Glass Crystallization Temperature Research Articles

CdS/TiO2 heterojunction in glass matrix: Synthesis, characterization, and application as an improved photocatalyst

In this paper, sodium borosilicate glass SiO2-B2O3-Na2O-ZnO with 2 wt% CdS and 1 wt% TiO2 were prepared by the melt quench technique. For the growth of QDs, single-step heat treatment was given using glass transition (Tg) and glass crystallization (Tc) temperature. Hexagonal and anatase phase of grown CdS and TiO2 QDs were confirmed by XRD pattern. The size of powders was observed by SEM and cluster formation of CdS/TiO2 QDs was studied by FESEM. EDS pattern confirms the elemental composition which was used during synthesis. The structural changes due to heat treatment were explored by FTIR study. The growth of QDs and size determination was done by HRTEM. An increase in the size of QDs with annealing time was confirmed by optical absorption and emission spectra.Photocatalytic activity of Cd3:3 h (5.33 μm) and Cd3:5 h (3 μm) is investigated by degrading indigo carmine (IC) dye and degradation efficiency was found to be 85.30% and 91.64% respectively for 5 h.

Long-Term Physical (In)Stability of Spray-Dried Amorphous Drugs: Relationship with Glass-Forming Ability and Physicochemical Properties

This study shows the importance of the chosen method for assessing the glass-forming ability (GFA) and glass stability (GS) of a drug compound. Traditionally, GFA and GS are established using in situ melt-quenching in a differential scanning calorimeter. In this study, we included 26 structurally diverse glass-forming drugs (i) to compare the GFA class when the model drugs were produced by spray-drying with that when melt-quenching was used, (ii) to investigate the long-term physical stability of the resulting amorphous solids, and (iii) to investigate the relationship between physicochemical properties and the GFA of spray-dried solids and their long-term physical stability. The spray-dried solids were exposed to dry (<5% RH) and humid (75% RH) conditions for six months at 25 °C. The crystallization of the spray-dried solids under these conditions was monitored using a combination of solid-state characterization techniques including differential scanning calorimetry, Raman spectroscopy, and powder X-ray diffraction. The GFA/GS class assignment for 85% of the model compounds was method-dependent, with significant differences between spray-drying and melt-quenching methods. The long-term physical stability under dry condition of the compounds was predictable from GFA/GS classification and glass transition and crystallization temperatures. However, the stability upon storage at 75% RH could not be predicted from the same data. There was no strong correlation between the physicochemical properties explored and the GFA class or long-term physical stability. However, there was a slight tendency for compounds with a relatively larger molecular weight, higher glass transition temperature, higher crystallization temperature, higher melting point and higher reduced glass transition temperature to have better GFA and better physical stability. In contrast, a high heat of fusion and entropy of fusion seemed to have a negative impact on the GFA and physical stability of our dataset.

Structural and Thermal Properties of Montmorillonite/Ionic Liquid Composites.

Composites of montmorillonite K10 (MMT K10) and ionic liquid (IL) containing a 1-butyl-3-methyl-imidazolium cation ([BMIm]+) and various anions, such as bis (trifluoromethylsulfonyl) imide ([NTf2]−), trifluoromethanesulfonate ([OTf]−), and dicyanamide ([DCA]−) have been obtained in this work. A number of methods, such as dynamic light scattering (DLS), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermal gravimetry (TG), differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR) spectroscopy, and nitrogen adsorption–desorption have been used to characterize clay, and to study the structure and thermal behaviour of the composites. It has been found that the MMT K10 powder has a narrow particle size distribution with a peak at 246 nm and a mesoporous structure (SBET=195 m2/g). According to the FTIR spectra, MMT K10/IL interaction depends on the IL type. It has been identified that confined ionic liquid interacts with both clay and adsorbed water in accordance with the hydrophilicity and size of the anion, in the following order: [DCA]− > [OTf]− > [NTf2]−. Characteristic temperatures of glass transition, crystallization, and melting have been determined for the ionic liquids under study and their MMT K10 composites. It has been revealed that when IL is adsorbed on the surface of clay, the phase transitions in IL change. The greatest changes are observed in the case of BMImNTf2. By applying the method of thermogravimetric analysis, it is shown that composite formation is accompanied by a decrease in the IL thermal stability. Apparently, the highly developed surface of montmorillonite K10, obtained by acid treatment, plays a major role in the decrease in the IL’s thermal stability. The influence of the IL anion on the thermal and spectral characteristics of an MMT K10/IL composite was studied for the first time.

Sol-gel synthesis for stable green emission in samarium doped borosilicate glasses

In this work, novel green luminescent samarium doped-borosilicate glasses synthesized by the sol-gel route are reported. Although synthesis of crack-free monoliths was carried out in acid catalyzed reaction at room temperature with subsequent gelation at 50 °C, heating in N2/H2 atmosphere activated the luminescence. The results reveal the amorphous nature of glasses with embedded Sm2O3 nanoparticles in the reticular structure. From TEM analysis, the average particle size is estimated to be around 2.7 and 4.1 nm for the glasses without and with Na2O, respectively. The addition of Sm2O3 and Na2O promotes an increase in the glass transition and crystallization temperatures due to the boric anomaly. However, the optical band gap of undoped borosilicate glasses (3.65–3.86 eV) decreases with the addition of Sm2O3 and Na2O (3.39–3.57 eV). Furthermore, the observed green luminescence (545 nm), associated to 4F3/2 → 6H5/2 transition of Sm3+ ions in borosilicate glasses, is found to remain stable during the test period of 6 months. Therefore, glasses with high spectral purity and low-phonon losses have been obtained by easy sol-gel route, which is useful to promote the emergence of spectral transitions of higher energy with respect to the usually reported transitions at 600 nm (4G5/2 → 6H7/2).

Single Crystal Growth via Solid → Solid Transformation of Glass

Fabrication of single crystals of materials by conventional methods, which decompose or undergo incongruent melting upon melting, has limited the development of advanced technologies. A solution to this challenge was demonstrated a few years ago using laser heating in a localized region to minimize undesirable nucleation, and then scanning the beam to obtain single crystal growth at the crystallization temperature of glass that was usually significantly below its melting temperature. An overview of the development of this new mode of crystal growth including some new results and insights is presented here. The discovery of rotating lattice single crystal as a novel form of meta-material and its characteristics in relation to process parameters are discussed in detail. Preliminary observations suggest strong correlation between the shape of growth front and rate of lattice rotation. Finally, challenges to single crystal growth via solid → solid transformation are exposed, which include the high interfacial stresses from density difference and the thermal expansion mismatch, of extremely steep T gradients due to highly localized (~μm) laser heating, and of the preferential diffusion of certain elements in the case of incongruent crystallization.

Accurate measurement of glass transition temperature of Cu47.5Zr47.5Al5 and Zr41.2Ti13.8Cu12.5Ni10Be22.5 using step-scan modulated differential scanning calorimeter

The onset of the glass transition (Tgonset) and crystallization (Tx) temperatures of Cu47.5Zr47.5Al5 and Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vitreloy 1) plates were investigated using conventional differential scanning calorimeter (DSC) and step-scan modulated differential scanning calorimeter (MDSC). A large scatter of the Tgonset values with error of ±6.9 K for Cu47.5Zr47.5Al5 and ±8.0 K for Vitreloy 1 have been observed, at a heating rate of 20 K/min using conventional DSC. Such variation is linked with the variation of the enthalpy change of the respective metallic glass up to different extent prior to the glass transition. Our investigation shows that the Tgonset values can be accurately estimated from the reversible heat flow curve with an error of ±0.6 K using step-scan MDSC analysis, which eliminates the effect of enthalpy change near to the glass transition.

Effects of Cr2O3 and CaF2 on the structure, crystal growth behavior, and properties of augite-based glass ceramics

Glass ceramics were synthetized using Cr2O3 and CaF2 as additives, and their structure, crystal growth behavior, and physicochemical properties were investigated. The results showed that an excessive amount of Cr2O3 leads to the formation of a spinel structure in the glass matrix and an increase in the number of Q3Si units. The addition of CaF2 promoted the decomposition of Q2Si into Q1Si and Q3Si. Compared with the sample with Cr2O3 alone, the addition of CaF2 helped reduce the glass transition and crystallization temperatures, forming sharper crystallization peaks. Although CaF2 increased the activation energy of crystallization, it increased the degree of crystallinity and Avrami parameter (2.019). In terms of the microstructure, the sample added with CaF2 formed a snowflake-like structure with a spinel core. An excessive amount of spinel reduced the strength of the samples. The samples (1.5Cr2O3-3.5CaF2) exhibited a maximum flexural strength of 149.85 MPa and a good chemical resistance.

Promising high-conductivity Li1.5Al0.5Ge1.5(PO4)3 solid electrolytes: the effect of crystallization temperature on the microstructure and transport properties

High-conductivity NASICON-type solid electrolytes of Li1.5Al0.5Ge1.5(PO4)3 composition have been obtained through glass crystallization. Thermal behavior of the precursor glass has been investigated; glass transition and crystallization temperatures have been determined by DSC. The influence of glass crystallization temperature (750, 800, 820, and 850 °C) on the phase composition, microstructure, molecular structure, and ionic conductivity of Li1.5Al0.5Ge1.5(PO4)3 glass-ceramics has been studied. It was found that the optimum crystallization temperature for obtaining an electrolyte with the highest conductivity (0.39 mS cm−1 at 25 °C) is 820 °C.

One-step eco-friendly synthesized silver-graphene oxide/poly(vinyl alcohol) antibacterial nanocomposites

Due to the increasing occurrence and spread of antibiotic resistance pathogenic microorganisms, the development of antimicrobial materials has emerged as a strategy to control the bacterial activity and transmission. In this study, poly(vinyl alcohol)/silver nanoparticles-graphene oxide (PVA/AgNPs-GO) nanocomposites were synthesized by a one-step process with l-ascorbic acid as environmentally friendly reductant agent of a mixture of AgNO3, GO and PVA aqueous solutions. PVA/GO nanocomposites were also prepared for comparison. The structure, morphology, thermal, mechanical, water resistance and antibacterial properties of the samples were investigated as a function of GO and silver precursor contents. GO sheets decorated with spherical AgNPs were uniformly dispersed in the polymer matrix. The size range of most AgNPs was below 10 nm. Nanocomposites exhibited higher glass transition and crystallization temperatures. Thermal stability, mechanical and water resistance properties of PVA enhanced when GO was incorporated, and it was more remarkable in the presence of AgNPs-GO. PVA/AgNPs-GO nanocomposites showed antibacterial activity against Gram negative bacteria Escherichia coli and against Gram positive bacteria Staphylococcus aureus, being its efficiency dependent on exposure time and AgNPs precursor concentration. In contrast, PVA/GO films showed no activity against both bacteria over the GO loading range investigated. PVA/AgNPs-GO nanocomposites may be potential wound dressings.

Effect of annealing time on optical properties of CdS QDs containing glasses and their application for degradation of methyl orange dye

Borosilicate glass system (SiO2:B2O3:Na2O:ZnO) with the addition of 3 wt% CdS was prepared by conventional melt quench technique. Amorphous nature of glass sample was confirmed from XRD measurement. CdS QDs were grown in the glass matrix using an optimized heat treatment schedule in between glass transition (Tg) and crystallization (Tc) temperature. The phases of CdS QDs were noted by XRD and confirmed by HRTEM. Optical absorption study was carried out to measure the energy band gap and it is found that the energy band gap decreases with an increase in the size of QDs. Size determination was done by optical absorption spectra and match with HRTEM results. This change in the size of QDs was confirmed by PL spectra. The optimized glass sample was used for the degradation of methyl orange (MO) dye.

Effects of Al/Na and heat treatment on the structure and properties of glass ceramics from molten blast furnace slag

Abstract Glass ceramics with different Al/Na molar ratio from blast furnace slag were prepared using conventional melting-casting method. The structure and properties of glasses or glass ceramics were investigated by DSC, Raman, MAS NMR, XRD, and SEM. The DSC results indicated that the thermal stability (ΔT = Tc-Tg) and crystallization temperature (Tc) of the parent glass firstly increased and then decreased when Al/Na exceeded 1.21. The Raman and 27Al MAS NMR spectra analysis revealed that [AlO6] increased positively with Al2O3/Na2O. The calculation of Qn ([SiO4] units with bridging oxygen atoms number of n) suggested an obvious decline of (Q0+Q2)/(Q1+Q3) and that [SiO4] mainly existed in the form of Q1 when Al/Na exceeded 1.21, which accorded closely with Tc variation. The crystallization results determined by XRD showed that as Al/Na increased, the main crystal phase was transformed from akermanite to gehlenite and nepheline disappeared. Glass ceramics with Al/Na of 1.48 nucleated at 780 °C for 2 h and crystallized at 880 °C for 3 h exhibited the maximum value of flexural strength. Orthogonal experiment (L9(34)) were carried out to investigated the optimum heat treatment of glass ceramics with a Al/Na of 1.48. The analyses indicated that nucleation time variation has little influence on the flexural strength, and the optimum heat treatment was determined as 760 °C – 1 h–900 °C – 1 h and the flexural strength was characterized as 81.310 MPa.

Microstructure and mechanical properties of tempered glass joint bonded with Bi-B-Zn low melting glass

Soda lime tempered glass was successfully joined by a Bi-B-Zn lead-free low-melting glass with a composition of 35Bi2O3-50H3BO3-15ZnO (mol%). The Bi-B-Zn glass exhibited a glass transition temperature (Tg), softening point (Td) and crystallization temperature (Tc) of 346 ℃, 364 ℃and 448 ℃ respectively. The wettability of the glass on tempered glass substrate was investigated, and a contact angle of less than 13.94° was obtained when the temperature was raised to above 470 ℃ in open atmosphere. The microstructural evolution, interfacial bonding mechanism and mechanical properties of the joint at different joining temperatures were investigated. The diffusion bonding between Bi-B-Zn glass solder and tempered glass was achieved. The crystals of Bi4B2O9 were detected in the joint when the joining temperature was higher than 450 ℃. The shear strength and Vickers hardness of the joint reached 35.14 ± 1.89 MPa and 191.55 ± 13.93 MPa, respectively. The effects of the fractions and size of Bi4B2O9 on the shear strength were evaluated, and the fracture mechanism at the interface was also clarified.

Dy3+ doped tellurite glasses for solid-state lighting: An investigation through physical, thermal, structural and optical spectroscopy studies

In the present work, a series of Dy3+ ion doped tellurite glasses in the (50-x)TeO2-25WO3-25Li2O-xDy2O3 system were synthesized using conventional melt quenching technique to investigate colorimetric and radiative properties of Dy3+ ions in a new and stable host for their evaluation as solid-state lighting materials. Physical and structural properties were studied through density calculations, refractive index measurements, and Fourier-transform IR spectroscopy analysis. Thermal properties of glasses – glass transition (Tg) and crystallization (Tc/Tp) temperatures and temperature difference (ΔT) – were determined using differential scanning calorimetry. Optical absorption spectra of glasses were recorded with Vis-NIR spectrophotometer. CIE color coordinates, correlated color temperature, color rendering index and yellow to blue emission intensity ratio values were obtained through photoluminescence analysis. Radiative properties such as, radiative transition probability, stimulated emission cross-section, branching ratio and optical bandwidth gain were calculated according to Judd-Ofelt theory. The obtained optical spectroscopy results were found to be comparable or better than other reported glass systems. From the derived results, glasses with Dy3+ ion concentration lower than 0.5 mol% were found to show the closest CIE color coordinate values to pure white light and highest CCT and CRI values revealing good potentiality to be used for applications in white LEDs and solid-state lasers.

Characterization of 20Na2O·30((1−x)CaO·xSrO)·50P2O5 glasses for a resorbable optical fiber application

AbstractResorbable glasses with nominal molar compositions of 20Na2O·30[(1−x)CaO·xSrO]∙50P2O5, where x = 0, 0.25, 0.50, 0.75, and 1, were prepared and characterized. With the replacement of CaO by SrO, the molar volume, refractive index, and coefficient of thermal expansion increased, and the glass transition temperature, crystallization temperature, and viscosity decreased. The replacement of CaO by SrO decreased the dissolution rate in 37°C water by nearly an order of magnitude. Resorbable glass fibers drawn from melts of the 20Na2O·30CaO·50P2O5 glass exhibited decreasing transmission of laser light (632 nm) in a predictable way as the fiber dissolved in a phosphate buffer solution. This demonstrated that these glasses could be used to produce resorbable fibers for temporary biosensing or therapeutic applications.

Thermal, structural and electrical study of boron-incorporated LATP glasses and glass-ceramics

Glasses of three compositions were prepared in the Li2O–Al2O3–B2O3–TiO2–P2O5 system. Next, they were heat-treated at 900 °C for 2 h to yield fast Li+ ion conducting glass-ceramics of NASICON-like structure. Effects of boron additive on structural, thermal and electrical properties of glasses and glass-ceramics are herein investigated and discussed. Thermal analysis revealed that glass transition and crystallization temperatures shift towards lower values with increasing boron content. Moreover, the system under study exhibits improved glass-forming ability. X-ray diffraction studies show that B-incorporated glass-ceramics are mainly composed of rhombohedral R3̄c phase with unit cell parameters a and c decreasing with boron substitution. Raman peaks at 791 cm−1 and 1206 cm−1 in glasses with B2O3 addition confirm the presence of BO4 and BO3 units in the glass structure. Overall ion transport properties (total conductivity and activation energy) were characterized by means of impedance spectroscopy. For optimized composition, the highest total conductivity of 6 · 10−5 S/cm for B-incorporated glass-ceramics was recorded. Moreover, separation of the bulk and grain boundary electrical responses was performed on the basis of equivalent circuit modelling of impedance data.

Influence of Er3+ ions addition on thermal and optical properties of phosphate–germanate system

Zinc phosphate–germanate samples doped with Er3+ ions and co-doped with silver nanoparticles in the 59.7KPO3–0.3Ag(NPs)–20ZnO–(20 − x)GeO2–xEr2O3 system where x ≤ 5 mol% were prepared by melting–quenching technique. The mentioned system was studied by X-ray diffraction (XRD), differential thermal analysis (DTA) and ultraviolet–visible (UV–Vis) spectroscopy, too. XRD analysis shows the presence of amorphous state for low contents of erbium and the presence of the ErPO4 (tetragonal, body-centered lattice) crystalline phase beside the amorphous phase for high contents of erbium (x ≥ 3 mol%). DTA investigation permitted the identification of some thermal parameters such as glass transition temperature, crystallization temperature and melting temperature. From these data, other two important parameters were calculated: the fragility index and the activation energy of glass transition. In our case, the obtained data reveal a good thermal stability for the matrix of the studied system. The increase in the content of erbium ions leads to more fragile glasses and glass ceramic samples. The DTA results also show that the samples are obtained from KS liquids. The UV–Vis spectroscopy shows seven f–f electronic transitions for the studied system, due to the presence of erbium ions. From the obtained UV–Vis data, the bonding parameter that shows an ionic character of the bonds from the glass ceramic network was calculated. Also, the values of optical band gap energy ( $$E_{\text{g}}^{\text{opt}}$$ ) show that when the erbium ions content increases, the $$E_{\text{g}}^{\text{opt}}$$ values decrease due probably to the amount of non-bridging oxygen atoms from the network.

Phase Transformation in Se75Te13In12 Chalcogenide Thin Films

In the present research work Se75Te13In12 chalcogenide glass has been prepared by melt quenching technique. The non-isothermal Differential Scanning Calorimetry (DSC) measurement of synthesized alloy has been executed at constant heating rate of 25 K/min. The glass transition temperature (Tg), crystallization temperature (Tc) and melting temperature (Tm) are found to be 349, 376 and 533 K, respectively. Thin films of 400 nm thickness of Se75Te13In12 alloy were prepared by thermal evaporation technique. To study the phase transformation, the thermal annealing was done at two different temperatures 353 and 363 K for 2 h in a vacuum furnace under a vacuum of 10–3 Torr. Optical measurements were done for as-prepared and annealed films. The optical band gap is found to decrease with increasing annealing temperature. The transformed phases of as grown and thermally annealed films were analyzed by High Resolution X-ray diffraction (HRXRD) and Field Emission Scanning Electron Microscope (FESEM).

Influence of pyrrole feeding ratios on physicochemical characteristics of high-performance multilayered PPy/PVC/PDA@FG-NH2nanocomposites

Nanocomposites of conjugated polymers polypyrrole (PPy) and polyvinyl chloride (PVC) as matrices and 1,4-phenylenediamine (PDA) as a linker with amine functional graphite (FG-NH2) as filler have been efficiently fabricated using in situ oxidative polymerization, and the effect of various mass ratios on physicochemical characteristics of prepared nanocomposite was investigated. The layer-by-layer oxidative polymerization of various matrices on host filler surface is confirmed by Fourier transform infrared, energy dispersive X-ray, and X-ray photoelectron spectroscopy examinations. Field emission scanning electron microscopy revealed fibrillary morphology of obtained nanocomposites. Thermal stability, glass transition temperature, and melting and crystallization temperature of the nanocomposites were increased with the incorporation of modified graphite. Brunauer–Emmett–Teller analysis explored the improved adsorption capacity (128 cm3g−1) of the nanocomposite with higher feeding ratio of pyrrole. The influence of FG-NH2and pyrrole on electrical conductivity performance of composites was also investigated. Functionalized graphite in the resultant PPy/PVC/PDA@FG-NH2nanocomposites played an important role in forming conducting network in PPy matrix indicating synergistic effect between PPy and FG-NH2.

Modeling and experimental determination of physical properties of GexGaySe1-x-y chalcogenide glasses II: Optical and thermal properties

This study systematically analyzed the correlation between topological structure and chemical ordering on the optical and thermal properties of synthesized material in the glass forming region of the GexGaySe1-x-y ternary. A series of ten compositions from 5 to 30 mol% Ge and 5 to 15 mol% Ga were examined within the ternary, showing broadband infrared properties with transmission from 1 to 25 μm. Topological constraint theory applied to compositions examined exhibited sharp inflection at the average coordination number of <r> = 2.67 defined as the chemical threshold where the glass network consists of tetrahedral Ge(Ga)Se2 units. These observations indicate that thermal and optical properties in these chalcogenide glasses are highly sensitive to the chemical ratio of homopolar versus heteropolar bonds, Ge to Ga ratio, as well as the dimensionality of the topological structure. Glass transition and crystallization temperature values compare well with previous literature on similar GeXSe systems. This is a comprehensive study that systematically examined thermal conductivity, heat capacity, absorption coefficient, and refractive index within the GexGaySe1-x-y system, correlating these properties with structural network calculations. The presented methodology and findings will enable the compositional design of materials for infrared systems using GexGaySe1-x-y glasses with broadband transmission.

Effect of Mischmetal Addition on Physical and Mechanical Properties of Al–Ni–Zr Melt-Spun Ribbons

In this work, the effect of mischmetal addition on the microstructural, physical and mechanical properties of rapidly solidified (Al90Ni8Zr2)(100−x)MMx (x = 0–6) alloys has been studied. In this respect, various as-spun ribbons were prepared by the single-roller melt-spinning process at a quenching wheel speed of 43 m/s. The results obtained showed that mischmetal had a strong effect on the control of amorphicity of the alloy during melt-spinning process. TEM and XRD results revealed the presence of two phases, nanocrystalline α-Al and amorphous phase of Al90Ni8Zr2 alloy compared with those of MM-added samples with an amorphous structure. This is believed to be related to the increase in glass-forming ability due to the addition of mischmetals to the alloy. The average crystallite size obtained for MM-free sample was in the range of 30 nm as confirmed by XRD and TEM data. Phase separation and formation of second phase were observed for 6 at.% MM-added sample in the as-spun state. DSC results revealed that glass transition and crystallization temperatures increased with the increase in mischmetal in Al90Ni8Zr2 system. Further, it was seen that the maximum microhardness value was obtained for the 4 at.% MM-added samples (4.72 GPa).