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Changes in the Structure of Ulexite on Heating by Savaş Şener; Gülhan Özbayoǧlu; Şahinde Demirci is a Materials Science article available to read on EtoBox.

What is Changes in the Structure of Ulexite on Heating about?

On heating, hydrated boron minerals, colemanite and ulexite lose their water of crystallisation while undergoing various mineralogical and structural changes. In this study, the nature and mechanisms of the thermal reactions of ulexite have been determined by TG, DTG and DTA. The changes in the structure have been investigated by XRD, SEM, and Hg-porosimetry. Thermal decomposition of ulexite occurred within the temperature range 60±5008C with two dehydration stages proceeded by two dehydroxylation stages. The structure was ®rst transformed into NaCaB 5 O 6 (OH) 6 Á3H 2 O within 60±1808C, then into NaCaB 5 O 6 (OH) 6 ÁH 2 O within 151± 2608C. Amorphisation took place along with dehydroxylation. The structure was ®rst transformed into a multi-domain heterogeneous matrix consisting of NaCaB 5 O 6 (OH) 6 ÁH 2 O and an amorphous phase to X-ray during the ®rst stage of dehydroxylation within 180±2608C. Then remaining hydroxyl groups removed between 260 and 5008C. The sample has become completely X-ray amorphous. During the gradual liberation of water vapour, the structure developed numerous microcracks and had exfoliated without decrepitating. The microcracks increased the degree of poro

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Author

Savaş Şener; Gülhan Özbayoǧlu; Şahinde Demirci

Publisher

Elsevier Science; Elsevier ; Elsevier BV (ISSN 0040-6031)

Published

2000

Language

EN

Field

Materials Science (Physical Sciences)