Melting Conditions Research Articles

Iron(ii) carboxylates and simple carboxamides: an inexpensive and modular catalyst system for the synthesis of PLLA and PLLA-PCL block copolymers.

The combination of inexpensive Fe(ii) acetate with low molecular weight aliphatic carboxamides in situ generates an effective catalyst system for the ring opening polymerisation of lactones. PLLAs were produced in melt conditions with molar masses of up to 15 kg mol-1, narrow dispersity (Đ = 1.03), and without racemisation. The catalytic system was investigated in detail with regard to Fe(ii) source, and steric and electronic effects of the amide's substituents. Furthermore, the synthesis of PLLA-PCL block copolymers of very low randomness was achieved. This commercially available, inexpensive, modular, and user-friendly catalyst mixture may be suitable for polymers with biomedical applications.

A melt inclusion approach to reconstructing sulfur contents and sulfide saturation of primitive basaltic melts

The study of melt inclusions in minerals is the only direct approach to estimate the contents of volatile components in silicate melts, which are essential to constrain the processes of magma generation and evolution. In particular, the content of sulfur in silicate melts is closely connected with the P-T-fO2 conditions of mantle melting and the formation of sulfide deposits. Inclusions in high-Mg olivine can provide access to the composition of the most primitive melts, but these are the most susceptible to post-entrapment modification such as ‘Fe-loss’. The loss of Fe consequently decreases sulfur solubility and leads to silicate-sulfide immiscibility and formation of daughter sulfide globules, significantly affecting the initial proportions of S contained within the silicate part (glass) of melt inclusions. In this study, we investigated the budget of sulfur in heated and quenched melt inclusions hosted in primitive olivine (87–90 mol% Fo) by accounting for sulfur stored in silicate glass (melt), daughter sulfide globules and shrinkage bubbles. Melt inclusions from MORB-like olivine-phyric rocks (Kamchatsky Mys, Far East Russia) heated for 30 min at 1200 °C and 1300 °C were compared with similar experiments on olivine-hosted melt inclusions over a 5 min duration (at 1200 °C and 1350 °C). Sulfur contents were calculated in the following types of melt inclusions, containing: (i) both sulfide globules and shrinkage bubbles, (ii) only sulfide globules, (iii) only shrinkage bubbles, and (iv) completely homogenized. Our findings indicate that S content in shrinkage bubbles and its precipitates is negligible in reheated water-poor melt inclusions, whereas daughter sulfide globules are significant repositories of initial S. Therefore, when estimating initial S contents in parental melts, the amounts stored in both daughter sulfide and silicate glass should be considered. Our experiments with MORB-type melt inclusions in forsteritic olivine phenocrysts demonstrate that effective homogenization is best achieved by briefly overheating melt inclusions prior to rapid quenching. Although this technique does not allow for the MgFe equilibrium between melt inclusions and their host olivine to be fully achieved, it promotes the dissolution of daughter sulfide globules and shrinkage bubbles, and thus the release of initial sulfur back to the melt/glass.

Modeling the Fluid Flow for Recent Solidification Experiments in Microgravity Electromagnetic Levitation

Microgravity electromagnetic levitation provides a unique processing environment for solidification experiments. The contactless processing allows for greater access to the undercooled region of the melt by isolating the sample from its environment and reducing the available heterogeneous nucleation to consistently achieve deep undercoolings. In the ISS-EML, a variety of solidification studies have investigated the relationship between nucleation temperature and flow conditions in metallic melts. These studies include recent work by Kelton et al. in which the coupled flux nucleation model was used to explore solidification in supercooled liquids using glass forming alloys: Vit106, Cu50Zr50, and Ti39.5Zr39.5Ni21. The relationship between fluid flow and nucleation is also a critical factor in recent experiments investigating dynamic nucleation. Unexplained solidification events occurred during both Spacelab Missions IML-2, MSL-1R, and ISS-EML. These experiments encompassed both steady and transient, accelerating flows. Repeatable, anomalous solidification was observed in both flow conditions. The conditions are consistent with dynamic nucleation, which relies heavily on the flow conditions within the sample for nucleation to occur. During these experiments, flow is not directly observable; however, magnetohydrodynamic models allow the flow to be calculated using the properties of the melt and the experimental conditions. These models provide key insights into the flow conditions and the impacts of flow on nucleation in these experiments.

Melting heat transfer and thermal radiation effects on MHD tangent hyperbolic nanofluid flow with chemical reaction and activation energy

In this research, we take into account tangent hyperbolic nanofluid flow along a moving stretched surface with thermal radiation, exothermic/endothermic chemical reaction and activation energy effects under melting condition. Governing PDE are transformed to dimensionless non-linear ODE with the add of appropriate similarity variables. The resulting non-linear ODE are solved numerically. The flow parameters influences on the fluid?s velocity, temperature, and concentration distributions are investigated. The results revealed that temperature profile is declining while concentration and velocity profiles are increasing for enhancing melting parameter.

Investigation of gallium and tin on IG5 commercial chalcogenide glass and glass ceramics

In this research, optical, mechanical, and thermal properties of chalcogenide glasses in a Se-Ge-Sb system were studied with 1, 3, 5, 7, and 9 % Gallium and tin. Glass samples melted at 850 °C for 20 h were quenched in the melted salt. XRD analyses were performed for them. The properties of this ternary system compared in presence of two different additive. The aim of this study was to improve the mechanical properties of the Se60Sb12Ge28 chalcogenide glass (IG5) with the thermal treatment and prepare glass ceramics with high strength and IR transmittance. The glasses exhibited about 70 % IR-transmission around 2–17 µm with the weakest peaks. The hardness of these pure glasses increased by adding the Gallium and improvement of the melting conditions and quenching so that it reached ∼ 230–345 Kg.mm2. This high hardness was firstly reported for chalcogenide glasses. Appropriate temperature and time were selected to precipitate sub-micron nanocrystals and prepare ceramic glasses, heat treatment was also performed. The size and distribution of nanocrystals in the glass ceramic microstructure was investigated by Fe-SEM and TEM. The hardness of this ceramic glass reached to ∼ 280–370 MPa by precipitation of nanocrystals with diameter of 100–400 nm.

Late glacial glaciomarine and Holocene marine sediments in the eastern part of the Barents Sea: structure composition; thickness; conditions of formation

Geological-geophysical dates are showing that Holocene marine and Late Glacial glaciomarine sediments in the eastern Barents Sea represent seismostratigraphic complexes (SSC), accordingly SSCI and SSCII. Th e composed of glacial mineral matter sediments SSCII formed in the time of the Barents Sea shelf deglaciation, but the sediments SSCI deposited in conditions of open marine basin and are terrigenious. Features of the structure, composition and thicknesses of sediments SSCII are defi nite by melting conditions of degraded glacier masses and by character of originated sedimentation basins, but of sediments SSCI — by hydrodynamic factor and, partially, — by processes of last glacial eustatic marine transgression.

Geochemical Signatures of Felsic Volcanic Rocks in Modern Oceanic Settings and Implications for Archean Greenstone Belts

Abstract Felsic volcanic rocks are abundant in ancient greenstone belts and important host rocks for volcanogenic massive sulfide (VMS) deposits. About half of all VMS deposits are hosted by dacite or rhyolite, an association that reflects anomalous heat flow during rifting, partial melting of basaltic crust, and fractional crystallization in high-level magma chambers. For over 30 years, geochemical signatures of these rocks (e.g., F classification of Archean rhyolites) have been widely used to identify possible hosts for VMS deposits in ancient greenstone belts. However, comparisons with modern oceanic settings have been limited, owing to a lack of samples of felsic volcanic rocks from the sea floor. This is changing with increasing exploration of the oceans. In this study, we have compiled high-quality geochemical analyses of more than 2,200 unique samples of submarine felsic volcanic rocks (>60 wt % SiO2) from a wide range of settings, including mid-ocean ridges, ridge-hot-spot intersections, intraoceanic arc and back-arc spreading centers, and ocean islands. The compiled data show significant geochemical diversity spanning the full range of compositions of rhyolites found in ancient greenstone belts. This diversity is interpreted to reflect variations in crustal thickness, the presence or absence of slab-derived fluids (dry melting versus wet melting), and mantle anomalies. Highly variable melting conditions are thought to be related to short-lived microplate domains, such as those caused by diffuse spreading and multiple overlapping spreading centers. Systematic differences in the compositions of felsic volcanic rocks in the modern oceanic settings are revealed by a combination of principal components analysis, unsupervised hierarchical clustering, and supervised random forest classification of the compiled data. Dacites and rhyolites from midocean ridge settings have moderately depleted mantle signatures, whereas rocks from ridge-hot-spot intersections and ocean islands reflect enriched mantle sources. Felsic volcanic rocks from arc-back-arc systems have strongly depleted mantle signatures and well-known subduction-related chemistry (strong large ion lithophile element enrichment in combination with strong negative Nb-Ta anomalies and low heavy rare earth elements [HREEs]). This contrasts with felsic volcanic rocks in Archean greenstone belts, which show high field strength element and HREE enrichment (so-called FIIIb-type) due to a less depleted mantle, a lack of wet melting, and variable crustal contamination. The differences between modern and ancient volcanic rocks are interpreted to reflect the lower mantle temperatures, thinner crust, and subduction-related processes in present-day settings. We suggest that the abundance of FIIIb-type felsic volcanic rocks in Archean greenstone belts is related to buoyant microplate domains with thickened oceanic crust that were better preserved on emerging Archean cratons, whereas in post-Archean tectonic settings most of these rocks are subducted.

Solidification of phase change materials in horizontal annuli

This paper presents experimental results on solidification of n-octadecane and dodecanoic acid in horizontal annuli with 18-, 27-, and 36-mm center tubes and a 127-mm outer cylinder. Dodecanoic acid was superheated to 2.5 °C above the solidification temperature and n-octadecane was superheated by 2.5 or 37.5 °C. Dodecanoic acid was solidified from the center tubes at temperatures 8.44, 21.1, or 33.8 °C below the solidification temperature; these temperatures for n-octadecane were 8.44 or 21.1 °C. Additionally, the solidification of dodecanoic acid was studied under the conditions of consecutive melting and solidification, where it was subcooled by 2.5 °C and the superheating was dictated by the melting conditions. For these cases, the melting/solidification temperature differentials were 16.9 or 33.8 °C above/below the melting/solidification temperature. A comparative study of melting and solidification of n-octadecane was also done. For the melting experiments, n-octadecane was subcooled by 2.5 °C and melted at 21.1 °C above the melting temperature, which was compared to the respective solidification experiments. The volumes of solid/liquid PCMs per unit length of the enclosures and the positions of solid-liquid interfaces were obtained photographically. The results show that the solidification rates can be enhanced by using a larger center tube, solidifying the PCM at a lower temperature, and using PCMs initially liquid close to the solidification temperature. The effects of these parameters are greater on the solidification of n-octadecane than dodecanoic acid. The effects of PCMs on the solidification process depend on how strong the conductive heat transfer is. The results also show that up to 30 % (if not more) of solidification can be contributed by natural convection in the early stages of the solidification process.

Nonlinear Optimization Algorithms for Adjusting Selective Laser Melting Conditions

Nonlinear Optimization Algorithms for Adjusting Selective Laser Melting Conditions

Optimization of Selective Laser Melting Process Parameters Via Taguchi's Methods and Gray Relational Analysis for 3D Printing of 18Ni‐300 Maraging Steel

Taguchi methods and gray relational analysis are used to determine optimal processing conditions for the selective laser melting (SLM) of 18Ni‐300 maraging steel. The following SLM process parameters are selected for optimization: laser power (P), scanning speed (v), and hatch spacing (h). Statistical analysis indicates that SLM parameter configuration no. 5 (275 W, 700 mm s−1, 0.08 mm) as most suitable for the simultaneous improvement of tensile strength, elongation (or ductility), hardness, and impact toughness. The order of influence of SLM parameters is identified as follows: . Samples with improved mechanical properties can be produced using configurations with higher linear energy density (). This is because the increased laser energy input facilitates complete melting of metal powder, as well as better interlayer bonding between melt pools. Higher can be achieved by either increasing P or decreasing v. Digital image correlation analysis indicates that tensile test samples with higher porosity exhibit lower ductility due to its inability to accommodate plastic strain accumulation for prolonged durations. Fractography analysis indicates that during tensile loading, cracks will nucleate around the pore perimeter and propagate via microvoid coalescence. Fracture will occur at regions with higher porosity due to it having multiple crack initiation sites.

Study of the Possibility of Recycling of Technogenic Hafnium during Electron Beam Refining

The possibility of removing metallic (such as Zr, Fe, Cr, and Zn) impurities and non-metallic (such as [O] and C) impurities from technogenic hafnium through single and double refining in the conditions of electron beam melting (EBM) has been studied. The influence of thermodynamic and kinetic parameters on the degree of removal of these impurities from the base metal under vacuum conditions and within a temperature interval of 2500 K to 3100 K is defined. The relative volatility of metal impurities and the stability of the oxides and carbides present in the base metal are evaluated. The possibility for complete removal of Fe, Cr, Zn, [O], and C during EBM is shown. In the case of double refining, at a temperature of 2700 K for 20 min, the maximum degree of removal of Zr is 46.8%, the achieved highest hafnium purity is 99.004%, and the overall effectiveness of the refining of hafnium from impurities is 53%. There is a correlation between the degree of removal of Zr and the micro-hardness of the Hf ingots obtained after EBM. The weight losses vary in the ranges of 1.5-5.8% and 1-8% under the studied single and double refining processes, respectively.

Entanglement Length Scale Separates Threading from Branching of Unknotted and Non-concatenated Ring Polymers in Melts.

Current theories on the conformation and dynamics of unknotted and non-concatenated ring polymers in melt conditions describe each ring as a tree-like double-folded object. While evidence from simulations supports this picture on a single ring level, other works show pairs of rings also thread each other, a feature overlooked in the tree theories. Here we reconcile this dichotomy using Monte Carlo simulations of the ring melts with different bending rigidities. We find that rings are double-folded (more strongly for stiffer rings) on and above the entanglement length scale, while the threadings are localized on smaller scales. The different theories disagree on the details of the tree structure, i.e., the fractal dimension of the backbone of the tree. In the stiffer melts we find an indication of a self-avoiding scaling of the backbone, while more flexible chains do not exhibit such a regime. Moreover, the theories commonly neglect threadings and assign different importance to the impact of the progressive constraint release (tube dilation) on single ring relaxation due to the motion of other rings. Despite that each threading creates only a small opening in the double-folded structure, the threading loops can be numerous and their length can exceed substantially the entanglement scale. We link the threading constraints to the divergence of the relaxation time of a ring, if the tube dilation is hindered by pinning a fraction of other rings in space. Current theories do not predict such divergence and predict faster than measured diffusion of rings, pointing at the relevance of the threading constraints in unpinned systems as well. Revision of the theories with explicit threading constraints might elucidate the validity of the conjectured existence of topological glass.

The effect of process parameters and scanning strategies on surface roughness of stainless steel 316L SLM parts

Selective Laser Melting (SLM) process is a powder-based metal Additive Manufacturing (AM) technique that can generate fully functional and geometrically complex shapes which can be used in actual load-bearing situations. The mechanical properties of SLM parts are highly dependent on process parameters. Generally, the as-built surface quality of SLM parts is not good enough, and finding the optimum values of the parameters to improve surface quality is an ongoing challenge. In this study, an experimental approach was taken to investigate the effect of process parameters and scanning strategy on the surface roughness of stainless steel 316L parts as well as determine the optimal values of parameters and optimum scanning strategy. Laser profilometry was applied to measure surface roughness. Results showed that the scanning speed was the most effective parameter; increasing it from 900 mm/s to 1200 mm/s caused 62.5% rougher surfaces. Also, increasing laser power from 255 W to 300 W resulted in 41.8% rougher surfaces. Smaller hatch spaces caused better surface quality; decreasing it from 0.1 mm to 0.04 mm improved surface quality by 16%. And lower scan pattern angles resulted in slightly rougher surfaces (by 2%). Changing the settings from minimum overlap to maximum overlap resulted in 73.6% better surface quality. It was found that insufficient melting is the main reason for poor surface quality. Surface quality was improved whenever the resultant effect of parameters caused sufficient melting conditions. The optimum values were found as 270 W laser power, 900 mm/s scanning speed, 0.06 mm hatch spacing and 75° scan pattern angle. The best surface quality was obtained for the chessboard scanning strategy, with scan vectors being parallel to each other in adjacent blocks and rotating by 90° in successive layers. The optimum strategy caused 2.5 times better surface quality than the strategy of the roughest sample.

Effect of network connectivity on behavior of synthetic Broborg hillfort glasses

AbstractThere is wide industrial interest in developing robust models of long‐term (>100 years) glass durability. Archeological glass analogs, glasses of similar composition, and alteration conditions to those being tested for durability can be used to evaluate and inform such models. Two such analog glasses from a 1500‐year‐old vitrified hillfort near Uppsala, Sweden have previously been identified as potential analogs for low concentration Fe‐bearing aluminosilicate nuclear waste glasses. However, open questions remain regarding the melting environment from which these historic glasses were formed and the effect of these conditions on their chemical durability. A key factor to answering the previous melting and durability questions is the redox state of Fe in the starting and final materials. Past work has shown that the melting conditions of a glass‐forming melt may influence the redox ratio value (Fe+3/∑Fe), a measure of a glass's redox state, and both melting conditions and the redox ratio may influence the glass alteration behavior. Synthetic analogs of the hillfort glasses have been produced using either fully oxidized or reduced Fe precursors to address this question.In this study, the melting behavior, glass transition temperature, oxidation state, network structure, and chemical durability of these synthesized glass analogs is presented. Resulting data suggests that the degree of network connectivity as impacted by the oxidation state of iron impacted the behavior of the glass‐forming melt but in this case does not affect the chemical durability of the final glass. Glasses with a lower degree of melt connectivity were found to have a lower viscosity, resulting in a lower glass transition temperature and softening temperature, as well as in a lower temperature of foam onset and temperature of foam maximum. This lower degree of network connectivity most likely played a more significant role in accelerating the conversion of batch chemicals into glass than the presence of water vapor in the furnace's atmosphere. Future work will focus on using the results from this work with outcomes from other aspects of this project to evaluate long‐term glass alteration models.

The effects of source composition and melting conditions on the composition of syn-exhumation granites in collisional orogen

Partial melting of the deeply subducted continental crust during exhumation has been widely recognized recently in collisional orogens. However, it is little known about the effects of source composition and melting conditions on the composition of syn -exhumation granitic rocks. This is investigated by studying zircon and titanite U Pb geochronology and whole-rock geochemistry for syn -exhumation granites from the Weihai area in the Sulu orogen. The U Pb dating of relict zircon cores yields concordant Neoproterozoic and Late Triassic ages, respectively, for the meta-igneous protolith and granulite-facies metamorphism. Magmatic zircon rims give U Pb ages of 207 ± 1 to 214 ± 2 Ma for the formation of Weihai granites, in agreement with magmatic titanite ages of 209 ± 6 to 217 ± 5 Ma in the Late Triassic. The compositional zonation of titanite shows decreases of Nb/Ta and (La/Yb) N from core to rim, indicating the geochemical changes during granitic magmatism. In general, these granites show arc-like trace element distribution patterns and enriched Sr–Nd–Hf isotope compositions with an affinity to deeply subducted crustal slices from the South China Block. Compared with previously reported syn -exhumation granites from Lanshan in the southern Sulu orogen, the Weihai granites in the northeastern Sulu orogen exhibit different Sr-Nd-O isotope compositions. The Weihai granites have relatively low SiO 2 and Na 2 O contents but high Al 2 O 3 and K 2 O contents with high A/CNK and K/Na ratios. They contain high Ba and Sr but low Y with high Sr/Y and (La/Yb) N ratios. Both zircon and whole-rock of the Weihai granites exhibit no significant negative Eu anomalies. Based on the differences in geochemical features and the spatial-temporal distributions, it is inferred that the syn -exhumation granites in the Weihai area are derived from decompressional melting of the lower crustal slice at greater depth, whereas those in the Lanshan area are derived from decompressional melting of the upper crustal slice at relatively shallower depth. These differences indicate that both source compositions and melting conditions have exerted significant influences on the geochemical composition of syn -exhumation granites in the collisional orogen. This has bearing on the crust-mantle interaction in continental subduction channel through metasomatic reaction of the mantle wedge with these granitic melts produced during the exhumation. • The Weihai granites in the northern Sulu orogen indicate syn -exhumation magmatism. • The Weihai granites are characterized by relatively high Sr/Y and (La/Yb) N ratios. • Syn-exhumation granites in the Sulu orogen are distinct from south to north. • Differences in source compositions and melting conditions caused the compositional diversity of granites.

Role of aqueous fluids during low pressure partial melting of pelites in the Adamello pluton contact aureole (Italy)

The contact aureole of the Adamello pluton (Italy) exhibits a rare combination of pelitic rocks anatexis around a shallow metaluminous pluton and formation of interconnected leucosomes, aplites and small lithium and cesium-enriched pegmatitic bodies. Contact metamorphic mineral assemblages are described in the non-graphitic pelites and psammites hosting the pluton in the central sector of the Adamello Massif. Three metamorphic zones are identified on the field: I – Muscovite-Biotite, II – Andalusite-Sillimanite-K feldspar, III – Melt zone. In the melt zone, the presence or absence of high temperature Crd defines two types of migmatites, a Crd-bearing metatexite characterized by orbicular textures and a Crd-absent stromatic metatexite. Peak P-T metamorphic conditions in the Adamello pluton thermal aureole were calculated at 690–700 °C and 3 kbar on the basis of phase equilibria and geothermobarometry. Phase equilibria modelling reveals that Crd-bearing migmatites, which produced around 20 vol% melt fraction, were generated through internal fluids-buffered partial melting conditions while Crd-absent stromatic metatexites, which produced ca. 35 vol% melt fraction, originated through local fluid present partial melting. Different types of leucosomes were produced by these two partial melting conditions. In-situ leucosomes linked to Crd-bearing migmatites are compositionally similar to primary liquid predicted by phase equilibria modelling (calculated at peak P-T conditions). Leucosomes within the Crd-absent stromatic metatexites show residual mineral compositions extremely enriched in Kfs and Bt and are connected to extraction structures. Their whole rock composition does not represent a primary melt while being compatible with Kfs cumulate textures. The extracted melt from the stromatic metatexites was calculated to be compatible with the spatially related Li-rich pegmatites mean composition, which are hosted by the same geological formation. The studied area shows the small-scale variability in intraformational fluids participation during metamorphic reactions while demonstrating the hybrid nature of partial melting in anatectic terranes. • Differential fluids influx created different migmatites from one protolith. • Extracted anatectic melt closely fits the self-hosted LCT pegmatites composition. • Fluid circulation in metamorphism causes hybrid fluid absent - present anatexis.

Unprecedented differences in phytoplankton community structures in the Amundsen Sea Polynyas, West Antarctica

In the Antarctic coast, ice shelves are rapidly thinning and retreating due to global warming. Basal melt water influences marine life, particularly the phytoplankton, which are directly affected by changes in physicochemical environments. However, there is limited in situ data over large areas in the Amundsen Sea, which is currently a hotspot for rapidly thinning ice shelves in West Antarctica. During the austral summer cruise of 2020, phytoplankton species abundance was investigated along the Amundsen Sea coast using an automated continuous observation instrument, the Imaging FlowCytobot. The phytoplankton community was dominated by Phaeocystis antarctica in most coastal waters of the Amundsen Sea, as previously reported; however, unexpected blooms of diatom Dactyliosolen tenuijunctus were observed throughout the Pine Island Bay region at a high dominance rate (∼90%) and abundance (>107 cells l−1). D. tenuijunctus is a weakly silicified diatom and its massive bloom in the water column has been rarely reported from the Antarctic Ocean. The dramatic difference in phytoplankton compositions between these adjacent polynyas probably indicates an unstable response of phytoplankton to ice melting conditions. They could play a different role in the marine food web and carbon flux compared to other diatoms and P. antarctica. Therefore, further research is warranted to predict the biological and biogeochemical impacts of future melting conditions.

Degassing of Aluminum Alloy Melts by High Shear Melt Conditioning Technology: An Overview

The search for more efficient methods for degassing aluminum alloy melts has always been of great interest for the metal industry because the presence of hydrogen and oxides in the melts’ prior casting was detrimental to the integrity and properties of the final products. In this work, we present an overview of the progress and key findings from the research and development of an innovative High Shear Melt Conditioning (HSMC) degassing technology during the Liquid Metal Engineering (LiME) Research Hub project. Compared to conventional rotary degassing, this novel technique was capable of working at higher rotor speeds to efficiently break and disperse the naturally occurring oxide bifilms in the melt and to capture and disperse each supplied inert gas bubble into many tiny bubbles throughout the whole melt. This resulted in the elimination of the need to degas fluxes to remove the oxides in the melt, the reduction in the gas flow required to reach the same level of hydrogen removal rate, and the minimization of the regassing effect after processing. The increased process efficiency allowed for reduced melt processing costs and, at the same time, improved the melt quality, which resulted in fewer defects and improved mechanical properties.

Colorless, highly refractive, and zero photoelastic calcium tin phosphate glasses

We prepared visible-wavelength-transparent, highly refractive, and very small photoelastic oxide glasses composed of common elements by a process that is suitable for mass-production in the glass industry. The present calcium tin phosphate glass materials, which are suitable replacements for PbO-containing silicate glass, will be part of optical devices such as lenses, fibers, and filters; and thus will contribute to environmental sustainability. We used starting materials and simple melting conditions that suppressed oxidation of divalent tin. The CaO-, BaO-, and SnO-containing phosphate-based glasses met stringent optical properties and realistic material-processing parameters. However, SnO-free oxide glasses did not have a very small photoelasticity (defined here as less than +0.1 TPa−1).

Bronze Production Systems in 6-7 Centuries South Korea: Micro-Structural and Micro-Chemical Analysis of Slags

Metallurgical remains such as crucible, mould, slag and tuyere are generated in the production of bronze. The analysis of slag in particular can be used to identify the raw materials, processes and environments (temperature and condition) employed in the bronze fabrication . The Gwanbuk-ri site in Buyeo is known as the location of a royal palace during the Baekje period, in the 6-7th centuries, and crucible fragments and slags used to make bronze were excavated there. The purpose of this study is to understand the process of bronze production and the origin of the raw ores used in the Baekje period, through micro-structure and microchemical analyses. Using chemical analysis and observation of the microstructure of the crucible and slag samples, we identified evidence of the bronze alloying and melting conditions. The melting process would have taken place under a variable redox atmosphere at 1,100 oC. Cu-Sn-Pb ternary bronze might have been produced by alloying Cu-Sn metal with lead ore (galena) in the Baekje period. The lead isotope composition ratios of 2 bronze slags were located in zone 2 and zone 3 of the lead isotope map in the southern Korean peninsula, which indicates the use of galena from south Chungcheong and north Gyeongsan provinces. For efficiency and cost-effectiveness, a concentrate of lead ore might have been transported from the mine to the consumer site.