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Study on Preparation of Al 2 O 3 aerogels dried at ambient pressure

Author: HuangBao
Tutor: LiJie
School: Central South University
Course: Physical Chemistry of Metallurgy
Keywords: AlCl3.6H2O Alumina airgel Sol - gel method Ambient Pressure Drying
CLC: TB383.1
Type: Master's thesis
Year: 2008
Downloads: 391
Quote: 2
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Abstract


AlCl 3 .6 H 2 O as the precursor by the sol - gel technique, ethanol and water mixture to the reaction system, add propylene oxide inducing agent for the gel network, carboxamide dry chemical control additives, the use of anhydrous ethanol solution containing TEOS soaked gel, dried over anhydrous ethanol gel processes such as solvent substitution was successfully prepared under atmospheric conditions white, light, block precursor of alumina - aluminum hydroxide airgel, after calcination at 500 ℃ alumina airgel. The thesis epoxy propane, ethanol, water and formamide preparation parameters specific surface area of ??the airgel, and by orthogonal experiment to determine the optimal reaction ratio of n (Al): n (propylene oxide) : n (ethanol): n (water): n (carboxamide) = 1:8:8:20:0.8. Airgel density is prepared under the conditions 1 38kg / m 3 , the specific surface area of ??560m 2 / g, a pore volume of 1.982cm 3 < / sup> / g; micro-org is the length for the 10 to 100 nm, a width of 2 to about 5 nm, an elongated particle crosslinking is formed between having a unique three-dimensional spatial network structure. The precursor airgel prepared high-temperature calcination process, successfully prepared γ-Al 2 O 3 aerogels after calcination at 500 ℃, with 423m < sup> 2 / g specific surface area, 1.638cm 3 / g of pore volume and the concentrated distribution in pore size of about 20nm; the airgel skeleton comprises an elongate, The one-dimensional line width of about 25nm interwoven three-dimensional network structure. Anhydrous ethanol solution containing TEOS soak gel, the gel structure containing the SiO 2 , the SiO 2 of the presence of suppressed Al 2 O 3 of sintering and phase transition; On the one hand is ethyl silicate and Al 2 O 3 surface hydroxyl condensation reaction, on the other hand the Al 2 O 3 surface hydroxyl group substituted by Si-OH is difficult to move, generated by Si-O-Al or Si-O-Si key firmly embedded in the γ-Al 2 O 3 surface, inhibiting the formation of the inter-particle sintering neck, which makes the airgel has a high temperature anti-sintering and high temperature anti-phase-change performance, after calcined at 1000 ℃ still has a high specific surface area (122m 2 / g) and large pore volume (0.564cm 3 / g). The directly added different amounts of silicon by sol preparation stage Aerogels process simplify the exploration and study. Studies have found that adding a silicon content of 10% may be prepared by a better performance of the airgel products; alumina airgel having a specific surface area of ??289m 2 / g after 500 ° C calcination prepared and The 1.127cm 3 / g pore volume. TEOS / anhydrous ethanol mixed solution soak process resulting airgel products compared to simplify the process for preparing the airgel products on the performance of the specific surface area, pore volume to be much worse, optimum conditions to be explored further.

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