Seeding effects on the mechanochemical synthesis of 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3

A systematic investigation of the seeding effects on the mechanochemical synthesis of lead magnesium niobate – lead titanate 0.9Pb(Mg_1/3Nb_2/3)O₃–0.1PbTiO₃ (PMN–10PT), one of the most studied relaxor-ferroelectric material for electrocaloric applications, is reported. The perovskite crystallisation process was followed by X-ray diffraction using the Rietveld refinement method and transmission electron microscopy. Compared to the mixed-oxides case which requires 143 h of high-energy milling, the milling time needed to obtain a phase-pure PMN–10PT perovskite using PT seeds is reduced almost twice. The presence of PT seeds leads to faster transitions from the amorphous to pyrochlore and to perovskite phases compared to the mixed-oxides case. A sintering study demonstrates, for the first time, that a second, metastable, pyrochlore phase is taking part in the processes of perovskite formation. The PMN–10PT ceramic prepared from the PT-seeded powder exhibits electrocaloric properties comparable to reported values for PMN–10 PT prepared from oxides.     

Room temperature deposition of freestanding BaTiO3 films: temperature-induced irreversible structural and chemical relaxation

The room temperature aerosol deposition method is especially promising for the rapid deposition of ceramic thick films, making it interesting for functional components in energy, mobility, and telecommunications applications. Despite this, a number of challenges remain, such as an enhanced electrical conductivity and internal residual stresses in as-deposited films. In this work, a novel technique that integrates a sacrificial water-soluble buffer layer was used to fabricate freestanding ceramic thick films, which allows for direct observation of the film without influence of the substrate or prior thermal treatment. Here, the temperature-dependent chemical and structural relaxation phenomena in freestanding BaTiO₃ films were directly investigated by characterizing the thermal expansion properties and temperature-dependent crystal structure as a function of oxygen partial pressure, where a clear nonlinear, hysteretic contraction was observed during heating, which is understood to be influenced by lattice defects. As such, aliovalent doping and atmosphere-dependent annealing experiments were used to demonstrate the influence of local chemical redistribution and oxygen vacancies on the thermal expansion, leading to insight into the origin of the high room temperature conductivity of as-deposited films as well as greater insight into the influence of the induced chemical, structural, and microstructural changes in room temperature deposited functional ceramic thick films.

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Blends of thermoplastic polyurethane and polypropylene. II. Thermal and morphological behavior

Neat thermoplastic polyurethane (TPU), polypropylene (PP), and TPU/PP blends with different weight ratios that were prepared in a twin‐screw extruder were investigated with differential scanning calorimetry and light and scanning electron microscopy. The results confirmed PP matrix to TPU matrix phase inversion in the concentration region between 60/40 and 80/20 TPU/PP blends. The total degree of crystallinity of the blends and the crystallization temperature of PP decreased with increasing TPU content. On the other hand, the addition of elastomeric TPU to PP significantly increased the spherulite size of PP. The TPU melt islands in the PP matrix prolonged the crystallization of PP during solidification, and this enhanced the growth of spherulites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Enhancing the performance of exterior waterborne coatings for wood by inorganic nanosized UV absorbers

Enhancing the durability of the architectural wood coatings is essential for a successful commercialization of the forest products. Therefore, this paper is focused on UV resistant waterborne nanocomposites coatings for exterior uses of wood, which were improved with inorganic UV absorbers such as zinc oxide and titanium dioxide nanoparticles. The performance of such nanocomposites coatings applied on black spruce boards was demonstrated trough accelerated weathering. Artificial aging behavior of the coatings was followed by color, gloss and thickness changes. Scanning electron microscopy and transmission electron microscopy was used to investigate nanoparticles dispersion in nanocomposite dry films. Fourier Transform Infrared Spectroscopy was used to characterize the chemical modification of the weathered coatings surface. The results have shown significant improvement in UV-shielding of the nanocomposites coatings. Depending of aging criteria, a selection of the best nanocomposite coatings formulations for exterior wood could be done.     

Doubly functionalized multiwall carbon nanotubes with enhanced solubility

Doubly functionalized multiwall carbon nanotubes (MWCNTs) have been produced by oxidation in concentrated nitric acid and subsequent treatment with lauoroyl peroxide. MWCNTs containing both carboxyl and alkyl functional groups show enhanced solubility in a wide range of polar and nonpolar solvents and epoxy resin.     

ELISA and HPLC analysis of ochratoxin A in red wines of Croatia

Ochratoxin A (OTA) contaminates wine all round the world, and its consumption may significantly increase human exposure to this toxin. In this study, enzyme-linked immunosorbent assay (ELISA) and high-performance liquid chromatography (HPLC) for OTA analysis were tested on must and wine samples collected in Croatia. The results of ELISA and HPLC analysis of OTA in naturally contaminated red wines correlated well (r = 0.821), and the correlation was better at higher OTA concentrations. In contrast to HPLC, ELISA could not detect very low OTA concentrations. OTA concentrations in must (range 19–50 ng/l) were higher than in the wines (range 0–21 ng/l). No must samples showed the presence of Aspergillus carbonarius, which is a common OTA-producing mould affecting grapes.     

Polysulfone–polyaniline‐type membranes obtained in a steady‐state system: Structural and hydrodynamic characteristics

Structural and hydrodynamic characteristics of polysulfone–polyaniline‐type membranes (Psf‐PANI) are depending on a number of parameters. The present article details the influence upon such membrane of the characteristics of obtaining process, type of monomer used in generating the composite membrane and pH of the solution permeating the membranes (for flow characterization). Membranes were obtained in a steady‐state process, using an inversion phase technique accompanied by an in situ chemical reaction. The composite character of the material is a result of inserting, in the pre‐existing porous polymer structure (polysulfone, Psf) of a second monomer (aniline or substituted anilines, e.g., amino‐benzoic acid, 3ABA) through an oxidative polycondensation reaction. The steady‐state process ensures a constant and reproducible structure of the composite material. As the study shows, from the two types of obtained composite membranes, the one that uses aniline polycondensation on polysulfone substrate presents better performances, compared with the one that uses substituted aniline in polycondensation (Psf‐P3ABA). POLYM. ENG. SCI., 54:1640–1647, 2014. © 2013 Society of Plastics Engineers     

Phase relations and optoelectronic characteristics in the NdVO4–BiVO4 system

Studies performed on the NdVO₄–BiVO₄ system showed the existence of the Bi_xNd_1?xVO₄ homogeneity range for x ? 0.49(1). Extended X-ray absorption fine structure and X-ray diffraction analyses confirmed that Bi³⁺ is incorporated onto the Nd site in the NdVO₄ crystal structure with some distortion of the local structure. Surprisingly, the unit cell volume decreases with the increase in the content of the larger Bi³⁺ ion. On the other side of the NdVO₄–BiVO₄ system, Nd³⁺ does not enter the BiVO₄ structure but forms the NdVO₄-based secondary phase. Ultraviolet–visible spectroscopy showed that the band gap of NdVO₄ can be reduced to below 3.1 eV by the Bi doping. New emissions that do not exist for NdVO₄ have been found in the 650–675 nm range of Bi_xNd_1?xVO₄ photoluminescence spectra. The observed chemical and optoelectronic properties were explained on the basis of the hybridization of Bi 6s² and O 2p orbitals.     

Single phase induction machine simulation using the ElectromagneticTransients Program: theory and test cases

This paper investigates the transient phenomena of capacitor induction machines. Machine equations are evaluated using a digital algorithm according to Electromagnetic Transients Program (EMTP) Universal Machine (UM) modeling. The transformation equations provide a unique method which is suited for the special case configuration of a single phase induction machine. The simulation results are compared with a published analog computer simulation, as well as laboratory testing results. Good agreements using these approaches are observed. This verifies that EMTP is a valid simulation tool for single phase induction machine analysis. Also, an application of the simulation in choices of capacitor for single phase machinery is discussed