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Optimizing the coordination/surrounding environments of active metal nanoclusters to promote the catalytic performance during hydrogen evolution reaction (HER) in alkaline media is highly important but extremely challenging. Here, we demonstrate that novel S-coordinated ruthenium (Ru) nanoclusters anchored on N/S-codoped carbon nanosheets (Ru–S/N–C) can be successfully synthesized via the space-confinement pyrolysis of Ru complexes in the framework of polyaniline–ammonia persulfate supermolecules. X-ray absorption fine structure spectroscopy and X-ray photoelectron spectroscopy studies reveal the local coordination structure of Ru–S bonds, the surrounding N/S/C environments of Ru, and the synergistic electronic interactions among N, S, C and Ru atoms. Theoretical calculations further confirm that the coordination/surrounding environments could optimize the adsorption energies of intermediates on Ru through interfacial charge transfer and, thus, accelerate the reaction kinetics of hydrogen evolution. The fabricated Ru–S/N–C exhibits an ultra-small overpotential of 10 mV at 10 mA cm−2 and an extremely high turnover frequency (TOF) of 2.3 H2 s−1 at an overpotential of 50 mV for the HER, as well as a mass catalytic activity about 10 times higher than that of a commercial Pt/C catalyst.

The primary understanding of laser-induced non-isothermal prior β grain growth behaviour of titanium alloys is given by adopting laser quenching on pure titanium. Results indicate that the prior β ...

In our previous research, titanium-based nitride with high conductivity and superior corrosion resistance were developed as an ideal core material for replacing noble metal to form Pt-based core-shell catalysts by pulse electrodeposition. Meanwhile, the smaller sizes of nitride cores would also be available for pulse electrodeposition by dispersing them on carbon nanotubes (CNT). To achieve a better practice on the preparation of the Pt-based core-shell catalysts, in this work, both nitrogen-doped carbon nanotubes (N-CNT) and reduced graphene oxide (N-rGO) were used to support the copper-doped titanium nitride (Ti0.9Cu0.1N) cores. In the course of pulse electrodeposition, their influences as supports on the electronic states of electrodeposited Pt as well as their catalytic activities were compared. The results showed that the Pt preferred to electrodeposit on Ti0.9Cu0.1N cores supported by N-CNT and formed a core-shell structure. While with the same electrodeposition process, the Pt was found to be electrodeposited not only on the Ti0.9Cu0.1N cores supported by N-rGO with heavy aggregations but also on the N-rGO support. Raman spectroscopy analysis indicated that the higher degree of structural defects on N-rGO, as support, might have contributed to such divergence observation.

Exploring advanced electrocatalysts for the sluggish oxygen reduction reaction is extremely important for fuel cell commercialization but still remains a great challenge, especially the durability issue that gains increasing attention. Herein, we demonstrate an extremely durable catalyst prototype that combines structurally ordered intermetallic nanoparticles (NPs) with mesoporous carbon. With ZIF-8 derived mesoporous carbon supported Pt3Co intermetallic NPs (Pt3Co/DMC-F) as an example, we illustrate its synthetic details, electrocatalytic performance and durability enhancement mechanism. The Pt3Co/DMC-F catalyst exhibited significant enhancement in activity and durability. More importantly, its extraordinary performance was observed/verified in a H2/air PEM single cell test. The confinement of mesoporous carbon not only efficiently controls the particle size of Pt3Co and hampers their aggregation during thermal annealing and electrochemical reactions, but also significantly suppresses detachment. Beyond offering an advanced electrocatalyst, this study provides a solution to the durability issue of cathodes that has prevented practical application of proton exchange membrane fuel cells.

Icing/snowing/frosting is ubiquitous in nature and industrial processes, and the accretion of ice mostly leads to catastrophic consequences. The existing understanding of icing is still limited, particularly for aircraft icing, where direct observation of the freezing dynamics is inaccessible. In this work, we investigate experimentally the impact and freezing of a water drop onto the supercooled substrate at extremely low vapor pressure, to mimic an aircraft passing through clouds at a relatively high altitude, engendering icing upon collisions with pendant drops. Special attention is focused on the ice coverage induced by an impinging drop, from the perimeter pointing outward along the radial direction. We observed two freezing regimes: (I) spread-recoil-freeze at the substrate temperature of Ts = −15.4 ± 0.2 °C and (II) spread (incomplete)-freeze at the substrate temperature of Ts = −22.1 ± 0.2 °C. The ice coverage is approximately one order of magnitude larger than the frozen drop itself, and counterintuitively, larger supercooling yields smaller ice coverage in the range of interest. We attribute the variation of ice coverage to the kinetics of vapor diffusion in the two regimes. This fundamental understanding benefits the design of new anti-icing technologies for aircraft.

In this work, a glucose-derived carbon supported CrN composite is prepared by using a hydrothermal method and followed by a nitridating process. It is found that CrN nanoparticles in the composite are well-dispersed and separated by the carbon support. More importantly, the composite exhibits significantly enhanced oxygen reduction reaction activity than free-standing aggregated CrN nanoparticles, especially in acidic medium. The onset potential of the composite reaches 0.81 V in acidic medium, which is one of the highest values among the reported metal nitrides. The rotating ring disk electrode results indicate that the composite is more beneficial to O2 dissociation than free-standing CrN nanoparticles. Results of X-ray photoelectron spectroscopy, O2 temperature-programmed desorption and electrochemical impedance spectroscopy indicate that the significantly enhanced oxygen reduction reaction activity of the composite over free-standing CrN is derived not from the new formed active sites or enhanced oxygen adsorption but from the much enhanced electron transfer rate. This observation helps to understand the role of electron transfer rate playing in the oxygen reduction reaction activity of metal nitrides.

The prior β grain structure is recognized to be an important factor governing the mechanical properties of laser additive manufacturing (LAM) titanium alloys (ti-alloys) components. Five kinds of ti-alloys plates were fabricated by LAM process aiming to investigate the solidification behavior and grain morphology. Full columnar grains, full equiaxed grains and a special mixed grains structure were observed in LAM TC4, TB6 and TC11 plates, respectively, indicating that the formation tendency and volume fraction of equiaxed grains in LAM ti-alloys plates increase gradually with the increasing alloying content. It was proposed the formation of equiaxed grains is a multifactor functioning result of the constitutional supercooling and the remaining powders in the local melting pool.

Ti-10V-2Fe-3Al alloy specimen has been fabricated by laser melting deposition additive manufacturing technique. Due to the repeated heating and cooling during deposition, complicated and unique phase transformation process take place with forming different microstructures from forging. In this study, a three-dimensional (3D) reconstruction method is used to understand the spatial distribution of α phase in different grains. The results indicated that, in as deposited alloy, α laths has a plate morphology, and they precipitated out from β phase followed a tetrahedral relationship. And the different grain orientation result to the specific different morphology. When the cutting plane parallel to the {100} plane of BCC cell, α laths are perpendicular to each other. If the cutting plane is parallel to the {111} plane, a special morphology with mixture of plate-like and rod-like α phase is founded. Keywords: Laser additive manufacturing, Ti-10V-2Fe-3Al, Titanium alloys, Spatial distribution, Phase transformation

A new type of Ti-6.5Al-3.5Mo-0.3Si-xZr (x = 1.5, 2.5, 3.5, 4.5 wt%) titanium alloys developed on TC11 alloy (x = 1.5) with different Zr contents were fabricated by laser additive manufacturing process in order to enhance the mechanical properties. Grain morphology and microstructure were systematically investigated. The results demonstrate that the addition of Zr element dramatically refines the grains of the titanium alloys by offering heterogeneous nucleate sites and controlling grain growth during subsequent thermal cycles. And the latter is the main influencing factor. Meanwhile, the addition of Zr element in the alloys does not affect their microstructures, which with similar α lamellar thickness. And the microhardness and compressive strength of the alloys continuously increase with the increase of Zr contents.

In order to evaluate the effects of microstructure characteristics on fatigue crack growth (FCG) resistance of laser additive manufactured (LAM) AerMet100 steel, microstructures and FCG behaviors (in Paris region) of as-deposited specimen and three types of tempered martensite specimens were examined. Results indicate as-deposited specimens of LAM AerMet100 steel have apparent texture characteristics of epitaxy unidirectional growth prior-austenite columnar grains and grain-interior inter-dendritic blocky retained austenite with [001] crystallographic orientation. And poor boundary cracking resistance of these texture characteristics along deposition direction mainly contributes to the FCG rate anisotropy of as-deposited specimens. After post-LAM heat treatments, the FCG resistance of all heat-treated specimens apparently improves with the fracture mode of transgranular cracking. With the increase of yield strength, the value of Paris coefficient C of the steel increases, but the value of Paris exponent m decreases. Compared to the poor dislocation slip resistance of bainite plates in as-deposited specimens, the improved dislocation slip resistance of martensite plates is mainly related to the strong dislocation pinning effect of fine dispersive rod-like coherent M2C carbides, resulting in the stronger FCG resistance of the heat-treated specimens. In the Paris region of low ΔK ( ~ 70 MPa m1/2), higher contents of retained/reverted austenite inversely accelerate the FCG rate of heat-treated LAM AerMet100 steel. In contrast, grain refinement has the little influence on the FCG rate (in most of Paris region) of the heat-treated specimens.

Ultrahigh-strength AerMet100 steel plate was fabricated by laser additive manufacturing process (LAM) followed by subsequent heat treatments. Microstructures and tensile mechanical properties of the steel were examined using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and universal mechanical testing machine. The results indicate that post-LAM heat treatments greatly change alloy carbide characteristics, decrease austenite content and prompt the formation of fine equiaxed prior-austenite grains for LAM AerMet100 steel. Compared to fine short rod-like Nb-rich MC carbides and needle-like M3C carbides in as-deposited specimens, alloy carbides in tempered specimens have the large changes, which include fine spherical Nb-rich MC carbides, fine rod-like M2C carbides, large-size spherical Mo-rich M6C carbides and Cr-rich M23C6 carbides. And the fine rod-like M2C carbides are dispersive distribution and coherency with the martix martensite, resulting in strong coherent strain strengthening. After proper post homogeneity heat treatment processes, tensile mechanical properties of LAM AerMet100 steel have the comprehensive improvement, which are comparable to those of the forged ones. In comparison with low ductility of as-deposited specimen, the higher ductility of tempered specimen is mainly related to its extremely strong strain-strengthening capability achieved by dispersive precipitation of M2C carbides. With the increase of homogenization, the further improved ductility of tempered specimen mainly ascribe to the decreased amount and size of large-size alloy carbides (especially Mo-rich M6C carbide).

Microalloyed coatings were fabricated on a forged TC11 titanium alloy surface by adding different amount of ZrN powders using laser cladding technique. Microstructures of coatings and heat affect zone were systematically investigated with the study of microhardness as well as wear property. Results indicated that all coatings have very uniform equiaxial grains with very fine α + β two-phase microstructure (the thickness of α lamellar is 0.8 μm), and nearly no change of microstructure for coatings was observed with the increase contents of ZrN from 3 wt% to 12 wt%. The changes of microstructure from coating to substrate are: fine α + β two-phase structure, super fine α + β two-phase structure (α lamellar of 0.2 μm), αp + αs + β structure, and α + β (forged). By increasing the contents of Zr and N, the hardness of coatings increased accordingly with no suddenly change at the interfacial region. Due to the strong solid-solution strengthening, coatings maintain high hardness even coarsening their microstructures. The enhanced hardness of coatings largely improves the wear properties of alloys to only more than twice of the TC11 matrix when addition of 12 wt% ZrN.

The severe dissolution of the cathode catalyst, caused by an undesired oxygen reduction reaction at the anode during startup and shutdown, is a fatal challenge to practical applications of polymer electrolyte membrane fuel cells. To address this important issue, according to the distinct structure-sensitivity between the σ-type bond in H2 and the π-type bond in O2, we design a HD-Pt/TiN material by highly dispersing Pt on the TiN surface to inhibit the unwanted oxygen reduction reaction. The highly dispersed Pt/TiN catalyst exhibits excellent selectivity toward hydrogen oxidation and oxygen reduction reactions. With a Pt loading of 0.88 wt %, our catalyst shows excellent hydrogen oxidation reaction activity, close to that of commercial 20 wt % Pt/C catalyst, and much lower oxygen reduction reaction activity than the commercial 20 wt % Pt/C catalyst. The lack of well-ordered Pt facets is responsible for the excellent selectivity of the HD-Pt/TiN materials toward hydrogen oxidation and oxygen reduction reac...

The effect of heat treatments on laser additive manufacturing (LAM) Ti-5Al-2Sn-2Zr-4Mo-4Cr titanium alloy (TC17) was studied aiming to optimize its microstructure and mechanical properties. The as-deposited sample exhibits features of a mixed prior β grain structure consisting of equiaxed and columnar grains, intragranular ultra-fine α laths and numerous continuous grain boundary α (αGB). After being pre-annealed in α+β region (840 °C) and standard solution and aging treated, the continuous αGB becomes coarser and the precipitate free zone (PFZ) nearby the αGB transforms into a zone filled with ultra-fine secondary α (αS) but no primary α (αP). When pre-annealed in single β region (910 °C), all α phases transform into β phase and the alloying elements distribute uniformly near the grain boundary. Discontinuous αGB and uniform mixture of αP and αS near grain boundary form after subsequent solution and aging treatment. The two heat treatments can improve the tensile mechanical properties of LAM TC17 to satisfy the aviation standard for TC17.

In this work, we developed a renewable wood-derived cathode with well-aligned elongated microchannels for high-performance Li–O2 batteries. The cathode was obtained from natural wood following carbonization, activation, and then loading of RuO2 nanoparticles (4.15 wt%) as catalysts (RuO2/WD-C). The cathode has a three-dimensional, high stability carbon matrix, uniformly anchored catalysts, and well-aligned porous microchannels. As a result, the specific areal capacity of the assembled batteries exceeds 8 mA h cm−2 and the charge terminal potential is lower than 3.8 V at 0.1 mA cm−2. The energy efficiency was improved up to 91.9% and exceeded 87.1% after 100 cycles (curtailed capacity of 0.5 mA h cm−2 at 0.2 mA cm−2). Furthermore, the RuO2/WD-C cathode can be fully regenerated from a deep discharge–charge cycle or 100 curtailed-capacity cycles by simply washing with water. The areal capacity of the regenerated RuO2/WD-C cathode is comparable to the performance of the initial cathode. The cut-off voltage was above 2.6 V following 200 cycles. Even when regenerated for the second time, the RuO2/WD-C cathode still demonstrated almost the same high performance as the initial one, indicating its high stability and excellent renewability.

A three-dimensional, low platinum (Pt) catalyst was prepared by decorating platinum on the palladium nanoflowers (Pd NF) by an underpotential deposition (UPD) method. The Pd NF was synthesized by a solvothermal approach, using oleic acid as the template and benzyl alcohol as the solvent-reducing agent. The obtained Pd with a morphology of uniform nanoflowers is composed of plentiful nanosheets. After decorating with platinum, the catalyst Pd NF@Pt exhibits much higher activity for the oxygen reduction reaction (ORR) compared to commercial Pt/C (Pt 20 wt%). The interaction between deposited Pt and Pd NF was revealed by XPS analysis, and the high performance of the Pd NF@Pt catalyst was attributed to following two aspects: the increased of dispersion of platinum based on Pd NF substrate, and the increased intrinsic activity of the active sites caused by the interaction of Pt and Pd NF.

In this study, a novel low-Pt core-shell catalyst is successfully prepared by depositing ultrathin Pt layer on the carbon nanotubes supported titanium nitride nanoparticles (TiN@Pt/CNTs) via a facile pulse electrochemical deposition approach. The catalyst is characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), High-angle annular dark field (HAADF) and energy-dispersive spectrometer (EDS) elemental mapping, X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. The results confirm the core-shell structure of the prepared TiN@Pt/CNTs catalyst. More importantly, the catalyst exhibits superb mass activity and durability for the methanol oxidation reaction (MOR) than that of the commercial JM Pt/C catalyst. Later experiments data demonstrate that the activity and stability of the catalyst can be further enhanced via copper doping, which results from the modified electronic structure of the Pt atoms and the synergistic effects of the core-shell structure.

Direct laser deposition (DLD) is a potential approach to prepare large-scale metal component. This work focuses on understanding microstructural characteristics and mechanical properties along deposition direction of 2A97 Al–Li alloy fabricated by direct laser deposition. As-deposited sample showed coarse equiaxed grains at top and columnar crystals at middle and bottom. Growth texture of as-deposited sample along was relatively obvious, value of which increased first and then decreased from bottom to top. Thermal cycle led to different kinds and distribution of precipitated phases along deposition direction, which affected microhardness and tensile strength. T1 phase and a small amount of T2, TB phase precipitated at top. Effect of thermal cycle from top to bottom gradually increased, resulted in δ′, T2, TB phase coarsened. As a result, microhardness decreased from top (99 HV) to bottom (75HV). The sample in bottom showed an ultimate tensile strength (UTS) of 232.9 ± 4.3 MPa, and elongation of 9.5 ± 1.4%. While, ultimate tensile strength was increased to 268.5 ± 5.2 MPa, and elongation was 12.5 ± 0.9% in middle part, which was close to that of sample at top.

The oxygen reduction reaction (ORR) takes place on the surface of catalyst, and the precise control of surface component at atomic scale has been an important factor to effectively improve the performance of catalysts. Herein, a highly active and stable catalyst is designed by constructing Pt skin and controllable near-surface atomic distribution of PtNi alloy nanowires (NWs). It is found that the d-band center of Pt-skin down-shifts with Pt ratio in the surface/near-surface of PtNi alloy decreasing, and correspondingly the adsorption energy of atomic oxygen (ΔEO) on PtNi alloys weakens, confirmed by experimental results and theoretical calculations. The optimum PtNi/C-NH3 NWs exhibit the enhanced mass activity (1.02 A mgPt−1) and specific activity (3.86 mA cm−2) for ORR, which are 5.7-fold and 11.4-fold higher than those of commercial Pt/C, respectively. Moreover, the H2/air fuel cell of PtNi/C-NH3 NWs exhibits a current density of 308 mA cm−2 at 0.8 V, which is superior to that of the 2020 target of the U.S. Department of Energy (DOE). Our study provides a new perspective and approach in promoting the electrocatalysis on alloy nanomaterials for ORR.

Core-shell structured Ru@Pd/C catalysts for the electrooxidation of formic acid are synthesized by an organic colloid method associated with a pulse electrodeposition process. The catalysts are characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and X-ray photoelectron spectroscopy (XPS). The electrocatalytic activity of the catalysts is evaluated by cyclic voltammetry, CO stripping and chronoamperometry technologies. The core-shell structure is revealed by both materials characterization and electrochemical methods, including STEM and energy dispersive X-ray spectroscopy (EDX), the binding energy difference of the XPS spectra and the potential shift of the CO stripping peaks. Such core-shell structured Ru@Pd/C catalysts show excellent activity towards the anodic oxidation of formic acid. The mass activity reaches 5.06 A mg−1Pd and 0.53 A mg−1metal which are ∼10.1 and 1.1 times that of commercial Pd/C. The encouraging performance of Ru@Pd/C is ascribed to the distinct dispersion of the Ru cores and the resulting Ru@Pd nanoparticles as well as the synergy between the core and shell that not only significantly enhances the ability to oxidize the formic acid but also improves the tolerance to CO.

A class of core–shell structured low-platinum catalysts with well-dispersed inexpensive titanium copper nitride nanoparticles as cores and atomic platinum layers as shells exhibiting high activity and stability for the oxygen reduction reaction is successfully developed. Using nitrided carbon nanotubes (NCNTs) as the support greatly improved the morphology and dispersion of the nitride nanoparticles, resulting in significant enhancement of the performance of the catalyst. The optimized catalyst, Ti0.9Cu0.1N@Pt/NCNTs, has a Pt mass activity 5 times higher than that of commercial Pt/C, comparable to that of core–shell catalysts with precious metal nanoparticles as the core, and much higher than that the latter if we take into account the mass activity of all platinum group metals. Furthermore, only a minimal loss of activity can be observed after 10000 potential cycles, demonstrating the catalyst’s high stability. Atomic-scale elemental mapping confirmed that the core–shell structure of the catalyst remaine...

Transition metal nitrides have recently attracted significant interest as electrocatalysts for the oxygen reduction reaction (ORR) owing to their low electrical resistance and good corrosion resistance. In this paper, we describe the preparation of a Nb-based binary nitride material with a porous nanogrid morphology/structure. The catalyst exhibited good catalytic activity and high stability towards oxygen reduction. We also intensively investigated the effect that doping with a second transition metal had on the performance of the catalyst. We found that the ORR activity of NbN could be enhanced significantly by enriching the d electrons of Nb through doping with a second transition metal, and that doping with cobalt resulted in the best improvement. Our optimal catalyst, Nb0.95Co0.05N, had an ORR activity ∼4.6 times that of NbN (current density @ 0.6 V vs. the RHE). XPS results revealed that Co doping increased the proportion of Nb in a low-valence state, which may be one of the most important reasons for the enhanced performance. Another important reason is the high surface area resulting from the porous nanogrid morphology. As transition metal doping is an attractive way to enhance the activity of nitride catalysts, our work may provide an effective pathway to achieve this.

Vortex electromagnetic (EM) waves, which carry orbital angular momentum (OAM), offers a new degree of freedom for radar detection, although to date few researches on vortex EM waves scattering characteristics for typical targets have been reported. In this paper, we investigated the backscattering characteristics of vortex EM waves for targets, i.e., corner reflectors, and flat plate. Experiments are carried out in an anechoic chamber to measure the radar cross section (RCS) of the targets, and the results indicate that for corner reflectors the RCS fluctuations of vortex EM waves are similar to that of the plane EM wave, whereas for the flat plate, RCS varies with OAM mode. The significance of this work exists in its pioneering character, which paves the way for revealing EM scattering characteristics in OAM domain.

Ultrahigh-strength AerMet100 steel thick plate was fabricated by laser additive manufacturing process. The as-deposited microstructures of the test steel were characterized using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The mechanical properties were then examined using vickers-hardness test and tensile test. Results indicate that the as-deposited microstructures of the steel mainly consist of grain boundary allotriomorphic ferrite (GBA), grain interior irregular proeutectoid ferrite, plate-like upper bainite, needle-like lower bainite and retained austenite, which result in a good strength and some ductility anisotropy. The low deformation compatibility of specimen at the transverse direction (perpendicular to the deposition direction) mainly ascribes to the poor cracking resistance of the prior-austenite columnar grain boundary with coarse GBA phases. Compared to the almost intergranular cracking taken place in the transverse tensile specimen, the fracture mode of the longitudinal tensile specimen is a mixed mode of the predominant transgranular cracking and minor intergranular cracking.

To give a deep insight into the nitrogen transfer mechanism during laser solid-state surface modification on titanium alloy, laser nitridation was conducted on Ti-6.5Al-3.5Mo-1.5Zr-0.3Si titanium alloy (TC11) without melting the metal surface. Microstructure characterizations of nitride layer formed under solid state condition were detailedly explored and the formation process of TiN phase was carefully discussed based on the lattice transformation. Results indicate that the nitride layer forming within a few seconds is composed of TiN phase layer and α phase layer with an orientation relationship: ( 1 1 ¯ 1 )TiN // (0001)α, [011]TiN // [ 2 11 ¯ 0 ]α. Formation of TiN phase experiences fast solid-state transformation from α phase. Phase transformation from α-Ti lattice to TiN lattice experiences orthorhombic lattice transformation due to the shear deformation caused by rapid interstitial solution of nitrogen. After repeated laser nitridation process upon three times, nitride layer was thickened with an improved hardness of 824 HV. Linearly reciprocating ball-on-plane wear tests indicate that wear resistance of laser nitridation samples could be enhanced by a factor of 13.

The high-energy input and thermal history during additive manufacturing lead to complex phase transformations in titanium aluminide alloy. This study mostly focuses on determining the solid-state phase transformation mechanisms during laser deposition and the failure mechanisms of alloys using molecular dynamics simulations. Because of the directional temperature gradient, columnar grains with fully lamellar microstructures are formed first after solidification. A narrow region just below the melting pool is reheated to high temperatures, thus enhancing the precipitation of new equiaxed grains. Multiple thermal cycles in the α + γ phase region promote the formation of massive γ phases (γm) at the grain boundaries. Finally, a nearly lamellar microstructure of alternating columnar and equiaxed grains with γm phases is formed. The deposited titanium aluminide alloy has good room and high-temperature (760 °C) tensile properties of 545 ± 9 and 471 ± 37 MPa, with elongations of 1.50 % ± 0.47 % and 1.50 % ± 0.45 %, respectively. The room and high-temperature samples both fail in the columnar grain region. The molecular dynamics simulations suggest that the interface between α2 and γm is the weakest, especially in the case of semicoherent interfaces (6° angle in the [1–10] direction), which provides good nucleation sites for cracks. Although the equiaxed grain regions contain several γm–α2 interfaces, the samples still fail in the columnar grain regions due to the increase in the cracking distance in the equiaxed regions caused by randomly oriented α2 + γ lamellae and the comparably good plasticity of the γm phases.

Developing cheap and stable electrocatalysts is considered the key factor to achieve the large-scale application of fuel cells. In this paper, three-dimensional (3D) porous Co-doped vanadium nitride (VN) nanosheet-assembled microflowers are prepared with a facile solvothermal approach followed by nitridation at 500 °C in NH3. It is found that the microflower morphology and the Co doping both significantly enhance the oxygen reduction reaction (ORR) performance of the materials. Because the unique 3D porous structure provides higher specific surface area and more active sites as well as enriching the d electrons of V via doping, Co also improves the intrinsic activity of VN. Our optimal V0.95Co0.05N microflowers achieve a half-wave potential for the ORR of up to 0.80 V in 0.1 M KOH solution, which is almost comparable to that of commercial 20% Pt/C. More importantly, the catalysts show superior durability with little current decline (less than 12%) during chronoamperometric evaluation for over 25 000 s. Th...