Ever more stringent regulations on greenhouse gas emissions from transportation motivate efforts to revisit materials used for vehicles1. High-strength aluminium alloys often used in aircrafts could help reduce the weight of automobiles, but are susceptible to environmental degradation2,3. Hydrogen ‘embrittlement’ is often indicated as the main culprit4; however, the exact mechanisms underpinning failure are not precisely known: atomic-scale analysis of H inside an alloy remains a challenge, and this prevents deploying alloy design strategies to enhance the durability of the materials. Here we performed near-atomic-scale analysis of H trapped in second-phase particles and at grain boundaries in a high-strength 7xxx Al alloy. We used these observations to guide atomistic ab initio calculations, which show that the co-segregation of alloying elements and H favours grain boundary decohesion, and the strong partitioning of H into the second-phase particles removes solute H from the matrix, hence preventing H embrittlement. Our insights further advance the mechanistic understanding of H-assisted embrittlement in Al alloys, emphasizing the role of H traps in minimizing cracking and guiding new alloy design.
With the aim of manipulating the mechanical properties of the recently discussed two-dimensional material MXene, we investigate the effect of alloying. We consider substitutional doping of B and V at Ti and C sites of Ti 2 C. Calculations of quantities such as in-plane stiffness, Young's modulus, and critical strain through rigorous first-principles technique establish that B doping is highly effective in improving the elastic properties. Oxygen passivation of B-doped Ti 2 C in addition to improved elastic properties also exhibits reasonably high critical strains making them ideally suited for applications in flexible devices. Our study further reveals the presence of strong spin-phonon coupling in unpassivated Ti 2 C compounds which influences the mechanical behavior. The damage of Ti 2 C in its magnetic ground state of A-type antiferromagnetic structure is found to occur at much higher strain than that of the nonmagnetic Ti 2 C.
With the aim of manipulating the mechanical properties of the recently discussed two-dimensional material MXene, we investigate the effect of alloying. We consider substitutional doping of B and V at Ti and C sites of Ti 2 C. Calculations of quantities such as in-plane stiffness, Young's modulus, and critical strain through rigorous first-principles technique establish that B doping is highly effective in improving the elastic properties. Oxygen passivation of B-doped Ti 2 C in addition to improved elastic properties also exhibits reasonably high critical strains making them ideally suited for applications in flexible devices. Our study further reveals the presence of strong spin-phonon coupling in unpassivated Ti 2 C compounds which influences the mechanical behavior. The damage of Ti 2 C in its magnetic ground state of A-type antiferromagnetic structure is found to occur at much higher strain than that of the nonmagnetic Ti 2 C.
Metal nanogels combine
a large surface area, a high structural
stability, and a high catalytic activity toward a variety of chemical
reactions. Their performance is underpinned by the atomic-level distribution
of their constituents, yet analyzing their subnanoscale structure
and composition to guide property optimization remains extremely challenging.
Here, we synthesized Pd nanogels using a conventional wet chemistry
route, and a near-atomic-scale analysis reveals that impurities from
the reactants (Na and K) are integrated into the grain boundaries
of the poly crystalline gel, typically loci of high catalytic activity.
We demonstrate that the level of impurities is controlled by the reaction
condition. Based on
ab initio
calculations, we provide
a detailed mechanism to explain how surface-bound impurities become
trapped at grain boundaries that form as the particles coalesce during
synthesis, possibly facilitating their decohesion. If controlled,
impurity integration into grain boundaries may offer opportunities
for designing new nanogels.
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