The Meta-Stable Region for the η-Spinel Solid Solution
| Autor: | Kouhei Shirasuka, Goro Yamaguchi, Kazuyoshi Takahashi |
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| Rok vydání: | 1974 |
| Předmět: | |
| Zdroj: | Journal of the Ceramic Association, Japan. 82:393-396 |
| ISSN: | 1884-2127 0009-0255 |
| DOI: | 10.2109/jcersj1950.82.947_393 |
| Popis: | The defective spinel in the system RO⋅Al2O3-Al2O3 at the lower temperature below about 1100°C, was synthesized, and it was named as γ-spinel and its meta-stable region was explanatorily draw by G. Yamaguchi in 1953.In the present investigation, this phase boundary has been revealed experimentally by the X-ray diffraction procedures and the differential thermal analysis, and this defective spinel has been termed η-spinel according to the common nomenclature of the γ alumina group in which an alumina phase with the spinel symmetry is called as η alumina.These η-spinel solid solution were synthesized from mixtures of the gibbsite Al(OH)3 and the magnesium nitrate Mg(NO3)2⋅6H2O aqueous solution.The lattice parameters of all specimens quenched from 1150°C continuously varied from the stoichiometric composition of 50MgO:50Al2O3 to δ, γ orη alumina, while the specimens of 10MgO:90Al2O3 and 30MgO:70Al2O3 quenched from 1200°C and 1280°C, respectively, deviated from this continuous change. Simultaneously, in these specimens the α alumina phase exsoluted from these meta-stable solid solutions was observed (Fig. 1 & Fig. 2).The starting point of the exsolution was decided on the intersection of the base line and the tangential line of the inflection point of the exothermic peak in the differential thermal analysis (Fig. 3 & Table 1).The results of the X-ray diffraction fairly coincided with those of the differential thermal analysis. Consequently, the upper limit phase boundary of the meta-stable region for the η-spinel solid solution was decided on the system MgO⋅Al2O3-Al2O3 (denoted as the broken line in Fig. 4). |
| Databáze: | OpenAIRE |
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