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  • 1.
    Edén, Mattias
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för fysikalisk kemi.
    The split network analysis for exploring composition-structure correlations in multi-component glasses: I. Rationalizing bioactivity-composition trends of bioglasses2011Inngår i: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 357, nr 6, s. 1595-1602Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a strategy, referred to as “split network” analysis, for assessing the average network polymerization (r(F)) and mean number of bridging oxygen (BO) atoms ( (N) over bar (F)(BO)) for each individual network former F in multi-component oxide-based glasses, primarily targeting those involving Al, B, P and Si. This requires a priori knowledge about the parameters (r(F), (N) over bar (F)(BO)) of all network builders, but one, whose values are deduced by the split network procedure. We illustrate split-network concepts for establishing composition/structure/bioactivity correlations in Na-Ca-Si-P-O glasses. The cooperating influences on the bioactivity from the average polymerization degree of the silicate network and the amounts of orthophosphate and sodium ions are discussed.

  • 2.
    Edén, Mattias
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för fysikalisk kemi.
    Sundberg, Peter
    Stålhandske, Christina
    The split network analysis for exploring composition-structure correlations in multi-component glasses: II. Multinuclear NMR studies of alumino-borosilicates and glass-wool fibers2011Inngår i: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 357, nr 6-7, s. 1587-1594Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The preceding part [M. Eden, J. Non.-Cryst. Solids, 357, (2011) 1595-1602] introduced the “split network” strategy for estimating the network polymerization degree (r(A)) and mean number of bridging oxygen (BO) atoms ((N) over bar (A)(BO)) for a network former A, given that these parameters are known for all other network builders in the multi-component oxide glass. However, as the detailed ordering of BO and non-bridging oxygen (NBO) species is often difficult to assess experimentally, we summarize some “rules of thumb” for predicting the coordination number and tendency to accept NBO ions for Al(3+), B(3+), Si(4+) and P(5+) cations: they are helpful in scenarios devoid of experimental data. Using the parameters r and (N) over bar (BO), we present expressions for the BO/NBO distributions among tetrahedrally coordinated cations, as predicted from the binary and random models. Multinuclear (11)B, (27)Al and (29)Si solid-state NMR is exploited to derive the split network representations of a set of Na-Ca-(Al)-(B)-Si-O glasses. These results are subsequently used to gain structural insight into two commercial glass-wool fibers that constitute alumino-borosilicate networks modified by Na(+), K(+), Ca(2+) and Mg(2+) ions.

  • 3.
    Iftekhar, Shahriar
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för fysikalisk kemi.
    Grins, Jekabs
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Edén, Mattias
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för fysikalisk kemi.
    Composition–property relationships of the La2O3–Al2O3–SiO2 glass system2010Inngår i: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 356, nr 20-22, s. 1043-1048Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report physical properties of density, glass transition temperature, Vickers hardness and refractive index for 15 La–Al–Si–O glasses within the compositional region 10–28 mol% La2O3, 11–30% Al2O3 and 45–78% SiO2. The glass transition temperature varies only slightly between 871 and 883 °C. Both the density (3.25–4.33 g cm−3) and refractive index (1.59–1.70) display similar compositional dependencies and are primarily dictated by the La2O3 content. The hardness (6.4–9.0 GPa) increases with decreasing SiO2 content and to a minor extent also with the amount of La2O3 of the glass. The physical properties, in particular the hardness, are discussed with reference to glass structure. The similarity in the observed properties between the present oxide-based glasses and those of analogous rare-earth (RE) element-containing RE–Si–(Al)–O–N oxynitride glasses is highlighted and discussed in relation to the apparent, but hitherto largely neglected, role of RE-ions to primarily control many enhanced physical properties of oxynitride glasses.

  • 4.
    Iftekhar, Shahriar
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Leonova, E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Edén, Mattias
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Structural Characterizations of Lanthanum Aluminosilicate Glasses by 27Al and 29Si Solid State NMR2009Inngår i: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 355, nr 43-44, s. 2165-2174Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 5.
    Leonova, Ekaterina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Hakeem, Abbas S.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Jansson, Kjell
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Stevensson, Baltzar
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Shen, Zhijian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Grins, Jekabs
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Esmaeilzadeh, Saeid
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Edén, Mattias
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Nitrogenrich La-Si-Al-O-N oxynitride glass structures probed by solid state NMR2008Inngår i: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 354, nr 1, s. 49-60Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigate the local structures of oxynitride La–Si–(Al)–O–N glasses by 29Si and 27Al magic-angle spinning (MAS) solid state Nuclear Magnetic Resonance (NMR). The glasses studied span an unprecedented range of compositions, up to >50 at.% lanthanum and nitrogen out of the cations and anions, respectively, and achievable through a recently introduced glass preparation route. Transmission as well as scanning electron microscopy verified homogeneous samples over length-scales down to 20 nm. As the nitrogen content of the glasses increased, 29Si NMR evidenced a progressive formation of Si–N bonds, with SiO2N2 tetrahedra dominating in the nitrogen-rich glass networks. In the oxygen-rich end of the series, aluminum is predominantly present in tetrahedral coordination as AlO4, whereas the glasses with highest nitrogen contents have a major fraction of AlO3N structural units. Trends in isotropic 29Si and 27Al chemical shifts and 27Al quadrupolar couplings are compared with results of La–Si–Al–O glasses and are discussed in relation to the glass compositions and their proposed structures.

  • 6. Limbach, René
    et al.
    Karlsson, Stefan
    Scannell, Garth
    Mathew, Renny
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Edén, Mattias
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Wondraczek, Lothar
    The effect of TiO2 on the structure of Na2O-CaO-SiO2 glasses and its implications for thermal and mechanical properties2017Inngår i: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 471, s. 6-18Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Titania represents an important compound for property modifications in the widespread family of soda lime silicate glasses. In particular, such titania-containing glasses offer interesting optical and mechanical properties, for example, for substituting lead-bearing consumer glasses. Here, we provide a systematic study of the effect of TiO2 on the structural, thermal, and mechanical properties for three series of quaternary Na2O-CaO-TiO2-SiO2 glasses with TiO2 concentrations up to 12 mol% and variable Na2O, CaO, and SiO2 contents. Structural analyses by Raman and magic-angle spinning Si-29 NMR spectroscopy reveal the presence of predominantly four-fold coordinated Ti-[4] atoms in glasses of low and moderate TiO2 concentrations, where Si-O-Si bonds are replaced by Si-O-Ti-[4] bonds that form a network of interconnected TiO4 and SiO4 tetrahedra, with a majority of the non bridging oxygen ions likely being located at the SiO4 tetrahedra. At higher TiO2 contents, TiO5 polyhedra are also formed. Incorporation of TiO2 strongly affects the titanosilicate network connectivity, especially when its addition is accompanied by a decrease of the CaO content. However, except for the thermal expansion coefficient, these silicate-network modifications seem to have no impact on the thermal and mechanical stability. Instead, the compositional dependence of the thermal and mechanical properties on the TiO2 content stems from its effect on the network energy and packing efficiency.

  • 7.
    Pettersson, Lars G. M.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Nilsson, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. SLAC National Accelerator Laboratory, USA.
    The structure of water; from ambient to deeply supercooled2015Inngår i: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 407, s. 399-417Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Here we discuss the structure of water in terms of a temperature-dependent balance between two classes of hydrogen-bonded structures. At high and down to mildly supercooled temperatures most molecules favor a closer packing than tetrahedral, with strongly distorted hydrogen bonds. This allows the quantized librational modes to be excited and contribute to the entropy while the loss of enthalpy due to breaking hydrogen bonds is compensated by enhanced van der Waals interactions. Tetrahedral hydrogen bonding is of lower enthalpy resulting in tetrahedrally bonded water patches appearing, but only as fluctuations with size and life-time increasing at lower temperatures. Measurements of the structure at deeply supercooled conditions show a continuous increase in tetrahedrality which becomes accelerated below the temperature of homogeneous ice nucleation. The two local structures are connected to the liquid liquid critical point (LLCP) hypothesis in supercooled water and correspond to high density liquid (HDL) and low density liquid (LDL). We propose that both HDL and LDL behave as normal liquids and that the anomalous properties of water result from the transition between them, which occurs over a wide temperature range at ambient pressure. The key issue is the competition between incompatible conditions for maximizing the entropy, favored in HDL, and minimizing the enthalpy, favored in LDL, which leads to the instability in the liquid and is the fundamental origin of the proposed LLCP.

  • 8. Sellappan, Pathikumar
    et al.
    Sharafat, Ali
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Keryvin, Vincent
    Houizot, Patrick
    Rouxel, Tanguy
    Grins, Jekabs
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Esmaeilzadeh, Saeid
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Elastic properties and surface damage resistance of nitrogen-rich (Ca,Sr)-Si-O-N glasses2010Inngår i: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 356, nr 41-42, s. 2120-2126Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ca and Sr-based oxynitride glasses with very high nitrogen content have been synthesized using metal hydrides as primary precursors. Values of Young's modulus, shear modulus, bulk modulus and Poisson's ratio were determined by means of ultrasonic echography. Vickers micro-indentation has been used to characterize hardness and indentation fracture toughness behaviour. Elastic moduli were found to increase linearly with nitrogen content, with the highest value of Young's modulus at 135 GPa, for a Ca-glass with 58 e/o of nitrogen. The Sr-glasses exhibit lower elastic moduli than Ca glasses. Poisson's ratio, hardness, indentation fracture toughness, crack initiation load and surface damage resistance were found to increase with increasing nitrogen content for both glass series.

  • 9.
    Sharafat, Ali
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Grins, Jekabs
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Esmaeilzadeh, Saeid
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Hardness and refractive index of Ca–Si–O–N glasses2009Inngår i: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 355, nr 4-5, s. 301-304Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 10.
    Sharafat, Ali
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Grins, Jekabs
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Esmaeilzadeh, Saeid
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    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.2009Inngår i: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 355, nr 22-23, s. 1259-1263Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 11.
    Stevensson, Baltzar
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Eden, Mattias
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Structural rationalization of the microhardness trends of rare-earth aluminosilicate glasses: Interplay between the RE3+ field-strength and the aluminum coordinations2013Inngår i: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 378, s. 163-167Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Many studies have sought to rationalize property/structure relationships in rare-earth (RE) bearing aluminosilicate oxide or oxynitride glasses. In a set of 48 RE2O3-Al2O3-SiO2 (RE = La, Y, Lu, Sc) glasses of widely spanning compositions and RE3+ cation field-strengths (CFS), we observe strong correlations between the microhardness, glass compactness, and the average coordination number of Al. We argue that the well-known microhardness elevation for increasing RE3+ CFS stems not primarily from the RE3+ ions themselves, as hitherto believed, but merely from a structure-strengthening by AlO5/AlO6 polyhedra that cross-link different glass-network segments. The high-coordination Al populations grow together with the RE3+ CFS.

  • 12.
    Stevensson, Baltzar
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Jaworski, Aleksander
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Edén, Mattias
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    The structural roles of Sc and Y in aluminosilicate glasses probed by molecular dynamics simulations2017Inngår i: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 460, s. 36-46Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The incorporation of rare-earth (RE) elements into an aluminosilicate (AS) glass generally enhances its optical and mechanical properties. Atomistic molecular dynamics (MD) simulations were employed for probing the coordinations of Y3+ and Sc3+ in Y2O3-Al2O3-SiO2 and Sc2O3-Al2O3-SiO2 glasses of variable Si, Al, and RE contents. YO6 and ScO5 polyhedra are the most abundant RE species. We explore the trends in the distributions of the various (non)bridging oxygen species and Si/Al/RE cations in the first and second RE coordination spheres, respectively. The lowest REM and R051 coordinations of both Y and Sc exhibit a strong preference for coordinating non-bridging 0 species, which gradually relaxes for increasing coordination number p. Clear deviations from a statistical Si/AI/RE distribution around the REOp polyhedra is observed, with preferences for RE-RE contacts relative to RE-Al and (notably) RE-Si. The extents of RE-RE associations are similar for Y and Sc and grow slightly for increasing Si content and/or glass network polymerization. The propensity for RE-Al contacts becomes emphasized in the Sc AS glasses, mainly at the expense of Sc-Si. The YOp and ScOp polyhedra connect to their Si/Al/RE neighbors primarily by sharing corners, but a significant extent of edge-sharing is also observed, which increases both with the RE1PI coordination number, and along the series Si < Al-[4] < Al-[5]/Al-[6] approximate to RE of neighbors.

  • 13. Wójcik, N. A.
    et al.
    Ali, S.
    Möncke, D.
    Tagiara, N. S.
    Kamitsos, E. I.
    Segawa, H.
    Eriksson, Mirva
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Jonson, B.
    The influence of Be addition on the structure and thermal properties of alkali-silicate glasses2019Inngår i: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 521, artikkel-id 119532Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Be-Na-(Li)-Si oxide glasses containing up to 15 mol% of BeO were prepared. Their structure was characterized by X-ray powder diffraction and Raman as well as infrared spectroscopic techniques, while their chemical compositions were examined by Inductively Coupled Plasma Optical Emission Spectrometry. All materials were found to be amorphous and contain Al contaminations from minor dissolution of the alumina crucibles. The results of Raman and IR spectroscopies showed that BeO addition to Na-(Li)-Si glass systems resulted in the formation of [BeO4/2](2-) tetrahedra which are inserted into the silicate glass network, demonstrating the intermediate glass-forming role of BeO. In parallel, the effective destruction of Si-O-Si bridges was observed by vibrational spectroscopy. The glass transition temperature was studied by Differential Thermal Analysis and found to range from about 431 degrees C to 551 degrees C. A significant increase in T-g by 70 degrees C was found as SiO2 was substituted by up to 15 mol% BeO.

  • 14. Wójcik, N. A.
    et al.
    Jonson, B.
    Möncke, D.
    Palles, D.
    Kamitsos, E. I.
    Ghassemali, E.
    Seifeddine, S.
    Eriksson, Mirva
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Ali, S.
    Influence of synthesis conditions on glass formation, structure and thermal properties in the Na2O-CaO-P2O5 system doped with Si3N4 and Mg2018Inngår i: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 494, s. 66-77Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Oxynitride phosphate glasses and glass-ceramics were prepared using new synthesis routes for phosphate glasses. Materials were melted from pre-prepared glass samples in the system Na-Ca-P-0 with addition of Mg and/or Si3N4 powders under different preparation conditions. The melting process was conducted at 1000-1500 degrees C either under air or nitrogen atmosphere to obtain materials with different nitrogen content. Their topography and structure were characterized by Confocal Microscopy, Scanning Electron Microscopy, X-ray powder diffraction and Raman and infrared spectroscopy techniques, while their chemical compositions were examined by Energy Dispersive X-ray spectroscopy (EDS). All materials prepared under nitrogen atmosphere were found to contain a relative low quantity of nitrogen and high amount of Nb leached from the crucible. The reaction with the Nb crucible was not previously observed for silicon-based oxynitride glasses. The synthesized materials form two groups: glasses and glass-ceramics. The first ones, were prepared under air and nitrogen atmospheres at temperatures up to 1400 degrees C, and were found to be amorphous and homogeneous. Raman and infrared spectroscopy measurements confirm the presence of amorphous phosphates in the synthesized materials. The samples of the second group were prepared at temperatures above 1400 degrees C and were found to be translucent and partially crystallized. They contain nanocrystallites of calcium and sodium phosphates including hydroxyapatite (HAp). The thermal properties of samples were studied by Differential Scanning Calorimetry (DSC). The obtained glass transition temperatures range from about 360 degrees C to 640 degrees C and exhibit high values for glass-ceramic materials. Stability is improved in the studied glass-ceramics because of the increased degree of network polymerization of the remaining glassy matrix. The approximate fragility index decreases two times for oxynitride materials compared to the primary glass. The synthesized new materials may be competitive to well-known bioactive phosphate glasses thanks to their improved stability by Mg, Si, N and Nb doping.

  • 15.
    Yu, Yang
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Mathew, Renny
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Edén, Mattias
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Quantitative composition–bioactivity relationships of phosphosilicate glasses: Bearings from the phosphorus content and network polymerization2018Inngår i: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 502, s. 106-117Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bioactive phosphosilicate glasses integrate with bone/tooth tissues by forming a bone-mineral mimicking surface layer of calcium hydroxyapatite (HA). The HA formation (“in vitrobioactivity”) in a simulated body fluid (SBF) solution is known to depend both on the P content (nP) and silicate network connectivity () of the glass, but the precise bioactivity–composition relationships remain poorly understood. We present a comprehensive study that clarifies the dependence of the in vitro bioactivity on the {nP, } parameters for Na2O–CaO–SiO2–P2O5 glass powders (2.6–6.0 mol% P2O5) exposed to SBF for 24 h, using infrared (IR) and solid-state 31P nuclear magnetic resonance (NMR) spectroscopy in conjunction with measured Ca and P concentrations in the solution. IR-derived relative apatite amounts reveal that an increase in the P content of the pristine glass promotes apatite formation by gradually reducing its dependence on the silicate network polymerization: increasing nP widens the  range that provides a high and nearly constant amount of HA, which scales roughly linearly with nP; these properties assist future design of P-rich bioactive glasses. All glasses provide significant HA formation for increasing  values up to ≈2.6, above which the in vitro bioactivity is lost due to insufficient glass dissolution. We also discuss the complex dependence of the SBF-testing outcome on the mass concentration and composition of the glass powder, as well as on its particle sizes, highlighting critical concerns that may guide developments of improved in vitro bioactivity-testing protocols. A strong dependence of the HA formation on the particle sizes is observed for glass powders with low P2O5 content (2.6 mol%), as opposed to their P-richer counterparts that reveal no pronounced particle-size effects.

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