Vanadium Doped Sol-Gel TiO2 Coatings

A study of the experimental conditions required to obtain vanadium doped sol-gel TiO2 coatings is presented. Tetraethyl orthotitanate was employed as the TiO2 source and VCl3, VOSO4 · H2O and VOSO4 dissolved H2SO4 where employed as vanadium sources.Dip coating has been used to produce coatings on silicon wafers, spectral carbon electrodes and titanium electrodes. Both supported and unsupported films have been studied by UV-Vis spectra, IR spectroscopy and X-ray diffraction (XRD). The measurements have been made on samples as prepared and treated thermally at temperatures between 100°C and 300°C. The thermal treatment temperatures have been established from DTA/TGA measurements.The vanadium doped sol-gel TiO2 coatings have been tested as sensors for redox potential measurements in electrochemical processes. The influence of both the thickness of films and the nature of substrate has been investigated.     

Atomic Force Microscopy Study of TiO2 Films Obtained by the Sol-Gel Method

Atomic Force Microscopy (AFM) was used to study the influence of thermal treatments on the structural and textural properties of the sol-gel TiO2 films obtained from Ti(OC3H7i)4. X-ray diffraction (XRD), ellipsometric and porosity measurements have also been made.The TiO2 sol-gel films were homogeneous, transparent and amorphous. Heat treatments in the 400–600°C range indicate that the films have a strong tendency to crystallization. The high initial homogeneity of the TiO2 films was preserved during the crystallization process. AFM shows that the thermally treated films exhibit uniform, monodispersed crystals.     

Sol–Gel SiO2-ZrO2 Coatings for Optical Applications

SiO₂-ZrO₂ based nanostructured multilayers films have been prepared by sol–gel processing from metallorganic precursors by low temperature inorganic polymerization reactions. Simultaneous gelation of both precursors was realized. Homogeneous and transparent films were obtained at room temperature by dip- and spin-coating on glass and silicon wafer substrates. Samples with successively deposited layers (1–3 layers) and successive thermal treatments have been also studied. Each deposited layer was thermally treated for 1 h at 300°C. The coatings were characterized by XRD, spectroellipsometry (SE), UV-VIS spectroscopy and AFM methods. The influence of substrates, number of coatings and number of thermal treatments on the optical and structural properties of the films was established. The thickness of three deposited SiO₂-ZrO₂ layers is about 496 nm on glass substrates and 413 nm on the silicon wafer substrate. The films deposited on glass are more porous than those deposited on silicon. The properties of optical waveguide prepared from SiO₂-ZrO₂ layers on silicon substrates will be discussed.     

Combined Experimental and Theoretical Insights into the Corrosion Inhibition Activity on Carbon Steel Iron of Phosphonic Acids

The inhibition effect of N,N′-phosphonomethylglycine (PMG) and vinyl phosphonic acid (VPA) on the 3% NaCl acidic solution corrosion of carbon steel iron was studied at different immersion times by potentiodynamic polarization, electrochemical impedance spectroscopy, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, and computational methods. It is found from the polarization studies that PMG and VPA behave as mixed-type inhibitors in NaCl. Values of charge transfer resistance (R_ct) and double layer capacitance (C_dl) in the absence and presence of inhibitors are determined. The PMG and VPA inhibitors were capable of inhibiting the corrosion process up to ≈91% and ≈85%, respectively. In the presence of PMG, the synergic effect of chlorine ions was observed. Density functional theory (DFT) was engaged to establish the adsorption site of PMG, VPA, and their deprotonated states. For studied compounds, the resulted values of E_LUMO, E_HOMO, energy gap (∆E), dipole moment (μ), electronic hardness (η), global softness (σ), electrophilic index (ω), and the electronic potential map are in concordance with the experimental data results regarding their corrosion inhibition behavior and adsorption on the metal surface.     

Linear and nonlinear relations between DSC parameters and elastic moduli for chemically and thermally treated human hair

Against the practical context of thermal straightening, hair samples were obtained with a chemical (bleaching) as well as a cumulative thermal history (0–800 s, 200 °C). On these samples, tensile testing and DSC analysis, both in the wet state, were conducted to obtain the elastic moduli E_w as well as denaturation temperatures T_D and enthalpies ΔH_D. 3D plots show overall linearity for the relationships between the parameters for natural hair. For bleached hair, pronounced nonlinearities develop beyond 300 s of thermal treatment. At this stage, T_D as well as E_w approaches limiting values, consistent with the state of a highly cross-linked, thermoset polymer. 2D projections are used to investigate the correlations between pairs of parameters. The results show that bleaching imparts a specific sensitivity for thermal damage, namely, to the matrix proteins, which more readily than the intermediate filaments (IF) turn into a thermoset. Overall, correlations between parameters hold well prior to the thermoset range. It is thus suggested that tensile testing to determine the elastic modulus and DSC come to consistent and equivalent results, at least, for the current experimental context. However, while E_w combines contributions of IFs and matrix, DSC differentiates the specific property changes of these components.

     

The solvent effect in obtaining of acid–base multicomponent systems: thermal,structural and luminescence study

Journal of Thermal Analysis and Calorimetry - Acid–base multicomponent systems based on active pharmaceutical ingredients 2-chloro-5-nitrobenzoic acid (2Cl5NBH) and monoethanolamine were...     

Role of Ag addition in L10 ordering of FePt-based nanocomposite magnets

The FePt system has important perspectives as high-temperature corrosion-resistant magnets. In the form of rapidly solidified melt-spun ribbons, FePt-based magnets may exhibit in certain cases a two-phase hard–soft magnetic behaviour. The present paper deals with a microstructural and magnetic study of FePtAgB alloys with increasing Ag content. The aim is to identify and confirm the effect of Ag addition in decreasing the temperature of the FePt disorder–order structural phase transformation. A detailed high-resolution transmission electron microscopy study is employed, and the alternative disposal of hard and soft regions within the two-phase microstructure is observed and interpreted with respect to the X-ray diffraction results. In the as-cast Ag-containing samples, it is shown that there is an optimum of the Ag content for which best magnetic properties are obtained. Ag addition creates a nonlinear behaviour of the coercive field and the ordering parameter, similar to the RKKY interaction-induced interlayer exchange coupling (IEC) observed in magnetic layers separated by non-magnetic spacer layers. Direct formation of the L1₀ phase from the as-cast state in the FePtAgB alloys is reported with magnetic parameters compatible to other exchange spring permanent nanomagnets. These findings open novel perspectives into utilization of such alloys in applications requiring magnets operating in high-temperature industrial environments.     

Influence of metal ions on oscillatory behavior of zinc anode in nitric acid-potassium dichromate media

A zinc anode in acidic media is a new oscillatory electrochemical system which manifests interesting behaviors, from steady states to simple oscillations and chaos. This paper presents an experimental study of the influence of metal ions on the shape, amplitude and duration of the cell potential oscillations, and gives a qualitative explanation of the system’s behavior. A small quantity of Cu²⁺, Zn²⁺ or Fe³⁺ ions added to the system change dramatically the potential oscillations from chaotic behavior to simple oscillations. The method may be used for chaos attenuation.     

Electronic Green's functions in a T-shaped multi-quantum dot system

We developed a set of equations to calculate the electronic Green's functions in a T-shaped multi-quantum dot system using the equation of motion method. We model the system using a generalized Anderson Hamiltonian which accounts for finite intradot on-site Coulomb interaction in all component dots as well as for the interdot electron tunneling between adjacent quantum dots. Our results are obtained within and beyond the Hartree–Fock approximation and provide a path to evaluate all the electronic correlations in the multi-quantum dot system in the Coulomb blockade regime. Both approximations provide information on the physical effects related to the finite intradot on-site Coulomb interaction. As a particular example for our generalized results, we considered the simplest T-shaped system consisting of two dots and proved that our approximation introduces important corrections in the detector and side dots Green's functions, and implicitly in the evaluation of the system's transport properties. The multi-quantum dot T-shaped setup may be of interest for the practical realization of qubit states in quantum dot systems.