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Glass forming region in Ca-Si-O-N system using CaH2 as Ca source
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
2008 (English)In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 28, no 14, 2659-2664 p.Article in journal (Refereed) Published
Abstract [en]

The present work explores the glass-forming region in the Ca–Si–O–N system, particularly in the N-rich part of the system. Bulk oxynitride glasses in the Ca–Si–O–N system were prepared by melting mixtures of CaH2, SiO2 and Si3N4 powders in a nitrogen atmosphere at 1500–1650 °C. The glasses were characterized by X-ray powder diffraction, differential thermal analysis, scanning electron microscopy and transmission electron microscopy. Glass compositions were calculated from analyses obtained by energy dispersive X-ray (EDX) spectroscopy and combustion analysis, for cation and anion compositions, respectively. The glasses were found to be X-ray amorphous and gray to black in color. The glasses retain up to 58 e/o of nitrogen and 42 e/o of calcium. The glass formation depends on reaction kinetics and the precursor used. A strong exothermic reaction is observed at 850–1000 °C, leading to formation of amorphous and crystalline oxynitride phases that melt at high temperatures upon further heating. Glass transition temperatures (Tg) were observed to vary between 798 °C and 1050 °C, and crystallization occurs typically 130 °C above the glass transition temperature. The glass densities vary between 2.79 g/cm3 and 3.25 g/cm3.

Place, publisher, year, edition, pages
2008. Vol. 28, no 14, 2659-2664 p.
Keyword [en]
Oxynitride glass, Glass-forming region, Calcium content, Nitrogen content, Ca–Si–O–N
Identifiers
URN: urn:nbn:se:su:diva-15477DOI: 10.1016/j.jeurceramsoc.2008.04.017ISI: 000259131500005OAI: oai:DiVA.org:su-15477DiVA: diva2:181997
Available from: 2008-12-03 Created: 2008-12-03 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Preparation, characterization and properties of nitrogen rich glasses in alkaline earth-Si-O-N systems
Open this publication in new window or tab >>Preparation, characterization and properties of nitrogen rich glasses in alkaline earth-Si-O-N systems
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nitrogen rich glasses in the systems Ca-Si-O-N, Sr-Si-O-N and AE-Ca-Si-O-N (AE = Mg, Sr and Ba) have been prepared using a novel glass-synthesis route. The limits of the glass forming regions in the Ca and Sr systems and substitution limits in the AE-Ca-Si-O-N systems have been determined and physical properties of the glasses measured.

Transparent glasses were obtained for a few specific compositions in the Ca-Si-O-N and Mg-Ca-Si-O-N systems. All other glasses were found to be translucent gray to opaque black, with the coloration of the glasses depending on the modifier. Small inclusions of Ca/Sr silicides and, in much smaller amounts, elemental Si are believed to be responsible for their poor transparency.

A large glass forming region was found for the Ca-Si-O-N system, with glasses retaining up to 58 e/o N and 42 e/o Ca. In comparison, a more narrow glass forming region was found for the corresponding Sr system, with glasses retaining up to 45 e/o N and 39 e/o Sr. The glass formation was found to depend on reaction kinetics and precursors used. A strong exothermic reaction was observed at temperatures 650–1000oC, providing improved conditions for reaction kinetics upon further heating.

Physical property measurements for the Ca and Sr glasses showed that glass transition and crystallization temperatures, viscosity, hardness, Young’s modulus and shear modulus depend strongly on the nitrogen content and that these properties increase approximately linearly with increasing nitrogen content. Glass density and refractive index are also dependent on the modifier element and content, in particular for the Sr glasses.

Glasses AE-Ca-Si-O-N, with approximately constant (Ca/AE): Si:O:N ratios, showed that mixed modifier glass properties, such as density, molar volume, glass transition temperature, hardness, refractive index can be related to the effective cation field strength of the modifiers.

Place, publisher, year, edition, pages
Stockholm: Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, 2009. 116 p.
Keyword
Oxynitride glasses, glass forming region, nitrogen content, hardness, refractive index
National Category
Inorganic Chemistry
Research subject
Inorganic Chemistry
Identifiers
urn:nbn:se:su:diva-8521 (URN)978-91-7155-818-3 (ISBN)
Public defence
2009-03-25, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 13:00 (English)
Opponent
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Available from: 2009-03-04 Created: 2009-02-10 Last updated: 2010-03-09Bibliographically approved

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