Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Structural Characterizations of Lanthanum Aluminosilicate Glasses by 27Al and 29Si Solid State NMR
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.
2009 (English)In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 355, no 43-44, 2165-2174 p.Article in journal (Refereed) Published
Abstract [en]

We investigate the network structures of LaSiAlO glasses by 29Si magic-angle-spinning (MAS) nuclear magnetic resonance (NMR). Their compositions span most of the glass-forming region of the ternary La2O3Al2O3SiO2 system at 1600 °C. The 29Si NMR resonances narrow and become progressively deshielded when Al substitutes for Si in the network, as well as for increasing La-content of the glass, which leads to network depolymerization. We compare experimental and calculated center of gravities of the 29Si NMR peaks, the latter generated from different simplified models for the distributions of Al and Si as well as bridging oxygen (BO) and non-bridging oxygen (NBO) atoms over the networks. The data do not permit accurate quantifications and may only be interpreted in limiting scenarios. However, they indicate that both distributions are essentially randomized, implying a clear deviation of the Al/Si ordering from that according to a Loewenstein Al-avoidance, coupled with a nearly uniform partitioning of the NBO atoms between Al and Si tetrahedra.

Place, publisher, year, edition, pages
2009. Vol. 355, no 43-44, 2165-2174 p.
National Category
Chemical Sciences
Research subject
Physical Chemistry
Identifiers
URN: urn:nbn:se:su:diva-25761DOI: 10.1016/j.jnoncrysol.2009.06.031ISI: 000271347000011OAI: oai:DiVA.org:su-25761DiVA: diva2:200482
Available from: 2009-02-26 Created: 2009-02-18 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Structural Investigations of Complex Glasses by Solid-state NMR
Open this publication in new window or tab >>Structural Investigations of Complex Glasses by Solid-state NMR
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This PhD thesis presents structural investigations of amorphous inorganic materials: oxide and oxynitride glasses and mesoporous bioactive glasses (MBGs), by solid-state Nuclear Magnetic Resonance (NMR).

Lanthanum oxide and oxynitride [La-Si-(Al)-O-(N)] glasses have a large number of potential applications due to their physical properties. In our work we have studied, compared to previous investigations, significantly expanded ranges of glass compositions (for oxynitride glasses, including samples of very high nitrogen content, up to 53 % out of the anions). We have estimated local environments of 29Si and 27Al structural units (their coordination, polymerization degree and number of N incorporated into tetrahedral units) in the materials. We have suggested a random Al/Si distribution along with almost uniform non-bridging oxygen atoms distribution in aluminosilicate glasses.

Silicon nitride was used as precursor in the oxynitride glass synthesis. We studied both α- and β-modifications of silicon nitride, 15N-enriched, as well as fully (29Si, 15N)-enriched samples. We have shown that the linewidths of 15N NMR spectra are dominated by J(29Si-15N) coupling in 29Si315N4 sample.

Mesoporous bioactive glasses in the CaO-SiO2-P2O5 system show superior bioactivity (the ability to form a hydroxycarbonate apatite layer on the glass surface when exposed to body fluids) compared to conventional bioactive glasses due to their large surface area and uniform pore-size distribution. Previous studies suggested a homogeneous cation distribution over the MBG samples on a 10−20 nm length-scale. From our results, on the other hand, we may conclude that Si and P is not intimately mixed. We propose a structural model, in which the pore walls of MBGs are composed of a silica network, and a phosphate phase is present as nanometer-sized clusters that are dispersed on the pore wall.

Place, publisher, year, edition, pages
Stockholm: Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, 2009. 62 p.
Keyword
glass, glass structure and properties, NMR, magic angle spinning, chemical shift
National Category
Physical Chemistry
Research subject
Physical Chemistry
Identifiers
urn:nbn:se:su:diva-8565 (URN)978-91-7155-816-9 (ISBN)
Public defence
2009-03-19, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 8 C, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2009-02-26 Created: 2009-02-18 Last updated: 2010-01-26Bibliographically approved
2. Structure-Property-Composition Correlations in Rare-Earth Alumino-silicate Glasses
Open this publication in new window or tab >>Structure-Property-Composition Correlations in Rare-Earth Alumino-silicate Glasses
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Rare earth (RE) alumino-silicate (AS) glasses exhibit favorable physical, mechanical and optical properties, such as high values of the glass transition temperature, Vickers hardness, and refractive index. RE2O3-Al2O3-SiO2 glasses have found several industrial applications, for example as components of optical amplifiers and lasers. Many of these features stem from the high cation field-strength (CFS) of the trivalent RE ions (proportional to the valence of the ion divided by the square of its radius), which affects not only the physical properties of the glass, but also their structures.

This thesis deals with investigations of four different RE2O3-Al2O3-SiO2 systems, where RE represents either of La, Y, Lu or Sc. The glass forming regions of the latter two were reported by us for the first time. Within each system, glasses were prepared for variable RE, Si and Al contents.

The glass structures were investigated by solid-state 29Si and 27Al nuclear magnetic resonance (NMR) spectroscopy that informs about the local Si and Al environments in the glass network, which is built from interlinked SiO4 and AlO4 groups. Higher Al coordination numbers were also revealed by 27Al NMR: their amounts were observed to increase markedly as the CFS of the RE ion increases, i.e., along the series La<Y<Lu<Sc. This thesis discusses such structure/composition relationships, as well as the correlations between the glass composition and its physical properties of density, molar volume, compactness, glass transition temperature, Vickers hardness and refractive index. Some of these properties, for example the glass transition temperature and Vickers hardness, were observed to enhance as the RE3+ CFS increased.

Place, publisher, year, edition, pages
Stockholm: Department of Materials and Environmental Chemistry (MMK), Stockholm University, 2012. 79 p.
National Category
Physical Chemistry
Research subject
Physical Chemistry
Identifiers
urn:nbn:se:su:diva-69325 (URN)978-91-7447-431-2 (ISBN)
Public defence
2012-02-14, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 5: Manuscript.

Available from: 2012-01-23 Created: 2012-01-11 Last updated: 2016-04-29Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Iftekhar, ShahriarEdén, Mattias
By organisation
Department of Physical, Inorganic and Structural Chemistry
In the same journal
Journal of Non-Crystalline Solids
Chemical Sciences

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 182 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf