Melting Of Mixtures Research Articles

Investigating the Role of Natural Deep Eutectic Low Melting Mixtures for the Synthesis of Symmetrical Bisamides

AbstractKeeping in view the fundamental significance of bisamides in nature, medicine, and biological systems in addition to their utility in chemistry of synthons, there is a tremendous need to develop environmentally benign synthetic methodologies for the construction of bisamides and their congeners. Herein, for the first time, we report a green and highly efficient method for the synthesis of diverse symmetrical bisamides in good to excellent yields through the condensation of diverse aromatic aldehydes with amides under operationally simple reaction conditions. The present strategy involves a renewable, biodegradable, and reusable, natural deep eutectic mixture of choline chloride and L‐(+)‐tartaric acid in the ratio of 2 : 1 at 100 °C for the generation of a range of bisamides. Moreover, we have fruitfully assembled diverse urea‐based symmetrical bisamides with the usage of a low melting mixture of L‐(+)‐tartaric and urea (1 : 4) in decent yields. On large scale synthesis, both the methods were also found to be quite effective which leads to the formation of desired bisamides without significant decrease in the yields, thereby revealing their significance from industrial as well as academic viewpoint.

Molecular motion in mixtures of polymer melts in a capillary flow

The evolution of the morphology of two incompatible polymer melts in a capillary flow was studied using analytical electron microscopy. The spatial distribution of polysulfone and the liquid–crystal (LC) polymer was evaluated by measuring the concentration of sulfur (which is contained exclusively in polysulfone) and oxygen (contained in a much larger proportion in the LC polymer). The distributions of both polymers in the cross-sections of the strands do not change regardless of the specified shear rate, which varies by a factor of 25. However, a thin boundary layer with a width of about 10 μm formed by a low-viscosity LC polymer was detected. Nevertheless, there is a strong deformation and orientation of both polymers. This indicates that the movement of the mixture through the capillary occurs not due to sliding along the boundary layer but also due to shear in the entire volume of the material.

Effects of additives on the thermal stability of silver tellurite glass system

129I is notable for its long half-life of 1.57 × 107 y and high mobility in the environment. It should be immobilized in a geological disposal environment through a stable waste form. In this study, additives including Al, Bi, Pb, V, Mo, and W were added to silver tellurite glass, and the thermal properties of this matrix for radioactive iodine immobilization were evaluated. The glasses were prepared by the melt-quenching method, including the melting of the glass precursor mixtures at 800 °C for 1 h. The loading of iodine in the matrix was approximately 11–15% by weight, excluding the oxygen element. Differential scanning calorimetry was performed to evaluate the thermal properties of the glass samples. The glass transition temperature (Tg), crystallization temperature (Tc), and glass stability were investigated. The addition of MoO3 or WO3 in the glass system increases Tg and Tc while maintaining the glass stability.

Influence of metallurgical slag additives on proppants synthesis processes based on drilling muds

The slags formed during the smelting of ferrous alloys consist of more than 75% oxides of calcium, iron and silicon that predetermines broad prospects for their use as an alternative to natural raw materials. Considering the significant amount of alkaline earth oxides (calcium and magnesium) in the metallurgical slag, it seems promising to use it as a fluxing additive in highalumina aluminosilicate materials, one of which is proppants – granular aluminosilicate materials designed to enhance oil production by hydraulic fracturing. The aim of this work is to study the effect of metallurgical slag additives on the processes of proppant synthesis based on drill slurry. The composition of the initial drill slurry from the Morozovskoye deposit and the fluxing additive of metallurgical slag of JCS “TagMet” was studied. Based on the composition of the metallurgical slag, an assumption was made about its fluxing activity in the synthesis of silicate materials, which is due to a large amount of alkaline earth metal oxides, a low intensity of the crystalline phase and the presence of preliminary heat treatment. Five compositions of raw mixtures for the production of proppants were developed with the addition of two types of fluxing additives: metallurgical slag and sodium hydroxide. Qualitative (texture and color) and quantitative (density and sintering coefficient) parameters of the degree of sintering and melting of mixtures were determined. It was shown that both additives have a fluxing effect on drill slurry. It was found that the introduction of metallurgical slag leads to a change in texture to a more sintered one, as well as an increase in density and sintering coefficient. The introduction of sodium hydroxide has a more active effect on drill slurry, which leads to glass formation of the surface and further melting of the material. Physicochemical processes under the fluxing effect of the selected additives were considered, which is explained by the formation of more low-melting silicates, which reduce the final melting temperature of the mixture. The work was performed at YuRGPU (NPI) with the financial support of the Russian Science Foundation under the Agreement No. 20-79-10142 “Development of an effective technology for synthesis of aluminosilicate proppants using waste of drilling oil and gas wells of the Southern Federal District” (head – A. A. Tretyak).

Ethylene Glycol: Urea: NH4Cl Low Melting Mixture‐Assisted Reactions between Aromatic Aldehydes and Active Methylene Compounds

AbstractSustainable reaction processes have become a subject of high priority in the previous decade. Low melting mixtures play a great role in building up greener pathways for organic reactions. The easiness in preparation, low toxicity, non‐metallic behaviour, recyclability, low cost and biodegradability have made the low melting mixtures important. In this article, we explore the behaviour of the reaction between different active methylene compounds and aldehydes. A low melting mixture can act as solvent, catalyst and reactant when the reaction between aromatic aldehydes and active methylene groups are conducted. Ethylene Glycol: Urea: NH4Cl mixture was used as catalyst and solvent to get α‐β unsaturated products, while it behaved as catalyst, solvent and reactant to get dihydropyrimidinones. All the reactions were done at 30 °C which was the least reported in reactions with low melting mixtures. The physical properties such as solubility in organic solvents, density, acidity, viscosity, surface tension, refractive index, glass transition temperature, thermal stability, polarity, IR spectra and cytotoxicity of the mixture was studied. The α‐β unsaturated products and dihydropyrimidinones were characterized using GC‐MS, 1H NMR and 13C NMR spectroscopic techniques.

Effect of softness on glass melting and re-entrant solidification in mixtures of soft and hard colloids.

We present a systematic investigation of the structure and dynamic properties of model soft-hard colloidal mixtures. Results of a coarse-grained theoretical model are contrasted with rheological data, where the soft and hard colloids are mimicked by large star polymers with high functionality as the soft component and smaller stars with ultrahigh functionality as the hard one. Previous work by us revealed the recovery of the ergodicity of glassy soft star solutions and subsequent arrested phase separation and re-entrant solid transition upon progressive addition of small hard depletants. Here, we use different components to show that a small variation in softness has a significant impact on the state diagram of such mixtures. In particular, we establish that rendering the soft component more penetrable and modifying the size ratio bring about a remarkable shift in both the phase separation region and the glass-melting line so that the region of restored ergodicity can be notably enhanced and extended to much higher star polymer concentrations than for pure systems. We further rationalize our findings by analyzing the features of the depletion interaction induced by the smaller component that result from the interplay between the size ratio and the softness of the large component. These results demonstrate the great sensitivity of the phase behavior of entropic mixtures to small changes in the molecular architecture of the soft stars and point to the importance of accounting for details of the internal microstructure of soft colloidal particles for tailoring the flow properties of soft composites.

Pyroxenite as a Product of Mafic-Carbonate Melt Interaction (Tazheran Massif, West Baikal Area, Russia)

Pyroxenite and nepheline-pyroxene rocks coexist with dolomite-bearing calcite marbles in Tazheran Massif in the area of Lake Baikal, Siberia, Russia. Pyroxenites occur in a continuous elongate zone between marbles and beerbachites (metamorphosed gabbro dolerites) and in 5 cm to 20 m fragments among the marbles. Pyroxene in pyroxenite is rich in calcium and alumina (5–12 wt% Al2O3) and has a fassaite composition. The Tazheran pyroxenite may originate from a mafic subvolcanic source indicated by the presence of remnant dolerite found in one pyroxenite body. This origin can be explained in terms of interaction between mafic and crust-derived carbonatitic melts, judging by the mineralogy of pyroxenite bodies and their geological relations with marbles. According to this model, the intrusion of mantle mafic melts into thick lower crust saturated with fluids caused partial melting of silicate-carbonate material and produced carbonate and carbonate-silicate melts. The fassaite-bearing pyroxenite crystallized from a silicate-carbonate melt mixture which was produced by roughly synchronous injections of mafic, pyroxenitic, and carbonate melt batches. The ascending hydrous carbonate melts entrained fragments of pyroxenite that crystallized previously at a temperature exceeding the crystallization point of carbonates. Subsequently, while the whole magmatic system was cooling down, pyroxenite became metasomatized by circulating fluids, which led to the formation of assemblages with garnet, melilite, and scapolite.

A study on the physical properties of low melting mixtures and their use as catalysts/solvent in the synthesis of barbiturates

AbstractIn recent years, deep eutectic solvents have become attractive due to their interesting characteristics such as, physicochemical properties, low cost of components, easiness to prepare, low toxicity, bio‐renewability, and biodegradability. In order to make the deep eutectic mixture more cost‐effective and renewable, carbohydrate derivatives were linked with deep eutectic mixtures, since, carbohydrates are the most important and widespread renewable compounds on the earth. In this work, we have used low melting mixtures comprised of carbohydrates to create the reaction media for organic transformations. The physical properties such as density, viscosity, acidity, refractive index, surface tension, solubility, glass transition temperature, thermal stability, solvent polarity, and toxicity of the mixture were studied. Low melting mixtures were used as reaction media and catalysts for the effective synthesis of Barbiturates. The reaction between aldehydes and barbituric acid/thiobarbituric acid, and the reaction between aldehydes, barbituric acid/thiobarbituric acid, and malononitrile/dimedone were performed effectively with good to excellent yields. The recyclability of the catalyst/solvent was also established.

Features of Glass Plate Hardening by the Ion Exchange Method

In this work various methods of glass plate hardening are considered. These plates are used to protect defense devices. As a glass was used system R2O-B2O3-SiO2. The method of thermal hardening was considered. Technological disadvantages of this method were discovered by analyzing Newton's rings and a polarizing plate. The use of chemical hardening has shown its advantages over the thermal method. The essence of the method is the ion exchange of alkali metals between glass plates and the chemical mixture melt. The operating principle of the chemical hardening equipment and its technology were considered. As a result, hardened glass plates with preservation of planar geometry were obtained.

Solvent-Free UV Polymerization of n-Octadecyl Acrylate in Butyl Rubber: A Simple Way to Produce Tough and Smart Polymeric Materials at Ambient Temperature.

One of the most fascinating challenges in recent years has been to produce mechanically robust and tough polymers with smart functions such as self-healing and shape-memory behavior. Here, we report a simple and versatile strategy for the preparation of a highly tough and highly stretchable interconnected interpenetrating polymer network (c-IPN) based on butyl rubber (IIR) and poly(n-octadecyl acrylate) (PC18A) with thermally induced healing and shape-memory functions. Solvent-free UV polymerization of n-octadecyl acrylate (C18A) at 30 ± 2 °C in the presence of IIR leads to IIR/PC18A c-IPNs with sea-island or co-continuous morphologies depending on their IIR contents. The lamellar crystals with a melting temperature Tm of 51-52 °C formed by side-by-side packed octadecyl (C18) side chains are responsible for more than 99% of effective cross-links in c-IPNs, the rest being hydrophobic associations and chemical cross-links. The c-IPNs exhibit varying stiffness (9-34 MPa), stretchability (72-740%), and a significantly higher toughness (1.9-12 MJ·m-3) than their components, which can be tuned by changing the IIR/PC18A weight ratio. The properties of c-IPNs could also be tuned by incorporating a second, noncrystallizable hydrophobic monomer, namely, lauryl methacrylate (C12M), in the melt mixture. We show that the lamellar clusters acting as sacrificial bonds break at the yield point by dissipation of energy, while the ductile amorphous continuous phase keeps the structure together, leading to the toughness improvement of c-IPNs. They exhibit a two-step healing process with >90% healing efficiency with respect to the modulus and a complete shape-recovery ratio induced by heating above Tm of alkyl crystals. The temperature-induced healing occurs via a quick step where C18 bridges form between the damaged surfaces followed by a slow step controlled by the interdiffusion of C18A segments in the bulk. We also show that the strategy developed here is suitable for a variety of rubbers and n-alkyl (meth)acrylates of various side-chain lengths.

Neutron-diffraction study of the cubic-tetragonal phase structural transition in the single crystals of the solid solutions of zirconium and yttrium oxides

Objectives. The determination of the phase relations, crystallographic characteristics, microstructure features, and atomic crystal structure of zirconium oxide crystals that are partially and completely stabilized by yttrium oxide additives, and the identification of the crystallographic and crystal-chemical correlations with the physicochemical properties of single crystals.Methods. The neutron structure of the crystals was studied using the neutron time-of-flight and constant wavelength methods using a high-resolution Fourier diffractometer on the IBR-2 pulsed fast reactor and a four-circle neutron diffractometer “Syntex.” Single crystals were grown by directed crystallization from the melts of mixtures (1 − х)ZrO2 ∙хY2O3 , х = 0.03 and х = 0.12 with different growth rates (10 and 40 mm/h).Results. It was observed that when growing single crystals with x = 0.03–0.05, the crystal was stratified into cubic and tetragonal phases, and the ratio between the phases depended on the growth rate. At a growth rate of 40 mm/h, the content of the cubic phase was insignificant. In the crystals of partially stabilized zirconium dioxide (ZrO2) with the additions of 3 mol % Y2O3, the coherent coexistence of cubic and tetragonal phases was established, and the twin law for a tetragonal component (rotation of unit cell axis by 90° around the a (b) axis) that was observed during the phase transition from high-temperature cubic phase to tetragonal phase was determined. For the fully stabilized zirconium oxide of the cubic symmetry (with 12 mol % Y2O3), the 0.3 Å displacements of oxygen atoms from their partial structural positions in the directions [100] and [111] were determined. These displacements correlated with the directions of the ion transport.Conclusions. Previous studies have shown that the ratio between the cubic and tetragonal phases of the single crystals of the ZrO2 –Y2O3 system depends on the growth rate of the single crystals. The content of Y2O3 in the cubic and tetragonal phases of a single crystal was determined using the non-destructive neutronography method on the same volume sample of a solid solution of this system. Moreover, the displacements of oxygen atoms from the main position of the crystal were determined.

The Double and Triple Role of L-(+)-tartaric Acid and Dimethyl Urea: A Prevailing Green Approach in Organic Synthesis

The deep eutectic mixtures (DESs), introduced as a novel alternative to usual volatile organic solvents for organic transformations, have attracted tremendous attention of the research community because of their low cost, negligible vapour pressure, low toxicity, biodegradability, recyclability, insensitivity towards moisture, and ready availability from bulk renewable resources. Although the low melting mixture of dimethyl urea (DMU)/L-(+)- tartaric acid (TA) is still in infancy, it is very effective as it plays multiple roles such as solvent, catalyst and/or reagent in the same pot for many crucial organic transformations. These unique properties of the DMU/TA mixture prompted us to provide a quick overview of where the field stands presently and where it might be going in the near future. To our best knowledge, no review dealing with the applications of a low melting mixture of DMU/TA appeared in the literature except the one published in 2017, describing only the chemistry of indole systems. Therefore, we intended to reveal the developments of this versatile, low melting mixture in the modern organic synthesis since its first report in 2011 by Köenig’s team to date. Hopefully, the present review article will be useful to the researcher working not only in the arena of synthetic organic chemistry but also to the scientists working in other branches of science and technology.

Compositional control on impact crater formation on mid-sized planetary bodies: Dawn at Ceres and Vesta, Cassini at Saturn

High-resolution mapping of Ceres, Vesta and the icy satellites of Saturn, Uranus and Pluto reveals a rich variety of well-preserved impact crater morphologies on these low gravity bodies. These objects provide a natural laboratory to study effects of composition on crater formation processes under similar surface gravity conditions (though mean impact velocities vary by several factors). Simple craters occur on all these bodies but subtle differences in morphology on Ceres and Vesta are recognized. Immature complex craters (with large floor mounds but not terraces or conical central peaks) occur on Vesta and while smaller than predicted are consistent with its silicate composition. Asymmetric simple craters (with incomplete scarp development) on all bodies are likely related to differential overburden stresses in the rim, and their occurrence is consistent with lower crustal strength on icy bodies including Ceres. Immature and mature complex craters exhibit increasing degrees of complexity, including spiral floor deformation patterns (related to failure in converging floor material), central peaks, and impact melt. Cerean crater morphologic types and simple-complex transition diameters are smaller than on Vesta but similar to those on icy satellites, indicating a much weaker rheology for Ceres' outer layers under impact conditions. These are consistent with geophysical indications of a low-density water ice and probably clathrate rich outer shell. Fluidized floor deposits (impact melt or melt-solid mixtures) are significant in craters >25 km across on Ceres but absent on Saturn satellites. Central pit craters are common on Ceres (at diameters of ~75 to 150 km consistent with gravity scaling from the larger Galilean satellites) but are absent on Saturnian satellites and Charon. The contrasting impact melt and central pit behaviors on Ceres and Saturn's moons is contrary to expectation given the higher impact velocities at Saturn but might be related to lower internal temperatures, or the higher fraction of non-ice material on Ceres. The correlation or scaling of transition diameters to surface gravity is near −0.65 rather than −1, perhaps due to increased porosity on lower gravity bodies. The fundamental similarity of crater morphologies on Ceres and icy satellites, however, indicates that the weaker rheology of water ice results in similar craters even if the non-(ice+clathrate) components are as high as ~30 vol%.

Tracing the isotopic signatures of cryospheric water and establishing the altitude effect in Central Himalayas: A tool for cryospheric water partitioning

This study focuses on the isotopic characterization of cryospheric water and quantification of different components contributing to Alaknanda River (major tributary of the Ganges River system) at its place of origin near snout of the Satopanth Glacier. A detailed understanding of various sources/flow components contributing to the river is useful for water resource management under changing climate scenario and helpful in risk assessment due to natural hazards in the headwater catchments, Extensive fieldwork was conducted, and water samples were collected from the river, snow, glacial ice, rain, lakes, and supraglacial channels of Satopanth Glacier Basin during the ablation period of 2017 and analysed for δ18O, δ2H, and 3H along with electrical conductivity. The results helped to establish the spatio-temporal and altitudinal variability in isotopic signatures of rain, snow, and ice in Satopanth Glacier Basin. The altitudinal effect in δ18O of pre-monsoon and monsoon rainfall is −0.13‰ and −0.41‰ per 100 m rise in elevation, respectively. Snow samples show depleting isotopic trend with an altitude effect of −0.43‰ in δ18O per 100 m rise in altitude. However, snowpack samples show an enrichment with time indicating post-depositional isotopic fractionation. The contrasting isotopic gradient in debris covered and non-debris covered ice are −0.9‰ and +3.4‰ per 100 m rise in elevation, respectively. These results divulge the spatial as well as temporal variation in cryospheric waters and these variations are used to derive the isotopic signatures of snow melt, glacier melt, and rain water. The results of hydrograph separation show that the snow melt, ice melt and rain water contribute about 33%, 49% and 18% respectively, to the discharge of Alaknanda River during the ablation period. Tracer based hydrograph separation indicates that the snow melt contribution dominates in river discharge during the initial ablation period. River discharge is a mixture of snow melt, glacier melt and rain water during July and August, while there is a dominance of glacier melt during end of the ablation period. The results of the present study highlight the importance of accounting the spatial and temporal variability in tracer signatures of cryospheric water for quantifying the contributions of snow and ice melt in a river originating from glacerised area.

An expeditious and highly efficient synthesis of substituted pyrroles using a low melting deep eutectic mixture.

An expeditious green method for the synthesis of diverse valued substituted pyrroles through a Paal-Knorr condensation reaction, using a variety of amines and 2,5-hexanedione/2,5-dimethoxytetrahydrofuran in the presence of a low melting mixture of N,N'-dimethylurea and L-(+)-tartaric acid (which acts as a dual catalyst/solvent system), has fruitfully been revealed. Herein, we have disclosed the applicability of this simple yet effective strategy for the generation of mono- and dipyrroles in good to excellent yields. Moreover, C3-symmetric tripyrrolo-truxene derivatives have also been assembled by means of cyclotrimerization, Paal-Knorr and Clauson-Kaas reactions as crucial steps. Interestingly, the melting mixture was recovered and reused with only a gradual decrease in the catalytic activity (over four cycles) without any significant drop in the yield of the product. This particular methodology is simple, rapid, environmental friendly, and high yielding for the generation of a variety of pyrroles. To the best of our knowledge, the present work reveals the fastest greener method reported up to this date for the construction of substituted pyrroles by utilizing the Paal-Knorr synthetic protocol, achieving impressive yields under operationally simple reaction conditions without involving any precarious/dangerous catalysts or unsafe volatile organic solvents.

The Birth of a Hawaiian Fissure Eruption

AbstractMost basaltic explosive eruptions intensify abruptly, allowing little time to document processes at the start of eruption. One opportunity came with the initiation of activity from fissure 8 (F8) during the 2018 eruption on the lower East Rift Zone of Kīlauea, Hawaii. F8 erupted in four episodes. We recorded 28 min of high‐definition video during a 51‐min period, capturing the onset of the second episode on 5 May. From the videos, we were able to analyze the following in‐flight parameters: frequency and duration of explosions; ejecta heights; pyroclast exit velocities; in‐flight total mass and estimated mass eruption rates; and the in‐flight total grain size distributions. The videos record a transition from initial pulsating outgassing, via spaced, but increasingly rapid, discrete explosions, to quasisustained, unsteady fountaining. This transition accompanied waxing intensity (mass flux) of the F8 eruption. We infer that all activity was driven by a combination of the ascent of a coupled mixture of small bubbles and melt, and the buoyant rise of decoupled gas slugs and/or pockets. The balance between these two types of concurrent flow determined the exact form of the eruptive activity at any point in time, and changes to their relative contributions drove the transition we observed at early F8. Qualitative observations of other Hawaiian fountains at Kīlauea suggest that this physical model may apply more generally. This study demonstrates the value of in‐flight parameters derived from high‐resolution videos, which offer a rapid and highly time‐sensitive alternative to measurements based on sampling of deposits posteruption.

Signatures of continuous hexatic-liquid transition in two-dimensional melting.

Recent studies have shown that the melting of two-dimensional crystals can be either continuous or discontinuous, relying on multiple parameters such as particle stiffness, density, and particle size dispersity. However, what determines the continuity or discontinuity of the two-dimensional melting remains elusive. Here we study the two-dimensional melting of binary mixtures of soft-core particles. The two particle species are different in either particle size or particle stiffness. Starting with the mono-component systems which exhibit discontinuous hexatic-liquid transition, we gradually increase the particle size or stiffness dispersity and find that the hexatic-liquid coexistent region shrinks and eventually vanishes above a critical dispersity. Therefore, the growth of disorder caused by the particle size or stiffness dispersity leads to the discontinuous-continuous transition of the two-dimensional melting. We further find that as long as the melting is continuous the defect concentrations on the boundary between hexatic and liquid phases remain almost constant, accompanied by an almost constant correlation length. These characteristic defect concentrations and correlation length are universal and independent of particle interactions, temperature, and type of particle dispersity, which act as signatures of the continuous two-dimensional melting.

Mayenite-based electride C12A7e−: an innovative synthetic method via plasma arc melting

The plasma arc melting of mixtures of oxygen-mayenite and solid-reductants (aluminum and graphite) enables the scalable synthesis of mayenite-based electrides with treatment times below one minute.

A catalytic and solvent-free approach for the synthesis of diverse functionalized dipyrromethanes (DPMs) and calix[4]pyrroles (C4Ps)

A catalytic and solvent-free method utilizing a low melting mixture of DMU:l-(+)-TA (7:3) at 70 oC has been developed and described in detail for the construction of diverse functionalized DPMs and C4Ps under mild reaction conditions.

Sustainable multicomponent one pot synthesis of pyranopyrazole derivatives in the presence of Lactic acid: Urea: NH4Cl

Owing to the importance of pyranopyrazole scaffolds, several methods for their synthesis were developed. The previous reports on the synthesis of pyranopyrazole derivatives suffered many drawbacks which included difficulty in the workup, longer reaction time, high cost of catalyst and use of organic solvents. The present article reports the use of low melting mixture as a catalyst and solvent for the synthesis of pyranopyrazole derivatives. A study on the physical properties of the new Lactic Acid: Urea: NH4Cl low melting mixture such as density, viscosity, acidity, refractive index, surface tension is reported. IR spectra, 1H NMR spectra, emission spectra, polarity and cytotoxicity were also studied. The application in the synthesis of pyranopyrazole derivatives was established. The present method of synthesis of pyranopyrazole derivatives followed a simple procedure and easy workup protocol. The reaction was performed without the use of organic solvents. The components used in the mixture were easily available. The reaction required only less time and reactions were done at 28 ​°C.