Development of Multiferroism in PVDF with CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript> Nanoparticles

Thin films of some polymer-ceramic nanomultiferroic composites (in 0–3 connectivity) of compositions (1-x) PVDF-xCoFe₂O₄ (x?=?0.05, 0.1, 0.5) have been fabricated through a solution casting route. Based on X-ray diffraction pattern and data, basic crystal structure and unit cell parameters were obtained. The surface morphology of the materials was studied using a scanning electron microscopy (SEM) technique. Structural investigation confirms the presence of a polymeric electro-active β-phase of matrix (PVDF) and nano filler spinel phase of the incorporated nano-ceramics. The observed SEM micrographs confirm that the nanoparticles are well distributed in the PVDF matrix without any agglomeration with a lesser spherulitic microstructure. The flexible nano-composites fabricated with polymer (PVDF) and CoFe₂O₄ provide high permittivity (relative dielectric constant) and low loss tangent. An impedance spectroscopy (IS) technique was employed to study the effect of grain and grain boundary in the resistive properties of the composite materials in terms of electric circuit. The study of AC conductivity as a function of frequency follows Jonscher’s power law. The improved conductivity and dielectric, magnetic, and measured first-order magnetoelectric coefficients suggest some promising applications in the embedded capacitors as well as in multifunctional devices.     

Electrical conductivity of CuI-AsI<Subscript>3</Subscript>-As<Subscript>2</Subscript>Se<Subscript>3</Subscript> and CuI-SbI<Subscript>3</Subscript>-As<Subscript>2</Subscript>Se<Subscript>3</Subscript> chalcogenide films prepared by chemical deposition

The electrical conductivity of chalcogenide semiconductor films in the CuI-AsI₃-As₂Se₃ and CuI-SbI₃-As₂Se₃ systems, which have been prepared by chemical deposition from mono-n-butylamine, has been studied as a function of the temperature and film composition. It has been established that the electrical conductivity of the CuI-AsI₃-As₂Se₃ and CuI-SbI₃-As₂Se₃ films is predominantly determined by the copper iodide content. It has been demonstrated that the electrical properties of the chalcogenide glasses and the related films are characterized by the same values to within the experimental error, which is explained by the same model of dissolution of vitreous semiconductors in amines with the retention of the electrical properties of chalcogenide glasses after the deposition of films from their solutions.     

Synthetic spinels of the system MgO-Cr<Subscript>2</Subscript>O<Subscript>3</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>

Synthetic spinels of the system MgO-Cr₂O₃-Al₂O₃-Fe₂O₃ are considered and the desirability of organizing their production for the refractory industry is demonstrated. Translated from Novye Ogneupory, No. 6, pp. 32–35, June 2008.     

Examining the use of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles to enhance the NH<Subscript>3</Subscript> sensitivity of polypyrrole films

Summary Polypyrrole (PPy) composite films with different contents of Fe₃O₄ were prepared by in-situ polymerization of pyrrole in aqueous solutions. The dependence of dc current changes on the response of the samples exposure to NH₃ vapor has been investigated. The results shows the composite films are more stable than the pristine ones after being exposed to NH₃ vapor. Meanwhile, the response time was reduced with increasing the Fe₃O₄ content in the films. The results might be originated from the structural changes in the PPy films caused by the addition of Fe₃O₄.     

Structure of an atmospheric-pressure H<Subscript>2</Subscript>/O<Subscript>2</Subscript>/N<Subscript>2</Subscript> flame doped with iron pentacarbonyl

This paper presents the measurement and simulation data on the thermal and chemical structure of an atmospheric-pressure premixed H₂/O₂/N₂ flame doped with iron pentacarbonyl Fe(CO)₅. Soft ionization molecular beam mass spectrometry was used to measure concentration profiles of the combustion products of iron pentacarbonyl: Fe, FeO₂, FeOH, and Fe(OH)₂. A comparison of experimental and simulated concentration profiles showed that they are in satisfactory agreement for FeO₂ and Fe(OH)₂ and differ significantly for Fe and FeOH. Thus, the previously proposed kinetic model for the oxidation of iron pentacarbonyl was tested and it was shown that the mechanism needs further elaboration.     

Preparation of oxidized PbSeO<Subscript>3</Subscript> films from PbSe films

Lead selenide nanocrystalline films of a controlled thickness have been obtained using vacuum deposition onto substrates of C-29 glass, part of which were oxidized in a dry air atmosphere. The surfaces and cleavages of both initial and oxidized PbSe films are studied using scanning electron microscopy. The qualitative and quantitative estimation of the elemental content in the subsurface region of all studied films based on PbSe is investigated using X-ray microanalysis. The presence of lead selenide and lead selenite on the surface of the films under study is proven, and the principle possibility of forming PbSeO₃ films from PbSe films is shown.     

Photoactive WO<Subscript>3</Subscript> and Se-WO<Subscript>3</Subscript> thin films for photoelectrochemical oxidation of organic compounds

Thin films of bare and Se-containing tungsten trioxide (WO₃) on AISI304-type stainless steel were prepared by electrochemical deposition using peroxy-tungstate solutions. The obtained films were characterized by X-ray diffraction, photoelectron spectroscopy, scanning electron microscopy, thermal and photovoltammetry analyses. The oxidation of methylene blue, phenol, and methanol was used to evaluate the photoelectrocatalytic activity of the prepared films. It has been established that the incident photon-to-current efficiency (IPCE) in 0.1-M K₂SO₄ decreases as the concentration of methylene blue and phenol increases. On the contrary, the IPCE values increase with the increase in initial concentration of methanol. The bulk electrolysis experiments revealed that the prepared films are stable and can be used for photoelectrochemical oxidation of methanol.     

Scanning Probe Microscopy on heterogeneous CaCu<Subscript>3</Subscript>Ti<Subscript>4</Subscript>O<Subscript>12</Subscript> thin films

The conductive atomic force microscopy provided a local characterization of the dielectric heterogeneities in CaCu₃Ti₄O₁₂ (CCTO) thin films deposited by MOCVD on IrO₂ bottom electrode. In particular, both techniques have been employed to clarify the role of the inter- and sub-granular features in terms of conductive and insulating regions. The microstructure and the dielectric properties of CCTO thin films have been studied and the evidence of internal barriers in CCTO thin films has been provided. The role of internal barriers and the possible explanation for the extrinsic origin of the giant dielectric response in CCTO has been evaluated.     

Microstructure and properties of novel ReO<Subscript>2</Subscript> /polyimide nanocomposite films

A series of Rhenium (VII, Re⁷⁺) compound-doped polyimide (PI) nanohybrid films had been successfully fabricated from methyltrioxorhenium (MTO) and polyamic acid (PAA) via the solution direct-dispersing method, followed by a stepwise thermal imidization process. X-ray photoelectron spectroscopy (XPS) confirmed that MTO had decomposed into Re (IV) oxidation state (ReO₂). Field emission scanning electron microscopy (FE-SEM) showed that for the differrent hybrid films, the ReO₂ nanoparticles which formed by MTO decomposing well dispersed in polyimide matrix with a size of 40–60 nm. Thermal analysis indicated that the introduction of MTO decreased the thermal stability and the glass transition temperature (T_g) because of the unstable MTO. DMTA and static tensile measurements showed that the storage modulus and the elongation at break of nanocomposite films had a maximum value when the 1% of MTO was doped in PI, while the tensile strength decreased with increasing MTO content on the whole.     

Photoreduction of CO<Subscript>2</Subscript> into CH<Subscript>4</Subscript> using Bi<Subscript>2</Subscript>S<Subscript>3</Subscript>-TiO<Subscript>2</Subscript> double-layered dense films

Nano-sized bismuth sulfide (Bi₂S₃) and titanium dioxide (TiO₂) with the orthorhombic and anatase tetragonal structures, respectively, were synthesized for application as catalysts for the reduction of carbon dioxide (CO₂) to methane (CH₄). Four double-layered dense films were fabricated with different coating sequences—TiO₂ (bottom layer)/Bi₂S₃ (top layer), Bi₂S₃/TiO₂, TiO₂/Bi₂S₃: TiO₂ (1 : 1) mix, and Bi₂S₃: TiO₂ (1 : 1) mix/Bi₂S₃: TiO₂ (1 : 1) mix—and applied to the photoreduction of CO₂ to CH₄; the catalytic activity of the fabricated films was compared to that of the pure TiO₂/TiO₂ and Bi₂S₃/Bi₂S₃ doubled-layered films. The TiO₂/Bi₂S₃ double-layered film exhibited superior photocatalytic behavior, and higher CH₄ production was obtained with the TiO₂/Bi₂S₃ double-layered film than with the other films. A model of the mechanism underlying the enhanced photoactivity of the TiO₂/Bi₂S₃ double-layered film was proposed, and it was attributed in effective charge separation.     

Temperature programmed desorption of oxygen from Pd films interfaced with Y<Subscript>2</Subscript>O<Subscript>3</Subscript>-doped ZrO<Subscript>2</Subscript>

The origin of the effect of non-faradaic electrochemical modification of catalytic activity (NEMCA) or Electrochemical Promotion was investigated via temperature-programmed-desorption (TPD) of oxygen, from polycrystalline Pd films deposited on 8 mol%Y₂O₃–stabilized–ZrO₂ (YSZ), an O²⁻ conductor, under high-vacuum conditions and temperatures between 50 and 250 °C. Oxygen was adsorbed both via the gas phase and electrochemically, as O²⁻, via electrical current application between the Pd catalyst film and a Au counter electrode. Gaseous oxygen adsorption gives two adsorbed atomic oxygen species desorbing at about 300 °C (state β₁) and 340–500 °C (state β₂). The creation of the low temperature peak is favored at high exposure times (exposure >1 kL) and low adsorption temperatures (T_ads < 200 °C). The decrease of the open circuit potential (or catalyst work function) during the adsorption at high exposure times, indicates the formation of subsurface oxygen species which desorbs at higher temperatures (above 450 °C). The desorption peak of this subsurface oxygen is not clear due to the wide peaks of the TPD spectra. The TPD spectra after electrochemical O²⁻ pumping to the Pd catalyst film show two peaks (at 350 and 430 °C) corresponding to spillover O_ads and according to the reaction:

Uniform color coating of multilayered TiO<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> films by atomic layer deposition

Thin film optics, based on light interference characteristics, are attracting increasing interest because of their ability to enable a functional color coating for various applications in optical, electronic, and solar industries. Here, we report on the dependence of coloring characteristics on single-layer TiO₂ thicknesses and alternating TiO₂/Al₂O₃ multilayer structures prepared by atomic layer deposition (ALD) at a low growth temperature. The ALD TiO₂ and Al₂O₃ thin films were studied at a low growth temperature of 80°C. Then, the coloring features in the single-layer TiO₂ and alternating TiO₂/Al₂O₃ multilayers using both the ALD processes were experimentally examined on a TiN/cut stainless steel sheet. The Essential Macleod software was used to estimate and compare the color coating results. The simulation results revealed that five different colors of the single TiO₂ layers were shown experimentally, depending on the film thickness. For the purpose of highly uniform pink color coating, the film structures of TiO₂/Al₂O₃ multilayers were designed in advance. It was experimentally demonstrated that the evaluated colors corresponded well with the simulated color spectrum results, exhibiting a uniform pink color with wide incident angles ranging from 0° to 75°. This article advances practical applications requiring highly uniform color coatings of surfaces in a variety of optical coating areas with complex topographical structures.     

Gd<Superscript>3+</Superscript> doped Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles with proper magnetic and supercapacitive characteristics: A novel synthesis platform and characterization

A novel electrochemical procedure was developed for the facile preparation of Gd-doped iron oxide nanoparticles (GdIO-NPs). A simple galvanostatic deposition (i=10 mA cm^-2) was done in an additive-free aqueous solution containing FeCl₂·4H₂O, Fe(NO₃)₃·9H₂O and GdCl₃·6H₂O. The XRD, FE-SEM, EDS and TEM characterizations showed that the product is composed of 15% GdIO-NPs with 10 nm in size. VSM analysis proved that the GdIO-NPs are superparamagnetic. The cyclic voltammetry and charge-discharge tests showed that the prepared GdIO-NPs are capable to deliver specific capacity as high as 190.1 F g^-1 at 0.5A g^-1 and capacity retention of 95.1% after 2000 cycling. Based on the results, it was concluded that the developed electrochemical strategy acts as an efficient procedure for the preparation of lanthanide doped MNPs with proper magnetic and supercapacitive characters.     

EPR study of compounds in the LaAlO<Subscript>3</Subscript>-La<Subscript>0.67</Subscript>Sr<Subscript>0.33</Subscript>MnO<Subscript>3</Subscript> system

The EPR spectra of compounds in the LaAlO₃-La_0.67Sr_0.33Mn _y O₃ system at a frequency of 9.4 GHz have been investigated at the temperatures T = 77 and 300 K as a function of the manganese concentration y (y = 0.015, 0.030, 0.080). It has been revealed that, in the paramagnetic state at y = 0.015, there exist isolated Mn²⁺ and Mn⁴⁺ ions, which has been confirmed by simulating the EPR spectra. The parameters of the EPR spectra have been determined. The effective magnetic moments μ_eff of the Mn²⁺ and Mn⁴⁺ ions have been calculated from the EPR spectra. It has been demonstrated that an increase in the Mn concentration leads to a decrease in the number of isolated ions and to the formation of new spin clusters. This manifests itself in the predominance of a broad line with weak traces of the hyperfine structure due to the isolated manganese ions.     

Synthesis and properties of flux-cast refractories in the Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-MgO-B<Subscript>2</Subscript>O<Subscript>3</Subscript> system

Details are given of the synthesis and testing of flux-cast refractory materials in the alumina-rich region of the Al₂O₃-MgO-B₂O₃ system; XRD and petrography indicate that the main structure-forming phases are corundum and magnesian spinel. In subordinate amounts there are the boroaluminate 9Al₂O₃·2B₂O₃ and the previously unknown compound 4Al₂O₃·MgO·2B₂O₃, whose composition has been established by microprobe analysis. Corrosion tests showed that three-component systems containing magnesium and boron oxides at levels of 5–10% do not increase the corrosion resistance of refractories in molten sodium-calcium-silicate glass and electrovacuum borosilicate glass. __________ Translated from Novye Ogneupory, No. 3, pp. 161–163, March, 2008.     

Low-temperature anti-icing reagents in the Ca(NO<Subscript>3</Subscript>)<Subscript>2</Subscript>-Mg(NO<Subscript>3</Subscript>)<Subscript>2</Subscript>-CO(NH<Subscript>2</Subscript>)<Subscript>2</Subscript>-H<Subscript>2</Subscript>O system and their properties

The polytherms of ice melting in sections of the Ca(NO₃)₂-Mg(NO₃)₂-CO(NH₂)₂-H₂O system with different component ratios were studied in the temperature interval from 0 to −40°C. A series of nitrate and nitrate-carbonate reagents that are promising for the creation of anti-acing reagents were found, which form eutectics with ice at temperatures from −25 to −39°C. Their properties, viz., melting properties with respect to ice and corrosiveness on metals and alloys, were determined. An effective corrosion inhibitor was selected.     

Electrochemical studies on Sr doped LaMnO<Subscript>3</Subscript> and LaCoO<Subscript>3</Subscript> layers synthesised in a low-pressure plasma reactor equipped with a convergent nozzle

The aim of this work was to synthesise and deposit a perovskite (La_1-x Sr _x MnO₃ or La_1-x Sr _x CoO₃) cathode on an SOFC electrolyte (8% Yttria Stabilised Zirconia – YSZ). The recombination of atomic oxygen on Sr doped LaMnO₃ was performed in order to study the properties of perovskite for the adsorption of oxygen. The electrical resistance of the layers was measured as a function of the chemical composition. Impedance measurements on different samples were performed in order to analyse the electrochemical response of the cathode – electrolyte stack as a function of temperature and nature of the atmosphere. Moreover, the Faradaic impedance representing the electrochemical processes at the cathode – electrolyte interface was calculated from the global impedance in various conditions.     

Electrical conductivity of CuI-Cu<Subscript>2</Subscript>Se-As<Subscript>2</Subscript>Se<Subscript>3</Subscript> chalcogenide films prepared by chemical deposition

The electrical conductivity of CuI-Cu₂Se-As₂Se₃ chalcogenide semiconductor films prepared through the chemical deposition from an organic solvent has been investigated as a function of the temperature and composition of the films. It has been established that the electrical properties of the chalcogenide glasses and related films are characterized by the same values within the limits of the experimental error. This result is in agreement with the model of dissolution of vitreous semiconductors in organic bases (amines), according to which the main properties of bulk (cast) chalcogenide glasses are retained in films prepared from these glasses.