Novel sol–gel synthesis of transparent and electrically bistable LiNbO<Subscript>3</Subscript>–SiO<Subscript>2</Subscript> nanocomposites thin films

The morphological and electrical characterization of transparent nanostructured LiNbO₃–SiO₂ thin films synthesized by a novel sol–gel route is reported. Films annealed at different temperatures exhibit different size of the nanocrystals, as demonstrated by Atomic Force Microscopy and Glancing Incidence X-ray diffraction. The dc electrical measurements performed on planar devices reveal electrical bistability. A clear relationship between the electrical bistability and the size of LiNbO₃ nanocrystals embedded in the matrix is observed.     

A novel technique to measure the surface electrical potential of polymer films by using dielectric spectroscopy

A novel method that allows the determination of the electrical potential of a polymer surface has been applied for polypropylene film treated by N₂ + H₂ cold plasma. The plasma treatment results in formation on the film surface of NH₂ groups, which then gets transformed to NH₃⁺ in contact with an electrolyte and leads to the formation of an electrical double layer. The method consists of theoretical calculation of electrical model potential, using the measurement of the electrical capacitance of the film in contact with an electrolyte by dielectric spectroscopy. Comparison with the results obtained by theoretical model shows similar dependencies of the electrical potential as a function of amino‐groups density and electrolyte concentration, but systematic differences of absolute values are observed. Copyright © 2005 John Wiley & Sons, Ltd.     

Effect of Lithium Sulfide on Electrical Properties of Li2S-LiPO3 Glasses

The temperature and concentration dependences of the electrical conductivity was studied in Li₂S-LiPO₃ glasses. The effect of lithium sulfide additions (22.5-25 mol %) to LiPO₃ on the electrical conductivity was studied. The nature of the conductivity was studied over the whole range of Li₂S concentrations using Tubandt's procedure, and the contribution of electronic component to the total electrical conductivity was examined by Liang-Wagner's polarization method.     

NTC陶瓷材料Co_(1.5)Mn_(1.5-X)Ni_XO_4中阳离子分布与导电性间的关系

本文通过溶胶-凝胶法制备三元系Co1.5Mn1.5-XNiXO4(X=0,0.1,0.3,0.5,0.7,1.0)NTC热敏电阻粉体材料,采用激光粒度分析、X射线衍射分析、红外光谱分析、电阻测量等手段,表征了煅烧材料的颗粒尺寸、烧结体的物相、红外吸收光谱以及陶瓷材料的电学特性。结合XRD、IR的分析结果,探讨了阳离子分布与热敏电阻电性能之间的关系,为解决热敏电阻材料高精度、高可靠性方面提供了依据。结果表明:随着Ni离子的增加,所得热敏材料的电阻率呈U型变化,材料常数B值从4427减小到2429K,该系列的电阻率、B25/50值调整范围较大,是一种具有实际应用价值的NTC热敏电阻。     

Preparation, morphology and properties of nano-sized Al2O3/polyimide hybrid films

Nano-sized Al₂O₃/polyimide (PI) hybrid films based on 4,4′-oxydianiline (ODA) and pyromellitic dianhydride (PMDA) were prepared by incorporation with different content of nano-sized Al₂O₃ via in situ polymerization. The TEM and SEM micrographs indicated that the Al₂O₃ particles were homogenously dispersed in the polyimide matrix by means of the ultrasonic treatment and the addition of coupling agent. The mechanical properties and thermal stability of the pure PI film can be improved by adequate addition of Al₂O₃. The PI hybrid film was strengthened and toughened simultaneously by the introduction of the well-dispersed Al₂O₃ particles. The PI hybrid films showed improved electrical aging performance as compared with pure PI film. Especially, the PI hybrid films with 10 wt.% of Al₂O₃ content exhibited obviously enhanced electrical aging performance with the time to failure of 3.4 times longer than that of pure PI film. The improved electrical aging performance of the hybrid film was attributed to the nano-sized Al₂O₃ particles highly dispersed in the hybrid film, which confirmed by the investigation of the morphology and the surface composition of PI hybrid film before and after electrical aging.     

Conducting polymers VIII: Optical and electrical conductivity of poly(bis-m-phenylenediaminosulphoxide)

Poly(bis-m-phenylenediaminosulphoxide) (PPDS) was prepared from Michael addition of N,N′-bis-sulphinyl-m-phenylenediamine and m-phenylenediamine. The prepared PPDS was then doped with iodine. PPDS was characterized by FTIR, ¹H-NMR, elemental microanalysis, thermogravimetric analysis (TGA), UV-visible absorption and fluorescence emission spectra. Thermal gravimetric analysis TGA showed that PPDS is thermally stable up to 179 °C. Electronic transitions showed main absorption peak at λ = 340 nm and two emission peaks at 460 and 490 nm. The behavior of both dc and ac electrical conductivities of PPDS were studied. The direct current electrical conductivity (σ_dc) and the alternating current electrical conductivity (σ_ac) were enhanced by the physical doping of I₂ in the polymer matrix. The conduction mechanisms for dc and ac electrical conductivities have been investigated.     

Preparation of some chitosan heavy metal complexes and study of its properties

The chitosan was prepared and mixed with some metal salts (FeCl₃, Co(OAc)₂ and NiCl₂) by different concentrations to form chitosan-metal complexes. The metal ions which strongly complexed to the amino groups of chitosan like Fe showed a smooth surface product, amorphous phase, thermally more stable and high electrical conductivity than other complexes, while the Co ions which the weakly complexed with chitosan showed a rough surface product, crystalline phase, thermally less stable and low electrical conductivity. The chitosan-metal complexes have a higher electrical conductivity than chitosan pure at room temperature.     

Characterization of CuInS2 Thin Films with Different Cu/In Ratio

Thin films of CuInS₂ were grown on glass substrate by successive ionic layer adsorption and reaction method with different [Cu]/[In] ratios and annealed at 400 °C for 30 min. The crystal structure and grain sizes of the thin films were characterized by X-ray diffraction method. Atomic force microscopy was used to determine surface morphology of the films. Optical and electrical properties of these films were investigated as a function of [Cu]/[In]ratios. The electrical resistivity of CuInS₂ of thin films was determined using a direct current-two probe method in the temperature range of 300—470 K. It is observed that, the electrical resistivity values show a big decreasing with increasing [Cu]/[In] ratio. Hence, the [Cu]/[In] ratio in the solution can drastically affect the structural, electrical, and optical properties of thin films of CuInS₂.     

A new method of coating powdered supportswith conductive carbon films

A series of conductive composite materials were obtained by polymerization of acrylonitrile in water suspensions of Al₂O₃ powder followed by further carbonization of the polymeric films covering the Al₂O₃ grains. The electrical conductivity and activation energy of the composites were measured in relation to the parameters used in preparation of the samples. This highly effective procedure can be used to improve electrical conductivity of the cathodes in lithium ion batteries.     

Proton dynamics in superionic phase of Tl3H(SO4)2

Electrical properties and ¹H-NMR absorption line have been measured, in order to investigate proton dynamics in a superionic phase in Tl₃H(SO₄)₂. From the measurement of the thermoelectric power, it is found that a majority carrier in electrical conductivity is a proton. Moreover, from ¹H-NMR measurement it is also found that the activation energy 0.33 eV of the hopping motion of protons is close to 0.38 eV as observed in the electrical conductivity measurement. These results indicate that the electrical conductivity in the superionic phase is caused by the hopping motion of protons accompanied by the breaking of the hydrogen bonds.     

Highly Conductive MXene Film Actuator Based on Moisture Gradients

MXene (Ti₃C₂T_x) is a new 2D material with both hydrophilicity and high electrical conductivity, and it has shown promise in smart electronic devices. Reported herein is a homogeneous MXene film actuator with high electrical conductivity triggered by moisture gradients. The actuator is highly sensitive to moisture and undergoes deformation, with the maximum bending angle as high as 155° at a relative humidity difference of 65 %. Several analysis methods show that the humidity drive and large deformation of the MXene film occur in situ by asymmetric expansion of the bilayer structure. The combination of deformation and electrical conductivity makes this film applicable to flexible excavators, electrical switches, and other fields, applications that are difficult to achieve directly by using other 2D materials. More importantly, this work further expands the new application range of MXene materials and provides new opportunities for building the next generation of high‐conductivity smart actuators.     

Effect of sintering temperature on the structural, optical and electrical properties of sol–gel derived indium oxide thin films

Sol gel derived indium oxide, In₂O₃; films were prepared by spin coating technique. The films were dried and sintered at different sintering temperatures (300, 400, 450 and 500 °C) in air. The effect of sintering temperature on the structural, optical and electrical properties of In₂O₃ thin films was studied. The morphology and structure of the films were analyzed by scanning electron microscope and X-ray diffraction. The films showed a bcc structure that changes its 400-preferential orientation to 222 orientation as the sintering temperature increases from 300 to 500 °C. The optical behavior of the films was studied by measuring the transmission spectra in the wavelength range 200–2,500 nm. Different optical models have been proposed for fitting the transmittance data and simulate the optical constants as well as the film thickness of In₂O₃ films. The best fitting of the data was obtained by combining the classical Drude and OJL models coupled with the Bruggeman effective medium approximation. The optical parameters of Drude model (plasma frequency and damping constant) are used calculate the electrical properties of the films. The calculated values of the electrical sheet resistance were compared with those measured experimentally by four probes. The correlation between the film orientation change and its optical and electrical properties was discussed.     

The compressive electrical field electrostrictive coefficient M33 of electroactive polymer composites and its saturation versus electrical field,polymer thickness,frequency, and fillers

Electroactive polymers are widely studied because of their large electrical‐field‐induced strain. Their flexibility and their ability to be deposited on large surfaces make them promising candidates as electroactive materials for actuators or energy‐harvesting devices. For actuation purposes, the material efficiency is directly related to the electrical‐field‐related electrostrictive coefficient M₃₃ through S₃₃ = M₃₃E², where S₃₃ is the electrical‐field‐induced strain and E is the applied electrical field. Numerous studies concern the increase of M₃₃, but very few have been devoted to its saturations versus electrical field. To this end, the present paper describes the variation of M₃₃ versus thickness, composition, frequency, and electrical field for polyurethane‐based composites. Based on the saturation of the electrical‐field‐induced polarization within the studied polymer composites, a model of the M₃₃ behavior was also proposed, and it was found to show a good agreement with the experimental data. In addition, this model predicts the dielectric constant and the saturation electrical field to be the key parameters ruling the M₃₃ saturation. Copyright © 2011 John Wiley & Sons, Ltd.     

Improvement of the thermoelectric properties of [Bi1.68Ca2O4−δ][CoO2]1.69 cobaltite by chimie douce methods

[Bi_1.68Ca₂O_4−δ]^RS[CoO₂]_1.69 has been obtained by different chimie douce methods and uniaxially or isostatically pressed. The influence of these parameters on the thermoelectric properties has been investigated. Contrary to the Seebeck coefficient, which remains unchanged, the electrical conductivity is greatly modified. In particular, spray-drying synthesis followed by uniaxial pressing results in an electrical conductivity two times larger than in the case of conventional solid state synthesis. Our results suggest that a narrow particle size distribution is beneficial to the thermoelectric properties of the layered compounds. The spray-drying technique seems to be promising to improve the electrical conductivity of layered materials. Moreover, this method presents other advantages (homogeneous samples and less energetic processing) which could be interesting to the future manufacturing of thermoelectric devices.     

Electric properties of ferromagnetic La1−XSrXCoO3 (0.5 ≦ X ≦ 0.9)

The electrical resistivity of ferromagnetic La_1?XSr_XCoO₃ (0.5 ≦ X ≦ 0.9) was measured in the temperature range from 77 to 300 K. All cobaltites are good conductors and have a metallic coefficient. The magnetic transitions are independent of the electrical conductivity in this system. The logarithm of the specific electrical resistivities (log ?) at 80 and 290 K monotonically increase with mole fraction of X, and these increases are explained by the itinerant-electron model.     

Structural characterization and electrical properties of NiNb2−xTaxO6 (0≤x≤2) and some Ti-substituted derivatives

A structural and electrical characterization of the system NiNb_2−xTa_xO₆ (0≤x≤2) is presented. For x≤0.25 materials with the columbite-type structure typical of NiNb₂O₆ have been obtained whereas for x≥1 tri-rutile-like oxides were obtained. The electrical properties are similar in both cases; they are semiconducting with very low electrical conductivity and very high activation energy, though slight differences were found as a function of Ta content. Improvement of conductivity by reducing the stoichiometric materials could not be achieved due to decomposition. In this connection, partial substitution of Nb or Ta by Ti has been carried out in order to create oxygen vacancies. Tantalum was partially replaced by Ti to a significant extent in the tri-rutile structure inducing a slight increasing of conductivity. However, for the columbite case neither Nb nor Ta could be partially replaced. This behavior is quite different from that reported for other similar columbites such as MnNb₂O_6−δ, which exhibits high electrical conductivity upon substitution of niobium by titanium.     

Electrochemical processes on the copper electrode in water-ethanol solutions of copper sulfate

The system Cu/H₂O-C₂H₅OH-CuSO₄ was studied in a wide range of organic component concentrations by the impedance spectroscopy method. In the studied range of ethanol concentrations the diffusion of ions to an electrode is the limiting stage of the electrode process. An increase in the ethanol concentration results in a decrease in the double electrical layer capacity, which is caused by a change in the double electrical layer structure at the electrode-solution boundary.     

The effect of platinum on the SnO<Subscript>2</Subscript> sorption properties

Chemisorption of SO₂ and O₂ at Pt-modified SnO₂ is studied by using the vacuum static method, with simultaneous recording of electrical conductivity, over the 22 to 300°C temperature range. The SnO₂ surface modification results in the increasing of SO₂ adsorption and weakening of the gas-surface bonding. The chemisorption enhances the samples’ electrical conductivity. The surface pretreatment with oxygen leads to the decreasing of the successive SO₂ chemisorption.     

Synthesis and oxygen permeation properties of 75 mol% Ce0.75Nd0.25O1.875–25 mol% Nd1.8Ce0.2CuO4 composite

An oxygen-permeable composite constituted to oxide ionic conductor phase (Ce_0.75Nd_0.25O_1.875) and oxide electronic conductor phase (Nd_1.8Ce_0.2CuO₄) was prepared using the acetate pyrolysis method. Based on electrical conductivity measurements, total electrical conductivity of 75 mol% Ce_0.75Nd_0.25O_1.875–25 mol% Nd_1.8Ce_0.2CuO₄ composite material was governed by the electronic conduction paths. With respect to the oxygen permeation properties, the results showed that oxygen permeation properties were unexplainable by a simple composite rule using the electrical transport properties of the bulk Ce_0.75Nd_0.25O_1.875 and the bulk Nd_1.8Ce_0.2CuO₄.     

Rapid quantitative analysis of fayalite and silica formed during decarburization of electrical steel

Subscales on surfaces are affected by the temperature and oxidation potential during decarburization annealing of electrical steel containing 3 wt% silicon. Knowledge of the structural and chemical properties of the surface oxide layer subscales permits the control of high‐temperature oxidation processes in the electrical steel. In the present work, the oxide layers were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectrometry, and glow discharge optical emission spectrometry (GD‐OES). The main oxide compounds formed within the subscales during decarburization annealing of the electrical steel were fayalite (Fe₂SiO₄) and silica (SiO₂). The fayalite and silica contents were quantitatively determined by wet analysis via the galvanostatic electrolysis method, and these oxide content measurements were compared with the fayalite content determined by FTIR spectrometry and the silica determined by GD‐OES. The results determined by rapid methods and wet analysis showed good agreement. The present findings show that FTIR spectrometry and GD‐OES measurements may be used for the rapid quantitative analysis of fayalite and silica in surface oxide layers during the manufacture of electrical steel. Copyright © 2011 John Wiley & Sons, Ltd.