Nqus preservation Kev npaj ntawm gel

Nqus preservation Kev npaj ntawm gel

(1) Ntxiv ib qho nyiaj ntawm tetrabutyl titanate, anhydrous ethanol, dej thiab catalyst rau lub beaker, do ceev kom txog thaum lub gel tsim, thiab ces nws muaj hnub nyoog rau ob peb hnub. Tus nqi dej thiab pH tswj tuaj yeem sib txawv ntawm pawg. (2) Hloov cov dej seem thiab cov reagents nyob rau hauv cov gel nrog kiag li ethanol.

Qhov nro ntawm lub tshuab nqus tsev tsis muaj nyob rau hauv supercritical drying

Ntxiv surfactant kom qhuav yuav qhia impurities. Tam sim no, txoj kev ua tau zoo tshaj plaws los tshem tawm cov nyhuv ntawm cov kua nplaum saum npoo ntawm qhov kev puas tsuaj ntawm gel yog siv qhov kub thiab txias kom qhuav los yog tshem tawm cov kua hauv cov gel pores nyob rau hauv cov xwm txheej ntawm supercritical kua, uas yog, supercritical drying thiab supercritical ziab. Nyob rau hauv cov kua hauv lub xeev supercritical, cov roj-kua interface ploj, thiab qhov nro saum npoo tsis muaj nyob rau hauv supercritical ziab. Nyob rau lub sijhawm no, tsis muaj lub siab ntxiv uas tsim los ntawm qhov nro saum npoo ntawm capillary pores ntawm gel. Yog li ntawd, kom qhuav nyob rau hauv cov dej supercritical, tus thawj dispersion qauv ntawm cov gel yuav tsum tau khaws cia, yog li zam lub agglomeration thiab agglomeration ntawm cov ntaub ntawv los yog nanoparticles tshwm sim los ntawm muaj zog capillary contraction nyob rau hauv cov txheej txheem ziab ntawm cov pa kom qhuav cov tswv yim xws li chav tsev kub kom qhuav thiab ci kom qhuav. , tiv thaiv cov khoom siv yooj yim hais. Roughening, qhov poob qis hauv qhov tshwj xeeb thiab txo qhov porosity loj yog qhov tshwm sim.

Muaj kev sib raug zoo ntawm cov khoom nto ntawm lub tshuab nqus tsev preservation.

D.4 Cov duab siab zoo ntawm cov khoom ntshiab D.

Kev tshawb fawb Thermophysics ntawm cov kua dej qhia tau hais tias qhov nro ntawm cov kua dej muaj feem xyuam nrog qhov kub thiab txias raws li hauv qab no:

σ {{0}} σ 0 (1 T / TC )

Nyob rau hauv cov mis: σ — nto nro ntawm cov kua; σ0—— tus yam ntxwv tsis tu ncua muaj feem cuam tshuam rau kev sib cuam tshuam; TC yog qhov ntsuas kub tseem ceeb ntawm cov teeb meem. Thaum qhov kub ntawm lub kaw lus nce mus txog qhov ntsuas kub tseem ceeb (T=TC), raws li cov qauv saum toj no, qhov nro saum npoo zoo li xoom, qhia tias nyob rau hauv cov xwm txheej tseem ceeb, cov roj-kua theem cuam tshuam ploj thiab qhov nro ntawm qhov chaw. tso tseg. Ua ntej cov gel qhuav, cov qauv gel network tau ntim nrog kua hnyav. Nrog rau qhov ziab ntawm cov gel qhuav, tom qab cov kuab tshuaj yog ib nrab volatilized, cov kua pib tsim meniscus nyob rau hauv capillary pores ntawm lub gel network, uas ua rau lub siab ntxiv. p=2σ/r. Qhov loj ntawm gel capillary feem ntau yog 1 ~ 100nm. Yog hais tias lub vojvoog ntawm lub gel capillary yog 20nm, thaum muaj xws li ib tug muaj zog capillary contraction quab yuam tsim los ntawm lub nto nro ntawm cov kua ethanol, lub theoretical xam yuav dais txog lub siab. 2.3 Mpa ua. Lub capillary pore loj yog ntxiv txo, thiab lub siab ntxiv yog ntxiv, yog li ntawd cov hais ntxiv mus, aggregated thiab cog lus, thiab cov gel network qauv collapses. Yog li ntawd, nws yog ib qho nyuaj los tiv thaiv lub shrinkage thiab fragmentation ntawm cov gel los ntawm kev siv cov pa qhuav txheej txheem, thiab thaum kawg tsuas yog ib tug fragmented, nyuaj thiab loj-scale ntxeem tau xerogel.

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