Kinetics of sintering of polyethilene glycol and lanthanum doped aluminum oxide obtained by the sol-gel method
| Autor: | S Ljiljana Rozic, B Tatjana Novakovic, P Srdjan Petrovic, M Zorica Vukovic |
|---|---|
| Jazyk: | srbština |
| Rok vydání: | 2011 |
| Předmět: |
Boehmite
Materials science General Chemical Engineering Inorganic chemistry Sintering chemistry.chemical_element 02 engineering and technology Polyethylene glycol lcsh:Chemical technology 010402 general chemistry 01 natural sciences law.invention chemistry.chemical_compound Lanthanum oxide aluminum-oxide law Specific surface area Lanthanum sol-gel lcsh:TP1-1185 Crystallization Sol-gel sintering General Chemistry 021001 nanoscience & nanotechnology 0104 chemical sciences lanthanum oxide chemistry Chemical engineering polyethylene glycol aluminumoxide 0210 nano-technology |
| Zdroj: | Hemijska industrija (2011) 65(4):355-362 Hemijska Industrija, Vol 65, Iss 4, Pp 355-362 (2011) |
| ISSN: | 0367-598X |
| Popis: | Sintering and crystallization of low-density polyethylene glycol (PEG) and lanthanum, La(III)-doped Al2O3 aerogels prepared from aluminum isopropoxide were investigated. The sintering behavior of non-doped and doped aerogels was examined by following the change of specific surface area with isothermal heat-treatment. The specific surface area and crystalline phases of non-doped and PEG+La(III)-doped aerogels were determined, and the effects of dopants on the sintering and crystallization of Al2O3 aerogels are discussed. Isothermal sintering experiments showed that the sintering mechanism of non-doped and PEG+La(III)-doped Al2O3 aerogels is surface diffusion. The specific surface areas of alumina samples decrease rapidly during the initial period of sintering, and more slowly with prolonged sintering time. The change of the porous structure is correlated with the phase transformation of γ-Al2O3 during calcinations of Al2O3 aerogels. The surface area of non-doped Al2O3 aerogels came to about 20 m2g-1 with heat-treatment at 1100°C because of crystallization of α-Al2O3 after densification. In the case of heattreatment at 1200°C, the largest surface area was observed for PEG+La(III) doped Al2O3 aerogels and the XRD pattern showed only low ordered θ-Al2O3. These indicate that the addition of PEG+La(III) to boehmite sol prevents Al2O3 aerogels from sintering and crystallizing to the α-Al2O3 phase. Even after 20 h at 1000°C, PEG+La (III)-doped alumina samples maintain a rather good specific surface area (108 m2 g-1) in comparison to the non-doped, containing mainly θ-Al2O3 and minor amounts of δ-Al2O3. Aluminum-oxides with these structural and textural properties are widely used as a coatings and catalyst supports in the field of various catalysis. |
| Databáze: | OpenAIRE |
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