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Thermal decomposition of rhombohedral KClO (sub 3) from 29-76 kilobars and implications from the molar volume of fluid oxygen at high pressures

Marie C. Johnson, David Walker, Simon M. Clark and Raymond L. Jones
Thermal decomposition of rhombohedral KClO (sub 3) from 29-76 kilobars and implications from the molar volume of fluid oxygen at high pressures
American Mineralogist (December 2001) 86 (11-12): 1367-1379

Abstract

KClO (sub 3) thermal decomposition has been studied from 29-76 kilobars using a multianvil high-pressure device and in-situ energy-dispersive X-ray diffraction and off-line quenching experiments. The rhombohedral form of KClO (sub 3) was found to decompose to the B2 form of KCl and O (sub 2) via an orthorhombic KClO (sub 4) intermediate over this pressure interval. The decomposition temperature was found to vary only slightly with pressure. The online experiments gave decomposition temperatures between 500 and 580 degrees C. Further off-line quenching experiments using sealed gold tubes determined the equilibrium decomposition boundary to be 500+ or -15 degrees C over this pressure range. Unit-cell parameters and volumes were determined for the high-pressure phases of KClO (sub 3) and KCl from the diffraction data. The partial molar volume of O (sub 2) was calculated from the difference in the solid volumes. Oxygen fluid volumes were then calculated along the decomposition boundary and vary from 10.6+ or -0.2 cm (super 3) /mol at 29 kbar to 9.6+ or -0.1 cm (super 3) /mol at 76 kbar. These volumes are 30 to 50% less than previous estimates determined from shock wave data, and imply that oxygen can be more easily stored in Earth's mantle and core than previously believed. The thermal equation of state of the B2 form of KCl was investigated online using NaCl as an internal pressure standard. KCl was then used as an internal pressure calibrant for the online KClO (sub 3) decomposition experiments. The mechanical behavior of the multianvil high-pressure device was also studied and load vs. force characteristics are presented here.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 86
Serial Issue: 11-12
Title: Thermal decomposition of rhombohedral KClO (sub 3) from 29-76 kilobars and implications from the molar volume of fluid oxygen at high pressures
Affiliation: United States Military Academy, Department of Geography and Environmental Engineering, West Point, NY, United States
Pages: 1367-1379
Published: 200112
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 26
Accession Number: 2002-012194
Categories: Geophysics of minerals and rocks
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables
Secondary Affiliation: Lamont-Doherty Earth Observatory, USA, United StatesCLRC Daresbury Laboratory, GBR, United Kingdom
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 200205
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