An XRD, SEM and TG study of a uranopilite from Australia
A uranopilite from The South Alligator River, Northern Territory, Australia has been studied using X-ray diffraction, scanning electron microscopy with EDAX attachment and thermogravimetry in conjunction with evolved gas mass spectrometry. X-ray diffraction shows the mineral is a pure uranopilite with little or no impurities. SEM images show the uranopilite to consist of long elongated crystals up to 50 μm in length and 5 μm in width. Thermogravimetry combined with mass spectrometry shows that dehydration occurs around 31 degrees Celsius resulting in the formation of metauranopilite. The first dehydration step over 20 - 71 degrees Celsius corresponds to the decrease of 5.4 wt %, equivalent to 6.076 H2O. The second dehydration step over 71-162.4 degrees Celsius corresponds to a decrease of 4.7 wt % equivalent to 5.288 H2O making a total of 11.364 moles of H2O, close to 12 H2O for uranopilite.
Dehydroxylation takes place over the temperature range 80 to 160 degrees Celsius. The loss of sulphate occurs at higher temperatures in two steps at 622 and 636 degrees Celsius. A mass loss also occurs at 755 degrees Celsius accounted for by evolved oxygen.
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|Item Type:||Journal Article|
|Additional Information:||This manuscript is one of a series of papers by the author [Ray Frost] on uranyl secondary minerals.|
|Keywords:||Keywords, uranopilite, johannite, zippeite, uranyl sulphate minerals, thermal analysis, dehydroxylation, dehydration, mass spectrometry|
|Subjects:||Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000) > INORGANIC CHEMISTRY (030200)|
|Divisions:||Past > QUT Faculties & Divisions > Faculty of Science and Technology|
|Copyright Owner:||Copyright 2006 The Mineralogical Society|
|Copyright Statement:||Reproduced in accordance with the copyright policy of the publisher.|
|Deposited On:||10 Nov 2006|
|Last Modified:||29 Feb 2012 23:24|
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