查看更多>>摘要：Electrocatalysts for oxygen reduction reactions (ORR) and oxygen evolution reactions (OER) are highly crucial and challenging toward the energy storage and conversion technologies such as fuel cells,metal-air batteries and water electrolysis.To replace noble-metal based catalysts and boost catalytic performance of carbon-based materials,we initially develop the nickel,phosphorus,sulfur and nitrogen co-modified mesoporous carbon (NiPS3@NMC) as a bifunctional oxygen electrocatalyst.The performance for ORR (half-wave potential at 0.90 V) and OER (10 mA cm-2 at 1.48 V) surpasses those of Pt/C coupled with lrO2 catalysts and most of the non-precious metal based bifunctional electrocatalysts reported in related literature.Moreover,the electrochemical durability is also confirmed by accelerated durability tests (ADTs) and long-term chronoamperometry (CA) tests.We demonstrated that the interfacial effect between NiPS3 quantum sheets (QSs) and NMC substrates by thermal activation contributed to the enhanced oxygen electrode bifunctionality with more active sites,due to the electrons-donating from nickel,phosphorus and sulfur elements and relatively enriched pyridinic type N.Such excellent overall performance highlights the potential application of NiPS3 QSs and NMC composites as the materials on energy conversion and storage.
查看更多>>摘要：Phase structure of sputtered Ta coating in the negative glow space and LPH effect were explored.The whole coating/substrate system is substrate → physically gas-absorbed Fe surface → oxygen-enriched TaOx layer → amorphous Ta → α and β dual phase → single α phase.After LPH course,microstructure of Ta coating shows intact,only a few cracks emerge after 100 laser pulses,exhibiting thin HAZ but thick Fe/Ta ICZ,without martensitic transformation.For the electrodeposited Cr coating,continuous thermal stresses produce many extra micro-crack,substrate oxidation and martensitic transformation,leading to crack propagations and final bulk delamination,without any ICZ.
查看更多>>摘要：Direct alloying is difficult to be realized in an immiscible Mo-Ag system with a positive formation heat due to the absence of thermodynamic driving force at equilibrium.In this work,a direct alloying method is developed to realize the direct alloying between Mo and Ag and construct Mo-Ag interface.The direct alloying method was mainly carried out through a direct diffusion bonding for Mo and Ag rods at a temperature close to the melting point of Ag (TmAg).Then the microstructure and phase constitution of the as-constructed Mo-Ag interface are characterized.The results show that Mo-Ag metallurgical bonding interface has been constructed successfully,indicating that a direct alloying in the immiscible Mo-Ag system has been realized.Additionally,mechanical tests are carried out for the Mo-Ag joints prepared through the direct alloying method.The test results show that the average maximum tensile strength of the joints is about 107 MPa.The effect of alloying parameters on the tensile strength is also discussed,which shows that there is an effective temperature range for the direct alloying between Mo and Ag.Lastly,an improved thermodynamic model that considers the formation of Mo-Ag crystalline and amorphous phase is presented to reveal the thermodynamic mechanism of the direct alloying.Combining the calculation and differential scanning calorimetry (DSC) tests results,the Gibbs energy diagram for the direct alloying is obtained.It is confirmed that the co-release of storage energy and surface energy can serve as the thermodynamic driving force to overcome the effect of positive formation heat and lead to direct alloying for Mo-Ag systems.
查看更多>>摘要：The steels with excellent strength and ductility are expected to be achieved by tailoring the microstructural features.In this work,laminate dual-phase (DP) steels with high martensite content (laminate HMDP steels) were produced by a combination of warm rolling and intercritical annealing.Influence of rolling strain and annealing temperature on the microstructural evolution and mechanical properties of laminate HMDP steels were systematically studied.The strength of HMDP steels was significantly improved to ～1.6 GPa associated with a high uniform elongation of 7％,as long as the laminate structure is maintained.The strengthening and ductilizing mechanisms of laminate HMDP steels are discussed based on the influence of laminate structure and the high martensite content,which promote the development of internal stresses and can be correlated to the Bauschinger effect as measured by the cyclic loadingunloading-reloading experiments.Detailed transmission electron microscopy (TEM) observation was applied to characterize the dislocation structure in the deformed ferrite.
查看更多>>摘要：The formation of fine,non-dendritic equiaxed grains throughout a casting without the addition of refiners (i.e.independent of alloy chemistry),is made possible by using ultrasonic,magnetic or pulsed magnetic and electric current pulse techniques.The dominant mechanisms proposed for the grain refinement produced during the application of an external field are cavitation phenomena assisted nucleation or fragmentation of dendrites (ultrasonic field),wall crystals arising from the cold surface of the mould (electric current pulse,magnetic and pulsed magnetic fields).In all these cases fluid flow provides an additional contribution (e.g.reduced temperature gradients,growth rate and remelting of dendrites) to maintaining an equiaxed grain structure.The origin of equiaxed grains under an external field also depends on the casting conditions (volume and shape of casting) and the type of alloy other than the mechanisms specific to a particular technique.The current work aims to provide a detailed understanding of the various factors and mechanisms that influence the grain refinement achieved during the solidification of pure metals (magnesium and zinc) subjected to UltraSonic Treatment (UST).The role of the temperature range of UST application,time duration and an unpreheated sonotrode are examined with respect to the origin,evolution of equiaxed grain structure,morphology and the columnar to equiaxed transition.The origin of grains was analysed from three fundamental aspects that contribute to refinement (i) heterogeneous nucleation (ii) fragmentation of existing dendrites and (iii) grains produced from the colder surfaces (arising from mould walls or vibrating surfaces as wall crystals).A comparison of UST refinement with mechanical,low-frequency vibration,electric current pulse and magnetic field solidification of pure metals has also been provided to highlight the importance of the cold surfaces (sonotrode and mould wall) in influencing grain refinement.
查看更多>>摘要：The correlation betweent deformation behavior and atomic-scale heterogeneity of bulk metallic glasses (BMGs) is critical to understand the BMGs' deformation mechanism.In this work,three typical[(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4,Fe39Ni39B14.2Si2.75P2.75Nb2.3,and Fe50Ni30P13C7 BMGs exhibiting different plasticity were selected,and the correlation between deformation behavior and atomic-scale hetero-geneity of Fe-based BMGs was studied.It is found that the serrated flow dynamics of Fe-based BMGs transform from chaotic state to self-organized critical state with increasing plasticity.This transformation is attributed to the increasing atomic-scale heterogeneity caused by the increasing free volume and short-to-medium range order,which facilitates a higher frequency of interaction and multiplication of shear bands,thereby results in a brittle to ductile transition in Fe-based BMGs.This work provides new evidence on heterogeneity in plastic Fe-based BMGs from the aspects of atomic-scale structure,and provides new insight into the plastic deformation of Fe-based BMGs.
查看更多>>摘要：Localized deformation and corrosion in irradiated 304 nuclear grade stainless steel in simulated primary water were investigated.The investigation was conducted by comparing the deformation structure,the oxide scale formed at the deformation structure,and their correlation with cracking.The results revealed that increasing the irradiation dose promoted localized corrosion at the slip step and grain boundary,which was primarily attributed to the strain concentration induced by enhanced localized deformation and depletion of Cr at grain boundary.Further,a synergic effect of the enhanced localized deformation and localized corrosion at the slip step and grain boundary caused a higher cracking susceptibility of the irradiated steel.
查看更多>>摘要：Luminescence materials have shown promise as display apparatus and lighting devices.The particularly interesting systems are photoluminescence materials that are capable of reversible colors emitting repeatedly on exposure to light.Here we report a series of color tunable flexible and transparent photoluminescence films consisting of multi-metals (Eu3+,Tb3+ and Zn2+) induced polymer aggregates (MIPAs) which are distributed uniformly in the polyacrylonitrile (PAN) films without agglomeration.MIPAs have a unique spherical structure due to the self-assembly of polystyrene-block-polyacrylic acid (PS-b-PAA) induced by metal ions.Notably,when applied in photoluminescence devices,these photoluminescence films exhibit not only red,green,blue colors (RGB) light,but also other tuned various color light covering the whole visible range upon excitation of 345 nm through adjusting the relative ratios of metal complexes.As the most important key point,non-conductive polymers can be used in photoluminescence devices as host medium,which is not realized in electroluminescent devices.Thus,the flexible photoluminescence films (FPFs) innovated herein exhibit the great potential to apply for flexible light-color and light-energy transformation devices.
查看更多>>摘要：A novel entropy-stabilized (ES) (Ca,Sr,Ba)ZrO3 ceramic has been designed and synthesized by pressureless sintering of CaZrO3,SrZrO3 and BaZrO3 powders mixtures at 1450 ℃,1500 ℃ and 1550 ℃ for 3 h.X-ray diffraction,scanning electron microscopy and transmission electron microscopy analyses collectively indicate that a single solid solution is formed with a homogeneous distribution of metal elements after sintering at 1550℃.The relative density and hardness of the ES (Ca,Sr,Ba)ZrO3 ceramic sintered at 1550 ℃ are 97.79 ％ and 10.84 ± 0.33 GPa,respectively.This ES (Ca,Sr,Ba)ZrO3 exhibits lower thermal conductivity from 373 K to 1073 K than their constituting zirconates,CaZrO3,SrZrO3 and BaZrO3.Most importantly,the ES (Ca,Sr,Ba)ZrO3 ceramic possesses good corrosion resistance to TiNi alloy melt and no distinct reaction layer exists between TiNi alloy and ES (Ca,Sr,Ba)ZrO3 ceramic in the contact region.The combination of these properties indicates that ES (Ca,Sr,Ba)ZrO3 ceramic is promising for use as a novel crucible material for the melting of titanium alloys.
查看更多>>摘要：Phase selection and growth characteristics ofdirectionally solidified Al2O3/GdAlO3 (GAP) faceted eutectic ceramics are investigated over wide ranges of compositions and solidification rates to explore the eutectic coupled zone.Through the observation of the quenched solid-liquid interface,the competitive growth of primary faceted Al2O3 phase,primary non-faceted GAP phase and Al2O3/GAP eutectic with different morphologies is detected.Microstructure transitions from wholly eutectic to primary Al2O3 (GAP) dendrite plus eutectic and then to wholly eutectic are found in Al2O3-20 mol％ Gd2O3 hypoeutectic (Al2O3-26 mol％ Gd2O3 hypereutectic) ceramics with the increase of solidification rate.The dendrite growth of faceted Al2O3 and non-faceted GAP phases are well predicted by KGT model,which have introduced appropriate dimensionless supersaturation Ω2 to characterize the anisotropic growth of dendrites.Based on the maximum interface temperature criterion,the competitive growth of primary phase and eutectic is analyzed theoretically and the predicted coupled zone of Al2O3/GAP eutectic ceramics is in good agreement with the experimental results.Besides,the influence of microstructure with these different morphologies on the flexural strength of Al2O3/GAP eutectic ceramics is studied.
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