibration ntawm Si-O-Si band tau pom nyob rau hauv SA microcapsule. Cov txiaj ntsig FT-IR yog sib xws nrog Yuan et al. 50 Lawv tau ua tiav npaj microencapsulated SA hauv ammonia / ethanol piv thiab pom tias tsis muaj kev sib cuam tshuam tshuaj tshwm sim ntawm SA thiab SiO2. Cov txiaj ntsig ntawm kev tshawb fawb FT-IR tam sim no qhia tau hais tias SiO2 plhaub tau ua tiav encapsulated SA (core) los ntawm cov txheej txheem condensation thiab polymerization ntawm hydrolyzed TEOS. Ntawm cov ntsiab lus SA qis dua, qhov siab tshaj plaws ntawm Si-O-Si band yog siab dua (Daim duab 3b-d). Thaum tus nqi ntawm SA nce mus txog ntau dua 15 g, qhov muaj zog ntawm lub ncov thiab qhov dav ntawm Si-O-Si band maj mam txo qis, qhia txog kev tsim ntawm ib txheej nyias ntawm SiO2 ntawm qhov chaw ntawm SA.
FTIR spectra ntawm (a) SA, (b) SATEOS1, (c) SATEOS2, (d) SATEOS3, (e) SATEOS4, (f) SATEOS5 thiab (g) SATEOS6.
Cov qauv XRD ntawm cov SA loj thiab cov SA me me tau qhia nyob rau hauv Daim Duab 4. Cov ncov XRD nyob ntawm 2θ = 6.50° (300), 10.94° (500), 15.46° (700), 20.26° \((\overline {5} raws li JCPDS No. 0381923, 02)\), 21.42° hauv txhua qhov qauv (311), 24.04° (602) thiab 39.98° (913) tau muab faib rau SA. Kev cuam tshuam thiab kev sib xyaw nrog CA loj vim muaj cov yam tsis paub meej xws li surfactant (SLS), lwm yam khoom seem thiab microencapsulation ntawm SiO250. Tom qab encapsulation tshwm sim, qhov muaj zog ntawm cov ncov tseem ceeb (300), (500), (311), thiab (602) maj mam txo qis piv rau CA loj, qhia txog kev txo qis hauv crystallinity ntawm cov qauv.
Cov qauv XRD ntawm (a) SA, (b) SATEOS1, (c) SATEOS2, (d) SATEOS3, (e) SATEOS4, (f) SATEOS5 thiab (g) SATEOS6.
Qhov muaj zog ntawm SATEOS1 txo qis dua piv rau lwm cov qauv. Tsis muaj lwm cov ncov tau pom nyob rau hauv txhua cov qauv microencapsulated (Daim Duab 4b-g), uas lees paub tias kev nqus ntawm SiO252 es tsis yog kev sib cuam tshuam tshuaj lom neeg tshwm sim ntawm qhov chaw SA. Tsis tas li ntawd, nws kuj tau xaus lus tias microencapsulation ntawm SA tsis ua rau muaj cov qauv tshiab tshwm sim. SiO2 tseem nyob ruaj khov ntawm qhov chaw SA yam tsis muaj kev cuam tshuam tshuaj lom neeg, thiab thaum qhov ntau ntawm SA txo qis, cov ncov uas twb muaj lawm yuav pom tseeb dua (SATEOS1). Qhov tshwm sim no qhia tau tias SiO2 feem ntau encapsulates qhov chaw SA. Lub ncov ntawm (700) ploj mus tag, thiab lub ncov ntawm \((\overline{5}02)\) dhau los ua lub hump hauv SATEOS 1 (Daim Duab 4b), uas cuam tshuam nrog kev txo qis crystallinity thiab kev nce ntxiv amorphism. SiO2 yog amorphous nyob rau hauv xwm, yog li cov ncov pom los ntawm 2θ = 19 ° txog 25 ° muaj lub hump thiab broadening53 (Daim duab 4b-g), uas lees paub qhov muaj nyob ntawm amorphous SiO252. Qhov qis dua diffraction ncov zog ntawm microencapsulated SA yog vim qhov nucleation nyhuv ntawm silica sab hauv phab ntsa thiab qhov txwv crystallization tus cwj pwm49. Nws ntseeg tau tias nrog cov ntsiab lus SA qis dua, lub plhaub silica tuab dua yog tsim vim muaj ntau ntawm TEOS, uas feem ntau adsorbed rau ntawm qhov chaw sab nraud ntawm SA. Txawm li cas los xij, raws li qhov ntau ntawm SA nce, thaj chaw ntawm SA droplets hauv cov kua emulsion nce thiab ntau TEOS yog qhov xav tau rau kev encapsulation kom zoo. Yog li ntawd, nrog cov ntsiab lus SA siab dua, SiO2 ncov hauv FT-IR raug suppressed (Daim duab 3), thiab qhov muaj zog ntawm diffraction ncov ze 2θ = 19-25 ° hauv XRF (Daim duab 4) txo qis thiab kev nthuav dav kuj txo qis. Tsis pom. Txawm li cas los xij, raws li pom tau hauv Daim Duab 4, thaum twg qhov ntau ntawm SA nce ntxiv ntawm 5 g (SATEOS1) mus rau 50 g (SATEOS6), cov ncov siab yuav ze rau qhov loj ntawm SA, thiab qhov ncov siab ntawm (700) tshwm sim nrog txhua qhov siab tshaj plaws uas tau txheeb xyuas. Qhov tshwm sim no sib raug zoo nrog cov txiaj ntsig FT-IR, qhov twg qhov hnyav ntawm SiO2 SATEOS6 ncov txo qis ntawm 1103 cm-1 (Daim Duab 3g).
Cov xwm txheej tshuaj lom neeg ntawm cov ntsiab lus uas muaj nyob hauv SA, SATEOS1 thiab SATEOS6 tau qhia nyob rau hauv Daim Duab 1 thiab 2. Daim Duab 5, 6, 7 thiab 8 thiab Rooj 2. Kev ntsuas scans rau bulk SA, SATEOS1 thiab SATEOS6 tau qhia nyob rau hauv Daim Duab 5 thiab kev daws teeb meem siab scans rau C 1s, O 1s thiab Si 2p tau qhia nyob rau hauv Daim Duab 5, 6, 7 thiab 8 thiab Rooj 2. 6, 7 thiab 8 feem. Cov nqi zog khi tau los ntawm XPS tau muab tso ua ke hauv Rooj 2. Raws li tuaj yeem pom los ntawm Daim Duab 5, pom tseeb Si 2s thiab Si 2p peaks tau pom nyob rau hauv SATEOS1 thiab SATEOS6, qhov twg microencapsulation ntawm SiO2 plhaub tshwm sim. Cov kws tshawb fawb yav dhau los tau tshaj tawm txog Si 2s peak zoo sib xws ntawm 155.1 eV54. Qhov muaj Si peaks hauv SATEOS1 (Daim Duab 5b) thiab SATEOS6 (Daim Duab 5c) lees paub cov ntaub ntawv FT-IR (Daim Duab 3) thiab XRD (Daim Duab 4).
Raws li pom hauv Daim Duab 6 a, C 1s ntawm cov SA loj muaj peb lub ncov sib txawv ntawm CC, caliphatic, thiab O = C = O ntawm lub zog khi, uas yog 284.5 eV, 285.2 eV, thiab 289.5 eV, raws li. C – C, caliphatic thiab O = C = O cov ncov kuj tau pom hauv SATEOS1 (Daim Duab 6b) thiab SATEOS6 (Daim Duab 6c) thiab tau muab tso ua ke hauv Rooj 2. Ntxiv rau qhov no, C 1s ncov kuj sib xws rau lub ncov Si-C ntxiv ntawm 283 .1 eV (SATEOS1) thiab 283.5 eV (SATEOS6). Peb lub zog khi uas tau pom rau C – C, caliphatic, O = C = O thiab Si – C sib raug zoo nrog lwm qhov chaw 55,56.
Cov XPS spectra ntawm O 1 SA, SATEOS1 thiab SATEOS6 tau qhia nyob rau hauv Daim Duab 7a-c, raws li. Lub O 1s ncov ntawm bulk SA yog deconvoluted thiab muaj ob lub ncov, uas yog C = O / C - O (531.9 eV) thiab C - O - H (533.0 eV), thaum O 1 ntawm SATEOS1 thiab SATEOS6 yog sib xws. muaj tsuas yog peb lub ncov: C = O / C - O, C - O - H thiab Si - OH 55, 57, 58. Lub zog khi O 1s hauv SATEOS1 thiab SATEOS6 hloov me ntsis piv rau bulk SA, uas yog cuam tshuam nrog kev hloov pauv hauv cov tshuaj lom neeg vim muaj SiO2 thiab Si-OH hauv cov khoom siv plhaub.
Cov Si 2p XPS spectra ntawm SATEOS1 thiab SATEOS6 tau qhia nyob rau hauv Daim Duab 8a thiab b, raws li. Hauv cov CA loj, Si 2p tsis tau pom vim tsis muaj SiO2. Lub ncov Si 2p sib raug rau 105.4 eV rau SATEOS1 thiab 105.0 eV rau SATEOS6, sib raug rau Si-O-Si, thaum lub ncov SATEOS1 yog 103.5 eV thiab lub ncov SATEOS6 yog 103.3 eV, sib raug rau Si-OH55. Si-O-Si thiab Si-OH peak sib haum hauv SATEOS1 thiab SATEOS6 tau qhia txog kev ua tiav microencapsulation ntawm SiO2 ntawm SA core surface.
Qhov morphology ntawm cov khoom siv microencapsulated yog qhov tseem ceeb heev, cuam tshuam rau kev yaj, kev ruaj khov, tshuaj lom neeg reactivity, flowability thiab lub zog 59. Yog li ntawd, SEM tau siv los piav qhia txog qhov morphology ntawm bulk SA (100 ×) thiab microencapsulated SA (500 ×), raws li pom hauv Daim Duab 9. Raws li tuaj yeem pom los ntawm Daim Duab 9a, lub SA block muaj lub duab elliptical. Qhov loj me ntawm cov khoom me me tshaj 500 microns. Txawm li cas los xij, thaum cov txheej txheem microencapsulation txuas ntxiv mus, qhov morphology hloov pauv ntau heev, raws li pom hauv Daim Duab 9 b-g.
Cov duab SEM ntawm (a) SA (×100), (b) SATEOS1, (c) SATEOS2, (d) SATEOS3, (e) SATEOS4, (f) SATEOS5 thiab (g) SATEOS6 ntawm ×500.
Hauv cov qauv SATEOS1, cov khoom me me quasi-spherical SiO2-qhwv SA nrog qhov chaw ntxhib tau pom (Daim Duab 9b), uas tej zaum yog vim hydrolysis thiab condensation polymerization ntawm TEOS ntawm qhov chaw SA, ua kom nrawm nrawm ntawm cov ethanol molecules. Yog li ntawd, cov khoom SiO2 tau tso thiab agglomeration tau pom52,60. Lub plhaub SiO2 no muab lub zog kho tshuab rau cov khoom me me microencapsulated CA thiab tseem tiv thaiv kev xau ntawm cov CA yaj ntawm qhov kub siab dua10. Qhov tshwm sim no qhia tau tias SA microcapsules uas muaj SiO2 tuaj yeem siv ua cov khoom siv khaws cia lub zog61. Raws li tuaj yeem pom los ntawm Daim Duab 9b, cov qauv SATEOS1 muaj kev faib tawm cov khoom me me nrog cov txheej SiO2 tuab encapsulating SA. Qhov loj me ntawm cov khoom me me ntawm microencapsulated SA (SATEOS1) yog kwv yees li 10–20 μm (Daim Duab 9b), uas yog me dua piv rau cov khoom loj SA vim yog cov ntsiab lus SA qis dua. Qhov tuab ntawm cov txheej microcapsule yog vim hydrolysis thiab condensation polymerization ntawm cov tshuaj precursor. Agglomeration tshwm sim ntawm cov koob tshuaj qis dua ntawm SA, piv txwv li txog li 15 g (Daim duab 9b-d), tab sis thaum cov koob tshuaj nce ntxiv, tsis pom agglomeration, tab sis pom cov khoom me me uas tau txhais meej (Daim duab 9e-g) 62.
Ntxiv mus, thaum qhov ntau ntawm SLS surfactant yog qhov ruaj khov, cov ntsiab lus SA (SATEOS1, SATEOS2 thiab SATEOS3) kuj cuam tshuam rau qhov ua haujlwm tau zoo, cov duab thiab qhov loj me ntawm cov khoom me me. Yog li, SATEOS1 tau pom tias muaj qhov me me ntawm cov khoom me me, kev faib tawm sib npaug thiab qhov chaw ntom ntom (Daim duab 9b), uas tau muab rau qhov xwm txheej hydrophilic ntawm SA txhawb nqa qhov nucleation thib ob nyob rau hauv qhov tsis tu ncua surfactant63. Nws ntseeg tau tias los ntawm kev nce cov ntsiab lus SA los ntawm 5 txog 15 g (SATEOS1, SATEOS2 thiab SATEOS3) thiab siv cov surfactant tas li, piv txwv li 0.10 g SLS (Rooj 1), qhov kev koom tes ntawm txhua lub khoom me me ntawm cov tshuaj surfactant molecule yuav txo qis, yog li txo qhov loj me ntawm cov khoom me me thiab qhov loj me ntawm cov khoom me me. Kev faib tawm ntawm SATEOS2 (Daim duab 9c) thiab SATEOS3 (Daim duab 9d) txawv ntawm kev faib tawm ntawm SATEOS 1 (Daim duab 9b).
Piv nrog SATEOS1 (Daim Duab 9b), SATEOS2 tau qhia txog cov qauv ntom ntom ntawm SA uas muaj microencapsulated thiab qhov loj ntawm cov khoom me me nce ntxiv (Daim Duab 9c). Qhov no yog vim muaj kev sib sau ua ke 49, uas txo qhov coagulation rate (Daim Duab 2b). Thaum qhov ntau ntawm SC nce nrog rau kev nce SLS, cov microcapsules pom tseeb, raws li pom hauv daim duab. Yuav ua li cas kev sib sau ua ke tshwm sim. Tsis tas li ntawd, Daim Duab 9e-g qhia tias txhua cov khoom me me yog cov duab kheej kheej thiab loj. Nws tau lees paub tias thaum muaj ntau ntawm SA, ib qho ntau ntawm silica oligomers tuaj yeem tau txais, ua rau muaj kev sib sau ua ke thiab encapsulation thiab yog li ntawd tsim cov microcapsules zoo-txhais49. Los ntawm cov txiaj ntsig SEM, nws yog qhov tseeb tias SATEOS6 tau tsim cov microcapsules sib xws piv rau qhov me me ntawm SA.
Cov txiaj ntsig ntawm lub zog dispersive X-ray spectroscopy (EDS) ntawm bulk SA thiab microcapsule SA tau nthuav tawm hauv Rooj 3. Raws li tuaj yeem pom los ntawm lub rooj no, cov ntsiab lus Si maj mam txo qis los ntawm SATEOS1 (12.34%) mus rau SATEOS6 (2.68%). Nce hauv SA. Yog li ntawd, peb tuaj yeem hais tias kev nce ntxiv ntawm SA ua rau kev txo qis ntawm kev tso SiO2 rau ntawm SA nto. Tsis muaj cov nqi sib xws rau cov ntsiab lus C thiab O hauv Rooj 3 vim yog kev tshuaj xyuas semi-quantitative ntawm EDS51. Cov ntsiab lus Si ntawm microencapsulated SA tau sib raug zoo nrog FT-IR, XRD thiab XPS cov txiaj ntsig.
Tus cwj pwm yaj thiab khov ntawm cov SA loj nrog rau microencapsulated SA nrog SiO2 plhaub tau qhia hauv Daim Duab 1 thiab 2. Lawv tau qhia hauv Daim Duab 10 thiab 11 feem, thiab cov ntaub ntawv thermal tau qhia hauv Rooj 4. Qhov kub yaj thiab khov ntawm microencapsulated SA tau pom tias txawv. Raws li qhov ntau ntawm SA nce, qhov kub yaj thiab khov nce thiab mus txog qhov tseem ceeb ntawm cov SA loj. Tom qab SA microencapsulation, phab ntsa silica nce qhov kub crystallization, thiab nws phab ntsa ua haujlwm ua lub hauv paus los txhawb kev sib txawv. Yog li ntawd, raws li qhov ntau ntawm SA nce, qhov kub yaj (Daim Duab 10) thiab khov (Daim Duab 11) kuj maj mam nce 49,51,64. Ntawm tag nrho cov qauv microencapsulated SA, SATEOS6 tau pom qhov kub yaj thiab khov siab tshaj plaws, ua raws li SATEOS5, SATEOS4, SATEOS3, SATEOS2, thiab SATEOS1.
SATEOS1 qhia qhov qis tshaj plaws melting point (68.97 °C) thiab qhov kub thiab txias solidification (60.60 °C), uas yog vim qhov me me ntawm cov khoom me me uas kev txav mus los ntawm SA cov khoom me me hauv cov microcapsules yog me heev thiab SiO2 plhaub tsim ib txheej tuab thiab yog li ntawd Core Material txwv tsis pub ncab thiab txav mus los49. Cov kev xav no muaj feem cuam tshuam nrog SEM cov txiaj ntsig, qhov twg SATEOS1 qhia qhov me me ntawm cov khoom me me (Daim duab 9b), uas yog vim qhov tseeb tias SA cov khoom me me raug kaw hauv thaj chaw me me ntawm cov microcapsules. Qhov sib txawv ntawm qhov kub thiab txias melting thiab solidification ntawm lub ntsiab pawg, nrog rau txhua SA microcapsules nrog SiO2 plhaub, yog nyob rau hauv qhov ntau ntawm 6.10–8.37 °C. Qhov tshwm sim no qhia tau hais tias microencapsulated SA tuaj yeem siv ua cov khoom siv khaws cia lub zog vim yog qhov zoo thermal conductivity ntawm SiO2 plhaub 65.
Raws li pom los ntawm Rooj 4, SATEOS6 muaj qhov enthalpy siab tshaj plaws ntawm txhua qhov microencapsulated SCs (Daim duab 9g) vim yog qhov encapsulation zoo uas SEM pom. Tus nqi ntim SA tuaj yeem suav tau siv kab zauv (1). (1) Los ntawm kev sib piv cov ntaub ntawv cua sov latent ntawm microencapsulated SA49.
Tus nqi R sawv cev rau qib encapsulation (%) ntawm microencapsulated SC, ΔHMEPCM,m sawv cev rau lub cua sov latent ntawm kev sib xyaw ntawm microencapsulated SC, thiab ΔHPCM, m sawv cev rau lub cua sov latent ntawm kev sib xyaw ntawm SC. Tsis tas li ntawd, kev ua haujlwm ntawm kev ntim khoom (%) yog suav ua lwm qhov tseem ceeb ntawm kev siv tshuab, raws li qhia hauv Equation (1). (2)49.
Tus nqi E sawv cev rau qhov ua tau zoo ntawm encapsulation (%) ntawm microencapsulated CA, ΔHMEPCM, s sawv cev rau qhov kub latent ntawm kev kho ntawm microencapsulated CA, thiab ΔHPCM, s sawv cev rau qhov kub latent ntawm kev kho ntawm CA.
Raws li tau pom hauv Rooj 4, qib ntim thiab kev ua haujlwm ntawm SATEOS1 yog 71.89% thiab 67.68%, raws li, thiab qib ntim thiab kev ua haujlwm ntawm SATEOS6 yog 90.86% thiab 86.68%, raws li (Rooj 4). Qauv SATEOS6 qhia txog qhov coefficient encapsulation siab tshaj plaws thiab kev ua haujlwm ntawm txhua lub microencapsulated SAs, qhia txog nws lub peev xwm thermal siab. Yog li ntawd, kev hloov pauv ntawm cov khoom khov mus rau kua xav tau ntau lub zog. Tsis tas li ntawd, qhov sib txawv ntawm qhov kub yaj thiab khov ntawm txhua lub microcapsules SA thiab bulk SA thaum lub sijhawm txias qhia tau hais tias lub plhaub silica raug txwv tsis pub nyob rau hauv qhov chaw thaum lub sijhawm microcapsule synthesis. Yog li, cov txiaj ntsig qhia tau hais tias thaum qhov ntau ntawm SC nce, qhov nrawm encapsulation thiab kev ua haujlwm maj mam nce (Rooj 4).
Cov kab TGA ntawm cov SA loj thiab cov microcapsule SA nrog lub plhaub SiO2 (SATEOS1, SATEOS3 thiab SATEOS6) tau qhia nyob rau hauv Daim Duab 12. Cov khoom siv thermal stability ntawm cov SA loj (SATEOS1, SATEOS3 thiab SATEOS6) tau muab piv rau cov qauv microencapsulated. Nws pom tseeb los ntawm daim duab TGA tias qhov hnyav poob ntawm cov SA loj thiab cov SA me qhia tau tias du thiab me ntsis txo qis los ntawm 40 ° C mus rau 190 ° C. Ntawm qhov kub no, cov SC loj tsis raug thermal decomposition, thaum cov SC microencapsulated tso tawm cov dej adsorbed txawm tias tom qab ziab ntawm 45 ° C rau 24 teev. Qhov no ua rau hnyav poob me ntsis,49 tab sis dhau qhov kub no cov khoom pib lwj. Ntawm cov ntsiab lus SA qis dua (piv txwv li SATEOS1), cov dej adsorbed ntau dua thiab yog li ntawd qhov hnyav poob txog li 190 ° C siab dua (inset hauv Daim Duab 12). Thaum qhov kub nce siab tshaj 190 °C, cov qauv pib poob qhov hnyav vim yog cov txheej txheem decomposition. Bulk SA pib decomposition ntawm 190 °C thiab tsuas yog 4% tseem nyob ntawm 260 °C, thaum SATEOS1, SATEOS3 thiab SATEOS6 khaws cia 50%, 20% thiab 12% ntawm qhov kub no, raws li. Tom qab 300 °C, qhov hnyav poob ntawm bulk SA yog kwv yees li 97.60%, thaum qhov hnyav poob ntawm SATEOS1, SATEOS3, thiab SATEOS6 yog kwv yees li 54.20%, 82.40%, thiab 90.30%, raws li. Nrog rau kev nce ntxiv ntawm cov ntsiab lus SA, cov ntsiab lus SiO2 txo qis (Rooj 3), thiab qhov nyias ntawm lub plhaub tau pom hauv SEM (Daim duab 9). Yog li, qhov hnyav poob ntawm microencapsulated SA qis dua piv rau bulk SA, uas yog piav qhia los ntawm cov khoom zoo ntawm SiO2 plhaub, uas txhawb nqa kev tsim ntawm cov txheej carbonaceous silicate-carbonaceous ntawm qhov chaw ntawm SA, yog li cais cov SA core thiab qeeb qeeb tso tawm ntawm cov khoom volatile tshwm sim10. Cov txheej char no tsim ib qho kev tiv thaiv lub cev thaum lub sijhawm thermal decomposition, txwv tsis pub hloov pauv ntawm cov molecules flammable mus rau hauv cov roj theem66,67. Ntxiv rau qhov no, peb kuj tuaj yeem pom cov txiaj ntsig poob phaus tseem ceeb: SATEOS1 qhia cov nqi qis dua piv rau SATEOS3, SATEOS6 thiab SA. Qhov no yog vim tias qhov ntau ntawm SA hauv SATEOS1 tsawg dua li hauv SATEOS3 thiab SATEOS6, qhov twg SiO2 plhaub tsim ib txheej tuab. Hauv kev sib piv, tag nrho qhov hnyav poob ntawm bulk SA ncav cuag 99.50% ntawm 415 ° C. Txawm li cas los xij, SATEOS1, SATEOS3, thiab SATEOS6 tau qhia tias lawv poob phaus 62.50%, 85.50%, thiab 93.76%, raws li qhov kub thiab txias, ntawm 415 °C. Qhov tshwm sim no qhia tau hais tias kev ntxiv TEOS ua rau SA puas tsuaj los ntawm kev tsim ib txheej SiO2 rau ntawm qhov chaw ntawm SA. Cov txheej no tuaj yeem tsim ib lub txheej tiv thaiv lub cev, thiab yog li ntawd kev txhim kho hauv kev ruaj khov ntawm microencapsulated CA tuaj yeem pom.
Cov txiaj ntsig ntawm kev ntseeg siab thermal ntawm bulk SA thiab cov qauv microencapsulated zoo tshaj plaws (piv txwv li SATEOS 6) tom qab 30 lub voj voog cua sov thiab txias ntawm DSC51,52 tau qhia hauv Daim Duab 13. Nws tuaj yeem pom tias bulk SA (Daim Duab 13a) tsis qhia qhov sib txawv ntawm qhov kub yaj. solidification thiab enthalpy tus nqi, thaum SATEOS6 (Daim Duab 13b) tsis qhia qhov sib txawv ntawm qhov kub thiab enthalpy tus nqi txawm tias tom qab 30th lub voj voog cua sov. thiab cov txheej txheem txias. Bulk SA tau qhia txog qhov melting point ntawm 72.10 °C, qhov kub solidification ntawm 64.69 °C, thiab qhov kub ntawm fusion thiab solidification tom qab thawj lub voj voog yog 201.0 J / g thiab 194.10 J / g, feem. Tom qab lub voj voog thib 30, qhov chaw yaj ntawm cov nqi no tau txo qis mus rau 71.24 ° C, qhov kub thiab txias khov tau txo qis mus rau 63.53 ° C, thiab tus nqi enthalpy txo qis 10%. Kev hloov pauv ntawm qhov kub thiab txias yaj thiab khov, nrog rau kev txo qis ntawm cov nqi enthalpy, qhia tias CA loj tsis txhim khu kev qha rau cov ntawv thov uas tsis yog microencapsulation. Txawm li cas los xij, tom qab microencapsulation zoo tshwm sim (SATEOS6), qhov kub thiab txias yaj thiab khov thiab cov nqi enthalpy tsis hloov pauv (Daim duab 13b). Thaum microencapsulated nrog SiO2 plhaub, SA tuaj yeem siv ua cov khoom hloov pauv theem hauv cov ntawv thov thermal, tshwj xeeb tshaj yog hauv kev tsim kho, vim nws qhov kub thiab txias yaj thiab khov zoo tshaj plaws thiab enthalpy ruaj khov.
Cov kab DSC tau txais rau cov qauv SA (a) thiab SATEOS6 (b) ntawm 1st thiab 30th cua sov thiab txias voj voog.
Hauv txoj kev tshawb fawb no, kev tshawb nrhiav txog microencapsulation tau ua tiav siv SA ua cov khoom siv tseem ceeb thiab SiO2 ua cov khoom siv plhaub. TEOS siv ua tus ua ntej los tsim ib txheej txhawb nqa SiO2 thiab ib txheej tiv thaiv ntawm SA nto. Tom qab ua tiav kev tsim cov microencapsulated SA, FT-IR, XRD, XPS, SEM thiab EDS cov txiaj ntsig tau qhia tias muaj SiO2. Kev tshuaj xyuas SEM qhia tau tias cov qauv SATEOS6 qhia txog cov khoom me me uas muaj cov plhaub SiO2 nyob ib puag ncig ntawm SA nto. Txawm li cas los xij, MEPCM nrog cov ntsiab lus SA qis dua qhia txog kev sib sau ua ke, uas txo qhov kev ua tau zoo ntawm PCM. Kev tshuaj xyuas XPS qhia txog qhov muaj Si-O-Si thiab Si-OH hauv cov qauv microcapsule, uas qhia txog kev nqus ntawm SiO2 ntawm SA nto. Raws li kev tshuaj xyuas kev ua haujlwm thermal, SATEOS6 qhia tau tias muaj peev xwm khaws cia cua sov zoo tshaj plaws, nrog rau qhov kub yaj thiab khov ntawm 70.37°C thiab 64.27°C, raws li, thiab cua sov latent ntawm kev yaj thiab khov ntawm 182.53 J/g thiab 160.12 J/g. G. raws li. Qhov ua tau zoo tshaj plaws ntawm kev ntim khoom ntawm SATEOS6 yog 86.68%. Kev tshuaj xyuas lub voj voog thermal TGA thiab DSC tau lees paub tias SATEOS6 tseem muaj kev ruaj khov thermal zoo thiab kev ntseeg siab txawm tias tom qab 30 qhov txheej txheem cua sov thiab txias.
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