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• Ni 3 Al alloy shows high OER activity and stability. • The boosted OER activity was ascribed to the γ/γ' phase lattice mismatch. • The increased lattice mismatch facilitated the formation of active β -NiOOH phase. The Ni 3 Al-based alloy has been considered as a robust catalyst for oxygen evolution reaction (OER) due to its long-term durability and acceptable activity. However, related reports about understanding the catalytic mechanism are rare and desirable. Herein, the effect of γ/γ' phase lattice mismatch on the catalytic performance caused by various cooling rates after solution heat treatment was investigated. With decreasing cooling rate, the morphologies of γ′ precipitates transformed from sphere to cube and the lattice mismatch increased from -0.172% to -0.409%. The increased lattice mismatch facilitated the formation of the active β -NiOOH phase and enhanced the intrinsic catalytic activity, resulting in the optimized OER overpotential of 240 mV at a current density of 10 mA cm−2 with a Tafel slope of 66.1 mV dec−1 and a stability of 200 h in 1 M KOH. This work reveals the lattice mismatch effect on OER and provides a potential candidate for OER. [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]

In recent years, the Ti 2 AlNb-based alloys are selected as potential alloys for elevated temperature applications to replace conventional Ni-based superalloys owing to their good creep resistance and oxidation resistance which are related to the O precipitates. In this paper, the precipitation mechanisms of O phase, phase transformation and microstructure control of Ti 2 AlNb-based alloys are reviewed. Ti 2 AlNb-based alloys generally consist of B2/β, α 2 , and O phase with different morphologies which are derived from the various heat treatment processes, including equiaxed α 2 /O particles, bimodal microstructure, and Widmannstätten B2/β + O structures etc. As a newly developed strengthening phase, O precipitates can be precipitated from the B2/β matrix or α 2 phase directly as well as generated by means of peritectoid reaction of α 2 phase and bcc matrix. Microstructural control of the Ti 2 AlNb-based alloys can be implemented by refining the original B2/β grain size and regulating the O precipitates. Multidirectional isothermal forging (MIF) and powder metallurgy technique are two effective methods to refine the original B2/β grains and the morphology and size of O precipitates can be regulated by adding alloying components and pre-deformation process. Moreover, the phase diagram as well as coarsening behavior of Ti 2 AlNb-based alloys in ageing process is also reviewed. For the further application of these alloys, more emphasis should be paid on the deep interpolation of microstructure-property relationship and the adoption of advanced manufacturing technology. [ABSTRACT FROM AUTHOR]

Recently, the γ′-strengthened superalloys are of great interests in high temperature applications due to their excellent high temperature strength which is derived from the γ′ strengthening phase. For these γ′-strengthened superalloys, the changes in morphology, size and distribution of γ′ precipitates due to coarsening during thermal exposure have a significant impact on the properties of alloys. This article briefly summarizes the recent advances on the coarsening behavior of gamma prime precipitates in the recently-developed γ′-strengthened superalloys and its effects on the hot deformation behavior of superalloys, drawing specific examples on Allvac® 718PlusTM and Ni 3 Al-based intermetallic superalloys. It is found that the particle size plays an important role in morphological evolution of γ′ precipitates. For instance, the morphology of γ' precipitates evolves from cuboidal to strip-like or other complex structures in Ni3Al-based intermetallic alloys, while the γ' precipitates in Allvac® 718Plus alloy always present near-spherical morphology due to the relatively small initial particle size. The Lifshitz-Slyozof-Wagner (LSW) theory and its modifications, as well as Trans-Interface Diffusion Controlled (TIDC) theory have been applied to describing the coarsening kinetics of γ' precipitates. Additionally, the hot deformation behavior of γ′-strengthened superalloy is found to be greatly influenced by the coarsening of γ′ precipitates. [ABSTRACT FROM AUTHOR]