Here, we briefly review recent advances in H2 storage technologies relying on mixed proton–hydride and destabilized hydride materials. We establish a general relationship across different materials: the higher the effective H content, the higher the temperatures needed to completely desorb H2. Nevertheless, several systems show promising thermodynamics for H2 desorption; however, the desorption kinetics still needs to be improved by the use of appropriate catalysts. Prompted by the importance of heterolytically splitting stable dihydrogen molecules for proton–hydride technologies, we attempt to theoretically design novel H2 transfer catalysts. We focus mainly on M4Nm4H8 catalysts (M = V, Ti, Zr, Hf, and Nm = Si, C, B, N), which should be able to preserve their functionality in the strongly reducing environment of a H2 storage system. We are able to determine the energy of H2 detachment from these molecules, as well as the associated energy barriers. In order to optimize the properties of the catalysts, we use isoelectronic atom‐by‐atom substitutions, vary the valence electron count, and borrow the concept of near‐surface alloys from extended solids and apply it to molecular systems. We are able to obtain control over the enthalpy and electronic barriers for H2 detachment. Molecules with the coordinatively unsaturated > TiSi < unit exhibit particularly favorable thermodynamics and show unusually small electronic barriers for H2 detachment (> 0.27 eV) and attachment (> 0.07 eV). These and homologous ZrSi frameworks may serve as novel H2 transfer catalysts for use with emerging lightweight hydrogen storage materials holding 5.0–10.4 wt % hydrogen, such as Li2NH, Li2Mg(NH)2, Mg2Si, and LiH/MgB2 (discharged forms). Catalytic properties are also anticipated for appropriate defects on the surfaces and crystal edges of solid Ti and Zr silicides, and for TiSi ad‐units chemisorbed on other support materials.
To satisfy the most stringent criteria in terms of new cardiovascular stents, pure Zn was alloyed with 1 wt pct of Mg and subsequently subjected to plastic deformation, using conventional hot extrusion followed by multi-pass hydrostatic extrusion. A detailed microstructural and textural characterization of the obtained materials was conducted, and mechanical properties were assessed at each pass of deformation process. In contrast to pure Zn, hydrostatically extruded low-alloyed Zn is characterized by a remarkable increase in strength and ductility (YS = 383 MPa, E = 23 pct), exceeding the values needed for stents. Such behavior is associated with a dual microstructure containing fine-grained Zn, alternatively arranged with bands of a fragmented eutectic. Extensive grain refinement was achieved due to the process of continuous dynamic recrystallization. Hydrostatic extrusion changes the initial $$ \langle 10\bar{1}0\rangle $$ ⟨ 10 1 ¯ 0 ⟩ fiber texture to a 〈0002〉 and $$ \langle 10\bar{1}1\rangle $$ ⟨ 10 1 ¯ 1 ⟩ double fiber texture in which the 〈0002〉 component decreases with each pass of hydrostatic extrusion. The gradual evolution of texture components was simulated using a visco-plastic self-consistent model, which confirmed that, during hydrostatic extrusion, secondary slip systems were activated involving mostly the pyramidal one.
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