Matusi–Akaogi force field is used in molecular dynamics simulations to generate three samples of amorphous TiO2 of 3-nm size under different heating and quenching rates. The averaged pair correlation functions, coordination numbers, bond lengths, bond angles, and dihedral angles are calculated at 315 K. It is found that overcoordinated Ti and O atoms are in the core region, 6- and 3-fold coordinated Ti and O atoms are in the central part, and undercoordinated Ti and O atoms are in the vicinity of the surface. The correlations are significant up to 10 Å and vanish at the particle size. The calculated averaged bond lengths for short-range interparticle correlations agree with the experimental data. The discrete bond angles and dihedral angles of crystalline sphere get distributed over complete range in the amorphous phase and closer strained atomic network is predicted. The relative variance in the atomic arrangements in three samples is within 4%.

The size dependence of the lattice parameter of nanosolids has extensively been studied because lattice strain engineering is important in controlling the physical properties of nanowires (NWs), such as band gap, carrier transport, mechanical strength, etc. We have investigated the size-dependent lattice behavior of microstructure-controlled Sn NWs with radii of 7–35 nm. The NW microstructures were controlled as single-crystal, granular, and bamboo structures in the longitudinal direction. Results showed that the a-axis lattice parameter in the [100]-longitudinal direction of NWs can be controlled within 1% by varying the wire microstructure for the same wire radius because it is strongly dependent on the microstructure and the wire radius. Moreover, as the randomness of the grain orientation in the microstructure-controlled NWs increases, by which the anisotropy of surface stress is effectively reduced, the lattice strain of the NW can be compressive or tensile as a function of the wire radius. The longitudinal lattice parameters of microstructure-controlled Sn NWs can be tailored by reducing the effective anisotropy of surface stresses under a dimension confinement in the nanometer scale.

A promising n-type thermoelectric oxide, based on the tungsten bronze-structured ferroelectric SrxBa1–xNb2O6–δ (SBN, x~0.61), was investigated to enhance the thermoelectric power factor through templated grain growth (textured polycrystalline). In the reduced SBN textured, both the electrical conductivity (σ) and the magnitude of thermopower (S) are increased in the c axis: σ33 > σ11 and |S33| > |S11|, and consequently, the thermoelectric power factor (PF) increased significantly due to crystal anisotropy and grain boundary density reduction. It was found in randomly oriented polycrystalline ceramics that the thermoelectric properties are dominated by a-axis properties. A ferroelectric–thermoelectric anomaly is observed at 4mm–4/mmm phase transition temperature (TC) and depends on temperature and reduction degree, consistent with our earlier observations in single crystal SBN. Above TC, the carrier transport mechanism is controlled by polaron hopping conduction, and below TC the behavior depends on the degree of reduction. However, the magnitude of the Seebeck coefficient is dependent on the crystal anisotropy.

Nickel oxide–polypyrrole (NiO–PPy) composites for lithium-ion batteries were prepared by a chemical polymerization method with sodium p-toluenesulfonate as the dopant, Triton-X as the surfactant, and FeCl3 as the oxidant. The new composite material was characterized by Raman spectroscopy, thermogravimetric analysis, scanning electron microscopy, and field-emission scanning electron microscopy. Nanosize conducting PPy particles with a cauliflower-like morphology were uniformly coated onto the surface of the NiO powder. The electrochemical results were improved for the NiO–PPy composite compared with the pristine NiO. After 30 cycles, the capacities of the NiO and the NiO–PPy composite were about 119 and 436 mAh·g−1, respectively, indicating that the electrochemical performance of the composite was significantly improved.

Thermophysical properties such as phase-transformation temperatures and enthalpy of solidification depend on the composition and on the solidification conditions. To analyze the effects of the cooling rate on these properties, three commercial magnesium alloys (AZ91D, AM60B, and AE44) have been studied. Phase-transformation temperatures and enthalpy of solidification of these alloys have been measured using differential scanning calorimetry. Solidification curves have been obtained experimentally and compared with thermodynamic calculations. For all the studied alloys, it has been found that with increasing cooling rate, liquidus temperature increases slightly, whereas solidus temperature decreases. Enthalpy of solidification increases significantly with increasing cooling rate. Finally, relationships of phase-transformation temperature and enthalpy of solidification as a function of cooling rate have been established on the basis of the general power law. Using these relationships, the phase-transformation temperature and enthalpy of solidification have been predicted at high cooling rates and compared with experimental results.

Ternary electroless nickel, NiXP, films were produced by adding salts of Mo, Re, Tl, Cu, W, Co, Fe, Zn, and Mn to conventional electroless Ni baths and subsequently reacted with Sn-3.5Ag solder. From the full width at the half maximum (FWHM) data, as-plated NiXP films can be categorized into two groups: one is close to the FWHM value of nanocrystalline Ni5P film and the other is close to amorphous Ni9P film. Alloying elements in the electrolessly plated under-bump metallurgy that effectively suppressed intermetallic compound (IMC) spalling were Mn, Zn, Re, Fe, and W, whereas Tl exacerbated spalling. The roles of Cu, Mo, and Co were less clear due to a lack of data. Based on scanning electron microscopy observations, a spalling map was presented, which showed elemental demarcation lines of IMC spalling in the X-P coordinates.

Using a recently developed multidimensional nanocontact system designed for a quantitative measurement of lateral contact stiffness in the 10–106 N/m stiffness range (or 10–1000 nm contact size), we found a crystallographic-orientation-dependent lateral-stiffness reduction relative to the elastic prediction at contact sizes around 50 nm for polished Ni single crystal surface in air. The slidingless measurement is enabled by a frequency-specific, continuous stiffness measurement technique. Based on an interface microslip model and an anisotropic elastic contact analysis, the resulting friction stress is found to increase monotonically when the tested lateral direction rotates away from the closely packed direction.

Semiconductor nanowires (NWs) are characterized by an extraordinarily large surface-to-volume ratio. Consequently, surface effects are expected to play a much larger role than in thin films. Here, we review a research focused on the impact of the surface on the electrical and optical properties of catalyst-free GaN NWs with growth direction <0001>. Using a combination of complementary experimental techniques, it has been shown that the Fermi level is pinned at the NW sidewall surfaces, resulting in internal electric fields and in full depletion for NWs below a critical diameter. Deoxidation of the surfaces unpins the Fermi level, leading to enhanced radiative recombination of excitons. Prominent absorption below the bandgap is caused by the Franz-Keldysh effect. Close to the surface, the ionization energy of donors is reduced. The consideration of surface-induced effects is mandatory for an understanding of the physical properties of NWs as well as their application in devices.

The properties of widely used Ni–Ti-based shape memory alloys (SMAs) are highly sensitive to the underlying microstructure. Hence, controlling the evolution of microstructure during high-temperature deformation becomes important. In this article, the “processing maps” approach is utilized to identify the combination of temperature and strain rate for thermomechanical processing of a Ni42Ti50Cu8 SMA. Uniaxial compression experiments were conducted in the temperature range of 800–1050 °C and at strain rate range of 10−3 and 102 s−1. Two-dimensional power dissipation efficiency and instability maps have been generated and various deformation mechanisms, which operate in different temperature and strain rate regimes, were identified with the aid of the maps and complementary microstructural analysis of the deformed specimens. Results show that the safe window for industrial processing of this alloy is in the range of 800–850 °C and at 0.1 s−1, which leads to grain refinement and strain-free grains. Regions of the instability were identified, which result in strained microstructure, which in turn can affect the performance of the SMA.

Breakdown of porous materials by salts occurs when growing crystals exert pressure on the pore walls, inducing stress in the material that exceeds its tensile strength. In this work, we quantify the mechanical stresses caused by a particularly destructive mechanism: the dissolution of an anhydrate (thenardite, Na2SO4) followed by precipitation of a hydrated salt (mirabilite, Na2SO4·10H2O). Stresses are measured using a composite specimen consisting of a plate of glass bonded to a plate of limestone (CaCO3) whose pores are impregnated with thenardite. As water wicks into the limestone, thenardite dissolves and mirabilite precipitates. The limestone expands from the pressure exerted by the salt resulting in deflection of the composite, and the stresses can be obtained from an elastic analysis. Synchrotron x-ray diffraction reveals the dissolution–crystallization rate. Numerical modeling shows that the stresses are affected by the kinetics of crystallization and dissolution, permeability, and mechanical properties of the stone, allowing us to determine the amount of salt that causes material fracture.

The effect of the magnetic anisotropy and the dipolar interactions between NiFe magnetic layers and between nanowires on the magnetic properties of NiFe/Cu multilayered nanowire arrays electrodeposited into the nanopores of anodic aluminium oxide (AAO) templates with diameters of 35 and 200 nm has been studied. The variation of the aspect ratio (thickness/diameter) between the NiFe magnetic and Cu nonmagnetic layers influences the effective anisotropy field. The correlation between the measured hysteresis loops, with the applied field parallel and perpendicular to the multilayered nanowires’ axis, and the calculated effective anisotropy field, Heff, and saturation field, Hsat, shows that it is possible to tune the orientation of the magnetization axis with high accuracy. Two formulas, which include both the intra- and internanowire interactions, were proposed to calculate the saturation fields of multilayered nanowire arrays for the applied field parallel and perpendicular to the nanowires’ axis.

Nacre from mollusk shell is a high-performance natural composite composed of microscopic mineral tablets bonded by a tough biopolymer. Under tensile stress, the tablets slide on one another in a highly controlled fashion, which makes nacre 3000 times tougher than the mineral it is made of. Significant efforts have led to nacre-like materials, but none can yet match this amount of toughness amplification. This article presents the first synthetic material that successfully duplicates the mechanism of tablet sliding observed in nacre. Made of millimeter-size wavy poly-methyl-methacrylate tablets held by fasteners, this “model material” undergoes massive tablet sliding under tensile loading, accompanied by strain hardening. Analytical and finite element models successfully captured the salient deformation mechanisms in this material, enabling further design refinements and optimization. In addition, two new mechanisms were identified: the effect of free surfaces and “unzipping.” Both mechanisms may be relevant to natural materials such as nacre or bone.

Elastic modulus and internal friction of Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) and La0.58Sr0.4Co0.2Fe0.8O3-δ (LSCF) were determined from resonance frequencies and damping behavior, respectively, using an impulse excitation method. An elastic anomaly for BSCF around 476 K, with a corresponding peak in the internal friction, is attributed to the experimentally confirmed spin transition of Co3+. LSCF is in a ferromagnetic state below ∼220 K and in a paramagnetic state above ∼250 K. The elastic modulus of LSCF exhibits an anomaly between 473 and 1113 K, which is attributed to a transition from rhombohedral to cubic symmetry.

An ecofriendly process has been successfully developed to synthesize the polycrystalline silver nanopolyhedrons with a high yield at large scale. By using tannic acid in the presence of poly (vinyl pyrrolidone) (PVP), high quality silver nanopolyhedrons were obtained in an aqueous one-pot reaction without any templates or auxiliaries. The film made from the silver nanostructures exhibits an electrical conductivity higher than 104 S/cm on both rigid and flexible substrates. The supreme mechanical strength of this silver film recommends its wide application in printing and flexible electronics.

Nd3+/Yb3+ co-doped TiO2–La2O3 glasses modified by ZrO2 were fabricated by containerless method. Under the excitation of 980 nm lasers, three intense emissions centered at 521, 545, and 655 nm were observed, which are assigned to the Nd3+: 4G9/2→4I9/2, 4G7/2→4I9/2, and 4G7/2→4I13/2 transitions, respectively. Besides, two very weak emission bands at 496 and 603 nm were also found due to the Nd3+ transition of 2G9/2→4I9/2 and 4G5/2 (or 2G7/2)→4I9/2, respectively. Pumping powder dependence of emission intensity suggests a two-photon adsorption process responsible for the upconversion luminescence. A combined phonon-assisted and cooperative sensitization mechanism is presented to interpret the energy transfer from Yb3+ to Nd3+ ions. In addition, the highest intensity of luminescence was found for the glass with 1.2 mol% Nd3+, and the upconversion efficiency can be enhanced by increasing of ZrO2 content.

Most state-of-the-art thermoelectric (TE) materials contain heavy elements Bi, Pb, Sb, or Te and exhibit maximum figure of merit, ZT∼1–2. On the other hand, oxides were believed to make poor TEs because of the low carrier mobility and high lattice thermal conductivity. That is why the discoveries of good p-type TE properties in layered cobaltites NaxCoO2, Ca4Co3O9, and Bi2Sr2Co2O9, and promising n-type TE properties in CaMnO3- and SrTiO3-based perovskites and doped ZnO, broke new ground in thermoelectrics study. The past two decades have witnessed more than an order of magnitude enhancement in ZT of oxides. In this article, we briefly review the challenges, progress, and outlook of oxide TE materials in their different forms (bulk, epitaxial film, superlattice, and nanocomposites), with a greater focus on the nanostructuring approach and the late development of the oxide-based TE module.

A 〈110〉 oriented Tb0.3Dy0.7Fe1.95 alloy rod was annealed at 500 °C under a magnetic field of 0.3 T, which was applied 35° away from the rod axis. X-ray diffraction characterization and optical microscopy observation showed that both the crystal orientation and morphologies were retained after magnetic annealing. Magnetic force microscopy images exhibited obvious change of the magnetic domain configurations. The magnetostrictive performance was changed drastically. Saturation axial magnetostriction λ‖s increased from 1023 to 1650 ppm by the ratio of 61.3%, but saturation perpendicular magnetostriction λ⊥s decreased from −802 to −624 ppm. Maximum magnetostrictive strain coefficients d33 and d31 were found to be enhanced by 29.3% and 32.6%, respectively. In addition, the fields for obtaining both optimum d33 and d31 decreased, which indicates that better magnetostrictive performance can be achieved at lower external fields after magnetic annealing.

Reliable and cost-effective techniques to process surface nanoscale metallic structures with controllable and complex nanomorphologies is important toward progress in technologies related to sensing, energy harvesting, information storage, and computing. Here we discuss how pulsed laser melting and the ensuing self-organization by dewetting of ultrathin films can be utilized to fabricate various nanomorphologies in a predictable manner. Ultrathin metal films (1–100 nm) on inert substrates like SiO2 are generally unstable, with their free energy resembling that of a spinodal system. The energy rate theory of self-organization, which is based on balancing the rate of thermodynamic free energy change to the rate of energy dissipation, predicts the appearance of characteristic length scales. This is borne out in experiments of nanosecond pulsed laser melting of a variety of metal films. We review this laser-based self-organization technique with various examples from the behavior of Ag and Co metals on SiO2 substrates. Specifically, film thickness and film roughness can be used to control dewetting length scales, whereas knowledge of the intermolecular forces responsible for the free energy of the system control the type of morphology. Furthermore, novel dewetting is observed that is attributable to nanoscale heating effects resulting from the thickness-dependent pulsed laser heating. These results help elucidate the basic mechanisms of pulsed laser induced dewetting of metal films, but they also provide potential routes for cost-effective nanomanufacturing of metallic surfaces for applications in sensing, energy harvesting, and information processing.

The influence of Co content on stacking fault energy (SFE) of the γ matrix in four Ni–Co base superalloys, including newly developed alloys, has been studied by utilizing high-resolution transmission electron microscopy. The results indicated the SFE was not linear with Co content of the γ matrix. The lowest SFE could be attained at around 34.0 at.% Co. This effect was attributed to variation of electron holes, saturated Co content in the matrix, and the effect of Co on the partition coefficient of other alloying elements. A high density of twins was related to low SFE and could improve the mechanical properties.

A procedure for predicting the in-plane and out-of-plane thermal conductivities of woven fabric composites through a combined approach of the representative volume element method and heat transfer analyses via finite element is presented. The representative volume element method was implemented using two unit cells established at different length scales with periodic boundary conditions. The procedure was exemplified on a plain weave glass fabric reinforced epoxy resin matrix composite. Sensitivity studies were conducted to quantify the influence of fiber volume fraction and thermal conductivity of the constituent phases on the effective thermal conductivities of the composite. The procedure, which can be implemented into commercial finite element codes, is an efficient tool for the design of woven fabric composites.