Eutectic Melt Research Articles

Eutectic binary phase diagram and kinetically stable homogeneous co-amorphous mixtures of two imidazole drugs

Amorphous multicomponent formulations allow improving the solubility and thus the bioavailability of active pharmaceutical ingredients (APIs) that are poorly soluble in water, provided that the molecular mobility in such formulations does not promote crystallization in the amorphous (glassy) state during their shelf life. Multicomponent formulations may involve a single API mixed with excipients, but also two mutually compatible APIs. Here, we describe kinetically stable amorphous binary mixtures of two commercial antifungal imidazole APIs, bifonazole and clotrimazole, which have similar melting points and glass transition temperatures. The equilibrium phase diagram of this binary system, as determined by differential scanning calorimetry, follows the Schroeder-van Laar-LeChatelier predictions, as typically found for compounds that are miscible as liquids but immiscible in the crystalline form, and is characterized by an experimental eutectic composition close to equimolar composition (xbifonazole = 0.45) and eutectic melting point Te = 392 K. The glass transition temperature Tg varies linearly with composition, as found in ideal liquid mixtures. Dielectric spectroscopy characterization is carried out to investigate the relaxation dynamics of each amorphous API separately, and of the amorphous mixtures (both in the supercooled liquid and glass state). A single structural α relaxation is observed in all supercooled liquid mixtures, confirming their homogeneity. Both pure amorphous APIs display conformational secondary relaxations: the one of bifonazole stems from the torsional rotation of the imidazole ring; the one of clotrimazole is significantly slower than that of bifonazole, and is related to small-angle librations of the imidazole and chlorobenzene rings. Conformational relaxation processes are observed also in binary mixtures, which display also a Johari-Goldstein relaxation as pure clotrimazole. Despite the presence of both primary and secondary relaxations, the binary mixtures are observed to remain amorphous for at least twelve months both at Tg and slightly above it.

Constraining the Thickness of the Conductive Portion of Europa's Ice Shell Using Sparse Radar Echoes

AbstractIce penetrating radar sounding is the primary geophysical technique for imaging the subsurface of planetary ice shells and has the potential to directly detect the ice–ocean interface. However, many sounding measurements may lack laterally extensive features that would aid their physical interpretation. In this scenario, the detection of sparse echoes can also provide rich information on ice shell properties. To explore and demonstrate this possibility, we consider three cases of isolated radar signatures: pore‐curing, eutectic melt, and unattributed echoes. We show that through detection of unattributed sparse echoes, the thickness of the conductive portion of Europa's ice shell can be constrained. These constraints can be improved by attributing sparse echoes to thermally diagnostic signatures such as pore‐curing and eutectic melt. Notably, this approach to radar sounding echo analysis is particularly compatible with joint inversions with other planetary geophysical observations such as tidal deformation, magnetic induction, and rotation state.

Fabrication of α-W and β-W Films By Using CsF–CsCl–WO3 Molten Salt: Effect of Oxygen Contents in W Films

Electrodeposition of W films in CsF–CsCl eutectic melts was investigated after adding 2.0 mol% of WO3 at 773–973 K. The oxygen content in W films electrodeposited at various temperatures was analyzed using inert gas fusion and non-dispersive infrared spectroscopy (NDIR). Oxygen contents in the W films gradually decreased from 6.65 at% to 0.24 at% as the bath temperature increased from 773 K to 923 K along with the crystal phase change from β-W to α-W, confirmed by X-ray diffractometry (XRD). Then, vacuum annealing treatment was performed for the electrodeposited β-W films. The crystal phase was transformed to pure α-W after annealing at 973 K for 3 h and the oxygen content in W films decreased from 1.82 at% to 0.38 at%. Finally, based on the above findings, we provide a promising two-step method for preparing mirror-like and dense α-W films.

SnS2 Nanoparticles Embedded in BiVO4 Surfaces via Eutectic Decomposition for Enhanced Performance in Photoelectrochemical Water Splitting.

BiVO4 has garnered substantial interest as a promising photoanode material for photoelectrochemical water-splitting due to its narrow band gap and appropriate band edge positions for water oxidation. Nevertheless, its practical use has been impeded by poor charge transport and sluggish water oxidation kinetics. Here, a hybrid composite photoanode is fabricated by uniformly embedding SnS2 nanoparticles near the surface of a BiVO4 thin film, creating a type II heterostructure with strong interactions between the nanoparticles and the film for efficient charge separation. This structure forms via eutectic melting during atomic layer deposition of SnS2 with subsequent phase separation between SnS2 and BiVO4 at room temperature, offering greater advantages and flexibilities over conventional exsolution techniques. Furthermore, the SnS2/BiVO4 hybrid composite is coated with a thin amorphous ZnS passivation layer to accelerate charge transfer process and enhance long-term stability. The optimized BiVO4/SnS2/ZnS photoanode exhibits a photocurrent density of 5.44mAcm-2 at 1.23V versus RHE, which is 2.73 times higher than that of the BiVO4 photoanode, and a dramatic improvement in photostability retention at 1.23V versus RHE, increasing from 55% to 91% over 24 hours. This method of anchoring nanoparticles onto host materials proves highly valuable for energy and environmental applications.

Morphology Control of Nanoporous Gold Through Selective Dissolution of Au–Ge Eutectic Microstructures

The synthesis of nanoporous gold (np‐Au) through the conventional method of dealloying a more reactive element from AuTherma alloys has been extensively studied and applied in various fields, particularly catalysis. Herein, a novel approach to creating droplet‐like np‐Au through the selective dissolution of Au–Ge eutectic microstructures is explored. This work reveals that adjusting the undercooling of the eutectic melt during solidification allows for the tuning of pore and ligament sizes. It is demonstrated that this undercooling can be modified, either directly or indirectly, by adjusting either the cooling rate or the heterogeneous nucleation site density of the eutectic melt. The findings, aligned with the model based on classical theory for eutectic solidification, elucidate the connection between the tuning of pore and ligament sizes in the eutectic microstructure and the undercooling of the eutectic melt. Importantly, it is established that this phenomenon is applicable across a variety of compositions, including hypereutectic, eutectic, and hypoeutectic. The ability to regulate pore and ligament size in single crystals of np‐Au droplets offers a novel approach to synthesizing catalytic np‐Au crystals with enhanced mechanical and thermal stability compared to conventional methods.

High‐Pressure Melting Experiments of Fe3C and a Thermodynamic Model of Fe‐C Liquids for the Earth's Core

AbstractMelting experiments of Fe3C were conducted to 85 GPa in laser‐heated diamond anvil cells with in situ X‐ray diffraction and post‐experiment textural observation. From the determined pressure‐temperature conditions of the melting curve for Fe3C, together with literature data on the melting point of diamond and eutectic point of the system Fe‐Fe3C/Fe7C3 under high pressures, we established a self‐consistent thermodynamic model for high‐pressure melting of the system Fe‐C including the mixing parameters for liquids. The results show that mixing of Fe and C liquids is negatively nonideal from 1 bar to the pressure at the center of the Earth. The departure from ideal mixing becomes progressively larger with increasing pressure, which leads to greatly stabilized liquids under core pressures. The modeled carbon content in eutectic melts under core pressures is 3.3–4.4 wt%. From the Gibbs free energy, we derived an internally consistent parameters for Fe‐C outer cores which included the crystallizing points at their bottoms, isentropic thermal profiles, and densities and longitudinal seismic wave speeds (Vp). While the addition of carbon in excess of the eutectic melt composition effectively reduces the density of iron liquid, the Vp of iron liquid is not greatly changed. Therefore, the low density and high Vp of PREM relative to pure iron cannot be reconciled by an Fe‐C liquid. Therefore, the Earth's core cannot be approximated by the system Fe‐C and should include another light element.

From low-cost mineral to high-performance Li4SiO4 for solar energy storage and CO2 capture

The huge consumption of fossil fuels results in excessive CO2 emissions and its reduction has become a common concern. The combination of renewable energies (i.e., solar energy) and carbon capture, utilization, and sequestration are well recognized as two major routes to achieving carbon neutrality. Lithium orthosilicate (Li4SiO4) has been identified as one of the most promising candidates for solar energy storage and CO2 capture. However, the cost reduction and performance enhancement remain to be the main obstacles for its practical application. In this work, high-performance Li4SiO4 heat carriers have been synthesized using low-cost mineral as silicon source for solar energy storage and CO2 capture. Li4SiO4 derived from diatomite exhibited cyclic energy storage densities above 500 kJ/kg. The performance was further improved by doping alkali carbonates, particularly doping 3 wt% K2CO3 (LD-P-3K), which exhibited high and stable energy storage density of approximately 700 kJ/kg in the tested 10 cycles. Then, the mechanism of alkali doping was revealed through experiments and DFT calculations. The DSC results demonstrated that the improved performance was attributed to the formation of a eutectic melt which reduced the CO2 diffusion resistance. The DFT calculations showed that K-doped Li4SiO4 had lower adsorption energy and more significant charge migration, which meant stronger interaction. Additionally, diatomite-derived Li4SiO4 material is also a promising candidate for high-temperature CO2 capture, evidenced by its relatively high cyclic CO2 capture capacity (∼0.25 g/g). In general, satisfactory density/capacity and stability endows diatomite-derived Li4SiO4 with great prospects for both thermochemical energy storage and high-temperature CO2 capture.

Electrochemical Identification of Metal Chlorides in Eutectic LiCl-KCl Without Prior Knowledge of Analyte Identities

The identities of unknown analytes within four eutectic LiCl-KCl melts were determined using electrochemical methods, simulating the uncertainty of electrochemically probing an electrorefiner salt bath or molten salt nuclear reactor. With a variety of electrochemical methods (e.g. cyclic voltammetry, chronopotentiometry, and square-wave voltammetry), and electroanalytical techniques (e.g. semi-differentiation), every analyte was positively identified, although one false positive occurred because of an unexpected chemical interaction. This study highlights some remaining challenges for the use of electrochemical sensors in nuclear material control and accountability in molten salts: (1) quantification of analytes without the use of calibration curves (e.g. error in property values, such as diffusion coefficient) and (2) additional and interfering electrochemical signals due to interaction and alloying of multiple species.

Separation of uranium from lanthanides (La, Ce, Nd) and purification of waste salt via aluminum electrodes with different structures in LiCl-KCl eutectic

Aluminum is an ideal cathode material for the pyrochemical reprocessing of spent nuclear fuels. However, there is a lack of large-scale experiments to further assess its performance. Here we designed several Al electrodes with sheet, rod, and porous morphologies, and employed them in separating actinides (An) from lanthanides (Ln) and purifying the waste salts in about 500 g of LiCl-KCl eutectic melt at 773 K. By applying a constant potential of −1.2 V vs. Ag/AgCl, U can be separated from Ln (La, Ce, and Nd) by forming Al-U alloys consisting of Al3U and Al4U with high separation factors and current efficiency. Among all Al electrodes used in our experiments, the porous-shaped ones show the fastest electrochemical reaction rate, and hence only 56 h were required to achieve the separation. Subsequently, the purification of the waste salts from U-Ln separation was conducted via constant potential electrolysis at −1.5 V vs. Ag/AgCl on porous-shaped Al electrodes. About 99.9 % of Ln was extracted via forming Al-Ln alloys, leaving a purified electrolyte that can be reused. In all, about 17 g of U metals and 1 kg of waste salts were successfully reprocessed in our large-scale experiments, which envisions the feasibility of applying Al electrodes in engineering-scale pyrochemical reprocessing.

Synthesis and characterizations of random copolyamide PA(56-co-66): Excellent toughness and transparency

Random copolyamides PA(56-co-66) (coPA-n) with various comonomer compositions were synthesized by a one-pot polycondensation reaction of pentamethyleneammonium adipate (PMA) salt and hexamethyleneammonium adipate (HMA) salt in aqueous solution. All copolymers have high Mn (≥15000 g/mol). The molecular segment composition can be regulated by controlling the feed ratio of PMA salt and HMA salt. Tc and Tm of copolymers obtained by nonisothermal crystallization depend on the composition, showing a clear pseudo-eutectic behavior. Copolyamide coPA-50 exhibits a eutectic phenomenon with the melting point decreasing to a minimum of 218.9 °C. WAXD and SAXS results confirm that the crystalline structure of the copolyamides follows that of the rich component, exhibiting a typical isodimorphic characteristic. Mechanical properties of the copolyamides indicate that the elongation at break could be improved significantly with slight sacrifice of strength, which provides a promising approach for fabricating polyamide materials with desired properties. The tensile strength, tensile modulus, and elongation at break of coPA-50 was 65.2 MPa, 1.0 GPa, and 758.1 %, respectively. These copolymers can be melt-spun into fibers with excellent mechanical properties. Especially, the transmittance of coPA-60 reaches a high value of 88.01 % due to its low crystallinity and small crystal size.

Binary wax oleogels: Improving physical properties and oxidation stability through substitution of carnauba wax with beeswax.

High concentrations of carnauba waxes (CRWs) that can compromise organoleptic properties are required to create self-sustained and functional oleogels. The weak physical properties and stability of 4% w/w CRW-rice bran oil (RBO) oleogel were addressed by substituting CRW with beeswax (BW) in different weight ratios. The texture profile analyzer revealed that substituting only 10% (weight ratio) of CRW with BW improved the hardness compared to the mono-CRW oleogel. The hardness of binary oleogels increased gradually as the proportion of BW increased. At a BW ratio of 70% or more, the hardness was three times higher than that of mono-BW oleogel. Rheology analysis showed the same trend as the large deformation test; however, the hardest binary oleogels had lower critical strain and yield point compared to the mono-wax oleogels, implying that they are more prone to lose their structure upon applied stress. Nevertheless, nearly all binary mixtures (except for 10%BW90%CRW) showed oil-binding capacities above 99%, suggesting improved nucleation and crystallization process. Polarized light microscopy showed the coexistence of BW and CRW crystals and changes in the size and arrangement of wax crystals upon proportional changes of the two waxes. X-ray diffraction confirmed no differences in the peaks' location, and all oleogels had β' polymorphism. Differential scanning calorimetry showed eutectic melting behavior in some binary blends. Oxidation stability in the binary wax oleogels improved as compared to the mono-wax oleogel and bulk RBO. BW and CRW mixtures have promising oil-structuring abilities and have various properties at different ratios that have the potential to be used as solid fat substitutes. PRACTICAL APPLICATION: As a trending green oil-structuring technology, oleogelation has shown great potential to reduce saturated fats in food systems. The current research provides valuable fundamental information on the strong synergistic interactions between beeswax and carnauba wax that have the potential to be used as solid fat substitutes created with a much lower total concentration of the required wax. This will help create wax oleogels with better organoleptic properties and less negative waxy mouthfeel. Such knowledge could prove beneficial for the development of healthy products that have potential applications in meat, bakery, dairy, pharmaceutical, as well as cosmetic industries.

The Effect of Zr and Li on the Microstructure of AlMg5Si2Mn-Type Casting Alloys

AbstractIn the article, the authors present results of microstructural studies of Al-Mg-Si-Mn casting alloys with Zr, Li, and TiB2 additions on a broad scale. Zirconium content was set on two levels: 0.34 and 1.58 wt%, and Li was set 1.2 and 2.0 wt%. It was found that the addition of Zr shifts the eutectic melting temperature to a higher level, up to 611.3 °C at 1.6 wt% Zr. At the same time, Li addition leads to the depression of eutectic melting temperature: down to 587.2 °C at 2.0 wt% Li, what is a common effect of eutectic modification which was confirmed by means of structural examinations. The complex addition of Li and AlTi5B1 resulted in a eutectic melting temperature close to the equilibrium eutectic temperature for the Al-Mg-Si system (596.2 °C). The grain refinement effect of Zr is due to the nucleation of α-Al on the Zr(Al1−x, Six)3 phase. Crystals of this phase were detected in the grain centers of Zr-containing alloys. The Li addition does not affect α-Al grain size but changes the morphology of eutectic colonies from petal-like to fibrous. Observation of TiB2 particles inside the primary Mg2Si crystals gives direct experimental confirmation of nucleation of the primary phase on the surface of TiB2 in the alloy after adding Li and AlTi5B1. Natural aging of the alloys resulted in the formation of fine precipitates detected close to dislocations. The most apparent supposition is that the mechanism responsible for their formation is heterogeneous nucleation in the stress field of dislocations. Hardness tests showed adding 2.0 wt% of Li is very effective, increasing hardness up to 113 HV0.2 in naturally aged condition, which is nearly double that of commercial Al-Mg-Si die-casting alloy. Several effects were proposed which may synergistically contribute to the rise of hardness in Li-containing alloys, such as solid solution strengthening, formation of primary LiAlSi phase and natural aging.

Early-phase core degradation interpretation by interaction between fuel cladding and fuel components in Fukushima Daiichi nuclear power plant Unit 2

ABSTRACT The early phase of the core degradation at the Fukushima Daiichi Nuclear Power Station Unit 2 was investigated in terms of a fuel-component degradation by materials interaction by carrying out the accident analysis, evaluation of chemical conditions and experimental works. First, the accident scenario was evaluated to specify a target period (from 18:40 to 22:40 on NaN Invalid Date NaN), and then the temperature and H2/H2O pressure ratio in the core region during this period were calculated based on plant parameters. Subsequently, semi-integral experiments were performed using the mocked-up fuel components of a boiling water reactor (BWR). Furthermore, separate-effects tests using Ni-alloy/Zircaloy4 were also performed to understand the phenomenon observed in the semi-integral experiments, where the Ni-Zr reaction occurred even with the oxide layer on the Zr-based alloy. Consequently, it was estimated that the Zr-Ni eutectic melting reaction above 1100°C under steam-starved conditions resulted in a fuel failure at 19:08, melting of spacer locations at 19:37, and upper-tie-plate at 21:26. The first and second degradations could have caused the release of radioactive elements or particles leading to the neutron detection at 21:00 in front of the main gate, and the third degradation could have resulted in the separation of the upper-tie-plate.

Structural correlation and chemistry of molten NaF–ScF3 with dissolved metal aluminium: TG/DTA, XRD, NMR and molecular dynamics simulations

For the first time, the mechanism of metal aluminum dissolution in NaF–ScF3 eutectic melts and the chemical interaction between the constituents of this mixture have been thoroughly studied by a combination of differential thermal analysis (DTA), high temperature and solid-state nuclear magnetic resonance (NMR), and X-ray diffraction (XRD) coupled with the molecular dynamic simulations. The formation of an insoluble Al3Sc alloy in molten (NaF–ScF3)eut system was proven, and the chemical mechanism of this aluminothermic Al3Sc alloy production was elucidated. Corresponding ex situ examinations bring to light the formation of NaScF4 and solid solution of Na3(Al,Sc)F6 in cooled bath. The molecular dynamics calculations of the bath allow us to construct the structural model and to predict viscosity, density and electrical conductivity of the reagent melt to help to optimize the conditions of the alloy synthesis.Graphical abstract

Thermal conductivity of lead and bismuth-lead eutectic melts up to 1300 K

Using a laser flash method, the thermal conductivity (λ) of Pb and eutectic alloy Bi-Pb (55.2 wt%Bi) melts is measured in the temperature range from the melting point to 1300 K with 3.2–6.0 % uncertainty. The results are compared with the data of other authors. Based on the measurements, the thermal diffusivity (a) and the Lorenz number of melts are calculated. Tables of recommended data for a and λ along with estimated errors are drawn up.

Permeation Tendency of Rare-earth Elements through a Ni-based Alloy Diaphragm in LiCl–KCl Eutectic Melts

Permeation Tendency of Rare-earth Elements through a Ni-based Alloy Diaphragm in LiCl–KCl Eutectic Melts

In situ coupling metallophilic Zn sites and interfacial LiCl stabilizer to achieve one-step reversible hydrogen storage in Li/Na dual-cation borohydride

Dual-cation borohydrides composed of alkali or alkaline-earth metals attract considerable attention for hydrogen storage, thanks to their high hydrogen capacity and low eutectic melt point; however, they still suffer from high-temperature-dependent dehydrogenation and poor reversibility. In-situ catalyzation and nanoconfinemnt are effective for easing these problems, but a simple and efficient method is required to achieve their coulping. Here inspired from the structural stabilization and performance improvement roles on anodes of metal batteries by constructing metallophilic Zn sites and interfacial LiCl layers, we develop a 0.62LiBH4-0.38NaBH4 system with ZnCl2 as reactive additives by one-step ball milling. In-situ evolved LiCl and Zn(BH4)2 are surprisingly identified as interfacial stabilizers and metastable phases to disperse borohydride particles and to trigger hydrogen release below 100 °C, respectively. Further formed Zn from the decomposition of Zn(BH4)2 acts as catalytic nucleation sites to promote the one-step and reversible (de)hydrogenation of LiBH4 and NaBH4, without producing high chemical potential intermediates, benefiting from the strong affinity of Zn towards Li and Na. These factors contribute to a cyclic stability of nearly 70 %, the highest for dual-cation borohydrides reported so far. The present work provides new insights and a feasible scheme for developing promising borohydride-based storage systems towards practical application.

Environmental stability of a uranium-plutonium-carbide phase

A plutonium-rich carbide, (U,Pu)(Al,Fe)3C3, was discovered in a hot particle from the Maralinga nuclear testing site in South Australia. The particle was produced between 1960 and 1963 and has been exposed to ambient conditions since then. The new phase belongs to a group of ternary carbides known as 'derivative-MAX phases'. It formed at high temperature within an explosion cloud via rapid eutectic crystallisation from a complex Al–Fe–U–Pu–C–O melt, and is the major Pu host in this particle. Despite signs of volume expansion due to radiation damage, (U,Pu)(Al,Fe)3C3 remains highly X-ray crystalline 60 years after its formation, with no evidence of Pu leaching from the crystals. Our results highlight that the high-energy conditions of (sub-)critical explosions can create unexpected species. Even micro-particles of a derivative-MAX phase can effectively retain low-valence (metallic-like character) Pu under environmental conditions; the slow physical and chemical weathering of these particles may contribute to the slow release of radionuclides over decades, explaining constant low-levels of radionuclides observed in fauna. This study further suggests that rapidly quenched eutectic melts may be engineered to stabilise actinides in nuclear waste products, removing the need for hydrometallurgical processing.

Recoverable tuning of lattice mismatch and strength in ultrastable-nanostructured Cu/Ag spinodoid alloys

The strengthening effect of interface in materials is usually studied by monitoring the change of strength in response to varying structure sizes, such as the varying grain or phase sizes. In this study, we demonstrate that the strength of a nanostructured material can be recoverably tuned by modifying interfacial structure without changing structure size. Specifically, we studied the Cu/Ag spinodoid alloys fabricated by dealloying and electrochemical deposition, which exhibit a cube-on-cube orientation relationship between two interpenetrating nanophases. This material remains stable against coarsening even at temperatures near the eutectic melting point, due to the presence of low-energy semi-coherent interfaces and the lack of defects such as grain boundaries. Using cyclic thermal annealing, we are able to alter the solid solubility of both nanophases and, consequently, the lattice mismatch between them, resulting in a recoverable tuning of hardness and strength. The amplitude of hardness modulation decreases with increasing feature size (λ), and changes sign when λ exceeds ∼500 nm. This is attributed to a competition between two strengthening mechanisms: the interface-induced strengthening that is more prominent at a lower λ, and the solid solution hardening that is largely λ-insensitive. The finding indicates that interface hardening prevails over solution hardening when λ is below ∼500 nm. Current study paves the way for the development of strong and stable nanostructured materials whose properties can be optimized by independently tailoring feature sizes and interfacial structures.

Deep eutectic melt of betaine and trichloroacetic acid; its anomalous thermal behavior and green promotion effect in selective synthesis of benzimidazoles

Trichloroacetic acid and betaine form glassy liquids on melting together in some molar ratios, of which the melt with mole fraction of trichloroacetic acid about 0.83 displayed the lowest freezing point, so was detected as their deep eutectic mixture. It showed two reversible DSC effects on cooling from 70 °C to −70 °C; a normal exotherm on freezing followed by an abnormal endotherm on melting. Electric conductance of the melt against temperature exhibited two regions of deviations from a perfect exponential curve. These regions correspond to the temperatures of the two reversible phase transitions detected by DSC analysis. As another evidence in support of its freezing on heating, the kinematic viscosity of the melt is increased within the temperature range of 40–50 °C. Moreover, the FT-IR spectrum and TGA analysis of the eutectic mixture point to its exceptional nature in comparison to other mixtures of the two components. The melt proved to be an efficient promoter for selective synthesis of benzimidazoles from o-phenylenediamine and arylaldehydes at room temperature. No N-substituted derivatives of the products were resolved from the reaction mixtures.