Intermetallic Research Articles

Microstructure and mechanical properties of Mg/Al laminated composite: The effect of transition layer thickness

This study successfully prepared Mg/Al laminated composites with various thicknesses of pure Cu transition layer via extrusion, overcoming the challenge of forming of Mg/Al composite plates through stacked extrusion technology. The effects of varying Cu layer thicknesses on the microstructure, mechanical properties, and fracture behaviors were systematically investigated. Microstructure analysis showed an uneven Cu layer distribution at the interface of the composite plate, characterized by alternating thicker and thinner layers, which stemmed from the low fluidity of pure Cu during extrusion. Although the thicker Cu layer significantly inhibited the diffusion of Mg and Al elements, there was still a significant enrichment of Mg-Al intermetallic compounds (IMCs) in the thinner Cu layer. There hard and brittle IMCs caused cracking during the deformation process. Increasing Cu layer thickness did not significantly affect the microstructure but contributed to the decrease of strength owing to increased stress concentration. Moreover, the thicker Cu layer exacerbated its uneven distribution and Mg-Al IMCs enrichment at the interface, resulting in a pattern of first decreasing and then increasing elongation and shear strength of the laminated composite.

Investigating laser and ultrasonic welding of pouch cell multi-foil current collectors for electric vehicle battery fabrication

The escalating necessity for more efficient and defect-free joining of ‘ultra-thin foil collectors-to-tabs’ in electric vehicle (EV) Li-ion pouch cells motivates this study. The prevalent ultrasonic welding (USW) method for these joint types, faces limitations such as design constraints and access requirements, laser welding (LW) emerges as a promising alternative offering flexibility, one-side access and faster speeds with efficient heat input. This study aims to investigate the feasibility of LW as a viable alternative to USW for joining current collectors-to-tab joints. It compares the mechanical, metallurgical, electrical and thermal analysis of the joints to evaluate both welding techniques for joint defects. The comparison of solid-state material mixing during USW and the intermixing of aluminium (Al) and copper (Cu) during fusion LW using EDX analysis presents interesting observations in the study. The USW generates a thin transition layer with intermetallic compounds (IMCs) attributed to the diffusion of Cu into the Al matrix during joining, which is comparatively lower as in the case of LW with higher material mixing with brittle IMCs like Al2Cu and Al4Cu9. However, the joint strength of LW is comparatively lower than the USW joint attributed to the reduced fusion zone area. Furthermore, from the electrical contact resistance and the joint temperature analysis, it was found that the resistance and temperature vary by as much as 13% and 6%, respectively, for the 50 A and 75 A passing currents when the USW is replaced with the LW process.

Enabling Invar to Ti6Al4V transitions through copper in functionally graded laser powder bed fused components

This study examines the microstructural evolution, elemental distribution, phase composition, and hardness variations in multi-material samples fabricated using Laser Powder Bed Fusion (LPBF) with Invar and Ti6Al4V with compositional gradients mediated by copper. A range of compositional transitions from Invar to Ti6Al4V with different copper fractions are reported. Defects such as gas and keyhole pores were detected in well-deep keyhole mode areas, while lack of fusion defects were observed in samples with pure Cu interlayers due to poor wettability and processing parameter variations. Crack formation between interlayer gradient zones and Invar regions was linked to FeNi and CuNi intermetallic phases. Intermetallic compounds (e.g., FeNi, CuNi, TiFe, TiNi) significantly influenced the microstructure and mechanical performance. Vickers hardness testing shows varying hardness across different builds, with the highest hardness being observed in the gradient zone enabled by pure copper (approximately 620 HV). This study also underscores the need for tailored component design linking build processing parameters and compositional transitions in multi-material LPBF to achieve desired properties and component structural behaviour.

Physico-Chemical and Microstructural Analysis of Al-Mg-Si Alloy Matrix Composites Reinforced Groundnut Shell ash Particulates

Metal matrix composites are an appealing alternative to monolithic metals for a variety of technical applications due to their superior mechanical and physical properties throughout a broad range of operating conditions. In the current study, different weight percentages of 150 µm groundnut shell ash (GNSA) particles (2.5%, 5%, 7.5%, 10%, 12.5%, 15%, 17.5%, 20%, 25% and 30%) were used to reinforce Al-Mg-Si alloy. Stir-casting was used to prepare the composite in a permanent mild steel mould. A number of the composites' physical, chemical, and microstructural characteristics (density, percentage porosity, XRF and SEM-EDS) were assessed, compared, and analysed with those of the matrix alloy. Oxides that could enhance the composites' mechanical, physical, and structural qualities were found during the structural assessment evaluation of the reinforcement. The microstructural analysis demonstrated that the GNSA reinforcements' secondary phase was uniformly distributed throughout the primary phase of the Al-Mg-Si alloy matrix. The added GNSA particles decreased the produced composite's density below that of the base alloy, and the percentage porosity of the composites rose as the groundnut shell ash content increased and remained within the upper limit allowed for cast aluminium metal matrix composites. The composites that were created showed evidence of intermetallic compound formation.

Hydrogen, Oxygen, and Lead Adsorbates on Al13Co4(100): Accurate Potential Energy Surfaces at Low Computational Cost by Machine Learning and DFT-Based Data.

Intermetallic compounds are promising materials in numerous fields, especially those involving surface interactions, such as catalysis. A key factor to investigate their surface properties lies in adsorption energy maps, typically built using first-principles approaches. However, exploring the adsorption energy landscapes of intermetallic compounds can be cumbersome, usually requiring huge computational resources. In this work, we propose an efficient method to predict adsorption energies, based on a Machine Learning (ML) scheme fed by a few Density Functional Theory (DFT) estimates performed on n sites selected through the Farthest Point Sampling (FPS) process. We detail its application on the Al13Co4(100) quasicrystalline approximant surface for several atomic adsorbates (H, O, and Pb). On this specific example, our approach is shown to outperform both simple interpolation strategies and the recent ML force field MACE [arXiv.2206.07697], especially when the number n is small, i.e., below 36 sites. The ground-truth DFT adsorption energies are much more correlated with the predicted FPS-ML estimates (Pearson R-factor of 0.71, 0.73, and 0.90 for H, O and Pb, respectively, when n = 36) than with interpolation-based or MACE-ML ones (Pearson R-factors of 0.43, 0.39, and 0.56 for H, O, and Pb, in the former case and 0.22, 0.35, and 0.63 in the latter case). The unbiased root-mean-square error (ubRMSE) is lower for FPS-ML than for interpolation-based and MACE-ML predictions (0.15, 0.17, and 0.17 eV, respectively, for hydrogen and 0.17, 0.25, and 0.22 eV for lead), except for oxygen (0.55, 0.47, and 0.46 eV) due to large surface relaxations in this case. We believe that these findings and the corresponding methodology can be extended to a wide range of systems, which will motivate the discovery of novel functional materials.

Microstructural evolution of Fe-25 W powder beds during CO2-H2 redox cycling at 800 °C

Fixed powder beds of Fe-25 W at% powders show excellent resistance to degradation during CO2-H2 redox cycling at 800 °C, releasing CO and H2O, respectively, with 100 % metal utilization. During cycling up to 165 full redox cycles (∼500 h), the reaction kinetics improve with cycle number and a stable, hierarchically-porous microstructure forms that shows neither sintering nor densification. The sintering inhibition provided by W addition to Fe stems from the formation of Fe-W mixed phases: as an intermetallic compound (Fe2W) in the reduced state and as a ternary oxide (FeWO4) in the oxidized state. In addition to the large channels running between coarse (100 µm) powder agglomerates, each agglomerate in the powder bed shows both microporosity due to sintering inhibition, and submicron porosity due to a chemical vapor transport reduction mechanism that is active when FeWO4 is reduced by H2 at high temperature. This hierarchical porosity enables fast reactions due to the short diffusion distance to free surfaces, and non-tortuous gas flow through the powder bed. As a result, under high CO2 flow, the CO2:CO ratio is sufficiently high to oxidize Fe3O4 to Fe2O3, improving the CO conversion capability on a per-mole basis.

Development of In Situ Methods for Preparing La-Mn-Co-Based Compounds over Carbon Xerogel for Oxygen Reduction Reaction in an Alkaline Medium.

Metal oxides containing La, Mn, and Co cations can catalyze oxygen reduction reactions (ORRs) in electrochemical processes. However, these materials require carbon support and optimal interactions between both compounds to be active. In this work, two approaches to prepare composites of La-Mn-Co-based compounds over carbon xerogel were developed. Using sol-gel methods, either the metal-based material was deposited on the existing carbon xerogel or vice versa. The metal oxide selected was the LaMn0.7Co0.3O3 perovskite, which has good catalytic behavior and selectivity towards direct ORRs. All the as-prepared composites were tested for ORRs in alkaline liquid electrolytes and characterized by diverse physicochemical techniques such as XRD, XPS, SEM, or N2 adsorption. Although the perovskite structure either decomposed or failed to form using those in situ methods, the materials exhibited great catalytic activity, which can be ascribed to the strengthening of the interactions between oxides and the carbon support via C-O-M covalent bonds and to the formation of new active sites such as the MnO/Co heterointerfaces. Moreover, Co-Nx-C species are formed during the synthesis of the metal compounds over the carbon xerogel. These species possess a strong catalytic activity towards ORR. Therefore, the composites formed by synthesizing metal compounds over the carbon xerogel exhibit the best performance in the ORR, which can be ascribed to the presence of the MnO/Co heterointerfaces and Co-Nx-C species and the strong interactions between both compounds. Moreover, the small nanoparticle size leads to a higher number of active sites available for the reaction.

Photothermal effects on low-temperature hybrid solder joints and its superior drop reliability

Hybrid solder joints incorporating the Sn-3.0Ag-0.5Cu/Sn–58Bi structure have been studied to tackle challenges such as warpage, thermal degradation, and excessive intermetallic compound (IMC) growth in heterogeneous integrated packages. However, the presence of Bi diminishes drop impact reliability, and conventional reflow processes aimed at increasing the Bi mixing ratio exacerbate IMC growth. This study investigates the feasibility of intense pulsed light (IPL) soldering for hybrid solder joints on electroless nickel immersion gold (ENIG) and (electroless nickel electroless palladium immersion gold (ENEPIG) PCB substrates, with the goal of advancing reliable and sustainable electronic packaging technology. Microstructural evolution and drop impact reliability of IPL-soldered joints were compared with those of conventionally reflow-soldered joints. Specifically, IPL soldering exhibited approximately sixfold higher drop impact reliability in ENIG and threefold in ENEPIG compared to reflow soldering under the lowest temperature conditions. This underscores IPL's effectiveness in suppressing interfacial reactions, thereby promoting crack propagation in the SnBi phases. Furthermore, under optimized IPL conditions on the ENEPIG substrate, drop reliability was approximately threefold higher than that achieved under the lowest temperature conditions, despite lower power consumption of 13.36 kWh. These findings demonstrate the potential feasibility of IPL soldering as a reliable and sustainable technology for electronic packages.

Investigating the oxidation behavior of Mg-Zn alloy: Effects of heating rates, gas flow, protective atmosphere, and alloy composition

Magnesium-zinc alloys offer promising lightweight properties but are prone to oxidation during high-temperature processing and usage. In this study, the oxidation behavior of Mg-Zn alloy was examined according to the inert gas type flow rate, heating rate and alloy amount. Initially, alloys were produced by adding zinc at weight percentages of 0.5%, 1.5%, and 2% using the casting method. The alloys were characterized using X-ray fluorescence (XRF), X-ray Diffraction (XRD), and scanning electron microscope (SEM) analyses, revealing the formation of dendritic Mg-Zn intermetallic within the alloy. The oxidation behavior of these alloys was examined via differential thermal analysis (DTA) and thermogravimetric analysis (TGA), considering factors such as heating rate, gas flow rate, type of protective atmosphere, and amount of alloying element. The results indicated that the onset temperature of oxidation decreased with increasing heating rate. The effect of gas flow rate varied depending on the heating rate and the type of gas. Under a nitrogen atmosphere, conditions with a heating rate of 20°C∙min‒1 and a gas flow rate of 5 cm3∙min‒1 resulted in the least oxidation. In an argon atmosphere, a gas flow rate of 5 cm3∙min‒1 was found to be sufficient to prevent oxidation. However, at a gas flow rate of 1 cm3∙min‒1, a heating rate of 20°C∙min‒1 was more effective in preventing oxidation. The alloying element (zinc) likely reduced oxidation, particularly at the 1.5% addition level, possibly due to the formation of intermetallic compounds.

Evolution mechanism of interfacial multi-layer intermetallic compounds and failure behavior in the Al–Au wire bonding

Evolution mechanism of interfacial multi-layer intermetallic compounds (IMCs) and their impact on failure behavior in Al–Au wire bonding after thermal storage and thermal cycle process are investigated. Microstructural analysis shows that multi-layer IMCs form between the Al wire and barrier layer. After thermal storage and thermal cycle process, the Au8Al3 layer transforms into AuAl2, and Au pad transforms to a thicker layer containing Au2Al and AuAl. Thermodynamic analysis indicates that Au8Al3, Au2Al, AuAl, and AuAl2 have increasing stability. Small-size, equiaxed AuAl2 grains form due to high stored energy, while large-size, columnar Au2Al and AuAl grains result from slower reaction rate and limited recrystallization. The stack-like formation of AuAl2 grains is attributed to the balance between driving force and interfacial energy resistance. During thermal storage, thicker IMC layers cause cracking between IMC layers and Au pad, and micro voids form near the IMC layers/barrier layer interface due to Kirkendall effect. Thermal stress results show that plastic deformation of the Al layer slightly affects the thermal stress in other layers during the thermal cycle process. The cyclic stress at the interface with initial cracks ranges from −157 MPa to 114 MPa, facilitating crack propagation. Additionally, micro void grows under cyclic thermal input, weakening interface adhesion. Therefore, bond strength decreases and frequency of bonding lift-off with cracking along the IMC layers/barrier layer interface increases after thermal storage and thermal cycle process. These results provide the guidance for regulating the interfacial IMCs and predicting the thermal stress in Al–Au wire bonding.

Exploring Intermetallic Compounds: Properties and Applications in Catalysis

Intermetallic compounds (IMCs) have attracted significant attention in recent years due to their unique properties and potential applications in various fields, particularly in catalysis. This review aims to provide an in-depth understanding of IMCs, including their synthesis methods, structural characteristics, and diverse catalytic applications. The review begins with an introduction to IMCs, highlighting their distinct features and advantages over traditional catalyst materials. It then delves into the synthesis techniques employed to prepare IMCs and explores their structural properties. Subsequently, catalytic applications of the IMCs are introduced, focusing on the key reactions and highlighting their superior catalytic performance compared to conventional catalysts. Future perspectives for, and challenges to, the catalysis of IMCs are then proposed.

Novel Fe-Mo intermetallic composite synthesized via diffusional-displacive mixed-mode transformation

Transition metal-based intermetallic materials are candidates for high-temperature structural applications. However, they are limited by their low fracture toughness at ambient temperature. Given Fe is a low-cost metal with a low environmental impact, it is necessary to design tough Fe-based intermetallic alloys. We report a novel ferrite-Fe2Mo intermetallic synthesized through arc melting and quenching of Fe0.78Mo0.22 alloy. Diffusional-displacive mixed-mode transformation of the parent ferrite phase resulted in the formation of nanocomposite microstructure. Two distinct microstructure morphologies of the product μ phase were observed: (i) allotriomorphic phase formation at the parent ferrite grain boundaries and (ii) formation of basket-weave Widmanstätten structures at the parent grain interior. Electron probe microanalysis (EPMA) revealed Mo partitioning across ∼800 nm wide Widmanstätten laths, establishing that it is a diffusional-displacive mixed-mode transformation. We performed atom probe tomography (APT) investigations to ascertain the nanoscale Mo solute partitioning. Based on the chemistry of the retained parent ferrite, the Mo partitioning temperature was estimated to be ∼865 °C. Mo partitioned Widmanstätten lath formation is clarified using a shear-assisted diffusional transformation model. APT studies further revealed that the composition of the product μ phase corresponds to stoichiometric Fe2Mo. It is an anomaly since stoichiometric Fe2Mo typically corresponds to λ C14 Laves phase. We explain the mechanism of μ phase formation with Fe2Mo stoichiometry. The nanocomposite exhibits a high hardness (HV2) of 7.54 GPa and excellent toughness (evidenced by resistance to indentation cracking).

Microstructure and mechanical properties of resistance spot welded dissimilar aluminum/steel joints fabricated using high entropy alloy as interlayer

To improve the welding quality of Al/steel joint during resistance spot welding (RSW) process, a CoCrFeNiMn high entropy alloy (HEA) sheet was employed to be an interlayer between aluminum alloy and high strength steel parent metal sheets. Through a series of comparative studies and analyses, the Al/steel spot welded joint obtained from the process with the HEA interlayer had a larger aluminum nugget diameter and thinner intermetallic compound (IMC) layer when compared to a conventional RSW process. When the thicknesses of two parent metal sheets were 1.0 mm or 1.5 mm, the aluminum nugget diameter of the Al/steel spot welded joint with the HEA interlayer were 4.904 mm and 5.962 mm, and respectively increases by 28.41% and 31.32% compared to a conventional RSW process. For the 1.5 mm of the thickness of the parent metal sheets, the HEA interlayer can make the layer thicknesses at the Al/steel faying interface decrease from 3.2 μm to 1.3 μm. Also, adding the HEA interlayer could induce more welding heat energy respectively by 30.74% and 30.34%, and significantly improve the lap-shear strength of the joint by 56.95% and 52.09% for two thicknesses of the parent metal sheets. Even increasing welding current of the process without HEA interlayer to make its calculated welding heat energy the same as that with HEA interlayer, the Al/steel joint obtained from the process with HEA interlayer still had a higher lap-shear strength. In addition, by seriously observing and analyzing the fracture surfaces obtained from processes with and without the HEA interlayer, it could be concluded that the HEA interlayer could improve the fracture mode of the Al/steel joint from interfacial fracture to button fracture, so the quality of the Al/steel joint could be improved. This work can supply an effective method to improve the dissimilar metals welding process.

Influence of Cu and Si on the microstructure and properties of CoCrFeNiCu1-xSix alloys

The effect of Cu and Si on the microstructure and properties of CoCrFeNiCu1-xSix alloys (x = 0, 0.2, 0.5, 0.8 and 1) was studied in this work. The results indicate that as the x value increased from 0 to 1, the phase compositions of CoCrFeNiCu1-xSix alloys evolved from FCC + Cu-rich phases to FCC + Cu-rich + NiSi-rich phases to FCC + BCC + NiSi-rich phases. Therefore, the decrease in Cu content led to the decreasing Cu-rich phase content, whereas Si addition not only favored the formation of intermetallic compounds, but also promoted the phase transition from FCC to BCC. Due to the competition between BCC phase suppressing corrosion and Cu-rich + NiSi-rich phases inducing galvanic corrosion, the corrosion resistance of CoCrFeNiCu1-xSix alloys improved with the increasing x value. The microstructure change also resulted in an improvement in hardness and wear resistance, and a deterioration in fracture toughness of CoCrFeNiCu1-xSix alloys. Moreover, the main wear mechanism evolved from adhesive wear and abrasive wear to slight abrasive wear. Comparison among five alloys indicates that Cu0.2Si0.8 alloy exhibited the excellent comprehensive properties, revealed by the corrosion current density of 4.81 × 10−8 A/cm2, the hardness value of 510.5 HV, the fracture toughness of 8.57 MPa·m1/2 and the wear rate of 0.88 mm3·N−1 · m−1.

Interfacial IMC growth behavior of Sn-3Ag-3Sb-xIn solder on Cu substrate

PurposeThe reliability of solder joints is closely related to the growth of an intermetallic compound (IMC) layer between the lead-free solder and substrate interface. This paper aims to investigate the growth behavior of the interfacial IMC layer during isothermal aging at 125°C for Sn-3Ag-3Sb-xIn/Cu (x = 0, 1, 2, 3, 4, 5 Wt.%) solder joints with different In contents and commercial Sn-3Ag-0.5Cu/Cu solder joints.Design/methodology/approachIn this paper, Sn-3Ag-3Sb-xIn/Cu (x = 0, 1, 2, 3, 4, 5 Wt.%) and commercial Sn-3Ag-0.5Cu/Cu solder were prepared for bonding Cu substrate. Then these samples were subjected to isothermal aging for 0, 2, 8, 14, 25 and 45 days. Scanning electron microscopy and transmission electron microscopy were used to analyze the soldering interface reaction and the difference in IMC growth behavior during the isothermal aging process.FindingsWhen the concentration of In in the Sn-3Ag-3Sb-xIn/Cu solder joints exceeded 2 Wt.%, a substantial amount of InSb particles were produced. These particles acted as a diffusion barrier, impeding the growth of the IMC layer at the interface. The growth of the Cu3Sn layer during the aging process was strongly correlated with the presence of In. The growth rate of the Cu3Sn layer was significantly reduced when the In concentration exceeded 3 Wt.%.Originality/valueThe addition of In promotes the formation of InSb particles in Sn-3Ag-3Sb-xIn/Cu solder joints. These particles limit the growth of the total IMC layer, while a higher In content also slows the growth of the Cu3Sn layer. This study is significant for designing alloy compositions for new high-reliability solders.

Effect of foam interlayer thickness and pore size on the microstructure and properties of brazed joints

Ni foam was introduced as an interlayer to improve the performance of the brazed C/C composite-TC4 titanium alloy joint, and high-quality brazed connections of c/c composites and TC4 were realized. Compared to a brazing joint without foam, the introduction of a foam Ni interlayer can achieve a more uniform bonding interface. The effects of the thickness and pore size of the foam Ni interlayer on the microstructure, mechanical properties and residual stresses of the joints were investigated. With increasing thickness and pore diameter, Ag-based solid solutions and Ti–Cu intermetallic compounds first become more dispersed and smaller at the center of the brazed joints, and then aggregate to become larger. The brazed interface microstructure with a 0.4 mm thick foam Ni interlayer with a pore size of 0.5 mm was more uniform, and the shear strength of the joint reached 21.23 MPa, representing an 85.96 % increase compared to the joint without the foam Ni interlayer. The residual stress and its distribution calculated by finite element method (FEM), and the residual stress of the brazed joint decreased from 467 MPa/-289.53 MPa to 457.96 MPa/-234.98 MPa. These results indicated that the Ni foam could act as a buffer layer to reduce the residual thermal stress, and improve the mechanical properties of C/C composite-TC4 titanium alloy joint.

Experiment investigation and thermodynamic assessment of the ternary Ti–Mo-Hf system

Based on experimental data measured by scanning electron microscope (SEM), X-ray diffraction (XRD) and electron probe microanalysis (EPMA), isothermal sections of Ti–Mo-Hf system at 800 °C and 1000 °C were constructed. Four and three three-phase regions were derived in the isothermal sections at 800 and 1000 °C, respectively. In addition, a new ternary compound named τ was discovered. The maximum solubilities of the three elements, Ti, Mo and Hf in τ were measured at 800 °C and 1000 °C. At the same time, the solid solubilities of Ti in HfMo2_C15 and Mo in Hcp were also obtained. According to the measured experimental data, the Ti–Mo-Hf system was optimized using the CALPHAD (CALculation of PHAse Diagrams) method. The solution phases, liquid, Bcc and Hcp, were treated as substitutional solution, while the intermetallic compounds were modeled using sublattice models. HfMo2_C15 was treated as (Hf, Mo, Ti)1(Hf, Mo, Ti)2. The ternary phase τ was considered as a stoichiometric compound and its thermodynamic modeling was defined as (Ti)3(Mo)3(Hf)14. The calculated results showed good agreement with the experimental phase equilibrium data, leading to the derivation of a set of self-consistent thermodynamic parameters for the Ti–Mo-Hf system.

Nominal CaAl2Pt2 and Ca2Al3Pt – two new Intermetallic Compounds in the Ternary System Ca−Al−Pt

AbstractSingle crystals of CaAl2Pt2, Ca2Al3Pt and Ca2AlPt2 were initially observed in an attempt to synthesize Ca3Al4Pt4. Their structures were determined using single‐crystal X‐ray diffraction experiments. While nominal CaAl2Pt2 (CaBe2Ge2 type, P4/nmm, a=426.79(2), c=988.79(6) pm, wR2=0.0679, 246 F2 values and 18 variables) and Ca2Al3Pt (Mg2Cu3Si type, P63/mmc, a=561.46(5), c=876.94(8) pm, wR2=0.0664, 214 F2 values and 13 variables) exhibit Al/Pt mixing, for Ca2AlPt2 (Ca2Ir2Si type, C2/c, a=981.03(2) b=573.74(1), c=772.95(2) pm, β=101.862(1)° wR2=0.0307, 2246 F2 values and 25 variables) no mixing was observed. Subsequently, the nominal compositions were targeted with synthetic attempts from the elements using arc‐melting and annealing techniques. For CaAl2Pt2 and Ca2Al3Pt always multi‐phase mixtures were observed while Ca2AlPt2 could be obtained as almost X‐ray pure material. Quantum‐chemical calculations were used to investigate the charge transfer in these compounds rendering them polar intermetallics with a designated [AlxPty]δ− polyanion and Caδ+ cations in the cavities of the polyanions.

Quasi-FeCo-MOF/CoS amorphous Nanosheets: A stable and highly active catalyst for electrocatalytic water splitting and monosaccharide oxidation

Quasi-metal organic frameworks (quasi-MOFs) are intermediate materials between pristine MOFs and metal compounds, possessing unusual structures and properties, which makes them promising porous materials. However, their synthesis remains challenging due to the absence of reliable design strategies. Here, we propose a novel solvent-thermal synthesis strategy for preparing quasi-FeCo-MOF/CoS amorphous nanosheet composites. The strategy involves the use of high-coordination metal ions and simple organic ligands, followed by a simple solvent-thermal treatment to induce quasi-MOF formation. The formation of CoS not only transforms the original crystal structure of FeCo-MOF into amorphous nanosheets but also imparts structural stability to the composite material. Furthermore, density functional theory (DFT) calculations reveal the catalytic mechanism, demonstrating that the introduction of CoS can adjust the d-band center of the composite material, optimizing adsorption free energy and reducing its overpotential. This method significantly enhances the electrocatalytic activity of the composite material in alkaline and neutral solutions. Notably, the optimized composite material (FeCo-MOF/CoS-2/FF) exhibits low overpotentials of 142 mV and 55 mV (at 10 mA cm−2) for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively, and achieved a current density of 10 mA cm−2 with a low overpotential of 1.391 V for HER and monosaccharide oxidation (MOR) using FeCo-MOF/CoS-2/FF. This method provides new insights and perspectives for developing highly active and stable catalysts and is expected to advance the development of electrocatalytic water splitting technology.

Enhancement of wear and corrosion resistance of pulsed electrodeposited Ni–Mo amorphous/nanocrystalline coatings by heat treatment

In this study, Ni–Mo coatings with various sodium molybdate concentrations were designed and successfully electrodeposited. The effects of treatment with different temperatures (200 °C,400 °C, 600 °C) on the microstructure and properties of the best-performing coating (4 g/L) were investigated. The surface morphologies, elemental content, and phase structure of the prepared coatings were obtained and analyzed by SEM, EDS, XRD, WFI and TEM. The Ni–Mo coating after heat treatment at 400 °C formed the compact and uniform amorphous/nanocrystalline coating. As shown by the electrochemical and wear test. Heat treatment at 400 °C improved the coating properties, and the corrosion current density was decreased by 66 % to 6.2532 × 10−7 A/cm2. The wear rate reduced from 8.3 × 10−4 mm3/N·m to 3.6 × 10−4 mm3/N·m, and the average friction coefficient minimized to 0.079. Additionally, compared with the as-deposited coating, the microhardness reaches the maximum (1048 HV). The formation of the oxide layer and the intermetallic compound MoNi on the surface of the coating plays a carrying and hindering role, thus the surface of the coating shows excellent wear and corrosion resistance. In addition, the corrosion inhibition mechanism during the heat treatment of Ni–Mo coatings was further explored.