کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
9594944 | 1507978 | 2005 | 11 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Epitaxial growth of celestite on barite (0Â 0Â 1) face at a molecular scale
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
شیمی
شیمی تئوریک و عملی
پیش نمایش صفحه اول مقاله
![عکس صفحه اول مقاله: Epitaxial growth of celestite on barite (0Â 0Â 1) face at a molecular scale Epitaxial growth of celestite on barite (0Â 0Â 1) face at a molecular scale](/preview/png/9594944.png)
چکیده انگلیسی
In situ AFM experiments have been conducted in order to obtain information about kinetics of celestite epitaxial growth on barite. Growth has been promoted by passing aqueous solutions supersaturated with respect to celestite over freshly cleaved barite (0 0 1) surfaces. Solution supersaturation, βcelestite, was varied from 1 to 45.7 (βcelestite=a(Sr2+)·a(SO42-)/Ksp,cel). At supersaturations below 10 neither two-dimensional nucleation neither step advancement are observed on barite (0 0 1) surfaces. However, once the two-dimensional nucleation barrier is overcome (βcelestite > 10), nuclei preferentially form on cleavage steps parallel to [1 0 0], [1 1 0] and [1 2 0] directions and more scarcely on terraces. The subsequent growth of two-dimensional nuclei leads to the development of celestite “islands”. Their morphology is defined by (0 0 1) face and {2 1 0} and {1 0 0} forms and can be explained on the basis of PBC theory. The coalescence of such islands results in the formation of a homogeneous SrSO4 layer. Growth rates along [0 0 1] direction have been measured for the whole supersaturation range. The growth rate equation for “Birth and Spread” crystal growth mechanism has been successfully fitted to our experimental data. The fitting process has provided basic growth parameters in a good agreement with theoretical ones. Both the high transitional supersaturation required for two-dimensional nucleation and the high interfacial energy value obtained from the fitting of the “Birth and Spread” equation (Ï001cel-bar=0.137J/m2) indicate low affinity of SrSO4 growth units for barite (0 0 1) faces. This is consistent with the relative high mismatch between celestite and barite structure. The behaviour of the epitaxial growth described in this work can help to interpret the oscillatory zoning frequently occurring in both natural and synthetic crystals of the BaxSr1âxSO4 solid solution.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Surface Science - Volume 581, Issues 2â3, 1 May 2005, Pages 225-235
Journal: Surface Science - Volume 581, Issues 2â3, 1 May 2005, Pages 225-235
نویسندگان
Nuria Sánchez-Pastor, Carlos M. Pina, José Manuel Astilleros, Lurdes Fernández-DÃaz, Andrew Putnis,