The formation of a metastable Cu–Ta solid solution in a mechanically alloyed Cu–10 at.%Ta alloy and its subsequent decomposition during annealing was investigated by atom probe tomography. During annealing, the as-milled Cu-rich alloy undergoes phase separation; Ta atoms diffuse out of the Cu lattice to form Ta clusters and particles along grain boundaries and within the Cu grains. The role of the Ta clusters and the nature of the solid solution as a potential strengthening mechanism for these alloys are discussed.

The (3 + 1)-dimensional crystal structure of the Nowotny chimney–ladder compound Rh17Ge22 was revealed using powder x-ray diffraction technique. As in the case of the higher manganese silicide MnSiγ (known as Mn11Si19, etc.), this germanide consists of two tetragonal subsystems of [Rh] and [Ge] with an irrational c-axis ratio γ = cRh/cGe, and hence the structural formula can be represented as RhGeγ. As expected from first-principles calculations of the approximate structure and the valence electron count, n-type (negative Seebeck coefficient) conduction was experimentally confirmed over the whole temperature range of 333–984 K. Although the absolute value of the Seebeck coefficient was limited to |S| ≤ 53 μV/K, a high electrical conductivity (σ = 4.8 × 103 S/cm) yielded a reasonable power factor of S2σ ∼ 1 mW/K2 m above 600 K. A maximum dimensionless figure-of-merit of ∼0.1 at 900 K was expected using thermal conductivity data of a sintered pellet.

We report on the ability to switch an optical material composed of a polymer stabilized cholesteric liquid crystal (polymer stabilized cholesteric texture, PSCT) between stable transparent (reflective) and scattering modes. The degree of scattering is controllable with the strength of the applied electric field. The mechanism for bistable switching of the PSCT is distinguished from prior examinations by employing electromechanical displacement of a stabilizing polymer network. The stable transparent (reflective) or scattering modes are induced with a variety of driving schemes employing both alternating and direct current fields. The relative degree of scattering can be varied to allow for grayscale control potentially useful in smart window and display applications.

To investigate the effect of Y element and hot-extrusion on microstructure and mechanical properties of the three alloys which are Mg–4Zn–xY (x = 1, 2, 3 in wt%). All the three alloys are hot-extruded and analyzed. The results show that as Y is increased, the microstructures of the as-cast alloys are more refined and the phase compositions are changed from both I-phase and W-phase to single W-phase whose structure is changed from mix of net and spheroidization to continuous net. The mechanical properties are increased to a small extent mainly due to the refining effect of Y. After hot-extrusion, coarse dendrite crystals are broken and dynamic recrystallization appears which obviously refine the microstructure. Second phases are redistributed along the extrusion direction. W-phases are twisted and broken, while I-phases are spheroidized. Tensile strengths and elongations are all increased by around 100% compared with the as-cast alloys.

This article addresses recent advances in the application of microscopy techniques to characterize crystallization processes as they relate to biomineralization and bioinspired materials synthesis. In particular, we focus on studies aimed at revealing the role organic macromolecules and functionalized surfaces play in modulating the mechanisms of nucleation and growth. In nucleation studies, we explore the use of methods such as in situ transmission electron microscopy, atomic force microscopy, and cryogenic electron microscopy to delineate formation pathways, phase stabilization, and the competing effects of free energy and kinetic barriers. In growth studies, we emphasize understanding the interactions of macromolecular constituents with growing crystals and characterization of the internal structures of the resulting composite crystals using techniques such as electron tomography, atom probe tomography, and vibrational spectromicroscopy. Examples are drawn from both biological and bioinspired synthetic systems.

We report the use of electrospray to continuously deposit thin films, including patterned films, of a block copolymer (BCP). High substrate temperatures led to vertically oriented cylindrical microdomains at the film surface independent of the solvent composition and deposition rates utilized. Conversely, low substrate temperatures resulted in morphologies that were more sensitive to these parameters, with poorly ordered films of globular structures observed at the lowest temperatures considered. The deposition pattern is defined by spatially varying the electric field at the substrate using an underlying charged grid. These results open up new possibilities for patterned deposition of BCP films with morphological control.

It has been about a hundred years since the atomic nature of matter began to be generally accepted. By the late 1920s, atomic theory was well established, and quantum theory had explained many properties of atoms in gases. The interpretation of the sharp lines in atomic optical spectra could be explained in terms of transitions between electronic energy levels. The application of interacting atoms in solids appeared straightforward in principle, and although quantum theory answered many fundamental questions about condensed matter, theoretical applications were mostly appropriate for idealized models of solids. Because the optical spectra of solids had broad structure, explaining their origin in terms of electronic transitions was more difficult than for the case of atoms. It was not until the 1960s that accurate electronic band structures could be calculated for bulk materials. Basic and applied research involving semiconductors, superconductors, and nanostructured materials has guided the application of quantum theory to condensed matter. These are areas where the use of quantum theory has been central in explaining and predicting properties and has even led to the discovery of new materials.

The present study was conducted to predict the hot deformation behavior of the as-forged Nitinol 60 shape memory alloy by using the Arrhenius type, multiple-linear, and artificial neural network (ANN) models. The acquired flow stress data from isothermal hot compression tests in a temperature range of 650–850 °C under strain rate range of 0.01–1 s−1 were used to calculate the material constants for establishing the corresponding constitutive equations. Furthermore, a comparative study has been made on the capability of the aforementioned models to predict the high-temperature deformation behavior by comparing the prediction relative errors, average absolute relative error, and correlation coefficient. The results show that multiple-linear model predicts the flow behavior more accurately than the Arrhenius type model. The ANN model is much more efficient and has a better prediction power for the as-forged Nitinol 60 alloy than both the Arrhenius type and multiple-linear models.

Recent efforts have demonstrated enhanced tailoring of material functionality with mixed anion materials, yet exploratory research with mixed anion chemistries is limited by the sensitivity of these materials to synthesis conditions. Synthesis of a particular metal oxynitride compound by traditional reactive annealing requires specific, limited ranges of both oxygen and nitrogen chemical potentials to establish equilibrium between the solid-state material and a reactive atmosphere. Using Ta–O–N as an example system, we describe a combination of reactive sputter deposition and rapid thermal processing (RTP) for synthesis of mixed anion inorganic materials. Heuristic optimization of reactive gas pressures to attain a desired anion stoichiometry is discussed, and the ability of RTP to enable amorphous to crystalline transitions without preferential anion loss is demonstrated through the controlled synthesis of nitride, oxide, and oxynitride phases.

A model of reactive hot pressing of zirconium carbide (ZrCx , 0.5 < x < 1) has been constructed that incorporates four processes that occur in parallel: creep of zirconium (Zr), reaction of Zr and carbon (C), increase in volume fraction of hard phase with progressive reaction that reduces the creep of Zr and, finally, de-densification associated with volume reduction during reaction. The reasonable agreement of the model with experimental results verifies that plastic deformation of Zr is the main factor that is responsible for the low-temperature reactive densification of ZrC and that ZrC may be treated as a rigid inclusion that contributes little to densification. It predicts that densification is impaired by increasing carbon stoichiometry due to the increasing amount of starting hard phase and the greater contraction upon reaction. Additionally, the model predicts that mixtures of Zr and ZrC should show equal or better densification than Zr and C mixtures.

In molecular dynamics simulations, the local stress state in the shear band is examined in six different model metallic glasses and one amorphous Si system (also has been perceived as a metallic glass analog) under different loading conditions. For all but the FeP and the amorphous Si systems, the running shear band (RSB) exhibits a liquid-like hydrostatic plus shear stress state. Our results suggest that the liquid feature of a RSB is not due to temperature rise or plastic confinement but due to the disorder driven by flow, which can be offset by strong directionality in bonding, phase segregation, or aging. The knowledge of the liquid-like stress state can be conveniently utilized in experiments to infer the local stress state of the RSB from the global tensile stress for metallic glasses.

This work focused on the modification of milled GaN powder. Successful attachment of a porphyrin derivative to a GaN powder was performed via in situ functionalization in the presence of phosphoric acid. The GaN powder was imaged using scanning electron microscopy and was found to be heterogeneous in nature, adopting no consistent geometry in the aggregates. The aqueous stability of the porphyrin used was observed in deionized water and a solution of phosphoric acid using ultraviolet–visible spectroscopy. Surface chemistry was characterized with x-ray photoelectron spectroscopy and infrared spectroscopy, which identified evidence of successful functionalization through the presence of characteristic peaks. The interface stability of the covalent bond between GaN and porphyrin was evaluated using fluorescence spectroscopy and demonstrated no leaching of dye in water solutions for 20 days.

The effects of heat treatment for recovering microstructure of a Ni-based single crystal superalloy with carbon addition have been evaluated. The heat treatment resulted in increased levels of chemical homogeneity. All the samples experienced more γ′ coarsening than as-cast samples. Significant changes to as-cast carbide morphologies were observed. Script-type, MC carbide networks transformed during heat treatment to smaller, spherical Ta-rich MC carbides. Heat treatment caused significant MC carbide decomposition and formation of Cr-rich secondary carbides on or near to decomposed carbides in all modifications. The size of carbides after heat treatment was less than that of cast alloy obviously, and the distribution of carbides became more and more dispersion than in cast alloy.