Showing papers in "Journal of Non-crystalline Solids in 2013"

High entropy Ti20Zr20Cu20Ni20Be20 bulk metallic glass

Abstract: In this letter, we report that a new bulk metallic glass (BMG) of Ti 20 Zr 20 Cu 20 Ni 20 Be 20 , with a critical diameter of 3 mm, has been successfully fabricated using copper mold casting method. Different from most reported BMGs which possess one or two main constituents, this newly developed BMG possesses five elements with equal atomic concentration, which has been defined as high entropy alloy. This high entropy bulk metallic glass (HE-BMG) exhibits high fracture strength of 2315 MPa but a brittle behavior. The glass forming ability, mechanical property and phase transformation after annealing of the HE-BMG are discussed in detail. And a way for designing high entropy bulk glassy alloy has been proposed.

Trends and prospects for development of chalcogenide fibers for mid-infrared transmission

Abstract: The main directions of investigations and technological developments for improvement of technical and operational characteristics of optical fibers from chalcogenide glasses are considered. The methods of ultra purification of various chalcogenide glasses from the limiting impurities, the techniques of preparation of low loss optical fibers, including microstructured fibers, have been developed. The prospects for the use of chalcogenide fibers in telecommunication and non-linear optics systems are discussed.

Characteristics of the Li2O–Li2S–P2S5 glasses synthesized by the two-step mechanical milling

Abstract: Sulfide solid electrolytes have high ion conductivities of 10 − 4 to 10 − 2 S cm − 1 at room temperature. However, sulfide electrolytes, which are hydrolyzed in air, generate H 2 S gas. In this study, an addition of Li 2 O to the 70Li 2 S·30P 2 S 5 (mol%) glass and synthesis procedures of the sulfide glasses were examined to suppress H 2 S gas generation. The addition of Li 2 O decreased H 2 S gas generation from the glass electrolytes. Moreover, the two-step synthesis, in which glasses were prepared by the reaction of Li 2 O and the 70Li 2 S·30P 2 S 5 glass prepared in advance, was extremely effective in suppressing H 2 S gas generation from the sulfide glass electrolytes. The Li 2 O–Li 2 S–P 2 S 5 glass electrolytes prepared by the two-step synthesis showed relatively high conductivity of more than 10 − 4 S cm − 1 at room temperature.

Optical absorption and structural studies of bismuth borate glasses containing Er3 + ions

Abstract: Glasses with composition xBi 2 O 3 –24Na 2 O–(75 − x)B 2 O 3 –1Er 2 O 3 (where x = 0, 5, 10, 15, 25, 33, 40 mol%), were prepared by the melt quenching technique The effect of Bi 2 O 3 content on thermal stability, optical properties and structures of these glasses is systematically investigated by X-ray diffraction, infrared spectroscopy and DTA techniques The variations in the optical band gap energies, with Bi 2 O 3 content have been discussed in terms of changes in the glass structure Urbach energy increases with increasing Bi 2 O 3 content in the present glass system It is found that the density, molar volume and optical basicity increase with increasing Bi 2 O 3 The glass transition temperature (T g ) of the samples was found to decrease with the Bi 2 O 3 content IR measurements revealed an existence of trigonal BO 3 pyramid, tetrahedron BO 4 , pyramidal BiO 3 and octahedron BiO 6 structural units in the network of the investigated glass Furthermore, a decrease in BO 4 and an increase in BO 3 take place against the increase of x which means that, Bi 2 O 3 plays the role of network modifier in the structural network

Review. Functional glasses and glass-ceramics derived from iron rich waste and combination of industrial residues

Abstract: Wastes from industrial processes and energy generation facilities pose environmental and health issues. Diversion of waste from landfill to favour reuse or recycling options and towards the fabrication of marketable products is of high economic and ecologic interest. Moreover safe recycling of industrial wastes is necessary and even vital to our society because of the increasing volume being generated. Glasses and glass–ceramics attract particular interest in waste recycling concepts. Novel and/or improved glass-based products from wastes should meet a variety of demands, among which the functional requirements are paramount. The investigations reviewed in this paper focusing on iron rich waste materials demonstrate the potential of turning these silicate based wastes into functional glass-based products. By properly selecting iron oxide containing residues and processing parameters, functional glass-based products with suitable catalytic activity, magnetic, optical and electrical properties can be obtained. The possibility of fabricating highly porous materials using different types of wastes for sound and thermal insulating as well as catalytic support applications is also discussed based on literature results. Thus, porosity can be considered to achieve particular properties in waste derived products.

Temperature and modifier cation field strength effects on aluminoborosilicate glass network structure

Abstract: The effect of temperature on the structure of barium aluminoborosilicate liquids has been studied by 11 B, 27 Al, and 17 O MAS NMR spectroscopies using glass samples prepared with different cooling rates and thus different fictive temperatures. Concentrations of BO 3 groups and of non-bridging oxygen (NBO) increase with increasing fictive temperature. The abundance of boron structural groups and NBO quantified by 11 B MAS NMR and 17 O MAS NMR confirms that the change of NBO corresponds to the boron coordination change through the structural reaction BO 4 ↔ BO 3 + NBO, which shifts to the right at higher temperature. The reaction enthalpy of this reaction is about 40 kJ mol − 1 . Configurational heat capacities have been estimated from differential scanning calorimetry (DSC) data; the redistribution of boron species (BO 4 /BO 3 ) contributes about 30% to these values. Results for barium aluminoborosilicates are compared with our previous study of sodium and calcium aluminoborosilicates with same stoichiometry [1] to understand how the modifier cation field strength affects the glass network structure. The modifier with higher field strength promotes the formation of BO 3 group and NBO, and the additional NBO helps to stabilize the modifier cation in the melt structure and lower the reaction enthalpy change of the speciation reaction.

Mixed alkaline earth effect in sodium aluminosilicate glasses

Abstract: article i nfo While the mixed alkali effect has received significant attention in the glass literature, the mixed alkaline earth effect has not been thoroughly studied. Here, we investigate the latter effect by partial substitution of magnesium for calcium in sodium aluminosilicate glasses. We use Raman and NMR spectroscopies to obtain insights into the structural and topological features of these glasses, and hence into the mixed alkaline earth effect. We demonstrate that the mixed alkaline earth effect manifests itself as a maximum in the amount of bonded tetrahedral units and as a minimum in liquid fragility index, glass transition temperature, Vickers microhardness, and isokom temperatures (viz., the temperatures at η =1 0 13.5 and 10 12.2 Pa s). The observed min- ima in fragility, glass transition temperature, and isokom temperature are ascribed to bond weakening in the local structural environment around the network modifiers. We suggest that, since the elastic properties of the investi- gated system are compositionally independent, the minimum in Vickers microhardness is closely correlated to the minimum in isokom temperatures. Both of these properties are related to plastic flow and the translational motion of structural units, and hence both may be related to the same underlying topological constraints. This indicates that there might not be any significant difference in the onset of the rigid sub-Tg constraints for the inves- tigated compositions.

Influence of network bond percolation on the thermal, mechanical, electrical and optical properties of high and low-k a-SiC:H thin films

Abstract: As demand for lower power and higher performance nano-electronic products increases, the semiconductor industry must adopt insulating materials with progressively lower dielectric constants (ie low-k) in order to minimize capacitive related power losses in integrated circuits However in addition to a lower dielectric constant, low-k materials typically exhibit many other reduced material properties that have limited the ability of the semiconductor industry to implement them In this article, we demonstrate that the reduced material properties exhibited by low-k materials can be understood based on bond constraint and percolation theory Using a-SiC:H as a case study material, we utilize nuclear reaction analysis, Rutherford backscattering, nuclear magnetic resonance and transmission Fourier transform infra-red spectroscopy measurements to determine the average coordination (〈r〉) for these materials Correlations of 〈r〉 to Young's modulus, hardness, thermal conductivity, resistivity, refractive index, intrinsic stress, mass density and porosity show that an extremely wide range in material properties (in some cases several orders of magnitude) can be achieved through reducing 〈r〉 via the controlled incorporation of terminal Si Hx and C Hx groups We also demonstrate that the critical point at 〈r〉 ≤ 24 predicted by constraint theory exists in this material system and places limitations on the range of properties that can be achieved for future low-k a-SiC:H materials

Preparation and characterization of TeO2–WO3–Li2O glasses

Abstract: Glasses in the TeO 2 –WO 3 –Li 2 O system were prepared by using conventional melt-quenching technique. Glass formation range of the system and thermal, physical and structural features of the ternary glasses were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and FTIR analysis according to the equimolar substitution of TeO 2 by WO 3 + Li 2 O and increasing Li 2 O content at constant TeO 2 . Thermal behavior of the glasses was studied in terms of glass transition temperature ( T g ), crystallization temperature ( T c / T p ) and glass stability against crystallization ( ∆T ). Density ( ρ ), molar volume ( V M ), oxygen molar volume ( V O ), oxygen packing density (OPD), average cross-link density ( n — c ), Poisson's ratio ( μ cal ) and number of bonds per unit volume ( n b ) values were calculated for the physical investigation of the glasses. FTIR spectra of the glasses were interpreted in terms of the structural transformations on the glass network by the changing composition.

Mixed alkali effects in Bioglass® 45S5

Abstract: Bioactive glasses, particularly Bioglass® 45S5, have been used to clinically regenerate human bone since the mid-1980s; however, their high crystallisation tendency still limits their range of applications. In order to develop new bioactive glass compositions, which combine high bioactivity with good processing of the melt, a deeper understanding of the role of modifier oxides on the structure and thermal properties of the glasses is required. Here, the influence of different alkali cations, Li 2 O, Na 2 O and K 2 O, on the properties of Bioglass® 45S5 has been investigated. Potassium cations expanded the silicate network, making it less compact, and thereby lowered hardness and Young's modulus. Lithium cations, on the other hand, made the silicate network more compact, which increased both hardness and Young's modulus. Structural analyses suggest non-random partitioning of modifier cations between the silicate and orthophosphate phase in mixed-alkali compositions. Transition and crystallisation temperatures of glasses containing two alkali cations showed the typical mixed alkali effect, with temperatures being lower than those of glasses containing one alkali cation only. Substitution of Na for Li or K resulted in an increased processing window (temperature range between T g and the onset of crystallisation) with the exception of the fully substituted potassium glass, which had the smallest processing window of all glasses. Taken together, these results suggest that bioactive glasses in which sodium is partially substituted (particularly with potassium) are of great interest to improve the processing, making the glasses more suitable for sintering or fibre drawing applications.

Radiative characteristics of opacifier-loaded silica aerogel composites

Abstract: Radiative characteristics of opacifier-loaded silica aerogel composites such as specific spectral extinction coefficient and Rossland mean extinction coefficient were usually calculated by the Fourier infrared spectral experiment and the Beer law. For the composites, it needs lots of experiments to find the proper opacifier categories, contents, and sizes, hence, the optimal design becomes difficult. Based on this reason, this work proposes a theoretical method with four sub-models to evaluate the radiative characteristics of opacifier-loaded silica aerogel composites. First, the Fourier infrared spectral experiment and the modified Kramers–Kronig (K–K) relation are used to calculate the basic optical constants of the opacifier (complex refractive index). Second, the extinction efficiency of a single opacifier particle is calculated based on its complex refractive index. Third, the spectral and Rossland extinction coefficients of opacifier particle assemble are calculated by using extinction efficiency and mass fraction of opacifier. Finally, the spectral and Rossland extinction coefficients and radiative heat conductivity of the composite are obtained. The radiative characteristics of six kinds of opacifiers with various particle diameters are investigated by using the present models. The results show that optimal opacifier and its diameter are strongly temperature-dependent. The optimal diameter of opacifier reduces with increased temperature, and SiC is the best choice due to its high-temperature stability. A gradient design of composite is proposed based on the temperature-dependent optimal opacifier and its diameter, which significantly reduces radiative heat transfer compared to the traditional design.

Radiative heat transfer study on silica aerogel and its composite insulation materials

Abstract: This paper studies the thermal radiative transfer in silica aerogel and silica aerogel composite insulation materials (a xonotlite–aerogel composite and a ceramic fiber–aerogel composite) The spectral transmittances of silica aerogel, xonotlite-type calcium silicate, and ceramic fiber insulation materials–all considered semi-transparent mediums capable of absorbing, emitting, and scattering thermal radiation–are measured with a Fourier transform infrared spectrometer (FTIR) at different infrared wavelengths ranging from 25 to 25 μm The spectral transmittances are used to determine the specific spectral extinction coefficient and the specific Rosseland mean extinction coefficient of each sample The radiative conductivity of each sample, deduced from the overall thermal conductivity measured using the transient hot-strip (THS) method, is compared against diffusion approximation predictions by using the measured spectral extinction coefficient The results show that the spectral extinction coefficients of the samples are strongly dependent on the wavelength, particularly in the short wavelength regime (

Raman and IR investigation of silica nanoparticles structure

Abstract: In the present investigation we report experimental data regarding the Raman and Infra-Red (IR) absorption activities of commercial silica nanoparticles. We compared the data of the nanoparticles with the ones acquired in the same experimental conditions for commercial bulk silica. By this comparison we highlighted that the variability of the spectral features of the matrix related Raman and IR bands in the nanoparticles is above the one observed for the bulk systems before any treatments. Furthermore, by studying nanoparticles with different sizes (diameters from 40 to 7 nm) and applying the shell-model we can suggest that the core network of the nanoparticles is close to the one encountered in the bulk materials. By contrast for the surface shell, having a thickness of about 1 nm, as suggested by previous investigations, the structure is strongly modified. In fact, from Raman and IR data it appears that the Si–O–Si angle has a lower main value than those encountered in bulk systems and that the ring statistic is shifted towards lower member rings.

Effects of processing conditions on silica aerogel during aging: Role of solvent, time and temperature

Abstract: Effective parameters that enhanced mechanical properties of silica aerogel during aging were investigated. Silica aerogel was made by tetraethyl orthosilicate (TEOS), water, methanol and ammonium fluoride (NH4F) as catalyst using a one-step method. Aging on the samples were performed under three different solvents including n-hexane, methanol and water for different time periods and also different temperatures. Subsequently, solvent exchange with n-hexane, modification under trimethyl chlorosilane (TMCS) solution and the ambient pressure drying (APD) were applied on all samples. The Fourier transform infrared spectroscopy (FTIR), Brunauer, Emmett and Teller (BET) method and compression tests were carried out on the produced samples. Both the compression strength and compression modulus of the gel increased with increasing of the time and temperature of aging. Those samples aged under water showed higher mechanical properties. On the contrary, the specific compression strength and modulus of samples aged in water were declined drastically.

Raman spectroscopic study of the structural properties of CaO–MgO–SiO2–TiO2 slags

Abstract: Raman spectra of CaO–MgO–SiO2–TiO2 slags were carefully analyzed to obtain the effect of TiO2 on the slag structures and the results are important for a better understanding of the behaviors of Ti-bearing slags. Gaussian deconvolutions of the Raman curves provide us with a deep insight into various structural units of the slags. The silicate network was more polymerized because of the increase of TiO2. Q2 (silica tetrahedra with two bridging oxygens) and Q3 species increase at the cost of Q0 and Q1 species. A significant fraction of Ti4 + plays the role of network formers and enters the silicate network, while some other Ti4 + exist in the slags in the form of TiO44 − monomers suggested by ~ 790 cm− 1 bands. A small content of 6-coordinated Ti4 + occurs when the fraction of TiO2 is relatively high. 5-Coordinated Ti4 + indicated by 870 cm− 1 may also appear and help the initial addition of Ti4 + into silicate network.

Adjustable structural, optical and dielectric characteristics in sol–gel PMMA–SiO2 hybrid films

Abstract: The structural, optical and dielectric characteristics of PMMA–TMSPM–SiO2 hybrid thin films, synthesized by sol–gel, were studied as a function of the molar concentration of the coupling agent (TMSPM) in the hybrid precursor solution. It was possible to obtain very homogenous films, with improved thermal stability and variable organic and inorganic composition. The hybrid films showed high uniformity, excellent optical transparency and tunable refractive index from 1.447 to 1.490 at 633 nm depending on the PMMA fraction in the films. The formation of both organic and inorganic components and their interaction in the hybrid material were confirmed by the analysis of the ATR–FTIR spectra, suggesting changes in the film structure caused by the variations of the TMSPM concentration. The dielectric constant of the hybrid films, determined from capacitance–voltage (C–V) measurements performed in metal–insulator–metal (MIM) configuration, had unexpectedly high values between 5 and 14, increasing with decreasing TMSPM molar ratio. Such high dielectric constant values were attributed to highly polarizable OH and C C groups in the hybrid films, OH being part of the residual precursor solvents and C C the result of incomplete conversion of precursor monomer (MMA) into polymer (PMMA), as shown by FTIR measurements. Furthermore, the dielectric constant of the hybrid films was modeled according to an effective media approximation model, taking into account the constituting organic and inorganic phases, residual O H and C C groups.

Optical spectroscopic analysis of cupric oxide doped barium phosphate glass for bandpass absorption filter

Abstract: CuO nanoparticles (25 nm) have been prepared by using co-precipitation method. The formed CuO powders were doped with barium phosphate glass with a series of x CuO–(20 − x )BaO–30ZnO–10Na 2 O–40P 2 O 5 in molar ratio with x = 2, 4, 6, 8, 10 and 12 and were prepared by using conventional quenching melts technique. The density has been measured by using the conventional Archimedes method, the molar volume was calculated and found, and the density and molar volume are trended in the same direction by increasing the CuO contents. The investigation of the glass state has been measured using XRD technique. The results show that no natural broadening peaks that form crystals, which proofed the systems, are completely in glass state. Some optical spectroscopic analysis was calculated from the absorbance and transmittance measurement like absorption coefficient, refractive index, extension coefficient, the optical energy gap, the cut off in UV and IR bands to the bandpass filter, which confirmed the optical properties of this type of filter.

Effect of gamma radiation on ultraviolet, visible and infrared studies of NiO, Cr2O3 and Fe2O3-doped alkali borate glasses

Abstract: Borate glasses with basic composition xR2O.(100 − x)B2O3 where R = Na, K, were colored by doping with one of transition metal ions Ni, Cr, Fe or doping with mixing of them. The effect of glass composition and gamma ray irradiation on the optical and infrared absorption spectra was studied and interpreted in terms of structural concepts. A resolution of the observed absorption spectra showed the existence of each transition metal ion in the possible coordination state according to the composition of the glass. The IR measurements reveal characteristic absorption bands due to various groups of triangular and tetrahedral borate network. The introduction of trace amounts of mixed dopants Cr2O3, Fe2O3 and NiO has no major effect on the structure of the studied glasses. The induced absorption spectra exhibit the characteristic absorption bands caused by the intrinsic base borate glass and the respective transition metal ions. The response of the doped glasses to gamma ray irradiation is assumed to be related to the formation and annihilation of the induced color centers.

Application of modified Judd–Ofelt theory and the evaluation of radiative properties of Pr3 +-doped lead telluroborate glasses for laser applications

Abstract: Praseodymium doped lead telluroborate (PTBPr) glasses were prepared by conventional melt quenching method. The absorption spectra have been analyzed to evaluate the intensity parameters applying the standard and the modified Judd–Ofelt theories. The emission spectra under 3P2 level excitation (λex = 447 nm) were investigated to estimate the laser characteristic parameters. These emission measurements together with Judd–Ofelt intensity parameters (Ωλ = 2,4,6) have been used to calculate the radiative transition probabilities, fluorescence branching ratios and radiative lifetimes of the transitions from 3P0 and 1D2 levels to their lower lying levels. The quenching of fluorescence intensity and experimental lifetime with the increase of Pr3 + concentration and the shift of 1D2 → 3H4 emission peak towards longer wavelengths was discussed. The non-radiative losses due to multiphonon and energy transfer relaxations were also explained. The Commission Internationale de I'Eclairage (CIE) coordinates, color purity and optical band gap energy values were evaluated. Some of the basic laser characteristics such as stimulated emission cross-section, optical and bandwidth gain parameters and fluorescence quantum efficiency were also reported.

Physical properties of the GexSe1 − x glasses in the 0 < x < 0.42 range in correlation with their structure

Abstract: Physical properties, including mechanical, thermal and optical properties, have been investigated for chalcogenide glasses in the GexSe1 − x system, for x ranging between 0 and 0.42. In the 0 = 2.4). Conversely, the chemical threshold ( = 2.67) clearly induces a change in the compositional trend of these properties. In the x > 1/3 range, Tg decreases and the elastic moduli markedly increase, which is not expected from the continuously reticulated model. The change of the physical properties in this range is an indicator of the existence of separated Ge-rich domains.

Optical and structural characterization of samarium and europium-doped phosphate glasses

Abstract: The work deals with optical and structural properties of aluminophosphate glasses from Li 2 O–BaO–Al 2 O 3 –La 2 O 3 –P 2 O 5 system containing Sm 3 + and Eu 3 + ions. X-ray fluorescence (XRF) has been used to establish the elemental composition of these materials. The influence of Sm 3 + and Eu 3 + ions on the optical properties of these glasses has been investigated in relation with their structural characteristics. The optical behavior of these materials has been studied by ultra-violet–visible (UV–Vis) spectroscopy, revealing absorption maxima specific to the doping ions. Structural information via vibration modes was provided by Fourier Transform Infrared (FTIR) absorption spectra evidenced as P O P symmetrical and asymmetrical stretching vibration modes, P O P bend, PO 2 − symmetrical and asymmetrical stretching vibration modes, P O stretching vibration mode and P O H water absorbance. Raman spectra acquired by 514.5 nm laser excitation disclosed peaks specific to metaphosphate network. Information about the elemental compositional homogeneity of Sm 3 + and Eu 3 + -containing glasses as well as about the defects of the doped-glasses is revealed by scanning electron microscopy/energy dispersive spectrometry (SEM/EDS). Fluorescence spectroscopy measurements put in evidence important fluorescence peaks found at 596 nm and 643 nm for Sm 3 + ions in phosphate matrix and 611 nm and 700 nm in the case of Eu 3 + -doped glass.

Influence of lanthanum on borosilicate glass structure: A multinuclear MAS and MQMAS NMR investigation

Abstract: The physical and chemical properties of silicate glasses containing rare-earth elements (REEs), either as dopants or at higher concentrations, are sensitive to the REE structural and chemical environment. An unambiguous role of REEs in the glass structure still remains difficult to define because many configurations may exist and are strongly composition-dependent. The structural configuration of lanthanum and its interactions with sodium and calcium are examined here in borosilicate glasses. The impact of lanthanum and calcium substituted for sodium on the boron speciation is investigated by 11B MAS NMR. The resulting 29Si MAS NMR spectra and their interpretations are discussed. A quantitative approach of 17O MQMAS NMR data with the reconstruction of 17O NMR parameter distributions provides an overview of lanthanum distribution and its interactions with the other cations in the vitreous network. No clustering of lanthanum atoms is observed; they are uniformly distributed in the glass structure, surrounded by about 6 non-bridging oxygen atoms and mixed with sodium and calcium atoms to the detriment of the number of BO4 groups. These data provide a better understanding of the addition of rare earths in the glass and of the conditions favorable to their uniform distribution in soda-lime borosilicate glass matrices.

Densification and plastic deformation under microindentation in silicate glasses and the relation to hardness and crack resistance

Abstract: To quantify and study the densification and plastic deformation under Vicker's indentation we prepared a series of simple soda-lime-silicate glasses with different modifying ion contents and four glasses with constant silica content but potassium and/or barium substituted for sodium and/or calcium. The densification and plastic deformation in these glasses were determined using atomic force microscopy (AFM) by measuring each sample twice, i.e., once immediately following indentation, and once after annealing to relax the densified volume. The results show that the densified volume of the glasses decreases approximately linearly with the bulk modulus, and the plastic deformation volume with silica mole fraction. These results have important implications in the prediction of hardness and crack resistance (i.e. load for crack initiation) from composition.

Nucleation of the electroactive β-phase, dielectric and magnetic response of poly(vinylidene fluoride) composites with Fe2O3 nanoparticles

Abstract: Iron oxide magnetic nanoparticles (IOMNPs) with average size of ~ 15 nm, synthesized by a co-precipitation technique were included in a poly(vinylidene fluoride) (PVDF) matrix with the objective to produce IOMNPs/PVDF multiferroic nanocomposites by solvent casting and melt processing. Increasing concentration of the IOMNPs nucleates the piezoelectric β-phase of the polymer, decreases the degree of crystallinity and increases the melting temperature of the polymer matrix leading to electroactive materials with large potential for sensor and actuator applications. The macroscopic magnetic and dielectric response of the composites depends on the weight fraction of IOMNPs nanoparticles in the nanocomposite, with both magnetization and dielectric constant increasing for increasing filler content. A typical superparamagnetic behavior was observed in the IOMNPs/PVDF composites.

Description of enthalpy relaxation dynamics in terms of TNM model

Abstract: This article critically reviews the current methodologies for description of enthalpy relaxation dynamics in amorphous materials in the glass transition range. In particular, the description in terms of the Tool–Narayanaswamy–Moynihan (TNM) model is discussed. Advantages and disadvantages of particular methodologies are demonstrated and suggested explanations of possible data-distortive effects involve thermal gradients, improperly designed temperature programs, or incorrectly applied subtraction of the thermokinetic background. In addition, a novel ultimate simulation-comparative method is presented, applicable even for extremely distorted differential scanning calorimetry data. Based on the introduced advantages and disadvantages of particular methodologies, an optimum generalized algorithm for precise and reliable evaluation of TNM parameters is proposed, utilizing both curve-fitting and alternative non-fitting techniques.

Spectroscopic and dielectric studies of Sm3 + ions in lithium zinc borate glasses

Abstract: In the present work, different concentrations of Sm 3 + ions doped lithium zinc borate glasses (LBZnFSm: Li 2 CO 3 + H 3 BO 3 + ZnF 2 + Sm 2 O 3 ) were prepared by melt quench technique. Thermal stability, amorphous nature and vibrational modes of lithium zinc borate glasses have been studied by using differential scanning calorimetry, X-ray diffraction and Fourier transform infrared spectroscopy, respectively. Spectroscopic characterization of Sm 3 + -doped lithium zinc borate glasses through absorption, excitation, emission and decay spectra has been carried out. Using absorption spectra nephelauxetic ratios, bonding parameters and energy band gap of the glass were evaluated. Judd–Ofelt (JO) intensity analysis had been performed and JO parameters were estimated for 1.0 mol.% Sm 2 O 3 doped lithium zinc borate glass. Radiative properties such as transition probabilities, branching ratios and radiative lifetime were estimated by using JO parameters. Stimulated emission cross-sections and effective bandwidths of each transition were obtained from the luminescence spectra. The decay curves of Sm 3 + -doped lithium zinc borate glasses exhibit single exponential nature for lower concentrations and gradually changes to non-exponential for higher Sm 3 + concentrations. The experimental life time, quantum efficiency and donor acceptor interaction parameters were also estimated using decay curves of 4 G 5/2 level of Sm 3 + ions in the present glasses. The non-exponential nature of the decay curves has been analyzed by Inokuti–Hirayama model indicating that ion interaction is of dipole–quadrupole nature. Dielectric studies of 0.1, 1.0 and 2.0 mol.% Sm 2 O 3 -doped glasses were undertaken and dielectric constants, Cole–Cole parameters and power-law parameters were also determined.

Structure–property correlations in highly modified Sr, Mn-borate glasses

Abstract: Highly modified borate glasses with the composition (1 − 2x)MnO–x(SrO–B2O3) (x = 0.46, 0.42, 0.36, 0.25, and 0.20) were prepared and investigated by Raman, infrared (IR), and electron paramagnetic resonance (EPR) spectroscopy. Optical properties were studied in regard to photoluminescence, optical absorption, and refractive index. The Mn2 +/Mn3 + equilibrium was shifted towards the divalent manganese ion as a result of the strongly reducing melting conditions employed in this work, which facilitate the preparation of transparent glasses with up to 80 mol% total SrO and MnO content. Changes in the optical and physical properties within this glass series were related to structural variations. The structure of glasses with relatively low MnO content was found to involve mainly trigonal [BO2O]− and tetrahedral [BO4]− metaborate groups, which are replaced progressively by pyroborate [B2O5]4 − and orthoborate [BO3]3 − triangular units upon increasing MnO content. At the highest modification level (x = 0.20) the structure is built of orthoborate isomeric species in triangular [BO3]3 − and tetrahedral [BO2O2]3 − configuration. The latter species form [B3O9]9 − rings, which reestablish some degree of network connectivity, as they involve three bridging and six non-bridging oxygen atoms, and this is reflected by the increase of the glass transition temperature for x = 0.25 over x = 0.20. Micro-Raman measurements showed structural inhomogeneities in these glasses due to chemical isomerization processes involving short- and medium-range order structures. Also, increasing MnO content was shown to cause MnO-clustering in the glasses as revealed by luminescence and EPR measurements.

Investigation of electrical and dielectric properties of antimony oxide (Sb2O4) semiconductor thin films for TCO and optoelectronic applications

Abstract: This work presents some electrical properties based on the impedance measurements as well as the dielectric constants on thermal evaporated Sb2O4 thin films additional to structural, opto-thermal and optical investigations which are reported previously by Ouni et al. in Journal of Non-Crystalline Solids (vol. 356 (2010) 1294–1299). The electrical conductivity and dielectric properties of Sb2O4 thin film were indeed studied using impedance spectroscopy technique in the frequency range 5 Hz–13 MHz at various temperatures (325–450 °C). The complex impedance diagram at different temperatures showed a single semicircle, implying that the response originated from a single capacitive element corresponding to the grains. AC and DC conductivities were studied to explore the mechanisms of conduction. It can be seen from the experimental data that the AC conductivity in thin films of Sb2O4 is proportional to ωs (s

Elastic and micromechanical properties of isostatically compressed soda–lime–borate glasses

Abstract: Isostatic pressure-induced changes in elastic constants and micromechanical properties of soda–lime–borate glasses of molar composition xNa2O⋅10CaO⋅(90 − x)B2O3 with x = 5, 15, and 25 were determined by performing Brillouin scattering and Vickers indentation experiments. An increase of the isostatic pressure up to 570 MPa resulted in an increase of Young's modulus of 19, 11, and 7% and of hardness at 9.81 N load of 33, 22, and 18% for x = 5, 15, and 25, respectively. The decrease in the resistance to crack initiation (ratio of at least 2) and the increase in the crack-to-indent ratio (change > 13%) followed the same compositional trend. Consequently, fracture toughness and brittleness of the soda–lime–borate glasses were negatively and positively correlated with isostatic pressure, respectively. These changes were correlated with the overall decrease of the molar volume.

Effect of the reduction treatment on the basalt continuous fiber crystallization properties

Abstract: Basalt continuous fibers were treated in H 2 /Ar atmosphere at 650 °С and 700 °C. The 57 Fe Mossbauer spectroscopy indicated that after the treatment at 650 °C all ferric cations reduced to ferrous. Reduction at higher temperature leads to metallic iron formation. DSC and XRD data indicated that crystallization process in reduced basalt fibers carried slower. Glass transition temperature decreases after the reduction due to the increase of amount of ferrous cations, that act as modifiers. Due to Fe 2 + /Fe 3 + ratio changing spinel-like phase crystallization ability decreases. Crystallization in reduced basalt fibers starts at lower temperature. The tensile strength of reduced fibers is higher than the tensile strength of basalt continuous fibers that were annealed at the same condition in air.