Binary Eutectics Research Articles

SINTERING PROCESSES, PHASE AND STRUCTURE FORMATION AND PROPERTIES OF ELECTRICAL PORCELAIN WITH THE USE OF MARSHALLIT AND WOLLASTONITE ADDITIVES

The effect of marshallite upon its complete replacement of quartz and wollastonite additions (2.0 wt.%) on the sintering and phase formation processes, as well as the structure and properties of insulation porcelain was studied. The object of study is insulation porcelain of typical component composition (kaolin, soft clay, feldspar, quartz sand). It has been established that the processes of melting and sintering at firing of the investigated porcelain compositions are not equilibrial. The formation of ternary eutectics fusions of the R2O-Al2O3-SiO2 systems at temperatures of 985 and 1050 °C in amounts of 45–60% does not occur. The formation of a fusion during firing of ceramics occurs due to partial binary eutectics “white feldspar-earth silicon” and “orthoclase feldspar-earth silicon” during the interaction of feldspar with silica-containing components (990–1060 °C). This is due to the fact that primary mullite is formed at temperatures of its stable state above 1200 °C. The actual processes of fusion formation during porcelain firing are not equilibrium. Recrystallization of mullite occurs due to the dissolution of primary mullite in the fusion, followed by crystallization of acicular mullite. Replacing of quartz sand with marshallite leads to a decrease in the temperatures of earth silicon with feldspar interaction and the formation of a primary fusion, which results in a decrease in the ceramics firing temperature by 70° from 1340 to 1270 °C. The addition of wollastonite – CaSiO3 (2 %wt.) intensifies the process of primary mullite dissolution and crystallization of acicular mullite. The length of the mullite needles increases from 2–3 μm up to 7–10 μm, the mullite needles form aggregates, which provides an increase in the bending strength of porcelain by 36% up to 80 MPa. For citation: Vereshchagin V.I., Kurbanbayev M.Ye., Yessimov B.O., Root L.O., Mogilevskaya N.V. Sintering processes, phase and structure formation and properties of electrical porcelain with the use of marshallit and wollastonite additives. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 5. P. 87-98. DOI: 10.6060/ivkkt.20246705.6960.

Dual-cluster interpretation of Au–Sn binary eutectics and solders

Au–Sn alloy is an important high-temperature solder, but it has some disadvantages such as high cost and brittleness. Multicomponent alloying is often performed to improve performance and reduce their cost. However, due to the absence of an atomic structure model, there has been a lack of effective theory to guide their composition design. Since Au–Sn solders are typically eutectic-based, understanding the Au–Sn eutectic at the atomic level is of great significance for clarifying the composition origin of Au–Sn solders and the subsequent multi-component composition design. In the present work, the short-range order of Au–Sn eutectics is characterized using a dual-cluster model. In the dual-cluster formulism, the two eutectics Au69.6Sn30.3 and Sn94.6Au5.4 at. % are interpreted in terms of the hypoeutectic [SnAu12]Sn2Au3 + [Au–Au2Sn6]Au3 = Au70.0Sn30.0 and [Au–Sn8]Au1 + 2{[Sn–Sn10]Sn5} = Sn95.2Au4.8 alloys, respectively. The compositions of Au–Sn solders are then analyzed based on the interpreted dual-cluster formulas, which indicate that the number of atoms of the alloying elements that replace the atoms in the dual-cluster formulas is always an integer. The present method provides a quantitative approach toward developing a practical composition interpretation and design tool for Au–Sn-based solders.

Characterization of an Active Soldering Zn-Mg Alloy and the Study of Ultrasonic Soldering of SiC Ceramics with Copper Substrate

The aim of this study was to characterize a Zn-Mg type soldering alloy and direct soldering of SiC ceramics with a copper substrate. The Zn1.5Mg solder exerts a wider melting interval. The temperature of the eutectic reaction was 365 °C, and the liquidus temperature was 405 °C. The microstructure of the soldering alloy is comprised of a zinc matrix. Segregation of binary eutectics in the form of (Zn) + Mg2Zn11 lamellas occurred on the boundaries of Zn grains. Additionally, the presence of a MgZn2 magnesium phase was observed in the solder matrix. The SiC/solder bond was formed due to magnesium distribution from solder to the boundary with SiC ceramics, where magnesium reacts with silicon, which is infiltered in SiC ceramics. By a mutual interaction, a new Mg2Si phase is formed. An interaction between the molten zinc solder and Cu substrate occurred on the boundary of the Cu/substrate joint at the formation of a transition zone composed of two new phases, namely the γCu (Cu5Zn8) non-wettable phase type, approximately 30 µm wide, and a wettable (CuZn4) phase type ε, approximately 12 µm wide. The average shear strength of a combined SiC/Cu joint fabricated using Zn1.5Mg solder was 44 MPa.

Redox Active Organic Liquids for Energy Storage

The necessity to move to renewable energy sources has increased over the last few years. However, to ensure a good transition and effective energy supply, efficient, cheap, and green technologies are required as grid-level storage.1 Redox-Active Organic Materials (ROMs) are a fast-growing research topic in different electrochemical storage devices. Their advantageous characteristics of being formed from highly abundant elements, having a high electrochemical tunability, ease of handling and device processing, and high versatility for a variety of energy storage applications make ROMs attractive.1–3 Redox-Active Liquids (RALs) are themselves a new trend within the category of ROMs because the physical properties of organic liquids are advantageous for some storage devices.4–6 Those advantages include no requirement for materials processing after synthesis, high miscibility and/or high solubility with battery electrolytes, the ability to be used as a solvent themselves without any additional additives,4,5 and the avoidance of surface-related changes e.g., dendrites.7 RALs have been studied as mediators or active materials in the context of different applications such as supercapacitors,6,8 conventional,4,5,9 and hybrid-flow batteries.10,11 In this work, we present the synthesis and physio-chemical characterization of different RALs that can be used in such energy storage devices. The characterization results supported by computational analyses were used to investigate the correlation between the chemical structure and the electrochemical properties of the compounds. The obtained information was then further used to inform the design of further compounds with enhanced electrochemical properties.(1) Schon, T. B.; McAllister, B. T.; Li, P. F.; Seferos, D. S. The Rise of Organic Electrode Materials for Energy Storage. Chem Soc Rev 2016, 45 (22), 6345–6404. https://doi.org/10.1039/c6cs00173d.(2) Kwon, G.; Ko, Y.; Kim, Y.; Kim, K.; Kang, K. Versatile Redox-Active Organic Materials for Rechargeable Energy Storage. Acc Chem Res 2021, 54 (23), 4423–4433. https://doi.org/10.1021/acs.accounts.1c00590.(3) Lee, S.; Hong, J.; Kang, K. Redox-Active Organic Compounds for Future Sustainable Energy Storage System. Advanced Energy Materials. Wiley-VCH Verlag August 1, 2020. https://doi.org/10.1002/aenm.202001445.(4) Zhao, Y.; Zhang, J.; Agarwal, G.; Yu, Z.; Corman, R. E.; Wang, Y.; Robertson, L. A.; Shi, Z.; Doan, H. A.; Ewoldt, R. H.; Shkrob, I. A.; Assary, R. S.; Cheng, L.; Srinivasan, V.; Babinec, S. J.; Zhang, L. TEMPO Allegro: Liquid Catholyte Redoxmers for Nonaqueous Redox Flow Batteries. J Mater Chem A Mater 2021, 9 (31), 16769–16775. https://doi.org/10.1039/d1ta04297a.(5) Robertson, L.; Udin, M. A.; Shlrob, I. A.; Moore, J. S.; Zhang, L. Liquid Redoxmers for Nonaqueous Redox Flow Batteries. ChemSusChem 2023, e202300043. https://doi.org/10.1002/CSSC.202300043.(6) Fontaine, O. A Deeper Understanding of the Electron Transfer Is the Key to the Success of Biredox Ionic Liquids. Energy Storage Mater 2019, 21, 240–245. https://doi.org/10.1016/J.ENSM.2019.06.023.(7) Bao, J.; Li, C.; Zhang, F.; Wang, P.; Zhang, X.; He, P.; Zhou, H. A Liquid Anode of Lithium Biphenyl for Highly Safe Lithium-Air Battery with Hybrid Electrolyte. Batter Supercaps 2020, 3 (8), 708–712. https://doi.org/10.1002/BATT.202000092.(8) Mourad, E.; Coustan, L.; Lannelongue, P.; Zigah, D.; Mehdi, A.; Vioux, A.; Freunberger, S. A.; Favier, F.; Fontaine, O. Biredox Ionic Liquids with Solid-like Redox Density in the Liquid State for High-Energy Supercapacitors. Nature Materials 2016 16:4 2016, 16 (4), 446–453. https://doi.org/10.1038/nmat4808.(9) Chen, H.; Niu, Z.; Zhao, Y. Redox-Active Binary Eutectics: Preparation and Their Electrochemical Properties. Electrochem commun 2021, 126. https://doi.org/10.1016/j.elecom.2021.107028.(10) Shimizu, A.; Takenaka, K.; Handa, N.; Nokami, T.; Itoh, T.; Yoshida, J.-I.; Shimizu, A.; Takenaka, K.; Yoshida, J.; Handa, N.; Nokami, T.; Itoh, T. Liquid Quinones for Solvent-Free Redox Flow Batteries. Advanced Materials 2017, 29 (41), 1606592. https://doi.org/10.1002/ADMA.201606592.(11) Chen, N.; Chen, D.; Wu, J.; Lai, Y.; Chen, D. Polyethylene Glycol Modified Tetrathiafulvalene for High Energy Density Non-Aqueous Catholyte of Hybrid Redox Flow Batteries. Chemical Engineering Journal 2023, 462. https://doi.org/10.1016/j.cej.2023.141996.

Improved tableting properties of ascorbic acid via eutectic compositions with sugars

Ascorbic acid (ASC) is commonly used as an anti-oxidant and a dietary supplement due to its radical scavenging properties. The ASC chewable tablet dosage form is regularly prescribed to increase immunity among Covid-19 patients. The main drawback during tableting of ASC is its brittle nature because of interlocking packing arrangement, strong hydrogen bonding between complimentary functional groups and lack of slip planes in its crystal lattice. In order to improve the compaction properties of ASC, sugar and sugar alcohol as coformers with better tableting profile over ASC were introduced. During high throughput cocrystal screening, four eutectic compositions of ASC with glucose (GLU), mannitol (MAN), sucrose (SUC) and lactose monohydrate (LAC) were obtained in an equivalent stoichiometry. The binary eutectics (1:1) were confirmed by their lower melting endotherms compared to the individual components and overlapping of those in XRD characterization. The regular (lamellar) microstructures of the ASC-GLU and ASC-MAN eutectics and irregular (acicular or globular) microstructures of the ASC-LAC and ASC-SUC eutectics were confirmed by the optical and scanning electron microscope (SEM) images of the crystallized binary compositions. Similar to ASC, all the eutectic mixtures were proved to be non-hygroscopic at 25 ᴼC/80 % RH. The eutectics with disaccharides such as ASC-SUC and ASC-LAC improved the tensile strength (tabletibility) of ASC with lower porosity, compared to the corresponding monosaccharide eutectics (ASC-GLU/ASC-MAN). Improved compaction properties of ASC-SUC/LAC eutectics is correlated with higher inter-particulate bonding area and bonding strength.

Development and thermophysical analysis of binary eutectics phase change materials for solar drying application

Background: In the past 30–40 years, conflicts over limited conventional energy sources and the negative climate change caused by them have attracted researchers and analysts to new, clean, and green energy technologies. Thereby reducing the consumption of conventional fuel and the negative impact on the climate. The production of alternative energy in the form of thermal energy storage using phase change materials (PCMs) is one of the techniques that not only reduces the gap between the supply and demand of energy but also increases the stability of the energy supply. The tendency of PCMs to melt and solidify over a wide temperature range makes them more attractive for use in many applications. The effective and efficient storage of solar energy by PCM has the potential to significantly advance the use of renewable energy. Methods: Organic non-paraffin compound beeswax (BW) mixed with other non-paraffin compounds stearic acid (SA), Palmitic acid (PA), Myristic acid (MA), and Lauric acid (LA) in different compositions with the help of magnetic stirrer at 50–60°C for 3–4 hours to prepare BWSA, BWPA, BWMA, and BWLA eutectic PCM. Results: Prepared eutectics melt and solidify in the temperature range 36–56°C and with latent heat in the range of 155–211 kJ/Kg. Conclusions: Due to suitable temperature and good latent heat storage range, it is a good choice as thermal energy storage, for solar drying applications.

Study of Lithium-Silicon Anode Materials for Thermal Batteries

Thermal batteries are constructed from a molten salt electrolyte which is solid at room temperature, a FeS2 positive electrode and a lithium-silicon negative electrode. The typical operating temperature of the battery is between 350 to 500°C. Thermal batteries use an inorganic salt as the electrolyte such as binary or ternary alkali halide eutectics. For example, LiCl-KCl and LiF-LiCl-LiBr. At a composition of 44.8 LiCl and 55.2 KCl wt%, the melting point is around 353°C for LiCl-KCl. Molten salts have a very high electrical conductivity, so thermal batteries have a higher power density than room temperature batteries. In this work, LiCl-KCl eutectic was used for electrochemical testing. The performance of an electrode can be studied in single-cell discharge tests where a discharge profile is obtained. The tests were carried out in a cell testing rig inside an argon glovebox. The cells were made from pellets which were placed in a Swagelok casing. The cells were made from 0.15g of FeS2 mixed with 0.05g LiCl-KCl as the positive electrode, 0.2g of LiCl-KCl with 35% wt MgO as the electrolyte and 0.2g of Li13Si4 as the negative electrode. Lithium silicides were made using solid state synthesis in a tube furnace. The electrochemical tests show that the Li13Si4 is a better negative electrode material than Li7Si3 (Figure 1). In addition, powder neutron diffraction was used to probe the lithium silicides with increasing temperature. The high-temperature behaviour of Li13Si4 and Li7Si3 was studied in March 2020 by the JTSI group at the ISIS neutron source, Rutherford Appleton Laboratory, UK. The data gives information on structural changes in Li13Si4 and Li7Si3. The results indicate that Li13Si4 and Li7Si3 remain remarkably stable at 500°C. There are no phase transitions in the materials from room temperature to 500°C and the materials remain crystalline. These findings give a clearer understanding of thermal battery discharge processes. Figure 1

Microstructural verification of the theoretically designed novel eutectic multi-principal element alloy

This letter proposes the theoretical design methodology based on the proportional mixing of binary eutectics for predicting novel eutectic multi-principal element alloys (EMPEAs). It was then experimentally verified by manufacturing a dual-phase eutectic Zr61.9AlTiVCr alloy having a density of 6.04 g/cc. Zirconium was identified as the eutectic forming element in this system, notably having only 3 binary eutectics in a quinary system. The alloy developed by vacuum arc melting revealed the formation of an irregular lamellar eutectic microstructure consisting of cubic and hexagonal Laves phases. The as-cast alloy had a superior hardness of HV527, with 780 MPa compressive strength. This study paves the way for designing new EMPEAs without depending on any simulation software.

Development and thermophysical analysis of binary eutectics phase change materials for solar drying application

Background: In the past 30–40 years, conflicts over limited conventional energy sources and the negative climate change caused by them have attracted researchers and analysts to new, clean, and green energy technologies. Thereby reducing the consumption of conventional fuel and the negative impact on the climate. The production of alternative energy in the form of thermal energy storage using phase change materials (PCMs) is one of the techniques that not only reduces the gap between the supply and demand of energy but also increases the stability of the energy supply. The tendency of PCMs to melt and solidify over a wide temperature range makes them more attractive for use in many applications. The effective and efficient storage of solar energy by PCM has the potential to significantly advance the use of renewable energy. Methods: Organic non-paraffin compound beeswax (BW) mixed with other non-paraffin compounds stearic acid (SA), Palmitic acid (PA), Myristic acid (MA), and Lauric acid (LA) in different compositions with the help of magnetic stirrer at 50–60°C for 3–4 hours to prepare BWSA, BWPA, BWMA, and BWLA eutectic PCM. Results: Prepared eutectics melt and solidify in the temperature range 36–56°C and with latent heat in the range of 155–211 kJ/Kg. Conclusions: Due to suitable temperature and good latent heat storage range, it is a good choice as thermal energy storage, for solar drying applications.

Assessment of COSMO-SAC Predictions for Solid–Liquid Equilibrium in Binary Eutectic Systems

Assessment of COSMO-SAC Predictions for Solid–Liquid Equilibrium in Binary Eutectic Systems

Machine learning correlated with phenomenological mode unlocks the vast compositional space of eutectics of multi-principal element alloys

Eutectic multi-principal element alloys (MPEAs) present a vast compositional space of eutectics, providing a great potential to tailor mechanical performance. However, only limited eutectics have been determined since MPEAs were brought to light in 2014. It still remains a huge challenge to efficiently identify the eutectics. Here, we propose a novel strategy to determine eutectic compositions via phenomenological mode and machine learning, which is validated with Co-Cr-Fe-Ni-Hf/Al MPEAs. Phenomenologically, approximate eutectics can be calculated via the addition of binary eutectics when ignoring the effect of Co-Cr-Fe-Ni interaction. Then, these eutectics are quantitatively corrected by only adjusting Hf content through machine learning. A prediction accuracy higher than 90% is achieved. Noticeably, the variation of eutectic compositions significantly alters the microstructures, leading to great changes in mechanical performances. These findings can potentially pave the pathway to explore the vast compositional space of eutectics and dramatically accelerate the development of eutectic MPEAs.

Characterization and control of a new kind of black spot defects on surface of hot-dip galvanized low-aluminum Zn-1.5Al-1.1 Mg coatings

Surface defects can seriously affect the appearance and performance of Zn-Al-Mg coatings. In this work, a new kind of black spot defects on the surface of hot-dip galvanized low-aluminum Zn-1.5Al-1.1 Mg coatings were investigated. Results revealed that the microstructures of normal and black spot regions were both composed of primary Zn, Zn/MgZn2 binary eutectic (BE) and Zn/MgZn2/Al ternary eutectic (TE). This kind of black spots with a diameter of 1 μm were caused by the difference in light reflection with normal region after generating local pseudo-eutectic structures. When the solidification cooling rate was controlled to 18 °C/s, the black spot defects were completely eliminated. Furthermore, the corrosion current density was reduced to 1.2 μA/cm2 and the coating resistance increased to 2427 Ω·cm2 in 3.5 wt% NaCl solution.

Design of Ascorbic Acid Eutectic Mixtures With Sugars to Inhibit Oxidative Degradation.

L-Ascorbic acid (ASC), commonly known as vitamin C, acts as an anti-oxidant in the biological system. It is extensively used as an excipient in pharmaceutical industry, food supplements in fruit juices, and food materials due to its free radicals scavenging activity. Main drawback of ASC is its poor aqueous stability owing to the presence of lactone moiety that is easily oxidized to dehydroascorbic acid and further degraded. To improve aqueous stability and inhibit oxidative degradation, ASC was co-crystallized to constitute binary eutectic compositions with mono and di-saccharides such as glucose, sucrose, lactose, and mannitol. The eutectics were confirmed by their (single) lower melting endotherm compared to ASC and sugars, although Powder X-ray diffraction (PXRD) and Fourier transform Infrared spectroscopy (FT-IR) data confirmed the characteristics of their physical mixture. Scanning electron microscope (SEM) images of the binary eutectics confirmed their irregular morphology. The ASC eutectics exhibited improved shelf-life by 2–5-fold in weakly acidic (pH 5) and neutral (pH 7) aqueous buffer medium, whereas the eutectic with glucose enhanced shelf-life only by 1.1–1.2-fold in acidic medium (pH 3.3 and 4). Notably, stabilizing effect of the sugar eutectics decreased with increasing acidity of the medium. In addition, higher binding energy of the disaccharide eutectics partially supports the aqueous stability order of ASC in the neutral pH medium due to more number of non-bonded interactions than that of monosaccharides.

Investigation of ultrasound-assisted soldering of SiC ceramics by using Zn-Al-In solder for high-temperature applications

PurposeThis study aims to investigate soldering of SiC ceramics by using Zn-Al-In-based solders and ultrasonic soldering. The focus was on the quality of soldered joints, examining the boundary of the solder/substrate joint and the strength of the fabricated joints. Moreover, the fractured surfaces of joints were assessed.Design/methodology/approachThe Zn-5Al base, which is considered for eutectic solder, was used in experiments. When manufacturing this solder, In was also added to at 1 Wt.%. The soldering of SiC substrates on a hot plate with ultrasonic assistance was performed.FindingsThe solder at room temperature consists of a primary segregated solid solution (Zn) and the binary eutectics (Zn) + (Al) with a high Al content and binary lamellar eutectic with a high Zn and In content non-uniformly distributed on the grain boundaries. The average tensile strength of the Zn5Al1In solder was 52 MPa. The ceramic material was wetted during soldering via reaction between the solder and the SiC substrate, with the formation of Al-Si reaction products. The thickness of the reaction layer on the boundary was 0.5–1.1 µm. The average strength of the soldered joint was 59 MPa. The obtained results confirmed the high efficiency of ultrasonic soldering in air.Originality/valueThis work has characterised Zn5Al1In soldering alloy and examining soldering SiC ceramics by a flux-less ultrasonic process. The analyses were oriented to assess the strength and structure of the solder and the soldered joints. Based on the achieved results, it is possible to predict the suitability of the solder alloy for flux-free soldering of SiC ceramics.

Composition origin of Cu-Zr bulk metallic glasses understood via a “dual-cluster” model of binary eutectics

Cu-Zr is an essential binary bulk glass-forming system with the three best bulk metallic glasses at Cu64Zr36, Cu56Zr44, and Cu50Zr50, which are eutectic or near-eutectic compositions. The current study reveals their composition origin by interpreting these eutectics via a “dual-cluster” model, where a eutectic is composed of two single-cluster-based chemical units derived from the corresponding eutectic phases in simple integer proportions. Each chemical unit represents a stable liquid formulated by the cluster-plus-glue-atom model. For example, eutectic Cu61.8Zr38.2 is deciphered as [Cu-Cu7Zr5]Cu1+4{[Zr-Cu10Zr6]Cu1} = Cu61.6Zr38.4, where the former is from eutectic phase Cu8Zr3 and the latter from another eutectic phase Cu10Zr7. The excellent glass forming composition Cu64Zr36 within this eutectic zone originates from the chemical unit of the Cu8Zr3 phase, [Cu-Cu7Zr5]Cu1 = Cu64.3Zr35.7. Two other eutectics, Cu56.0Zr44.0 and Cu45.7Zr54.3, are also interpreted using this dual-cluster model, leading to suitable glass formers Cu56Zr44 and Cu50Zr50.

On the pressure dependence of salty aqueous eutectics

The eutectic is fundamental to multicomponent systems, defining the lowest temperature at which a given liquid phase is stable. Although binary aqueous eutectics have been broadly characterized at atmospheric pressure, eutectic data at high pressure are scarce, leaving critical gaps both in the data available for modeling and in our understanding of how eutectic equilibria may evolve with pressure. In this work, we deploy a simple, high-throughput, isochoric freezing method to measure the pressure dependences of five binary aqueous eutectics, chosen for their importance in compositional modeling of the distant icy planets deemed most likely to harbor life. Our data reveal that the pressure dependence of all the eutectics measured herein can be approximated by the pressure dependence of the ice Ih melting curve, providing a key rule of thumb for future analysis, and we further demonstrate multiple methods by which additional thermophysical properties of these high-pressure eutectics may be extracted from the measured pressure-temperature coordinates. • Characterize high-pressure eutectics for several aqueous binaries • Eutectic pressure dependences approximately follow pressure-melting curve of ice Ih • Develop methods to extract additional eutectic properties from measured P-T curves • Isochoric freezing method enables high-throughput measurement of multiphase equilibria The eutectic defines the threshold of stability for liquid phases, and high-pressure eutectic data are essential to the modeling of icy worlds. Chang et al. acquire measurements of the pressure dependences of five salty aqueous eutectics, providing both reference data and physical insight into the pressure evolution of the eutectic temperature.

A strategy to design eutectic high-entropy alloys based on binary eutectics

• we employed a useful strategy to design EHEAs and quickly locating eutectic compositions in multicomponent HEAs based on binary eutectic compositions. • Nb 0.62 Fe 1.98 Co 1.22 Ni 1.00 exhibits a fully eutectic microstructure confirmed by both SEM and DSC results • Our findings provide a new strategy for a starting point for quickly pinpointing EHEAs. Although eutectic high entropy alloys (EHEAs) display homogeneously fine microstructure, outstanding castability and promising industrial application potential, how to search for the eutectic compositions in multicomponent high-entropy alloys (HEAs) remains to be challenging. Herein, the strategy which was proposed for pinpointing good glass formers in the field of bulk metallic glasses was utilized for quickly locating EHEA compositions in Nb-(Fe, Co, Ni), Zr-(Fe, Co, Ni) and Hf-(Fe, Co, Ni) HEA systems based on the constituent binary eutectics. As a demonstration, the eutectic compositions in the Nb-(Fe, Co, Ni), Zr-(Fe, Co, Ni) and Hf-(Fe, Co, Ni) HEA systems were quickly determined using this new approach. The newly designed EHEAs showed ultrafine eutectic microstructures, good castability and decent compressive mechanical properties. Current findings clearly demonstrated that this proposed approach is effective for searching for eutectic compositions in HEAs, which will expedite alloy design of EHEAs with strong solid solution strengthening effects.

Dual-cluster model of Sn-based binary eutectics and solders

Sn-based solders are typically binary eutectic-based and understanding of the eutectic compositions at atomic level is important to guide the development of improved solder alloys. In the present work, Sn-based eutectics of Sn-(Zn, Bi, Pb, Ag, Au, Mg) are investigated utilizing a dual-cluster model, which states that a eutectic liquid is composed of two chemical units from relevant eutectic phases and each unit is expressed by a cluster-plus-glue-atom model, [cluster](glue atoms). By introducing Friedel oscillation, the number of atoms in the chemical unit is calculated. Results include determining that the β-Sn phase being formulated as [Sn-Sn10]Sn5, i.e., the central Sn atom is nearest-neighbored by ten Sn atoms and glued by five others. The Sn-(Zn, Bi, Pb, Ag, Au, Mg) eutectics are well defined by dual-cluster formulism, which is applied to examine Sn-based multi-element commercial solder alloys. The results emphasize that the alloying elements correspond to integer substitutions of Sn in the basic units. The present method provides a quantitative approach towards developing a practical composition interpretation and design tool for Sn-based eutectic solders.

Preparation and Thermal Properties of Hexadecanol-Myristic Acid Eutectics/ Activated Carbon Composites as Shape-stabilized Phase Change Materials in Thermal Energy Storage

In this study, hexadecanol-myristic acid (HD-MA) binary eutectic mixtures were adsorbed into activated carbon (AC) to prepare the composite phase transition materials(CPCMs). In the hexadecanol-myristic acid/activated carbon (HD-MA/AC) composites, the mixture of HD–MA acted as the phase change energy storage material and the AC was used as the matrix supporting material. Activated carbon is a kind of inorganic supporting material, which has developed pore structure, strong adsorption, high mechanical strength, corrosion resistance and good thermal stability. As the supporting material, activated carbon was helpful to prevent the eutectics from leakage. The chemical structure and crystal phase structure of HD-MA/AC composites were tested by FT-IR and XRD. The microstructure of the composites was observed through field emission scanning electron microscopy (FE-SEM). It was found that the organic binary eutectics were adsorbed on the surface and inside by activated carbon. Thermal properties of the composites were measured by differential scanning calorimetry (DSC). The results of performance test demonstrated that the satisfactory sample CPCM1 melted at 42.38 °C with latent heat of 76.24 J/g and solidified at 38.32 °C with latent heat of 67.08 J/g. The test results of TGA indicated that the prepared composites of hexadecanol-myristic acid/activated carbon possessed great thermal stability and high reliability. It is predicted that the shape-stabilized HD-MA/AC composites have great potential for thermal energy storage.

High Strength Al-La, Al-Ce, and Al-Ni Eutectic Aluminum Alloys Obtained by High-Pressure Torsion.

A comparative analysis of the effect of high-pressure torsion (HPT) on the microstructure and tensile properties of the Al–10% La, Al–9% Ce, and Al–7% Ni model binary eutectic aluminum alloys is carried out. An HPT of 20-mm diameter specimens in as-cast state was carried out under constrained conditions, at room temperature, pressure P = 6 GPa, and number of turns N = 5. It is shown that the formation of nano- and submicrocrystalline structures and the refinement of eutectic particles in aluminum alloys simultaneously provide a multiple increase in strength while maintaining a high plasticity margin. This combination of properties has been achieved for the first time for severely deformed binary aluminum eutectics. The relationship between the type of eutectic particles, the structure formation process and the mechanical properties of the aluminum alloys has been established. The thermal stability of severely deformed aluminum alloys at heating up to 200 °C has been studied.