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.

X-ray photoemission spectroscopy using synchrotron radiation from 100 to 1486.6 eV was used to investigate polarity-dependent differences between the Zn-polar (0001) and the O-polar () faces of ultrahigh vacuum cleaved hydrothermally grown ZnO single crystals. The cleaved polar surfaces showed a characteristic polarity effect in that the intensity of emission from the lowest binding energy O 2p related valence band states was significantly stronger on the Zn-polar face, even when the cleaved surfaces were imperfect with irregular nonatomically flat features. A residual submonolayer hydroxyl termination of approximately 0.5 ML was observed on both the Zn-polar and O-polar surfaces immediately after cleaving. The near-surface downward band bending on the O-polar face was removed by the cleaving process leaving almost flat bands, while on the cleaved Zn-polar face, emission from states above the valence band edge was observed.

Pop-ins on nanoindentation load–displacement curves of a ferritic steel were correlated with yield drops on its tensile stress–strain curves. To investigate the relationship between these two phenomena, nanoindentation and tensile tests were performed on annealed specimens, prestrained specimens, and specimens aged for various times after prestraining. Clear nanoindentation pop-ins were observed on annealed specimens, which disappeared when specimens were indented right after the prestrain, but reappeared to varying degrees after strain aging. Yield drops in tensile tests showed similar disappearance and appearance, indicating that the two phenomena, at the nano- and macro-scale, respectively, are closely related and influenced by dislocation locking by solutes (Cottrell atmospheres).

This study focuses on nanoindentation creep in polycarbonate (PC) and syndiotactic polystyrene (sPS) throughout the transient and steady-state regions. The viscoelastic Burgers model is used to explain transient creep data, while the power-law creep model is used to interpret steady-state creep data. The Newtonian shear viscosity of the Maxwell element and Young’s modulus of the Kelvin element are greater for the creep period than for the preload period, and an opposite trend is noted in the Newtonian shear viscosity of the Kelvin element and Young’s modulus of the Maxwell element. The fact that the Young’s moduli of Maxwell and Kelvin elements in the creep period are different from those in the preload period implies that a stress-induced mesomorphic structure forms or that crystallization occurs in nanoindentation creep. While the strain rate increases with decreasing preload period, the stress exponent factor is almost the same for all preload periods.

Results are presented for modeling the growth of TiO2 on the rutile (110) surface. We illustrate how long time scale dynamics techniques can be used to model thin film growth at realistic growth rates. The system evolution between deposition events is achieved through an on-the-fly Kinetic Monte Carlo method, which finds diffusion pathways and barriers without prior knowledge of transitions. We examine effects of various experimental parameters, such as substrate bias, plasma density, and stoichiometry of the deposited species. Growth of TiO2 via three deposition methods has been investigated: evaporation (thermal and electron beam), ion-beam assist, and reactive magnetron sputtering. We conclude that the evaporation process produces a void filled, incomplete structure even with the low-energy ion-beam assist, but that the sputtering process produces crystalline growth. The energy of the deposition method plays an important role in the film quality.

We describe the fabrication of core–shell colloidal spheres composed of a shell of tin sulfide and a core of polystyrene. The tin sulfide shell is deposited on micrometer-sized latex spheres using a sonochemical technique. By angle-dependent light scattering and electron microscopy, we find that the refractive index of the shell is 3.0 at a wave length of 1064 nm, and the shell’s thickness is controllable in the range of 30–60 nm. The resulting spheres have a narrow distribution of sizes, are stable in aqueous suspension, and are very strong scatterers in the near infrared with potential application in photonic band gap materials or other photonic devices.

The phase evolution, nucleation, and sintered ceramics of barium titanate (BaTiO3, BT) powder prepared by solid-state synthesis with an ultrafine starting material (27 m2/g of BaCO3 and 190 m2/g of TiO2) were investigated in this study. Surface diffusion between BaCO3 and TiO2 was observed at a relatively low temperature of 400 °C by transmission electron microscopy. Rapid nucleation of the BT and cubic BT phases was observed at 500 °C by x-ray diffraction. The derivative thermogravimetry curve clearly shows a single step of BT formation at 600 °C. In short, pure BT particles with an average particle size of 250 nm and high tetragonality were prepared by solid-state synthesis, which produced X7R ceramics with high dielectric permittivity, high insulation resistance, and a clear core–shell structure.

Yb3+:Sr3Y2(BO3)4 crystals have been grown successfully by Czochralski method. The compound crystallizes in orthorhombic system, space group Pnma, with a = 7.4062(3) Å, b = 16.0030(7) Å, c = 8.7130(4) Å, α = β = γ = 90°, and Z = 4. Yb3+:Sr3Y2(BO3)4 has three cationic sites and two kinds of boron sites. The crystalline quality of the Yb3+:Sr3Y2(BO3)4 single crystal was verified by the width of the x-ray diffraction peak in the x-ray rocking curves measurement. The absorption spectrum, emission spectrum, and fluorescence lifetime of the Yb3+:Sr3Y2(BO3)4 crystal were detected at room temperature. The laser performance parameters βmin, Ipsat, and Imin were calculated.

The role played by catalyst aggregates in the growth of carbon nanocoils (CNCs) by a chemical vapor deposition (CVD) method has been studied. The experimental results show that CNCs can be grown from the discrete aggregates on a substrate with a porous surface, while only some irregular carbon nanofibers are grown from those on a flat substrate. It is accepted from the viewpoint of mechanics that the spiral motion of a CNC should generate a torsional moment on its base that attaches to an aggregate. The catalyst particles readily expand on the flat substrate during the CVD process and form a loose aggregate, which cannot provide a strong interaction between the aggregate and the base of a carbon fiber grown from there. On the contrary, the expansion of catalyst particles in a microsized hole is restricted by the surrounding wall of the hole, leading to the formation of a compact aggregate that fixes the base of the grown fiber. A perfect CNC can be grown only under the condition that its base is firmly fixed by an aggregate that can balance the torsional moment of the CNC during its spiral growth.

First-principles fully relaxed tensile and shear test simulations were performed on tilt Fe grain-boundaries (GBs) with and without hydrogen (H) segregation, to investigate the mechanisms of GB embrittlement enhanced by H segregation. Premature fracture was found in the H-segregated GB, compared with the clean GB, in the tensile test simulations. The Fe–H bond showed covalent-like and ion-like characteristics. The covalent-like characteristics reinforced the Fe–Fe bonds, but the ion-like characteristics weakened the Fe–Fe bonds as a result of charge transfer. The effect of the latter increased with increasing strain, and prevailed over the former, resulting in GB embrittlement. In the shear test simulations, variation in the GB energy for the H-segregated GB was almost the same as that for the clean GB. This is because bond-breaking and rebonding occur concurrently in GB shearing and the variations in charge transfer during shear straining are less than those during tensile straining.

Fabrication of thin film nanocomposites via decomposition and self-assembly from the vapor phase is a promising path for cost-effective fabrication of multifunctional materials. In particular, oxides as a new class of energy materials allow for rich functionalities, e.g., by combining p- and n-doped systems in catalytic or light harvesting units. Combining A-site doped perovskites ABO3 with CoFe2O4 spinel, we have investigated thin film phase composition and nanocomposite morphology in the pseudobinary system La0.6Sr0.4BO3–CoFe2O4 for B = Fe, Co, and Mn. We observe formation of an epitaxial two-phase nanocomposite for B = Fe, i.e., the coexistence of La0.6Sr0.4FeO3 and CoFe2O4. In contrast, for B = Co or Mn nanocomposites are formed, where perovskite La0.6Sr0.4BO3 solid solutions coexists with Co-rich spinel and periclase phases. We derive conclusions for the preparation of perovskite-spinel nanocomposites with well-designed doping levels.

The thermal and mechanical behavior, the water uptake (WU), and water diffusion coefficient of sulfonated poly(ether ether ketone) (SPEEK) membranes annealed at 180 °C for different times were explored by high-resolution thermogravimetric analysis, mechanical tensile tests, dynamic mechanical analysis, and WU measurements. The mechanical and thermal stability increased with the thermal treatment time, i.e., with the degree of crosslinking. The effect of residual casting solvent, dimethyl sulfoxide (DMSO), on the WU within SPEEK was probed. In presence of residual DMSO, crosslinked SPEEK exhibited higher water sorption at low and medium relative humidity (RH), and lower water sorption at high RH. These membranes have properties well adapted to fuel cell applications.

Molsidomine is one of the sydnonimine class of antianginal drugs that due to its structure exhibits both dipolar nature and aromatic properties. To select efficient carrier for the drug, unmodified and modified mesoporous silica materials were synthesized using phenyltriethoxysilane and 3-aminopropyltriethoxysilane via cocondensation and grafting routes. Synthesis of the mesoporous silica materials via cocondensation was carried out in the presence of D-glucose as pore-forming agent. Equilibrium isotherms for the adsorption of mesoionic compound molsidomine on the mesoporous silica materials were analyzed by the Langmuir, Freundlich, Redlich-Peterson and Langmuir–Freundlich (Sips) models. Langmuir model is found to be the best to explain the equilibrium data. Comparative study of the adsorption properties of the unmodified and modified mesoporous silica materials demonstrated that the phenyl-modified silica materials are the most efficient adsorbents for molsidomine. They exhibit the highest adsorption capacity and affinity in relation to the mesoionic compound.

In this study, nanoindentation was utilized to measure the local, three-dimensional properties of Kevlar 49 and Kevlar KM2 on the length scales of the fiber microstructure. First, atomic force microscopy-based methods were used to explore the extent of property changes with respect to radial position in the fibers’ axial and hoop planes. From these measurements, no significant change in response was found for Kevlar 49 fibers, consistent with transverse isotropy. However, a reduced stiffness “shell” region (up to ∼300–350 nm thick) was observed for KM2 fibers. Instrumented indentation was then used to evaluate fiber response with respect to orientation and contact size and establish a critical contact size above which the response is independent of indenter size (i.e., “homogeneous” behavior). A previously proposed analytical method for indentation of a transversely isotropic material was used to estimate the local material properties of the Kevlar fibers from the measured homogeneous response.

Effects of Ti and Si particle sizes on phase transformations of Ti–Si–Cu system were explored through differential thermal analysis (DTA), x-ray diffraction (XRD), and field emission scanning electron microscope (FESEM). For Ti[15]Si[15]Cu[45] system, fine Ti easily dissolves into Si–Cu liquid to form Ti–Si–Cu liquid at ∼795 °C, which further participates into the reaction of β-Ti and Si to yield abundant quantity of Ti5Si3 at ∼917 °C. For Ti[150]Si[15]Cu[45] system, nonetheless, the reaction of coarse Ti with Si–Cu liquid involves more difficulty in forming the ternary liquid , which is the causal factor for the delay in the formation of Ti5Si3 to ∼948 °C. For Ti[15]Si[150]Cu[45] system, coarse Si results in the formation of insufficient Si–Cu liquid initially, whereas Ti–Cu liquid forms at ∼960 °C instead, which further reacts with coarse Si to form Ti–Si–Cu liquid, and then Ti5Si3is precipitated from the liquid.

Poly(l-lactic acid) (PLLA) is one of the most studied biopolymers nowadays. Due to its good performance, it constitutes an alternative to petrochemical-derived polymers. It was largely studied by differential scanning calorimetry (DSC) and temperature-modulated DSC. Nevertheless, there is an ongoing debate of what happens at the overlapping melting processes. In the present work, the experimental setups are discussed. Different modulation conditions are proposed for the study of the glass transition, cold crystallization, and the two reported melting processes. Finally, the experimental results allowed to measure the heat capacity change at the cold crystallization and a correct interpretation of what happens at the reported double melting peak of PLLA, which involves the existence of three crystalline structures.

To possess the merits of both building blocks, i.e., the rapid interfacial electron transport of ZnO nanoneedles (NNs) and the high surface area of TiO2 nanoparticles (NPs), the ZnO NN and TiO2 NP composite photoelectrodes were prepared with controllable weight ratio. The dye-sensitized solar cell (DSSC) prototypes were fabricated based on this composite photoelectrodes, and the photoelectrical properties have been systematically studied. The results indicate that the composite cells achieve higher power conversion efficiency compared to pure TiO2 NP cells by rational tuning the weight ratio of ZnO NNs and TiO2NPs. The DSSC with 1 wt% ZnO NNs yields the highest η of 5.16%. It is elucidated by the interfacial electron transfer of DSSC with different weight of ZnO NNs using the electrochemical impedance spectra. And it is found that the DSSC with 1 wt% ZnO NNs displays the fastest interfacial electron transfer.

The (1−x)MgO–xLiF ceramics (x = 0.02–0.08) were successfully sintered when the ceramics were sintered at 950 °C for 4 h in covered crucible. From the crystal structure analysis, it was found that a small amount of Li+ cation occupied Mg2+ site in MgO ceramic; the formation of oxygen vacancy induced by Li substitution for Mg was suggested by the evaluation of the bulk conductivity and the calculation of density of state (DOS) for the (Mg13O43)−60 and (Mg11Li2O42)−58 cluster models. As for the microwave dielectric properties of the (1−x)MgO–xLiF ceramics, the dielectric constant εr and the temperature coefficient of resonant frequency values of the ceramic were independent of the lithium fluoride (LiF) content, and these values were approximately 9.5 and −62 ppm/°C. On the other hand, the quality factor values strongly depended on the LiF content. As a result, the highest value of 282,230 GHz was obtained at x = 0.04. From these results, it is determined that the LiF addition is effective in reducing the sintering temperature of MgO without any detrimental effect on the microwave dielectric properties of MgO ceramics.

Thin native oxide layers can dominate the mechanical properties of metallic thin films. However, to date there has been little quantification of how such overlayers affect yield and fracture during indentation in constrained film systems. To gain insight into such processes, electrical contact resistance was measured in situ during nanoindentation on constrained thin films of epitaxial Cr and polycrystalline Al, both possessing a native oxide overlayer. Measurements during loading of the films show both increases and decreases in current, which can then be used to distinguish between various sources of plasticity. Ex situ measurements of the oxide thickness are used to provide a starting point for elasticity simulations of stress in both systems. The results show that dislocation nucleation in the metal film can be differentiated from oxide fracture during indentation.

In the present work, proton conducting nanocomposite electrolytes containing poly(vinylphosphonic acid) (PVPA) and TiO2 have been prepared and characterized. In the nanocomposite materials, the TiO2 content was varied from 5% to 20% (w/w) to improve mechanical strength and stability. The thermal stability, proton conductivity, as well as morphology of the electrolytes were investigated. The interaction existed between PVPA and TiO2 was confirmed by Fourier transform infrared spectroscopy. Thermogravimetric analysis showed that the samples are thermally stable up to approximately 200 °C. Differential scanning calorimetry results indicate that the Tg of the materials shift to higher temperatures as TiO2 content increases. Scanning electron microscopy results confirmed that the TiO2 nanoparticles were successfully incorporated and homogeneously distributed in the PVPA matrix. In the anhydrous state, the proton conductivity of PVPA(10)TiO2(in situ) has been found to be 0.004 S/cm at 120 °C. The proton conductivity of these membranes are also measured and compared with previous studies.