Considerable interest in understanding interfacial phenomena occurring across nanostructured solid oxide fuel cell (SOFC) membrane electrode assemblies has increased demand for in situ characterization techniques with higher resolution. We briefly outline recent advancements in atomic force microscopy (AFM) instrumentation and subsystems in realizing real time imaging at high temperatures and ambient pressures, and the use of these in situ, multi-stimuli probes in collecting local information related to physical and fundamental processes. Here we demonstrate direct probing of local surface potential gradients related to the ionic conductivity of yttria-stabilized zirconia (YSZ) within symmetric SOFCs under intermediate operating temperatures (500–600 °C) via variable temperature scanning surface potential microscopy (VT-SSPM). The conductivity values obtained at different temperatures are then used to estimate the activation energy. These locally collected conductivity and activation energy values are subsequently compared to macroscopic electrochemical impedance results and bulk literature values, thus supporting the validity of the approach.

Herein, we present a method for introducing β-cyclodextrin (β-CD) and Ferrocene (Fc) into the main chain of poly(acrylic acid) (PAA) to fabricate a novel supramolecular polymer, which was investigated by Fourier transform infrared spectroscopy and 1H Nuclear Magnetic Resonance (1H NMR). This polymer can self-assemble into interesting nanoparticles in aqueous solution. The redox-responsive Fc–CD host–guest interactions endow these nanoparticles with unique self-degradable and self-healable features under redox potential control. This redox behavior of the supramolecular polymer would open up an approach for redox-controlled biological materials with great application potential.

Double-filled high Fe content skutterudites, BaxYbyFe3CoSb12 (x + y = 1), were synthesized to investigate their high temperature transport properties. Both their phase and stoichiometry were characterized by powder x-ray diffraction and energy dispersive spectroscopy. The Seebeck coefficient, S, and electrical resistivity, ρ, increase with increasing temperature for all specimens over the entire measured temperature range. The thermal conductivity for the two low Ba content specimens decreases with increasing temperature up to 550 K at which point it increases with temperature due to bipolar diffusion. Bipolar diffusion becomes negligible with increasing Ba content. Due to this low bipolar diffusion, the ZT values of the higher Ba content specimens increase linearly with temperature, with the highest ZT value obtained for Ba0.9Yb0.1Fe3CoSb12.

Amorphous and nanocrystalline soft magnets have been investigated extensively in the past two decades. Many materials with attractive soft magnetic properties contain boron, which improves the glass formability, thermal stability and prevents undesirable grain growth. The high price of boron, however, makes the development of new soft magnetic materials and alternative synthesis routes important. We report here a synthesis of cobalt-rich alloys by substituting boron carbide for elemental boron to achieve significantly lower cost. Ribbons produced with and without boron carbide substitution were observed to exhibit comparable soft magnetic properties while the former results in 31–48% cost reduction. Extrapolating this idea to commercial VITROVAC 6025 and 6150, the cost reductions were calculated to be 56 and 50%, respectively, while both synthesis routes produced ribbons of similar soft magnetic properties. Our work here provides an attractive route to reduce the cost and increase the market competitiveness of soft magnets.

This study presents an analytical model of the reflectance of flat and textured silicon substrates. The model was used to study the reflection behavior of textured silicon surfaces under non-normal incidence. By characterizing the incident light and facets of the silicon wafer with vector geometry, dot products and Phong's reflection model (https://cs.oberlin.edu/∼bob/cs357.08/VectorGeometry/VectorGeometry.pdf) were used to determine the reflection angles between incident light rays and pyramidal facets. The possible optical interactions are considered for a wide range of pyramidal geometries and light incidence angles that are relevant to the exposure of textured silicon surfaces to incident sunlight. Furthermore, the model was used to investigate the possibility of secondary reflection, for the full range of incidence angles to the substrate. The textured silicon surfaces were found to reduce the reflection angles more effectively than flat substrates at lower angles of incidence. Secondary reflection was also found to be experienced or guaranteed, for all pyramid heights, when the angle of incidence to the substrate was less than 19.4°. The predictions are validated with experimental measurements of reflectance from (001)-textured silicon surfaces. The implications of the results are then discussed for the development of micropyramids for improved photoconversion in silicon solar cells.

In this work, the correlation between the number of nonbridging oxygen (NBO) atoms and the thermal and optical properties of TeO2–Li2O–MoO3 glasses was studied. Samples containing (100 − x)TeO2–x(Li2O–MoO3) with x = 10, 15, 20, and 25 mol% were investigated by Raman and Fourier transform infrared (FTIR) spectroscopies. From the optical absorption measurements, the band gap energies were determined. The Raman and FTIR results showed that with increasing x, the TeO4 units transform into TeO3+1 units and then into TeO3 units, while the Mo coordination changes from 4 → 6. This transformation corresponds to a decrease in the total number of NBO with increasing x in this glass matrix. The decrease in the NBO is also confirmed by the increase in band gap energies and the decrease in the optical basicity, indicating a more polymerized network with increasing x.

This work describes the effects of different atmospheres used during the thermal treatment of hematite films synthesized on transparent conductive substrates of fluorine-doped tin oxide by a newly reported wet chemical route assisted by microwave. The as-synthesized films were subjected to additional thermal treatment at 750 °C for 30 min in different gas flux (air, O2, and N2) to obtain a desirable phase and surface activation. A series of techniques were used to elucidate effects of each atmosphere used during the thermal treatment. The morphology of the films, as analyzed by top-view and cross-sectional scanning electron microscopy images, showed no significant changes and was composed of rods homogeneously distributed over the substrate, which covered the immersed area with a thickness between 98 and 100 nm. The photoelectrochemical response of the N2-hematite films was found to be 80 and 50% more efficient at 1.23 VRHE (reversible hydrogen electrode) than those of films produced in air and an O2 atmosphere. The photocurrent enhancement achieved by treatment in an oxygen-deficient atmosphere was attributed to the improvement of hematite catalytic activity, which produced a hematite–electrolyte interface favorable for water oxidation. Since an increase in the donor density by one order of magnitude was found for the N2-hematite films, a reduction of charge transfer resistance was expected in these films. However, the Nyquist plot analysis showed that the O2-hematite film had a lower charge transfer resistance. As a result, it is impossible to relate the photocurrent enhancement observed in N2-hematite film to electronic changes or vacancy formation, as previously reported in the literature. Indeed, by performing photoelectrochemical measurements in the presence of hole scavengers, it became clear that the major improvement caused by the oxygen-deficient atmosphere was in the catalytic activity efficiency of the hematite films for water oxidation. It was found that the oxygen-deficient atmosphere could improve the overall photoelectrochemical performance of the hematite by acting as a hole scavengers. This finding contrasts with a previous report, in which the use of an oxygen-deficient atmosphere during the phase transformation from akaganeite to hematite was found to enhance the photocurrent density by inducing an increased donor density caused by the formation of vacancies [Y. Ling et al., Angew. Chem., Int. Ed.51, 4074 (2012)].

A simple and efficient method for in situ preparation of highly stable polyimide (PI)-supported silver nanoparticles (AgNPs) was proposed. This process achieves excellent dispersion and high stability of AgNPs in the PI matrix. The formation of AgNPs in PI and the morphology evolution of PI/Ag nanocomposites were characterized by x-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy (FT-IR), and x-ray photoelectron spectra studies. The catalytic properties of these PI-supported AgNPs were investigated by monitoring the reduction of 4-nitrophenol by excess NaBH4 in water. The catalytic reaction was observed to have a pseudo first-order rate constant of 0.567 min−1 (9.45 × 10−3 s−1), which is comparable to other heterogeneous silver catalysts reported in the literature. Notably, the PI-supported AgNPs retained their relatively high catalytic activity over seven recycles with almost no leaching of catalytic species in the reaction solution. Moreover, the catalytic activity of the catalyst is still quite appreciable even after a six-month shelf-storage under room temperature.

Four epitaxial ScN(001) thin films were successfully deposited on MgO(001) substrates by dc reactive magnetron sputtering at 2, 5, 10, and 20 mTorr in an Ar/N2 ambient atmosphere at 650 °C. The microstructure of the resultant films was analyzed by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Electrical resistivity, electron mobility and concentration were measured using the room temperature Hall technique, and temperature dependent in-plain measurements of the thermoelectric properties of the ScN thin films were performed. The surface morphology and film crystallinity significantly degrade with increasing deposition pressure. The ScN thin film deposited at 20 mTorr exhibits the presence of <221> oriented secondary grains resulting in decreased electric properties and a low thermoelectric power factor of 0.5 W/mK2 at 800 K. The ScN thin films grown at 5 and 10 mTorr are single crystalline, yielding the power factor of approximately 2.5 W/mK2 at 800 K. The deposition performed at 2 mTorr produces the highest quality ScN thin film with the electron mobility of 98 cm2 V−1 s−1 and the power factor of 3.3 W/mK2 at 800 K.

Fluorine-doped tin oxide (FTO) thin films were deposited by spray pyrolysis in a pulse mode at 450 °C on glass substrates, using an alcoholic solution of SnCl4·5H2O and NH4F with different F/Sn ratios in the precursor solution. The film structure was nanocrystalline for all molar F/Sn ratios in the solution from 0 to 1.0. Postdeposition annealing treatments were not carried out. The films with a F/Sn = 0.35–1.0 ratio present a high grain orientation in the (200) crystallographic plane. A minimum sheet resistance of 4.5 Ω/sq, a resistivity of 2.2 × 10−4 Ω cm, a maximum electron mobility of 21.6 cm2/V s, and a carrier concentration of 1.7 × 1021 cm−3, corresponding to a strong degeneration of the electron gas in the conduction band, as well as a mean value of the transmittance of 0.84 in the visible spectral range, were obtained for the films fabricated with a F/Sn = 0.5 ratio. A high value of the figure of merit was obtained using two methods (38.8 × 10−3 Ω−1 and 5.75 Ω−1), that is, comparable with the highest values reported to date.

Single-walled carbon nanotube (SWNT) and conductive polymer composite were studied as a potential electrode candidate for plastic electronic devices such as organic light-emitting diodes (OLEDs) and solar cells. A novel conductive polymer, poly(2,7–9,9(di(oxy-2,5,8-trioxadecane))fluorene) (PFO), was synthesized and characterized as a surfactant to disperse SWNTs in solutions. The ethylene oxide (EO) side chain of rigid PFO backbone acts as a template to wrap around SWNTs in solution. Up to 0.02% (by weight) of SWNTs are stabilized and well separated in the solution phase. The carbon nanotube can be dispersed in solutions for over 4 mo. Transmission electron microscopy (TEM) images of solvent cast film suggest highly uniformed SWNT distribution incorporated in the conductive polymer matrix. Transmittance characterization shows the film is as transparent as indium tin oxide conducting glass. Conductivity measurement shows SWNTs can effectively inject charges into the PFO polymer matrix at low voltage. The current versus voltage profile of the SWNT/PFO composite film (2% SWNT in PFO by weight) shows that the majority current conducting is carried by SWNTs.

AlGaN-based quantum well (QW) heterostructures grown by plasma-assisted molecular beam epitaxy on c-Al2O3 substrates have been studied. The high-temperature (785 °C) synthesis of AlN buffer layer nucleated by a migration-enhanced epitaxy and including several ultrathin GaN interlayers was the optimum approach for lowering the threading dislocations density down to 108–109 cm−2. High-angle annular dark-field scanning transmission electron microscopy (HAADF STEM) has revealed the step-like roughness of the AlN/Al2O3 interface. Also, the formation of Al-rich barriers induced by temperature-modulated epitaxy and the spontaneous compositional disordering have been found in the AlxGa1−xN (x > 0.6) barrier layers. The origin of these phenomena and their influence on parameters of the mid-UV stimulated emission observed in the QW heterostructures were discussed. The fine structure of the QWs formed by a submonolayer digital alloying technique has been displayed by HAADF STEM, and optical properties of the QW structures were studied by temperature- and time-dependent photoluminescence spectroscopy.

The effect of interface tailoring by Cu coating carbon nanotubes (CNTs) on the properties of CNTs enhanced copper–tungsten (CNT/Cu–W) composites is investigated. Thermal, electrical, and mechanical properties were measured, and interfacial thermal resistance between Cu and CNT was calculated according to the thermal conductivity curves. CNTs with interface tailoring showed superior dispersion state in the Cu–W composites. When the CNT contents were lower than 0.5 vol%, homogeneous dispersion CNTs and strong interfacial bond between CNTs and Cu had a positive effect on the physical properties of CNT/Cu–W composites. Such interface modification can effectively achieve thermal and electrical conduction, as well as transfer load between CNTs and Cu in the CNT/Cu–W composites. When the CNT contents were higher than 0.5 wt%, the CNT agglomerations became the dominant factor to decrease the physical properties of the composites.

0.7(0.1BiYbO3-0.9PbTiO3)-0.3 Pb(Mg1/3Nb2/3)O3 (0.7BYPT-0.3PMN) ternary piezoelectric ceramics were prepared by a columbite precursor method. The effects of sintering temperature on the crystalline phase, microstructure, and electrical properties of the ceramics were systematically investigated. There were two phases coexisting in the 0.7BYPT-0.3PMN ceramics sintered at 1100–1250 °C, one is the perovskite host phase with tetragonal symmetry and the other is Yb2Ti2O7 impurity phase. It was observed that, with increasing sintering temperature, the piezoelectric constant d33, dielectric constant εr, planar electromechanical coupling coefficient kp, and Curie temperature TC increased initially and then decreased. An apparent structure distortion could also be observed in samples synthesized at high sintering temperature due to the severe volatilization of Pb and Bi. The optimum performances of the material were obtained for samples sintered at 1150 °C with d33 = 100 pC/N, εr = 494, kp = 25.4%, and TC = 380 °C, respectively. It can be ascribed to the combined effect of a higher density, structural homogeneity with decreased tetragonality as well as a small amount of pyrochlore phase.

In the present work, the Li2ZnTi3O8 ceramics were prepared via the solid-state reaction method, afterward annealed at 800 °C in a time variation from 4 to 20 h. The ordering, microstructures and dielectric properties were investigated using x-ray diffraction, scanning electron microscopy, network analyzer, and Raman spectroscopy. The most significant enhancement of quality factor is obtained in the sample annealed for 20 h, while the dielectric constant and temperature coefficient of resonant frequency change slightly. This result mainly attributes to the enhancement of ordering, which could be related to the increase in the Zn–O bond strength in ZnO4 tetrahedra. Meanwhile, the full-width at half-maximum of A1g mode decreased with higher annealing time, which suggested less variation in the Zn–O bond length and a higher degree of ordering. The best combination of microwave dielectric characteristic is obtained in the sample annealed at 800 °C for 20 h: Q × f = 112,400 GHz, εr = 24.500, and τf = −11 ppm/°C.

This study describes the nonlinear characteristics of SrCoO3-doped ZnO varistors and multilayer ceramic varistors (MLCVs) with copper electrodes, both of which are sintered in a reducing atmosphere. Due to postannealing effects in air or N2 with low-oxygen concentration (0.02%), bulk disks can be sintered in a reducing atmosphere, with a usable V1 mA/mm (e.g., 1600 V for bulk bodies or 1200 V for Cu cofiring) and highly nonlinear indices (α10 μA = V1 mA/V10 μA < 1.3), regardless of whether cofiring with Cu electrodes on disk surfaces was conducted or not. On the basis of this procedure, Cu-MLCVs were successfully produced, without oxidation of Cu-internal electrodes or structural defects. They exhibited high stability as well as a useful nonlinearity of V1 mA = 10.4 V and α10 μA = 1.93. The resultant stability against electrostatic discharge (ESD) satisfies the highest standard of level 4 in IEC61000-4-2 (ESD stability test). This is the first report to show that MLCVs with base metals have practical properties, including stability.

In this paper, a novel method is proposed to determine surface residual stress components and their directions based on the spherical indentation. To obtain the direction and the components of a uniaxial or biaxial residual stress, the relationship between the pile-up deformation around an indentation after unloading and the residual stress was firstly systematically studied and established by using numerical simulation. Through theoretical analysis and numerical simulation, we found that the position of the maximum residual stress is dependent on the maximum pile-up around an indentation after unloading. The direction and components of residual stress can be correctly determined by the unique relationship between pile-up after unloading and biaxial residual stress. This conclusion has been verified by the experiment results in the residual stress measurements of a welded specimen with spherical indentation and x-ray diffraction methods. Meanwhile, the influences of friction between the object surface and the indenter, the material hardening exponent of the specimen, and the elastic deformation upon the residual stress are discussed.

Compounds of poly(3-hydroxybutyrate) (PHB) and carbon black (CB) with CB content ranging between 0.5 and 10% were prepared in an internal mixer. The effect of heating and cooling rates on the crystallization and melting of PHB/CB compounds was investigated by differential scanning calorimetry (DSC), and its morphology analyzed by optical microscopy (OM). Results showed that PHB and its compounds partially crystallize from the melt during cooling and partially cold crystallize on reheating, with the amount of polymer crystallizing in each stage depending strongly on the cooling rate. Melting is usually shown in DSC scans as complex (double) peaks, which are influenced by the heating/reheating thermal cycles. The melting and cold crystallization temperatures, and the rates of phase change depend strongly on the cooling and heating rates and CB content. CB acts as a nucleating agent, promoting the melt and cold crystallization of PHB as well as increasing the number of spherulites, with a mild effect on the melting transition. Light microscopy images suggest that a secondary crystallization of PHB also occurs during storage at room temperature.

The development of synthetic scaffolds with a desirable combination of properties, such as bioactivity, the ability to locally deliver antibacterial agents and high osteogenic capacity, is a challenging but promising approach in bone tissue engineering. In this study, scaffolds of a borosilicate bioactive glass (composition: 6Na2O, 8K2O, 8MgO, 22CaO, 36B2O3, 18SiO2, 2P2O5; mol%) with controllable antibacterial activity were developed by doping the parent glass with varying amounts of Ag2O (0.05, 0.5, and 1.0 wt%). The addition of the Ag2O lowered the compressive strength and degradation of the bioactive glass scaffolds but it did not affect the formation of hydroxyapatite on the surface of the glass as determined by energy dispersive x-ray analysis, x-ray diffraction, and Fourier transform infrared analysis. The Ag2O-doped scaffolds showed a sustained release of Ag ions over more than 8 weeks in simulated body fluid and resistance against colonization by the bacterial strains Escherichia coli and Staphylococcus aureus. In vitro cell culture showed better adhesion, proliferation, and alkaline phosphatase activity of murine osteoblastic MC3T3-E1 cells on the Ag2O-doped bioactive glass scaffolds than on the undoped scaffolds. The results indicate that these Ag-doped borosilicate bioactive glass scaffolds may have potential in repairing bone coupled with providing a lower risk of bacterial infection.

A fast and nondestructive method for polarity determination of wurtzite GaN crystals based on x-ray photoelectron diffraction (XPD) has been demonstrated. Photoelectron emission from N 1s core level excited by Mg Kα source was found sufficient for the polarity determination of GaN crystals. XPD polar plots from polar GaN {0001} and semipolar GaN$\{ 10\bar 11\}$, $\left\{ {20\bar 21} \right\}$, $\left\{ {11\bar 22} \right\}$ crystals have been analyzed. Due to dominant electron forward scattering along N–Ga directions, photoelectron intensities either increase or decrease within a relatively narrow emission polar angle range. The slopes of polar plots are found noticeably different in the polar angle range of 20°–25° for (0001) or $\left( {000\bar 1} \right)$ crystals, respectively. The semipolar GaN substrates can be divided into two groups, depending on whether m-plane or a-plane is perpendicular to the semipolar surface. It was found that the slopes of the polar plots are different in the angular range of 20°–27° for semipolar GaN$\left\{ {10\bar 11} \right\}$, 10°–22° for GaN$\left\{ {20\bar 21} \right\}$ substrates, while for the GaN$\left\{ {11\bar 22} \right\}$ semipolar planes, the slopes are different in the range of 0°–15° with respect to the surface normal.