Stability Of Glasses Research Articles

Photoluminescence downshifting studies of thermally stable Dy3+ ions doped phosphate glasses for photonic device applications

Trivalent dysprosium (Dy3+) activated barium zinc lithium phosphate (BaZnLiP) glasses were prepared by employing melt quench routes. To understand the possible applicability of the prepared glasses in photonic device applications, numerous structural, optical, and radiative characteristics have been explored in detail. The non-crystalline character of BaZnLiP glass has been confirmed with the help of an X-ray diffraction pattern. The titled glasses doped with Dy3+ ions show several absorption peaks in the 330–1800 nm range with an indirect optical band gap of 3.41–3.76 eV. The Judd-Ofelt (J-O) theory was employed on the absorption profiles and estimated various radiative parameters for the Dy3+ ions activated BaZnLiP glasses. The Dy3+ ions activated glasses exhibit intense excitation at 350 nm and three sharp visible emissions at blue (4F9/2 → 6H15/2), yellow (4F9/2 → 6H13/2), and red (4F9/2 → 6H11/2). To ascertain the lasing potentialities of BaZnLiP glasses, the stimulated emission cross-section and branching ratios have been assessed by correlating the emission spectral information with the radiative parameters calculated from the absorption spectral features. The colorimetric properties show the coordinates situated in a bright white region. Temperature-dependent photoluminescence (TD-PL) spectral features recorded revealed the thermal stability of the as-prepared glasses. The explored distinctive features for Dy3+ ions activated BaZnLiP glasses suggested the superiority and direct utility of the as-prepared glasses in advanced photonic device applications such as lasers and w-LEDs.

Effect of composition and nanostructure on the mechanical properties and thermal stability of Zr100-xCux thin film metallic glasses

Thin film metallic glasses (TFMGs) are a novel class of materials showing a mutual combination of large plastic deformation in tension (>10% strain) and superior yield strength up to ∼ 3.5 GPa, which make them ideal candidates for applications such as flexible electronics. Nevertheless, a clear relationship between the atomic structure and mechanical properties of TFMGs has not yet been achieved. In particular, the role of composition in determining a different local atomic order and the effect of nanostructure on TFMGs properties must be further investigated. In this work, the mechanical properties and thermal stability of several amorphous Zr100-xCux TFMGs with either compact or fine columnar nanostructure were studied. The mediating role of composition in controlling crystallization temperature and hardness is here reported, which was found to increase from 4.6 to 7.7 GPa with increasing Cu content from 26 to 76 at.%. Moreover, plastic behavior and fracture resistance are shown to be highly dependent on both composition and nanostructure, with the Cu-rich and homogeneous film able to withstand elongation up to 2% strain before crack initiation. These results underline how atomic structure changes induced by composition can effectively influence TFMG properties, while demonstrating an approach to tune their behavior for various technological applications.

Borotellurite glass system doped with ZrO2, potential use for radiation shielding

Boro-tellurite former based glasses have recently sparked the interest of a number of researchers as a powerful optical device and shielding material. In this study, novel glasses of composition (60B2O3 –(10-x) CaO–10Na2O – 20TeO2 - xZrO2) where x is varied from 0.0 to 3.0% mol have been integrated using the melt-quenching method. Even at high concentrations of ZrO2, the obtained X-ray diffraction (XRD) patterns revealed the absence of crystalline peaks, confirming the glassy nature of all glass samples. The physio-chemical and radiation shielding characteristic were evaluated for specimens. The thermal transition temperatures as well as the glass thermal stability were determined using a Differential Scanning Calorimeter (DSC) test. Glass stability was found to deteriorate with increasing ZrO2 content. Radiation shielding characteristics were calculated theoretically using the Phy-X/PSD and WinXCom databases, and the findings reveal that the glass sample with the greatest ZrO2 concentration has the best gamma ray shielding in the energy range of (0.015 MeV−15 MeV). Furthermore, when compared to ordinary concrete, the computed fast neutron removal cross-section (FNRC) revealed a 36.84 percent improvement. The shielding results show that light-weight transparent ZrO2-doped boro-tellurite glasses compositions might be a promising candidate for a variety of shielding applications. The optimum proportion of ZrO2 additive is determined by the balance between greater shielding and glass stability qualities, which varies depending on the application.

Enhancement of optical properties and dielectric nature of Sm3+doped Na2O–ZnO–TeO2Glass materials

Samarium doped Na2O–ZnO–TeO2 (NZT) glasses were prepared by the melt quenching method. The glass-forming ability and glass stability of prepared glass was estimated by Hruby parameter using Differential Thermal Analysis (DTA) and Thermo-gravimetric Analysis (TGA). The study of FTIR spectra and X-ray diffraction described the ionic nature and the amorphous pattern of glass respectively. The absorption peaks were observed for the transitions 6H5/2-4P3/2 at 402 nm, 6H5/2-4M19/2 at 418 nm, 6H5/2-4I15/2 at 462 nm and 6H5/2-4I11/2 at 478 nm in the absorption spectra. The optical band gap energy (Eg) was calculated and observed to be decreased from 2.95 eV to 1.58 eV with doping concentration. The visible emission band was observed in the Sm3+ doped glass samples. The variation of dielectric constant with frequency was found to be independent for the frequency range 3 kHz - 2 MHz. The measurement of temperature-dependent dc conductivity showed Arrhenius type mechanism of conduction.

Crystallization and thermal stability of Ni-based metallic glass with high tungsten and boron

Non-isothermal crystallization behavior of the amorphous (Ni51W31.6B17.4)75Co25 alloy with high tungsten and boron content was investigated. Continuous heating DSC analyses of the amorphous samples revealed that the alloy undergoes crystallization with three-step. The thermal stability and crystallization kinetics of the samples were evaluated by Lasocka, Kissinger and Ozawa approaches. Activation energy calculated for the first crystallization step showed that the thermal stability of the NiCoWB alloy is higher than other Ni-based alloys. Avrami exponent value calculated for the early stage of the Niss-phase crystallization indicated a three-dimensional diffusion-controlled mechanism with increasing nucleation. The continuous heating transformation diagram plotted according to non-isothermal analyzes is consistent with the phases detected in isothermal heat treatments. The usability of the continuous heating transformation diagram of the alloy in isothermal heat treatment applications has been demonstrated.

Biodegradable Poly(D-L-lactide-co-glycolide) (PLGA)-Infiltrated Bioactive Glass (CAR12N) Scaffolds Maintain Mesenchymal Stem Cell Chondrogenesis for Cartilage Tissue Engineering.

Regeneration of articular cartilage remains challenging. The aim of this study was to increase the stability of pure bioactive glass (BG) scaffolds by means of solvent phase polymer infiltration and to maintain cell adherence on the glass struts. Therefore, BG scaffolds either pure or enhanced with three different amounts of poly(D-L-lactide-co-glycolide) (PLGA) were characterized in detail. Scaffolds were seeded with primary porcine articular chondrocytes (pACs) and human mesenchymal stem cells (hMSCs) in a dynamic long-term culture (35 days). Light microscopy evaluations showed that PLGA was detectable in every region of the scaffold. Porosity was greater than 70%. The biomechanical stability was increased by polymer infiltration. PLGA infiltration did not result in a decrease in viability of both cell types, but increased DNA and sulfated glycosaminoglycan (sGAG) contents of hMSCs-colonized scaffolds. Successful chondrogenesis of hMSC-colonized scaffolds was demonstrated by immunocytochemical staining of collagen type II, cartilage proteoglycans and the transcription factor SOX9. PLGA-infiltrated scaffolds showed a higher relative expression of cartilage related genes not only of pAC-, but also of hMSC-colonized scaffolds in comparison to the pure BG. Based on the novel data, our recommendation is BG scaffolds with single infiltrated PLGA for cartilage tissue engineering.

Marginal stability of soft anharmonic mean field spin glasses

We investigate the properties of the glass phase of a recently introduced spin glass model of soft spins subjected to an anharmonic quartic local potential, which serves as a model of low temperature molecular or soft glasses. We solve the model using mean field theory and show that, at low temperatures, it is described by full replica symmetry breaking. As a consequence, at zero temperature the glass phase is marginally stable. We show that in this case, marginal stability comes from a combination of both soft linear excitations—appearing in a gapless spectrum of the Hessian of linear excitations—and pseudogapped non-linear excitations—corresponding to nearly degenerate two level systems. Therefore, this model is a natural candidate to describe what happens in soft glasses, where quasi localized soft modes in the density of states appear together with non-linear modes triggering avalanches and conjectured to be essential to describe the universal low temperature anomalies of glasses.

Stability of acid volcanic glasses in alkaline solutions: Understanding their potential to participate in the alkali-silica reaction

Experimental laboratory tests were performed using volcanic glasses from Argentina of variable chemical composition and texture, in 1 N KOH, NaOH, Ca(OH)2 and combined NaOH + KOH + Ca(OH)2 solutions, at 40 °C and up to 10 weeks. The initial materials were characterized by petrography, chemical analysis, XRD, FT-IR and DSC-TGA. The reaction progress was evaluated by XRD, and the final products studied by SEM-EDS. The reactivity of the most reactive glass is attributed to a combination of its high porosity/permeability and alteration degree (indirectly assessed by the volatile mass loss up to ~250 °C). The glass silica content and Ca/(Al+Si) ratio could be other factors affecting the glass reactivity; however, more studies are needed to understand the influence of these variables.

Local symmetry predictors of mechanical stability in glasses.

The mechanical properties of crystals are controlled by the translational symmetry of their structures. But for glasses with a disordered structure, the link between the symmetry of local particle arrangements and stability is not well established. In this contribution, we provide experimental verification that the centrosymmetry of nearest-neighbor polyhedra in a glass strongly correlates with the local mechanical stability. We examine the distribution of local stability and local centrosymmetry in a glass during aging and deformation using microbeam x-ray scattering. These measurements reveal the underlying relationship between particle-level structure and larger-scale behavior and demonstrate that spatially connected, coordinated local transformations to lower symmetry structures are fundamental to these phenomena. While glassy structures lack obvious global symmetry breaking, local structural symmetry is a critical factor in predicting stability.

Nanoscale-to-Mesoscale Heterogeneity and Percolating Favored Clusters Govern Ultrastability of Metallic Glasses.

Comprehending and controlling the stability of glasses is one of the most challenging issues in glass science. Here we explore the microscopic origin of the ultrastability of a Cu-Zr-Al metallic glass (MG). It is revealed that the ultrastable window (0.7-0.8 Tg) of MGs correlates with the enhanced degree of nanoscale-to-mesoscale structural/mechanical heterogeneity and the connection of stability-favored clusters. On one side, the increased fraction of stability-favored clusters promotes the formation of a stable percolating network through a critical percolation transition, which is essential to form ultrastable MG. On the other side, the enhanced heterogeneity arising from an increased distribution in local clusters may promote synergistically a more efficient and frustrated packing of amorphous structure, contributing to the ultrastability. The present work sheds new light on the stability of MGs and provides a step toward next-generation MGs with superior stability and performances.

Improving the luminescence, hardness and thermal stability of silicate glass for white LED by precipitation of Ba2YNbO6 crystals

In this work, Dy3+-Eu3+ doped precursor glass and transparent glass-ceramics containing Ba2YNbO6 crystal phase have been designed by the melting crystallization method. It was proved by XRD and XPS that the target crystal phase was successfully obtained. 750 ℃/180 min was selected as the heat treatment condition, after analyzing the micro-morphology, fluorescence spectra, transmittance curves and Vickers hardness of glass-ceramics. Under this condition, the luminescence intensity and Vickers hardness of glass-ceramic were about 50% and 30% higher than that of precursor glass, respectively. The chromaticity coordinate of the 2.0%Dy3+-1.0%Eu3+ co-doped glass-ceramic was (0.4158, 0.3862), and the correlated color temperature was 3179 K. Its excellent stability to thermal quenching at LED working temperature (423–473 K) was observed and the luminescence intensity can be maintained above 89.6% of room temperature. The activation energy of 2.0%Dy3+-1.0%Eu3+ co-doped glass-ceramic was estimated to be 0.3548 eV by temperature-dependent emission spectra, and the color coordinate shift was small, about 5.4 × 10−3. The research results show that the glass-ceramic has good warm white luminescence properties and fluorescent thermal stability.

Spectroscopic properties of Er3+-doped lithium-modified bismuth tellurite glasses for broadband near-infrared emission

Er3+ ions doped tellurite glasses are very attractive for laser and photonic applications. In this work, the glass forming ability of bismuth tellurite glasses was investigated by adding Li2O, and an optimal glass stability was obtained with additional dopant of 8 mol% Li2O. Moreover, an intense near-infrared (NIR) emission at 1.5 μm was observed in Er3+-doped TeO2-Bi2O3-Li2O (TBL-xEr) glasses with the full width at half maxima (FWHM) from 76 to 114 nm. 2.7 μm and visible emissions were also measured to understand the competitive luminescent mechanism. The maximum emission intensity at 1.5 μm was observed in TBL-1.0Er, while it decreased as the Er2O3 concentration continued to increase due to energy transfer between 4I11/2 and 4I13/2 level. Furthermore, Judd-Ofelt theory was used to evaluate the spectroscopic characteristics including radiative transition probability, branching ratio and radiative lifetime of Er3+ ions through absorption spectra. Glass TBL-1.0Er presented a large calculated stimulated emission cross-section (σem) at around 1.5 μm (10.43 × 10−21 cm2) and a high quantum efficiency (76.16%). Hence, these results imply that the developed glasses are promising gain-medium candidates for broadband optical amplifiers.

Glass formation and devitrification behavior of alkali (Li, Na) aluminosilicate melts containing TiO2

The impact of TiO2 additions on the quenchability of melts derived from the stoichiometry of spodumene (LiAlSi2O6), eucryptite (LiAlSiO4) and nepheline (NaAlSiO4) was investigated by containerless melting. The results reveal a compositional dependence (Al2O3/SiO2 and M2O/Al2O3 ratios, M = Na or Li) of the role of TiO2 during devitrification. Amorphous samples incorporating up to 10 mol% TiO2 could be produced, above which devitrification invariably took place. Interaction of TiO2 with other glass components (such as Al2O3 and Na2O in nepheline glass) perceivably reduced glass stability, while eucryptite and spodumene glasses appeared only affected to the extent to which nanosized TiO2 polymorphs (TiO2(B), anatase and rutile) served as heterogeneous nucleation sites for quartz solid solutions, in which we inferred a substantial incorporation of Ti4+. A reduction in SiO2 content and a preference for peraluminous compositions stand out as viable compositional strategies to foster the glass-forming ability of TiO2-rich aluminosilicate melts.

Effect of B2O3 addition on thermal and optical properties of TeO2–ZnO–Bi2O3–TiO2 glasses

New tellurite glasses with composition (in mol%): 60TeO2–(30-x)ZnO–5Bi2O3–5TiO2-xB2O3 (where x = 0, 2.5, 5.0, 7.5 and 10.0) were fabricated using conventional melt quenching method. Compositional dependence of the glasses on their density, thermal, refractive index and optical properties were investigated. X-Ray Diffraction analysis was carried out to confirm the nature of the thus formed glasses. Density, refractive index, and absorption spectra were measured at room temperature from which other glass characteristics such as polaron radius, oxygen packing density, field strength, B3+ interatomic distance, band gap energy, and Urbach tail were determined. Thermal characterisation to determine the change in glass transition temperature, glass crystallisation, melting point, and glass stability was carried out using Differential Scanning Calorimetry. A discussion was made in order to understand the results in terms of the ratio of bridging oxygen to non-bridging oxygen ions (BO/NBO). It was found that the addition of B2O3 results in increasing oxygen packing density, glass transition temperature, BO/NBO ratio and band gap energy, while decreasing density, refractive index, field strength, glass stability and Urbach tail energy. With increasing B2O3 concentration density changed from 5.879 to 5.646 g cm−3, refractive index 1.875 to 1.741, working temperature range (ΔT = 66 °C) and phonon energy within the range of 736–740 cm−1.

Effect of W on the thermal stability, mechanical properties and corrosion resistance of Fe-based bulk metallic glass

In this work, the effect of refractory metal W on the thermal stability, mechanical properties and corrosion resistance of Fe36Cr23Mo18-XWXC15B6Y2 (X = 0, 3, 5, 8, 10, 12, 15, 18) bulk metallic glasses (BMGs) were systematically investigated. The results showed that a wide composition range could be quenched to form BMG when the considerable refractory metal was introduced, although the higher mixing enthalpy of W than Mo between other elements (such as Fe, Cr, C) incited the deterioration of glass forming ability (GFA). The introduction of W significantly improved the thermal stability of the alloy system with glass transition temperature Tg and onset crystallization temperature Tx of Fe36Cr23Mo8W10C15B6Y2 BMG reached 923 K and 972 K, respectively. The W-bearing Fe-based BMGs also exhibited a very high hardness of 1400 HV and Young's modulus of 271 GPa, respectively. The extremely high thermal stability and elastic modulus were mainly derived from the strong chemical bonding between atoms. In addition, the large addition of W reduced the corrosion current density of the original alloy by an order of magnitude, which was mainly due to the formation of WO3 and the increase of MoO2 in the passivation film which inhibit the pit initiation and pit growth.

Investigating the Crystallization Process of Boron-Bearing Silicate-Phosphate Glasses by Thermal and Spectroscopic Methods.

Glasses and devitrificates from the SiO2–B2O3–P2O5–K2O–CaO–MgO system with constant contents of SiO2 and P2O5 network formers, modified by the addition of B2O3, were analyzed. All materials were synthesized by the traditional melt-quenching technique. The glass stability (GS) parameters (Krg, ∆T, KW, KH) were determined. The effect of the addition of B2O3 on the GS, liquation phenomenon, crystallization process, and the type of crystallizing phases were examined using SEM-EDS, DSC, XRD, and Raman spectroscopy imaging methods. It was observed that the addition of B2O3 increased the tendency of the glass to crystallize. Both phosphates (e.g., Ca9MgK(PO4)7, Mg3Ca3(PO4)4), and silicates (e.g., K2Mg5(Si12O30), CaMg(Si2O6), MgSiO3) crystallized in the studied system. The Raman spectrum for the orthophosphate Mg3Ca3(PO4)4 stanfieldite type was obtained. Boron ions were introduced into the structures of crystalline compounds at high crystallization temperatures. The type of crystallizing phases was found to be related to the phenomenon of liquation, and the order of their occurrence was dependent on the Gibbs free enthalpy.

Bonding Nature and Optical Properties of As2Te3 Phase‐Change Material

Chalcogenide phase‐change materials (PCMs) are a promising candidate for advanced memory and computing technologies. PCM‐based random access memories have entered the global memory market as storage‐class memory. In these products, the element arsenic plays an essential role in the selector layers, but how arsenic stabilizes the thermal stability of the chalcogenide glass remains elusive. Herein, thorough ab initio simulations are carried out to understand the chemical bonding, electronic structure, and optical properties of an important arsenic alloy As2Te3 in both crystalline and amorphous forms. In comparison with the homologue alloy Sb2Te3, the importance of homopolar bonds in stabilizing the amorphous phase of As2Te3 is revealed. Also, a strategy for the design of As x Sb2−x Te3 alloys with optimal material properties for nonvolatile photonic phase‐change applications is proposed.

Stability of metallic glasses under simulated space conditions

Metallic glasses (MGs), due to their exceptional properties resulting from the amorphous structures, may be potential candidates for space applications. However, the effect of space conditions on the stability of MGs is not clear, which should be taken into account for practical use. The present work assessed the thermal stabilities of MGs in the simulated space thermal fields under vacuum condition, with a specific focus on the cryogenic thermal cycling with a high ratio of the non-isothermal to isothermal durations and the cryogenic treatment for a long-duration. The dynamics and thermal properties of MGs under the simulated space conditions were found to be different than those in laboratory-based conditions. MGs with lower fragility values were also determined to show greater thermal stability. On this basis, rules for the selection of MGs to ensure thermal stability during future space applications were proposed.

Kinetics of structure formation in the vicinity of the glass transition

The structural stability of a gold-based bulk metallic glass (Au49Ag5.5Pd2.3Cu26.9Si16.3) was investigated by fast differential scanning calorimetry (FDSC). A chemically homogeneous glass (CHG) containing no quenched-in nuclei was produced using sufficiently fast cooling from the melt. To characterize the stability of this glass, the structural variations during annealing in the glassy state were investigated and a sequence of five different events observed. These are structural relaxation, an incubation period, nucleation, crystallization, and finally reorganization. The kinetics of these processes and the stability of the crystalline structures are discussed.

Effect of different sources of oxygen on the thermal stability and crystallization behavior of the Cu66Zr34 metallic glass

Effect of different sources of oxygen on the thermal stability and crystallization behavior of the Cu66Zr34 metallic glass