Formation Of Solid Solution Research Articles

A first-principles investigation on the enthalpy landscape for the hibonite solid solution: Implications for a nebular barometer

Abstract Hibonite, nominally CaAl12O19, is among the first minerals thermodynamically predicted to have formed in the early history of our solar system. It can incorporate significant amounts of Ti (≤15 wt%, ∼2 cations per formula unit) into its crystal structure as both Ti4+ and Ti3+. The main pathways for Ti incorporation in the solar nebula include a direct substitution of Ti3+ replacing Al3+ and a coupled substitution in which Ti4+ and Mg2+ replace two Al3+. Additionally, the formation of oxygen vacancies can also reduce a Ti4+ cation to Ti3+ by trapping a free electron. The relative amounts of these cations potentially reflect the fugacity of oxygen (fO2), a fundamental thermodynamic parameter, that prevailed when hibonite first formed or last equilibrated. However, the Ti content and its oxidation state in hibonite does not depend solely on fO2. The composition of the system is, thus, a key factor in changing the Ti4+/ΣTi ratio of the structure concurrently with the fO2. Therefore, it is necessary to understand the energetics, complex crystal chemistry, and substitution reactions of hibonite in order to relate the Ti oxidation state to the fO2 of the nebular system in which condensed. To that end, we report DFT calculations (0 K) to determine the ground-state energies and the enthalpy of formation (ΔH) of hibonite solid solutions that span the range reported in meteorites. Our results show that coupled substitution is energetically favored (ΔH=-96.70 kJ.mol-1, from oxides). In comparison, the formation of oxygen vacancies is energetically unfavorable, but similar to Ti3+ direct substitution for Al3+ (ΔH=∼60 kJ.mol-1, from oxides), which is commonly observed in hibonite. It is therefore necessary to consider oxygen vacancies as a potential mechanism for controlling the incorporation of Ti3+ into hibonite, in addition to direct replacement reactions. We provide here the first reliable estimation of the formation enthalpies for the hibonite solid solution that includes solutes and point defects. The results presented herein constitute a significant advance towards the establishment of a comprehensive Gibbs free energy description of the hibonite solid solution, which is ultimately required for accurate modelling of its thermodynamic stability within the early solar nebula.

CRYSTALS GROWTH OF AND CRYSTAL STRUCTURE OF SOLID SOLUTIONS IN THE Ag8SiS6 HOMOGENEITY REGION

Compounds with an argyrodite structure are a family of complex chalcogenides that demonstrate a wide range of properties: superionics, thermoelectrics, sensors, and photovoltaic materials. For sulfur-containing representatives, the main field of application is solid-state ionics. However, the formation of solid solutions is used to modify and improve the functional parameters of individual argyrodites. When solid solutions are formed by iso- or heterovalent substitution, an additional deformation of the crystal structure occurs, which increases the efficiency of ion transport. For the growth of single crystals, the method of direct crystallization by melt-solution technique was used. Based on the results of DTA, technological conditions for growing single crystals of solid solutions of Ag7.75P0.25Si0.75S6 and Ag7.5P0.5Si0.5S6 were developed. The temperature of the melt zone (Tmelt) was 50 K higher than the melting point of the solid solutions, and the temperature of the annealing zone (Tann) was 2/3 of their crystallization temperature determined by the DTA method. As a result, single crystals of dark gray color with a metallic luster were obtained. The crystal structure of the solid solutions of Ag7.75P0.25Si0.75S6 and Ag7.5P0.5Si0.5S6 was determined by the Rietveld method. Both solid solutions crystallize in a rhombic crystal system, SG Pna21, with lattice parameters: a = 15.06 Å, b = 7.44 Å, c = 10.54 Å (Ag7.75P0.25Si0.75S6) and a = 15.06 Å, b = 7.44 Å, c = 10.54 Å (Ag7.5P0.5Si0.5S6).

Utilization of Novel (KNbO3)1−x(Ba2FeNbO6)x (x = 0.1, 0.2, 0.3) Solid Solutions for Efficient Photo‐Assisted Fenton Degradation of Methylene Blue Dye

Novel (KNbO3)1−x(Ba2FeNbO6)x (x = 0.1, 0.2, 0.3) solid solutions corresponding to K0.82Ba0.18Fe0.09Nb0.91O3, K0.64Ba0.36Fe0.18Nb0.82O3, and K0.46Ba0.54Fe0.27Nb0.73O3 compounds have been synthesized via molten salt method. X‐ray diffraction confirms the formation of solid solutions, while transmission electron microscopy combined with energy‐dispersive spectroscopy results demonstrates a homogeneous distribution of elements. The obtained solid solutions crystallized in a cubic crystal structure, whereas the parent KNbO3 possesses an orthorhombic structure. The wide bandgap semiconductor KNbO3 transformed into a visible‐light‐active material, with its bandgap energy reduced from 3.56 eV to ≈2.4 eV. The substitution of K in KNbO3 with Ba is responsible for structural modification from orthorhombic to cubic symmetry, whereas both structural modification and the substitution of Nb with Fe correlated with optical properties. The photocatalytic activities of all obtained solid solutions are improved compared with the parent KNbO3 and Ba2FeNbO6 compounds for photocatalytic degradation of methylene blue (MB) dye. Among the series of solid solutions, K0.82Ba0.18Fe0.09Nb0.91O3 photocatalysts show the highest MB removal efficiency owing to its relatively higher surface area, suppressed charge carrier recombination, and more negative conduction band edge. Moreover, K0.82Ba0.18Fe0.09Nb0.91O3 photocatalyst (0.1 g) combined with hydrogen peroxide (H2O2) to form a novel photo‐Fenton system, achieving almost complete degradation of 100 mL of 10 mg L−1 MB dye in 30 min.

Improving fracture toughness and densification behavior of single‐phase TaC–HfC ceramic with carbon additives

AbstractThis investigation was undertaken to determine the role of carbon additives on the densification behavior and fracture toughness of TaC–HfC ceramic. The composition of TaC‐19 vol% HfC‐5 vol% VC with 10 vol% nano graphite/10 vol% nano carbon black was sintered by hot‐pressing (HP) method. Also, the sintering temperature varied from 1700°C to 2000°C. Vanadium carbide was used as a sintering aid to minimize the porosity for the given hot‐pressing temperatures while keeping the consolidation temperature low. The analysis of XRD patterns revealed that the sintering process led to the formation of a ternary solid solution in the samples accompanied by the entire consumption of HfC and VC phases. Also, the presence of carbon additives increased the relative density from 96% to 100% by enhancing the sintering temperature from 1700°C to 2000°C. It was significantly higher than the carbon‐free sample, which had a maximum value of 96.7% at 2000°C. The results also indicated that the maximum fracture toughness of 7.1 MPa.m1/2 was obtained for nano carbon black contained samples at the sintering temperature of 1900°C and above. The toughening mechanisms in samples were discussed, too.

Highly porous Ni/MgO-ZrO2 catalysts for dry reforming of methane and the effects of MgO addition on the mechanisms

Dry reforming of methane (DRM) is a promising pathway to convert greenhouse gas into syngas. However, the commonly used Ni based catalysts suffer deactivation due to severe sintering and coking. In this paper, a series of porous Ni/MgO-ZrO2 catalysts (5Ni/xM(1-x)Z, x = 0, 20, 40, 60, 80 wt%, respectively) with high specific surface area were synthesized by a facile combustion method followed by incipient impregnation. It is found that the appropriate amount of MgO (40 %) addition in ZrO2 favors high porosity and high specific area. More MgO enhances the basicity of the catalyst as well as the metal-support interaction (MSI) by the formation of NiO-MgO solid solution, thus improving DRM activity and coking resistance. However, excessive MgO addition leads to over-strong MSI and lower porosity, resulting in lower DRM activity. The catalyst with 40 % MgO addition (5Ni/40M60Z) exhibits the best activity (conversions of CH4 ∼ 76 %, CO2 ∼ 83 %) and stability (>50 h) at high GHSV = 96000 ml/gcat·h and 750 °C. in situ DRIFTS reveals the mechanism that MgO addition improves DRM activity and stability. Compared with ZrO2 where CO2 adsorbs as monodentate carbonate, CO2 tends to adsorb on 40 %MgO-60 %ZrO2 as bidentate carbonate and then easily transfer to more stable intermediate bidentate formate, thus improving DRM activity and coking resistance. This study provides new insights on the role of Mg addition in Ni/MgO-ZrO2 DRM catalysts.

Leaching behavior of arsenic in coal under the action of mine water

Arsenic, a potentially harmful element in coal, has a detrimental effect on the quality of groundwater and the water cycle. There is a significant safety risk to the drinking water and overall health of residents living near mining areas. It is of great significance to explore the leaching pattern of arsenic in coal under the influence of mining and identify the main controlling factors for the prevention and control of groundwater pollution in mining areas. In this paper, we selected long flame coal and non-caking coal from Wulanmulun Mine, along with four types of water samples from the mine area, as the research subjects. Our aim was to investigate the leaching mechanism of arsenic in groundwater under the influence of coal-water interaction in the mine area. To achieve this, we conducted indoor batch coal-water leaching simulation experiments. The results show that: 1) The four leaching solutions, which correspond to four groundwater types at the coal mine production site, exhibit similar trends in the presence of arsenic ions after water-coal interaction. The leaching process can be divided into three distinct zones: a rapid descent zone, a dissolution shock zone, and a dissolution linear stable zone. The initial decline rate of arsenic content in different water samples is proportional to the initial concentration of arsenic in the water samples. 2) The dissolution of arsenic has a strong negative correlation with DO, and the lower the oxygen content in the solution, the higher the arsenic ion content. There is a relatively strong negative correlation with pH value. It has a strong positive correlation with the leaching of Mg, K, V, Cr, and Fe, and a relatively small positive correlation with the leaching of Mn and Cu. The leaching degree of Mg, K, V, Cr and Fe can be used as a sign to explore the leaching or content change of arsenic in actual mining environment. 3) Most arsenic in coal occurs in pyrite in the form of isomorphism or solid solution, and the dissolution of arsenic is related to pyrite content and its oxidative dissolution behavior. The higher the pyrite content, the greater its oxidation degree, and the higher the arsenic content in the solution. 4) Clay minerals, predominantly kaolinite, found in different coal samples demonstrate varying capacities for arsenic adsorption in the leaching solution. The results of this experiment indicate that the adsorption capacity of clay minerals in long flame coal is considerably higher than that observed in non-caking coal, leading to a substantial decrease in the concentration of arsenic ions in the solution. This reduction is associated with a notable decline in the arsenic concentration within the groundwater associated with the coal samples collected on-site. The results suggest that the leaching of arsenic from the coal samples will not lead to arsenic contamination in four distinct categories of groundwater. This finding holds considerable importance for the management and remediation of water pollution in mining contexts.

The thermodynamics of multicomponent high-entropy materials

AbstractHuman development has been based for millennia on manufacturing materials using a conventional alloying strategy of selecting a principal component for the primary property requirement of the material and then adding one or two minor alloying components at relatively low concentrations, either to enhance the primary property or to provide additional secondary properties. We have discovered relatively recently that, with sufficiently large numbers of alloying elements added in sufficiently large concentrations, the configurational entropy of mixing can often become large enough to suppress the formation of brittle compound phases, leading instead to the formation of multicomponent high-entropy solid solutions. In fact, there are literally billions of multicomponent high-entropy single-phase solid-solution materials, with a wide range of exciting new properties, in most cases relatively straightforward to manufacture by conventional processing methods. There seems, however, to be an upper limit to these effects, so that, beyond about ten or twelve alloying components, the inevitable increase in chemical diversity prevents the configurational entropy of mixing from suppressing the increasingly strong chemical reactions between them. This paper discusses in more detail the thermodynamic balance between: (1) increasing configurational entropy and promoting high-entropy solid solutions; and (2) increasing chemical diversity and promoting the formation of brittle compound phases. This is discussed on the basis of regular solution thermodynamics, without the need for more complex, semi-empirical Calphad calculations that can sometimes obscure the underlying key physical and chemical principles. The results show: (1) why large single-phase solid-solution regions are relatively common in multicomponent phase space; (2) why single-phase solid solutions are often favoured over stoichiometric compounds for large numbers of chemically similar components, in concentrated rather than dilute proportions, at high temperatures, and after quenching to room temperature; and (3) the difficulty of detailed thermodynamic analysis in multicomponent materials because of the large numbers of thermodynamic parameters that need to be known and the corresponding lack of underlying thermodynamic measurements.

Formation and Segregation of the Ru- and Rh-MgO Solid Solutions.

Structural changes in Ru- and Rh-loaded magnesium oxide (MgO) subjected to thermal treatment were investigated by using X-ray absorption spectroscopy. The thermal treatment of the MgO-loaded Ru and Rh nanoparticles led to the formation of Ru-MgO and Rh-MgO solid solutions, respectively. The valences of Ru and Rh in the solutions were 4+ and 3+, respectively, as determined by the Ru and Rh K-edge X-ray absorption near-edge structure (XANES). The degree of solid solution formation was the highest at 873 and 1073 K in Ru-MgO and Rh-MgO, respectively, as observed in the extended X-ray absorption fine structure and XANES analyses. The nearest neighboring Ru-O and Rh-O bond distances were shorter than the Mg-O bond in MgO. The dispersion of Ru and Rh on the MgO surface, measured by CO adsorption, increased for samples thermally heated at 1273 K, suggesting that the segregation of Ru or Rh from the solid solutions occurred at this temperature. Consequently, a relatively high dispersion was realized in the sample thermally heated to 1273 K. A good correlation was found between the dispersion value of Ru in Ru/MgO and the NH3 decomposition activity.

Ti1-xAlxN or TiN + AlN: An investigation about Al influence on titanium aluminum nitride thin films structural organization

Ti1-xAlxN thin films with different Al contents (Ti0.8Al0.2N, Ti0.6Al0.4N and Ti0.4Al0.6N) were deposited by reactive magnetron sputtering in order to determine the real structure formed in these coatings: a single ternary nitride, with a substitutional solid solution formation, or the presence of two binary nitrides, TiN + AlN. The elementary composition, morphology homogeneity, chemical elements distribution, crystalline structure, grain size evaluation, modification on coatings structure and formed compounds were determined. GAXRD analyses evinced a grain size growth for all Ti1-xAlxN samples, suggesting that aluminum atoms are not present as a single AlN phase, but as a ternary nitride. In XPS analyses, N 1s spectrum for all samples exhibited a shift toward lower binding energies in Ti-N component, attesting the Ti-Al-N bond presence. Moreover, signatures of Al 3p and Ti 3d band shift were detected in the valence band region, confirming the Ti1-xAlxN solid solution formation for all deposited samples.

Enhancement of CO2 adsorption and oxygen transfer properties on γ-Al2O3 support through surface modification with MgO-ZrO2 for coke suppression over Ni catalyst in CO2 reforming of methane

This work focuses on employing commercial γ-Al2O3 for surface modification with MgO-ZrO2 mixed oxide to enhance the potential of CO2 adsorption and oxygen mobility. This enhancement facilitates its application as a support in catalysts for CO2 utilization such as CO2 reforming of methane (CRM). To achieve this perspective, γ-Al2O3 was modified with 10 wt.% of various MgO and ZrO2 contents (MgO:ZrO2= 10:0, 9:1,7:3, 5:5, 3:7, 1:9 and 0:10) using the impregnation method. All samples including unmodified γ-Al2O3 (Al) were characterized. Due to the increase in basicity and oxygen transfer around the surface, the improvement of the CO2 adsorption was observed on γ-Al2O3 modified with 9 wt.% MgO-1 wt.% ZrO2 (9Mg1ZrAl) and 10 wt.% MgO (10MgAl), respectively. An application of these two superior samples as a support of 10 wt.% Ni (10Ni) catalysts for CRM was investigated and compared with an unmodified γ-Al2O3. Characterization results suggest the formation of NiO-MgO solid solution at the surface due to the decrease in metal-support interaction and the increase in metal dispersion. The Ni catalysts with the surface-modified support show higher CO2 activity that raises carbon deposition resistance. The greatest coke prevention was observed on 10Ni/9Mg1ZrAl that lowers the coke deposition by 42 % compared to 10Ni/Al. It indicates that the composition of this modification allowed very low ZrO2 portion to merge with MgO and MgO to form solid solution with NiO. This enables the 10Ni/9Mg1ZrAl catalyst to generate labile oxygens which can be conveyed to the Ni metal sites on the catalyst.

Preparation of iron-based composites reinforced with submicron/nano-sized TiC ceramic particles by in-situ reaction in melts and one-step integrated hot pressing densification

The iron matrix composites strengthened with submicron/nano-sized TiC particles dopping with different alloying elements (Mo, Ni) were prepared by melt-in-situ reaction and one-step integrated hot compaction. The results indicate that the incorporation of Mo and Ni through alloying treatment can refine ceramic particles, and thus lead to a significant improvement in the uniformity of the microstructure. The mismatch between the TiC and α-Fe is significantly reduced and the interface stability is enhanced. The yield strength of 1904 MPa and maximum compressive strength of 2605 MPa of TiC/Fe composite with the addition of 4 wt.% Mo are 28.3 % and 23.9 % higher than those without alloying elements, respectively. The yield strength of 2032 MPa and maximum compressive strength of 2815 MPa of TiC/Fe composite with the addition of 2 wt.% Ni are 36.9 % and 33.9 % higher than those without alloying elements, respectively. First-principles calculation results indicate that Mo atoms tend to accumulate at the interface, while Ni atoms can easily substitute Fe atoms, resulting in the formation of a FeNi solid solution. The primary strengthening mechanisms of TiC/Fe composites dopping Mo are the refinement strengthening of ceramic particles. The interface bond between Fe matrix and TiC particles is also strengthened. The addition of Ni primarily leads to solid solution strengthening and grain refinement. This TiC particle manipulating strategy within Fe melt can effectively optimize the corresponding interfacial bonding, lead to comprehensive improvement in property, and finally realize the expanding application at specific wear locations.

Eu2+-activated hexagonal aluminate solid solution phosphors with high quantum efficiency and anti-thermal quenching for pc-LEDs

The luminescence quantum efficiency and thermal stability are important parameters for phosphors when applied in phosphor-converted white light-emitting diodes (pc-LEDs). A facile solid solution strategy was applied to improve the quantum efficiency and thermal stability based on Na-β-Al2O3:Eu2+. Ba2+, Mg2+, and Ge4+ are introduced to replace Na+ and Al3+ simultaneously, besides the substitution of Na+ by Eu2+. X-ray powder diffraction, scanning electron microscopy combining elemental mapping indicate the formation of solid solution from Na-β-Al2O3:Eu2+ and BaMgAl10O17:Eu2+. The internal and external quantum efficiencies (IQE, EQE) both increase through solid solution with nearly unchanged blue emission at 468 nm. The IQE and EQE values of nominal Na1.6-xBaxAl11-3xMg2xGexO17+δ:0.2Eu2+ (x = 0.3) are as high as 90.4 % and 68.1 %, respectively. Furthermore, the thermoluminescent curves suggest that the defects decrease by introducing Ba2+, Mg2+, and Ge4+ ions. Therefore, the anti-thermal quenching degree decreases, resulting in better thermal stability. The proto-type white pc-LED based on the as-synthesized blue phosphor has a color-rendering index of 87, and nearly unchanged emission profile versus driving currents. The solid-solution phosphors show their potential as blue-emitting component for white pc-LEDs.

Phase Formation, Polymorphism, Optical Properties, and Conductivity of Nd2WO6-Based Compounds and Solid Solutions

Phase Formation, Polymorphism, Optical Properties, and Conductivity of Nd2WO6-Based Compounds and Solid Solutions

High-Temperature Behavior of Pd/MgO Catalysts Prepared via Various Sol-Gel Approaches.

A series of Pd/MgO catalysts based on nanocrystalline MgO were prepared via different sol-gel approaches. In the first two cases, palladium was introduced during the gel preparation, followed by drying it in supercritical or ambient conditions. In the third case, aerogel-prepared MgO was impregnated with an ethanol solution of Pd(NO3)2. The prepared catalysts differ in particle size and oxidation state of palladium. The catalytic performance and thermal stability of the samples were examined in a model reaction of CO oxidation at prompt thermal aging conditions. The as-prepared and aged materials were characterized by low-temperature nitrogen adsorption, UV-vis spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and ethane hydrogenolysis testing reaction. The highest initial activity (T50 = 103 °C) was demonstrated by the impregnated sample, containing Pd0 particles of 3 nm in size. The lowest T50 value (215 °C) after aging at 1000 °C was demonstrated by the impregnated Pd/MgO-WI sample. The high-temperature behavior of the catalysts was found to be affected by the initial oxidation state and dispersion of Pd. Two deactivation mechanisms, such as the agglomeration of Pd particles and migration of small Pd species into the bulk of the MgO support with the formation of Pd-MgO solid solutions, were discussed.

Controlled synthesis of CeNbZrO solid solution with high thermal stability and application in catalytic degradation of C6H5CH3 and C6H5Cl

A series of CeNbZrO composite oxides with different (CeNb)/Zr molar ratios were prepared by urea homogeneous precipitation method and systematically characterized. The thermal stability, degradation performance and structure-activity relationship of these catalysts for eliminating C6H5CH3 and C6H5Cl mixed pollutants were evaluated. The results indicated that with the increase of ZrO2 content, the catalytic activity of CeNbxZrO increased first and then decreased. Among them, the CeNb3.3ZrO catalyst (Ce/Nb/Zr=2/1/3.3, molar ratio) exhibited the highest catalytic activity (C6H5CH3: T90 %=310 °C, C6H5Cl: T90 %=344 °C) and thermal stability. Compared with the traditional CeO2-MnO2 catalyst, the T90 % of the CeNb3.3ZrO catalyst in the degradation of C6H5Cl was reduced by 100 °C. CeNb3.3ZrO exhibited high specific surface area and strong oxidation ability, which enhanced the redox cycles and promoted the interactions between metal ions. In addition, the formation of Ce2Zr3O10 solid solution made its structure stable even at high temperature. Overall, the optimized CeNb3.3ZrO has broad prospects in the catalytic treatment of volatile organic compounds and some other related fields in thermal catalysis.

Ca(Mo,W)O4 Solid Solutions Formation in CaMoO4‐CaWO4 System

AbstractThe formation of solid solutions in the CaMoO4‐CaWO4 binary system is investigated by X‐ray diffraction, Raman spectroscopy, and scanning electron microscopy methods. The intermixtures of CaMoO4 and CaWO4 components are sintered in 600—1200 °C temperature range (in 100 °C increments). The solidus of the CaMoxW(1‐x)O4 system is studied by the differential scanning calorimetry method in the x = 0.3 … 1.0 range. CaMoO4‐CaWO4 phase diagram is constructed up to 1550 °C. The minimal sintering temperature in order to get CaMoxW(1‐x)O4 solid solution is shown to be 800 °C. Cathodoluminescence study of CaMoxW(1‐x)O4 compounds showed higher intensity of molybdate luminescence type.

Recent research progress on Li29Zr9Nb3O40-based solid electrolytes for lithium batteries

All-solid-state batteries have become a research hotspot because of their high specific capacity and safety. Solid-state electrolytes are the key material of all-solid-state lithium-ion batteries, and their properties directly affect the overall performance of lithium-ion batteries. So far, many inorganic solid electrolytes have been reported, such as NASICON, LISICON, perovskite, and garnet-type solid electrolyte. However, some lithium-rich rock salt-structured electrolytes, such as Li2ZrO3, LiNbO4, and Li6Zr2O7, have been underappreciated in the field of solid-state electrolytes due to their lower ionic conductivity at room temperature. While investigating solid solution formation, Li6Zr[Formula: see text][Formula: see text]Nb[Formula: see text]O[Formula: see text][Formula: see text][Formula: see text], a new phase known as Li[Formula: see text]Zr9Nb3O[Formula: see text] with a rock-salt structure was discovered. After decades, it was not until a team prepared Li[Formula: see text]Zr9Nb3O[Formula: see text] ceramics by sol-gel method, which exhibited high ionic conductivity (10[Formula: see text]–10[Formula: see text]S cm[Formula: see text]) at room temperature, that the substance showed great potential as a solid electrolyte in all-solid-state lithium-ion batteries. In this paper, the crystal structure, lithium-ion transport mechanism, preparation method, and element doping of Li[Formula: see text]Zr9Nb3O[Formula: see text] are described comprehensively based on research progress in recent years. Then, development prospects and challenges of the concrete application of Li[Formula: see text]Zr9Nb3O[Formula: see text]in all-solid-state lithium-ion batteries are also discussed.

Formation and strengthening mechanism of high entropy nugget for aluminum/steel resistance rivet welding

Resistance rivet welding (RRW) was a promising joining process for aluminum (Al) alloy and steel. The high entropy mixed nugget (HEMN) with the composition of Al0.8CoCrFe1.6Ni was obtained by introducing a high entropy alloy (HEA) rivet in RRW process. The high entropy played a significant role in facilitating the formation of solid solution. The HEMN microstructure exhibited a nanometer-sized weave-like structure caused by spinodal decomposition, comprising both BCC and B2 phases. The average hardness of the HEMN exceeded that of the Al/Steel mixed nugget, resulting in higher lap-shear strength and ductility. The analysis of strengthening mechanism demonstrated that the lattice misfit and order strengthening were the primary contributors. This study provided a novel strategy for joining dissimilar metal materials.

Role of Mo and Zr Additions in Enhancing the Behavior of New Ti–Mo Alloys for Implant Materials

AbstractThe utilization of Ti–Mo alloys in biomedical applications has gained attention for use in biomedical applications owing to their non-toxicity, reasonable cost, and favorable properties. In the present study, Ti–12Mo–6Zr and Ti–15Mo–6Zr alloys were prepared using elemental blend and mechanical alloying techniques. The effect of alloying elements Mo and Zr of Ti–Mo alloy, as well as the effect of fabrication techniques of Ti–Mo–Zr trinary alloys, were investigated. Thermodynamic calculations supported by CALPHAD analysis revealed that the addition of Zr increases lattice distortion, which contributes to enhancing the strength. Conversely, adding Mo decreases the enthalpy, facilitating improved mixing and solid solution formation. The as-sintered samples were characterized by X-ray diffraction, optical microscope, and scanning electron microscopy, and their microhardness, compressive, and corrosion behavior were investigated. Among all the investigated alloys, Ti–15Mo–6Zr alloy prepared by the mechanical alloying technique, milled for six hours at 300 rpm, compacted at 600 MPa, and sintered at 1250 ℃, shows good comprehensive mechanical properties with a preferable compressive strength (− 1710 MPa) and hardness (396 HV5), as well as the lowest wear rate (0.69%) and corrosion rate (0.557 × 10–3 mm/year). This can be related to the solid solution strengthening and relative density, together with dispersion and precipitation strengthening of the α phase. Remarkably, the combination of high mechanical and corrosion properties can be achieved by tailoring the content of the α phase, controlling the density, and providing new fabricating techniques for β Ti alloys. Graphical Abstract

Rhombohedral phase high-entropy alloy of AlMnCuZnBi as a photo-Fenton catalyst for methyl orange degradation

The formation of solid solutions with five or more elements having nearly equiatomic contributions termed as high entropy alloys (HEA), is recent strategy for the development of new materials. Such alloys have displayed superior properties than the conventional ones. The prepared alloys are generally face- or body-centered cubic structures with a few exceptions for orthorhombic and hexagonal close packed structure. In this, we report the synthesis of HEA of AlMnCuZnBi having rhombohedral crystal structure. The material was prepared by vacuum arc melting route. Both the diffractions (X-ray and electron) confirm its structure. The calculated thermodynamic empirical parameters e.g. ΔSmix, ΔHmix, δ, VEC and Ω even validate the feasibility of this single phase solid solution. The HEA had shown feeble ferromagnetic behaviour. The rhombohedral structured HEA may open up new possibilities for various emerging applications. The proposed HEA acted as a catalyst for photo-Fenton like reaction and could degraded methyl orange dye completely in 170 minutes.