Influence of pH and precipitation temperature on the structural characteristics of aluminium hydroxides prepared form nitrate aqueous solutions
| Autor: | Vollet, Dimas Roberto [UNESP], Donatti, Dario Antonio [UNESP], Domingos, Roberto Naves [UNESP], Camargo Jr., Hélio |
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| Přispěvatelé: | Universidade Estadual Paulista (UNESP), CNPq |
| Jazyk: | portugalština |
| Rok vydání: | 1996 |
| Předmět: | |
| Zdroj: | Scopus Repositório Institucional da UNESP Universidade Estadual Paulista (UNESP) instacron:UNESP |
| Popis: | Made available in DSpace on 2022-04-28T20:01:32Z (GMT). No. of bitstreams: 0 Previous issue date: 1996-12-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Aluminium Hydroxides were precipitated from Aluminium Nitrate and Ammonium Hydroxide, at the temperatures 64°C (hot) and 25°C (cold), under the pH conditions 5, 7 and 9. The samples were characterized by X-Ray Diffraction (XRD) and Differential Thermal Analysis (DTA). The hydroxide precipitated at pH 9 and 64°C is built up by pseudoboehmite and a minor share of others apparently amorphous hydroxides. The crystallinity of the hot yielded pseudoboehmite diminishes with the pH. The crystallite size was evaluated as about 40Å for the best crystallized sample. The cold precipitated product is apparently composed by amorphous or very poorly crystallized hydroxides. Upon heating, the cold precipitated hydroxides, and the low pH and hot precipitated hydroxide, release their structural water before the occurrence, about 430°C, of the transition of the pseudoboehmite to γ-alumina, and exhibit a shifting (towards low temperature side) and a broadening in the peak of the transition to α-alumina, which occurs at 1200°C in the pseudoboehmite pattern. The yielded pseudoboehmite peptized by HNO3 addition and gelified by evaporation in a critical concentration approximately 0.17gcm-3. Departamento de Física Inst. de Geociendas e Cie. Exatas UNESP, 13500-230 - Rio Claro - SP Iniciação Cientifica CNPq Departamento de Física Inst. de Geociendas e Cie. Exatas UNESP, 13500-230 - Rio Claro - SP |
| Databáze: | OpenAIRE |
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