کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1481381 1510467 2013 8 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Mixed alkaline earth effect in sodium aluminosilicate glasses
موضوعات مرتبط
مهندسی و علوم پایه مهندسی مواد سرامیک و کامپوزیت
پیش نمایش صفحه اول مقاله
Mixed alkaline earth effect in sodium aluminosilicate glasses
چکیده انگلیسی


• The mixed alkaline earth effect (MAEE) in aluminosilicate glasses is studied by substituting MgO for CaO.
• The MAEE manifests itself as a maximum in the amount of bridging oxygen.
• The MAEE manifests itself as a minimum in hardness and isokom temperatures.
• The minimum in isokom temperatures is due to bond weakening in the local structure around the network modifiers.
• The minimum in hardness could be associated with the corresponding minimum in shear viscosity.

While the mixed alkali effect has received significant attention in the glass literature, the mixed alkaline earth effect has not been thoroughly studied. Here, we investigate the latter effect by partial substitution of magnesium for calcium in sodium aluminosilicate glasses. We use Raman and NMR spectroscopies to obtain insights into the structural and topological features of these glasses, and hence into the mixed alkaline earth effect. We demonstrate that the mixed alkaline earth effect manifests itself as a maximum in the amount of bonded tetrahedral units and as a minimum in liquid fragility index, glass transition temperature, Vickers microhardness, and isokom temperatures (viz., the temperatures at η = 1013.5 and 1012.2 Pa s). The observed minima in fragility, glass transition temperature, and isokom temperature are ascribed to bond weakening in the local structural environment around the network modifiers. We suggest that, since the elastic properties of the investigated system are compositionally independent, the minimum in Vickers microhardness is closely correlated to the minimum in isokom temperatures. Both of these properties are related to plastic flow and the translational motion of structural units, and hence both may be related to the same underlying topological constraints. This indicates that there might not be any significant difference in the onset of the rigid sub-Tg constraints for the investigated compositions.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Non-Crystalline Solids - Volume 369, 1 June 2013, Pages 61–68
نویسندگان
, , , , , ,