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• Real-time stress evolutions in the nanocrystalline films upon heating were investigated by in situ synchrotron X-ray diffraction. • The total stress in the films can be separated into thermal stress, grain-growth stress, and intrinsic stress. • The addition of solute Mo can modify grain boundaries during heating, including grain-boundary amorphization, grain-boundary relaxation, and grain-boundary segregation. • The intrinsic role of solute on stress development in the nanocrystalline films has been disclosed. The effect of the solute (Mo) on the stress development of nanocrystalline Ni and Ni–Mo films upon heating has been investigated in real time using in situ synchrotron X-ray diffraction. The complex and distinct relationship between the film stress and grain boundaries (GBs) has been examined by the evolution of real-time intrinsic stress in combination with the in situ grain growth and thermal characterizations. The different intrinsic stress evolutions in the Ni and Ni–Mo films during the heating process result from the modification of GBs by Mo alloying, including GB amorphization, GB relaxation, and GB segregation. It has been found that GBs play a vital role in the stress development of nanocrystalline films. The addition of a solute can not only inhibit grain growth but also influence the stress evolution in the film by changing the atomic diffusivity at the GBs. This work provides valuable and unique insights into the effect of solutes on stress development in nanocrystalline films during annealing, permitting control of the film stress through solute addition and heat treatment, which is critical for improving the design, processing, and lifetime of advanced nanocrystalline film devices at high temperatures. [ABSTRACT FROM AUTHOR]

• High-valence metal sites are formed via MXene coupling and phosphorization. • In-situ Raman confirms the TMP are easily transferred into active species MOOH. • DFT reveals the strong electronic interaction between TMP and MXene. • NiFeCoP/MXene exhibits excellent OER performance (η 10 : 240 mV). Exploring low-cost, high-performance, and stable electrocatalysts toward the oxygen evolution reaction (OER) is highly desired but remains challenging. Transition metal hydroxide has been wildly utilized as a promising candidate, but practical implementation is impeded by insufficient catalytic activity, easy agglomeration, and poor conductivity. Here, we report that both phosphorization and combination with MXnene can improve the catalysts' intrinsic activity and conductivity. Besides, MXene also prevents the agglomeration of the nanoparticles, resulting in the enhanced exposure of active sites. Experimental characterizing and density functional theory simulations revealed that P species can attract electrons to promote the formation of high-valence states of adjacent metal atoms, and coupling MXene support can effectively modulate the electronic structure and optimize the d -band center, which boosts the OER performance. Consequently, the optimized NiFeCoP/Mxene catalyst exhibits a low overpotential of 240 mV at a current density of 10 mA cm−2, a small Tafel slope of 55 mV dec−1, and superior long-term stability of 40 h in 1 M KOH electrolyte, which is superior to other counterparts. [Display omitted]. [ABSTRACT FROM AUTHOR]

Oxide-dispersion-strengthened tungsten (ODS-W) and a CuCrZr alloy were bonded by a three-step process: (i) surface nano-activation, (ii) copper plating followed by annealing, and (iii) diffusion bonding. The morphological and structural evolutions of ODS-W and the interface of the ODS-W/CuCrZr joint during these processes have been thoroughly studied by X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry, and high-resolution transmission electron microscopy. After surface nano-activation, a nanoporous structure of ODS-W with an average pore size of ~100 nm was obtained, and the Y 2 O 3 particles therein remained unchanged. A Cu coating was tightly bonded with the surface nano-activated ODS-W after Cu plating and annealing. An interaction layer embedded with nanosized W particles was formed at the interface between ODS-W and plated Cu after the three-step process. Consequently, well-cohesive ODS-W/Cu and ODS-W/Y 2 O 3 /Cu interfaces were formed. The ODS-W/CuCrZr joint showed high shear strengths (up to 201 MPa) and effective bonded area ratios (>98%). The developed three-step bonding process between ODS-W and the CuCrZr alloy provides an effective support for future plasma-facing components in nuclear fusion reactor applications. • High-strength bonding of immiscible ODS-W and CuCrZr was realized by combination of surface nano-activation and Cu plating. • Surface nano-activation of ODS-W was achieved by the sequential anodization and deoxidation annealing. • A Cu coating was tightly bonded with the surface nano-activated ODS-W through controllable Cu plating and annealing. • An interfacial Cu layer embedded with nanosized W particles was formed at the ODS-W/CuCrZr joint interface. • Well-cohesive ODS-W/Cu and ODS-W/Y 2 O 3 /Cu interfaces lead to excellent performance of the ODS-W/CuCrZr joint. [Display omitted] [ABSTRACT FROM AUTHOR]

The effect of thermal treatments on mechanical properties was systematically investigated in Ni/Mo multilayers with a constant modulation period (160 nm) prepared by magnetron sputtering deposition. A supermodulus effect was found in the annealed multilayers as compared to the as-deposited state. A large tensile stress development was observed in the multilayers. The evolution of grain-boundary (GB) wetting was observed at the interfaces of the multilayers, which results in an enhanced modulus based on the mechanism of GB-wetting-induced interfacial stress/strain. The GB wetting phenomenon was further supported by a thermodynamic calculation. The results not only bring clear evidence of the important role of interfacial structures in governing the elastic behavior of metallic multilayers, but also allow designing the multilayers with special properties through atomic diffusion and wetting at the interfaces based on the thermodynamic calculation. [ABSTRACT FROM AUTHOR]

Direct alloying is difficult to be realized in an immiscible Mo-Ag system with a positive formation heat due to the absence of thermodynamic driving force at equilibrium. In this work, a direct alloying method is developed to realize the direct alloying between Mo and Ag and construct Mo-Ag interface. The direct alloying method was mainly carried out through a direct diffusion bonding for Mo and Ag rods at a temperature close to the melting point of Ag (T mAg). Then the microstructure and phase constitution of the as-constructed Mo-Ag interface are characterized. The results show that Mo-Ag metallurgical bonding interface has been constructed successfully, indicating that a direct alloying in the immiscible Mo-Ag system has been realized. Additionally, mechanical tests are carried out for the Mo-Ag joints prepared through the direct alloying method. The test results show that the average maximum tensile strength of the joints is about 107 MPa. The effect of alloying parameters on the tensile strength is also discussed, which shows that there is an effective temperature range for the direct alloying between Mo and Ag. Lastly, an improved thermodynamic model that considers the formation of Mo-Ag crystalline and amorphous phase is presented to reveal the thermodynamic mechanism of the direct alloying. Combining the calculation and differential scanning calorimetry (DSC) tests results, the Gibbs energy diagram for the direct alloying is obtained. It is confirmed that the co-release of storage energy and surface energy can serve as the thermodynamic driving force to overcome the effect of positive formation heat and lead to direct alloying for Mo-Ag systems. [ABSTRACT FROM AUTHOR]

The effect of the γ′+γ two-phase structure on the oxidation behaviors of Ni-Al single-crystal alloys at 650 °C was investigated by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, X-ray diffraction and Auger electron spectroscopy. In the initial oxidation stage, the oxidation behavior is primarily determined by the growth pattern of oxides in the γ channel. The outward convex NiO was formed in unprotected wide γ channels. And Ni-Al spinel oxide provides a great number of short-circuit paths, accelerating the inward diffusion of oxygen and outward diffusion of Ni. In the late stage of oxidation, the elongated internal oxide in the large γ′ phase contributes to the diffusion of oxygen along the oxide/metal interface. Consequently, the Ni-Al single-crystal alloy with wide γ channels and large γ′ precipitates exhibited poor oxidation performance. [ABSTRACT FROM AUTHOR]