We describe a group of alloys that exhibit "super" properties, such as ultralow elastic modulus, ultrahigh strength, super elasticity, and super plasticity, at room temperature and that show Elinvar and Invar behavior. These "super" properties are attributable to a dislocation-free plastic deformation mechanism. In cold-worked alloys, this mechanism forms elastic strain fields of hierarchical structure that range in size from the nanometer scale to several tens of micrometers. The resultant elastic strain energy leads to a number of enhanced material properties.Mechanical properties, such as strength, of metallic materials are strongly affected by metallurgical processes such as heat treatment and plastic working, which bring modifications in the microstructure. On the other hand, these processes have no substantial effect on physical properties such as elastic modulus and thermal expansion. The reason for this is that the changes that can be affected by plastic working and heat treatment do not extend to interatomic bonds or electronic states.We present a group of alloys that exhibit multiple "super" properties and drastic changes in physical properties after plastic working at room temperature. These alloys simultaneously offer super elasticity, super strength, super coldworkability, and Invar and Elinvar properties. The alloys consist of Group IVa and Va elements and oxygen and share the following three electronic magic numbers: (i) a compositional average valence electron number [electron/atom (e/a) ratio] of about 4.24; (ii) a bond order (Bo value) of about 2.87 based on the DV-X␣ cluster method, which represents the bonding strength (1-3); and (iii) a "d" electron-orbital energy level (Md value) of about 2.45 eV, representing electronegativity. The properties emerge only when all three of these magic numbers are satisfied simultaneously. Various alloy composition combinations meet these criteria, such as Ti-12Ta-9Nb-3V-6Zr-O and Ti23Nb-0.7Ta-2Zr-O [mole percent (mol %)], wherein each alloy has a simple body-centered cubic (bcc) crystal structure. In order to exhibit these properties, each alloy system requires substantial cold working and the presence of a certain amount of oxygen, restricted to an oxygen concentration of 0.7 to 3.0 mol %.Typical properties of the alloys are shown in Fig. 1 for samples before and after cold swaging with 90% reduction in area (4). Tensile stress-strain curves shown in Fig. 1A indicate that cold working substantially decreases the elastic modulus and increases the yield strength and confirm nonlinearity in the elastic range, with the gradient of each curve decreasing continuously to about 1/3 its original value near the elastic limit. As a result of this decrease in elastic modulus and nonlinearity, elastic deformability after cold working reaches 2.5%, which is at least double the value before cold working. Generally, large elastic deformations that occur in so-called "super-elastic alloys" are known to be reversible martensitic transformations resulting from deformation, d...

Direct observation of light elements (Li and O) in oxygen‐deficient lithium manganese spinel by spherical aberration‐corrected scanning transmission electron microscopy is reported. A previously unknown ordered structure was revealed by annular dark‐field (ADF) imaging of oxygen columns, while Li ions are visualized successfully by annular bright‐field (ABF) imaging (see picture).

Lanthanum lithium titanate (LLTO) is one of the most promising electrolyte materials for all-solid-state lithium-ion batteries. Despite numerous studies, the detailed crystal structure is still open to conjecture because of the difficulty of identifying precisely the positions of Li atoms and the distribution of intrinsic cation vacancies. Here we use subangstrom resolution scanning transmission electron microscopy (STEM) imaging methods and spatially resolved electron energy loss spectroscopy (EELS) analysis to examine the local atomic structure of LLTO. Direct annular bright-field (ABF) observations show Li locations on O4 window positions in Li-poor phase La0.62Li0.16TiO3 and near to A-site positions in Li-rich phase La0.56Li0.33TiO3. Local clustering of A-site vacancies results in aggregation of Li atoms, enhanced octahedral tilting and distortion, formation of O vacancies, and partial Ti4+ reduction. The results suggest local LLTO structures depend on a balance between the distribution of A-site vacancies and the need to maintain interlayer charge neutrality. The associated local clustering of A-site vacancies and aggregation of Li atoms is expected to affect the Li-ion migration pathways, which change from two-dimensional in Li-poor LLTO to three-dimensional in Li-rich LLTO. This study demonstrates how a combination of advanced STEM and EELS analysis can provide critical insights into the atomic structure and crystal chemistry of solid ionic conductors.

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Atomic-resolution STEM and EELS analysis provide insights into microscopic mechanisms behind oxygen loss and capacity fade in spinel-structured lithium-ion battery cathode material LiMn2O4.

Nickel (Ni) nanoparticle-dispersed amorphous silica (Si-O) powders were synthesized from chemical solution precursors. The high-temperature hydrogen adsorption property of the precursor-derived composite powders was investigated in comparison with the amorphous Si-O and Ni at 773 K. Among the three powder samples, Ni nanoparticle-dispersed amorphous Si-O exhibited a unique reversible hydrogen adsorption property that was hardly detected on the amorphous Si-O and Ni. The increase amount of the reversibly adsorbed hydrogen was the highest for the composite samples at around the Ni content with a Ni/(Si1Ni) ratio of 0.2-0.3. The results strongly suggested that when the composite material is used in the form of a gas separation membrane, the reversibly adsorbed hydrogen property is thought to contribute to the additional increase in the number of solubility sites for hydrogen, which leads to a selective enhancement in the high-temperature hydrogen permeance at 773 K.

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