Design of nanomaterials for hydrogen storage

The interaction of hydrogen with solids and the mechanisms of hydride formation experience significant changes in nanomaterials due to a number of structural features. This review aims at illustrating the design principles that have recently inspired the development of new nanomaterials for hydrogen storage. After a general discussion about the influence of nanomaterials' microstructure on their hydrogen sorption properties, several scientific cases and hot topics are illustrated surveying various classes of materials. These include bulk-like nanomaterials processed by mechanochemical routes, thin films and multilayers, nano-objects with composite architectures such as core-shell or composite nanoparticles, and nanoparticles on porous or graphene-like supports. Finally, selected examples of recent in situ studies of metal-hydride transformation mechanisms using microscopy and spectroscopy techniques are highlighted

TiFe0.85Mn0.05 alloy produced at industrial level for a hydrogen storage plant

Moving from basic research to the implementation of hydrogen storage system based on metal hydride, the industrial production of the active material is fundamental. The alloy TiFe0.85Mn0.05 was selected as H2-carrier for a storage plant of about 50 kg of H2. In this work, a batch of 5 kg of TiFe0.85Mn0.05 alloy was synthesized at industrial level and characterized to determine the structure and phase abundance. The H2 sorption properties were investigated, performing studies on long-term cycling study and resistance to poisoning. The alloy absorbs and desorbs hydrogen between 25 bar and 1 bar at 55 °C, storing 1.0 H2 wt.%, displaying fast kinetic, good resistance to gas impurities, and storage stability over 250 cycles. The industrial production promotes the formation of a passive layer and a high amount of secondary phases, observing differences in the H2 sorption behaviour compared to samples prepared at laboratory scale. This work highlights how hydrogen sorption properties of metal hydrides are strictly related to the synthesis method

Growth and characterization of amorphous ultrathin ruthenium metal films

Copper interconnect systems in modern microelectronics require the use of one or more liner layers and a capping layer in order to prevent copper diffusion into the other materials of the device. Ruthenium has been suggested as a replacement for the currently-standard Ta/TaN stack used for this purpose due to its low bulk diffusivity of copper and its good adhesion to both substrate materials and copper, but at very low thicknesses the polycrystalline nature of pure Ru allows for diffusion of copper along grain boundaries, resulting in the failure of the barrier. Because amorphous metal alloys do not form grains, amorphous Ru alloys have been examined as a way to eliminate the grain boundary diffusion of copper across the film. Early attempts to produce such films with phosphorus as an alloying element by chemical vapor deposition (CVD) using Ru₃(CO)₁₂ and organic phosphorus precursors such as trimethylphosphine have performed well relative to Ta/TaN as a barrier layer at 5 nm thickness. However, high concentrations of carbon were incorporated into the films during CVD by the P precursors. Carbon increases the resistivity of Ru(P) and adds an unnecessary element to the calculated structure of the amorphous alloy. To reduce resistivity, lower-carbon Ru(P) alloy films are grown at 250 °C using Ru₃(CO)₁₂ and a hydride gas (PH₃) as the P precursor. Diborane (B₂H₆) is used to grow an alternate alloy, Ru(B). Ru(P) and Ru(B) alloys are predicted by first-principles calculations to be amorphous above 20 at.% P for Ru(P) and 10 at.% B for Ru(B). Growth studies revealed amorphous Ru(P) above 17 at.% P and amorphous Ru(B) above 10 at.% B, with polycrystalline films formed at lower concentrations. Both Ru(P) and Ru(B) are found to deposit as smooth, continuous films at the 3 nm thickness. Metal-insulator-semiconductor (MIS) capacitor structures consisting of copper / amorphous alloy / SiO₂ / Si / Al stacks were used to test barrier performance under electrical stress. This testing confirms that the amorphous Ru films perform adequately as Cu diffusion barriers.Chemical Engineerin