The fabrication of capillary cylindrical crystals from colloidal suspension with controllable thickness by evaporation-induced self-assembly method has been investigated. The thickness of the hollow cylinders can be precisely controlled ranging from monolayer to tens of layers by varying the suspension concentration. With the increase of suspension concentration, the particles fill completely inside capillaries to form solid bulk crystals and the critical values are found in capillaries with various diameters. Scanning electron microscope images confirm the face-centered-cubic structure in both crystals, but with two different [111] crystalline directions. The experiment parameters, such as the solvent, concentration of the suspension and inner diameter of capillary are studied for the quality and the number of film layers control. Qualitative analysis has been performed to probe into the solvent evaporation modes and the mechanism of particle arrangement inside the capillary.

Nanofibers (NFs) of Ga-doped ZnO (GZO) were prepared by electrospinning of polymer–salts solution. Sintering profiles reported in the literature led to loss of the fibrous structure. Hence, the morphology, thermal stability, and phase composition of green and sintered fibers were investigated as function of sintering conditions to elucidate this degradation process. Optimal results were obtained at 400 °C for 30 min. This low temperature sintering of GZO fibers has not been previously reported. The fibers were porous with a significant surface area, making it possible to test their sensitivity to environmental changes. In particular, the response of the GZO NFs to changes in humidity was demonstrated for the first time. The electrical and sensing properties of single NFs prepared at these conditions were studied using a field-effect transistor mode.

Multiwalled carbon nanotubes/Pd nanoparticles (CNT/Pd) were prepared by different four synthesis techniques. After the chemical oxidation of CNTs, the infrared absorption data indicated the existence of several functional groups loaded on the CNTs surfaces. The first Pd deposition technique went through the processes of Sn sensitization and Pd deposition on the functionalized surfaces of CNTs. The second method was Pd deposition by polyol process. The third method was Pd deposition using hydrazine in acidic media. In the fourth method, fourth generation poly(amidoamine) dendrimer and sodium borohydride were used as an intermediator between Pd and the surfaces of CNTs and as a reducing agent of the palladium chloride, respectively. It was observed from transmission electron microscope analysis of the produced CNT/Pd nanoparticles that the Pd particles on the CNTs prepared by the fourth method had the smallest average particle size of 3 nm. The Pd contents in the produced CNT/Pd nanocomposite powders were determined by thermogravimetric analysis.

Platinum (Pt) nanoparticles were synthesized on tin dioxide (SnO2) nanowires by applying γ-ray radiolysis. The growth behavior of Pt nanoparticles was systematically investigated as a function of precursor concentration, illumination intensity and exposure time of the γ-rays. We found that these processing parameters greatly influenced the growth behavior of Pt nanoparticles in terms of size and formation density. Vapor-phase-grown SnO2 nanowires were uniformly covered with Pt nanoparticles by the radiolysis process. The Pt nanoparticle-functionalized SnO2 nanowires were tested as sensors for detecting reductive gases including carbon monoxide, toluene, and benzene. The results indicate that the γ-ray radiolysis is an efficient way of functionalizing the surface of oxide nanowires with catalytic Pt nanoparticles.

The present study aims to determine the optimum radio frequency (RF) sputtering power to obtain the desired W–TiO2 nanotubes for the best photoelectrochemical (PEC) performance. Tungsten (W) was deposited on titania (TiO2) nanotube arrays via RF sputtering technique under different sputtering powers from 50 to 250 W. The optimum content of W on TiO2 nanotube arrays play a significant role in maximizing the photocurrent generation efficiency to promote charge separation by accumulation of photogenerated electrons. The sputtering power below 180 W exhibited high-ordered and unbroken TiO2 nanotube arrays. However, the sputtering power over 180 W exhibited broken nanotube arrays and an oxide layer was formed due to the impact of high energy ions accelerated by a high sputtering power. The TiO2 nanotube arrays sputtered with tungsten at 50 W showed a better photocurrent density (1.55 mA/cm2), with a photoconversion efficiency of 2.2% in the PEC performance among the samples due to the effective charge separation and reduced recombination center in the resultant W–TiO2 nanotubes.

The structural, mechanical, and electronic properties of rhenium, osmium, and tungsten tetranitrides, XN4 (X = Re, Os, W) with the orthorhombic ReP4-type structure have been investigated by first-principles calculations using density functional plane-wave pseudopotential method. The calculated formation enthalpies and elastic constants show that these tetranitrides are energetically and mechanically stable. It is appeared from the calculated band structures and density of states that ReN4 and new proposed WN4 are metallic, while OsN4 is semiconductor with a band gap of 0.64 eV. The hardness values of all compounds obtained from different hardness methods indicate that these tetranitrides are superhard materials.

Nanocomposite Zr0.52Al0.48N1.11 thin films consisting of crystalline grains surrounded by an amorphous matrix were deposited using cathodic arc evaporation. The structure evolution after annealing of the films was studied using high-energy x-ray scattering and transmission electron microscopy. The mechanical properties were characterized by nanoindentation on as-deposited and annealed films. After annealing in temperatures of 1050–1400 °C, nucleation and grain growth of cubic ZrN takes place in the film. This increases the hardness, which reaches a maximum, while parts of the film remain amorphous. Grain growth of the hexagonal AlN phase occurs above 1300 °C.

NbN thin films grown on Nb using pulsed laser deposition (PLD) were investigated for film crystal structures. The nanomechanical properties of NbN on Nb were examined as a function of the film/substrate crystal structure. X-ray diffraction (XRD) reveals peaks that correspond to δ-NbN cubic and β-Nb2N hexagonal phases in addition to δ′-NbN phase. Samples of various crystal structures were tested for phase characterization, microstructure, and surface morphology using XRD analysis, scanning electron microscopy, and atomic force microscopy. The nanomechanical properties were investigated using nanoindentation. The results indicate that there are clear effects of the crystal structure on the hardness of the PLD-grown NbNx films.

In this work, different methods to estimate the value of thin film residual stresses using instrumented indentation data were analyzed. This study considered procedures proposed in the literature, as well as a modification on one of these methods and a new approach based on the effect of residual stress on the value of hardness calculated via the Oliver and Pharr method. The analysis of these methods was centered on an axisymmetric two-dimensional finite element model, which was developed to simulate instrumented indentation testing of thin ceramic films deposited onto hard steel substrates. Simulations were conducted varying the level of film residual stress, film strain hardening exponent, film yield strength, and film Poisson’s ratio. Different ratios of maximum penetration depth hmax over film thickness t were also considered, including h/t = 0.04, for which the contribution of the substrate in the mechanical response of the system is not significant. Residual stresses were then calculated following the procedures mentioned above and compared with the values used as input in the numerical simulations. In general, results indicate the difference that each method provides with respect to the input values depends on the conditions studied. The method by Suresh and Giannakopoulos consistently overestimated the values when stresses were compressive. The method provided by Wang et al. has shown less dependence on h/t than the others.

Plasticity initiation behavior that appears as a pop-in phenomenon on a loading process during indentation-induced deformation was investigated to reveal the effects of lattice defects such as grain boundary and solute element for various metallic materials including Fe alloys through instrumented nanoindentation techniques. The critical load Pc of pop-in on a loading process is lower in the vicinity of the grain boundary than in the grain interior, but the relative hardness of the boundary is equal to or greater than that in grain interior. In-solution Si produces a larger increase in the Pc for both the grain boundary and the grain interior in the Fe–Si alloy than in the interstitial-free steel. The maximum shear stress corresponding to the Pc underneath the indenter is directly proportional to the shear modulus in single crystals with various crystallographic structures. Microstructural effects on the Pc are considered based on some dislocation models.

LiMn2O4 nanowires have been synthesized by a two-step approach. γ-MnOOH nanowires are firstly synthesized by hydrothermal method and after further sintering with LiOH at 750 °C for about 3 h, the wire-like LiMn2O4 can be obtained. The structure of the final product is characterized by x-ray diffraction using Rietveld refinement. Its electrochemical performance is investigated by galvanostatic tests. The as-prepared LiMn2O4 nanowires display excellent cyclability. The LiMn2O4 nanowires with good cycle stability may be beneficial from the structural stability of LiMn2O4 crystal cell and one-dimensional nanostructure.

Oxidation kinetics of copper nanowires (CuNWs) with diameter 25 ± 4 nm were studied. The dry powder of CuNWs before oxidation comprises 73.2 wt% Cu and 26.8 wt% Cu2O. The oxidation reaction can be divided into two stages at weight of 111.2%. Oxidized CuNWs after Stage 1 consist of Cu2O and CuO. Oxidized CuNWs after Stage 2 comprise CuO only. The activation energies for both stages are determined by Kissinger method and other five isoconversional methods: Flynn–Wall–Osawa, Starink, Kissinger–Akahira–Sunose, Boswell and Friedman differential methods. The isoconversional activation energies determined by Starink method are used to fit different master plots. The Johnson–Mehl–Avrami equation gives the best fit. Surface atoms are the sites for the random nucleation, and the crystallite strain in CuNWs is the driving force for the growth of nuclei during the oxidation process.

In this article, we report the unique microstructural characteristics of YBa2Cu3O7-x (YBCO)/BaSnO3 (BSO) nanocomposite thin films on LaAlO3 (LAO) substrates. The BSO secondary phase grows as self-assembled vertically aligned nanopillars uniformly distributed in the superconducting YBCO matrix. Detailed microstructure and strain studies including x-ray diffraction, cross-section and plan-view transmission electron microscopy, and geometric phase analysis reveal that, as the BSO doping concentration varied from 2 mol% to 20 mol%, the nanopillar density increased from 0.26 × 1011/cm2 to 1.44 × 1011/cm2 while the diameter of the nanopillars remains relatively constant (7–8 nm in diameter). The strain state of the YBCO matrix is affected by both lateral and vertical lattice strains; while, the BSO lattice is strongly tuned by YBCO rather than the substrate. A high-density array of dislocations in the order of 1013/cm2 was observed along the vertical heterogeneous interfaces throughout the YBCO film thickness for all doping concentrations.

Two-micrometer-thick Pb0.97La0.02(Zr0.98Ti0.02)O3 (PLZT) antiferroelectric films, with the addition of different PbO insert layer, were successfully fabricated on LaNiO3/Si substrates through a sol–gel method, and their microstructure and the energy storage performance were investigated in detail. X-ray diffraction curves and scanning electron microscopy images indicated that all the PLZT films showed a strong (042)-preferred orientation and had a uniform surface microstructure. The electrical measurements illustrated that the capacitive density and saturation polarization values of the thick films were improved by the PbO insert layer. As a result, PLZT thick films with 0.4‐M/L PbO‐insert layer possessed an enhanced energy storage density and energy storage efficiency, which were 25.2 J/cm3 and 52.3% measured at 984 kV/cm, respectively. Moreover, after 106 switching, the Jreco values of the corresponding films were only declined from 17.5 to 16.1 J/cm3, indicating good fatigue endurance.