Glass Melting Research Articles

Characterization of the α-relaxation and gel-like dynamics in mixed network forming (GeO2)x(NaPO3)100-x glass melts by photon correlation spectroscopy

Dynamic light scattering investigations of the α-relaxation in network-forming (GeO2)x(NaPO3)100-x glass melts is reported for x = 0 to 40 mol% GeO2. Addition of GeO2 results in an increased density of bridging oxygen bonds. This monotonically increases the glass transition temperature but generates complex changes to the glass forming fragility which initially decreases with increasing GeO2 but increases again at higher GeO2 contents. A resolution to this odd fragility behavior is obtained by applying a coarse-graining procedure used previously in sodium germanate melts to arrive at a topological network connectivity for which fragility exhibits a universal dependence. Also observed in the light scattering measurements is a secondary relaxation, several orders of magnitude slower than that of the α-relaxation, which we tentatively attribute to gel-like anomalous diffusion of Ge crosslinks formed between phosphate chains.

Submicroscopic magnetite may be ubiquitous in the lunar regolith of the high-Ti region

Magnetite is rare on the Moon. The ubiquitous presence of magnetite in lunar soil has been hypothesized in previous Apollo Mössbauer spectroscopy and electron spin resonance studies, but there is currently no mineralogical evidence to prove it. Here, we report a large number of submicroscopic magnetite particles embedded within iron-sulfide on the surface of Chang’e-5 glass, with a close positive correlation between magnetite content and the TiO 2 content of the surrounding glass. The morphology and mineralogy of the iron-sulfide grains suggest that these magnetite particles formed via an impact process between iron-sulfide droplets and silicate glass melt, and ilmenite is necessary for magnetite formation. Magnetite in lunar glass is a potential candidate for the “magnetite-like” phase detected in the Apollo era and suggests that impact-induced submicroscopic magnetite may be ubiquitous in high-Ti regions of the Moon. Moreover, these impact-induced magnetite particles may be crucial for understanding the lunar magnetic anomalies and mineral components of the deep Moon.

Cold crystallization behavior of poly(lactic acid) induced by poly(ethylene glycol)-grafted graphene oxide: Crystallization kinetics and polymorphism

Cold crystallization between the glass transition and melt temperature is of particular significance for crystalline regulation due to the slow crystallization rate of poly(lactic acid) (PLA). Incorporation of nucleation agents can promote PLA crystallization by reducing the nucleation activation energy and offering nucleation sites. Herein, we investigated the cold crystallization behavior of PLA induced by poly(ethylene glycol)-grafted graphene oxide (PEGgGO) which was synthesized and identified as a powerful nucleation agent for melt crystallization. The obtained results showed that PEGgGO not only accelerated the cold crystallization kinetics of PLA, but also promoted the polymorphic transition kinetics during the heating process. The half crystallization time of PLA induced by PEGgGO was shortened by 51 % and the final crystallinity increased by 57 % compared to that induced by GO alone at the same loading of 0.5 wt%. In addition, relative to GO, PEGgGO enabled the α′-to-α phase transition kinetics of PLA by a reduced transition temperature range of 26 % due to its excellent nucleation ability even at cold crystallization. The flexible PEG chains on GO facilitated crystalline regulation of PLA owing to the improved chain mobility. This work provides a broader framework for fashioning semicrystalline PLA products with enhanced crystallinity and refined crystal structure towards prospective applications.

Effect of High Fiber Content on Properties and Performance of CFRTP Composites

Continuously reinforced thermoplastic composites are widely used in structural applications due to their toughness, light weight, and shorter process cycle. Moreover, they provide flexibility in design and material selection. Unlike thermoset composites, continuous fiber content to maximize mechanical properties in thermoplastic composites has not been well investigated. In this paper, three thermoplastic systems are investigated to study the optimum content of continuous fiber reinforcement. These systems include carbon fiber/polyphenylene sulfide (PPS), glass fiber/PPS, and glass fiber/high-density polyethylene (HDPE). Tapes were made at several fiber contents, and samples were compression molded and tested using thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), tensile, 3-point flexure, and short-beam shear tests. Results revealed that higher fiber content led to an increase in the glass transition and melt transition temperatures of the polymer. Some mechanical properties increased with fiber content and then began to decrease upon further addition of fibers, while other properties, such as ductility and interfacial bond strength, decreased with more reinforcement. Furthermore, the optimum fiber contents to maximize mechanical properties are different for different properties and different materials.

Sustainable construction materials from alkali-activated waste fiberglass and waste refractory

In this work, waste fiberglass was up-cycled, alone, or mixed with used alumina-zirconia-silica (AZS) refractory from dismantled glass melting furnaces. Alkali activation was performed by suspending fiberglass and fiberglass/AZS powders in NaOH aqueous solution of various concentrations (8M, 6M, and 3M). The activation of waste fiberglass with 8M NaOH yields a gel with calcium and sodium-containing aluminosilicate hydrates. The addition of AZS refractory enabled the release of aluminates into the solution, which had beneficial effects on the mechanical properties. Low molarity activation yielded weaker materials which could be used as precursors for firing at moderate temperatures (800 °C and 1000 °C) to create cellular glass-ceramics, with a total porosity of up to 92 %. The firing of 8M activated samples resulted in glass ceramics with a 66–75 % porosity range and compressive strength of 10–23Mpa. The compressive strength-to-density ratio before and after firing was comparable to that of established commercial construction materials.

On the suitability of the α‐relaxation as novel trigger for a shape memory polymer

AbstractShape memory polymers typically utilize the glass transition or melting temperature to switch from one shape to another. The goal of this work is to check if the α‐relaxation, which is attributed to the migration of chains through lamellar crystals, can be utilized as novel switch for any crosslinkable semi‐crystalline thermoplastic. Using cross‐linked low‐density polyethylene (x‐LDPE) as an example, it is shown that the α‐relaxation is indeed suitable as switch, when the polymer is crystallized under strain to an intermediate shape. It is demonstrated that post‐stretching at a temperature between the α‐relaxation and the melting temperature, followed by subsequent cooling to room‐temperature switches x‐LDPE from the intermediate to a temporary shape and that reheating to this temperature initiates the retraction back to the intermediate shape. Switching between intermediate and temporary shapes is shown to be accompanied by a reversible change in morphology.

Study of Some Physical and Antibacterial Properties of Bio-based (PLA)/(PCL) Blend reinforced with ZrO2 Nanoparticles

The aim of this study was to produce flexible films by combining polylactic acid (PLA) and poly(ε-caprolactone) (PCL), and enhance their strength by reinforcing them with different weight percentages (0.75, 1.5, and 2.25%) of zirconium oxide (ZrO2) nanoparticles (NPs) using a solvent casting process. The physical and antibacterial properties of the films were analysed to determine their suitability for use in food packaging. X-ray diffraction (XRD) patterns of the PLA/PCL films containing 2.25% by weight ZrO2 nanoparticles have a peak at an angle of 2θ = 17.18°, accompanied by smaller peaks. This confirms that these thin films have a semi-crystalline structure and that the molecules in the thin films are well dispersed. Scanning electron microscopy (SEM) analysis of the film surfaces reveals that the pure PLA/PCL films exhibit a smooth surface, while the (PLA/PCL/ZrO2NPs) films have a rough surface. The thermal behaviour of the blends through differential scanning calorimetry (DSC) showed fluctuations due to variations in the reinforcement ratio, resulting in changes in the glass transition and melting temperatures. These oscillations indicate changes in the level of crystallinity. ZnO2 has antibacterial properties that promote growth inhibition, making these films more effective in food packaging.

Influence of cerium addition and redox state on silicate structure and viscosity

AbstractThe viscosities of Ce‐free and Ce‐bearing (∼1.3 mol%, ∼6.5 wt.% Ce2O3) soda lime silicate (window glass) melts were measured with respect to oxidation state. Experiments were performed isothermally using a concentric‐cylinder viscometer on melts equilibrated with successively reducing CO–CO2 gas mixtures within a gas tight vertical tube furnace at 1 atm. Viscosity measurement and sampling were performed at the end of each melt reduction step. Further, viscosities in the glass transition temperature range were estimated using the shift factor method applied to glass transition temperature values determined using differential scanning calorimetry (DSC) measurements on quenched glasses. The Ce speciation at each stepwise melt reduction was probed using Ce L3‐edge X‐ray absorption near‐edge structure (XANES) spectroscopy, while structural information upon Ce addition and reduction was provided by Raman spectroscopy. The viscosities of these materials remain constant at this level of Ce addition and do not vary significantly with redox state at high temperature. Conversely, viscosity values in the glass transition temperature range increase upon both Ce addition and reduction. Our analysis, based on the glass composition analyses obtained via electron probe microanalyzer (EPMA), viscosity calculations, and observations of silicate structural changes, leads to the conclusion that the observed viscosity increase around the glass transition temperature is explained by the high ionic field strength of Ce ions as well as the polymerization behavior of the silicate matrix occurring during reduction of Ce. Because of its low concentration, resulting from its low solubility, Ce redox changes exert only minimal effects on the viscosity of this melt.

Optical Real-Time Castability Evaluation for High-Throughput Glass Melting

A novel optical real-time method for evaluating the castability of glass forming melts for laboratory furnaces is presented. The method is based on the analysis of top view images of the melt surface inside the crucible during melting after being subjected to a small mechanical impulse. In this way, the melt surface is excited to oscillate. The difference in contrast between two images taken in quick succession scales with the viscosity, with a larger diffe­rence occurring at lower viscosities. The method is designed as an instrument for the in-line evaluation of the castability for a high-throughput glass melting system as part of the joint project “GlasDigital” in the framework of the German Platform Material Digital initiative but is applicable to other laboratory furnaces as well.

French nuclear glass synthesis: Focus on liquid waste dissolution kinetics

In France, high-level nuclear wastes are confined in glass using a calcination-vitrification process. The waste can also be vitrified by liquid feeding, which imply to add directly the liquid waste. In this study, we focus on nuclear waste vitrification process by direct liquid feeding in order to decipher the dissolution kinetics of the waste in the molten glass. We propose an experimental and analytical protocol to study the dissolution in the solid glass frit of the liquid waste dried beforehand during the glass melting process. This methodology allows to: i) identify the intermediate reaction phases which formed and dissolved during the process; ii) characterizes the evolution of waste element concentrations in the dried waste as a function of time and temperature on glass obtained after cooling; iii) define kinetic parameters relative to the process of intermediate reaction phases dissolution in the molten glass. The three main intermediate reaction phases formed and dissolved in function of temperature are Ca-REE (Rare Earth Elements)- silicate, Ce- oxide and Zr- oxide. At each temperature step (800 to 1200 °C) the evolution of REE (La, Ce, Nd and Pr) and Zr concentrations in the glass samples obtained after cooling shows a fast increase followed by a stabilization in time, which reflects the fast dissolution of the dried waste in the molten glass, i.e. the fast dissolution of intermediate reaction phases. The molten glass is completely homogeneous at classical synthesis temperature (1200 °C). A parameterization methodology of element concentration evolution as a function of time and temperature is proposed here in order to define the kinetic parameters corresponding to the dried waste dissolution (i.e. concentration at a given time t, maximal concentration at a given temperature, characteristic time and activation energy). The results show that the activation related to the formation and dissolution processes of the intermediate reaction phases, i.e. whether they constitute intermediate compounds formed in temperature by the interaction between the dried waste and the glass frit, and the phases formed without reacting with the glass frit, directly in the dried waste during heat treatment.

Phase behaviour and heat capacities of DBN and DBU based protic ionic liquids – Insights into the ionic character and nanostructuration

Herein, we report the thermal behavior and high-precision heat capacity values, at T = 298.15 K, and in the range from 283 to 363 K, for several protic ionic liquids (PILs), derived from the 1:1 liquid mixtures of the organic superbases 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) with some carboxylic acids (propionic, butyric, hexanoic and octanoic). Glass transition, Tg, crystallization, Tc, cold-crystallization, Tcc, and melting, Tm, temperatures were determined for the PILs studied, showing marked differences with the base – Tg is lower for all DBN PILs, and no Tm, Tc, and Tcc could be obtained for the DBU PILs. The standard molar heat capacities, Cp,m0, were obtained with an uncertainty of less than ±0.3 % and their dependence on the base and on the acid’s chain length was studied in detail. The Cp,m0 of the DBU PILs were found to be significantly higher than those of the corresponding DBN PILs, which corroborates the greater ionic character of DBU PILs. The heat capacity data suggested the existence of a trend-shift with the chain length of the carboxylic acid. Similar to aprotic ionic liquids, the shift occurs around n = 5 (pentanoic acid) and suggests the existence of some degree of nanostructuration into polar and non-polar domains in PILs with larger acids. Moreover, PILs can display abnormally high excess heat capacities, resulting from the formation of an ionic mixture from neutral species. Analysis of the calculated excess heat capacities indicates that PILs tend to become less ionic as the temperature increases, which goes in accordance with the acid-base equilibrium shift.

Microwave spheronization of polyetherimide powder in plasticizer liquids for laser powder bed fusion

Preparing spherical powders from high-performance engineering plastics is usually challenging due to their high characteristic temperatures and excellent chemical resistance. This study reported an innovative liquid-phase microwave heating method for rapid spheronization of amorphous polyetherimide (PEI) powder and explored the processability of resultant powder in laser powder bed fusion (PBF-LB). The results indicated that the microwave process conditions, including the type of plasticizer liquids and microwave time, significantly influenced the spheronization effect and physicochemical properties of the powder. The plasticizing effect of the liquid largely reduced the glass transition temperature and melt viscosity of PEI particles, promoting their spheronization process. Spheronization enhanced the PBF-LB processability of PEI powder and reduced structural defects in parts, thereby leading to improved mechanical properties. Furthermore, its valuable flame-retardant properties were largely preserved. These findings showed the power of microwave spheronization in plasticizer liquids for advancing the application of optimized high-performance engineering plastic powders in the field of PBF-LB.

Influence of Carbonyl Iron Particles (CIP) and Glass Microspheres on Thermal Properties of Poly(lactic acid) (PLA).

In this investigation, composite poly(lactic acid) (PLA) systems of hollow glass microspheres (MS) and carbonyl iron particles (CIP) were processed and characterized to investigate the effects of using conductive and insulating particles as additives in a polymer system. PLA-MS and PLA-CIP were set at the two levels of 3.94 and 7.77 vol.% for each particle type to study the effects of the particle material type and loading on neat PLA's thermal properties. It was observed during the twin-screw extrusion that the addition of CIP greatly decreased the viscosity of the PLA melt during processing. Correlations determined using thermogravimetric analysis, differential scanning calorimetry, thermal conductivity, and shear rheology provided insights into how thermal stability was affected. The incorporation of MS and CIP altered thermal properties such as the glass transition temperature (Tg), melting temperature (Tm), and cold crystallization temperature (Tcc). The metal CIP-filled systems had large increases in their thermal conductivity values and viscoelastic transitions compared to those with PLA that were correlated with the observed overheating during extrusion.

Demethylation strategies for spiro-OMeTAD to enhance the thermo-opto-electronic properties as potential hole transport materials in perovskite solar cells

Abstract Spiro-OMeTAD is a widely used hole-transporting material (HTM) that plays a crucial role in achieving highly efficient perovskite solar cells (PSCs). In this work, a series of demethylated functionalized spiro-OMeTAD-based derivatives with different numbers of hydroxyl substituted groups (named as SOH2, SOH4, and SOH6) were synthesized, and their thermal, optical, electrical, and electrochemical properties have been investigated as potential HTMs for PSCs. It has been found that the molecule with six hydroxyl substituted groups on the spiro-OMeTAD-based structure SOH6 exhibited the highest glass transition temperature (T g) and melting point (T m) as compared to SOH2 and SOH4 molecules. The UV–vis absorption spectra portrayed a distinct pattern with the increase in hydroxyl substituted groups as it was slightly blue-shifted for the SOH6 molecule compared to red-shifted for SOH2 and SOH4 molecules. Carrier mobility shows a notable improvement with the hydroxyl substitution. The density functional theory (DFT) has provided useful insight into identifying the chemical stability of spiro-OMeTAD derivatives. In the device simulation, hydroxyl-substituted spiro SOH2 was found to outperform its pristine counterpart, achieving a peak PCE of 17.61% with a V oc of 0.98 V, a J sc of 22.69 mA cm−2, and an FF of 80.67% within the device structure FTO/TiO2/MAPbI3/HTMs/Au. This investigation provided insight into the development of novel spiro-OMeTAD-based derivatives with enhanced optoelectronic properties and showed promising potential for addressing the limitations of traditional HTMs in PSCs.

Ultramafic melt viscosity: A model

A non-Arrhenian model for the Newtonian viscosity (η) of ultramafic melts is presented. The model predicts the viscosity of ultramafic melts as a function of temperature (T), pressure (P), H2O content and for a range of melt compositions (70 < Mg# < 100). The calibration consists of 63 viscosity measurements at ambient pressure for 20 individual melt compositions and 5 high-P measurements on a single melt composition, all drawn from the literature. The data span 14 orders of magnitude of η (10−2 to 1011.8 Pa s), a T range of 880 to 2700 K, pressures from 1 atm to 25 GPa, and include measurements on hydrous melts containing 0.2 to 4.4 wt.% H2O. The T-dependence of viscosity is modelled with the VFT equation [log η = A+B/(T(K) − C)] whereby A is assumed to be a common, high-T limit for these melt compositions (i.e. log η∞ = -5.4). The pressure and composition effects are parameterised in terms of 5 adjustable parameters in expanded forms of B and C. The viscosity model is continuous across T-P-composition space and can predict ancillary transport properties including glass transition temperatures (Tg) and melt fragility (m). Melt viscosity decreases markedly with increasing H2O content but increases significantly with increasing pressure and decreasing Mg# (i.e. higher Fe-content). We show strong systematic decreases in Tg and m with increasing H2O content whereas an increase in P causes a rise in Tg and decrease in m. The predictive capacity of this model for ultramafic melt viscosity makes it pertinent to the fields of volcanology, geophysics, petrology, and the material sciences. Moreover, it provides constraints on models of magma oceans on terrestrial planets and, the evolution of planetary atmospheres via magmatic degassing on exoplanets.

Shallow storage of the explosive Earthquake Flat Pyroclastics magma body, Okataina Volcanic Center, Taupo Volcanic Zone, New Zealand: evidence from phase-equilibria experiments

Rhyolitic tuffs range widely in their crystal contents from nearly aphyric to crystal-rich, and their crystal cargoes inform concepts of upper crustal magma reservoirs. The Earthquake Flat pyroclastics (Okataina Volcanic Center, Taupo Volcanic Zone, New Zealand) are 10 km3 of rhyolitic tuffs with abundant (~ 40 vol.%) plagioclase and quartz, minor biotite, hornblende, and orthopyroxene, and accessory Fe-Ti oxides, apatite, and zircon, set in high-silica rhyolitic glass. Major minerals form large, euhedral phenocrysts and abundant glomerocrysts with few disequilibrium textures excepting some faintly resorbed quartz. Plagioclase phenocrysts have thick rims of nearly constant composition near An30, and hornblende is weakly zoned or unzoned. The abundant and texturally complex mineral assemblage contrasts with the nearby (~ 25 km), nearly synchronous, but more voluminous and crystal-moderate rhyolite tuffs from Rotoiti caldera. New H2O-saturated phase-equilibria results on the erupted Earthquake Flat melt (glass) determine its co-saturation with the partial phenocryst assemblage of plagioclase, quartz, biotite, and Fe-Ti oxides at: 140 MPa, 755 ºC. These closely approximate the conditions of the pre-eruptive magma body assuming it was saturated with nearly pure H2O and at an fO2 of ~ Ni–NiO. Absence of hornblende and orthopyroxene from the synthesized assemblages may result from those minerals being in a peritectic reaction relation with melt to produce biotite, so they would not grow from the liquid used as starting material. Experimental results on Rotoiti rhyolite (Nicholls et al. 1992) show that the two bodies resided at similar pressures, temperatures, and fO2s. Lower crystal abundance of the Rotoiti tuffs may result from slight compositional differences. We interpret that the Earthquake Flat pyroclastics were sourced from the crystal-rich periphery of a mushy reservoir system with the Rotoiti occupying a more melt-rich central location. Uncertain is whether this was a single intrusion zoned continuously in crystallinity, or discrete adjacent intrusions, but our results illustrate and quantify complexities of magma storage across relatively short distances.

Poly(Butylene Succinate) Copolyesters Modified with Linear‐Chain Diols toward Adjustable Thermal, Mechanical, and Biodegradable Properties

AbstractThe production and application of poly(butylene succinate) (PBS) still face challenges such as high production costs, insufficient toughness, and slow biodegradation. This study utilizes the ring‐opening condensation polymerization method to prepare PBS copolyesters using succinic anhydride (SAA) and 1,4‐butanediol (BDO) as raw materials, with 20 moL% different lengths of linear‐chain diols as third monomers (carbon numbers are 3, 5, 6, 8, 9,10, and 12). Both PBS and its copolyesters exhibit high weight average molecular weights (18.8 × 104–26.1 × 104 g moL−1), much higher than those obtained through the traditional conventional direct esterification method. Incorporating the third monomer reduces the glass transition temperature (Tg), crystallinity, and melting point (Tm) of the copolyesters. As the chain length of the third monomer increases, the copolyesters show improved toughness, with the elongation at break and notch impact strength of poly(butylene succinate‐ran‐dodecylene succinate) (P(BS‐ran‐DoS)) increasing from 374.1% and 5.6 KJ m−2 of PBS to 723.2% and 64.8 KJ m−2, respectively. The degradation rate of the copolyesters modified with short‐chain diols increases significantly, and as the chain length of the third monomer increases, the degradation rate of the copolyesters slows down. Therefore, the selection of the third monomer can be used to adjust the properties of the polymer.

Temperature and composition dependence modeling of viscosity and electrical conductivity of low-activity waste glass melts

The development of models that accurately relate the properties of a glass melt to its temperature and composition is important for glass formulation, melter control, and modeling the melt flow, refractory corrosion, and production rate. Using a database consisting of more than 4,000 data points measured between 900 °C and 1250 °C for over 600 unique low-activity waste glass compositions, we developed models for the melt viscosity and electrical conductivity. Models based on the Gaussian process regression approach outperformed models based on the Vogel–Fulcher–Tammann equation according to four standard metrics and yielded reliable prediction intervals. The models found primarily linear effects between properties and individual components, except for the effect of the Na2O mass fraction on the electrical conductivity. The effects were found to be consistent with current theories on physical processes involved with those properties.

Poisson's Ratio Prediction of Injection Molded Thermoplastics Using Differential Scanning Calorimetry.

In the development of thermoplastic products, it is necessary to conduct the necessary mechanical tests and evaluate the reliability of thermoplastics in each case, because the mechanical properties of the same material vary depending on the molding process conditions and product shape. In order to build a sustainable society, it is expected that the evaluation of the mechanical properties of thermoplastics, which are resource and energy saving, will be required. In this paper, the glass transition temperature and melting point of injection-molded thermoplastics were evaluated by differential scanning calorimetry, and the correlation between Poisson's ratio and free volume was obtained by applying the theory proposed by Flory et al. A certain correlation was found between the Poisson's ratio of polymers and the change in free volume determined by the glass transition temperature. It is also clear that this relationship can be approximated by orders of magnitude. The Poisson's ratio of the core layer tended to be smaller than that of the skin layer. It has also been found that there is a negative correlation between the Young's modulus and the free volume of the polymer material.

Thermal and rheological properties and processability of thermoplastic lignocellulose

AbstractFossil‐free biobased materials like thermoplastic lignocellulose are gaining attention because of climate issues. However, there is a challenge to make these as thermoplastic as commonly used thermoplastics. Arboform® is one of today's commercially available thermoplastic lignocellulose materials. In this work, the processability of this material was studied in detail and the effects of plasticizers on its processability, rheological, and mechanical properties were determined. Thermal/calorimetry analysis indicated that the processing temperature window was shifted to lower temperature with the use of tributyl citrate (TBC) and poly(ethylene glycol) (PEG 400) plasticizers, thus enabling extrusion at lower temperature. TBC and PEG 400 decreased both the glass transition temperature and melting point of the polylactide component. Surprisingly, they also affected the lignin component, as observed by the decreasing lignin decomposition temperature. It is observed that TBC and PEG400 lowered the stiffness of the compression molded material in the temperature range investigated (−30–180°C), and tensile tests in the presence of TBC revealed a decrease in ductility. Notable is that, in contrast to most thermoplastics, the Arboform® melt increases in viscosity and elastic moduli when the processing temperature was increased (from 180 to 200°C) or when processing time was increased.