Influence of thermal treatment on the water release and the glassy structure of perlite
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The effect of slow and rapid thermal treatment on water release and the structure of perlite was investigated by employing complementary techniques including X-ray diffraction, infrared spectroscopy and scanning electron microscopy. The study of several perlite samples, with different grain size and origin, has shown that rapid heating has a more pronounced effect on the glassy structure and that this is the only process capable of leading to perlite grain expansion. This process was simulated in a laboratory furnace allowing the careful control of temperature and time of treatment, and, thus, the description of their influence on the expansion process. The results show that molecular water released between 250 and 550 °C affects mostly the expansion process. Infrared spectroscopy provides evidence for additional water release, through dehydroxylation of Si–OH bonds, that may contribute also to expansion with a simultaneous development of the silicate network. The grain morphology was found to correlate with the expansion ratio. The presence of crystallites in raw perlite was shown to affect also the expansion process.
KeywordsExpansion Ratio Expansion Process Grain Morphology Molecular Water Heat Treatment Time
This work was supported in part by the Greek General Secretariat for Research and Technology. Dr Y.D. Yiannopoulos is gratefully acknowledged for his help with infrared studies at NHRF.
- 4.Zahringer K, Martin J-P, Petit J-P (2001) Glass Sci Technol 74:57Google Scholar
- 5.Papanastassiou D (1980) J Trans Inst Min Metall (Sect C: Mineral Process Extr Metall) 89:120Google Scholar
- 10.Tarasevich YI, Verlinskaya RM, Nesterova MP, Gornitskii AB (1986) Khimiya I Tekhnologiya Vody 8:34Google Scholar
- 11.Tarasevich YI, Panasevich AA, Bezorudko OV, Skrylev LD, Purich AA (1985) Khimiya I Tekhnologiya Vody 7:67Google Scholar
- 22.Lehmann H, Rössler M (1974) Therm Anal 1:619Google Scholar
- 26.Kamitsos EI, Patsis AP and Kordas G (1993) Phys Rev B 48:12499; Kamitsos EI (1996) Phys Rev B 53:14659Google Scholar
- 27.Ingram MD, Davinson JE, Coats AM, Kamitsos EI, Kapoutsis JA (2000) Glastech Ber Glass Sci Technol 73:89Google Scholar