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• Al-Mg-Sc-Zr components fabricated by WAAM were nearly full dense. • Unique microstructure features of WAAM-processed Al-Mg-Sc-Zr. • The short-circuit transition mode of CMT and microalloying effect of Sc + Zr change the microstructure morphologies of molten pool. • Controlling interlayer temperature at 100 °C improved the strength. • Solid solution strengthening was the main strengthening mechanism. Wire arc additive manufacturing (WAAM) technique is a promising approach to producing large-scale metal components due to high deposition efficiency and low production cost. However, fundamental research about WAAM-processed Al-Mg-Sc-Zr alloy was still fewer. In this study, Al-6.54Mg-0.36Sc-0.11Zr (wt%) components were successfully manufactured by WAAM with an interlayer temperature at 100 °C (named IW) and continuous printing (named CP), and the corresponding porosity, microstructure, and mechanical properties of components were studied in detail. The porosity of components as-deposited was relatively low, about 0.385% and 0.116%, respectively. The microstructures of the two components exhibited the same distribution characteristics in XZ and YZ planes: fine equiaxed grains (FEG) at remelted zone + FEG and coarse equiaxed grain (CEG) alternative distribution at middle zone + FEG at the top zone of the molten pool. The average grain size of component IW was about 10.51 ± 6.01 μm, and that of component CP significantly increased, to about 11.85 ± 5.86 μm. The short-circuit transition mode of cold metal transfer technology and the heterogeneous nucleation effect of primary Al 3 (Sc, Zr) and Al 3 (Sc, Zr, Ti) phases together promoted the formation of equiaxed grains and refined the microstructures. After heat treatment at 325 °C and 6 h, nano-Al 3 Sc precipitated with a size of about 15–50 nm. The yield strength (YS) of components IW and CP increased from 171 ± 3 to 261 ± 1 MPa and 168 ± 7 to 240 ± 17 MPa, respectively. Component IW had the highest ultimate tensile strength, about 400 ± 1 MPa. For WAAM-processed Al-Mg-Sc-Zr alloys, the contribution of the strengthening mechanism to YS was solid solution strengthening > precipitation strengthening > fine grain strengthening > dislocation strengthening. [Display omitted] [ABSTRACT FROM AUTHOR]

Hot cracking is the most prevalent defect in the rapid solidification process of alloys, which seriously restricts the mechanical properties of the build. Solidification shrinkage is one of the key factors leading to hot cracking sensitivity, and it, together with tensile stress, causes pressure drops inside the liquid channel. However, the mechanism of solidification shrinkage on hot cracking is not clear. In this work, we established a non-equilibrium phase field model considering the density change during liquid-solid phase transformation. The effects of solidification shrinkage on the morphology and solute segregation of liquid channel in directional solidification were simulated by examples with different solid density. The solidification shrinkage will promote the release and diffusion of solute, leading to an increase in the proportion of high solute concentration liquid in the channel. The columnar dendrites continue to solidify, leading to a decrease in constitutional supercooling in the channel, thereby reducing the temperature at which the solid skeletons connect with each other. This results in the channel becoming narrow and elongated, increasing the hot cracking sensitivity. Finally, the solidification curves obtained from the phase field model and analytical model are input into the RDG (Rappaz, Drezet and Gremaud) model to predict the pressure drop in the system. The numerical results indicate that the maximum pressure drop in the channel occurs at the root and increases with solidification shrinkage. These results demonstrate that the phase field model, which takes into account the change of liquid-solid densities during phase transition, can accurately analyze the impact of solidification shrinkage on hot cracking sensitivity and the maximum pressure drop in the liquid channel.

Oxides play a crucial role in shaping various properties in ferritic alloys under Helium environment. This study investigates the thermodynamic and mechanical properties of Y4Zr3O12and Y2Ti2O7oxides in ferritic alloys with and without Helium utilizing a systematic first-principles approach. Firstly, the atomic arrangement of Y and Zr atoms at cation 18fsites in δ-(Y–Zr–O) oxide is identified, while it is found that Y4Zr3O12exhibits a more robust formation tendency than Y2Ti2O7. Furthermore, it is noted that both Y4Zr3O12and Y2Ti2O7oxides demonstrate a prior ability to trap Helium compared to the bcc-Fe matrix, which leads to a substantial enhancement on the stiffness of both oxides. The elastic moduli of both Y4Zr3O12and Y2Ti2O7oxide exhibit a gradual increase with the growing Helium concentration. As a result, the enhanced shear modulus of oxides and sustained shear modulus of the bcc-Fe matrix collectively contribute to the overall strength of ferritic alloys under Helium environments. The findings in this work propose valuable insights for guiding critical strategies in the design of high-performance oxide-dispersion-strengthened ferritic alloys, particularly for applications in Helium environments.

• Doping cerium (Ce) presents a promising pathway to synergistically improve the strength and ductility of stainless steels by AM. • The strengthening mechanism is contributed by strengthening effects of nanoscale precipitation (inclusion) and grain refining by doping Ce. • The improved misorientation angle of grain boundary and ameliorative coherency between the inclusion and matrix by doping Ce benefits the ductility. In this study, the PH13–8Mo stainless steel parts doped without and with cerium (Ce) were fabricated via laser powder bed fusion followed by post-heat treatment, and systematically compared in terms of microstructure, phase constituent, and tensile properties. The comparative results show that doping Ce-modified grains with the equiaxed morphology and finer size, increased the mechanical stability of austenite, and enhanced the sphericity of oxide inclusion in the resultant PH13–8Mo. Additionally, the coherency between the newly-formed CeAlO 3 inclusion and matrix was effectively improved after doping Ce, as compared to the original aluminum oxide inclusion without doping Ce. The resultant PH13–8Mo parts doped with Ce yielded an ultimate tensile strength of 1446 ± 20 MPa with a fracture elongation of 16.0% ± 1.5%, for the first time meeting the AMS 5629E H1000 standard for the PH13–8Mo made by additive manufacturing (AM). The enhanced strength results from the strengthening effects of nanoscale precipitation (inclusion) and grain refining. Meanwhile, the ductilizing mechanism can be attributed to the enhanced inclusion sphericity and ameliorative coherency between the inclusion and matrix, and improved misorientation angle of grain boundary owing to the modification by Ce, which efficiently reduced the stress concentration and enhanced cracking resistance during deformation. Therefore, doping rare earth elements presents a promising pathway to synergistically improve the strength and ductility of stainless steels by AM. [Display omitted] [ABSTRACT FROM AUTHOR]

Diamond/SiC composites were prepared by vacuum silica vapor-phase infiltration of in situ silicon–carbon reaction, and the thermophysical properties of the composites were modulated by controlling diamond graphitizing. The effects of diamond surface state and vacuum silicon infiltration temperature on diamond graphitization were investigated, and the micro-morphology, phase composition, and properties of the composites were observed and characterized. The results show that diamond pretreatment can reduce the probability of graphitizing; when the penetration temperature is greater than 1600 °C, the diamond undergoes a graphitizing phase transition and the micro-morphology presents a lamellar shape. The thermal conductivity, density, and flexural strength of the composites increased and then decreased with the increase of penetration temperature in the experimentally designed range of penetration temperature. The variation of thermal expansion coefficients of composites prepared with different penetration temperatures ranged from 0.8 to 3.0 ppm/K when the temperature was between 50 and 400 °C.

• Bulk W-Re alloys have achieved ∼98%–99% densities with ∼200–300 nm grain size. • Pressureless two-step sintering resolves the sintering conundrum of W-Re alloys. • Re alloying suppresses the final-stage densification of W-Re. • Re alloying can dramatically inhibit the grain growth at low temperature. • The exploration of W-Re system provides theoretical guidance for W-B and Fe-Co. Tungsten-rhenium (W-Re) alloys with high-Re contents are the preferred refractory metal materials in many applications because of the improved ductility and processability over pure W and low-Re tungsten alloys. However, the sintering concurrently becomes increasingly more difficult with increasing Re contents. Here we proposed that the sintering conundrum is caused by the lowered crystal symmetry and the wider dihedral angle distribution when body-center-cubic (BCC) W is alloyed with more hexagonal-close-packed (HCP) Re, which results in inefficient pore removal in the final stage sintering. We showed that the conundrum can be resolved by pressureless two-step sintering (TSS) which suppresses accelerating final-stage grain growth, and our proposal is supported by the data of the critical density ρ c that is required to start the second step for successful TSS at different W-Re compositions. Dense ultrafine-grained W-Re alloys with ∼300 nm average grain size and up to 25 wt% Re were successfully produced. Our work demonstrates the unique opportunities offered by two-step sintering to advance the scientific understanding and technological practices in powder metallurgy and related fields. Sintering tungsten-rhenium (W-Re) alloys becomes difficult with increasing Re content, which is revealed by the final-stage bifurcation. The pressureless two-step sintering method is carried out to resolve the sintering conundrum and produces ultrafine-grained W-Re alloys containing up to 25 wt% Re with record-fine grain sizes, uniform microstructures, and high hardness. [Display omitted] [ABSTRACT FROM AUTHOR]

Microstructure plays a crucial role in predicting the properties of parts by additive manufacturing. Fluid flow and temperature gradient are always recognized as key factors influencing the final microstructure. However, the effects of flow field were often ignored during microstructure simulation inside the molten pool. In this study, the Marangoni flow is firstly calculated using the finite element method. Fluid flow increases the temperature gradient and the cooling rate at the solid front. Subsequently, the temperature field and flow field are input to phase-field model to simulate the microstructure inside the molten pool. This integrated model is then applied to study the solidification behavior of IN718 alloy during additive manufacturing. The microstructure evolutions are analyzed in detail under different processing parameters. The simulation results demonstrate that the Marangoni flow has great effects on both molten pool and solidification microstructure. The integrated model developed in this work can predict the molten pool and solidification microstructure more accurately by combining the thermal, flow and microstructure models together.

Al–Li alloys are extensively utilized in the field of aerospace due to their low density and high specific strength. However, laser powder bed fusion (LPBF) processed Al–Li alloys still encounter challenges because of hot cracking and Li element ablation. In this study, a TiC nanoparticle modified Al–Mg–Li alloy is developed for LPBF process. Full dense printed TiC modified Al–Mg–Li alloy can be obtained. The presence of TiC nanoparticles in the melt pool effectively increased the viscosity of Al alloy liquid, leading to a reduction in the metal vaporization and liquid spatters, thus preventing the Li ablation during LBPF. The Li content was significantly increased from 0.87 wt.% in the Al–Mg–Li alloy to 1.34 % in the TiC modified Al–Mg–Li alloy. Moreover, the TiC nanoparticles played a key role in transition of columnar to equiaxed grain. The average grain size of TiC modified Al–Mg–Li alloy was refined to about 1.5 μm, two orders of magnitude smaller than that in printed Al–Mg–Li alloy. A gradient transition reaction from TiC to Al3Ti was found on the TiC nanoparticles surface during LPBF. The in-situformed Al3Ti phase on TiC nanoparticles significantly decreased the lattice mismatch with Al matrix, thereby resulting in an outstanding mechanical property of ultimate tensile strength of 343 MPa and elongation of 9.3 %. The effect of Li element anti-ablation induced by TiC nanoparticles provided a new pathway for additive manufacturing light-weight alloy.

Although the stabilizing heat treatment between solution treatment and aging treatment in Inconel 706 alloy is important to improve its stress rupture life, the influence of stabilization heat treatment temperature on the microstructure and stress rupture properties has not been well understood. In this study, heat treatments consisting of three stabilization temperatures (800 °C, 845 °C, and 880 °C) were performed in Inconel 706 alloy. The results showed that the stress rupture properties were improved with the increase of stabilization temperature. When compared with stabilization at 800 °C, the alloy stabilized at 880 °C exhibited a 96% increase in stress rupture life and a 110% increase in elongation. Furthermore, increasing the stabilization temperature led to the increased amount of η phase at grain boundaries. The η phase appeared in granular, rod-shaped or needle-shaped morphology. The microstructure in the grain interior exhibited compact γ'/γ" coprecipitates in the samples stabilized at 800 °C and 845 °C, while that showed noncompact γ'/γ" coprecipitates in the sample stabilized at 880 °C. The formation of 2.34 vol% η phase was found to be beneficial for the stress rupture properties. The improvement in stress rupture properties was ascribed to the presence of η phase and the associated precipitate-free zones at grain boundaries.

Activating anionic redox chemistry in layered oxide cathodes is a paradigmatic approach to devise high-energy sodium-ion batteries. Unfortunately, excessive oxygen redox usually induces irreversible lattice oxygen loss and cation migration, resulting in rapid capacity and voltage fading and sluggish reaction kinetics. Herein, the reductive coupling mechanism (RCM) of uncommon electron transfer from oxygen to copper ions is unraveled in a novel P2-Na0.8Cu0.22Li0.08Mn0.67O2cathode for boosting the reversibility and kinetics of anionic redox reactions. The resultant strong covalent Cu–(O–O) bonding can efficaciously suppress excessive oxygen oxidation and irreversible cation migration. Consequently, the P2-Na0.8Cu0.22Li0.08Mn0.67O2cathode delivers a marvelous rate capability (134.1 and 63.2 mAh g–1at 0.1C and 100C, respectively) and outstanding long-term cycling stability (82% capacity retention after 500 cycles at 10C). The intrinsic functioning mechanisms of RCM are fully understood through systematic in situ/ex situ characterizations and theoretical computations. This study opens a new avenue toward enhancing the stability and dynamics of oxygen redox chemistry.

The oxygen evolution reaction (OER) plays a vital role in renewable energy technologies, including in fuel cells, metal–air batteries, and water splitting; however, the currently available catalysts still suffer from unsatisfactory performance due to the sluggish OER kinetics. Herein, we developed a new catalyst with high efficiency in which the dynamic exchange mechanism of active Fe sites in the OER was regulated by crystal plane engineering and pore structure design. High-density nanoholes were created on cobalt hydroxide as the catalyst host, and then Fe species were filled inside the nanoholes. During the OER, the dynamic Fe was selectively and strongly adsorbed by the (101̅0) sites on the nanohole walls rather than the (0001) basal plane, and at the same time the space-confining effect of the nanohole slowed down the Fe diffusion from catalyst to electrolyte. As a result, a local high-flux Fe dynamic equilibrium inside the nanoholes for OER was achieved, as demonstrated by the Fe57isotope labeled mass spectrometry, thereby delivering a high OER activity. The catalyst showed a remarkably low overpotential of 228 mV at a current density of 10 mA cm–2, which is among the best cobalt-based catalysts reported so far. This special protection strategy for Fe also greatly improved the catalytic stability, reducing the Fe leaching amount by 2 orders of magnitude compared with the pure Fe hydroxide catalyst and thus delivering a long-term stability of 130 h. An assembled Zn–air battery was stably cycled for 170 h with a low discharge/charge voltage difference of 0.72 V.

• Designing high-strength Ni-based turbine disc superalloys by data-driven way. • Cross-scale design from crystal to phase and then to mechanical property. • Designed alloys having a higher yield strength than commercial superalloys. • Expending less resources than traditional trial-and-error tests. Increasing the thrust-weight ratio of aeroengines requires development of high-strength and stable high-temperature materials. A data-driven design of Ni-based turbine disc superalloys is performed to improve the yield strength to reach the target. Through first-principles calculations determining the design superalloy system, the theoretical models and Calculation of Phase Diagram (CALPHAD) screening compositions, and machine learning extrapolating prediction, 14 compositions are selected from 2,865,039 composition combinations. Ni-17Cr-8Co-1Mo-1W-6Al-3Ti-1Nb-1Ta is selected to verify the design accuracy. Experimental tests prove that the designed alloy has trade-offs of microstructure with satisfying design targets, and then, the yield strength is higher in the designed alloy than in commercial superalloys, reaching 728 MPa at 850 °C. A scheme for increasing the performance of the designed alloy is proposed by discussing the strengthening mechanisms, machine learning process, and alloying chemistry effect. The cross-scale data-driven design is regarded as an accurate and efficient way to design novel high-strength Ni-based turbine disc superalloys, whose significance is the obvious reduction of trial-and-error tests. [Display omitted] [ABSTRACT FROM AUTHOR]

Graphical abstract:

Ductility deterioration induced by L21-Ni2AlTi precipitates in the aged ferritic alloys was examined systematically by using a combination of scanning transmission electron microscope (STEM), mechanical tests and first-principles thermodynamic calculations. The experimental studies revealed that the strength and hardness of the aged Fe–10Cr–5Ni–1Al–1Ti ferritic alloy containing B2–NiAl and L21-Ni2AlTi precipitates were higher than that of the aged Fe–10Cr–5Ni–1Al ferritic alloy containing NiAl precipitates, whereas the elongation-to-failure decreased dramatically from 9.3% to 0.3% indicating an obvious ductility deterioration due to the formation of L21-Ni2AlTi precipitates. This was also confirmed by the observation of fracture transition mode from dimpled failure to cleavage failure. The first-principles calculations, concerning the precipitate/matrix interface, were carried out to provide a theoretical analysis for the ductile–brittle transition by means of empirical ductility criteria ratios G/Band (C12–C44)/Bas well as cleavage energy. The cleavage energy results indicated an intrinsic brittleness of the L21-Ni2AlTi phase and the L21-Ni2AlTi/BCC-Fe interface. Our analysis revealed that the intrinsic brittleness of L21-Ni2AlTi phase and L21-Ni2AlTi/BCC-Fe interface plays a vital role in determining the deformation behavior of the aged Fe–10Cr–5Ni–1Al–1Ti alloy.

This article reported a simple method for preparing diamond/SiC composites by polymer impregnation and pyrolysis (PIP) process, and the advantages of this method were discussed. Only diamond and SiC were contained in the diamond/SiC composite prepared by PIP process, and the diamond particles remained thermally stable up until the pyrolysis temperature was increased to 1600 °C. The pyrolysis temperature has a significant impact on the thermal conductivity and dielectric properties of composites. The thermal conductivity of the composite reaches a maximum value of 63.9 W/mK when the pyrolysis temperature is 1600 °C, and the minimum values of the real and imaginary part of the complex permittivity are 19.5 and 0.77, respectively. The PIP process is a quick and easy method to prepare diamond/SiC composites without needing expensive equipment, and it is of importance for promoting its application in the field of electric packaging substrate.

Although manganese-based oxides possess high voltage and low cost, the sluggish reaction kinetics and poor structural stability hinder their applications in aqueous rechargeable Zn-ion batteries (ZIBs). Herein, a molybdenum (Mo) pre-intercalation strategy is proposed to solve the above issues of δ-MnO2. The pre-intercalated Mo dopants, acting as the interlayer pillars, can not only expand the interlayer spacing but also reinforce the layered structure of δ-MnO2, finally achieving enhanced reaction kinetics and superb cycling stability during carrier (de)intercalation. Moreover, oxygen defects, introduced due to Mo-pre-intercalation, play a critical role in the fast reaction kinetics and capacity improvement of the Mo-pre-intercalated δ-MnO2(Mo-MnO2) cathode. Therefore, the Mo-MnO2cathode displays a high energy density of 451 Wh kg–1(based on cathode mass), excellent rate capability, and admirable long-term cycling performance with a high capacity of 159 mAhg–1at 1.0 A g–1after 1000 cycles. In addition, the energy storage mechanism of Zn2+/H+stepwise reversible (de)intercalation is also revealed by ex situ experiments. This work provides an insightful guide for boosting the electrochemical performance of Mn-based oxide cathodes for ZIBs.

Despite the growing development of ceramic fabrication by vat photopolymerization (VP), major gaps remain in application. Particularly in the case of VP-printed aluminum nitride (AlN) ceramic, the thermal conductivity is still below 170 W·m−1·K−1, a critical benchmark for efficient heat dissipation. To address this challenge, here we prepared an AlN slurry with high curing thickness through RI coupling between liquid-solid phase, and took into account of the rheological property under high solid loading. Full dense AlN green bodies with solid loading up to 50 vol% were successfully printed. Aiming to to tackle the degradation of thermal conductivity issue caused by oxygen increment of AlN via VP, we systemically studied the form of oxygen in AlN preparation processes. Through the sintering optimization, the oxygen element from the hydrolysis of AlN surface was fixated in the sintering aid Y2O3. Eventually, without any special process control or additional treatment, the final sintered AlN ceramics prepared by the developed slurry present a full densification and the highest thermal conductivity (up to 187.9 W∙m−1∙K−1) of any known additive manufactured ceramics.

• Pressureless two-step sintering of W-10Re and Mo has been demonstrated. • 98.4% dense W-10Re with an average grain size of 260 nm can be pressurelessly sintered below 1200 °C. • 98.3% dense Mo with an average grain size of 290 nm can be pressurelessly sintered below 1120 °C. • W-10Re and W have similar grain boundary diffusivity at the same homologous temperature and similar activation energy. • Mo has more sluggish grain boundary diffusivity and larger activation energy. • Pressureless two-step sintering to be a general method to produce dense ultrafine-grained refractory metals and alloys. The challenge of sintering ultrafine-grained refractory metals and alloys to full density is hereby addressed by pressureless two-step sintering in tungsten-rhenium alloy and pure molybdenum. Using properly processed nano powders (∼50 nm average particle size), we are able to sinter W-10Re alloy to 98.4% density below 1200 °C while maintaining a fine grain size of 260 nm, and sinter molybdenum to 98.3% density below 1120 °C while maintaining a fine grain size of 290 nm. Compared to normal sintering, two-step sintering offers record-fine grain sizes and better microstructural uniformity, which translates to better mechanical properties with higher hardness (6.3 GPa for tungsten-rhenium and 4.0 GPa for molybdenum, both being the highest in all pressurelessly sintered samples of the respective material system) and larger Weibull modulus. Together with our previous demonstration in tungsten, we believe that two-step sintering is a general effective method to produce high-quality fine-grained refractory metals and alloys, and the lessons learned here are transferable to other materials for powder metallurgy. [ABSTRACT FROM AUTHOR]

Aqueous Zn/MnO2batteries exhibit huge potential for grid-scale energy storage but suffer from poor cycling stability derived from both structural instability of cathode and Zn dendrite growth of anode. Here, we report a high-performance aqueous Zn/MnO2battery with ZnSO4-based electrolyte, comprising a nanoparticle-like cathode with abundant surface oxygen defects (MO-Vo) and a dendrite-free Zn anode. The transformation from nanowire (α-MnO2) to nanoparticle (MO-Vo) was found by tuning the annealing conditions in an argon flow. Moreover, the small size of MO-Vonanoparticles can effectively promote the spatially uniform distribution of volume stress during carrier intercalation, boosting the structural stability of the MO-Vocathode. Moreover, it was found that the intercalation pseudocapacitive behavior of Zn2+in the MO-Vocathode can be strongly boosted by tailoring the surface oxygen defect of MnO2based on the calculations and experiments, thereby achieving enhanced cycling stability and redox kinetics. Additionally, the addition of K2SO4additive into the electrolyte can tailor the deposition behavior of Zn2+, enabling stable Zn stripping/plating without dendrites. Therefore, the assembled Zn/MO-Vobatteries exhibit a high energy density and excellent long-term cyclability over 1400 cycles. Besides, the reaction mechanism of pseudocapacitive Zn2+intercalation and H+intercalation for the MO-Vocathode was revealed via ex situ characterizations.

Diamond reinforced silicon carbide matrix composites (diamond/SiC) with high thermal conductivity were prepared by tape casting combined with Si vapor infiltration for thermal management application. The effects of the mixing mode of bimodal diamond particles on the microstructure, thermal and mechanical properties of the composites were analyzed. The results reveal that the thermal conductivity of composites is affected significantly by mixing mode of diamond. In general, when the content of large diamond remains constant, adding a slight amount of small diamond was found to be effective in improving the thermal conductivity of the composite. However, excess small diamonds added will decrease thermal conductivity due to its high interfacial thermal resistance. The maximum thermal conductivity of obtained diamond/SiC is 469 W/(m K) when 38 vol% large diamond and 4 vol% small diamond were added. Such a result can be attributed to the formation of efficient heat transfer channels within the composite and sound interfacial bonding between diamond and SiC phase. Diamond/SiC with high thermal conductivity are expected to be the next generation of electronic packaging substrate.

[Display omitted] • Porous FeAl alloys were fabricated by elemental powder sintering. • Fundamental mechanism of phase transformations was probed by neutron diffraction. • The swelling behavior during powder sintering of Fe/Al was investigated. • The aqueous corrosion kinetics of the sintered porous FeAl was studied. This study investigates the phase transformation and microstructure of porous FeAl parts sintered from elemental powder mixtures using in-situ neutron diffraction and in-situ thermal dilatometry. A single B2 structured FeAl phase was determined in the sintered FeAl alloy. The combined effects of the Kirkendall porosity, transient liquid phase, and phase transformations associated with powder sintering all contribute to the swelling phenomenon of the final sintered part. The aqueous corrosion test indicates that the corrosion products include iron oxides in the porous FeAl parts. The accumulation of corrosion products blocks the pore channel and decreases pore size and permeability over the soaking time. [ABSTRACT FROM AUTHOR]

As an emerging optoelectronic material, colloidal lead halide perovskite nanocrystals (PeNCs) have attracted considerable interest, but the fundamental and crucial formation mechanism of PeNCs is still unclear due to the fast speed of the chemical synthesis. Here, we developed a novel stepwise method to explore the formation process of CsPbBr3PeNCs. Polar alcohol was used to trigger the formation reaction of PeNCs, thereby controlling the reaction speed and achieving stepwise synthesis. Our work found that the synthesis of PeNCs undergoes three formation steps: PbBr3–complexes, PbBr64–octahedrons, and perovskite crystals. The PbBr3–complexes were first formed through the coordination of Pb2+and Br–ions in the precursor solution and then were transformed into PbBr64–octahedrons by being triggered with the polar alcohol. Finally, the PbBr64–octahedrons reacted with the free-state Cs+ions to form perovskites. The PbBr64–octahedrons should be formed first, otherwise the Cs+ions are always in the free state in the precursor solution so that they cannot react with lead bromide complexes to form perovskite crystals. This study provides new insights into the formation process of PeNCs and new thinking for designing and constructing PeNCs.

Wire arc directed energy deposition (WA-DED) technology has broad application prospects in man-ufacturing large-size and complex metal components due to its low production costs and high depos-ition efficiency. However, pores are still challenging in WA-DED-processed aluminum (Al) alloys. Although many works have been discussed in this field, the relevant studies about the effect of alloying elements on porosity are fewer. In this work, Al alloy wires with 0.36Sc and 0.11Zr (LAEW, wt%) and 0.72Sc and 0.23Zr (HAEW) were selected to fabricate single-pass multi-layer compone-nts with different welding speeds, and the pores were analyzed by X-ray computed tomography (XCT) technology. As the content of Sc and Zr elements increased, the density of Al-Mg-Sc-Zr components significantly decreased. The highest porosity, number density, and the largest average diameter of pores in components with HAEW were about 7.37 %, 6.04 × 102/mm3, and 46.77 ± 29.31 μm, respectively, which were significantly higher than those of LAEW. The second phases of all components were mainly Al3(Sc1-x, Zrx) phases. Compared to LAEW, the Al3(Sc1-x, Zrx) phases of components with HAEW had a larger area fraction and average diameter, as well as a higher number density at the same process parameters, the highest values were around 3.00 %, 1.27 ± 0.89 μm, and 15.20 × 103/mm2. Al3(Sc1-x, Zrx) phases could not only serve as the nucleation cores of bubbles but also hinder bubbles escape. In addition, the Sc element significantly increased the viscosity of Al melt. Therefore, the main influencing factors of pores in components with HAEW were not only process parameters, but also the Al3(Sc1-x, Zrx) phases. However, for LAEW, the process parameters were the major influencing factors on porosity due to lower area fraction and number density of Al3(Sc1-x, Zrx) phases. This work has laid a theoretical foundation for WA-DED-processed high-strength Al-Mg-Sc-Zr alloys.

Multi-material laser powder bed fusion has long been a challenge in additive manufacturing, especially in terms of controlling spatial variations and joining multiple materials. The challenge is even greater when multi-material components have different physical properties (e.g., different thermal expansions, thermal conductivities and laser reflectivities). The aforementioned scenario is applicable to copper–nickel (Cu–Ni) alloy. The simultaneous printing and controllable mixing of pure Cu and pure Ni within a single print have not been accomplished due to the substantial disparity in the physical properties of pure Cu and pure Ni. In this work, a full composition with different mixing proportions (100 % Cu to 100 % Ni) was fabricated in a single printing process through in-situ alloying based on our process of micro laser powder bed fusion. A transition from a columnar grain to a quasi-equiaxed grain morphology with texture variation from <110> to <111> was found in the full–composition–gradient of the Cu–Ni alloy. Microstructural variations, such as fine grain strengthening and grain boundary strengthening, greatly affected the mechanical properties of the alloys: the ultimate tensile strength ranged from 303 to 488 MPa and the yield strength ranged from 231 to 445 MPa. Moreover, the electrical conductivity of the alloys with a compositional gradient ranged from 3.6 % IACS to 96 % IACS due to the electron scattering induced by lattice distortion. In summary, a full-composition Cu–Ni gradient alloy was fabricated through in-situ alloying adopting micro laser powder bed fusion for the first time, enabling the investigation of the evolution of the microstructure and properties of the alloy as the alloy composition varies.

Energy transmission efficiency and stability place higher demands on electrical power systems. Aluminium nitride (AlN) ceramics, which possess high thermal conductivity and electrical insulation, are gradually used in heat dissipation systems for high-power semiconductors. However, oxygen impurity has been one of the key factors limiting the thermal conductivity of AlN ceramics. The pre-reduction treatment was used to reduce the powder oxygen content. AlN ceramics with low oxygen impurities were then obtained by hot-pressing sintering. The decrease in the oxygen content of the powder shows a hindering effect on densification, which increases the sintering temperature to 1750°C. The pre-reduced powders transform the grain edge phase from YAP to YAM, which is more favourable for purifying the lattice. The variations in grain size and mechanical properties are also discussed. Eventually, AlN ceramics with a thermal conductivity of 201 W m-1K-1and a flexural strength of 376 MPa are obtained.

Ti alloys with lattice structures are garnering more and more attention in the field of bone repair or regeneration due to their superior structural, mechanical, and biological properties. In this study, six types of composite lattice structures with different strut radius that consist of simple cubic (structure A), body-centered cubic (structure B), and edge-centered cubic (structure C) unit cells are designed. The designed structures are firstly simulated and analysed by the finite element (FE) method. Commercially pure Ti (CP–Ti) lattice structures with optimized unit cells and strut radius are then fabricated by selective laser melting (SLM), and the dimensions, microtopography, and mechanical properties are characterised. The results show that among the six types of composite lattice structures, combined BA, CA, and CB structures exhibit smaller maximum von-Mises stress, indicating that these structures have higher strength. Based on the fitting curves of stress/specific surface area versus strut radius, the optimized strut radius of BA, CA, and CB structures is 0.28, 0.23, and 0.30 mm respectively. Their corresponding compressive yield strength and compressive modulus are 42.28, 30.11, and 176.96 MPa, and 4.13, 2.16, and 7.84 GPa, respectively. The CP-Ti with CB unit structure presents a similar strength and compressive modulus to the cortical bone, which makes it a potential candidate for subchondral bone restorations.

This review comprehensively summarizes the state-of-the-art progress in electrospun electrode materials for sodium-ion batteries, with the electrospinning parameters modulating strategies, the electrode structure-performance correlations, and the future developing directions illuminated.

In this study, the influences of La 2 O 3 added on the phase, morphology and reduction process of tungsten oxide prepared by solution combustion synthesis (SCS) were investigated for the first time. And tungsten nanopowders with different La 2 O 3 doping amount (0.5∼5.0 wt%) were successfully prepared by SCS and followed hydrogen reduction. The results showed that with the increase of La 2 O 3 addition, the product synthesized by SCS changed from needle-like W 18 O 49 to irregularly granulated H 0.53 WO 3 and the complete reduction temperature also increased form 700 ℃ to 850 ℃. The densification behavior of as-prepared W nanopowders revealed that the densification inhibitory effect of La 2 O 3 was enhanced as the La 2 O 3 addition increased. Nevertheless, due to the optimal size and distribution of La 2 O 3 particles, the sample with 2.0 wt% La 2 O 3 addition has a smallest grain size of 0.47 μm and a highest microhardness value of 739.3 Hv 0.2 , which are the best compared with the literature. [ABSTRACT FROM AUTHOR]

In this study, corrosion, wear, and tribocorrosion of Ti-16Mo alloy manufactured by powder metallurgy (PM) in phosphate-buffered saline are investigated. The results indicate that the corrosion rate of Ti-16Mo alloy increases about 100 times from 0.00009 mm/yr to 0.00851 mm/yr under the tribocorrosion condition. Also, corrosion accelerates wear loss, and wear increment rate due to the corrosion (4.7715 mm/yr) of Ti-16Mo alloy is about 40% of pure mechanical wear rate (11.78 mm/yr). Compared with as-cast pure Ti (23.70999 mm/yr) and Ti-6Al-4 V (17.12003 mm/yr), Ti-16Mo alloy exhibits the lowest materials loss of 16.56001 mm/yr making it become a promising alloy for bone-tissue applications.

When biomaterials are implanted in the human body, the surfaces of the implants become favorable sites for microbial adhesion and biofilm formation, causing peri-implant infection which frequently results in the failure of prosthetics and revision surgery. Ti–Mo alloy is one of the commonly used implant materials for load-bearing bone replacement, and the prevention of infection of Ti–Mo implants is therefore crucial. In this study, bacterial inhibitory copper (Cu) was added to Ti–Mo matrix to develop a novel Ti–Mo–Cu alloy with bacterial inhibitory property. The effects of Cu content on microstructure, tensile properties, cytocompatibility, and bacterial inhibitory ability of Ti–Mo–Cu alloy were systematically investigated. Results revealed that Ti–10Mo–1Cu alloy consisted of α and β phases, while there were a few Ti2Cu intermetallic compounds existed for Ti–10Mo–3Cu and Ti–10Mo–5Cu alloys, in addition to α and β phases. The tensile strength of Ti–10Mo-xCu alloy increased with Cu content while elongation decreased. Ti–10Mo–3Cu alloy exhibited an optimal tensile strength of 1098.1 MPa and elongation of 5.2%. Cytocompatibility study indicated that none of the Ti–10Mo-xCu alloys had a negative effect on MC3T3-E1 cell proliferation. Bacterial inhibitory rates against S. aureusand E. coliincreased with the increase in Cu content of Ti–10Mo-xCu alloy, within the ranges of 20–60% and 15–50%, respectively. Taken together, this study suggests that Ti–10Mo–3Cu alloy with high strength, acceptable elongation, excellent cytocompatibility, and the bacterial inhibitory property is a promising candidate for biomedical implant applications.

Novel anode materials are of paramount significance for the development of advanced Li- and K-ions batteries with high energy density, favorable rate capability, and long lifespan. We herein construct a delicate three-dimensional (3D) hierarchical porous carbon networks uniformly decorated with FeSe2nanodots (FeSe2@PCN) for fast and stable lithium/potassium storage. The FeSe2@PCN features a honeycomb-like architecture made up of countless cross-linked N-doped carbon membranes, which is synthesized via a simple and scalable gas-pumped self-expanding approach. The well-integrated porous carbon network (PCN) matrix not only can facilitate ion/electron transportation and offer sufficient active sites for Li+/K+adsorption but also accommodate the volumetric change of decorated FeSe2nanodots during lithiation/potassiation to maintain the integrity of electrode materials. Thus, FeSe2@PCN displays exceptional electrochemical properties for lithium storage in terms of high capacity (1150 mAh g–1after 100 cycles at 200 mA g–1) and outstanding cyclic stability (232 mAh g–1after 5000 cycles at 10 A g–1). When further used in KIBs, it delivers a superior capacity of 390 mAh g–1at 100 mA g–1and retains 128 mAh g–1after 500 cycles at 2 A g–1.

A ternary Ti35Zr28Nb alloy was fabricated by powder metallurgy (PM) from pre-alloyed powder. The microstructure, hardness, corrosion behavior, and wear response of the produced alloy were investigated systematically. The results show that nearly full dense Ti35Zr28Nb alloy (relative density is 98.1 ± 1.2 %) can be fabricated by PM. The microstructure was dominated with uniform β phase. The Ti35Zr28Nb alloy displayed spontaneous passivity in a naturally aerated simulated body fluid (SBF) solution at 37 ± 0.5 °C. The Ti35Zr28Nb alloy exhibited the highest corrosion resistance as compared to as-cast Ti6Al4V and pure Ti because of the formation of a protective passive film containing TiO 2 , Nb 2 O 5 , and ZrO 2 , including the highest corrosion potential (−0.22 ± 0.01 V), the lowest corrosion current density (57.45 ± 1.88 nA), the lowest passive potential (0.05 ± 0.01 V) and the widest passivation range (1.29 ± 0.09 V). Under the same wear condition, the wear rate of the Ti35Zr28Nb alloy (0.0021 ± 0.0002 mm3/m·N) was lower than that of the CP Ti (0.0029 ± 0.0004 mm3/m·N) and close to that of the Ti6Al4V (0.0020 ± 0.0003 mm3/m·N). The wear mechanism of the Ti35Zr28Nb alloy was mainly dominated by abrasive wear, accompanied by adhesive wear. The highest corrosion resistance together with the adequate wear resistance makes the PM-fabricated Ti35Zr28Nb alloy an attractive candidate for orthopedic implant materials. [ABSTRACT FROM AUTHOR]

The performance of high-speed steel (HSS) powder is a prerequisite for the preparation of high-performance powder metallurgy HSS. The physical properties, microstructure, and solidification characteristics of HSS powder prepared by nitrogen gas atomisation were systematically studied and analysed in detail. For the atomised TPM558 HSS powder, the morphology is spherical and the particle size distribution is wide. The smooth small particles of satellite powder attach to the surface of large particles. Shrinkage pits caused by solidification shrinkage exist on the surface of large particles. The average cooling rate is between 104and 106K·s−1, with the increase of cooling rate, the powder surface tends to be smooth, and the grain structure is transformed in the order of cellular to dendritic to radial. The single powder particle surface shows fine-equiaxed grains, while the internal presents columnar grains. The crystalline phases of the powder are austenite, ferrite, martensite, and carbide, and the carbide includes MC carbide with face-centred structure and M2C carbide with hexagonal structure. The average nano-hardness of the powder is 9.93 GPa, resulting in poor formability, and it can be pressed and formed only after adding binder.

Potassium-ion batteries are potential alternatives to lithium-ion batteries for large-scale energy storage considering the low cost and high abundance of potassium. However, it is challenging to obtain stable electrode materials capable of undergoing long-term potassiation/depotassiation due to the high accumulated stress associated with the huge volume variation of the electrode. Here, we simulate the von Mises stress distributions of four different carbon three-dimensional models under an isotropic initial stress by the finite element method and reveal the critical role of the structure of a hollow multihole bowl on the strain–relaxation behavior. In this regard, nitrogen/oxygen codoped carbon hollow multihole bowls (CHMBs) are synthesized viahydrothermal carbonization coupled with an emulsion-templating strategy using biomass as the carbon source. Consistent with our simulation results, the CHMB anode remains stable for over 1000 cycles and delivers a high reversible capacity of 304 mAh g–1at 0.1 A g–1. In addition to the reduced stress accumulation, the good electrochemical performances are also attributed to the surface capacitive mechanism and the shortened electron/ion transport distance in CHMBs. In particular, the CHMB composite electrode has a volumetric specific capacity 56% higher than that of hollow spheres due to the high tapped density of the bowl-shaped particles.

A newly developed porous Ti35Zr28Nb scaffold was manufactured via powder metallurgy (PM) using space-holder (NH4HCO3) sintering from pre-alloyed powder. The pore features, compression and anti-corrosion properties of the manufactured porous scaffolds were systematically studied. The results show that all the manufactured porous Ti35Zr28Nb scaffolds consisted of a single β phase. The porosity of the porous Ti35Zr28Nb scaffolds increased from 50% to 65% with in increasing the NH4HCO3from 63% to 79% (volume ratio), and the average pore size (d50) was in the range of 230–430 μm. The yield strength in compression and the elastic modulus of the porous Ti35Zr28Nb scaffolds both decreased gradually with an increase in porosity, varying from 230.5 MPa to 79.7 MPa and 6.9 GPa to 1.8 GPa, respectively. The corrosion rate of the porous Ti35Zr28Nb scaffolds in the phosphate buffer saline (PBS) solution increased from 0.91 × 10−3 mm/yr to 4.18 × 10−3 mm/yr with an increase in porosity from 51.4% to 64.9%. In comparison with unalloyed Ti scaffolds with almost the same porosity, the porous Ti35Zr28Nb scaffolds showed a significantly higher compressive yield strength and a lower corrosion rate. These results suggest that porous Ti35Zr28Nb scaffolds fabricated by PM have substantial potential for hard-tissue engineering applications. Additionally, the relationship of porosity, mechanical and anti-corrosion properties of these Ti35Zr28Nb scaffolds has now been confirmed, and could be used in the process of material selection for their specific applications.

Porous Ti-10Mo alloys were fabricated by powder metallurgy using a space-holder method. The pore characteristics, microstructure, mechanical properties, in vitrobiocompatibility, and in vivo osseointegration of the fabricated alloys were systematically investigated. The results show that with different weight ratios of the space-holder (NH4HCO3) added, all of the porous Ti-10Mo alloys sintered at 1,300°C exhibited a typical Widmanstätten microstructure. The porosity and average pore size of the porous structures can be controlled in the range of 50.8%–66.9% and 70.1–381.4 μm, respectively. The Ti-10Mo alloy with 63.4% porosity exhibited the most suitable mechanical properties for implant applications with an elastic modulus of 2.9 GPa and a compressive yield strength of 127.5 MPa. In vitro, the alloyconditioned medium showed no deleterious effect on the cell proliferation. The cell viability in this medium was higher than that of the reference group, suggesting non-toxicity and good biological characteristics of the alloy specimens. In vivo, after eight weeks’ implantation, new bone tissue formed surrounding the alloy implants, and no noticeable inflammation was observed at the implantation site. The bone bonding strength of the porous Ti-10Mo alloy increased over time from 46.6 N at two weeks to 176.4 N at eight weeks. Suitable mechanical properties together with excellent biocompatibility in vitroand osteointegration in vivo make the porous Ti-10Mo fabricated by powder metallurgy an attractive orthopedic implant alloy. 本文中, 我们以元素粉末为原料, 采用粉末冶金造孔剂法制备了多孔Ti-10Mo合金, 系统探讨了所制备的多孔Ti-10Mo合金的孔隙特 征、显微组织、力学性能、体外生物相容性及体内骨整合能力. 结果表明, 随着造孔剂含量的增加(碳酸氢铵),在1300°C下烧结的多孔Ti- 10Mo合金均由魏氏体组织组成. 所制备的Ti-10Mo合金的孔隙率与平均孔尺寸能够分别控制在50.8%–66.9%与70.1–381.4 μm. 孔隙率为 63.4%的Ti-10Mo合金具有最适合植入应用的力学性能, 其弹性模量为2.9 GPa, 抗压屈服强度为127.5 MPa. 在体外, Ti-10Mo合金浸提液 对细胞增殖没有不良影响. 细胞在浸提液中的存活率高于对照组, 表明合金无毒性并且具有良好的生物学特征. 在体内, 植入8周后合金周 围被新生骨包围, 并且植入部分未见明显炎症. 随着植入时间由2周增加到8周, 多孔Ti-10Mo合金的骨结合强度从46.6 N增加到176.4 N. 适 合的力学性能以及良好的体外生物相容性和体内骨整合性使粉末冶金法制备的多孔Ti-10Mo成为一种具有吸引力的骨科植入合金.

Graphical abstract Abstract Micro-fine sphericalpowders are recommended for selective laser melting (SLM). However, they are mostly expensive due to the complex manufacturing technique and low yield. In this paper, using low-cost treated hydride-dehydride (HDH) Ti powders, commercial pure Ti (CP-Ti) was successfully fabricated by SLM. After 4-h milling, the resulting powders become near-spherical with no obvious angularity, and have optimal flowability with the apparent density of 1.64 ± 0.02 g/cm3, tap density of 2.10 ± 0.04 g/cm3, angle of repose 40.11°±0.09°, and Carr's index of 77.74 ± 0.15. The microstructure was determined with full acicular martensitic α′ phase. The CP-Ti can achieve superior mechanical properties with the ultimate tensile strength of 876.1 ± 20.5 MPa and elongation of (14.7 ± 0.5)%, which exhibit distinctly competitive compared to the as-cast CP-Ti or Ti-6Al-4V. Excellent mechanical properties together with its low-cost make SLM-fabricated CP-Ti from modified HDH Ti powders show promising applications. [ABSTRACT FROM AUTHOR]

The liquid metal battery (LMB) is an attractive chemistry for grid-scale energy-storage applications. The full-liquid feature significantly reduces the interface resistance between electrode and electrolyte, endowing LMB with attractive kinetics and transport properties. Achieving a high energy density still remains a big challenge. Herein, we report a low-melting-point antimony–bismuth-tin positive electrode for LMB with high energy density and excellent rate performance for the first time. The electromotive force of Li||Sb–Bi–Sn system is determined by Li||Sb and Li||Bi chemistries. The Sn component plays a bifunctional role in the chemistry, decreasing the melting point of Sb–Bi–Sn alloy and providing rapid lithium diffusion paths for the electrode reaction. The ternary feature of the positive electrode ensures a low Sn concentration for the eutectic requirement of the positive electrode working at moderate temperature (500 °C). The stepwise reaction characteristics of Sb and Bi provides a dynamic microstructure change of intermediate compounds during the charge/discharge process, allowing the electrolyte to penetrate and make contact with the positive electrode to enable a fast electrode reaction. A synergetic combination of these advantages enables the reported Sb–Bi–Sn electrode to demonstrate a high energy density of about 260 Wh kg–1and excellent rate capability with almost no capacity degradation at different current densities from 200 to 1200 mA cm–2. All these excellent properties demonstrate that the Sb–Bi–Sn alloy is an ideal positive electrode of LMB for large-scale applications.

The performance of Li||Sb-Sn liquid metal batteries (LMBs) is hindered by the corrosion of the Sb-Sn cathode on its current collector. Herein, a uniform, dense, and low-oxidized W coating was prepared by plasma spraying, which can effectively resist the corrosion of the cathode and improve the cycle stability of the Li||Sb-Sn LMBs. For the first time, micro-CT nondestructive inspection is applied in the field of LMBs. The corrosion micromorphology and composition evolution of the SS304 matrix and Sb-Sn cathode with or without the plasma-sprayed W coating is obtained without disassembling the battery, which proves that the W coating can effectively protect the SS304 matrix. Our autonomous new LMB device for nondestructive inspection is universal and can be applied to different LMBs systems for advancing knowledge of corrosion mechanism and protection. This work guarantees the ability to directly visualize the inner critical positions in three dimensions and fills the knowledge gap in the field of LMB detection technology.

ABSTRACTIn this paper, the composite of low alloy steel reinforced with TiC particles was prepared by conventional powder metallurgy process. The effects of the combined carbon content of TiC powder, sintering temperature and heating rate on the composite were studied. The results showed that the selected TiC powder has a combined carbon content of 17.91 wt-% and the optimal sintering process is heating from 600 to 1440°C at a rate of 1°C min−1and holding for 1 h at 1440°C. The composite after heat treatment has excellent mechanical properties with density of 6.45 g cm−3, hardness of 68–69 HRC and TRS of 1763 MPa, respectively, and will be used as wear-resistant parts, assembly fixtures, moulds, etc.

In this paper, the composite of low alloy steel reinforced with TiC particles was prepared by conventional powder metallurgy process. The effects of the combined carbon content of TiC powder, sintering temperature and heating rate on the composite were studied. The results showed that the selected TiC powder has a combined carbon content of 17.91?wt-% and the optimal sintering process is heating from 600 to 1440°C at a rate of 1°C?min-1and holding for 1?h at 1440°C. The composite after heat treatment has excellent mechanical properties with density of 6.45?g?cm-3, hardness of 68–69 HRC and TRS of 1763?MPa, respectively, and will be used as wear-resistant parts, assembly fixtures, moulds, etc.

Through a novel preparation process, 50 μm diamond particles are successfully filled into the gaps formed by closely arranged 400 μm diamond particles, thereby obtaining diamond/SiC composites with high diamond content and uniform structure. The diamond volume fraction and thermal conductivity of the composite are 79.18% and 722.55 W/mK, respectively, both are the maximum values of the diamond/SiC composites prepared by pressureless infiltration at present. The innovative preparation method provides a new solution for the uniform mixing of particles of different sizes in composites.

Three-dimensional (3D) carbon fiber (CF) networks were constructed by electrodeposition using Cu foam as template, and then 3D CF/Cu composites were prepared by hot pressing sintering. Experimental investigations revealed the successful formation of a well-connected 3D CF network embedded within the Cu matrix. The constructed 3D CF networks are conducive to establishing effective heat transfer channels in the composites. The thermal conductivity of the 3D CF/Cu composite with 20 vol% CF in the X–Y plane and Z plane are 418 ± 3 Wm−1K−1and 415 ± 5 Wm−1K−1, respectively. The thermal conductivity of the composites is significantly enhanced, and the thermal conductivity becomes isotropic. Additionally, the construction of the 3D CF network promotes efficient heat transfer in CF/Cu composites, providing a promising strategy for the development of advanced CF/metal thermal management materials.

Brake pads play a vital role in controlling the operation of high-speed trains with over 300 km/h. Currently the copper-based composites produced by powder metallurgy techniques have been proved as one of the ideal materials. However，the braking performance is strongly influenced by the chemical composition, production, microstructure as well as the working conditions. The intrinsic mechanism of the thermal fade and wear loss under thermal and mechanical coupled influence has not yet been fully revealed. As of late, machine learning algorithms have attracted widespread attention and extraordinary results has been accomplished in materials science and engineering. In this study the algorithms for predicting the braking performance of copper-based brake pads are developed. A new PM copper-based alloy, was designed via the models of the coefficient of friction (COF) and wear loss. The braking test results of this alloy show that the average COF was 0.37 at stable stage I and thermal recession decrease only 0.012 at stage II when under 350 km/h/0.48 MPa continuous braking for 10 times. And the total wear loss is only 1.30 g when under braking from 200 km/h to 350 km/h with pressure from 0.31 MPa to 0.48 MPa. Compared with the commercial brake pads, our designed alloy exhibits excellent braking performance with COF for thermal fade reduced to 21% and the total wear loss reduced to 20%.

Diamond/SiC composite with 3D connected diamond as the reinforcements are prepared for the first time using the foam SiC as a template. The fabricated composite consisted of diamond, SiC and residual Si; nearly fully dense composite obtained by liquid Si infiltration as densification process. The results show that construction of efficient diamond heat transport channels in composite can greatly improve its thermal conductivity. Finally, the thermal conductivity of 3D connected diamond particles reinforced diamond/SiC composite reached up to 298 W/mk, at diamond volume fraction of only 26 vol%, which is almost the same as that of composite with 38 vol% diamond in the literature. Construction of heat transfer channels greatly reduces the diamond content in the diamond/SiC composite, effectively decreasing its preparation cost and providing a new development direction for diamond/SiC composite.

Two-step dipping is one of the popular low temperature solution methods to prepare organic–inorganic halide perovskite (CH3NH3PbI3) films for solar cells. However, pinholes in perovskite films fabricated by the static growth method (SGM) result in low power conversion efficiency (PCE) in the resulting solar cells. In this work, the static dipping process is changed into a dynamic dipping process by controlled stirring PbI2substrates in CH3NH3I isopropanol solution. The dynamic growth method (DGM) produces more nuclei and decreases the pinholes during the nucleation and growth of perovskite crystals. The compact perovskite films with free pinholes are obtained by DGM, which present that the big perovskite particles with a size of 350 nm are surrounded by small perovskite particles with a size of 50 nm. The surface coverage of the perovskite film is up to nearly 100%. Such high quality perovskite film not only eliminated pinholes, resulting in reduced charge recombination of the solar cells, but also improves the light harvesting efficiency. As a result, the PCE of the perovskite solar cells is increased from 11% for SGM to 13% for DGM.

Metal hydrides high temperature thermal heat storage technique has great promising future prospects in solar power generation, industrial waste heat utilization and peak load regulating of power system. This article introduces basic principle of metal hydrides for thermal storage, and summarizes developments in advanced metal hydrides high-temperature thermal storage materials, numerical simulation and thermodynamic calculation in thermal storage systems, and metal hydrides thermal storage prototypes. Finally, the future metal hydrides high temperature thermal heat storage technique is been looked ahead.

The La0.67Mg0.33Ni2.5Co0.5hydrogen storage alloy was prepared by the vacuum intermediate frequency induction furnace followed by annealing treatment. The pulverization degree of both the as-cast and annealed alloy powders after gaseous hydriding and dehydriding cycle was investigated and the discovery was that annealing treatment could hardly ameliorate their anti-pulverization ability. The element content of La, Mg, Ni and Co existing in electrolyte before and after the electrochemical cycles by using ICP-AES technology was also analyzed and it showed that a large amount of La and Mg were dissolved in the electrolyte, but the amount of dissolution for La and Mg significantly declined when the alloy was annealed. The XRD analysis revealed that all the alloys consisted of two main phases AB3and AB2and a residual phase AB5while annealing treatment made the AB2phase decrease slightly. Furthermore, the anti-corrosion abilities of various elements in different phases of the as-cast and annealed alloy samples were studied by analyzing the element (La, Mg, Ni, Co) change with the corrosion time in phases AB3and AB2by means of EDS. It turned out that the element of La was mainly corroded out from the phase AB2while not easily from the phase AB3. However, the element of Mg was both easily corroded out from the phases AB2and AB3, but the corrosion was more obvious in the phase AB3. Therefore, annealing improved the anti-corrosion performances of La and Mg in the phase AB2.

The catalysis of NiFe2O4nanoparticles on the hydrogen storage performances of magnesium hydride synthesized by high-energy ball milling was studied for the first time. The H2storage performances and catalytic mechanism were studied by pressure–composition–temperature (PCT), differential scanning calorimetry (DSC), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The nonisothermal dehydrogenation results display that the initial dehydrogenation temperature of 7 mol % NiFe2O4-doped MgH2is 191 °C, which is 250 °C lower than that of pristine MgH2. The desorption kinetics displays that the MgH2+7 mol % NiFe2O4sample could desorb 3.79 wt % H2within 1 h at 300 °C under H2pressure of 0.1 MPa. The absorption kinetics displays that the MgH2+7 mol % NiFe2O4sample could absorb 2.06 wt % H2within 3 h near room temperature under H2pressure of 4 MPa. The desorption activation energy of the MgH2+7 mol % NiFe2O4sample is 59.6 kJ/mol, decreasing 195.3 kJ/mol as compared with pristine magnesium hydride. The reaction enthalpy and entropy of the MgH2+7 mol % NiFe2O4sample during the dehydrogenation process are improved. The enhancement in the H2storage performances of MgH2by adding NiFe2O4nanoparticles is primarily ascribed to intermetallic Fe7Ni3and (Fe,Ni) phases during the desorption procedure, which act as the real catalyzer in the 7 mol % NiFe2O4-doped sample.

AbstractMicrostructural evolution of secondary γ′ precipitates in superalloy FGH96 under various aging treatments after 1200 °C solution treatment was investigated. The results indicate that particle size of secondary γ′ precipitates increases from about 73 μm to about 587 μm with the increasing of aging temperature in the range of 850–1120 °C, and the shape of secondary γ′ precipitates changes from spherical to cuboidal, and to butterfly-like with the increase of aging temperature. In case of the aging temperature of 1120 °C, the γ′ precipitates change into butterfly-like and the size is the largest. When the aging temperature reached 1140 °C, the γ′ precipitates are refined.