کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4701430 1637770 2006 7 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Coesite (SiO2) as an extreme case of superheated crystal: An X-ray diffraction study up to 1776 K
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات ژئوشیمی و پترولوژی
پیش نمایش صفحه اول مقاله
Coesite (SiO2) as an extreme case of superheated crystal: An X-ray diffraction study up to 1776 K
چکیده انگلیسی

The dense SiO2 polymorph coesite has been investigated by X-ray powder diffraction from room temperature up to 1776 K. No phase transition has been detected in this temperature interval. Thermal expansion shows little anisotropy and remains very small since the volume increases by only 1.6% between 300 and 1776 K. As indicated by theoretical simulations, the small dilation results from limited rotations of SiO4 tetrahedra and also from slight expansion of Si–O bonds. In addition, the results demonstrate that coesite can be kept 900° above its metastable congruent temperature of fusion which is about 875 K. Comparisons with measurements made under the same conditions for quartz and cristobalite indicate that, for SiO2 polymorphs with 4-fold coordinated Si, crystal structure exerts a smaller influence than melt viscosity on the extent of superheating.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Chemical Geology - Volume 229, Issues 1–3, 16 May 2006, Pages 57–63
نویسندگان
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