Compressive property and energy absorption characteristic of interconnected porous Mg-Zn-Y alloys with adjusting Y addition

In this study,interconnected porous Mg-2Zn-xY alloys with different phase compositions were prepared by various Y additions(x=0.4,3,and 6 wt.%)to adjust the compressive properties and energy absorption characteristics.Several characterization methods were then applied to identify the microstructure of the porous Mg-Zn-Y and describe the details of the second phase.Compressive tests were performed at room temperature(RT),200℃,and 300℃to study the impact of the Y addition and testing temperature on the compressive properties of the porous Mg-Zn-Y.The experimental results showed that a high Y content promotes a microstructure refinement and increases the volume fraction of the second phase.When the Y content increases,different Mg-Zn-Y ternary phases appear:I-phase(Mg_(3)Zn_(6)Y),W-phase(Mg_(3)Zn_(3)Y_(2)),and LPSO phase(Mg_(12)ZnY).When the Y content ranges between 0.4%and 6%,the compressive strength increases from 6.30MPa to 9.23 MPa,and the energy absorption capacity increases from 7.33 MJ/m^(3)to 10.97 MJ/m^(3)at RT,which is mainly attributed to the phase composition and volume fraction of the second phase.However,the average energy absorption efficiency is independent of the Y content.In addition,the compressive deformation behaviors of the porous Mg-Zn-Y are altered by the testing temperature.The compressive strength and energy absorption capacity of the porous Mg-Zn-Y decrease due to the softening effect of the high temperature on the struts.The deformation behaviors at different temperatures are finally observed to reflect the failure mechanisms of the struts.

Effect of Ca on microstructure and high temperature creep properties of AM60-1Ce alloy

A series of AM60-1Ce-xCa(x=0, 0.5, 1.5, 2.5) magnesium alloys were prepared by gravity casting method and analyzed by means of XRD, DSC and SEM. The effects of Ca on normal temperature mechanical properties and high temperature creep behavior of alloys were characterized by tensile and constant creep test.Microstructure analysis indicated that Ca was preferentially combined with Al in the alloy to form the high melting point Al_2Ca phase at the grain boundary. The addition of Ca can refine the crystal grains and reduces the content of β-Mg_(17)Al_(12) phase. With the increase of Ca content in the alloy, Al_2Ca phases at the grain boundary gradually changed to the network of lamellar structure, and replaced the β-Mg_(17)Al_(12) phase as the main strengthening phase gradually. The creep resistance of the alloy continuously increases because the high-temperature stable phase Al_2Ca firmly nailed at grain boundaries impedes the sliding of grain boundaries. However, when the addition of Ca was more than 1.5%, mechanical properties of the alloy started to decrease, which was probably due to the large amount of irregularly shaped Al_2Ca phases at the grain boundary. Experimental results show that the optimal addition amount of Ca is 1.5 wt.%.

Mn_(x)Co_(3-x)O_(4)Microtubules with Enhanced Catalytic Activity Towards Toluene Combustion:Effects of Redox Property and Oxygen Species

The redox property and oxygen species play an important role in the catalytic oxidation of volatile organic compounds(VOCs).In this paper,a series of Mn_(x)Co_(3-x)O_(4)catalysts with tubular structure were synthesized and applied for the catalytic combustion of toluene.Various characterization technologies were employed to reveal the relationship between the catalytic performance of the Mn_(x)Co_(3-x)O_(4)catalysts and Mn doping.The results of XRD,SEM and N2 adsorption-desorption analyses showed that the Mn doping had significant effects on the structure and morphology of the Mn_(x)Co_(3-x)O_(4)catalysts.The H2-TPR,O2-TPD,and XPS results proved that the strong interaction between Co and Mn resulted in the enhanced Olatt mobility,the richer active oxygen species,and the enhanced redox property in comparison with the pure Co_(3)O_(4)sample,which were crucial to the improvement of the catalytic activity of Co-Mn catalysts.The best catalyst,Co5-Mn5 sample,exhibited a good and stable activity to catalytically oxidize toluene at low temperatures even in the presence of water vapor,indicating that it is a potential material to be used in the commercialization of catalytic abatement of toluene.

Effect of Hot-Plate Rolling on the Microstructure Evolution and Mechanical Properties of In-Situ Nano-TiC_(P)/Al-Mg-Si Composites

The hot-plate rolling(HPR)process is adopted to achieve the optimal strength-ductility for the in-situ nano-TiC_(P)/Al-Mg-Si composites.There was no crack in the sheet by single pass of hot-plate rolling with a thickness reduction of 80%,while there were numerous cracks in the sheet by two passes of conventional hot rolling to achieve a total reduction of 50%.The microstructure and mechanical properties of the composites subjected to 80%thickness reduction of hot rolling at 540℃were investigated by tensile tests,scanning electron microscopy,and electron backscatter diffraction.The yield strength and ultimate tensile strength of in-situ nano-TiC_(P)/Al-Mg-Si composites after the hot-plate rolling process and T6 heat treatment increased significantly due to the dislocation strengthening and precipitation strengthening.

Mechanical behaviors of ZL109/Al_2O_3·SiO_2 particle reinforced composites

The squeeze-casting method is utilized to synthesize ZL109/Al2O3·SiO2 particle reinforced composites with 5%,10%,20%,30%(volume fraction) Al2O3·SiO2 particles,respectively. The microstructures and mechanical behaviors of ZL109/Al2O3·SiO2 particle reinforced composites were studied,and the mechanical properties were tested. The results show that Al2O3·SiO2 particles can be homogeneously distributed on the aluminum matrix in this process. The hardnesses of the composites are higher than that of the Al matrix,and increases with increasing the volume fraction of Al2O3·SiO2 particles. The tensile strengths and elongations of the composites are lower than that of the Al matrix,and decrease with increasing the volume fraction of Al2O3·SiO2 particles. The fracture characteristics of the composites has an obvious change with increasing the volume fraction of Al2O3·SiO2 particles on the fracture section,the toughness dens become smaller and shallower,and the tearing ridges and "rivers" pattern appear. The fracture characteristics of the composites become fragile from ductile with the increase of the volume fraction of Al2O3·SiO2 particles. Elastic moduli of the composites have little change compared with the Al matrix.

Construction of MoP/MoS_(2) Core-shell Structure Electrocatalyst for Boosting Hydrogen Evolution Reaction

Hydrogen energy stands out as one of the most promising alternative energy sources due to its cleanliness and renewability.Electrocatalytic water splitting offers a sustainable pathway for hydrogen production.However,the kinetic rate of the hydrogen evolution reaction(HER)is sluggish,emphasizing the critical need for stable and highly active electrocatalysts to facilitate HER and enhance reaction efficiency.Transition metal-based catalysts have garnered attention for their favorable catalytic activity in electrochemical hydrogen evolution in alkaline electrolytes.In this investigation,flower-like nanorods of MoS_(2) were directly synthesized in situ on a nickel foam substrate,followed by the formation of MoP/MoS_(2)-nickel foam(NF)heterostructures through high-temperature phosphating in a tube furnace environment.The findings reveal that MoP/MoS_(2)-NF-450 exhibits outstanding electrocatalytic performance in an alkaline milieu,demonstrating a low overpotential(90 mV)and remarkable durability at a current density of 10 mA/cm^(2).Comprehensive analysis indicates that the introduction of phosphorus(P)atoms enhances the synergistic effect with MoS_(2),while the distinctive flower-like nanorod structure of MoS_(2) exposes more active sites.Moreover,the interface between the MoP/MoS_(2) heterostructure and NF facilitates electron transfer during hydrogen evolution,thereby enhancing electrocatalytic performance.The design and synthesis of such catalysts offer a valuable approach for the development of high-performance hydrogen evolution electrocatalysts.

Preparation of High-Strength Al–Mg–Si/Al_2O_3 Composites with Lamellar Structures Using Freeze Casting and Pressureless Infiltration Techniques

Lamellar porous alumina scaffolds with the initial solid loadings of 20, 25, and 30 vol% were prepared by freeze casting using 5 μm alumina powders. With the addition of 3 wt% MgO-A1203-SiO2 nanopowders in a eutectic composition as sintering aid, the maximum compressive strength of the sintered scaffolds reached （64 -4- 2） MPa after sintering at 1,773 K for 2 h. The lamellar porous scaffolds were then filled with a molten Al-12Si-10 Mg alloy （in wt%） by pressureless infiltration at 1,223 K in a N2 atmosphere, yielding the shell-like structure of the composites. The compressive strength of the upper part composite with the initial 30 vol% solid loading reached （1,190 ±50） MPa, which was about 3.5 times as large as that of the matrix alloy.

Recent advances of nanoporous metal-based catalyst: synthesis, application and perspectives

Nanoporous metal-based catalysts with the specific bicontinuous interconnected ligaments/pores network exhibit highly active performances in application for energy conversion, which represent a broader trend in the design of catalyst materials. These promising nanomaterials commendably provide highly conductive porous morphologies with reduced contact resistances, large electrochemical surface areas with enhanced catalytic efficiency, and controllable synthesis for regulating the performances. Thus, we highlight recent designs of nanoporous metals, alloys, transition metal compounds and hierarchical structures mainly employed in catalysis process. We discuss applied strategies to utilize characteristics of nanoporous metals in the energetic field of catalytic reactions. Moreover, development and evolution of novel controllable synthesis methods are applied in preparation of nanoporous non-noble metals and transition metal compounds. Finally, we present some outlooks and perspectives on the nanoporous metal catalyst and suggest ways for achieving alternative materials in catalysis applications.

深冷处理对AZ31板冲剪的影响（英文）

冲剪成形作为一种材料加工方法,经常用于加工一些成品零件。深冷处理在改善钢的局部力学性能上有显著效果,但有关深冷处理对镁合金冲剪性能影响的研究较少。本文通过金相组织分析、拉伸、硬度测试和冲剪实验等,分析了深冷处理对AZ31板冲剪性能的影响。结果表明:深冷处理后组织中第二相数量增加,晶粒中出现大量孪晶。同时,AZ31镁合金的抗拉强度,延展性和硬度均得到改善,而屈服强度在深冷处理后有所降低。此外,经深冷处理后的AZ31镁合金板在冲剪过程中,剪切强度降低,圆角半径变化不明显,横截面边缘的毛刺高度降低,光亮带所占比例明显增加。

Mechanical Properties of Vermicular Graphite Cast Iron Processed by Selective Laser Surface Alloying with Ultra-fine ZrO2 Ceramic Particulates

In this work, the mechanical properties and microstructures of vermicular graphite cast iron processed by selective laser surface alloying with ultra-fine ZrO2 ceramic particulates were investigated. A particulate-reinforced metal matrix composite coating with the thickness of -650 μm was fabricated by laser treatment on the sample surface. The particulates were uniformly distributed in the microstructure of the coating. The tensile strength and microhardness both increased with the particulate fraction, since more tensile load was transferred from the matrix to the reinforcement showing essential strengthening effect. The composite coating also sharply reduced the wear mass loss and thus improved the wear resistance.

面向碱性析氢反应的原子级优化Fe-Pt金属间化合物催化剂表面终结态探索

Controlling the atomic arrangement of elemental atoms in intermetallic catalysts to govern their surface and subsurface properties is a crucial but challenging endeavor in electrocatalytic reactions.In hydrogen evolution reaction(HER),adjusting the d-band center of the conventional noble-metallic Pt by introducing Fe enables the optimization of catalytic performance.However,a notable gap exists in research on the effective transition from disordered Fe/Pt alloys to highly ordered intermetallic compounds(IMCs)such as FePt_(3)in the alkaline HER,hampering their broader application.In this study,a series of catalysts FePt_(3-x)H(x=5,6,7,8 and 9)supported on carbon nanotubes(CNTs)were synthesized via a simple impregnation method,along with a range of heat treatment processes,including annealing in a reductive atmosphere,to regulate the order degree of the arrangement of Fe/Pt atoms within the FePt_(3)catalyst.By using advanced microscopy and spectroscopy techniques,we systematically explored the impact of the order degree of FePt_(3)in the HER.The as-prepared FePt_(3)-8H exhibited notable HER catalytic activity with low overpotentials(η=37 mV in 1.0 mol L^(-1)KOH)at j=10 mA cm^(-2).The surface of the L1_(2)FePt_(3)-8H catalyst was demonstrated to be Pt-rich.The Pt on the surface was not easily oxidized due to the unique Fe/Pt coordination,resulting in significant enhancement of HER performance.

Biocompatible DCPD Coating Formed on AZ91D Magnesium Alloy by Chemical Deposition and Its Corrosion Behaviors in SBF

Bioactive calcium phosphate coatings were prepared on AZ91D magnesium alloy in phosphating solution in order to im- prove the corrosion resistance of the magnesium alloy in Simulated Body Fluid （SBF）. The surface morphologies and compo- sitions of the calcium phosphate coatings deposited in the phosphating bath with different compositions were investigated by Scanning Electron Microscopy （SEM） with Energy Dispersive Spectrometer （EDS） and X-ray Diffraction （XRD）. Results showed that the calcium phosphate coating was mainly composed of dicalcium phosphate dihydrate （CaHPO4o2H20, DCPD）, with Ca/P ratio of approximately 1 ： 1. The corrosion resistance was evaluated by acid drop, electrochemical polarization, elec- trochemical impedance spectroscopy and immersion tests. The dense and uniform calcium phosphate coating obtained from the optimal phosphating bath can greatly decrease the corrosion rate and hydrogen evolution rate of AZ91D magnesium alloy in SBE

基于激发依赖性钙钛矿/聚合物薄膜的紫外可视化研究

紫外可视化技术在安全监控、空间通信、物联网健康监测可穿戴设备等领域有着广泛的应用.由于其显著的光电特性,钙钛矿材料被认为是有前途的紫外光探测和成像的候选者.本文报道了具有激发依赖特性的钙钬矿/聚合物薄膜,通过改变紫外激发波长(260~380 nm)实现了从绿色到品红的动态可调荧光显示.通过探究不同聚合物基质、卤素比例和钙钛矿材料的阳离子对动态的多色紫外可视化的影响和理论计算,结果表明其荧光变化机理与钙钛矿材料中的氯空位有关.该钙钛矿/聚合物薄膜还可以通过丝网印刷工艺实现紫外可视化的图案化多色显示.该技术可能应用于物联网的信息安全、紫外可视化和动态多色显示.