Octahedral molecular sieves (OMS) are built of transition metal-oxygen octahedra that delimit sub-nanoscale cavities. Compared to other microporous solids, OMS exhibit larger versatility in properties, provided by various redox states and magnetic behaviors of transition metals. Hence, OMS offer opportunities in electrochemical energy harnessing devices, including batteries, electrochemical capacitors and electrochromic systems, provided two conditions are met: fast exchange of ions in the micropores and stability upon exchange. Here we unveil a novel OMS hexagonal polymorph of tungsten oxide called h’-WO3, built of (WO6)6 tunnel cavities. h’-WO3 is prepared by a one-step soft chemistry aqueous route leading to the hydrogen bronze h’-H0.07WO3. Gentle heating results in h’-WO3 with framework retention. The material exhibits an unusual combination of 1-dimensional crystal structure and 2-dimensional nanostructure that enhances and fastens proton (de)insertion for stable electrochromic devices. This discovery paves the way to a new family of mixed valence functional materials with tunable behaviors.
Incorporating boride nanocrystals could significantly impact the mechanical properties of aluminum alloys. Molten salts synthesis offers opportunities to fabricate superhard boride nanoparticles, which can sustain the harsh conditions of liquid metallurgy synthesis, thus enabling liquid-phase design of metallic nanocomposites. Here we unveil HfB 2 -Al nanocomposites with molten salt-derived HfB 2 nanoparticles incorporated by ultrasound-assisted casting. Using sequential dilutions, the nanoparticles were incorporated in Al with macroscale homogeneity. The crystal structure and size of the nanocrystals is retained in the final nanocomposites, supporting their excellent chemical stability. Semi-coherent interfaces between the nanoparticles and the matrix are then evidenced by transmission electron microscopy, thus suggesting that the nanocrystals could act as nuclei for the solidification of Al and then limit the Al grain size to< ca. 20 µm. Nanoindentation measurements revealed significant grain boundaries strengthening effect. We finally show that HfB 2 nanoparticles also enable a strong decrease in matrix grain size and an increase in the hardness of the AlSi 7 Cu 0.5 Mg 0.3 cast alloy. This proof-of-concept material is paving the way to new light-weight Al matrix nanocomposites doped by molten-salt synthesized nanoparticles.
Metal matrix nanocomposites encompassing low-melting point metal nano-inclusions are promising candidates for thermal regulation of devices at high temperature. They are usually processed by solid-state routes that provide access to a limited range of materials and are hardly compatible with complex shaping processes and with large-scale applications. Herein, we develop a liquid-phase processing technique to design aluminum matrix nanocomposites made of phase change nanoparticles, using bismuth nanoparticles as a proof-of-concept. The bismuth nanoparticles derived from colloidal chemistry are first encapsulated in a silica shell and then dispersed by ultrasonication into molten aluminum. Using X-ray diffraction, electron microscopy, and X-ray photoelectron spectroscopy, we probe the evolution of the bismuth particles and of the inorganic shell. We demonstrate that the silica shell acts as a barrier against extensive coalescence of particles during the dispersion process, thus enabling a decrease and a widening of the phase change temperature range.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.