Recent advances of Rh-based intermetallic nanomaterials for catalytic applications

Rhodium(Rh)has received widespread attention in fundamental catalytic research and numerous industrial catalytic applications.Compared to homogeneous catalysts,Rh-based nanomaterials as heterogeneous catalysts are much easier to separate and collect after usage,making them more suitable for commercial use.To this purpose,there has been a constant demand in constructing stable and highly active Rh-based nanomaterials.In contrast to Rh-based solid solutions with a random distribution of metallic atoms in the lattice,Rh-based intermetallic compounds(IMCs)with a fixed stoichiometric ratio and an ordered atomic arrangement can ensure the homogenous distribution of active sites and structural stability in the catalytic process.In this review,we concentrate on the fabrication of Rh-based IMCs for catalytic applications.Various synthetic methods and protocols for the controlled preparation of Rh-based IMC are illustrated.Meanwhile,the catalytic applications and corresponding catalytic mechanisms are discussed.In addition,personal perspectives about the remaining challenges and prospects in this field are provided.We believe this review will be useful in directing the development of Rh-based IMC catalysts for heterogeneous catalysis.

High-entropy intermetallics:from alloy design to structural and functional properties

Conventional intermetallics are strong but brit-tle.However,multi-principal element intermetallics,also termed as high-entropy intermetallics(HEIs)in the recent high-entropy alloy literature,are strong but malleable,some of which even show appreciable ductility and fracture toughness at room temperature.In this article,we provide a focused review on the recent researches on HEIs,from the fundamentals,such as the concept of HEIs,the formation rules to the structural and functional properties of HEIs.The results hitherto reported clearly show that the HEIs with distinct properties could be a promising material for future structural and functional applications.

Deteriorated corrosion performance of micro-alloyed Mg-Zn alloy after heat treatment and mechanical processing

The corrosion performances of the as-cast and solution-treated Mg-0.5Zn samples were investigated in 0.9%Na Cl solution and compared.From the electrochemical measurement results and corrosion morphology observations,it is found that the corrosion resistance of Mg-0.5Zn deteriorated with the extension of solution treatment duration.The main reason was the formation of Fe-Si precipitates with higher Fe concentrations during heat treatment.The Fe-Si precipitates,especially the ones with high Fe contents influenced the corrosion initiation and propagation significantly.In regard of corrosion performance,the solution-treated and then extruded sample was also performing not as good as the cast and then directly extruded sample.

Unveiling the Growth Mechanism of Faceted Primary Al_(2)Cu with Complex Morphologies During Solidification

The growth characteristic of primary faceted Al_(2)Cu intermetallic compounds(IMCs)during solidification was observed directly by synchrotron radiography.The formation and transition mechanisms of Al_(2)Cu IMCs with diverse morphologies were elucidated by first-principle calculations combined with electron backscatter diffraction analysis.The Al_(2)Cu crystals preferred to grow along the[001]direction and were bounded by{110}planes with the lowest surface energy.The faceted Al_(2)Cu rod-like clusters consisted of multiple crystals with complete rod,hollowness and partial sides,which was attributed to the increase in strain energy and solute redistribution during solidification.The faceted Al_(2)Cu with branches was characteristic with the perpendicular relationship between the main branches and side steps and partial coalescence at the junction,which was ascribed to the continuous propagation and growth of newly formed crystals along the diagonal direction.

3D morphological evolution and growth mechanism of proeutectic FeAl_(3) phases formed at Al/Fe interface under different cooling rates

The 3D morphologies and growth mechanisms of proeutectic FeAl_(3) at the Al/Fe interface under different cooling rates were studied by synchrotron X-ray tomography.With increasing cooling rate,FeAl_(3) crystals developed from faceted polygonal prism,plates with flat surface,thin ribbon-like with periodic undulating surface to non-faceted rods with radial dendrites in cross section,indicating a gradual interface growth mode transition from two-dimensional layer growth to continuous growth.At a higher cooling rate,twinning mechanism plays a leading role in the formation and growth of FeAl_(3).A link between the morphologies,twinning and crystallographic structure was established based on quantitative analyses on the 3D structures.

Analyzing the Effects of Milling and Sintering Parameters on Crystalline Phase Evolution and Mechanical Properties of Al_(86)Ni_(8)Y_(6) and Al_(86)Ni_(6)Y_(4.5)Co_(2)La_(1.5) Amorphous Ribbons

In the present study,Al_(86)Ni_(8)Y_(6) and Al_(86)Ni_(6)Y_(4.5)Co_(2)La_(1.5) bulk amorphous nanocomposites were synthesized by spark plasma sintering of milled melt spun ribbon particles.The as-cast ribbons were of near amorphous nature with minute amount of FCC Al embedded in the amorphous matrix.Milling of the ribbons resulted in partial devitrifi cation due to mechanical crystallization.The milled ribbon particles were sintered in the temperature and pressure range of 300-500℃ and 500-700 MPa,respectively.It was observed that nominal amount of amorphous phase was retained at 500℃ and 500 MPa.With increase in sintering pressure and decrease in sintering temperature,the amount of crystalline phase evolution decreased,and maximum amount of amorphous phase was retained at 300℃ and 700 MPa.The microstructure consisting of amorphous phase embedded with hard intermetallic phases led to increase in the nanohardness of Al_(86)Ni_(8)Y_(6) and Al_(86)Ni_(6)Y_(4.5)Co_(2)La_(1.5) as-cast ribbons from 3.26±0.59 GPa and 3.81±0.58 GPa to 6.06±0.70 GPa and 6.14±0.82 GPa,respectively,for the corresponding consolidated amorphous nanocomposite.Microhardness of the three and five component system bulk samples was 4.19±0.13GPa and 3.6±0.13 GPa,respectively.

Structure and magnetic properties of YCo5 compound at high pressures

The crystal structure and magnetic properties of YCo5 compound have been studied by neutron diffraction,in the pressure range 0≤p≤7.2 GPa.The cobalt moments decrease with pressure,parallelly with anisotropic changes of lattice parameters.The experimental data are analyzed together with results from the combined Density Functional and Dynamical Mean-Field Theory.A rather good agreement between the experimentally determined and calculated values of cobalt moments is shown.Our scenario for the behavior of YCo5 under pressure,is the combined action of the Lifshitz transition with a strong local electron-electron interaction.