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  • 1.
    Ali, Sharafat
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Jonson, Bo
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Preparation of oxynitride glasses from woody biofuel ashes.2010In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 356, no 50-51, p. 2774-2777Article in journal (Refereed)
    Abstract [en]

    Oxynitride glasses have been prepared by melting woody biofuel ash from a power plant in south Sweden with addition of calcium metal as an extra modifier in a nitrogen atmosphere at 1350–1500 °C. The glasses were characterized by X-ray powder diffraction, differential thermal analysis and scanning electron microscopy. Cation and anion glass compositions were determined by energy dispersive X-ray analysis and combustion analysis, respectively. The glasses were found to be homogenous, translucent gray to black, and to contain up to 23 e/o of calcium and 5 e/o of nitrogen. The glass formation depends on the ratio of calcium metal introduction to the ash precursors. A strong exothermic reaction was observed at 650–850 °C, leading to the formation of amorphous and crystalline oxynitride phases that melt at high temperatures upon further heating. The glass densities vary between 2.76 g/cm3 and 2.92 g/cm3. The glass transition temperature was found to vary from 670 °C to 749 °C and increase linearly with the nitrogen content.

  • 2.
    Hakeem, Abbas Saeed
    et al.
    King Fahd University of Petroleum & Minerals (KFUPM).
    Ali, Sharafat
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Jonson, Bo
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Preparation and properties of mixed La–Pr silicate oxynitride glasses2013In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 368, p. 93-97Article in journal (Refereed)
    Abstract [en]

    The preparation and properties of mixed lanthanide (La, Pr) silicate oxynitride glasses are reported. These oxynitride glasses were prepared by melting mixtures of La, Pr, SiO2 and Si3N4 powders in a nitrogen atmosphere at 1750 °C. The glasses were characterized by X-ray powder diffraction, differential thermal analysis, scanning and transmission electron microscopy. Glass compositions were calculated from the analyses obtained by energy dispersive X-ray (EDX) spectroscopy and combustion analysis, for cation and anion compositions, respectively. The glasses were found to be homogenous, optically opaque black, and to contain contents up to 66 e/o of N and up to 48 e/o of La–Pr. The physical properties were found to vary linearly with the degree of substitution of La by the Pr. Determined glass density increases substantially upon the substitution of La by Pr, up to 5.49 g/cm3. The calculated molar volumes and compactness values decrease and increase respectively by the substitution of Pr for La. Glass transition temperatures and microhardness increase upon the substitution by Pr, up to 1086 °C and 10.98 GPa, respectively. The refractive index increases upon the substitution by Pr up to 2.00.

  • 3.
    Kupracz, P.
    et al.
    Gdansk Univ Technol, Poland.
    Wojcik, Natalia A.
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology. Gdansk Univ Technol, Poland.
    Barczynski, R. J.
    Gdansk Univ Technol, Poland.
    A method of determination of electrical conduction mechanisms in complex amorphous materials2018In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 498, p. 223-227Article in journal (Refereed)
    Abstract [en]

    A novel approach to determine conduction mechanisms in complex amorphous materials was presented and tested on a real system. In the first step of the presented method, total electrical admittance of the material is analyzed in order to separate a couple of processes, each of which can be described by Jonscher's universal dielectric response. In the following step, a temperature dependence of dielectric response parameters of the processes is determined and compared with known models of conduction mechanisms in structural amorphous materials. Using this approach, a presence of two different conduction mechanisms describing electrical conductivity in a two-phase glass was described.

  • 4.
    Mukherjee, Debasis Pradip
    et al.
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology. Univ Calcutta, India .
    Molla, Atiar Rahaman
    CSIR Cent Glass & Ceram Res Inst, India.
    Das, Sudip Kumar
    Univ Calcutta, India.
    The influence of MgF2 content on the characteristic improvement of machinable glass ceramics2016In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 433, p. 51-59Article in journal (Refereed)
    Abstract [en]

    The influence of MgF2 on the various properties like crystalline behavior, microstructure phases, hardness etc. in the SiO2-Al2O3-MgO-K2O-B2O3 glass system has been investigated. Three batches of glass system were synthesized and characterized by differential scanning calorimetry (DSC), coefficient of thermal expansion (CTE), X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) equipped with energy dispersion X-ray spectroscopy (EDS). DSC study reveals that with the increase in MgF2 content the glass transition temperature (T-g) and first crystallization peak temperature (T-p(I)) decreased whilst the second crystallization peak temperature (T-p(II)) slightly increased. The CTE of the glasses is found to be in the ranges 634-6.40 x 10(-6) K-1 (50-400 degrees C). The activation energy (E-c) and frequency factor (v) both increase with increasing MgF2 content. The three-dimensional crystal growth is observed. The mica crystals are identified as fluorophlogopite, the predominant crystal phase for all the three glass specimens heat treated at 1050 degrees C. Vickers hardness values decrease with increasing amount of fluorine content and it gives better machinability. (C) 2015 Elsevier B.V. All rights reserved.

  • 5.
    Möncke, Doris
    et al.
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology. Fed Univ Sao Carlos UFSCar, Brazil;Natl Hellen Res Fdn, Greece.
    Jiusti, Jeanini
    Fed Univ Sao Carlos UFSCar, Brazil.
    Silva, Lais Dantas
    Fed Univ Sao Carlos UFSCar, Brazil.
    Martins Rodrigues, Ana Candida
    Fed Univ Sao Carlos UFSCar, Brazil.
    Long-term stability of laser-induced defects in (fluoride-)phosphate glasses doped with W, Mo, Ta, Nb and Zr ions2018In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 498, p. 401-414Article in journal (Refereed)
    Abstract [en]

    Laser-induced defects in glasses are of considerable interest for many applications from optics to photonics. The importance of low-level impurities of polyvalent ions in aiding defect formation has been identified early on. (Fluoride-)phosphate glasses are used today as laser materials, waveguides, amplifiers and luminescing materials, all sensitive to a change of the materials transmission by the interaction with light during application. To better understand the processes of defect generation and recovery, a systematic comparison of defect formation in various glasses and for various radiation sources and dopants has been conducted over the last decades. Here we will focus on (fluoride-) phosphate glasses doped with 50 to 5000 ppm of the 4d and 5d ions Zr, Nb, Ta, Mo and W. Glasses were melted under air or under reducing conditions in order to shift the redox equilibrium of the dopants before irradiation with either the 193 nm or 248 nm excimer laser. Only for W, Mo and Nb reduced ion species were confirmed by optical and/or ESR spectroscopy in the pre-irradiated glasses. However, irradiation showed for all metaphosphates the presence of reduced dopant species (W5+, Mo5+, Ta4+, Nb4+, Zr3+), acting as extrinsic hole centers (HC) after being photo-oxidized by laser irradiation to the fully oxidized d ions (Mn+)(+)-HC. Only for Ta5+ with its (Ta5+)(-)-electron center (EC), photo-reduction to the tetravalent ion was observed. Defect recovery was followed up to 16 years after the irradiation experiments, showing that most (Mn+)(+)-HC were very stable, while intrinsic HC either recombined with EC or converted into extrinsic (Mn+)(+)-HC. Due to ubiquitous iron impurities, even these high purity glasses with iron levels of 5-10 ppm or less, showed the formation of (Fe2+)(+)-HC.

  • 6. Sellappan, Pathikumar
    et al.
    Ali, Sharafat
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Keryvin, Vincent
    Houizot, Patrik
    Tanguy, Rouxel
    Grins, Jekabs
    Esmaeilzadehb, Saeid
    Elastic properties and surface damage resistance of nitrogen-rich (Ca,Sr)–Si–O–N glasses2010In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 356, no 41-42, p. 2120-2126Article in journal (Refereed)
    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.

  • 7.
    Wojcik, Natalia A.
    et al.
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology. Gdansk Univ Technol, Poland.
    Jonson, Bo
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    Möncke, Doris
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology. Natl Hellen Res Fdn, Greece.
    Polies, D.
    Natl Hellen Res Fdn, Greece.
    Kamitsos, E. I.
    Natl Hellen Res Fdn, Greec.
    Ghassemali, E.
    Jönköping University.
    Seifeddine, S.
    Jönköping University.
    Eriksson, M.
    Stockholm University.
    Ali, Sharafat
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    Influence of synthesis conditions on glass formation, structure and thermal properties in the Na2O-CaO-P2O5 system doped with Si3N4 and Mg2018In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 494, p. 66-77Article in journal (Refereed)
    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.

  • 8.
    Wójcik, Natalia A.
    et al.
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology. Gdańsk University of Technology, Poland.
    Ali, Sharafat
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    Möncke, Doris
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology. Alfred University, USA;National Hellenic Research Foundation, Greece.
    Kamitsos, Efstratios
    National Hellenic Research Foundation, Greece.
    Segawa, Hiroyo
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology. National Institute for Materials Science, Japan.
    Eriksson, Mirva
    Stockholm University, Sweden.
    Jonson, Bo
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    The influence of Be addition on the structure and thermal properties of alkali-silicate glasses2019In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 521, article id 119532Article in journal (Refereed)
    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 °C to 551 °C. A significant increase in Tg by 70 °C was found as SiO2 was substituted by up to 15 mol% BeO.

  • 9.
    Wójcik, Natalia A.
    et al.
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology. Gdańsk University of Technology, Poland.
    Jonson, Bo
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    Möncke, Doris
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology. National Hellenic Research Foundation, Greece;Alfred University, USA.
    Kamitsos, Efstratios
    National Hellenic Research Foundation, Greece.
    Segawa, Hiroyo
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology. National Institute for Materials Science, Japan.
    Karczewski, Jakub
    Gdańsk University of Technology, Poland.
    Ali, Sharafat
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    The effect of nitrogen on the structure and thermal properties of beryllium-containing Na-(Li)-Si-O-N glasses1919In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 522, article id 119585Article in journal (Refereed)
    Abstract [en]

    Two oxynitride glass series with the composition of 35Na2O-5BeO-(60-x)SiO2-xSi3N4 and 9Li2O- 27Na2O-5BeO-(59-x)SiO2-xSi3N4, were prepared. The glasses' topography and structure were studied by Scanning Electron Microscopy and Raman spectroscopy. The composition was analyzed by Inductively Coupled Plasma Optical Emission Spectrometer, SEM-EDS and nitrogen and oxygen elemental analyzer. Na-(Li)-Be-silicate glasses were found to contain up to approximately 3.4 (or 5.2 for EDS measurements) at.% of N, respectively. The samples were homogenous in their topography and compositions of their cross-sections.

    The presence of three-fold coordinated nitrogen atoms in Na-Be-Si-O-N glasses results in higher degree of polymerization as was observed by Raman spectroscopy. The spectrum of analogous glasses with lithium did not show a significant decrease in Q2 units but exhibit the presence of Q4 units which also indicates a polymerization of the network. The incorporation of nitrogen in these glasses leads to the increase of the glass transition temperature and thermal stability.

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