Looming concerns regarding scarcity, high prices, and safety threaten the long-term use of lithium in energy storage devices. Calcium has been explored in batteries because of its abundance and low cost, but the larger size and higher charge density of calcium ions relative to lithium impairs diffusion kinetics and cyclic stability. In this work, an aqueous calcium–ion battery is demonstrated using orthorhombic, trigonal, and tetragonal polymorphs of molybdenum vanadium oxide (MoVO) as a host for calcium ions. Orthorhombic and trigonal MoVOs outperform the tetragonal structure because large hexagonal and heptagonal tunnels are ubiquitous in such crystals, providing facile pathways for calcium–ion diffusion. For trigonal MoVO, a specific capacity of ∼203 mAh g ⁻¹ was obtained at 0.2C and at a 100 times faster rate of 20C, an ∼60 mAh g ⁻¹ capacity was achieved. The open-tunnel trigonal and orthorhombic polymorphs also promoted cyclic stability and reversibility. A review of the literature indicates that MoVO provides one of the best performances reported to date for the storage of calcium ions.

Piezoelectric materials show potential to harvest the ubiquitous, abundant, and renewable energy associated with mechanical vibrations. However, the best performing piezoelectric materials typically contain lead which is a carcinogen. Such lead-containing materials are hazardous and are being increasingly curtailed by environmental regulations. In this study, we report that the lead-free chalcogenide perovskite family of materials exhibits piezoelectricity. First-principles calculations indicate that even though these materials are centrosymmetric, they are readily polarizable when deformed. The reason for this is shown to be a loosely packed unit cell, containing a significant volume of vacant space. This allows for an extended displacement of the ions, enabling symmetry reduction, and resulting in an enhanced displacement-mediated dipole moment. Piezoresponse force microscopy performed on BaZrS₃ confirmed that the material is piezoelectric. Composites of BaZrS₃ particles dispersed in polycaprolactone were developed to harvest energy from human body motion for the purposes of powering electrochemical and electronic devices.

In this study, structural and mechanical properties of re-pressed and annealed iron (Fe)-alumina (Al₂O₃) metal matrix nanocomposites (MMNCs) was investigated. Composite composition with 5 wt.% of alumina to iron was fabricated using ball milling technique. Cylindrical sintered specimens were pressed at a load of 10, 12.5, and 15 kN in a die of similar diameter so as to have maximum deformation internally at grain as well as at grain boundary. These specimens were heat treated at 900, 1000, and 1100℃ for 1 h to anneal the stresses as well as to enhance the bonding between grains. Synthesized specimens were characterized for their microstructure, density and hardness respectively. Scanning electron microscopic images of the synthesized specimens revealed the formation of dense phase microstructure along with the presence of nano-dispersion of iron aluminate (FeAl₂O₄) phase. Secondary processing of metal matrix nanocomposites resulted in an increase in density of prepared specimens from 4.6960 to 5.5035 g/cm³ and the hardness values increased from 63 to 94 HRH.