Effect of a low-voltage pulsed magnetic field (LVPMF) on the solidified microstructure of Mg–Al–Zn alloy has been investigated. Experimental results show that the solidified structure of Mg–Al–Zn alloy can be remarkably refined and that the morphology of α-Mg is transformed from developed dendrite to fine rosette with the application of LVPMF. Magnetization of the solute and solvent in the diffusion layer cannot account for the formation of the rosette α-Mg under LVPMF. A model for the formation of rosette α-Mg under LVPMF has been developed by analyzing the growth behavior of α-Mg dendrite. Morphology change of α-Mg dendrite under LVPMF is caused by Joule heat concentrated on the dendrite tip. Accumulation of Joule heat on the dendrite tip melts the local dendrite tip and increases the radius of curvature. The increased radius of curvature at the dendrite tip lowers the growth rate and results in the formation of rosette α-Mg.

The time-resolved evolution of intermetallic phase formation in the system pure Sn (polycrystalline coating with a thickness of several microns) on pure Cu (polycrystalline bulk substrate) was investigated in detail by means of focused ion beam and transmission electron microscopy and x-ray diffraction during aging at room temperature for a period of about 1 year. The availability of this coherent data base allowed interpretation of the evolution of intermetallic compound (IMC) formation in terms of interface thermodynamics and interdiffusion kinetics. On this basis spontaneous Sn whiskering on the surface of the Sn coating as a consequence of intermetallic phase (Cu6Sn5) formation along, specifically, Sn grain boundaries intersecting the Sn/Cu interfaces could be discussed. Moreover, a treatment to mitigate spontaneous Sn whiskering on the basis of thermodynamic control of the IMC morphology was proposed.

The thermal conductivity of nacre from red abalone (Haliotis fulgens) has been determined as a function of temperature (2–300 K), direction, and treatment to partially demineralize or to remove a portion of the organic matrix. The room-temperature thermal conductivity and specific heat of nacre are ∼1 W m−1 K−1 and 0.9 J K−1 g−1, respectively. The thermal conductivity of nacre is rather low and glass-like. It is not as anisotropic as one might expect on the basis of brick-and-mortar structure, in support of recent findings that the aragonite tablets are not monolithic. Partial removal of the mineral component reduces the thermal conductivity in both principal directions, whereas partial removal of the proteins (as observed by 13C NMR) only reduces the thermal conductivity across the aragonite layers.

Tungsten nanoparticles (W-NPs) with average sizes ranging between 30 and 80 nm were prepared by thermolytic decomposition of tungsten hexacarbonyl in presence of a mixture of surfactants, oleic acid and oleyl amine. Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy (XPS) results reveal that the surfactants oleic acid and oleyl amine bonded to the surface of W-NP through their functional groups, which in turn render stability to the nanopowders with respect to coarsening or aggregation. XPS results also confirm that carbon is present only at the surface of the W-NPs. The as-synthesized W-NPs were amorphous, and on heat treatment at 600 °C for 1 h, the amorphous powders transform into a body-centered cubic crystalline form (α-W).

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.

Nonequilibrium phase composition in multiphase systems affects physical properties of many materials. Development of phase composition is controlled by external conditions and material characteristics. Based on the model presented in the Part I [A. Ziabicki and B. Misztal-Faraj, J. Mater. Res. 26(13), (2011)], rates of phase transitions in a three-phase model monotropic system composed of an amorphous (liquid) phase and two solid polymorphs have been analyzed. Effects of material characteristics including activation energy of molecular mobility, heat and entropy of the transitions, interface tensions, and concentration of predetermined nuclei have been discussed.

The three-dimensional structure of crack tip dislocations in single crystal silicon was observed by combining high-voltage electron microscopy and tomography. It was revealed that dislocations cross-slipped proximal to the crack tip even in the initial stages of plastic deformation. The local stress intensity factor along the crack front was calculated by taking into account the experimentally determined dislocation character. Based on these observations and calculations, a model to account for the sequential multiplication of dislocation sources along the crack front is proposed.

The exact solution of viscoelastic stresses in the bilayer system due to thermal and/or lattice mismatch is derived if both layers are Maxwell materials. When the thickness of one layer is much smaller than that of the other layer, the viscoelastic stresses in the bilayer system can be reduced to that of the thin film/substrate system. The relative film thickness and the position in the thin film/substrate systems are included in this solution. The average film stress decreases with increasing the normalized time and finally approaches zero in a long time. As the relative film thickness is equal to or less than 0.001, the average film stresses of the zeroth-order approximation, first-order approximation, and Hsueh and Lee model [J. Appl. Phys.91, 2760 (2002)] are close to that of exact solution. Nevertheless, as the relative film thickness is larger than 0.001, the accuracies of the zeroth-order approximation, first-order approximation, and Hsueh and Lee model are dependent on the normalized time and relative film thickness.

A multitarget sputtering method was applied to embed Au nanoparticles in TiO2 thin films (Au/TiO2 films) with a high concentration of Au particles (19–41 at%). The absolute values of imaginary part of the third-order nonlinear susceptibility, |Im [χ(3)]|, of the Au/TiO2 films, exhibited a peak around the localized surface plasmon resonance absorption peak (around 660 nm), and the maximum value was estimated to be 3.6 × 10−7 esu measured by the femtosecond Z-scan technique. The figure of merit, |Im [χ(3)]|/α, (α is the absorption coefficient of the film at the corresponding wavelength of the measurement) of the film was calculated to be 1.4 × 10−12 esu·cm, which was larger than that of the Au/SiO2 film. This is mainly due to the local field enhancement.

The kinetics of hydrogen in preparing amorphous boron carbide (a-B5C:H) thin films was studied. The hydrogen concentration of a-B5C:H thin films formed by plasma-enhanced chemical vapor deposition (PECVD) from a single-source precursor (o-B10C2H12) is ∼35–50 at.% as determined by nuclear reaction analysis. The hydrogen concentration of the a-B5C:H thin films is an exponential function of the precursor flux during the deposition. After annealing, the hydrogen concentration in the a-B5C:H thin films decreases with the increasing annealing temperature. The kinetics of hydrogen removal during annealing is controlled predominantly by its dissociation from PECVD radicals in the a-B5C:H thin films. The activation energy of about 0.14 eV is related to hydrogen dissociation from B–H bonds, but higher activation energy (∼0.44 eV) is required to strip the hydrogen atoms from C–H bonds in the thin films.

Single-crystalline p-type silicon nanowire (SiNW) arrays have been formed by electroless metal deposition on a silicon wafer piece in an ionic Ag/fluorhydric acid (HF) solution through selective etching. They display mechanical properties that are different from those of both bulk silicon and single SiNWs. As any practical application of these materials is likely to involve a large number of nanowires in close proximity to each other, it is necessary to understand the mechanical properties of SiNW arrays. In this work, as a first step to characterize their mechanical properties, the buckling instabilities of the surfaces formed by vertically aligned SiNWs have been studied by nanoindentation tests.

ZnO crystals have been investigated by scanning cathodoluminescence microscopy and spectroscopy at 80 K following hydrogen incorporation by plasma exposure. The intensity of the ZnO near-band-edge (NBE) emission is greatly enhanced while the defect-related green emission is quenched following plasma treatment. These effects are attributed to the passivation of zinc vacancies by hydrogen. The green and yellow intensities and their intensity ratios to the NBE vary with excitation depth for both undoped and H-doped ZnO crystals. The intensities of the green and yellow emissions exhibit sublinear dependencies on electron beam excitation density while the NBE intensity increases linearly with the excitation density. These saturation effects with increasing excitation density must be taken into account when assessing defects in ZnO by luminescence characterization.

(Bi,Sb)2Te3 + 4 mol%PbTe was quenched in water and on a rotating copper wheel (melt spinning). It was found that PbTe was immiscible in (Bi,Sb)2Te3 when the material is quenched in water and that the thermoelectric figure of merit increases by annealing. Natural nanostructures (nns) were found in melt-spun (Bi,Sb)2Te3, whereas they were hard to detect in (Bi,Sb)2Te3 alloyed with PbTe. There is a correlation between the orientation of the strain field and the nns. Within the grains of melt-spun (Bi,Sb)2Te3 alloyed with PbTe, the chemical composition was homogeneous. An enrichment of Pb was found at the grain boundaries. Quenched (Bi,Sb)2Te3 alloyed with 0.3 wt%PbTe have been spark plasma sintered (SPS). After optimization, the Seebeck coefficients of the melt-spun SPS (MS-SPS) materials were larger than for materials quenched in water and sintered (QW-SPS) materials. In addition, the mobility increases with the carrier concentration in MS-SPS materials, whereas it decreases in QW-SPS materials.

Ferromagnetic resonance investigations on Ni nanowires are reported. The angular dependence of the resonance line position is analyzed within a thermodynamic approach that includes shape anisotropy (ellipsoids of revolution), magnetocrystalline anisotropies (cubic and uniaxial), and dipole–dipole interactions. The results are supported by hysteresis loops, obtained on the same sample.

Bismuth sulfide (Bi2S3) polycrystalline bulks with a high relative density (>90%) were fabricated by combining mechanical alloying (MA) and spark plasma sintering (SPS). The microstructural and thermoelectric (TE) properties were investigated with a special emphasis on the influence of SPS temperature. The components (Bi/S ratio), grain size, and relative density of Bi2S3 bulk are sensitive to the SPS temperature, which all affect the electrical transport properties of samples. Elevating SPS temperature results in grain growth, densification, and spontaneous texturing, which benefit to enhance TE properties, whereas overheating leads to severe volatilization of both S and Bi and formation of porous microstructure. The highest figure of merit value reaches 0.22 at 573 K for the Bi2S3 sample obtained by applying SPS at 673 K for 5 min, which is the maximum value reported so far in bulk Bi2S3 system. The enhanced TE property of cheap and environmental friendly Bi2S3 material indicates a great promise in TE devices.

Thermomigration in Pb-free SnAg solder alloys is investigated during accelerated electromigration tests under 9.7 × 103 A/cm2 at 150 °C. It is found that Cu–Sn intermetallic compounds (IMCs) migrate toward the cold end on the substrate side and, as a result, voids accumulate in the chip side for the bump with current flowing from the substrate end to the chip end. Theoretical calculations indicate that the thermomigration force is greater than the electromigration force at a thermal gradient above 400 °C/cm for this stressing condition. Copper atoms may migrate against current flow and become the dominant diffusion species. On the other hand, Ni–Sn IMCs did not migrate even under a huge thermal gradient of 1400 °C/cm. These findings provide more understanding on the thermomigration of metallization materials in flip-chip solder joints.

A series of red-emitting phosphors with compositions of La2(Mo1−zSiz)2O9:0.05Eu3+ (0 ≤ z ≤ 0.10) with strong near-UV absorption were prepared by solid-state method. The structure and luminescence properties were investigated by x-ray powder diffraction, UV–vis diffuse reflectivity, and photoluminescence spectra. The luminescent properties as a function of Si4+ concentrations were systematically studied. Under excitation of a wide range near-UV (250–430 nm) or blue light, Si4+-doped series phosphors exhibit characteristic red emission of Eu3+ peaked at 615 nm. The incorporation of Si4+ into La2Mo2O9:0.05Eu3+ phosphor leads to the improvement of the excitation broad band and sharp peaks, as well as the broadening of charge transfer band. Appropriate amount of Si4+ doping can enhance the red luminescence intensity. Finally, the possible reasons for the luminescence enhancement via the corporation of Si4+ were explained.

We report the low-temperature synthesis and characterization of polyvinylpyrrolidone (PVP)-capped FeAu magneto-plasmonic multifunctional nanoparticles by a one-step nanoemulsion process. The Fourier transform infrared spectroscopy study proves the PVP coating on the surface of the resultant FeAu nanoparticles, whereas the structural, magnetic, and optical analysis illustrates the fusion of iron and gold into one single nanostructure showing the nanoparticle shape and a tight size distribution with an average size of 11.3 nm, followed by the growth habit compared to other relevant nanoparticles. Moreover, the PVP-capped FeAu nanoparticles manifest soft ferromagnetic behavior with a small coercivity of ∼40 Oe at room temperature. The corresponding magnetic hysteresis curves were elucidated by modified bi-phase Langevin equations, which were reasonably interpreted with the binary particle size distribution. The nanoparticles reveal a well-defined surface plasmon resonance band at ∼546 nm and a visual demonstration shows the magnetic separability of all nanoparticles for potential magnetic and/or optical manipulation.

The unique and highly utilized properties of TiO2 nanotubes are a direct result of nanotube architecture. To create different engineered architectures, the effects of electrolyte solution, time, and temperature on the anodization of titanium foil were studied along with the resultant anodized titanium oxide (ATO) nanotube architectures encompassing nanotube length, pore diameter, wall thickness, smoothness, and ordered array structure. Titanium foil was anodized in three different electrolyte solutions: one aqueous [consisting of NH4F and (NH4)2SO4] and two nonaqueous (glycerol or ethylene glycol, both containing NH4F) at varying temperatures and anodization times. Variation in anodization applied voltage, initial current, and effect of F− ion concentration on ATO nanotube architecture was also studied. Anodization in the aqueous electrolyte produced short, rough nanotube arrays, whereas anodization in organic electrolytes produced long, smooth nanotube arrays greater than 10 μm in length. A position effect, relative to the solution–air interface, was observed in this work. Furthermore, it was found that anodization in glycerol at elevated temperatures for several hours could possibly produce freely dispersed individual nanotubes.

Mg2Si1−xSnx compounds are promising as “environmentally friendly” thermoelectric (TE) materials. For years, investigations of the TE properties of these compounds have been hindered by the poor reproducibility in sample preparation. In this work, we used a recently developed simple B2O3 flux method to prepare Mg2Si1−xSnx compounds over a wide composition range (0.1 ≤x≤ 0.8). The phase structure, microstructure, and TE properties have been investigated. We found that a miscibility gap existed at 0.2 ≤x≤ 0.45, substantially lower than the more generally accepted values 0.4 ≤x≤ 0.6, and a low lattice thermal conductivity of 1.4 W·m−1·K−1 in undoped Mg2Si0.55Sn0.45, which led to a ZT ∼0.3 at 550 K. These results constitute a solid basis for investigating further optimization of the Mg2Si1−xSnx-based TE materials via doping and possibly nanostrucuring approaches.