We report the characterization of white light emitting devices fabricated using conjugated polymer blends. Blue emissive poly[9,9-bis(4′-n-octyloxyphenyl)fluorene-2,7-diyl-co-10-(2′-ethylhexyl)phenothiazine-3,7-diyl] [poly(BOPF-co-PTZ)] and red emissive poly(2-(2′-ethylhexyloxy)-5-methoxy-1,4-phenylenevinylene) (MEH-PPV) were used in the blends. The inefficient energy transfer between these blue and red light emitting polymers (previously deduced from the photoluminscence (PL) spectra of the blend films) enables the production of white light emission through control of the blend ratio. The PL and electroluminescence (EL) emission spectra of the blend systems were found to vary with the blend ratio. The EL devices were fabricated in the indium tin oxide [poly(3,4-ethylenedioxy-thiophene)-poly(styrenesulfonate)] (ITO/PEDOT-PSS)blend/LiF/Al configuration, and white light emission was obtained for one of the tested blend ratios.

The direct current (dc) conductivities and organic field-effect transistor (OFET) characteristics of a class of octa-substituted liquid crystalline (discotic mesophase) phthalocyanines (Pcs) are discussed. These molecules self-organize into columnar aggregates with large coherence lengths (up to approximately 300 nm). Langmuir–Blodgett films of these molecules were horizontally transferred to either interdigitated microelectrodes (IME) or OFET substrates, so that current flow could be measured either parallel or perpendicular to the column axis. Twenty-eight bilayer films of these Pcs on the IME substrates showed anisotropies in dc conductivity up to 50:1, whereas similar Pc films showed anisotropies in field effect mobilities of approximately 10:1, for a variety of W/L ratios (source/drain dimensions and spacing). Field-effect mobilities of 1 to 5 × 10-6 cm2·V-1·s-1 were determined from OFET measurements, along the Pc column axis, whereas charge mobilities measured from the space charge limited current regime on the IME substrates were in the range of 10-4 cm2·V-1·s-1. Conductive tip atomic force microscopy measurements on the apprximately 500-nm length scale showed that the conductivity anisotropy can be as high as 1000:1 when the Pc columns are intimately contacted to an adjacent Au bond pad.

Powders of TiO2 doped with a metal ion and N species were prepared by a polymerized complex method and the visible-light photocatalytic activities of the products are investigated. Of the metal ions studied (K+, Ca2+, Sr2+, Ba2+, Nb5+, Fe3+, Zn2+, and Al3+), the photocatalyst prepared with Sr2+ exhibits the highest activity for acetaldehyde decomposition under visible-light irradiation. Results obtained from x-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) analyses suggest that the doped N species reside at interstitial lattice positions in the catalyst. It was also found by XPS and ESR measurements that the doped N species combine with lattice oxygen to give rise to a paramagnetic property. The visible-light response of the catalyst is driven by the formation of paramagnetic N species at interstitial positions in the TiO2 lattice.

This paper analyses the influence of the inner structure of a SiO2 coating deposited on SiC particles by a sol-gel route on reactivity and wettability between SiC particles and molten aluminium during composite manufacturing. Different heat treatments were applied to the sol-gel coatings to change the porous structure of the amorphous silica. The coatings subjected to the mildest heat treatment were more reactive with molten aluminium, enriching the Si content of the matrix composite, and hence inhibiting direct reaction of the SiC particles and the formation of aluminium carbide. Thermal analysis showed that Si enrichment altered the solidification behavior of the aluminium matrix and its resultant microstructure, influencing the manufacturing conditions and final properties of the fabricated composites.

Epitaxial lanthanum zirconate (LZO) buffer layers have been grown by sol-gel processing on Ni–W substrates. We report on the application of these oxide films as seed and barrier layers in coated conductor fabrication as potentially simpler, lower cost coated-conductor architecture. The LZO films, about 80–100-nm thick, were found to have dense, crack-free surfaces with high surface crystallinity. Using 0.2-μm YBCO deposited by pulsed laser deposition, a critical current density of 2 MA/cm2 has been demonstrated on the LZO films (YBCO/LZO/Ni–W). Using 0.8-μm YBCO deposited using metal organic decomposition, a critical current density of 1.7 MA/cm2 and a critical current of 135 A/cm have been demonstrated on the LZO barrier layer with a sputtered CeO2 cap layer (YBCO/CeO2/LZO/Ni–W). These results offer promise to replace several of the vacuum-deposited layers in the typical coated conductor architecture (YBCO/CeO2/YSZ/Y2O3/Ni/Ni-W).

The microstructure of three kinds of porous carbon–carbon preforms prepared for carbon–carbon/aluminum composites was identified by x-ray diffraction, Raman spectroscopy, and field emission scan electronic microscope. Although manufactured at same processing conditions, including the temperature, type of organic gas, and pressure of pyrolysis, the structure of the pyrolytic carbon (Cpy) in three kinds of preforms is different. The morphology of the Cpy is influence by the topology of the preforms greatly, and the crystal structure of the Cpy is influenced by the crystal structure of the carbon fiber greatly, on which surface the Cpy was deposited. The degree of graphitization of the Cpy had been enhanced and the structure of the Cpy changed to more anisotropic form when the preforms were annealed at 2773 K.

Transmission electron microscopy (TEM) and analytic TEM were used to study the microstructure of amorphous carbon (a-C) films of thickness in the range of 5–100 nm deposited on Si(100) by radio-frequency (rf) sputtering. High-resolution cross-section TEM revealed a two-layer structure consisting of the a-C film and an ultrathin interface layer, in agreement with electron energy loss spectroscopy results. The presence of a 35-Å-thick interface layer (regardless of the deposition conditions) indicates that nucleation and initial growth of the a-C films were mainly controlled by the substrate surface condition. Mass-thickness contrast in bright-field TEM images showed an interface layer denser than the a-C film. This layer, believed to consist of Si, a-C, and SiC, enhances the adhesion of the film to the silicon substrate and accommodates the residual stress in the film. High-resolution cross-section TEM images revealed the presence of platelike nanocrystallites (∼35 Å in size) randomly distributed in the a-C film and oriented parallel to the surface. The possible mechanisms leading to the formation of these nanocrystalline structures are discussed in terms of sputtering phenomena occurring during film deposition.

Processes and preparation conditions for growing epitaxial thin films of Cu-based, layered oxychalcogenides LnCuOCh (Ln = La, Ce, Pr or Nd; Ch = S1-xSex or Se1-yTey) are reported. Epitaxial thin films on MgO (001) substrates were prepared by a reactive solid-phase epitaxy method. Four-axes high-resolution x-ray diffraction measurements revealed that the crystallographic orientation is (001)[110] LnCuOCh || (001)[110] MgO and the internal stress of the crystalline lattices in the films are relaxed during thermal-annealing process of the reactive solid-phase epitaxy. Furthermore, except for CeCuOS, systematic variations in the lattice constant by chalcogen or lanthanide ion substitutions were observed. These results demonstrated that the reactive solid-phase epitaxy is an efficient technique for fabricating LnCuOCh epitaxial films.

Both analysis and numerical calculations have been carried out to investigate the relationship between Young’s modulus and nonideally sharp indentation parameters. The results confirm that there exists an approximate one-to-one correspondence between the ratio of nominal hardness/reduced Young’s modulus (Hn/Er) and the ratio of elastic work/total work (We/W) for any definite bluntness ratio (Δh/hm) of a nonideally sharp indenter. Based on this relationship, the Young’s modulus of the indented material can be determined just from the values of Hn, We, and W, which are directly measurable quantities in an indentation test.

We propose a nucleation theory-based analysis for incipient plasticity during nanoindentation and predict the statistical distribution of rate-dependent pop-in events for many nominally identical indentations on the same surface. In the framework of stress-assisted, thermally activated defect nucleation, we quantitatively rationalize new nanoindentation measurements on 4H SiC and extract the activation volume of the nucleation events that mark the onset of plastic flow. We also illustrate how this statistical approach can differentiate between unique nucleation events for different indenter tip geometries.

Tellurium nanotubes and nanorods were synthesized by physical vapor deposition (PVD) in an induction furnace for reaction times between 25 and 35 min. The growth morphologies depended on the reaction times and the atmosphere in the induction furnace. Nanotubes grew only under argon atmosphere (1 mbar). Under vacuum, tellurium blades and nanorods were observed. Of particular interest are the dense carpets of nanorods observed on polycrystalline aluminum. PVD experiences in a conventional high vacuum coating system did not lead to the formation of nanotubes nor nanorods. The interesting electrical properties of tellurium and tellurium compounds combined with the observed growth morphologies are promising for the fabrication of nanoscale functional devices.

The formation enthalpies for alkali rare-earth compounds of the type K3RE(PO4)2 where RE = Sc, Y, Lu, Er, Ho, Dy, Gd, Nd, or Ce and for A3Lu(PO4)2 compounds with A = K, Rb, or Cs were determined using high-temperature oxide-melt solution calorimetry. Structural phase transitions were observed and characterized using differential scanning calorimetry and high-temperature x-ray diffraction. The formation enthalpy of the K3RE(PO4)2 phases from oxides becomes more exothermic with increasing rare-earth radius for the K3RE(PO4)2 series and with increasing alkali radius for the A3Lu(PO4)2 compounds. The K3RE(PO4)2 phases are stable with respect to anhydrous K3PO4 and REPO4. The monoclinic K3RE(PO4)2 compounds undergo a reversible phase transition to a hexagonal (glaserite-type) structure with a phase transition temperature that increases from −99 to 1197 °C with increasing RE ionic radius going from Lu to Ce.

Bimetallic NiW sulfide nanostructures of the inorganic fullerene-like (IF-like) type were prepared by a chemical method employing ammonium thiotungstate and nickel nitrate as metal-sulfide precursors followed by sulfidation in H2S/H2 at 400 °C. The nanostructures were grown with a Ni excess, at an atomic ratio R = 0.85 (R = Ni/Ni + W). The x-ray diffraction patterns showed poorly crystalline WS2, WO2, NiS, and Ni9S8 phases. High-resolution electron microscopy micrographs revealed the formation of two fullerene-like nanostructures, nickel sulfide nanoparticles and long nanotubes filled with tungsten suboxide, both coated by several WS2 layers. The surface area of 18 m2/g measured by nitrogen adsorption (BET surface-area) revealed that these materials contained micropororosity.

The extent of BiInO3 substitution in the perovskite system xBiInO3–(1 - x)PbTiO3 and the corresponding raise in the Curie temperature were investigated using thermal analysis, dielectric measurements, x-ray diffraction, and electron microscopy. Maximum tetragonal perovskite distortion (c/a = 1.082) was obtained for x = 0.20, with a corresponding Curie temperature of 582 °C. Phase-pure tetragonal perovskite was obtained for x ⩽ 0.25. Compound formation after calcining mixed oxide powders resulted in agglomerated cube-shaped tetragonal perovskite particles, which could be fired to 94.7% of theoretical density (TD). Sol-gel fabrication resulted in nano-sized tetragonal or pseudo-cubic perovskite particles, which after two-step firing, resulted in a tetragonal perovskite microstructure at as high as (x = 0.20) 98.1% of TD.

This article was originally published in [J. Mater. Res. 19, 1139 (2004)] and was incorrectly printed. The correct version appears below.