Near-stoichiometric (NS) (Mg:)Er:LiNbO3 crystals were grown from melts containing 0.0/0.5, 0.5/0.5, and 1.0/0.5 mol%/mol% MgO/Er2O3. Crystal composition and optical properties studies show that the Li2O contents in these crystals increase all by ∼1 mol% relative to the congruent point. The 1.0 mol% MgO-doped NS crystal is just near optical damage threshold and withstands a 488 nm light intensity >0.74 MW/cm2 without optical damage. Unpolarized absorption spectra of these NS crystals were measured, and the Er3+ absorption cross-section spectra were determined. The Er3+ spectroscopic properties were studied by Judd–Ofelt theory. The results show that as the crystal composition approaches the stoichiometry, the Er3+ spectroscopic properties change definitely. The Er3+ ion in the NS crystal has smaller absorption cross section and hence weaker oscillator strength, lower emission rate, and longer radiative lifetime. Nevertheless, the radiative quantum efficiency is retained. In addition, the MgO codoping has less effect on the Er3+ spectroscopic properties.

Y2Ba4CuNbO12 (Y-24Nb1) and silver (Ag) are recognized as potential candidates for improving both flux pinning and the mechanical properties of bulk rare earth (RE)–Ba–Cu–O [(RE)BCO] high-temperature superconductors (HTS). Recent attempts to add Ag2O to superconducting Y-123/Y2Ba4CuNbO12 composites, however, have produced a highly anisotropic morphology of Ag particles in samples grown by top-seeded melt growth (TSMG). This morphology has been attributed to strong particle pushing effects due to the presence of Y-24Nb1 nanoparticles in the composite microstructure. An investigation of the formation of anisotropic Ag particles in the YBCO bulk microstructure indicates that these pushing effects generate different morphological microstructural zones in the composite. These include a zone free of inclusions other than acicular Ag particles, a zone of segregated additives (i.e., Y-24Nb1, Y-211, and Ag), and a zone containing fine Ag and other particles distributed uniformly throughout the local microstructure. The particle pushing/trapping theory has been used to explain these extraordinary features of the distribution of Ag inclusions. The superconducting and mechanical properties of samples containing very fine silver inclusions are also discussed briefly.

This work first deals with the effect of Nb addition on the liquid phase separation in the Cu–Co system, which displays a metastable liquid miscibility gap. The isothermal sections at 800, 900, 1000, 1100, and 1200 °C in the Cu–Co–Nb system have been experimentally determined by optical microscopy, electron probe microanalysis, and x-ray diffraction on the equilibrated alloys, and the phase equilibria in the Cu–Co–Nb ternary system were thermodynamically assessed by using CALPHAD (Calculation of Phase Diagrams) method on the basis of the presently determined experimental data. Nb additions can stabilize the metastable liquid phase separation in the Cu–Co binary system and significantly increase its critical temperature. The solidified Cu–Co–Nb alloys appearing on the top-bottom separated microstructural morphology under low cooling rate while forming core-type macrostructural morphology under high cooling rate have been confirmed.

To investigate the effects of substituting Ag and Sb for Pb on the thermoelectric properties of PbTe, the electronic structures of PbTe and AgPb18SbTe20 were calculated by using the linearized augmented plane wave based on the density-functional theory of the first principles. By comparing the differences in the band structure, the partial density of states (PDOS), the scanning transmission microscope, and the electron density difference for PbTe and AgPb18SbTe20, we explained the reason from the aspect of electronic structures why the thermoelectric properties of AgPb18SbTe20 could be improved significantly. Our results suggest that the excellent thermoelectric properties of AgPb18SbTe20 should be attributed in part to the narrowing of its band gap, band structure anisotropy, the much extrema and large DOS near Fermi energy, as well as the large effective mass of electrons. Moreover, the complex bonding behaviors for which the strong bonds and the weak bonds are coexisted, and the electrovalence and covalence of Pb–Te bond are mixed should also play an important role in the enhancement of the thermoelectric properties of the AgPb18SbTe20.

We synthesized Ta3N5 by ammonolysis of Ta(OH)5. Ta(OH)5 was prepared by titration using TaCl5. The stirring speed and the amount of NH4OH to be added were important factors for controlling the particle size and formation of Ta(OH)5 during titration. During transformation of Ta(OH)5 to Ta3N5, the color changed from white to red. A small particle size and high level of formation of Ta(OH)5 improved nitridation, which was related to the color value. An x-ray diffractometer was used for phase identification. A scanning electron microscope was used to determine the microstructure, particle shape, and size. A colorimeter was used to obtain CIELab values. Ultraviolet–visible (UV–VIS) spectroscopy was carried out to determine the absorbance of colored powders. Thermogravimetry and a differential scanning calorimeter were used in air with a heating rate of 5 °C/min for thermal stability and behavior. An ON detector was used for detecting oxygen and nitrogen contents in Ta3N5.

An experimental study on the adhesion of thin films was conducted for the ultraviolet (UV)-cured SiOC films on Si substrate by examining the mechanical energy balance during the indentation process combined with atomic force microscopy observation. The effect of UV cure on the interfacial delamination toughness and the structure of the SiOC films are discussed. The energy release rate of the SiOC film/Si substrate interfacial delamination increases with the increases in the time of UV curing, indicating that the indentation method is efficient to examine the adhesion of coating. As the UV curing time increases, the film thickness and the Si–CH3 bond structure decrease, whereas the SiO2 network structure develops and the mechanical properties of the film are improved. Furthermore, the energy release rate of SiOC film/Si interfacial delamination is well correlated in a proportional manner to the Young's modulus of the film.

Tetrakis(diethylamino)phosphonium tetrafluoroborate (TDENPBF4), tetrakis(diethylamino)phosphonium hexafluorophosphate (TDENPPF6), and tetrakis(dimethylamino)phosphonium tetrafluoroborate (TDMNPBF4) in acetonitrile (AN) have been studied as electrical double-layer capacitor electrolytes in a two-electrode test cell using titanium carbide derived carbon, C(TiC), as an electrode material. Electrochemical characteristics for C(TiC)|1 M TDENPBF4 + AN, C(TiC)|1 M TDENPPF6 + AN, and C(TiC)|1 M TDMNPBF4 + AN interfaces have been obtained by cyclic voltammetry, constant current charging/discharging, and electrochemical impedance spectroscopy. High-capacitance (85 °F/g) and gravimetric power (269 kW/kg) have been achieved at cell voltage 3.2 V. Data obtained have been compared with results published previously.

This paper presents experimental and theoretical studies of the adhesion between the drug-eluting layer and a Parylene C primer layer in coatings present on a model drug-eluting stent. To quantify adhesion, Brazil nut sandwich specimens were prepared mimicking the layers of this coating. These samples were stressed to fracture, and the resulting initial cracks at the Parylene C/drug interface were used to measure the dependence of interfacial fracture energy of mode mixity. The mating fracture surfaces were then analyzed using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX). The interfacial energy release rates were obtained over a wide variety of mode mixities. Adhesion and fracture mechanics models were then used to estimate the mode mixity dependency of interfacial fracture toughness. Fracture toughness was found to be larger under higher mode mixity than that under lower mixity and the analytical model showed close agreement with experimental results.

A pulsed direct current (dc) reactive ion beam sputtering system has been used to synthesize highly c-axis oriented aluminum nitride (AlN) thin films on (0002)-oriented 200-nm thin titanium layers deposited on a Si-(111) substrate. After a systematic study of the processing variables, high-quality polycrystalline films with preferred c-axis orientation have been grown successfully on the Ti (0002) layer using an Al target under a N2/(N2 + Ar) ratio of 70%, a 2 mTorr processing pressure, and keeping the temperature of the substrate holder at ambient temperature (no substrate heating). The crystalline quality of the AlN and the underlaying Ti thin films was characterized by high-resolution x-ray diffraction. Best ω- full width at half maximum values of the (0002) reflection for 1-μm thin AlN layers are 0.56°. Hence, the AlN layers show a high degree of orientation in the (0002) direction, which directly translates into a high Q value piezoelectric response. Atomic force microscopy measurements were used to study the surface morphology of the Ti layer in an attempt to understand its impact on the quality of the AlN films deposited on top of them. Transmission electron microscopy cross-section analysis has been carried out to investigate the AlN/Ti interface. Our observations reveal the presence of crack-free layers with a smooth surface and extremely low defect density. Even local epitaxy phenomena have been identified at the AlN/Ti interface. The processing conditions used to synthesize AlN layers on Ti at room temperature are efficient in reducing the dislocation density and in-plane residual strain. Such AlN/Ti bilayers can be applied to manufacture novel electroacoustic device structures (such as bulk acoustic wave filters) on silicon substrates in further investigations.

The Ce-doped yttrium ortho- and pyrosilicate powders were prepared in a powder form by the formamide-modified sol-gel method. Crystal structure was checked by x-ray diffraction and sample morphology by transmission electron microscopy measurements. Both ortho- and pyrosilicate pure phases were obtained by the previously mentioned preparation procedure and proper annealing temperature was determined to obtain the maximum scintillation efficiency. Luminescence spectra and decays were measured to better evaluate the source of efficiency losses in the scintillator mechanism of samples heat-treated at lower temperatures. The potential of this preparation method for manufacturing the nanocomposite scintillators was discussed.

ZnO-ZnS-CdS heterostructure photocatalysts for water splitting were designed and prepared by a wet chemistry method. It was found that ZnO-ZnS-CdS heterostructures are highly active photocatalysts for H2 evolution under simulated solar light irradiation in an aqueous solution containing SO32- and S2- ions as sacrificial reagents. H2 evolution with (ZnO)2-(ZnS)1-(CdS)1 heterostructure reaches up to 2790 μmol h−1 g−1. The photoexcited electrons in the ZnO-ZnS-CdS heterostructures have a much longer lifetime (>225 ns) than that of the sole ZnO, ZnS, and CdS (<65 ns). The favorable interface processes of the heterostructures make a significant contribution to high photocatalytic H2 evolution rate.

Punched-out dislocations emitted from an octahedral oxide precipitate in single-crystal silicon were investigated using high-voltage electron microscopy and tomography (HVEM-tomography) to understand the mechanism of softening caused by the oxide precipitates. In the present paper, direct evidence of the transition of a punched-out prismatic dislocation loop to a slip dislocation is presented. The punched-out dislocation grows into a large matrix dislocation loop by absorption of interstitial atoms, which were produced during oxide precipitation.

The electronic structures of KMPO4 (M = Sr, Ba) were calculated by the density functional theory with the local-density approximation. The calculated result shows that KSrPO4 and KBaPO4 are direct-band gap materials with direct energy gaps of 4.52 and 4.35 eV, respectively. Meanwhile, by analyzing the valence band structures of KMPO4 (M = Sr, Ba), the strength of binding of valence band electrons of KBaPO4 is stronger than that of KSrPO4. In addition, the photoluminescence (PL) properties of the intense red-emitting phosphors KM1–xPO4:Eu3+x (M = Sr, Ba) were investigated. The PL emission spectra excited at 393 nm are dominated by the peak at 611 nm due to the forced electric dipole 5D0–7F2 transition of Eu3+ ions, which is attributed to low local symmetry sites occupied by Eu3+ ions in these hosts. And the optimum integrated intensities for KSr1–xPO4:Eu3+x and KBa1–xPO4:Eu3+x are 1.3 times and 1.1 times of that for commercial Y2O3:Eu3+, respectively.

We developed a new microscale technique for evaluating the local interface adhesion in a thin film stack and we compared it with a conventional four-point bending technique. Using the microscale technique, the interface adhesion was estimated to be 3.0 J/m2 by comparing experimental results with numerical simulation results for interface crack propagation behavior. The four-point bending technique was applied to the same interface and the interface adhesion was estimated to be 4.4 J/m2 by experiment. However, this value is an overestimate because it includes the plastic deformation of epoxy resin used to fabricate the specimens. By eliminating the additional energy dissipated through plastic deformation of the epoxy resin close to the interface crack tip, the interface adhesion was evaluated to be 3.3 J/m2. This value agrees well with that obtained using the microscale technique.

We report on the incorporation of molybdenum into tungsten oxide by co-sputtering and its effect on solar-powered photoelectrochemical (PEC) water splitting. Our study shows that Mo incorporation in the bulk of the film (WO3:Mo) results in poor PEC performance when compared with pure WO3, most likely due to defects that trap photo-generated charge carriers. However, when a WO3:Mo/WO3 bilayer electrode is used, a 20% increase of the photocurrent density at 1.6 V versus saturated calomel reference electrode is observed compared with pure WO3. Morphological and microstructural analysis of the WO3:Mo/WO3 bilayer structure reveals that it is formed by coherent growth of the WO3:Mo top layer on the WO3 bottom layer. This effect allows an optimization of the electronic surface structure of the electrode while maintaining good crystallographic properties in the bulk.

A solid state mechanochemical reaction (MCR) method for synthesizing AlN powder with aluminum and melamine powders as the reactants was proposed and put into practice. It was found that the solid state MCR between aluminum and melamine is an instantaneous and exothermic reaction. For a certain charge ratio, a critical ball milling time is needed for the MCR to occur. The higher the charge ratio, the faster the MCR. Cryogenic environments help to accelerate the MCR between Al and melamine. In addition to the direct one-step MCR synthesis approach mentioned above, AlN powder can also be synthesized by pre-ball-milling Al and melamine powders followed by heat treatment. Using this two-step approach, the heat treatment temperature is only about 638 °C, which is much lower than that used in other ways for synthesizing AlN powder. The lower heat treatment temperature can be attributed to the combined effect of both the adoption of melamine and the high reactivity of powders caused by ball milling. Comparatively, the present solid state MCR method for synthesizing AlN powder may be more cost-effective and hence more promising to be used to industrially produce both AlN powder and in situ AlNP reinforced aluminum matrix composites.

Emission properties of Er3+ in Ga2S3–GeS2–Sb2S3 glasses at the mid-infrared region were investigated from the viewpoint of their dependence on the concentration of the active ion and the glass composition. In the Judd–Ofelt analysis, no variation in omega parameters were observed when GeS2 was replaced by Ga2S3, while Ω2 increased as Sb2S3 was replaced by Ga2S3. This is due to the structural similarity and difference between the glass network units, GaS4 and GeS4 tetrahedra, and SbS3 pyramid. Clear mid-infrared emissions were observed at 2750 and 4300 nm assigned to the 4I11/2 → 4I13/2 and 4I9/2 → 4I11/2 transitions, respectively. The lifetime of the initial level of the 4.3 μm emission, 4I9/2, rapidly decreased with the Er3+ concentration because of the cross relaxation of this level, which can take place even at considerably low Er3+ concentration. The cross-relaxation processes were suppressed by the increase in the content of Ga2S3 because the solubility of Er3+ ions in the glasses increases with the Ga2S3 content.

Congruent Er:Mg:LiNbO3 crystals were grown by the Czochralski method from the melts containing fixed 0.5 mol% Er2O3 while varied MgO content ranged from 0.0 to 8.0 mol%. The Mg and Er contents in the crystals were determined by neutron activation analysis. In the presence of Er codopant, the Mg threshold concentration with respect to optical damage is determined from the measured OH absorption spectra. The results show that the Er codopant has less effect on both the Mg threshold concentration and Mg segregation coefficient, which is within 1.13–1.23 as the Mg concentration is below the threshold while within 0.88–0.98 when above the threshold, consistent with the only MgO doping case. On the other hand, the practical Er concentration in the crystal is closely related to the Mg content and shows definite Mg threshold effect. Below the threshold, the Er concentration decreases linearly with the increased Mg concentration in the crystal; above the threshold, the decrease is more remarkable and follows another linear function. The Mg concentration effect on the Er segregation coefficient is discussed from the viewpoint of the Mg doping effect on the solubility of Er ions in the crystal.

The effect of chemical treatment on the capacitance of carbon electrodes prepared from waste coffee grounds was investigated. Coffee grounds were impregnated with FeCl3 and MgCl2 and then treated at 900 °C. The resultant carbons were compared with activated coffee ground carbons prepared by ZnCl2 treatment. The carbon treatment processes of FeCl3 and MgCl2 were studied using thermal gravimetric analysis. Raman spectroscopy, x-ray photoelectron spectroscopy, and N2 and CO2 adsorption were used to characterize the activated carbons. Activation with ZnCl2 and FeCl3 produced carbons with higher surface areas (977 and 846 m2/g, respectively) than treatment with MgCl2 (123 m2/g). Electrochemical double-layer capacitances of the carbons were evaluated in 1 M H2SO4 using two-electrode cells. The system with FeCl3-treated carbon electrodes provided a specific cell capacitance of 57 F/g.

The distribution of alloying elements and the corresponding structural evolution of Mn–Sb alloys in magnetic field gradients were investigated in detail. It was found that a high magnetic field gradient could control the distribution of solute element in the alloys during the solidification process and therefore resulted in the coexistence of both primary MnSb and Sb phases or the aggregation of the primary MnSb with a continuous change in morphology. The positions where these primary phases located depended on the direction of field gradient. The control of the solute element distribution by a high magnetic field gradient was realized through the magnetic buoyancy force that could drive the migration of Mn element in the melt, originating from the difference in the magnetic susceptibility between Mn and Sb. The effectiveness of this control depends on the alloy composition, specimen dimension, cooling rate, and |BdB/dz| value.