Glass Crystallization Temperature Research Articles

Study of thermal behavior of poly (lactic) acid composites with electron beam irradiated luffa fiber

Modification of surface of natural fibers by high energy electron beam irradiation (6 MeV) is a process for enhancing the adhesion between fiber and matrix. Composites reinforced with natural fiber have gained a prominent place in the field of research and innovation due to the advantages such as low cost, light weight and environment friendly factors. We have studied the thermal properties such as thermal degradation and crystallinity behavior of biodegradable composites using biodegradable polymer poly (lactic) acid (PLA) and fiber of luffa cylindrica (LC) fabricated by using injection molding technique. First, reinforcement LC fibers are irradiated with electron beam of 0.5, 1.0, 2.0, 4.0 and 10.0 Gy using 6 MeV linear accelerator at room temperature in presence of air. The thermal properties like glass transition temperature [Formula: see text], cold crystallization temperature [Formula: see text], melting peak temperature [Formula: see text] and thermal stability of the composites are studied using differential scanning calorimetry (DSC) in the temperature range from 30[Formula: see text]C to 250[Formula: see text]C and thermogravimetric analysis (TGA) in temperature range from 20[Formula: see text]C to 700[Formula: see text]C. The variation of these properties in response to the irradiation dose is analyzed in detail. It is observed that with increase in irradiation dose, glass transition temperature and crystallization temperature increase. However, the thermal stability of the composites is found to increase with increase in irradiation dose.

Influence of ZrO2 Addition on Structural and Biological Activity of Phosphate Glasses for Bone Regeneration.

Zirconium doped calcium phosphate-based bioglasses are the most prominent bioactive materials for bone and dental repair and regeneration implants. In the present study, a 8ZnO–22Na2O–(24 − x)CaO–46P2O5–xZrO2 (0.1 ≤ x ≤ 0.7, all are in mol%) bioglass system was synthesized by the conventional melt-quenching process at 1100 °C. The glass-forming ability and thermal stability of the glasses were determined by measuring the glass transition temperature (Tg), crystallization temperature (Tc), and melting temperature (Tm), using differential thermal analysis (DTA). The biological activity of the prepared samples was identified by analyzing X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy-energy dispersive spectra (SEM-EDS), before and after immersion in simulated body fluid (SBF) for various intervals of 0, 1 and 5 days, along with the magnitude of pH and the degradation of glasses also evaluated. The obtained results revealed that the glass-forming ability and thermal stability of glasses increased with the increase in zirconia mol%. The XRD, FTIR, and SEM-EDS data confirmed a thin hydroxyapatite (HAp) layer over the sample surface after incubation in SBF for 1 and 5 days. Furthermore, the development of layer found to be increased with the increase of incubation time. The degradation of the glasses in SBF increased with incubation time and decreased gradually with the increase content of ZrO2 mol% in the host glass matrix. A sudden rise in initial pH values of residual SBF for 1 day owing to ion leaching and increase of Ca2+ and PO43− ions and then decreased. These findings confirmed the suitability of choosing material for bone-related applications.

Changes of thermal properties and microstructure of nano‐ZnO/polylactic acid composite films during Zn migration

In this study, polylactic acid (PLA) films with different nano‐ZnO concentration (0, 1, 3, 5, 7, 9, and 15%wt) were obtained by casting method. Overall migration values and specific migration values were studied in different food simulants (10% [v/v] ethanol and isooctane). The results demonstrated that overall migration of the composite films and specific migration of Zn2+ was higher in 10% (v/v) ethanol solution than in isooctane solution. The release of Zn2+ was affected by the percentage of nano‐ZnO in the composite films and food simulants. The migration of Zn in this study was mainly caused by polymer softening and degradation leading to the dissolution of Zn. Scanning electron microscope analysis indicated that with the migration of Zn2+, the structure of the composite films changed greatly. Differential scanning calorimeter analysis indicated that the thermal stability was decreased and the glass transition temperature and crystallization temperature were reduced.

INFLUENCE OF DIFFERENT CaF₂ CONTENTS AND HEAT TREATMENT TEMPERATURES ON APATITE-MULLITE GLASS CERAMICS DERIVED FROM WASTE MATERIALS

An apatite-mullite glass ceramics composition derived from clam shell (CS) and soda lime silicate (SLS) glass has been fabricated from a heat treatment process of composition [xCaF2·(45−x)SLS·15CS·20Al2O3·20P2O5], where x is 5, 10, 15 and 20 (wt. %). The result concluded that the Ca and Si elements were found in the CS and SLS glass respectively as a major weight composition, thereby promoting the use of waste materials in the manufacture of glass ceramic samples. Besides, the CaF2 addition lowers the glass transition temperature (Tg) and crystallisation temperature (Tc) of the glass composition. The density and percentage of the linear shrinkage of the samples differs with the addition of CaF2 and various heat treatment temperatures. For the structural properties’ analysis, the formation of fluorapatite with a needle-like microstructure and mullite phase was enhanced with a higher CaF2 content, while the growth of the anorthite phase was observed to occur at a higher heat treatment temperature. Generally, the addition of ahigh CaF2 content with the help of heat treatment in apatitemullite glass ceramics composition greatly promotes the crystallisation of the fluorapatite phase, which is crucial for denture glass ceramics.

The Onset and Solidification Path of a Basaltic Melt by in situ Differential Scanning Calorimetry (DSC) and ex situ Investigations

The in-situ differential scanning calorimetry (DSC) technique has been applied to investigate the solidification paths of a basaltic liquid. The starting glass was heated up to 1300 °C, kept at this superliquidus temperature for 2 h and cooled at rates (∆T/∆t) of 7, 60, 180, 1000, and 1800 °C/h, down to 800 and 600 °C. Glass transition temperature (Tg), crystallization temperature (Tx_HR) and melting temperature (Tm) were measured by in-situ DSC spectra on heating. Tx measured along the cooling paths (Tx_CR) shows exothermic peaks that change from a single symmetric shape (7 and 60 °C/h) to multi-component patterns (180, 1000 and 1800 °C/h). The recovered products characterized by FE-SEM and EPMA-WDS show a phase assemblage of spinel (sp), clinopyroxene (cpx), melilite (mel), plagioclase (plg), and glass. Moreover, crystal size distributions (CSDs) and growth rates (Gmax and GCSD) were also determined. The crystal content slightly increases from 7 to 1800 °C/h. Faceted sp are present in all the run products with an amount always < 2 area%. Cpx increases from 7 to 1800 °C/h, changing its texture from almost faceted to dendritic between 60 and 180 °C/h. The area% of mel follows an asymmetric Gaussian trend, while plg nucleates only at 7 °C/h with a content < 2 area%. The coupling of DSC and SEM outcomes indicate that sp nucleate first, followed by cpx and mel (and/or plg). The increment of ∆T/∆t causes an increase of the CSD slope (m) and crystal population density per size (n0), as well as a decrease of the crystal size, for both cpx and sp. The log-linear CSD segments with different slopes at 7 and 60 °C/h suggest multiple nucleation events and crystal growth by coarsening. Gmax and GCSD for cpx and sp directly measured on the actual crystallization time by DSC spectra, both increase with the increasing of ∆T/∆t. The onset temperature of crystallization (Txi) decreases as ∆T/∆t increases, following an exponential trend that defines the uppermost portion of a time-transformation-temperature (TTT)-like curve. This analytical model allows us to quantitatively model the kinetic crystallization paths of dry basalts.

Bioactivity in SBF versus trace element effects: The isolated role of Mg2+ and Zn2+ in osteoblast behavior.

The bioactivity assay originally proposed by Kokubo is one of the most commonly used tests to indirectly evaluate the biocompatibility of bioactive glasses. However, extensive evidence has shown that trace elements present in biomaterials may stimulate cellular behavior in different ways even when no apatite formation is observed, i.e., in biomaterials with low or no bioactivity. To further elucidate this topic, we designed three different SiO2-rich bioglass compositions in which CaO was partially replaced by ZnO and MgO, two oxides known to affect bioactivity as well as osteoblastic behavior. The physicochemical changes induced by the presence of oxides and their effects on biological behavior, as well as the adhesion, proliferation and differentiation of human osteoblast-like osteosarcoma cells (MG-63), were followed by a bioactivity assay in simulated body fluid (SBF). The insertion of ZnO or MgO decreased the glass transition (Tg) and crystallization (Tc) temperatures as a function of the increase in nonbonding oxygens, which was directly reflected in the higher solubility. The release of Mg2+ ions from the MgO-containing samples inhibited the bioactivity in SBF, inducing high cell adhesion and proliferation and moderate ALP activity. The release of Zn2+ also inhibited the bioactivity in SBF but, in contrast to the release of Mg2+, induced low cell adhesion and proliferation and high ALP activity compared to the control.

Study of Thermal Behaviour of Poly(Lactic) Acid Composites with Gamma Irradiated Luffa Fiber

Modification of surface of natural fibers by high-energy gamma irradiation (6 MV) is a competent process for enhancing the adhesion between fiber and matrix. Composites reinforced with natural fiber have gained a prominent place in the field of research and innovation due to the advantages such as low cost, lightweight and environment friendly. We have studied the thermal properties of biodegradable composites using biodegradable polymer poly(lactic) acid and fiber of Luffa cylindrica (LC) fabricated by using injection molding technique. Before reinforcement LC fibers are irradiated with gamma rays of 0.5, 1 and 2 Gy using 6 MV linear accelerator at room temperature in the presence of air. The thermal properties like glass transition temperature (Tg), crystallization temperature (Tcc), melting peak temperature (Tm) and thermal stability of the composites are studied using differential scanning calorimetry in the temperature range from 30 to 250 °C and thermogravimetric analysis in temperature range from 20 to 700 °C. The variation of these properties in response to the irradiation dose and fiber loading is analyzed in detail. It is observed that with increase in irradiation dose, glass transition temperature and crystallization temperature are increasing. However, the thermal stability of the composites is found to decrease with increase in irradiation dose.

Abnormal isochronous crystallization behavior of Zr-Al-Ni-Cu-Fe-C bulk metallic glasses

(Zr53Al11.6Ni11.7Cu23.7)1-x(Fe77.1C22.9)x (x = 0–2.2 at.%) bulk metallic glasses (BMGs) were prepared by water cooling copper mold suction casting and their isochronous crystallization characteristics are investigated. The glass transition temperature, crystallization temperature, and crystallization peak temperature for all studied Zr-based BMGs firstly increase with increasing heating rate, and then decrease when the heating rate increases up to 60 K/min for the BMGs (0 ≤ x ≤ 0.88 at.%) and 80 K/min for the BMGs (1.32 ≤ x ≤ 2.20 at.%). The glass transition temperature, crystallization temperature, glass transition activiation energy, crystallization activiation energy, and activiation energy for crystallization peak temperature of the Fe- and C-free Zr-based BMG are the smallest among the studied BMGs, indicating that Fe and C additions are benificial to delaying the glass transition and the crystallization. Fe and C additions influence more significantly on the glass transition than on the crystallization. The local crystallization activiation energy for the Fe- and C-free BMG are the smallest among the studied BMGs, indicating that the crystallization is easy for the Fe- and C-free BMG. The peak height of local Avrami exponent and its corresponding crystallization fraction decrease with increasing heating rate except for the BMG (x = 1.32 at.%). The fragility indexes are 32–48 for the studied Zr-based BMGs. The present results are of guiding significance for preparing the excellent BMG composites by heat treatment and selecting suitable conditions for forming the BMGs.

Synthesis and Optical, Thermal, Structural Investigation of Zinc-Borate Glasses Containing V2O5

Vanadium pentaoxide (V 2 O 5 ) doped zinc borate (ZnB) oxide glasses that could be used in fiber optic cable cores in optoelectronics, in laser crystals in solar energy systems have been synthesized successfully. Structural characters of synthesized glasses were determined with differential scanning calorimeter (DSC) and Fourier-Transform infrared spectroscopy (FTIR). Glass transition (T g ), crystallization (T c ) and melting temperatures (T m ), and thermal stabilities ($\Delta$T) of the glasses were determined and also their association with the change in V 2 O 5 was explained. Structural units of boron and zinc that form the structure were determined according to FTIR data. As a result, it was determined that boron formed the glass matrix with BO 3 , BO 4 and boroxol ring structural units; on the other hand, zinc contributed to the glass matrix with tetrahedral ZnO 4 and octahedral ZnO 6 structural units, and vanadium usually had modifier role in the structure with its VO 4 and VO 5 structural units. V 2 O 5 ’s presence in the structure with increasing amount changes thermal, structural and physical properties. Among the properties that significantly change, the most important one is optical properties. Indirect optical band gaps, Urbach energies, refractive index values of these synthesized samples were determined, and quite clear shifts towards red region were observed in the transmittance and absorption spectra. Optical band gap decreased to 1.24 eV from 2.55 eV with increasing amount of V 2 O 5 ; on the other hand, Urbach energy was determined to increase to 0.630 eV from 0.246 eV. Densities, molar volumes of these synthesized glasses were also examined and commented on.

Influence of Vanadium on Optical and Mechanical Properties of Aluminosilicate Glasses

V2O5 was introduced up to 9 wt% in a peralkaline alkali earth aluminosilicate glass and up to 4.8 wt.% in two sodo aluminosilicate glasses, respectively a peralkaline and a peraluminous one. This introduction had a strong effect on thermal properties, and in particular on glass transition and crystallization temperatures of the peraluminous, which dropped by 89 K, while a moderate drop of ~ 20 K was observed for the two other glasses. Still, the glass stability and the glass-forming ability stay almost unmodified. The elastic properties measured by Brillouin spectroscopy show a decrease with added Vanadium for the depolymerized alkali earth aluminosilicate and the peraluminous sodo aluminosilicate, whereas they remain unchanged for the peralkaline one. Using Optical absorption the proportion of V5+, which is largely dominant, was found to follow the trend predicted using optical basicity considerations. The UV edge of the absorption spectra is assigned to charge transfers associated with V5+ in four-fold coordination. A large photoluminescence emission, centered at ~560 nm, is found for all glasses, upon excitation in the UV edge at both ~280 and ~350 nm. The emission band positions are relatively insensitive to the glass composition, whereas their intensities show variations of one order of magnitude between the sodium peralkaline composition and the calcium depolymerized glass. A too high concentration of V2O5 shows a quenching effect of the emission. Raman spectroscopy in polarized and cross-polarized permitted to identify the different environments around the V5+O4 tetrahedra. The highly polarizable V5+O4 tetrahedra associated with two non-bridging oxygens, vibrating at 860 cm-1, is proposed to be responsible for the more efficient charge transfer. At the opposite, the formation of VO4-AlO4 units is proposed to quench luminescence properties. Furthermore, we observed that upon the thermal treatment, the optical properties of the glasses are significantly modified without observable structural modifications or evolution of the elastic properties.

Effects of TiO2 content and thermal parameters on crystallization kinetics and mechanical properties of phosphate based glass system

The effects of TiO2 content and thermal parameters on crystallization kinetics and mechanical properties of sodium-calcium-phosphate glass system have been revealed in this study. From the DTA results using for crystallization kinetics study, the activation energies of crystallization and Avrami parameters have been calculated. The glass transition (Tg), crystallization temperature (Tp) and activation energy (E) were found to increase with the increase in the content of TiO2. The major crystalline phases were calcium pyrophosphate and sodium dititanium triphosphate along with rutile as the minor crystalline phase presented as phase separation in the samples. Mechanical properties were obtained from the microhardness measurements for all samples. It was found that the added TiO2 content caused positive effect while heat treatment temperature caused negative effect on Young's modulus, Knoop hardness and Vickers hardness.

The effects of cellulosic fillers on the mechanical, morphological, thermal, viscoelastic, and rheological properties of polyhydroxybutyrate biopolymers

AbstractThe aim of this study was to determine the effects of cellulosic fillers on the conventional and dynamic mechanical, thermal, morphological, and rheological properties of polyhydroxybutyrate (PHB) biopolymers. Polyhydroxybutyrate as a biopolymer matrix and cellulosic fillers including wood flour, microcrystalline cellulose, and cellulose nanofibrils (0.5 and 5 wt%) as reinforcing agents were used to produce the composite. According to the results obtained, the addition of 0.5 wt% cellulose nanofibrils improved both the flexural and tensile moduli of elasticity but other fillers and filler loading levels generally decreased the mechanical properties attributable to aggregations of fillers in the matrix. Thermal analysis results showed that the addition of cellulosic fillers did not influence the glass transition and crystallization temperature of the PHB whereas the crystallinity and melting temperature generally increased with the addition of the cellulosic fillers. Thermal stability of the composites generally improved with addition of the cellulosic fillers. The dynamic mechanical analysis results showed that both storage and loss moduli of all the samples generally decreased with increasing temperature. Elastic and viscous moduli of all the samples initially decreased with frequency but then generally increased according to the rheological analysis.

Study of the Effect of Calcium Substitution by Magnesium in the Vitreous System 3P2O5-2K2O-(1 - x) CaO-x MgO.

Phosphate glasses have potentially interesting properties that can be used in various applications. Recently, different studies are focusing on their dissolution behaviours that can be modified to suit some environmental applications, such as controlled-release fertilisers. In this work, magnesium had been suggested to improve the glass durability of 3P2O5-2K2O-(1 − x)CaO-xMgO glasses (0 ≤ x ≤ 1). Indeed, its effect on glass structure, thermal properties and most important dissolution behaviours were studied, in order to evaluate their suitability of being used as controlled-release fertilisers. Various compositions in which calcium was partially replaced by magnesium were prepared by melting at 800 °C. The samples were characterised by differential scanning calorimetry, density measurements, X-Ray diffraction, FTIR spectroscopy and Raman spectroscopy. The dissolution behaviours were investigated using inductively coupled plasma optical emission spectrometry ICP-OES, pH measurements and SEM. Substitution of calcium by magnesium reduced the glass density, owing to the lower atomic weight of magnesium compared to calcium, and caused an increase in glass transition and crystallisation temperatures. Magnesium substitution significantly improved the chemical durability of the glasses due to more covalent Mg–O bond than the Ca–O bond. This study demonstrated that 3P2O5-2K2O-0.3CaO-0.7MgO (x = 0.7) had a dissolution profile adequate to the criteria of controlled-release fertilisers and could be used to nourish the plants with phosphorus, potassium, calcium and magnesium.

The impact of the lead on the physicochemical and optical properties of the fluorophosphate glasses doped by Nd3+ ions

Fluorophosphate glasses of the composition 5Ba (PO3) 2- (38-x) AlF3-57RF2-xNdF3 were obtained, where R = Ba, Ca, Sr, Mg, Pb; x = 0.5, 3, 5 mol%. It was found that the introduction of lead fluoride reduces the glass transition and crystallization temperatures. It has been shown that for all systems containing MgF2, the formation of a uovite phase is characteristic. The UV-cutoff has shifted from 200 nm to 250 nm.

Synthesis of novel AgO-doped vanadium–borophosphate semiconducting glasses and investigation of their optical, structural, and thermal properties

Ag-doped vanadium–borophosphate glasses having 46V2O5–46P2O5–(8 − x)B2O3–xAgO as the base structure have been successfully synthesized with different compositions of AgO (x = 0, 2, 4, 6, 8 mol%) by the conventional melt-quenching technique. Density and molar volume values were calculated by Archimedes principle. The transmittance and absorbance spectra, XRD, and FTIR measurements of the glasses were performed at room temperature. While XRD data showed that the glasses had an amorphous structure away from crystallization, FTIR spectra showed that vanadium and phosphate compounds forming the glass network consisted of VO4, VO5 and PO3, PO2 structural units, respectively. It was observed that AgO, which replaces B2O3, acted as a modifier in the glass network. Direct and indirect band gaps of synthesized glasses were calculated using Tauc method. Urbach energies were also calculated. The glass transition temperature, crystallization temperature, and melting temperature values of the samples were determined with differential scanning calorimetry (DSC) in the range of room temperature to 1000 °C.

Synthesis, Physical, Mechanical and Antibacterial Properties of Nanocomposites Based on Poly(vinyl alcohol)/Graphene Oxide-Silver Nanoparticles.

The design of new materials with antimicrobial properties has emerged in response to the need for preventing and controlling the growth of pathogenic microorganisms without the use of antibiotics. In this study, partially reduced graphene oxide decorated with silver nanoparticles (GO–AgNPs) was incorporated as a reinforcing filler with antibacterial properties to poly(vinyl alcohol) (PVA) for preparation of poly(vinyl alcohol)/graphene oxide-silver nanoparticles nanocomposites (PVA/GO–AgNPs). AgNPs, spherical in shape and with an average size of 3.1 nm, were uniformly anchored on the partially reduced GO surface. PVA/GO–AgNPs nanocomposites showed exfoliated structures with improved thermal stability, tensile properties and water resistance compared to neat PVA. The glass transition and crystallization temperatures of the polymer matrix increased with the incorporation of the hybrid. The nanocomposites displayed antibacterial activity against Staphylococcus aureus and Escherichia coli in a filler content- and time-dependent manner. S. aureus showed higher susceptibility to PVA/GO–AgNPs films than E. coli. Inhibitory activity was higher when bacterial cells were in contact with nanocomposite films than when in contact with leachates coming out of the films. GO–AgNPs based PVA nanocomposites could find application as wound dressings for wound healing and infection prevention.

Influence of topological structure and chemical segregation on the thermal and mechanical properties of Pd–Si nanoglasses

Metallic nanoglasses are non-crystalline solids with interfacial regions, typically characterized by a modified short-range order and compositional gradients. These interfaces can act as nucleation sites for the formation of shear transformation zones during mechanical deformation, which gives rise to a deformation behavior distinct from the bulk glass counterpart. While various studies have investigated nanoglasses experimentally (mostly Fe–Sc) and in computer simulations (typically Cu–Zr), there is hitherto no study comparing compositionally identical nanoglasses and conventional metallic glasses by experiments and simulations. In this contribution, we investigate Pd–Si as a model system and compare nanoglasses produced by inert gas condensation with melt-spun ribbons. Molecular dynamics simulations and atom probe tomography provide evidence that glass–glass interfaces are primarily topological and chemical defects in this particular system. Differential scanning calorimetry shows a decrease in the glass transition and crystallization temperature of the nanoglasses compared to melt-spun ribbons. Nanoindentation and micropillar tests on Pd–Si metallic nanoglasses, however, provide evidence for shear band formation in both sample types, the melt-spun ribbons and nanoglass. Shear bands in the nanoglass samples appear more diffuse as compared to melt-spun ribbons. This is also evident from the reduced strain localization in the nanoglass. It is concluded that the topological inhomogenieties induced by forming glass–glass interfaces significantly affect the mechanical properties of nanoglasses.

Influence of selenium dioxide (SeO2) on properties of bioglass in SiO2-Na2O-CaO-P2O5 system

The influence of selenium dioxide on bioglass in (45.0-x) SiO2 24.5Na2O 24.5CaO 6.0P2O5 xSeO2 (x = 0.0, 0.5, 1.0, 1.5, and 2.0 wt%) system was investigated by preparing the glass through conventional melting and annealing method. The glass transition temperature (Tg), crystallization temperature (Tc), and density of prepared glasses were measured by differential thermal analysis and Archimedes’ principle respectively. The structural and microstructure analyses of glasses were characterized by Raman spectroscopy, Fourier transformed infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX). The formation of hydroxy apatite carbonate (HCA) layer for glasses was investigated by Raman spectroscopy, FTIR, SEM with EDS, pH measurement, ion concentrations analysis, and (%) weight loss after immersion in simulated body fluid (SBF) for 10 h to 14 days at 37.5°C. Experimental results showed that SeO2 substitution for SiO2 in the glass had increased glass density and molar volume whereas network connectivity was decreased. The addition of selenium oxide reduced the glass transition temperature and also crystallization temperature. The FTIR study of glass confirmed the P–O bonding after immersion for 14 days in SBF, which was also identified in the Raman spectroscopy. SEM of the 14 days immersed sample showed the formation of cauliflower like morphology of HA particles on the glass. pH and ion concentrations analysis also confirmed the formation of HCA layer after 14 days of immersion in SBF.

Synthesis and characterization of 50BaO - (5-x) Al2O3 - xR2O3 - 30B2O3 - 15SiO2(R = Nd, Gd) glass-ceramics

Glass-ceramics of composition 50BaO-(5-x)Al2O3-xR2O3-30B2O3-15SiO2(x = 0, 1, 2, 3,4,5 and R = Nd, Gd) have been synthesized by conventional melt quenching method followed by controlled heat treatment. The glass transition temperature (Tg) and crystallization temperature (Tc) have been observed from the Differential Thermal Analysis (DTA). The density of glasses and glass-ceramics has been measured. X-ray diffraction (XRD) technique has been used to confirm the amorphous nature of the glasses and to identify the crystalline phases formed in glass-ceramics. The structural changes due to heat-treatment have been investigated using Fourier Transform Infrared (FT-IR). The coefficient of thermal expansion (CTE) of glasses lie within the range (11.40 - 11.81) x 10−6/℃, and increased to (12.32 – 12.81) x 10−6/℃ for glass-ceramics. Microhardness values lie in the range 9.34 – 9.48 GPa. Owing to the suitable thermal properties these glass-ceramics can be considered as suitable materials as sealants for Solid Oxide Fuel Cells (SOFC).

Er3+,Yb3+-doped oxyfluorotellurite glasses—Impact of temperature on spectroscopic properties and optical sensor qualities

Oxyfluorotellurite glasses co-doped with erbium (0.5%) and ytterbium (2%, 5%) were manufactured from high purity reagents at 840 °C in air. Differential thermal analysis was used to estimate the temperatures of glass transition and glass crystallization of 2% and 5%Yb co-doped glasses. The effect of Yb3+ co-doping on relaxation dynamics of erbium excited states was demonstrated by the means of excitation, emission and fluorescence lifetime spectroscopy. Up-conversion luminescence spectra were studied in a function of temperature in the 295–675 K range, yielding information on thermal quenching of the emission and a temperature sensing model based on 2H11/2–4I15/2 to 4S3/2–4I15/2 erbium fluorescence intensity ratio. Application potential of the investigated material in optical sensor thermometry was evaluated. Maximum absolute and relative sensitivities were established at 6.45 × 10−3 K−1 at T = 675 K and 0.46 %K−1 at T = 400 K, respectively.