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溶 凝 膠 法. 簡 介. 圖片轉載於 http://w ww.gaematech.co.kr/ sub2/sub2_main_02.html. 溶凝膠法的優缺點 優點 : (1) 均質性與高純度。 (2) 節省能源,減少蒸發的損失與空氣的汙染、 較純的樣品、避開相變、結晶的過程。 缺點: (1) 原料昂貴。 (2) 凝膠的收縮量大。 (3) 孔穴、氫氧基、碳。. 溶凝膠法主要過程 ( 以 SiO 2 為例 ) TMOS+ 水 + 醇 (a) 水解 (hydrolysis) 反應。 - PowerPoint PPT Presentation
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簡 介
圖片轉載於 http://www.gaematech.co.kr/ sub2/sub2_main_02.html
溶凝膠法的優缺點 優點:
(1) 均質性與高純度。(2) 節省能源,減少蒸發的損失與空氣的汙染、 較純的樣品、避開相變、結晶的過程。
缺點:(1) 原料昂貴。(2) 凝膠的收縮量大。(3) 孔穴、氫氧基、碳。
溶 凝 膠 法 的 過 程 與 原 理溶凝膠法主要過程 ( 以 SiO2為例 )TMOS+ 水 + 醇
(a) 水解 (hydrolysis) 反應。
(b) 縮合 (condensation) 反應。
Si
OR
OR
OR
RO + H2O Si OR
OR
HO + ROH
OR
Si
OR
O
OR
RO+Si
OR
OH
OH
RO Si
OR
OR
OR
HO Si
OR
OR
OR
+ H2O
(c) 多縮合反應 (polycondensation)
Si
OH
O
OH
HO Si
OH
OH
OH
+ 6(H2O)
+ 6Si(OH)4
Si
O
O
O
O Si
O
O
O
SiHO
OH
OHSi
OH
OHHO
Si OH
OH
HOSiHO OH
OH
Si
OH
OH
OH
Si
OH
OH
HO
聚合反應
單體 (monomer) 顆粒 (particle) 鏈狀結構 (chain)三維網狀結構(3D network)
不同環境下的聚合反應
(1) Far from gel point
(2) Near from gel point
(3) Gel point
(acid-catalyzed)
10nm
(base-catalyzed)
10nm
溶凝膠過程與溫度之關係
Effect of experimental condition on the gelling time
(1) pH value(2) temperature(3) molar ration of H2O:Si
(4) precursor molecules(5) volume ratio of ROH:H2O
(6) solvent and additive solvent gelling time (hrs)
Methanol FormamideDimethyl-formamideAcetonitrileDioxane
86282341
Effect of pH value on the structure of gel
Aging process
Flow Chart of the two methods used to vary the pore characteristics of the gel silica matrices
Drying
Stage 1 CRP
Falling rate period 1 FRP1
Falling rate period 2 FRP2
Densification
Hydrolysis of TEOS with LiNO3 solution and LiOH solution
Example of preparation of lithium containing gel
Infiltration of LiNO3/LiOH in SiO2 gel
a: polymerized/LiNO3 gelb: infiltrated/LiNO3 gelc: polymerized/LiOH geld: infiltrated/LiOH gel
TG curves for the gels
Experimental solidification temperature of LiNO3 gels
Cooling rate (oC/min)
Polymerized T(o
C) InfiltratedT
(oC)0.05 2.06.0
203199191
213208 182
* Melting point of LiNO3 is 254oC
Conductivities ((-cm)-1) of gels at 400oCpolymerized/LiNO3 gel 1.3x10-2
infiltrated/LiNO3 gel 8.0x10-4
polymerized/LiOH gel 1.5x10-5
infiltrated/LiOH gel 4.4x10-6
0.2Li2O-0.8SiO2 glass(350oC)
VO(i-OC3H7)3 or VOCl3
+ C2H5OH+ H2O + dilute HNO3
pH~2 stir 1 day at 65oC dark green color
60oC oven for 4 weeks
Dried gels dark green brown color
Preparation of V2O5 crystals through sol-gel
Heat treated in oxygen atmosphere to varies temperatures
brown color
VOCl3 prepared gel V2O5 crystal forms above 200oC
VO(i-OC3H7)3 prepared gel V2O5 crystal forms above 400oC
VOCl3 prepared gel
200oC
700oC
VO(i-OC3H7)3 prepared gel
400oC
700oC
Alumina gel
HydrolysisThe unhydrolyzed species [Al(OH2)6]+3 exist below pH 3.With increasing pH, [Al(OH2)6]+3 can be hydrolyzed extensively:[Al(OH2)6]+3+hH2O→ [Al(OH)h(OH2)6-h]+3-h+hH3O+ hH3O+ +hOH- →2hH2O
Condensation
Dimer trimer X
Chemical modified Aluminum Alkoxides
Al-tri-sec-butoxide Al(OC4H9)3 modified with -diketonesActeylactone (CH3COCH2COCH3, AcAcH)Benzoylacetone (CH3COCH2COC6H5, BzAcH)Ethyl acetoacetata (CH3COCH2COOC2H5, EAcAcH)
The stabilization of -diketones for Al-tri-sec-butoxide in the order BzAcH < AcAcH < EAcAcH
The Al2O3/BzAc gel film is the most stable in air and have the highest photosensitivity among Al2O3 gel films.
ORMOSILS (Organically Modified Silicates)
Si(OR)4+R2Si(OR)2+YR’Si(OC2H5)3
where R is alkyl group -CH3, R’ is alkylene group -(CH2)n
Y is organofunction group such as -(CH2)3NH2,
-(CH2)3NHCOONH2, -(CH2)3S(CH2)2CHO.
Application:
1. Thin film and coating
2. Monoliths
3. Powders, grains, and spheres
4. Fibers
5. Porous gels and Members
Some Systems have been studied1.SiO2, Al2O3, B2O3, ZrO2, TiO2, Nb2O5, V2O5, Fe2O3, P2O5, ZnO2. Binary : SiO2-Al2O3, Li2O-B2O3, P2O5-SiO2.3. Composite : CdS-SiO2, Pt-SiO2, organic-inorganic hybrids, dye(R6G)-doped hybrids4. Multi-component: BaTiO3, PbZrxTi(1-x)O3, (Pb(1-y)Lay)( ZrxTi(1-x))O3 ( 鐵電 ), YBa2Cu3O7
Some Metal-alkoxidesTEOS (Si(OC2H5)4, 1L, 98%, USD $291), TMOS (Si(OCH3)4), 100g, 98%, USD $100)TPT (Ti(OCH(CH3)2)4, 500ml, 97%, USD $52), TBZ ((Zr(OC4H9)4, 25g, 99%, USD $249),ASB (Al(OC4H9)3, 500g 97% USD $64),
End of Part One