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Preparation, characterization and properties of nitrogen rich glasses in alkaline earth-Si-O-N systems
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
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 [en]
Oxynitride glasses, glass forming region, nitrogen content, hardness, refractive index
National Category
Inorganic Chemistry
Research subject
Inorganic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-8521ISBN: 978-91-7155-818-3 (print)OAI: oai:DiVA.org:su-8521DiVA: diva2:200422
Public defence
2009-03-25, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 13:00 (English)
Opponent
Supervisors
Available from: 2009-03-04 Created: 2009-02-10 Last updated: 2010-03-09Bibliographically approved
List of papers
1. Glass forming region in Ca-Si-O-N system using CaH2 as Ca source
Open this publication in new window or tab >>Glass forming region in Ca-Si-O-N system using CaH2 as Ca source
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.

Keyword
Oxynitride glass, Glass-forming region, Calcium content, Nitrogen content, Ca–Si–O–N
Identifiers
urn:nbn:se:su:diva-15477 (URN)10.1016/j.jeurceramsoc.2008.04.017 (DOI)000259131500005 ()
Available from: 2008-12-03 Created: 2008-12-03 Last updated: 2017-12-13Bibliographically approved
2. Formation and properties of nitrogen-rich strontium silicon oxynitride glasses
Open this publication in new window or tab >>Formation and properties of nitrogen-rich strontium silicon oxynitride glasses
2009 (English)In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 44, no 2, 664-670 p.Article in journal (Refereed) Published
Abstract [en]

Glass formation in the system Sr–Si–O–N was investigated and properties of obtained glasses evaluated. The glass-forming region was determined for glasses prepared by melting mixtures of Sr metal, SiO2 and Si3N4 powders in Nb crucibles at 1600–1750 °C in nitrogen atmosphere using a radio frequency furnace. The glasses were found to be homogenous, translucent gray to opaque black, and to contain high contents of N (up to 45 e/o) and Sr (up to 36 e/o). The glass transition temperature (790–973 °C), density (2.99–4.07 g/cm3), microhardness (8.10–10.50 GPa), and refractive index (1.65–1.93) are strongly correlated with the amounts of Sr and N. The properties are compared with findings in other oxynitride silicate glass systems.

Identifiers
urn:nbn:se:su:diva-25745 (URN)10.1007/s10853-008-3058-3 (DOI)000262505200040 ()
Note
Part of urn:nbn:se:su:diva-8521Available from: 2009-03-04 Created: 2009-02-10 Last updated: 2017-12-13Bibliographically approved
3. Hardness and refractive index of Ca–Si–O–N glasses
Open this publication in new window or tab >>Hardness and refractive index of Ca–Si–O–N glasses
2009 (English)In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 355, no 4-5, 301-304 p.Article in journal (Refereed) Published
Abstract [en]

Vickers hardness and refractive index was determined for Ca–Si–O–N glasses with 14.6–58 e/o N and 19–42 e/o Ca. By applying slow cooling rates, transparent glasses were obtained for compositions near Ca9.94Si10O17.73N8.14, while the majority of the glasses were opaque due to small inclusions of elemental Si and/or Ca-silicide. Determined glass densities varied between 2.80 and 3.25 g/cm3. Hardness was found to vary from 7.3 to 10.1 GPa at a load of 500 g and, respectively increase and decrease linearly with N and Ca content. The refractive index was found to increase linearly with N content from 1.62 to 1.95 and showed no significant dependence on Ca content.

Keyword
Oxynitride glasses, Hardness, Nitrogen-containing glass
National Category
Chemical Sciences
Identifiers
urn:nbn:se:su:diva-25746 (URN)10.1016/j.jnoncrysol.2008.11.019 (DOI)
Available from: 2009-03-04 Created: 2009-02-10 Last updated: 2017-12-13Bibliographically approved
4. Properties of high nitrogen content mixed alkali-earth oxynitride glasses: (AExCa1-x)1.2(1)SiO1.9(1)N0.86(6), AE = Mg, Sr, Ba.
Open this publication in new window or tab >>Properties of high nitrogen content mixed alkali-earth oxynitride glasses: (AExCa1-x)1.2(1)SiO1.9(1)N0.86(6), AE = Mg, Sr, Ba.
2009 (English)In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 355, no 22-23, 1259-1263 p.Article in journal (Refereed) Published
Abstract [en]

Mixed alkali earth element containing high nitrogen content oxynitride glasses (Ca1−xAEx)1.2(1)SiO1.9(1)N0.86(6), with AE = Mg, Sr, Ba, x ≤ 0.30 for Mg and x ≤ 0.46 for Sr and Ba, and nominally constant (Ca/AE):Si:O:N ratios were prepared in order to investigate the compositional dependencies of physical properties on alkali earth element composition. The glasses were prepared by melting mixtures of AEH2, CaH2, SiO2 and Si3N4 powders in nitrogen atmosphere at 1600–1700 °C and characterized by X-ray powder diffraction and scanning and transmission electron microscopy. Cation and anion glass compositions were determined by respectively energy dispersive X-ray analysis and combustion analysis. The determined physical properties were density, glass transition temperature, Vickers hardness, and refractive index. The physical properties were found to vary linearly with the degree of substitution of Ca by the AE elements. The density of the glasses increases substantially upon substitution by Sr and Ba, up to 3.99 g/cm3. Glass transition temperatures are found to be higher for Mg and Sr substituted glasses, ca. 900 °C, in comparison with Ba substituted glasses, ca. 850 °C. The hardness increases upon substitution by Mg, up to 12.2 GPa at x = 0.46, and decreases upon substitution by Sr and Ba. The refractive index increases upon substitution by Sr and Ba, up to 1.97 for Ba at x = 0.46, and decreases upon substitution by Mg. The transparency of the glasses was found to increase upon increasing substitution by Mg and completely transparent glasses were obtained for x = 0.24.

Keyword
Oxynitride glass, Hardness, Refractive index
Identifiers
urn:nbn:se:su:diva-25747 (URN)10.1016/j.jnoncrysol.2009.04.036 (DOI)000268405000012 ()
Note
Part of urn:nbn:se:su:diva-8521Available from: 2009-03-04 Created: 2009-02-10 Last updated: 2017-12-13Bibliographically approved
5. A cubic calcium oxynitrido-silicate, Ca2.88Si2N1.77O4.23
Open this publication in new window or tab >>A cubic calcium oxynitrido-silicate, Ca2.88Si2N1.77O4.23
Show others...
(English)Article in journal (Refereed) Submitted
Identifiers
urn:nbn:se:su:diva-25748 (URN)
Note
Part of urn:nbn:se:su:diva-8521Available from: 2009-03-04 Created: 2009-02-10 Last updated: 2010-03-09Bibliographically approved

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