Abstract
The differences of the thermal curves (DTA-TG) of pyrophyllite measured before and after grinding have been studied to obtain quantitative information about the alteration of the structure of this layer silicate.
The mechanical treatment by dry grinding of pyrophyllite produces a decrease in the particle size of the original material. This strongly influences the thermal behaviour of weight losses on the TG curves decrease, and the endothermic DTA effects shift to lower temperatures, until the mechanochemical limit in particle size reduction is reached.
Further grinding produces a disruption of the 2∶1 aluminosilicate structure giving an exothermic DTA effect, and also reagglomeration processes of the amorphous and activated material accompanied by a decrease in specific surface area.
Zusammenfassung
Es wurden vergleichbare Änderungen an thermischen Kurven (DTA, TG) von Pyrophyllit vor und nach Zerkleinerung untersucht, um quantitative Angaben über die Änderung dieses Schichtensilikates zu erhalten.
Durch die mechanische, trockene Zerkleinerung von Pyrophyllit kam es gegenüber dem Ausgangsmaterial zu einer Abnahme der Partikelgröße. Durch diesen Umstand wird das thermische Verhalten des erhaltenen Produktes stark beeinflußt. Bis zum Erreichen der mechanochemischen Grenze der Minderung der Partikelgröße nehmen in den TG-Kurven die Temperaturen für die Massenverluste ab, und die endothermen DTA-Effekte werden zu niedrigeren Temperaturen verschoben.
Weiteres Zerkleinern führt zu einer Störung der 2∶1-Aluminosilikatstruktur, was einen exothermen DTA-Effekt verursacht, sowie auch zu Reagglomeration des sehr amorphen und aktivierten Materiales, begleitet von einer Minderung des spezifischen Oberfläche.
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Dedicated to Professor Dr. H. J. Seifert on the occasion of his 60th birthday
The authors thank Professors J. Sanz and J. M. Trillo for their valuable discussions of some aspects of this paper, and Mr. E. Gomez-Asensio for technical assistance in the SEM work.
Thanks are extended to the Ministerio of Educacion y Ciencia for a grant to one of the authors (Pedro José Sánchez Soto) which enabled him to make this research.
This paper was made possible through the financial support of the CICYT, research number GEO90-0060.
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Rodriguez, J.L.P., Soto, P.J.S. The influence of the dry grinding on the thermal behaviour of pyrophyllite. Journal of Thermal Analysis 37, 1401–1413 (1991). https://doi.org/10.1007/BF01913477
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DOI: https://doi.org/10.1007/BF01913477