Microstructures and mechanical properties of Ti−Al−V−Nb alloys with cluster formula manufactured by laser additive manufacturing

Ti−Al−V−Nb alloys with the cluster formula,12[Al−Ti_(12)](AlTi_(2))+5[Al−Ti1_(4)](V,Nb)2Ti,were designed by replacing V with Nb based on the Ti−6Al−4V alloy.Single-track cladding layers and bulk samples of the alloys with Nb contents ranging from 0 to 6.96 wt.%were prepared by laser additive manufacturing to examine their formability,microstructure,and mechanical properties.For single-track cladding layers,the addition of Nb increased the surface roughness slightly and decreased the molten pool height to improve its spreadability.The alloy,Ti−5.96Al−1.94V−3.54Nb(wt.%),exhibited better geometrical accuracy than the other alloys because its molten pool height was consistent with the spread layer thickness of the powder.The microstructures of the bulk samples contained similar columnar β-phase grains,regardless of Nb content.These grains grew epitaxially from the Ti substrate along the deposition direction,with basket-weaveα-phase laths within the columnar grains.Theα-phase size increased with increasing Nb contents,but its uniformity decreased.Along the deposition direction,the Vickers hardness increased from the substrate to the surface.The Ti−5.96Al−1.94V−3.54Nb alloy exhibited the highest Vickers hardness regardless of deposition position because of the optimal matching relationship between theα-phase size and its content among the designed alloys.

Copper-indium bimetallic catalysts for the selective electrochemical reduction of carbon dioxide

Copper-indium bimetallic catalysts with a dendritic structure are fabricated by a two-step electrodeposition method using a hydrogen evolution template for the CO2 electroreduction reaction(CO2RR).The dendritic Cu-In-30 catalyst electrodeposited for 30 min shows the highest specific surface area and exposes the most active sites,resulting in improved CO2RR activity.The dendritic Cu-In-30 catalyst exhibits distinctly higher formate partial current density(42.0 m A cm^-2)and Faradaic efficiency(87.4%)than those of the In-30 catalyst without the dendritic structure(the formate partial current density and Faradaic efficiency are 4.6 m A cm^-2 and 57.0%,respectively)at-0.85 V vs.reversible hydrogen electrode,ascribed to the increased specific surface area.The Cu-In-30 catalyst can maintain stable performance for 12 h during the CO2RR.In addition,the intrinsic current density of Cu-In-30 with the dendritic structure(4.8 m A cm^-2)is much higher than that of In-30 without the dendritic structure(2.1 m A cm^-2),indicating that the dendritic structure promotes the CO2RR,possibly due to additional coordination unsaturated atoms.

Catalytic upgrading of ethanol to butanol over a binary catalytic system of FeNiO_x and LiOH

Catalytic conversion of ethanol to butanol is vital to bridge the gap between huge amounts of ethanol production,the limited blending ratio of ethanol in gasoline,and the outstanding performance of butanol.In this work,a highly active binary catalytic system of FeNiOx and LiOH was developed for upgrading of ethanol to butanol.After 24 h reaction at 493 K,the selectivity to butanol reached 71% with>90% high carbon alcohols at 28% ethanol conversion,which was comparable to the performance of some noble metal homogeneous catalysts.

基于不同α/β团簇式比例的Ti-Al-V合金的铸态组织和力学性能

在课题组前期工作基础上,设计并铜模吸铸了满足α-{[Al-Ti_(12)](AlTi_(2))}_(17-n)+β-{[Al-Ti_(14)](V_(2)Ti)}n团簇式的合金系列,通过改变β相团簇式的个数n,获得组织覆盖α到β的Ti-(3.19~7.45)Al-(0~12.03)V系列合金,进而表征了铸态组织和室温拉伸力学性能。结果表明,随着n增加,铸态组织由单一α(α'马氏体)经双相态直到单相β,α'马氏体形态由板条状逐渐转变为细片状和针状,当n=5时开始出现β相,n=8时α'马氏体数量最多且呈针状,当n=12时α相完全消失,形成单一β相。相应地,合金强度呈先上升而后下降的趋势,塑性变化趋势则相反,这源自细小针状α'马氏体提升强度而降低塑性的作用。当n=8时,合金的强度达到最大(比Ti-6Al-4V提高了90 MPa),抗拉强度约为1019 MPa、屈服强度约为867 MPa、延伸率与Ti-6Al-4V持平(约为4%),尤其是比强度和比硬度均优于Ti-6Al-4V,达到了230 kN·m/kg和0.76 GPa·cm^(3)/g,分别提升了9%和5%。