An axial magnetic field of 0.1 T was applied to ZrF4–BaF2–LaF3–AlF3NaF fibers during heating to the glass crystallization temperature. Scanning electron microscopy and x-ray diffraction were used to identify crystal phases. It was shown that fibers exposed to the magnetic field did not crystallize, while fibers not exposed to the field did crystallize. A hypothesis based on magnetic work was proposed to explain the results, and was tested by measuring the magnetic susceptibilities of the glass and crystal.

Bi-doped sodium–potassium aluminosilicate glasses were synthesized and characterized. Broadband near-infrared (IR) emission covered the whole telecommunication wavelength region, with a maximum peak at about 1250 nm, a full width at half-maximum of about 370 nm, and a lifetime longer than 420 μs. The present glasses are potential materials for tunable lasers and optical amplifiers. The decrease of active Bi center concentration with the increase of Na2O content and the addition of CeO2are first reported here, and the IR emission center in sodium–potassium aluminosilicate glasses might be ascribed to low-valence-state bismuth, most probably, Bi+.

Out-of-phase boundaries (OPBs) are translation boundary defects characterized by a misregistry of a fraction of a unit cell dimension in neighboring regions of a crystal. Although rarely observed in the bulk, they are common in epitaxial films of complex crystals due to the physical constraint of the underlying substrate and a low degree of structural rearrangement during growth. OPBs can strongly affect properties, but no extensive studies of them are available. The morphology, structure, and nucleation mechanisms of OPBs in epitaxial films of layered complex oxides are presented with a review of published studies and new work. Morphological trends in two families of layered oxide phases are described. The atomic structure at OPBs is presented. OPBs may be introduced into a film during growth via the primary mechanisms that occur at film nucleation (steric, nucleation layer, a-bmisfit, and inclined-cmisfit) or after growth via the secondary nucleation mechanism (crystallographic shear in response to loss of a volatile component). Mechanism descriptions are accompanied by experimental examples. Alternative methods to the direct imaging of OPBs are also presented.

Novel slight yellow CeO2single/multiwall hollow microspheres were synthesized by the hydrothermal method without any surfactant and characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), field-emission scanning electron microscopy (FESEM), and x-ray photoelectron spectra (XPS). The results showed that the products were CeO2single/multiwall hollow microspheres, the shells of which were composed of CeO2nanoparticles with a mean size of 70 nm. The effect of the preparation conditions, the reaction temperature, the reaction time, and the molar ratios of urea to Ce(NO3)3·6H2O on the morphology of the products, was investigated. The optimal preparation conditions are determined as follows: the reaction temperature of 230 °C, the reaction time of 6 to 10 h, and the molar ratios of urea to Ce(NO3)3·6H2O of 3:1 to 6:1. The formation mechanism of CeO2single/multiwall hollow microspheres was proposed. The ultraviolet-visible (UV-VIS) diffuse reflectance spectra of the samples were measured. The results showed that the absorption edges of the samples were red-shifted compared with that of bulk CeO2, and that the red-shift of the absorption edges and the yellow of the samples enhanced with increasing the yield of CeO2single/multiwall hollow microspheres. The catalytic activity and the recycling performance of the sample on CO oxidation were tested and the T100%(the temperature at which CO 100% conversion) was 230 °C in the first run and decreased by 270 and 205 °C compared with that of bulk CeO2and CeO2nanocrystal, respectively.

In this work, we report on silver nanocubes with perfect shape prepared by a simple poly(vinyl pyrrolidone)-directed polyol synthesis process. The effects of poly(vinyl pyrrolidone)/AgNO3ratio Rand reaction temperature Ton the morphology and size of the products were investigated. Ag nanocubes with an average edge length of 230 nm were obtained successfully with sharp edges and corners under a precise synthesis condition of R= 1 and T= 150 °C. The optical properties of Ag nanocubes show an attractive plasma resonance red-shift with size in a wide spectra region. The growth mechanism of the Ag nanocubes is proposed to be thermodynamically and kinetically controlled.

Two TiO2layers formed in TiAl oxidation for 50 h at 900 °C were studied using scanning transmission electron microscopy. The main efforts were placed on the investigation of the distribution of niobium. It was found that Nb enriched in TiO2grains of mixture layer but did not exist in the outer TiO2layer. High-resolution electron microscopy (HREM) Z-contrast image revealed that Nb substitute for Ti site leading to Nb enrichment in TiO2grains of the mixture layer. The formation mechanism of the two TiO2layers and the potential effect of Nb doping in the mixture layer were also discussed.

In this paper, we report the results of a transmission electron microscopy investigation on WC–6 wt% ZrO2nanocomposite, spark plasma sintered at 1300 °C, for varying times of up to 20 min. The primary aim of this work was to understand the evolution of microstructure during such a sintering process. The investigation revealed the presence of nanocrystalline ZrO2particles (30–50 nm) entrapped within submicron WC grains. In addition, relatively coarser ZrO2(60–100 nm) particles were observed to be either attached to WC grain boundaries or located at WC triple grain junctions. The evidence of the presence of a small amount of W2C, supposed to have been formed due to sintering reaction between WC and ZrO2, is presented here. Detailed structural investigation indicated that ZrO2in the spark plasma sintered nanocomposite adopted an orthorhombic crystal structure, and the possible reasons for o-ZrO2formation are explained. The increase in kinetics of densification due to the addition of ZrO2is believed to be caused by the enhanced diffusion kinetics in the presence of nonstoichiometric nanocrystalline ZrO2.

Formation of intermetallic compounds (IMCs) at the interface between two metals during soldering processing exerts much influence on the electrical and mechanical performance of integrate circuits (ICs). Considering both of the thermodynamic and kinetic factors (including nucleation and growth) on phase formation, a new model capable of predicting phase formation sequence at the interface between two metals with different structures has been proposed in this work. Application of this new model on the interfacial reactions between pure elemental pairs of metals such as Ni/Sn, Cu/In, Cu/Sn, and Co/Sn at different temperatures shows good agreement between predictions by this model and experimental observations.

Experimental verifications have been performed on three engineering metals to verify recent methods proposed for extracting stress–strain curves from indentation tests. Their sensitivity to data errors is evaluated. Finally, the factors that might cause the inaccuracy and instability of the proposed methods are discussed, providing information that can be useful for further improving these methods.

Size-controlled nanocrystallites of Ni varying in size from 2 to 26 nm distributed in a nonmagnetic matrix of Ni(OH)2–ZrO2have been prepared by changing the reduction reaction time and by adding different concentrations of ZrOCl2solution to the initial reaction mixture. X-ray photoelectron spectroscopy indicates the presence of B2O3, Ni(OH)2, and ZrO2with Ni nanocrystals in the as-prepared composites. The room-temperature saturation magnetization and coercivity of the composites increases from ∼1.5 to 10 emu g−1and 100 to 200 Oe, respectively, when the ZrOCl2concentration in the reaction mixture increases to 0.10 M. The nanocrystals prepared without the addition of ZrOCl2exhibit a typical ferromagnetic response at 300 K, while that prepared with the addition of 0.10 M ZrOCl2shows a ferromagnetic response up to 400 K with higher saturation magnetization and coercivity.

In this paper, we report the first successful fabrication of dense and optically transparent cadmium tungstate (CWO) films by sol-gel processing and the study of their optical and x-ray scintillation properties. A new sol-gel processing method was developed using tungstic acid and cadmium nitrate as precursors and hydrogen peroxide as solvent; homogeneous and stable CWO sols were aged at room temperature and used for the preparation of CWO films. A rapid sintering process was investigated and found to be necessary to make dense and optically transparent nanocrystalline CWO films. CWO films were uniform, fully dense, and crack-free, with CWO as the only detectable crystalline phase, as determined by x-ray diffraction. The thickness, density, grain size, and crystallinity of CWO films are all found to be strongly dependent on the sintering conditions and in turn impact the optical and x-ray scintillation properties. Sol-gel-derived dense CWO films demonstrated intense photoluminescence and x-ray excited optical luminescence intensity. The relationships between sol-gel processing, nanostructures, and optical and x-ray scintillation properties are discussed in detail.

Raw and partially infiltrated carbon–carbon composite preforms have been scanned by high-resolution synchrotron radiation x-ray computerized microtomography. Three-dimensional high-quality images of the pore space have been produced at two distinct resolutions and have been used for the computation of transport properties: heat conductivity, binary gas diffusivities, Knudsen diffusivities, and viscous flow permeabilities. The computation procedures are based on a double change-of-scale strategy suited to the bimodal nature of pore space and on the local determination of transport anisotropy. Good agreement has been found between all calculated quantities and experimental data.

(100)-/(001)-oriented epitaxial Pb(Zr,Ti)O3(PZT) films with various Zr/(Zr + Ti) ratios and film thicknesses were grown on (100)cSrRuO3//(100)SrTiO3substrates at 600 °C by metalorganic chemical vapor deposition. Their crystal structure and microstructure consisting of particularly mixed phases with tetragonal and rhombohedral symmetries were investigated in detail. Films with the mixed phases with tetragonal and rhombohedral symmetries were ascertained at a Zr/(Zr + Ti) ratio of around 0.50 at a thickness of more than 200 nm from x-ray diffraction (XRD) analysis, while no mixed phase region was observed for 50 nm thick film. The relative volume fraction of the tetragonal cdomain decreased with increasing film thickness for 2-μm-thick films with mixed phases, while the tetragonal adomain and rhombohedral domain increased. These mixed phases were ascertained to have originated from the same cubic PZT grown above Curie temperature from results obtained by temperature-dependent high-resolution XRD reciprocal space mapping. The transmission electron microscopy images clearly revealed that the microstructure of the film gradually changed along the film thickness, despite the fact that the film was very uniform. Tetragonal phases were dominant in the bottom region (near the interface with the substrate) of the film, while rhombohedral phase was dominant in the upper region (near the surface), which was also ascertained by cross-sectional Raman analysis. In addition, the tetragonal a/cdomain was wider in the bottom region than that in the upper region of film with mixed phases. These data clearly demonstrate that both the crystal structure and microstructure changed along the film thickness.

A fluorescence switch by the photoisomerization of a photochromic compound in CH3CN and in a polymer film using a bistable photochromic (1,2-bis(2-methylbenzo[b]thiophen-3-yl) hexafluorocyclopentene) (BTF6) and a fluorescent 3-(2-benzothiazolyl)-7-(diethylamino) coumarin (coumarin6) was demonstrated. Because only the closed form of BTF6 serves as a fluorescence quencher of coumarin6, and the read (406 nm), write (254 nm), and erase (>500 nm) wavelengths are well-separated, a reversible modulation of the fluorescence of coumarin6 with high contrast and high sensitivity is expected to be realized. This system may represent an alternative to the fluorescence switches that are based on covalent systems in the potentially long-term optical data or image storage schemes utilizing luminescence intensity readout.

We present a systematic study of homogeneous deformation in a La-based bulk metallic glass and two in situ composites based on the same glass. In contrast to prior investigations, which focused on relatively dilute composites, in this work the reinforcement volume percentages were more concentrated at 37% and 52%—near or above the percolation threshold (35–40%). Hot uniaxial compressive testing was conducted over a wide strain rate range from 10−2to 10−5s−1at a temperature near the glass transition. For such concentrated composites, the homogeneous deformation behavior appeared to be dominated by the properties of the reinforcement phase; in the present case the La reinforcements deformed by glide-controlled creep. Post-deformation analysis suggested that bulk metallic glass matrix composites were susceptible to microstructural evolution, which appeared to be enhanced by deformation, in contrast with a stress-free anneal. Consequently, unreinforced bulk metallic glass appeared to be more structurally stable than its composites during deformation near the glass transition.

We report on ultrabroad infrared (IR) luminescences covering the 1000–1700-nm wavelength region, from Bi-doped 75GeO2–20RO–5Al2O3–1Bi2O3(R = Sr, Ca, and Mg) glasses. The full width at half-maximum of the IR luminescences excited at 980 nm increases (315 → 440 → 510 nm) with the change of alkaline earth metal (Mg2+→ Ca2+→ Sr2+). The fluorescence lifetime of the glass samples is 1725, 157, and 264 μs when R is Sr, Ca, and Mg, respectively. These materials may be promising candidates for broad-band fiber amplifiers and tunable laser resources.

Fundamental to investigating the coexistence of superconductivity and magnetic ordering in GdSr2RuCu2Oy(Gd1212) is the fabrication of macroscopic crystallographically oriented samples. To achieve this, we need to identify the conditions in which Gd1212 incongruent melting reaction, producing solid GdSr2RuO6(Gd1210) in Cu-rich liquid, dominates over decomposition due to RuO2sublimation. Only in these conditions is it possible, indeed, to grow oriented samples by any melting and resolidifying technique. Moreover, the optimal mixture of Gd1212 and its melting products has to be identified to perform melt-textured or flux-flow growth. By means of thermogravimetric and differential thermal analysis (TG–DTA) we analyzed, up to 1200 °C in air, several mixtures of Gd1212 with Gd1210 or CuO, performing a scan of the entire CuO–Gd1212–Gd1210 coexistence line of the Gd–Sr–Ru–Cu–O phase diagram. Gd1212 melting temperatures have shown a certain dependence on composition, decreasing about 30 °C for high Gd1210 content samples and about 20 °C for high CuO content samples with respect to pure Gd1212. A huge undercooling was observed for resolidification processes that were revealed to start at temperatures around 990 °C. Measurements proved that in this range of temperatures in air, no mass is lost at the end of each melting process, so that they are not affected by RuO2sublimation. A strong dependence on the atmosphere has also been observed for pure Gd1212, melting temperature decreasing by more than 80 °C from 100% O2atmosphere to He atmosphere (less than 10−2% O2). Measurements revealed that high O2partial pressures favor RuO2sublimation, whereas low oxygen atmospheres prevent resolidification.

The indentation behavior of polycrystalline copper at room temperature was investigated with a flat cylindrical indenter applied to fatigue-peak overloading. The experimental results showed that fatigue-peak overloading can retard the indentation depth (d) propagation rate. After the period of overloading, the dpropagation rate arrived at a new steady-state value again. The greater the amplitude of the peak overloading, the more the number of cycles that were needed to remove the effect of overloading. The observations of indentation cross-sectional microstructures revealed that the mechanism of dpropagation was the nucleation, formation, and propagation of cracks around the indentation. The experimental results and their interpretation implied that there were some similarities between the indentation fatigue-depth propagation and the conventional fatigue-crack propagation under fatigue-peak overloading.

Biomimetic coating of titanium and related alloys with carbonated apatitic calcium phosphate is an important area of research in implantology. While this paper specifically refers to coating Ti6Al4V, the results are valid with other related alloys as well. One step in the protocol involves an intermediate alkali treatment of Ti6Al4V to form a sodium titanate layer on the alloy surface. This pretreatment enhances the formation of the coating from simulated body fluid (SBF) solutions. Many papers in the biomimetic coating literature demonstrate the presence of cracks in coatings, irrespective of the SBF compositions and placement of the substrates. The presence of cracks may result in degradation and delamination of coatings. To the best of our knowledge, this issue remains unresolved. Therefore, the aim of this study was: (i) to examine and understand the reasons for cracking and (ii) based on the results, to develop a protocol for producing crack-free apatitic calcium phosphate coatings on Ti6Al4V substrates. In this study, the authors focused their attention on the alkali treatment procedure and the final drying step. It is hypothesized that these two steps of the process affect the crack formation the most. In the first case, the surfaces of alkali-treated substrates were examined with/without water-soaking treatment before immersing in SBF. This water treatment modifies the sodium titanate surface layer. In the second case, two different drying techniques (after soaking in SBF) were used. In one procedure, the coated substrates were dried rapidly, and in the other they were dried slowly. It was observed that the water treatment, irrespective of the drying method, provides a surface, which on subsequent soaking in SBF forms a crack-free apatitic calcium phosphate coating. Based on these results, the authors suggest a protocol incorporating a water-soaking treatment after the alkali treatment and prior to the SBF soaking treatment to obtain crack-free coatings.

The ability to create small-scale material patterns using lithography has been limited by the feature sizes and assembly of the master stamping system. Developing a simple and robust robotically automated patterning technique for both organic and inorganic materials, which is able to be actively controlled down to scales smaller than the operating features, would enable new capabilities and directions in research. Here, a novel method is presented to form patterns of defined shape and distribution via automated assembly along with force-controlled microstamping. Robotic assembly based particle templates and pyramid structures were used to create controlled distributions of materials. Systems including quantum dots and biomolecules were patterned, demonstrating our ability to create repeatable geometries with size scales smaller than the master stamping system. These patterns were also utilized for constraining cell adhesion and spreading. This work has potential applications in diverse areas from building molecular circuits to probing biological pattern formation.