Melt Phase Research Articles

High‐Temperature Fracture Growth by Constrained Sintering of Jadeite and Quartz Aggregates

AbstractFractures control heat and mass transfer and rheology in a wide range of subsurface regimes, ranging from low‐temperature diagenetic environments to high‐temperature metamorphic and magmatic systems. To investigate processes of opening‐mode fracture growth at high homologous temperature, we conducted constrained high‐temperature sintering experiments of thin layers of porous jadeite and quartz aggregate attached to a non‐sintering mullite substrate. Samples were heated stepwise at a low rate in a muffle furnace from 25°C to 1,000°C under ambient air pressure and examined for changes in mineral composition, texture, porosity, and fracture morphology using powder‐X‐ray diffraction, macro‐photography, reflected incident light microscopy, and secondary electron microscopy. Mineral reactions in the jadeite and quartz sample layer include jadeite and quartz reacting to albite at 600°C and the formation of nepheline and orthoclase at 900°C and 1,000°C. Opening‐mode fractures are first observed at 850°C coincident with the first presence of a melt phase with low aperture‐to‐length ratios similar to elastic‐brittle fractures. At 900°C, melt becomes increasingly abundant, and fractures obtain ductile morphology with high aperture‐to length ratios and blunted tips resulting from fracture growth by growth and coalescence of larger pores at the expense of smaller pores. In the absence of an externally applied mechanical load, we conclude that fracture growth is driven primarily by sintering stress resulting from differential contraction between sample layer and substrate associated with high‐temperature mineral reactions, melt formation and redistribution, and changes in pore structure. Similar fracture processes may be relevant to the segregation and migration of melt in magmatic systems.

A Drop-In High-Temperature Pb-Free Solder Paste That Outperforms High-Pb Pastes in Power Discrete Applications

Sn-based high-temperature Pb-free (HTLF) solder pastes have been developed as a drop-in solution to replace high- Pb solder pastes in power discrete applications. The pastes were designed with Indium Corporation’s DurafuseVR technology, to combine the merits of two constituent powders. A SnSb-based Ag/ Cu-containing high-temperature powder, with a melting temperature above 320 degrees C, was designed to maintain high-temperature performance. A Sn-rich SnAgCu-Sb powder, with a melting temperature around 228 degrees C, was added to the paste to enhance wetting and improve joint ductility. In the design, the final joint will have the low-melting phase (the melting temperature >228 degrees C) in a controllable quantity embedded into the high-melting SnSb matrix. HTLF-1, one of the designs, maintained the bond shear strength up to 15 MPa, even around 290 degrees C. Another design, HTLF-2, has a similar bond shear strength as Pb92.5/Sn5/Ag2.5 around 290 degrees C, but exceeds substantially below 250 degrees C. The power discrete components had been built with both HTLF solder pastes for both die-attach and clip-bond through the traditional high-Pb process, which demonstrated the drop-in processing compatibility. The components survived three additional surface mounting (SMT) reflows (peak temperature upto 260 degrees C) and passed moisture sensitivity level 1 (MSL1). This confirmed that the maintained joint strength (comparable to or stronger than high-Pb), helped to keep the joint integrity within the encapsulated components in the following SMT process, even with the controlled quantity of the melting phases above 228 degrees C. Both HTLF solder pastes outperformed Pb92.5/Sn5/Ag2.5 in the resistance from drain to source when power is on (RDS(on)), even after 1,000 cycles of temperature cycling test (TCT) under 255/175 degrees C, which is attributed to the intrinsic lower electrical resistivity of Sn in both HTLF pastes. Microstructural observation had shown no corner cracks for both die-attach and clip-bond joints after TCT.

Ash Transformation during Fixed-Bed Co-combustion of Sewage Sludge and Agricultural Residues with a Focus on Phosphorus.

This work investigates the ash transformation during fixed-bed co-combustion of sewage sludge mixtures with the agricultural residues wheat straw and sunflower husks, focusing on the fate of phosphorus (P) in the resulting ash fractions. The study aims to determine suitable process parameters for fixed-bed combustion of fuels previously investigated in single-pellet experiments. The pure fuels and fuel mixtures were combusted in a 20 kWth residential pellet burner while monitoring the flue gas composition, temperature, and particulate matter formation. Subsequently, the different ash fractions were collected and characterized by CHN, SEM/EDS, and XRD analysis. The results showed that co-combustion of sewage sludge and agricultural residues reduced the formation of particulate matter as well as the formation of slag. Co-combustion of sewage sludge with either agricultural residue resulted in a change in phosphate speciation, displaying higher shares of Ca and lower shares of Fe and Al in the formed orthophosphates as well as amorphous phases containing higher shares of K. The formation of K-bearing phosphates was hindered by the spatial association of P with Ca and Fe in the sewage sludge, the incorporation of available K in K-Al silicates, and the depletion of K in the P-rich melt phase. Compared to mono-combustion, co-combustion experiments showed the potential for improving the combustion performance and reducing the risk of slag formation. The outcome suggests that co-combustion is a feasible path to integrate waste streams in fixed-bed energy conversion with simultaneous formation of phosphates enabling P recovery.

A general non-Fourier Stefan problem formulation that accounts for memory effects

The Stefan problem is the classical model of a melting phase change. In heterogeneous systems, such phase changes can exhibit non-Fourier (anomalous) behaviors, where the advance of the melt interface does not follow the expected time scaling. These situations can be modeled by replacing the derivatives, in the governing partial differential equations, with fractional order derivatives. In particular, replacing the time derivatives leads to non-Fourier models that account for memory effects in the system. In this work, by using appropriate time convolution integrals, a general thermodynamic balance statement for melting phase problems, explicitly accounting for memory effects, is developed. From this balance, a general model formulation applicable to problems involving melting over a temperature range (i.e., a mushy region) is derived. A key component in this model is the representation of memory effects through the use of fractional derivative based constitutive models of the enthalpy and heat flux. On shrinking the mushy region to a single isotherm, a general sharp interface melting model is obtained. Here, in contrast to the classic Stefan problem, the fractional derivatives induce a natural regularization, such that the constitutive models for enthalpy and heat flux are continuous at the melt interface; a result confirmed through numerical simulation. To further support the theoretical findings, a physical example of a non-Fourier Stefan problem is presented. Overall the development and results in this paper underscore the importance of explicitly relating the development of fractional calculus models to the appropriate thermodynamic balance statements.

Thermophysical parameters governing the glass formation and crystallization of CuZr

Cu-Zr is one of the best binary metallic glass formers. Here, new data on the enthalpy and specific heat difference between undercooled melt and crystal phases are provided for the equiatomic composition CuZr. Together with a comprehensive collection of literature data on the heat of crystallization and fusion, on the viscosity and crystal growth rate, the parameters needed for the application of the Classical Nucleation Theory are assessed. The TTT and CCT curves for crystallization are computed allowing the determination of the crystal-liquid interfacial energy by fitting the critical cooling rate for bulk glass formation.The glass forming tendency of CuZr is discussed pointing to the role of the high interfacial energy and the sluggish interdiffusion in the undercooled melt.

Novel insight into the self-lubricating mechanism of Cu–Pb bearing alloy during sliding friction with the guidance of molecular dynamics

The self-lubricating mechanism of Cu–Pb bearing alloy is discussed by molecular dynamics (MD). MD friction tests are conducted on the pure Cu and Cu–Pb models. The Pb-rich secondary phases (PSPs) melt due to the frictional heat. The solid–liquid phase transition of Pb is characterized by the radial distribution function (RDF) and the potential energy. An obvious drop of motion resistance of the abrasive debris is observed in Cu–Pb alloy once the debris moves close to the soft PSP which protect the matrix from abrasion by embedding the debris and promoting the formation of a liquid lubricant film. The synchrotron radiation technology is employed to in-situ observe the phase transition of Pb, and the MD results match the experimental results well.

A simplified core catcher model for the containment code AC2/COCOSYS

In Generation 3+ NPPs such as EPR or WWER-1200 the ex-vessel core catcher presents a key component of the severe accident mitigation concept. A simplified core catcher model in the containment code COCOSYS (part of AC2 code package) is developed to consider core melt retention and cooling phenomena in core catchers for containment simulations. The model enables the characterization of the corium in the core catcher including processes in the corium conditioning phase (melting of sacrificial material in the core catcher, oxidation of metallic components, possible layer flip) and the long-term cooling phase (evolution of long-term corium pool bulk temperature and changes in physical state). The core catcher model is based on the existing molten corium / concrete interaction (MCCI) model in COCOSYS with additions for melt retention within water-cooled structures and input data can be adapted to simulate various core catcher design features of e. g. NPPs with EPR or WWER.The current state of the model, including basic assumptions, calculation methods, simplifications, and two application examples are outlined. The recalculation of the water-cooled basemat test OECD WCB-1 shows that the experimental data regarding e. g. the ablation of the sacrificial concrete on top of the water-cooled basemat, corium pool temperature and heat fluxes at water-cooled interfaces can be adequately reproduced by the COCOSYS simulation, when using empirical data for the heat transfer, including the MCCI phase. These empirical heat transfer data agree well with findings obtained from recent analytical work on MCCI tests. However, the model does not predict high local bottom plate temperatures as observed in the WCB-1 test due to a restriction of the model to quasi-steady state processes. The second calculation example demonstrates the current modelling features when applied to an axisymmetric geometry of a reactor-scale core catcher. With view to reactor-scale, the model is ready for a further verification, like e.g. comparison with other analytical core catcher approaches.

Microstructural diversity, nucleation paths, and phase behavior in binary mixtures of charged colloidal spheres.

We study low-salt, binary aqueous suspensions of charged colloidal spheres of size ratio Γ = 0.57, number densities below the eutectic number density nE, and number fractions of p = 1.00-0.40. The typical phase obtained by solidification from a homogeneous shear-melt is a substitutional alloy with a body centered cubic structure. In strictly gas-tight vials, the polycrystalline solid is stable against melting and further phase transformation for extended times. For comparison, we also prepare the same samples by slow, mechanically undisturbed deionization in commercial slit cells. These cells feature a complex but well reproducible sequence of global and local gradients in salt concentration, number density, and composition as induced by successive deionization, phoretic transport, and differential settling of the components, respectively. Moreover, they provide an extended bottom surface suitable for heterogeneous nucleation of the β-phase. We give a detailed qualitative characterization of the crystallization processes using imaging and optical microscopy. By contrast to the bulk samples, the initial alloy formation is not volume-filling, and we now observe also α- and β-phases with low solubility of the odd component. In addition to the initial homogeneous nucleation route, the interplay of gradients opens various further crystallization and transformation pathways leading to a great diversity of microstructures. Upon a subsequent increase in salt concentration, the crystals melt again. Wall-based, pebble-shaped β-phase crystals and facetted α-crystals melt last. Our observations suggest that the substitutional alloys formed in bulk experiments by homogeneous nucleation and subsequent growth are mechanically stable in the absence of solid-fluid interfaces but thermodynamically metastable.

Numerical studies on a fin-foam composite structure towards improving melting phase change

The low thermal conductivity of phase change materials limits the large-scale application of latent heat storage technology. It is meaningful to improve the thermal conductivity of phase change materials by corresponding means. In order to improve the performance of latent heat storage device, this paper takes square latent heat storage device as the research object, and uses fin and foam metal to enhance its melting performance. A 3-D numerical model is established and verified by visualization experiment. The quantitative comparison of melting properties of four different structures (pure paraffin, fin, metal foam, fin-metal foam) is presented. The results show that compared with pure paraffin structure, the complete melting time of phase change materials corresponding to fin, metal foam, and fin-metal foam structure is reduced by 47.48%, 79.53%, and 83.68%, respectively. The temperature uniformity increased by 28.97%, 79.37%, and 91.12%, and the total heat storage decreased by 6.0%, 4.6%, and 11.64%, respectively. It shows that the addition of fin and foam metal is beneficial to improve the melting performance and the overall temperature uniformity of the device, but it has a negative effect on total heat storage. Dynamic temperature studies were conducted to further explore the effect of fins and metal foam on the internal melting process compared with pure paraffin structure.

Melt/solid interaction and melt super-saturation effect on the microstructure asset of ultra-refractory composites prepared by reactive melting infiltration

The reactions occurring between a Zr2Cu melting phase and possible compounds intended for use in ultra-refractory ceramic matrix composite, i.e. SiC, TiB2 and ZrB2 are first explored through sessile drop tests, confirming a promising infiltration capability of the melt. Then, a multiphasic ultra-high temperature ceramic matrix composite was prepared by reactive melt infiltration (RMI), using a TiB2-coated carbon fiber preform infiltrated with Zr2Cu at 1500 °C which resulted in the precipitation of ZrB2 and ZrC sub-micrometric faceted grains and a general damage of both fiber and fiber coating, which were penetrated by the melt. Then, to decrease the RMI process temperature down to 1200 °C and limit the fiber damage degree, a second composite was prepared by introducing an additional ZrB2-B infiltration step. Although processing at 300 °C lower, notable alteration of the fiber occurred upon reaction with the Zr2Cu melt and developed a ZrC layer around them, but still allowing pull-out. In addition, the local B-rich environment promoted the development of a dual-phase microstructure within the matrix composed of new sub-micrometric grains and of larger ZrB2 grains, partially dissolved in the melt and re-precipitated acquiring a nano-sized lamellar eutectic structure. The combination of factors on multiple scale length, from the micro- of the fiber to the nano-of the lamella, seems to provide synergistic reinforcing phenomena and thus could be a valuable approach to develop materials for extreme environments.

Physical characterization of chocolates prepared with various soybean and milk powders.

The physical characterization of chocolate products is vital in manufacturing, and the chocolate's processing time and composition directly influence physical properties, such as rheology and melting. The objective of this study was to investigate the effects of processing time and the ingredient types on the physical properties of milk chocolates containing soy milk powder and soy protein isolate. Characteristics of skimmed milk chocolate (SMC) and whole milk chocolate (WMC) were compared to soy milk chocolate and soy protein chocolate (SPC). Rheological data of chocolate products were fitted to Casson, Herschel-Bulkley, and Bingham models. The highest viscosity was observed for SPC samples, whereas yield stress was the highest for SMC samples after 2hr of processing. The increase in milk and soy fats in the formulation softened the texture and decreased the whiteness index significantly (p < .05). PSD results show that SPC had the highest D90 (40.1μm) and the lowest specific surface area (893 m2 /kg) after 6hr of processing. SPC samples had the narrowest particle size distribution observed by the span values. X-ray diffraction analysis showed that all the samples had the desired Form V, crystal form. The differential scanning calorimetry thermogram was used to determine phase transitions and melting behaviors. At the end of processing, melting enthalpies (ΔHmelt ) were significantly lower (p < .05) in milk chocolates.

Experimental Determination of a Chiral Ternary Solubility Diagram and Its Interpretation in Gas Antisolvent Fractionation

Although crystallization has been widely applied for the enantiomeric enrichment of non-racemates both in research and in industrial applications, the physical-chemical background of chiral crystallizations is not as frequently discussed. A guide for the experimental determination of such phase equilibrium information is lacking. In the current paper, the experimental investigation of chiral melting phase equilibria, chiral solubility phase diagrams and their application in atmospheric and supercritical carbon dioxide-assisted enantiomeric enrichment is described and compared. Benzylammonium mandelate is a racemic compound; it shows eutectic behavior when molten. A similar eutonic composition was observed in its methanol phase diagram at 1 °C. The influence of the ternary solubility plot could be unequivocally discovered in atmospheric recrystallization experiments, which proved that the crystalline solid phase and the liquid phase were in an equilibrium. The interpretation of the results obtained at 20 MPa and 40 °C, using the methanol-carbon dioxide mixture as a pseudo-component, was more challenging. Although the eutonic composition was found to be the limiting enantiomeric excess value in this purification process as well, the high-pressure gas antisolvent fractionation results were only clearly thermodynamically controlled in certain concentration ranges.

Multi-scale isotopic heterogeneity reveals a complex magmatic evolution: An example from the wallundry suite granitoids of the lachlan fold belt, Australia

Open-system magmatic processes are expected to impart various sorts of isotopic heterogeneity upon the igneous rocks they produce. The range of processes under the “open-system” umbrella (e.g., simple two-component mixing, magma mingling, assimilation with fractional crystallization) cannot usually be uniquely identified using data from a single isotope system. The use of bulk-rock, mineral separate and in situ techniques and multiple isotope systems allows the characterization of isotopic variability at different sampling scales, illuminating details of the petrogenesis of a magmatic system. This approach has been applied to granitoids of the Wallundry Suite in the Lachlan Fold Belt, Australia. The Wallundry Suite exhibits variations in mineral assemblage, mineral composition and trends in bulk-rock major and trace element compositions consistent with the involvement of liquid-crystal sorting processes such as fractional crystallization. In situ paired O-Hf isotope data from zircon in six samples show an array indicating the isotopic evolution of the melt phase. Similarly, bulk-rock Sr-Nd-Hf isotope arrays support open-system magma evolution. These data combined with the petrographic observations and major and trace element geochemical variations suggest some form of assimilation-fractional crystallization process in the petrogenesis of the Wallundry Suite. Added complexity is revealed by two observations: 1) the isotopic variations are only weakly coupled to the lithology and major element compositions of the samples; and 2) there are distinguishable differences between the Hf isotope compositions of bulk-rock samples and those of the magmatic zircons they host. To varying degrees the rocks consistently show negative ΔεHfbulk-zrc values (i.e., the bulk-rock compositions have less radiogenic Hf isotope values than their coexisting zircons). The preservation of distinctly low Nd and Hf isotope ratios in an Fe-Ti oxide mineral separate suggests that the bulk-rock vs. zircon discrepancy is caused by the presence of unmelted components derived from a contaminant of continental origin (i.e., a rock with low Sm/Nd and Lu/Hf and thus unradiogenic Nd and Hf). Evidently, a complex interplay of assimilation, crystallization and melt segregation is required to account for the data. This investigation demonstrates that such complexity can, nevertheless, be disentangled through comparison of complementary isotope data at multiple sampling scales.

Dilution Driven Self-assembly and Re-entrant Phase Transition in Molecular Hydrogels

TX-100 molecular hydrogels exhibited re-entrant melt-gel-sol phase transition driven solely by dilution, which sequentially altered the self-assembly of the micellar formations and their population was investigated through the monitoring of the physical parameters namely, solution viscosity, particle size histogram, ergodicity, and gel rigidity modulus. This phenomenon was noticed at 20°C in the TX-100 concentration region of 0.2 to 1.2 M much above the critical micellar concentration of 0.22 mM. The particle size histograms revealed the presence of spherical micelles (size »3 nm) in the solution ([TX-100] &lt; 0.5 M) which formed entangled wormlike cylindrical micelles (apparent hydrodynamic radius » 50 nm) when (0.5 M&lt; [TX-100] &lt; 0.9 M) giving rise to a gel-like structure. Further increase in the TX-100 concentration increased the propensity of these wormlike cylindrical micelles that got randomly distributed creating a dense melt phase. Interestingly, we observed transition solely driven by dilution which defined complete re-entrant behavior at room temperature. These molecular gels could be created by dilution of the melt or concentration of the sol unlike in the polymer gels. Remarkably, this hitherto little known unique phenomenon was exhibited by a simple system of non-ionic surfactant solution. Thus, we have a hydration reversible gel at our disposal which has a special place in soft matter arena.

A thermoviscoelastic model for the one-way and two-way shape memory effects of semi-crystalline polymers

Both one-way and two-way shape memory effects induced by crystallization and melting transitions have been recently demonstrated in several semi-crystalline polymers. The paper proposes a novel thermoviscoelastic phase transition model accounting for the underlying mechanisms of the material. The nonlinear Adam-Gibbs model of structural relaxation and a modified Eying model of viscous flow are incorporated to characterize the thermomechanical behaviors of the amorphous phase. Another main feature of the model lies in the characterization of the formation and melting of the crystalline phase based on a theory of multiple natural configurations. Comparisons with uniaxial shape memory experiments show that the model can well reproduce the stress-strain-temperature responses in different loading conditions.

Geochemical variation in biotite from the Devonian South Mountain Batholith, Nova Scotia: Constraints on emplacement pressure, temperature, magma redox state and the development of a magmatic vapor phase (MVP)

Abstract Here we report the composition of biotite from the peraluminous Devonian South Mountain Batholith (SMB) of southwestern Nova Scotia (Canada), the largest intrusive body within the Appalachian orogen. The batholith was emplaced in two phases: an early (379–375 Ma) granodiorite-monzogranite suite (Stage 1) and a later (375–372 Ma) more-evolved monzogranite-leucogranite suite (Stage 2). Biotite analyses (major and minor elements) were obtained on 55 unmineralized samples representing 11 plutons. Regardless of the stage of pluton emplacement, biotite is commonly interstitial to alkali feldspar, quartz and plagioclase, indicating similar timing of biotite saturation. This suggests that biotite chemistry records conditions at similar extents of magma evolution for the chosen suite of samples. Biotite compositions are Fe-rich, with Fe/(Fe+Mg) ranging from 0.6 to 0.98, and Al-rich, with IVAl ranging from 2.2 to 2.9 atoms per formula unit (apfu; 22 oxygen basis), the latter reflecting the coexistence of other Al-rich phases, such as muscovite, garnet, aluminosilicates, and cordierite. Biotite anion sites are dominated by OH (&amp;gt;3 apfu), followed by F (~0.3 apfu) and Cl (≤0.02 apfu), with a general trend of decreasing OH, increasing F and a marked decrease in Cl, with increasing differentiation. Pressure (P) is estimated from the Al content of biotite to be between 280–430 MPa, consistent with a range of 240 to &amp;lt;470 MPa derived from phase equilibria and fluid inclusion microthermometry combined with mineral thermobarometry. Temperature (T) calculated from the Ti content of biotite ranges from 603–722 °C. Comparison of P-T estimates with water-saturated granite phase relations suggest minimum water contents of 6–7 wt% for the SMB magmas. The redox state of the SMB was estimated by comparing biotite Fe#-Ti relations with compositions calculated using the MELTS thermodynamic model, as experiments have shown that biotite Fe# increases with decreasing fO2 at a given extent of crystallization. Results of MELTS modeling for the most primitive magmas of the SMB sample suite indicate that the observed biotite Fe#-Ti variation is consistent with crystallization at FMQ to FMQ-1, with more oxidizing conditions suggested for the most strongly differentiated samples. To constrain the origin of the biotite anion site variation, a quantitative model using biotite-melt exchange coefficients (KD) derived from existing experimental data was used to track the change in biotite OH-F-Cl abundances as a function of crystallization, with or without an extant magmatic vapor phase (MVP). The model reproduces the relative OH, F, and Cl abundances in biotite, and suggests that SMB crystallization occurred in the presence of a MVP. The relatively reduced redox state of the SMB, similar to other peraluminous granitoid occurrences worldwide, aligns with other measures of fO2 for the SMB, including the occurrence of primary ilmenite. The observed correspondence between the estimated fO2 and that imposed by graphite-gas equilibrium suggests a role for reduced carbon in the generation and evolution of the SMB. This is consistent with evidence for SMB interaction with graphite-bearing felsic granulites of the underthrust Avalon terrane, and assimilation of carbonaceous and sulfidic metasediments during pluton ascent and emplacement. Reducing conditions and development of a MVP have implications for granophile element concentration processes in the SMB magmatic system. Low fO2 during crystallization affects the mineral/melt partitioning and solubility of the redox-sensitive elements Sn, W, U, and Mo, serving to suppress early SnO2 precipitation, and cause both an increase in W/Mo and an overall buildup of all four elements in evolving SMB liquids. Available experimental data indicate that reducing conditions also shifts DMVP/melt to favor partitioning into the melt phase. Therefore, early vapor exsolution under reducing conditions also lessens the extraction efficiency of these redox-sensitive elements to the MVP, further underscoring the role of extensive crystallization as an important metal enrichment process.

EFFECT OF SULFUR CONCENTRATION ON OLIVINE SULFIDATION UNDER LITHOSPHERIC MANTLE &lt;i&gt;PT&lt;/i&gt;-PARAMETERS

Experimental studies aimed at the modeling of interaction processes of sulfur-bearing metasomatic agents with mantle silicates and assessing the effect of sulfur concentration on olivine sulfidation were carried out in the Fe,Ni-olivine – sulfur system using the high-pressure multi-anvil apparatus BARS (1050 and 1450°C, 6.3 GPa, 40–60 hours, sulfur concentrations (Xs) 0.1, 2 and 6 mol. %.). It has been established that as a result of the recrystallization of Fe,Ni-olivine in a sulfur melt, Fe and Ni are extracted from olivine into this melt, and formation of Fe,Ni-sulfides (or sulfide melts) and low-iron, low-nickel silicates takes place. The key indicator characteristics of the olivine sulfidation process are determined depending on the temperature and sulfur concentration, including characteristic phase assemblages, regularities in the evolution of the chemical compositions of mineral and melt phases, and structural features of olivine crystals. It has been experimentally established that reducing sulfur-bearing metasomatic agents, even in minimal concentrations and at relatively low temperatures, are capable of dissolving and transporting mantle silicates and sulfides, and can play an important role in sulfide ore formation in the mantle.

Pulse-to-pulse ultrafast dynamics of highly photoexcited Ge2Sb2Te5 thin films

Observing ultrafast pulse-to-pulse dynamics of highly photoexcited materials could foster a comprehensive understanding of the initial stage of irreversible photoinduced events, such as phase change, structural deformation, and laser ablation. In this study, using high-repetition-rate single-shot spectroscopy and a laser microscope, the pulse-to-pulse ultrafast dynamics of energy relaxation in Ge2Sb2Te5 thin films are revealed under high-density photoexcitation that induces sequential events involving the crystalline-to-amorphous phase transition, melt and quench processes, and formation of laser-induced periodic surface structures (LIPSSs). Above the threshold excitation density for LIPSS formation, the first excitation pulse induces the transient transmittance change of the crystalline phase in a picosecond timescale, and subsequent pulses provoke the amorphous phase energy relaxation with a long decay time of hundreds of picoseconds. We observed that the subsequent pulses gradually reduce the amplitude and decay time of the transient transmittance, leading to efficient energy relaxation and LIPSS formation in the photoinduced amorphous phase.

Fractonic Berezinskii-Kosterlitz-Thouless transition from a renormalization group perspective

Proliferation of defects is a mechanism that allows for topological phase transitions. Such a phase transition is found in two dimensions for the XY model, which lies in the Berezinskii-Kosterlitz-Thouless (BKT) universality class. The transition point can be found using renormalization group analysis. We apply renormalization group arguments to determine the nature of BKT transitions for the three-dimensional plaquette-dimer model, which is a model that exhibits fractonic mobility constraints. We show that an important part of this analysis demands a modified dimensional analysis that changes the interpretation of scaling dimensions upon coarse-graining. Using this modified dimensional analysis, we compute the beta functions of the model and predict a finite critical value above which the fractonic phase melts, proliferating dipoles. Importantly, the transition point is found through a renormalization group analysis that accounts for the phenomenon of UV/IR mixing, characteristic of fractonic models.

Enantioselectivity of chiral dihydromyricetin in multicomponent solid solutions regulated by subtle structural mutation.

Multicomponent crystals of a chiral drug with non-chiral components have attracted increasing attention in the application of enantiomer purification and regulation of the physicochemical properties of crystalline materials. Crystalline solid solutions provide opportunities for fine-tuning material properties because of continuously adjustable component stoichiometry ratios. The synthesis, crystal structure, thermodynamics and solid-state enantioselectivity of a series of multicomponent crystals of chiral dihydromyricetin (DMY) with caffeine (CAF) or theophylline (THE) were investigated and the results reveal how the subtle change of molecular structure of the coformer dictates the enantiomer selectivity in multicomponent cocrystals. A series of multicomponent cocrystal solvates of chiral DMY with CAF and THE were synthesized by the slurry cocrystallization method in acetonitrile. Although most racemic mixtures crystallize as racemic compounds or conglomerates, both DMY-CAF and DMY-THE crystallize as chiral solid solutions, unveiled by pseudo-binary melt phase diagrams and pseudo-ternary solution phase diagrams. Crystal structures of Rac-DMY-CAF, R,R-DMY-CAF, Rac-DMY-THE and R,R-DMY-THE are reported for the first time via single-crystal X-ray diffraction, displaying two distinct types of solid solution differing in mixing scale of enantiomers spanning several orders of magnitude. Surprisingly, this remarkable impact on enantiomer discrimination was simply achieved by the reduction of a methyl group of CAF to the THE coformer, which was further rationalized from their crystal structures and intermolecular interactions. Collectively, this work has demonstrated that a subtle change in the molecular structure of a coformer can regulate enantioselectivity in crystalline materials, guiding the purification of chiral racemic compounds via the cocrystallization method and the design of solid-solution crystalline materials.