Effects of heat treatment on microstructure and mechanical properties of SLMed Sc-modified AlSi10Mg alloy

The influence of heat treatments on the microstructures and mechanical properties of the selective laser melting manufactured AlSi10Mg alloy modified with Sc was systematically investigated. The results showed that the addition of Sc element introduced primary Al₃ Sc, which increased the heterogeneous nucleation during the solidification of AlSi10Mg alloy, and then the ultrafine network eutectic structure was obtained, and hence the tensile strength was improved significantly(nearly 2...     

Creep behavior and dislocation mechanism of Ni3Al based single crystal alloy IC6SX at 760℃

The creep behavior and dislocation mechanism of Ni₃Al-based single crystal alloys IC6 SX with crystal orientation[001] which was prepared by seed crystal method under the testing conditions of 760℃/500 MPa,760℃/540 MPa and 760℃/580 MPa were investigated. The experimental results showed that the creep properties,dislocation morphology and mechanism of this alloy were different under different stress conditions. With the stress increasing from 500 MPa to 580 MPa, the creep life decrease...     

Large specific surface area S-doped Fe–N–C electrocatalysts derived from Metal–Organic frameworks for oxygen reduction reaction

It is highly desired but challenging to develop platinum group metal-free electrocatalysts for oxygen reduction reaction (ORR), which can promote the commercialization of fuel cell technology. To achieve this target, we report a one-step doping method to prepare S-doped Fe–N–C catalysts using zeolite imidazole framework (ZIF-8) and iron (III) thiocyanate (Fe(SCN)₃) as precursor. Different from conventional doping approach, i.e. physical mixing, Fe(SCN)₃ is in-situ added during ZIF-8 formation which would encapsulate Fe(SCN)₃ molecules inside ZIF-8 to avoid structure destruction and create potential replacement of Zn ions by Fe ions to form uniform Fe–N₄ complexes. As a result, the prepared S-doped Fe–N–C catalysts own large specific surface areas with a maximum value of 1326 ​m² ​g⁻¹ and a dual-scale porous structure that benefits mass transport. Significantly, the composition-optimized catalyst exhibits superior ORR activity in both 0.1 ​M HClO₄ electrolyte and 0.1 ​M KOH electrolyte, in which the half-wave potential reaches 0.81 ​V and 0.92 ​V (vs. RHE), respectively. Remarkable stability is also attained, which loses 2 ​mV only after 10000 potential cycles in O₂-saturated 0.1 ​M HClO₄ and remains almost constant in O₂-saturated 0.1 ​M KOH, surpassing commercial Pt/C catalyst in both acidic and alkaline medium.     

Magnetic field induced synthesis of (Ni,Zn)Fe2O4 spinel nanorod for enhanced alkaline hydrogen evolution reaction

Recently, the introduction of external fields(light, thermal, magnetism, etc.) during electrocatalysis reactions gradually becomes a new strategy to modulate the catalytic activities. In this work, an external magnetic field was innovatively employed for the synthesis progress of(Ni, Zn)Fe₂O₄spinel oxide(M-(Ni, Zn)Fe₂O₄). Results indicated the magnetic field(≤250 m T) would affect the morphology of catalyst due to the existing Fe ions, inducing the M-(...     

Near-microscopic grain boundary facilitates fatigue crack propagation in a polycrystalline Al–Zn–Mg–Cu alloy

In present study, grain characteristics with sizes within 10–30 μm were fabricated from a same Al–Zn–Mg–Cu alloy, FCP behaviors of the alloys with small grain(SG alloy), medium grain(MG alloy) and large grain(LG alloy)were investigated and related fatigue fracture morphology was analyzed. With the enhancement of stress intensity factor range(ΔK), the alloy with larger grains possessed faster FCP rate, which were successively arranged as SG alloy > MG alloy > LG alloy at initial stage while...     

Towards understanding the influence of Mg content on phase transformations in the La3-xMgxNi9 alloys by in-situ neutron powder diffraction study

The present work is focused on the studies of the phase-structural transformations in the La_3-xMg_xNi₉ (x = 1.0, 1.1 and 1.2) alloys as active materials of negative electrodes in the Nickel-Metal Hydride(Ni/MH) batteries. The phase equilibria and phase-structural transformations in the alloys were probed by in situ neutron powder diffraction(NPD) at the temperatures ranging from 300 K to 1273 K using the measurements of the equilibrated alloys at 8 setpoint temper...     

Effect of carbon addition on microstructure and mechanical properties of a typical hard-to-deform Ni-base superalloy

In this paper, the as-cast microstructure, microsegregation, and mechanical properties of GH4151 superalloys with a carbon addition were studied by scanner electron microscopy(SEM), transmission electron microscope(TEM), electron probe microanalysis(EPMA), differential thermal analyzer(DSC), and electron backscattered diffraction(EBSD). The results show that the solid solution effect of carbon in alloys is limited, the addition of C from 0.01 to 0.08 wt% significantly refines the secondary dendr...     

Ameliorating mechanical properties and reducing anisotropy of as-extruded Mg-1.0Sn-0.5Ca alloy via Al addition

Effects of Al addition to a Mg–Sn–Ca ternary alloy on its microstructure and tensile properties after extrusion were studied via extrusion of Mg-1.0 Sn-0.5 Ca-x Al(x = 0, 0.8, 2.4 wt%) sheets and analysis of the extruded materials.The results showed that Al addition not only refined the grain size(from 9.8 ± 0.7 μm to 8.3 ± 0.4 μm and7.6 ± 0.5 μm) but also accelerated the generation of more second phase(from 0.98 to 1.72 and 4.32%). Except for the CaMgSn and Mg₂Ca in Mg-1.0Sn-0.5 Ca a...     

Microstructure and electrical conductivity of 10% Yb-doped SrCeO3 ceramics

As a candidate material for hydrogen separation, Yb-doped SrCeO₃ has attracted increasing attention in recent decades. In the present study, Yb-doped SrCe_0.9Yb_0.1O_3-α ceramics were prepared by the dry pressing and sintering approach, with the microstructure evolution and the micro morphology investigated. It was indicated that the ceramics sintered in air were of a pure perovskite structure, and that the sintering temperature had a significant effect on the growth of ceramic grains. The average grain size increased from 1 ​μm to 10 ​μm with an increase in sintering temperature from 1300 to 1500 ​°C. Further investigation of the thermodynamics and kinetics of grain growth revealed that the grain boundary diffusion was the main driving force of grain growth during solid phase sintering, with a grain growth index of 4 and an activation energy of approximately 61.23 ​kJ ​mol⁻¹. These results illustrate an obvious tendency of grain size growth. By electrochemical workstation with different atmospheres the effects of sintering temperature on the conductivity were characterized in the temperature range of 700–900 ​°C. The electrical conductivities σ of SrCe_0.9Yb_0.1O_3-α ceramics in different atmospheres were as follows: σ(wet hydrogen) ​> ​σ(dry hydrogen) ​> ​σ(dry air) ​> ​σ(wet air). In the test atmosphere containing water and hydrogen the conductivity of protons increased with increasing temperature because of the protons jump between lattices in the form of interstitial hydrogen ions or bare protons.     

Li3N film modified separator with homogenization effect of lithium ions for stable lithium metal battery

Lithium metal anode with high theoretical capacity is considered to be one of the most potential anode materials of the next generation. However, the growth of lithium dendrite seriously affects the application of lithium metal anode and the development of lithium metal batteries(LMBs). Herein, an ultrathin Li₃N film modified separator to homogenize the lithium ions and protect the lithium metal anode was reported. Due to the intrinsic properties of Li₃N, the functional sep...     

Spectroscopic properties of Er3+/Ho3+/Tm3+ doped α-SiAlON ceramics under 793 ​nm excitation

This paper reports the first demonstration of super broadband infrared downshifting emission extending from 1640 ​nm to 2200 ​nm with the full width at half maximum of ∼ 417 ​nm in lanthanides (Er³⁺, Ho³⁺, and Tm³⁺)-doped α-SiAlON ceramics upon 793 ​nm excitation. Using α-Si₃N₄ ceramic as a precursor the lanthanides-doped α-SiAlON ceramics were synthesized by the hot-press method. The lanthanides induced no significant secondary phases in the sintered α-SiAlON ceramics. Strong two-photon upconversion emission bands centered at 547, 671 and 694 ​nm have also been observed upon 793 ​nm excitation. The time-resolved measurements of the upconversion emissions confirm that the efficient energy transfer among the Er³⁺, Ho³⁺ and Tm³⁺ ions as well as the ground state absorption in Er³⁺ and Tm³⁺ are responsible for the observed spectroscopic properties.     

Flexible free-standing polyaniline/poly(vinyl alcohol) composite electrode with good capacitance performance and shape memory behavior

The increasing demand for portable and flexible energy storage devices drives the development of flexible electrodes and electrolytes. The aim of this work is to fabricate the flexible free-standing polyaniline/poly(vinyl alcohol)(PANI/PVA) composite electrode with good capacitance performance and shape memory behavior. The electrodes were fabricated by chemical oxidation polymerization of aniline in porous PVA(P-PVA) films. The morphology, electrochemical and mechanical properties of PANI/P-PVA...     

A novel graphite/phenolic resin bipolar plate modified by doping carbon fibers for the application of proton exchange membrane fuel cells

In this study, the carbon fibers treated by three methods were selected as a reinforcement to investigate the influence on the properties of composite bipolar plates. The properties and microstructure of the composite bipolar plate were characterized by the four-point probe, universal test machine, contact angle tester and scanning electron microscopy. The optimum treatment methods and the fiber content were analysed. The results showed that the carbon fibers treated by Fenton reagent for 2 ​h exhibited the best performance, which could improve the electrical conductivity and the flexural strength for composite bipolar plate. Besides, the optimal content content of carbon fibers treated by Fenton reagent was 4%. The maximum power density of the PEMFC with the composite bipolar plates could reach 662.75 ​mW ​cm⁻² in H₂-air conditions. Therefore, the phenolic resin/graphite composite bipolar plate modified by doping carbon fibers was a promising candidate for bipolar plate materials for PEMFC.     

Nanoengineered polypeptides from tetraphenylethylene-functionalized N-carboxyanhydride: Synthesis,self-assembly and intrinsic aggregation-induced emission

Ring-opening polymerization of N-carboxyanhydrides(NCAs) bearing pendant groups creates functional polypeptides. In this paper, we report the design, synthesis and polymerization of tetraphenylethylene(TPE)-modified NCA, which is used to incorporate aggregation-induced emission(AIE)-active segments into polypeptides. Specifically, we attempted the synthesis of amphiphilic methoxy poly(ethyleneglycol)-block-poly(γ-benzyl-L-glutamate)-block-poly(γ-4-(1,2,2-triphenylvinyl)benzyl-L-glutamate)(PEG-PB...     

Effect of Mn content on the microstructure and mechanical properties of Mg–6Li–4Zn-xMn alloys

The as-cast Mg–6Li–4Zn-x Mn alloys were prepared and extruded at 280℃ with an extrusion ratio of 25:1. The effects of Mn content on the microstructure and mechanical properties of Mg–6Li–4Zn-x Mn alloys were investigated in this study. The XRD results show that Mg–6Li–4Zn–x Mn alloys consisted of α-Mg(hcp) + β-Li(bcc)duplex structured matrix, Mg Li₂Zn and Mn phases. The grains of the extruded Mg–6Li–4Zn–x Mn alloys were refined by dynamic recrystallization during the extrusion process...     

Mechanical behaviors of extruded Mg alloys with high Gd and Nd content

The influence of alloying elements and heat treatment on the microstructure and mechanical behaviors of extruded Mg–Gd–Nd ternary alloys was investigated in this study. The grain sizes dramatically decreased after extrusion, and the particles which distributed in Mg matrix had great effect on the grain size. The grain sizes of extruded alloys decreased from 26 to 5 μm with the alloying content increasing. The mechanical test results show that both Gd and Nd had positive effect on the hardness, y...     

Corrosion resistance and thermal stability of sputtered Fe44Al34Ti7N15 and Al61Ti11N28 thin films for prospective application in oil and gas industry

Fe-and Al-based thin-film metallic glass coatings (Fe₄₄Al₃₄Ti₇N₁₅ and Al₆₁Ti₁₁N₂₈) were fabricated using magnetron co-sputtering technique, and their corrosion performances compared against wrought 316L stainless steel. The results of GI-XRD and XPS analyses demonstrated amorphous structure and oxide layer formation on the surface of the fabricated thin films, respectively. The potentiodynamic (PD) polarization test in chloride-thiosulfate (NH₄Cl ​+ ​Na₂S₂O₃) solution revealed lower corrosion current (I_corr) (0.42 ​± ​0.02 ​μA/cm² and 0.086 ​± ​0.001 ​μA/cm² Vs. 0.76 ​± ​0.05 ​μA/cm²), lower passivation current (I_pass) (1.45 ​± ​0.03 ​μA/cm² and 1.83 ​± ​0.07 ​μA/cm² Vs. 1.98 ​± ​0.04 ​μA/cm²), and approximately six-fold higher breakdown potential (E_bd) for Fe- and Al-based coatings than those of wrought 316L stainless steel. Electrochemical Impedance Spectroscopy (EIS) of both films showed 4- and 2-fold higher charge transfer resistance (R_ct), 7- and 2.5-times higher film resistance (R_f), lower film capacitance values (Q_f) (10 ​± ​2.4 ​μS-s^acm^-2, and 5.41 ​± ​0.8 ​μS-s^acm^-2 Vs. 18 ​± ​2.21 ​μS-s^acm^-2), and lower double-layer capacitance values (Q_dl) (31.33 ​± ​4.74 ​μS-s^acm^-2, and 15.3 ​± ​0.48 ​μS-s^acm^-2 Vs. 43 ​± ​4.23 ​μS-s^acm^-2), indicating higher corrosion resistance of the thin films. Cyclic Voltammetry (CV) scan exhibited that the passive films formed on the Fe- and Al-based coatings were more stable and less prone to pitting corrosion than the wrought 316L stainless steel. The surface morphology of both films via SEM endorsed the CV scan results, showing better resistance to pitting corrosion. Furthermore, the thermal analysis via TGA and DSC revealed the excellent thermal stability of the thin films over a wide temperature range typically observed in oil-gas industries.     

Hydrogen absorption-desorption cycle decay mechanism of palladium nanoparticle decorated nitrogen doped graphene

As a hydrogen storage material, palladium nanoparticle decorated nitrogen doped graphene (Pd/N-rGO) has drawn much attention owing to its high absorption capacity at moderate conditions. However, its hydrogen absorption-desorption cycle performance, which is essential for their practical application, has been rarely studied. In this paper, a simple and convenient high temperature thermal reduction method was used to synthesize nitrogen-doped graphene decorated with Pd nanoparticles (Pd/N-rGO). Taken it as a representative, the hydrogen absorption-desorption cycle performance of Pd/N-rGO was investigated. The results showed that after three cycles the hydrogen storage capacity dropped from 2.9 ​wt% to 0.8 ​wt% at 25 ​°C and 4 ​MPa pressure. It was found that the palladium nanoparticles shed from Pd/N-RGO sheet after cycle performance test, and then agglomerated. These phenomena will weaken the hydrogen spillover effect, leading to the decrease of hydrogen storage capacity. Meanwhile, decreased defects reduce the hydrogen absorption sites, which will thus deteriorate the hydrogen storage capacity.     

Effect of initial orientation on microstructure and mechanical properties of AZ31 Mg alloy sheets via accumulated extrusion bonding

In this study, effects of initial orientation on microstructure evolution and mechanical properties of AZ31 Mg alloy sheets via accumulated extrusion bonding(AEB) was systematically studied. The samples with RD and TD parallel to extrusion direction(ED) were labeled as RED and TED, respectively. RD and TD pieces alternately stacked was named as RTED. The results revealed that under three-dimensional compressive stress, {10-12} tensile twinning dominated the first stage deformation in container. ...     

纵向耦合谐振滤波器旁瓣抑制的改进

介绍了一种在石英基片上两端对纵向耦合谐振滤波器阻带抑制的方法，一般纵向耦合谐振器的频率响应有旁瓣较高的缺点，影响其实际应用．分析这些旁瓣形成的原因后，引入了hiccup结构，它改变换能器指条结构分布，并且对指条进行了不同方式的加权，这种结构有利于多方面调节滤波器的结构参数，对其频响进行细微的控制和调整，运用耦合模理论对纵向谐振模式进行了分析，在计算机上这种结构的滤波器特性作了模拟，理论计算表明器件响应中部分旁瓣得到了有效的抑制，实验结果证明了理论分析的准确性与实用性。