Type II ZnO/ZnSe core/shell nanowire arrays were grown by a two-step chemical vapor deposition. The nanowire arrays with dense nanoislands on the surface are well aligned and normal to the substrate imaged by scanning electron microscopy. The core/shell structure of nanowires was identified by a high-resolution transmission electron microscopy. The structure and composition of the shell were confirmed to be wurtzite ZnSe by x-ray diffraction, Raman scattering and energy-dispersive x-ray spectroscopy. Moreover, an intense emission was observed at 1.89 eV smaller than the band gaps of core and shell materials by photoluminescence, indicating the achievement of the type II band alignment at the interface. This study is expected to contribute to the potential applications in novel photovoltaic devices.

The influence of temperature on the indentation size effect is explored experimentally. Copper is indented on a custom-built high-temperature nanoindenter at temperatures between ambient and 200 °C, in an inert atmosphere that precludes oxidation. Over this range of temperatures, the size effect is reduced considerably, suggesting that thermal activation plays a major role in determining the length scale for plasticity.

Wurtzite ZnO nanorods were grown from solution onto coarse-grain bulk polycrystalline Ag substrates to explore the nature of preferred heteroepitaxial orientations. ZnO nanorods grow copiously on grains with <111> and <001> surface normals. Two epitaxial orientations were observed: {0001} ZnO ‖ {111} Ag with <20> ZnO ‖ <10> Ag and {0001} ZnO ‖ {001} Ag with <20> ZnO ‖ <10> Ag. Both feature ZnO basal plane growth, and the specific in-plane orientation relationships both feature alignment of close-packed directions in the interface. Nanorod growth was strongly suppressed on Ag grains in most other orientations. Although strain energy minimization is often invoked to explain the {0001} ZnO ‖ {111} Ag with <20> ZnO ‖ <10> Ag orientation, associated with an almost ideal near-coincidence site lattice matching, our data suggests that strain may not be the sole, or even the most important, determinant of the preferred orientations during solution-based epitaxial growth in this system.

The dynamic uniaxial compressive behavior of Zr-based metallic glasses under a wide high strain rate was studied by a miniaturized split Hopkinson pressure bar, including high strain rate up to 104 s−1. Experimental results indicate that the uniaxial compressive failure stress would decrease suddenly and then tend to hold steady with increasing strain rate. This phenomenon provides a generalized perspective for understanding the effect of local heat generation on the deformation of metallic glasses under dynamic loads.

Recent advances in pulsed x-ray sources have opened up new opportunities to study the dynamics of matter directly in the time domain with picosecond to femtosecond resolution. In this article, we present recent results from a variety of ultrafast sources on time-resolved x-ray scattering from elementary excitations in periodic solids. A few representative examples are given on folded acoustic phonons, coherent optical phonons, squeezed phonons, and polaritons excited by femtosecond lasers. Next-generation light sources, such as the x-ray-free electron laser, will lead to improvements in coherence, flux, and pulse duration. These experiments demonstrate potential opportunities for studying matter far from equilibrium on the fastest time scales and shortest distances that will be available in the coming years.

Electroless nickel (Ni–P) is a common surface finish used in the ball grid array (BGA) package and interfacial reactions between its surface finish and lead-free solders can form complex intermetallic compound (IMC) layers. The presence of minor elements in lead-free solders either intentionally added or due to impurity contamination during solder manufacturing, can affect the solder-joint performance. In this work, interfacial reactions between Ni–P surface finish and the Sn–Ag–Cu solders were modified by varying Ag and Cu contents and also by adding a small amount of minor elements such as phosphorus (P), indium (In), and germanium (Ge). A transmission electron microscope was used to determine the intermetallic layer phases, compositions, crystal structures, and void defects. Varying the solder alloy elements led to the modulation of voids formation.

Compressive stress–strain behaviors in a 〈110〉-oriented crystal Tb0.3Dy0.7Fe1.95 after magnetic annealing have been investigated under a series of quasi-static magnetic fields, attempting to add more insight into the corresponding domain-switching process. The magnetically annealed crystal outputs larger final strains than the untreated one, although it exhibits similar stress–strain behaviors. An obvious improvement also occurs in the initial Young's modulus E0 after magnetic annealing. The corresponding domain switching processes under compressive stress have been discussed. Non-180° domain processes are favored because of the specific initial domain states, which can be reflected by the shortening of the flat stage in magnetostriction–magnetic induction (λ–B) curve and the increase of the critical field where maximum forced magnetostriction constant d33 locates.

Particle-containing silica sol was synthesized by co-hydrolysis and co-condensation of two silane precursors, tetraethylorthosilicate (TEOS) and an organic silane composed of a non-hydrolyzable functional group (e.g., alkyl, fluorinated alkyl, and phenyl), and used to produce superhydrophobic coatings on fabrics. It has been revealed that the non-hydrolyzable functional groups in the organic silanes have a considerable influence on the fabric surface wettability. When the functional group was long chain alkyl (C16), phenyl, or fluorinated alkyl (C8), the treated surfaces were highly superhydrophobic with a water contact angle (CA) greater than 170°, and the CA value was little affected by the fabric type. The washing durability of the superhydrophobic coating was improved by introducing the third silane containing epoxide group, 3-glycidoxypropyltrimethoxysilane (GPTMS), for synthesis. Although the presence of epoxide groups in the coating slightly reduced the fabrics' superhydrophobicity, the washing durability was considerably improved when polyester and cotton fabrics were used as substrates.

The dynamics of track development due to the passage of relativistic heavy ions through solids is a long-standing issue relevant to nuclear materials, age dating of minerals, space exploration, and nanoscale fabrication of novel devices. We have integrated experimental and simulation approaches to investigate nanoscale phase transitions under the extreme conditions created within single tracks of relativistic ions in Gd2O3(TiO2)x and Gd2Zr2–xTixO7. Track size and internal structure depend on energy density deposition, irradiation temperature, and material composition. Based on the inelastic thermal spike model, molecular dynamics simulations follow the time evolution of individual tracks and reveal the phase transition pathways to the concentric track structures observed experimentally. Individual ion tracks have nanoscale core-shell structures that provide a unique record of the phase transition pathways under extreme conditions.

X-ray and neutron diffraction have been two key techniques for structural characterization of materials since their inception. If single crystals of the materials of interest cannot be synthesized, one has to resort to powder diffraction. This results in the loss of three-dimensional orientation information of the crystal, and one has to contend with the one-dimensional information that is inherent to powder diffraction, making it harder to analyze the data. The structural study of contemporary materials and their remarkable properties is a challenging problem, particularly when properties of interest result from interplay of multiple degrees of freedom. Very often these are associated with structural defects or relate to different length scales in a material. The signature of the defect-related phenomenon is visible as diffuse scattering in the diffraction pattern, and the signals associated with diffuse scattering are orders of magnitude smaller than Bragg scattering. Given these limitations, it is crucial to have high-resolution and high-intensity data along with the ability to carry out theoretical interpretation that goes beyond periodic lattice formalism of crystallography. Great advances have been achieved due to the advent of synchrotron and neutron sources, along with the availability of high-speed computational algorithms allowing materials scientists to work with a very small amount of sample (both single crystal and powder) and analyze vast amounts of data to unravel detailed structural descriptions that were not previously possible. This article presents some of these great advances in using scattering probes for materials characterization.

A new low sintering temperature microwave dielectric ceramic, Li2ZnTi3O8, was investigated. X-ray diffraction data show that Li2ZnTi3O8 has a cubic structure [P4332(212)] with lattice parameters a = 8.37506 Å, V = 587.44 Å3, and Z = 4 when the sintering temperature is 1050 °C. The Li2ZnTi3O8 ceramic exhibits good microwave dielectric properties with εr about 26.2, Q×f value about 62,000 GHz, and τf about −15 ppm/°C. The addition of BaCu(B2O5) can effectively lower the sintering temperature from 1050 to 900 °C without degrading the microwave dielectric properties. Compatibility with Ag electrode indicates this material can be applied to low temperature cofired ceramic devices.

The microstructure and microimpact performance of Sn1Ag0.1Cu0.02Ni0.05In (SAC101NiIn)/AuNi/Cu solder ball joints were investigated after a thermal cycle test (TCT). The joints show complete bulk fracture behavior before TCT. Moreover, TCT facilitated interfacial fracture behavior with lower fracture energy. The intermetallic compounds (IMCs) formed in the solder joints before and after TCT were investigated. TCT induces a variety of structural variations in the solder joints, including slipping bands, whisker formation, the squeezing of the IMC layer, the formation of cavities, the rotation and pop-up of grain, and the deformation and rotation of the entire joint. The variations in fracture behavior induced by TCT are correlated with the structural variations in the solder joints.

Modified embedded-atom method (MEAM) interatomic potentials for Nb-C, Nb-N, Fe-Nb-C, and Fe-Nb-N systems have been developed based on the previously developed MEAM potentials for lower order systems. The potentials reproduce various fundamental physical properties (structural properties, elastic properties, thermal properties, and surface properties) of NbC and NbN, and interfacial energy between bcc Fe and NbC or NbN, in generally good agreement with higher-level calculations or experimental information. The applicability of the present potentials to atomic-level investigations to the precipitation behavior of complex-carbonitrides (Nb,Ti)(C,N) as well as NbC and NbN, and their effects on the mechanical properties of steels are also discussed.