High-concentration niobium (V)-doped titanium dioxide (TiO2) nanoparticles of the nonequilibrium chemical composition have been synthesized via Ar/O2 radio-frequency thermal plasma oxidation of mist precursor solutions with various Nb5+ concentrations (Nb/(Ti + Nb) = 0–25.0 at.%). The solubility as high as ∼25.0 at.% has not been achieved before by wet-chemical techniques. The preferable anatase formation was attained in the plasma-synthesized powders and was enhanced by the niobium doping. All the powders were heated at high temperatures (600–800 °C) to investigate their phase transformation, band gap variation, inter-particulate binding behavior, and photocatalytic stability. The transformation from anatase to rutile was effectively inhibited by increasing the Nb5+ content. The Nb5+ doping prevented the band gap of TiO2 from narrowing after the heating. At high temperatures, Nb5+ doping could not only preserve particle size but also prevent inter-particulate binding. High concentration (25.0 at.%) Nb5+ doping retained the photocatalytic performance almost invariably irrespective of being thermally treated.

We grew epitaxial SrTiO3 (STO) thin films on (001) LaAlO3 substrates via a two-step procedure using pulsed laser deposition and studied them with transmission electron microscopy in plane-view and cross-sectional samples. We found that partial misfit dislocations are the main interfacial defects, whereas planar defects are the main defects in STO films. Our results suggest that a three-dimensional island mode dominates the growth of the STO film.

High quality factor and near-zero temperature coefficient of resonant frequency (τf) are the two key issues for a certain microwave dielectric material system used in microstrip patch antennas. ZnTiO3-based ceramics is a promising candidate for microstrip patch antennas. On inhibiting the decomposition of ZnTiO3 by adding sufficient amount of MgO, high quality factor microwave dielectric material (Zn0.7Mg0.3)TiO3 was obtained. The deviations between theoretical and observed dielectric polarizabilites, the packing fraction, and bond valence were calculated to analyze correlation between structure and properties of (Zn0.7Mg0.3)TiO3. TiO2 was added to adjust τf of (Zn0.7Mg0.3)TiO3, and 0.82(Zn0.7Mg0.3)TiO3–0.18TiO2 with an εr of 28.5, a Qf of 125,050 GHz, and a near-zero τf which satisfied the requirement as a substrate material for microstrip patch antenna was obtained at 1100 °C. In addition, a dielectric microstrip antenna was designed and fabricated using the proposed dielectric materials. The microstrip patch antenna exhibited a −34.96 dB return loss and a 1.05 voltage standing wave ratio at 2.5 GHz.

Weak-beam dark-field images of dislocations interacting with particles acquired over a large angular range were used to reconstruct tomograms, which were then used as the basis to construct a three-dimensional (3D) model of the dislocation structure. These capabilities facilitate viewing the dislocation structure from different directions, recovering the information lost in the electron beam direction. Coupling these capabilities and a method to include the specimen coordinate system within them with conventional dislocation analysis enables a full characterization of the dislocation microstructure in three dimensions. This approach is used to understand the 3D nature of the interaction of dislocations and a twist boundary with Al3Sc particles in an Al–Mg–Sc alloy.

The morphology of semiconducting nanowires, including kinked and branched wires, must be controlled in order to produce functional devices. Here, we describe some of the experimental and theoretical work involving complex morphologies of Au-catalyzed Si nanowires grown using the vapor–liquid–solid technique. Although there is a broad parameter space to explore, experiments have highlighted the importance of the precursor and impurity partial pressures on kinking behavior. Theoretical and modeling work has indicated that the stability of and transitions in droplet configuration are important for growth direction changes that can lead to complex morphologies. We describe recent phase-field simulations of nanowire growth that address the dynamics of liquid droplets during vapor–liquid–solid growth, as well as the implications of these results for the formation of wires with complex morphology.

A combined melt-spinning and spark-plasma-sintering (SPS) procedure has proven to be effective in preparing high-performance (Bi,Sb)2Te3 thermoelectric (TE) nanocomposites via creating and optimizing their resulting multiscale microstructures. (Bi,Sb)2Te3 possesses a highly anisotropic crystal structure; therefore, it is important to investigate any potential correlation between the SPS conditions, the as-formed microstructures, and the resulting TE properties. In this work, we investigate the correlation between the SPS pressure, the microstructure texture, and the anisotropy of the total thermal conductivity in these melt-spun spark-plasma-sintered (Bi,Sb)2Te3 compounds. The thermal conductivity has been measured in directions that are both perpendicular and parallel to the pressing (or force) direction by rearranging the sample geometry as described in the text. The results show that the anisotropy of thermal conductivity is ∼0, 2–3, 6–7, and 13–15% for the samples sintered at pressures of 20, 30, 45, and 60 MPa, respectively. These results are consistent with an increasing degree of orientation observed by x-ray diffraction and electron microscopy.

ZnS:Cu,Cl,Mn,Te, which shows red AC powder electroluminescence (ACPEL) emission, was synthesized using a conventional wet synthesis and a sealed vessel method. The photoluminescence (PL) and ACPEL were characterized. After the second firing, 0.5 wt% tellurium (Te)-doped ZnS:Cu,Cl,Mn,Te phosphor shows almost red PL emission from the 4T1–6A1 transition of Mn2+ ions, which are affected by the Te. Extended x-ray absorption fine structure analysis on the Mn K edge proved that the substitution of sulfur (S) with Te changes the local crystal field of the Mn2+ ions and shifts an orange emission (∼588 nm) to a red emission (∼650 nm). A red ACPEL emission is first shown in 0.5 wt%Te-doped ZnS:Cu,Cl,Mn,Te after the third firing phosphor even though its luminance is not very high. The origin of the ACPEL emission is assumed to be not a CuxS–ZnS p–n junction but a CuxTe–ZnS p–n junction. Raman spectra were characterized to support that the red ACPEL emission is probably attributed to a CuxTe–ZnS p–n junction.

Anodized aluminum oxide (AAO), well-known hexagonally ordered vertical pore nanostructure, can be altered to form nanotubular AAO arrays potentially having many favorable properties due to its large surface area and unique geometry. We present here a creation of novel nanotubular AAO structure by the hard anodization technique. Because of the guided formation of void channels at triple cell junctions during the course of the controlled anodization process, periodically spaced-apart aluminum oxide nanotubular geometry could be achieved over large areas. Further separation to well-defined individual AAO nanotube arrays was obtained when etched in a mixed CuCl2/HCl solution during Al substrate removal. Nanotubular geometry AAO with periodic and mechanically robust structure can be useful not only for biomedical applications such as to enhance cell adhesion and viability or drug delivery vehicles, but also as a large-surface-area catalyst support or sensor elements.

Upon rapid heating to a high temperature (~800 °C), mixtures of nitrate compounds and urea created nano and submicron metal particles. The process (reductive/expansion synthesis, RES) results in atomic scale mixing. The product formed from mixed-nitrate (Fe + Ni) salts and urea created true metallic alloy. Unlike other product-from-powder synthesis processes, this process produced only zero valent metal. Initial work suggests this method is a scalable and efficient means for making metallic nanoparticles. Although this is primarily a phenomenological report, a preliminary model is presented: Initially, nitrates decompose to oxide; thus in the absence of urea metal oxide particles form, as in the case of combustion synthesis. In the case of urea/nitrate mixtures, there is a “convolution” of decomposition processes. Urea decomposes to yield reducing gases, leading to the formation of metal rather than oxide. Rapid “expansion” of gas leads to “shattering,” resulting in highly dispersed particles.

In this work, epitaxial (001) BiFeO3 thin films were deposited on SrTiO3 and TbScO3 single-crystal substrates and analyzed with high-resolution x-ray diffraction—reciprocal space mapping. A basic method was developed to extract structural details of the as-grown BiFeO3 film, including (i) epitaxial strain, (ii) ferroelastic domains, and (iii) lattice rotations. After demonstrating the method, extrinsic distortions at vertical twin walls were determined for specific BiFeO3 heterostructures. A relatively large distortion (0.20° ± 0.08°) was measured in a multidomain (12) and incoherent film, while a nearly intrinsic distortion (0.04° ± 0.03°) was measured in a two-domain coherent film. This work offers insights into the structure of multiferroic BiFeO3 thin films with a general approach that is appropriate for low symmetry epitaxial heterostructures.

The Maugis–Barquins (MB) solutions for the adhesive contact between an axisymmetric indenter and an elastic half-space are modified by incorporating the interfacial energy defined by the real area of contact. With the modified MB solutions, general relations for contact stiffness including adhesive effects in indentation analysis are derived. Numerical calculations showed that the difference in expected stiffness for the modified MB model compared to the standard MB results can be significant at low loads of interest in atomic force microscopy measurements and also for indentation tests at high load if the interfacial energy is large (∼0.1 J/m2) and the material is soft (Young’s modulus ≤100 MPa).

The shapes of the interfacial delamination crack and stress states during wedge indentation in a soft-film-on-hard-substrate system were investigated systematically using the three-dimensional (3D) finite element simulation and wedge indentation experiment. In the simulation, a traction–separation law was used to characterize the failure behaviors of the interface. The effects of the wedge indenter tip length and the film thickness on the onset and growth of interfacial delamination were analyzed. It was shown that a two-dimensional (2D) to 3D transition of stress states occurred depending on the ratio of indenter length to film thickness. Furthermore, the interfacial delamination process by wedge indentation was conducted experimentally, and comparisons between the computational and experimental results yielded quantitative good agreement. Finally, a straightforward criterion based on the curvature of the delamination crack front was proposed to indicate the transition of stress states during the interfacial delamination. A guideline was therefore proposed to classify the 2D and 3D stress states for extracting the interface adhesion properties.

InN thin films were grown on GaN underlayer with sapphire substrate by metalorganic vapor phase epitaxy under different growth conditions, including growth temperature, reactor pressure, and V/III ratio. X-ray diffraction and Raman scattering measurements reveal that the samples grown at different temperatures are mixed with different phases, especially at higher temperature. The calculated phonon dispersion curves of wurtzite, zinc-blende, and rocksalt structures show that the samples mainly contain wurtzite structure and small amount of zinc-blende phase, while the samples grown at 600 °C and 650 °C include a new structural phase other than the three well-known ones. This analysis demonstrates that the InN epilayer grown at 550 °C has the highest phase purity and better crystalline quality. Besides the key role of growth temperature, a relatively higher reactor pressure and lower V/III ratio are found to be more conducive to the improvement of crystalline quality, though they have a modest effect on the InN microstructure.

The local structures about Cu, In, and Se atoms in a series of Cu2Se–In2Se3 pseudobinary compounds have been investigated by x-ray absorption fine structure (XAFS). In K-edge XAFS and L3-edge x-ray absorption near-edge structure (XANES) suggest that CuInSe2, Cu0.9InSe1.95, Cu0.82InSe1.91, and Cu2In3Se5.5 have a nominally four-coordinated InSe4 structure, whereas CuIn3Se5 and CuIn5Se8 possess two different InSe4 structures. Cu K-edge XAFS also showed that CuIn3Se5 and CuIn5Se8 possess two different CuSe4 structures, whereas others have a CuSe4 structure. Se K-edge XANES and curve fitting analysis reveal that the Cu vacancy (VCu) gradually forms with decreasing Cu/In ratio. Moreover, the substitution of In for VCu (InCu) is observed in CuIn3Se5 and CuIn5Se8. These results were compared to the previously proposed Cu–In–Se models. We conclude that Cu0.9InSe1.95 and Cu0.82InSe1.91 have a chalcopyrite structure with VCu and that the structure of CuIn3Se5 and CuIn5Se8 is a stannite-like structure with VCu and InCu defects.

Nickel-titanium (NiTi) alloys combine several remarkable characteristics, among them are shape-memory, superelasticity, great strain recovery, good biocompatibility, and corrosion resistance. These render them well suited to a wide range of medical applications, such as cardiovascular stents, laparoscopy, and dental applications such as NiTi endodontic files (EFs) used for root canal treatment, which are the focus of this work. Unfortunately, fatigue-induced and incidental failure of NiTi EFs is not uncommon, which may lead to severe medical consequences. Here we examine the effects of cobalt coatings with impregnated fullerene-like WS2 nanoparticles on file fatigue and failure. Dynamic x-ray diffraction, nanoindentation and torque measurements all indicate a significant improvement in the fatigue resistance and time to breakage of the coated files, stemming from reduced friction between the file and the surrounding tissue. These methods are possibly applicable to a variety of NiTi-based medical devices where fatigue and consequent failure are of relevance.

In this work, poly(2-ethyl-2-oxazoline) (PEtOx) is used for synthesis of silver-nanoparticle-embedded polymer nanofibers through a simple polyol process. The factors, such as AgNO3/PEtOx molar ratio R, reaction temperature T, and reaction time t, which would influence the morphology of the nanofiber were studied extensively. Long linear PEtOx nanofibers with length more than 1 μm were obtained under the optimum conditions of R = 5, T = 150 °C, and t = 1 h. PEtOx and reaction temperature were found to be the key factors affecting the final morphology of nanofibers in this system. The physical and chemical properties of these silver-nanoparticle-embedded PEtOx nanofibers were characterized by transmission electron microscopy, high-resolution transmission electron microscopy, energy dispersive spectrum, x-ray diffraction, and inductive coupled plasma-mass spectrometry. The growth mechanism of the nanofibers is elucidated, and the process is demonstrated to be both kinetically and thermodynamically controlled.

The thermal transitions and the nonisothermal cold crystallization kinetics of poly(ethylene terephthalate) (PET) at constant heating rates were investigated using differential scanning calorimetry. It was found that the glass transition and crystallization temperature increased with the heating rates, while the melting temperature showed a little variation for the heating rates used. Crystallization and melting latent heats were remarkably constant, independent of the heating rate. Kinetics parameters were determined using Ozawa model. Two different kinetic regimes were identified, corresponding to primary and secondary crystallization, at low and high fractional crystallization, respectively, both following Ozawa’s model. Kinetics parameters were determined for the primary and secondary regimes; the pre-exponential constant (KT) and Ozawa’s exponent (m) decreased with increasing crystallization temperature. The combined kinetic parameter increased exponentially with temperature; activation energies were estimated using Arrhenius plots for the two PET crystallization regimes.

The catalytic influence of Ni, Zr2Ni5, and LaNi5 on the dehydrogenation properties of milled MgH2 was investigated. MgH2 milled in the presence of Ni (5 wt%) and Zr2Ni5 (5 wt%) catalysts for 2 h showed apparent activation energies, EA, of 81 and 79 kJ/mol, respectively, corresponding to ∼50% decrease in EA and a moderate decrease (∼100 °C) in the decomposition temperature (Tdec). A further 27 °C decrease in Tdec was observed after milling with 10 wt%Ni. Based on the EA values, the catalytic activity decreased in the following order: Ni ≈ Zr2Ni5 > LaNi5. X-ray photoelectron spectroscopy analysis of the milled and dehydrogenated states of the hydrides modified with Ni catalyst revealed that the observed reduction in EA may be due to the ability of Ni catalyst to decrease the amount of oxygen atoms in defective positions that are capable of blocking catalytically active sites thereby enhancing the dehydrogenation kinetics. In particular, our results reveal a strong correlation between the type of oxygen species adsorbed on Ni-modified MgH2 and the EA of the dehydrogenation reaction.

Transparent and high preferential c-axis-oriented ZnO thin films doped with SiO2 have been prepared by sol–gel method using zinc nitrate and tetraethylorthosilicate as precursors, absolute ethanol as solvent, and diethanolamine as sol stabilizer. Thin film deposition was performed by spin coating technique at a spinning speed of 2000 rpm/sec on glass substrate followed by calcinations at 500 °C. The structural characteristics of the samples were analyzed by x-ray diffractometer and atomic force microscope. The optical properties were studied by an ultraviolet–visible spectrophotometer. The results show that all the prepared ZnO thin films have a compact hexagonal wurtzite structure. With the change in the amount of SiO2 dopants, the intensity of (002) peak, particle size, surface root mean square roughness, thickness, transmittance, absorbance, and the optical band gap of the ZnO–SiO2 thin films were changed as well.

We report on the electrical and structural properties of boron-doped diamond tips commonly used for in-situ electromechanical testing during nanoindentation. The boron dopant environment, as evidenced by cathodoluminescence (CL) microscopy, revealed significantly different boron states within each tip. Characteristic emission bands of both electrically activated and nonelectrically activated boron centers were identified in all boron-doped tips. Surface CL mapping also revealed vastly different surface properties, confirming a high amount of nonelectrically activated boron clusters at the tip surface. Raman microspectroscopy analysis showed that structural characteristics at the atomic scale for boron-doped tips also differ significantly when compared to an undoped diamond tip. Furthermore, the active boron concentration, as inferred via the Raman analysis, varied greatly from tip-to-tip. It was found that tips (or tip areas) with low overall boron concentration have a higher number of electrically inactive boron, and thus non-Ohmic contacts were made when these tips contacted metallic substrates. Conversely, tips that have higher boron concentrations and a higher number of electrically active boron centers display Ohmic-like contacts. Our results demonstrate the necessity to understand and fully characterize the boron environments, boron concentrations, and atomic structure of the tips prior to performing in situ electromechanical experiments, particularly if quantitative electrical data are required.