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Evaluation of Nigerian Source of Kaolin as a Raw Material for Mullite Synthesis

Ajanaku, K. O. and Aladesuyi, O. and MOUSUMI, PAL and SWAPAN, KUMAR DAS (2016) Evaluation of Nigerian Source of Kaolin as a Raw Material for Mullite Synthesis. ORIENTAL JOURNAL OF CHEMISTRY, 32 (3). pp. 1571-1582. ISSN 0970-020 X

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In the present study, a new source of kaolinitic clay (Al2O3.2SiO2.2H2O) collected from Abule Onikosin Road in Abeokuta area of Ogun State, Nigeria was first processed to remove the stony materials adhered to its surface and subsequently characterized with respect to its chemical analysis, TG-DTA, particle size spectrum and identification of mineralogical phases by XRD technique. The identified endothermic peak at 516.39oC for dehydroxylation in the DTA curve and observed deformed XRD profile confirm that the clay belongs to disordered kaolinitic clay. The high SiO2 content (59.26 wt%) compared to theoretical value (46.54 wt%) of well-ordered kaolinite is due to excess silica and this has been revealed in XRD pattern as quartz peak. The compact samples of this processed clay powder on heating in the temperature range of 1400-1600oC resulted almost densified and impervious sample at 1600oC. The densification occurred by viscous flow mechanism. Silica together with impurity oxides (Fe2O3, TiO2) in the clay forms glassy phase in the above temperature range and that accompany the formation of mullite (3Al2O3.2SiO2) crystals. The XRD and FESEM studies conducted on heated samples revealed the formation of mullite needle, the amount and aspect ratio of which increases with increase in heating temperature. The EDAX studies confirm the presence of Al, Si, O as major elements which also support mullite formation in the heated compact samples. This new sources of kaolinitic clay identified in Nigeria is found to be suitable for mullite synthesis and it is advantageous due to its low temperature mullitization unique microstructure.

Item Type: Article
Uncontrolled Keywords: Kaolinite, disordered structure, mullite, TG-DTA, phase transformation, sintering.
Subjects: Q Science > Q Science (General)
Q Science > QD Chemistry
Divisions: Faculty of Engineering, Science and Mathematics > School of Chemistry
Depositing User: Mrs Hannah Akinwumi
Date Deposited: 14 Dec 2016 11:44
Last Modified: 14 Dec 2016 11:44

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