Cadmium oxide, indium oxide and cadmium indate thin films obtained by the sol-gel technique

Thin films of the mixed CdO-In₂O₃ system were deposited on glass substrates by the sol-gel technique. The precursor solution was obtained starting from the mixture of two precursor solutions of CdO and In₂O₃ prepared separately at room temperature. The In atomic concentration percentages (X) in the precursor solution with respect to Cd (1 − X), were: 0, 16, 33, 50, 67, 84 and 100. The films were sintered at two different sintering temperatures (Ts) 450 and 550 °C, and after that, annealed in a 96:4 N₂/H₂ gas mixture at 350 °C. X-ray diffraction patterns showed three types of films, excluding those constituted only of CdO and In₂O₃ crystals: i) For X ≤ 50 at.%, the films were constituted of CdO + CdIn₂O₄ crystals, ii) For X = 67 at.%, the films were only formed of CdIn₂O₄ crystals and iii) For X = 84 at.% the films were constituted of In₂O₃ + CdIn₂O₄ crystals. In all films in the 0 < X < 100 range, the formation CdIn₂O₄ crystals of this material was prioritized with respect to the formation of CdO and In₂O₃ materials. All films showed high optical transmission and an increase of the direct band gap value from 2.4 (for CdO) to 3.6 eV (for In₂O₃), as the X value increases. The resistivity values obtained were in the interval of 8 × 10^− 4 Ω cm to 10⁶ Ω cm. The CdIn₂O₄ films had a resistivity value of 8 × 10^− 3 Ω cm and a band gap value of 3.3 eV.     

Substitution of Cu by Fe in the superconducting ceramic oxide EuBa2Cu3Oy: Structure, electrical conductivity, and microwave response

A series of EuBa₂(Cu_1–x Fe _x )₃O_y (0.0x0.15) ceramics were prepared and examined by thermogravimetric analysis, X-ray powder diffraction, electrical resistance measurements, and a magnetically modulated microwave absorption technique. The oxygen content (y=6.98±0.03), determined by thermogravimetric analysis in a reducing atmosphere, was independent of the iron concentration forx0.12. The introduction of iron into the EuBa₂Cu₃O _y lattice, via substitution into copper sites, effects a progressive decrease in the superconducting transition temperature with increasing iron concentration. Normal-state conductivity similarly progresses from a low resistivity and negative temperature coefficient behavior, to a semiconducting-like response at the high iron concentrations. X-ray powder diffraction measurements indicate that material containing 6% iron and above is tetragonal, yet it remains superconducting with up to at least 12% iron.     

Surface modification of the (Y,Gd)BO3:Eu phosphor by dual-coating of oxide nano-particles

The surface of (Y,Gd)BO₃:Eu³⁺ phosphor, red-emitting source in the plasma display panel (PDP), was dual-coated with SiO₂ and Al₂O₃ nano-particles. The surface modification of the phosphor was performed by a modified sol-gel method using the colloidal alumina and silica as surface coating precursors. We observed the oxide nano-particles on the surface of the single coated and the dual-coated phosphors and it was found that the luminance intensity was increased in the photoluminescence (PL) by a suppression of the nonradiative recombination via surface defects. The experimental results suggest that the surface modification of phosphors with nano-particles of the oxides leads to an increase in the luminance intensity of phosphors in the PDP (plasma display panel) and the gas discharge lamps.     

Facile synthesis of copper oxide nanotubes decorated by TiO2 nanoparticles,optical and photocatalytic activity in water

Copper oxide nanotubes decorated by TiO₂ nanoparticles (CNTNs) were fabricated by simple three-step method. First, deposition of copper onto cellulose fibres, then thermal oxidation of copper and cellulose fibres and last simply mixing copper oxide nanotubes and TiO₂ nanoparticles (NPs). Scanning electron microscopy, transmission electron microscopy and X-ray diffraction showed that the synthesised nanotubes were monoclinic-structured polycrystalline CuO with diameter and wall thickness of approximately 50～100 nm and 20～25 nm, respectively. Moreover, the diameter of the TiO₂ NPs is about 20～30 nm. Optical properties of the solutions containing copper oxide nanotubes decorated by TiO₂ NPs were studied. Discrete dipole approximation was used for the calculation of absorption, scattering and extinction cross sections of the deposited CNTNs on a glass substrate. Our simulation results show that there are good agreements between the experimental date and the simulation results. Moreover, the photocatalytic tests were done by methyl orange under visible light (λ = 633 nm) irradiation for prepared samples.     

Preparation of an Alkali-Element or Alkali-Earth-Element-Doped CeO2–Sm2O3 System and Its Operation Properties as the Electrolyte in Planar Solid Oxide Fuel Cells

Ceria–samaria (CeO₂–Sm₂O₃) is one of the most interesting fluorite oxides since its ionic conductivity is higher than that of yttria-stabilized zirconia in air. However, these CeO₂ -based oxides are partially reduced and develop electronic conductivity under fuel cell operating conditions. In their application to the SOFC system, their current densities and power densities are not at a satisfactory level. For the development of high-performance CeO₂ electrolytes, it is important that the fluorite lattice of CeO₂-based oxide be improved from the viewpoint of crystallography. In this study, it is assumed that the reduction of Ce⁴⁺ in the fluorite lattice was inhibited by expansion of the CeO₂ lattice. In order to investigate the contribution of the expanded CeO₂ lattice to reduction resistance, CeO₂–Sm₂O₃ solid solution, calcia-doped CeO₂–Sm₂O₃ solid solution, and a small amount of alkali element-doped CeO₂–Sm₂O₃ -based oxide were prepared for comparison. It was found that the calcia or a small amount of alkali element-doped CeO₂ solid solution enhanced the oxide ionic conductivity. The power density of the latter showed a high value at 800°C. It is concluded that the improved fuel cell performance can be attributed to the good reduction resistance in the fuel cell atmosphere.     

Nanostructured lipid carriers loaded with simvastatin: effect of PEG/glycerides on characterization,stability, cellular uptake efficiency and in vitro cytotoxicity

Objective: The aim of this study is to evaluate the use of PEG/glycerides of different HLB; oleoyl macrogol-6-glycerides (Labrafil^® M 1944 CS) and caprylocaproylmacrogol-8-glycerides (Labrasol^®), compared to Labrafac lipophile^® as PEG-free glyceride in the preparation of nanostructured lipid carriers (NLCs). PEG/glycerides are suggested to perform a dual function; as the oily component, and as the PEG-containing substrate required for producing the PEGylated carriers without physical or chemical synthesis.

Methods: Lipid nanocarriers were loaded with simvastatin (SV) as a promising anticancer drug. An optimization study of NLC fabrication variables was first conducted. The effect of lyophilization was investigated using cryoprotectants of various types and concentrations. The prepared NLCs were characterized in terms of particle size (PS), size distribution (PDI), zeta potential (ZP), drug entrapment, in vitro drug release, morphology and drug–excipient interactions. The influence of glycerides?±?PEG on the cytotoxicity of SV was evaluated on MCF-7 breast cancer cells, in addition to the cellular uptake of fluorescent blank NLCs.

Results: The alteration between different oil types had a significant impact on PS, ZP and drug release. Both sucrose and trehalose showed the lowest increase in PS and PDI of the reconstituted lyophilized NLCs. The in vitro cytotoxicity and cellular uptake studies indicated that SV showed the highest antitumor effect on MCF-7 cancer cells when loaded into Labrasol^® NLCs demonstrating a high cellular uptake as well.

Conclusion: The study confirms the applicability of PEG/glycerides in the development of NLCs. Encapsulating SV in Labrasol^®-containing NLC could enhance the antitumor effect of the drug.     

Structural transition induced by the release of residual stress in the complex of cubic and monoclinic Gd2O3:Eu nanoparticles

The Photoluminescence (PL) spectra of Gd₂O₃:Eu composed of cubic and monoclinic structure were collected on November 2003 and June 2006, respectively. The results show that a portion of cubic Gd₂O₃ transforms into monoclinic after the sample was left as it is for two years; and the ⁵D₁-⁷F_J emission of Eu³⁺ in cubic host was enhanced in this released complex. Considering the high pressure behavior of Gd₂O₃, we think this structural transition is due to the sample that endures a process of press and release while the residual stress is released slowly.     

Structure and property changes of ZrO2/Al2O3/ZrO2 laminate induced by low-temperature NH3 annealing applicable to metal-insulator-metal capacitor

Phase transformation and morphology evolution of ZrO₂/Al₂O₃/ZrO₂ laminate induced by the post-deposition NH₃ annealing at 480 °C were studied and the effect on the electrical property of the TiN/ZrO₂/Al₂O₃/ZrO₂/TiN capacitor module was evaluated in dynamic random access memory cell. Experimental results indicated N could indeed be incorporated into the dielectric laminate by the low-temperature NH₃ annealing, resulting in tetragonal-to-cubic phase transformation and small crystallites in the ZrO₂ layers. The C residue and Cl impurity in the ZrO₂/Al₂O₃/ZrO₂ laminate, which derived from the dielectric film formation and capping TiN layer deposition, respectively, could also be reduced by the nitridation process. As a result of the better surface morphology and less impurity content, lower dielectric leakage current and longer reliability lifetime were observed for the nitrided ZrO₂/Al₂O₃/ZrO₂ capacitor. This study demonstrates the low-temperature NH₃ annealing on ZrO₂/Al₂O₃/ZrO₂ dielectric can be applicable to the metal-insulator-metal capacitor structure with nitride-based electrode, which brings advantages over mass production-wise property improvements and extends the practical applicability of the ZrO₂/Al₂O₃/ZrO₂ dielectric.     

Speciation of Cr(III) and Cr(VI) in environmental samples determined by selective separation and preconcentration on silica gel chemically modified with niobium(V) oxide

In this study a new method for chromium speciation in water using solid phase extraction coupled to a flow injection system and flame atomic absorption spectrometry was developed. The adsorption behavior of Cr(III) and Cr(VI) on Nb2O5-SiO2 allowed the selective separation of Cr(III) from Cr(VI) in the pH range of 6-9. Thus, a method for Cr(III) preconcentration and extraction using Nb2O5-SiO2 was developed. Total chromium was determined after the reduction of Cr(VI) to Cr(III) using sodium sulfite in acidic medium. The operational variables of the preconcentration and reduction procedures were optimized through full factorial and Doehlert designs. The limit of detection for Cr(III) was 0.34microgL(-1) and the precision was below 4.6%. Results for recovery tests using different environmental samples were between 90 and 105%. Certified reference materials (NIST 1640 and NIST 1643e) were analyzed in order to check the accuracy of the proposed method, and the results were in agreement with the certified values.     

Growth,magnetic properties and the effect of cobalt addition in metal-organic chemical vapour deposited (MOCVD) gamma iron oxide thin films for magnetic recording applications

The present study aims at investigating MOCVD technique for the deposition of magnetic oxide thin films using volatile metal-organic compounds as source material. A three-step scheme has been described to form γ-Fe₂O₃ phase starting from α-Fe₂O₃ films as-deposited in optically heated atmospheric cold wall CVD reactor. Growth of γ-Fe₂O₃ in a two-step process has been performed by depositing Fe₃O₄ phase directly by resistively heated low-pressure CVD (LPCVD) technique. Role of substrate temperature in controlling the oxidation leading to direct formation of metastable γ-Fe₂O₃ phase (single-step scheme) by atmospheric CVD technique has been described. A new mode of introduction of cobalt in the film, namely heterogeneous dispersion of cobalt in the γ-Fe₂O₃ matrix, has also been described. Crystallographic structure, microstructure and magnetic properties of the films have been studied in detail. Biaxial vector coil and high-temperature magnetic studies were carried out for determining the nature of anisotropy in the γ-Fe₂O₃ film. Growth of γ-Fe₂O₃ films in different schemes have been discussed from the studies of growth kinetics in a cold-and hot-wall-type reactor chambers.     

Breakdown of the protective oxide on 11 % Cr steel at high temperature in the presence of water vapor and oxygen,the influence of chromium vaporization

Abstract

We report on the effect of water vapor and oxygen on the oxidation of a ferritic/martensitic 11 % Cr steel (CrMoV11 1). The influence of pH₂O, exposure time, gas velocity and temperature was investigated. The samples were exposed to dry O₂, O₂+10 or 40 % H₂O for up to 336 hours. Total pressure was 1 atm (1.02 × 10⁵ Pa). The gas velocity was between 0.05 and 10 cm/s while temperature was in the range 450–700°C. The samples are investigated by thermogravimetry, GI-XRD, SEM/EDX, GDOES, FIB and TEM/EDX. Oxidation is strongly affected by the vaporization of CrO₂(OH)₂ in H₂O/O₂ environment. The mechanism of vaporization of CrO₂(OH)₂ from a Cr₂O₃ surface is modelled by DFT calculations. In the absence of chromium vaporization the alloy forms a protective oxide consisting of a corundum-type solid solution (Fe_1–xCr_x)₂O₃. The vaporization of chromium tends to deplete the oxide in chromium. In some cases the oxide remains protective in spite of chromium depletion while in other cases there is a transition to breakaway oxidation. In the latter case a thick layered scale forms, consisting of an outer hematite part and an inner iron-chromium spinel. Oxidation behavior in an O₂+H₂O environment is to a large extent determined by the ability of the metallic substrate to supply the oxide with chromium by diffusion in order to compensate for the losses by vaporization. The corrosivity of the environment increases with the concentration of water vapor and oxygen, with the gas velocity and with temperature.     

Thermal conductivity of La2CuO4, La2NiO4, and Nd2CuO4 in the semiconducting and metallic phases

Thermal conductivity of polycrystalline La₂CuO₄, La₂NiO₄, and Nd₂CuO₄ was measured in the temperature range 300–1000 K. No anomaly in thermal conductivity has been observed during the semiconductor-to-metal transition of La₂NiO₄ or in the metallic phases of La₂CuO₄ and La₂NiO₄. A change of slope has been found, however, in the thermal conductivity of La₂CuO₄ at the crystallographic transition. The thermal conductivity of the oxides is mainly phononic in this temperature range.     

Spontaneous formation of Ge nanocrystals with the capping layer of Si3N4 by N2 implantation and rapid thermal annealing

We studied Ge nanocrystals (nc-Ge) formed by bombarding Ge(100) surface with N₂⁺ gas followed by rapid thermal annealing (RTA). After initial N₂⁺ implantation, near-edge x-ray absorption fine structure and x-ray photoelectron spectroscopy (XPS) data showed formation of molecule-like N₂ species and chemically metastable Ge nitrides (GeN_x). The RTA transformed these into hemispherical nc-Ge of 10-25 nm in the diameter as clearly seen in transmission electron microscope images. XPS confirmed that the surface of the nc-Ge was covered with Ge₃N₄ layer and underlying layer is also mostly likely Ge₃N₄. This simple process of forming isolated nc-Ge with Ge₃N₄ surrounding layer can be useful in non-volatile memory applications.     

DRIFT studies of thick film un-doped and Pd-doped SnO2 sensors: temperature changes effect and CO detection mechanism in the presence of water vapour

Diffuse reflectance infrared Fourier transform measurements were performed on tin oxide based thick film gas sensors operated in normal working conditions. We characterised SnO₂ sensors at different temperatures between room temperature and 300 °C. The results show the presence of different surface OH groups as well as coordinated water on the SnO₂ sensor surface. Their intensity changes with temperature. During the temperature cycles the bands’ peak positions are reversibly changed but their intensity is not. CO measurements were performed at 300 °C at different humidity levels (0 and 50% r.h.) on un-doped and Pd-doped sensors. In the presence of CO we observed in the spectra: a decrease of the OH groups on the SnO₂ surfaces, the appearance of gaseous CO₂ and CO in the pores of the sensitive layer and an increase of hydrated protons and of the free charge concentration. The effects are dramatically influenced by the water vapour concentration, temperature, dopands (Pd) and can be correlated with simultaneously performed sensor resistance measurements.     

Field, temperature, and angle dependence of the critical current density in Bi2Sr2CaCu2O10/Ag ribbons

Current-voltage characteristics of high-critical-current Bi₂Sr₂CaCu₂O₁₀/Ag ribbons were measured using both transport and magnetization techniques. The slope of these curves changes with magnetic field and temperature in a way very similar to the observedj _c (H, T) behavior. This correspondence between the critical current and the slope of theI–V characteristics can be explained within the thermally activated flux creep framework. The dependence ofj _c on the angle between field and ribbon is compared to the existing intrinsic anisotropy models.     

Evaluation of a method to reduce the redeposition of hydrogenated coatings containing carbon and tungsten in fusion reactors

The International Thermonuclear Experimental Reactor (ITER) project will be the first experimental fusion reactor with the objective to demonstrate the scientific and technological feasibility of fusion energy for commercial energy production. Erosion of materials by physical sputtering is the most fundamental of plasma-surface interactions in fusion reactor devices. Carbon and tungsten materials planned to be used in ITER divertor will be subjected to erosion, which produces local redeposition of mixed layers. Tritium retention in mixed materials is the major concern due to the limits imposed for safety reasons by nuclear licensing. The scavenging effect to reduce the redeposition phenomenon has been reported in low-pressure technical plasmas. In the present work, the minimization of co-deposits of hydrogenated C/W coatings by the injection of scavenger particles is analyzed.     

Probing the compositional, structural and morphological aspects of CdSe-TiO2 nanocomposites by surface-sensitive techniques

In this work, a colloidal suspension of trioctyl phosphine oxide/trioctyl phosphine (TOPO/TOP)-capped CdSe QD's of size ∼5 nm was prepared by chemical route and these QD's were anchored on the surface of sol-gel prepared nanoporous TiO₂ layers in THF-ethanol solvent either by direct adsorption or with the aid of bi-functional linker molecule mercaptoacetic acid (MPA). The particle size estimation of both TiO₂ and CdSe nanoparticles by X-ray diffraction (XRD) and transmission electron microscopic (TEM) measurements concur well with each other. Energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) studies elucidate the signatures of TiO₂, CdSe nanoparticles and linker which is also supported by the presence of contrasting images in TEM studies respectively. XPS depth-profiling measurements have been used as a probe to determine the chemical composition and structure of CdSe nanocrystals and CdSe-TiO₂ nanocomposites respectively. The CdSe nanoparticles and CdSe-TiO₂ nanocomposites formed by different routes are modeled, based on the observations of several complimentary techniques.     

Wetting induced by near-surface Ti-enrichment in the CaF2/In–Ti and CaF2/Cu–Ti systems

This paper is concerned with the wetting of CaF₂ by liquid Cu and In and with the effect of Ti additions to the melt. According to thermodynamic analysis and to the experimental observations, the significantly decreased contact angle following the addition of Ti to the molten metals is not due to the formation of interfacial fluoride phases, in contrast to previously reported results. Ab initio density functional calculations indicate that preferential Ti adsorption takes place at the near CaF₂ surface. It is suggested that the presence of a Ti-enriched liquid, adjacent to the substrate, gives rise, by means of heterogeneous nucleation, to the formation of a thin intermetallic compound layer that stands behind the experimentally observed enhanced wetting. The suggested wetting mechanism is supported by the notable correlation that has been observed between the temperature dependence of the contact angle and the temperature domains, associated with the presence of intermetallic compounds in both Me–Ti (Me = Cu, In) binary systems.     

超声场醇盐水解三氧化二锑颗粒的制备与表征

为减少协效阻燃剂中Sb_2O_3用量,降低其作为阻燃剂对材料性能的损伤.试验用SbCl_3通过超声场醇盐水解法制备Sb_2O_3粒子,探究阳离子和非离子表面活性剂对颗粒制备的粒径影响,再以正交试验考察氨水量、超声波处理时间及温度对Sb_2O_3颗粒生成时尺寸大小的影响,并得出最优制备工艺.通过扫描电子显微镜(SEM)、X射线衍射仪(XRD)对Sb_2O_3粒子微观结构进行了观察.结果表明:影响制备的试验条件为氨水与水体积比超声处理温度超声时间,且当氨水与水体积比为50∶0、超声处理20 min、45℃时,制得颗粒粒径为1.17μm;晶体类型为斜方晶型,结晶度高、晶粒度较大;在干燥时粒子进行了二次生长,大多数Sb_2O_3粒子呈长方体结构,轮廓尖锐,粒径0.5～2.0μm.为验证复合阻燃性,将其制备成介层多孔核-壳型Sb_2O_3@SiO_2阻燃颗粒,复合阻燃颗粒与聚合物基体相容性较好,颗粒分布均匀,材料阻燃效果明显.较于纳米型Sb_2O_3颗粒,复合颗粒表现出协同阻燃效果,并降低了软质塑料阻燃成本.     

On the effects of Ti,Zr and Ce substitution in YBa2Cu3O7−δ : transport,XRD, XPS and XANES studies

Results of the XRD, XPS, XANES, iodometric titration and transport studies on freshly prepared Ce, Zr and Ti substituted 1-2-3 samples are reported here. It is argued that at least 2% of Ce, Zr and Ti ions go into the 1-2-3 lattice. It is found that Zr, Ti ions exist in 4⁺ valence state, Ce is in predominantly 4⁺ (mixed valence) state and valence of Cu remains unaffected on substitution.