Effect of surfactant and mineral additive on the efficiency of lead-acid battery positive active material

The effect of Sodium tripolyphosphate (STPP) and mineral additive on the performance of the lead-acid battery positive plate has been investigated. The addition of alumina-silicate to the positive paste and STPP to the electrolyte modifies the shape and size of PbO₂ crystals and improves the utilization of the positive active material (PAM). The electrochemical performance of the positive active material was determined using galvanostatic discharge and electrochemical impedance spectroscopy (EIS). The crystal structure and morphology of the PAM (PbO₂) were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The water content of the PAM was calculated using Thermogravimetric analysis (TGA) technique. The results showed that the addition of surfactant and mineral additive changes the morphology and the crystallite size of the PAM. We observe a remarkable improvement of the discharge capacity of the PAM when the surfactant (STPP) is added in the electrolyte. The discharge capacity increases with the decrease of the crystallite size and the charge transfer resistance R_ct of the PAM. This shows that the addition of mineral additive and the surfactant together improves the electrical performance of lead-acid battery.     

Nonisothermal crystallisation kinetics of amorphous selenium prepared by high-energy ball milling: A comparison with the melt-quenching and thin-film techniques

Differential scanning calorimetry (DSC) studies were performed under nonisothermal conditions at various heating rates for glassy Se made by high-energy ball milling. Comparisons were made between the ball-milling technique and the melt-quenching and thin-film techniques. Well-defined endothermic and exothermic peaks were observed at the glass-transition temperature, T_g, and the onset temperature of crystallisation, T_c. The isoconversional method of Vyazovkin was used to determine the variation in the activation energy for crystallisation with temperature, E_α(T). The value of E_α(T) was dependent on the sample preparation method. The thermal stability of the Se glasses was evaluated by calculation of the temperature difference (T_c ? T_g) and the S-parameter. In addition, the glass-forming ability was estimated by the criteria of reduced glass-transition temperature, T_rg, and the Hruby number, H_R. The structures of the Se samples that resulted from the DSC analysis were identified using an X-ray diffractometer. The glasses formed using the thin film technique were the most stable.     

A Comprehensive Study and Characterization of Colloidal Emeraldine-Base

Soluble emeraldine-base (PANI-EB) was prepared and its structure was characterized using ¹H, ¹³C and 2D (COSY, HMQC and HMBC) NMR. The solubility of the polymer in two solvents (N-methylpyrrolidone (NMP) and dimethyl sulfoxide (DMSO), the structure of the solution (aggregation) and the behavior of polyaniline were studied by viscometry and by dynamic light scattering (DLS) in dilute solution. Viscometric behavior in NMP and Huggins constant determination confirm supramolecular interactions also evidenced by DLS; at end, the molecular weight of the soluble fraction of PANI-EB is determined.     

Numerical modelling of twin helical spring under tensile loading

This paper presents a 3D geometric modelling of a twin helical spring and its finite element analysis to study the spring mechanical behaviour under tensile axial loading. The spiralled shape graphic design is achieved through the use of Computer Aided Design (CAD) tools, of which a finite element model is generated. Thus, a 3D 18-dof pentaedric elements are employed to discretise the complex “wired-shape” of the spring, allowing the analysis of the mechanical response of the twin spiralled helical spring under an axial load. The study provides a clear match between the evolution of the theoretical and the numerical tensile and compression normal stresses, being of sinusoidal behaviour. The overall equivalent stress isovalues increases radially from 0° to 180°, being maximal on the internal radial zone at the section 180°. On the other hand, the minimum stress level is located in the centre of the filament cross section.     

Photocatalytic activity of silicon nanowires under UV and visible light irradiation

The communication reports on the high performance of hydrogen-terminated silicon nanowires and silicon nanowires coated with metal (Ag, Cu) nanostructures for the photodegradation of rhodamine B under UV and visible light irradiation.     

Preparative three-dimensional GC and nuclear magnetic resonance for the isolation and identification of two sesquiterpene ethers from Dictyota Dichotoma

Separation science plays a crucial role in the isolation of novel compounds contained in complex matrices. Yet their rationale employment needs preliminary structure elucidation, which usually requires sufficient aliquots of grade substances to characterize the molecule by nuclear magnetic resonance experiments. In this study, two peculiar oxa-tricycloundecane ethers were isolated by means of preparative multidimensional gas chromatography from the brown alga species Dictyota dichotoma (Huds.) Lam., aiming to assign their 3D structures. Density functional theory simulations were carried out to select the correct configurational species matching the experimental NMR data (in terms of enantiomeric couples). In this case, the theoretical approach was crucial as the protonic signal overlap and spectral overcrowding were preventing any other unambiguous structural information. Just after the identification through the density functional theory data matching of the correct relative configuration it was possible to verify an enhanced self-consistency with the experimental data, confirming the stereochemistry. The results obtained further pave the way toward structure elucidation of highly asymmetric molecules, whose configuration cannot be inferred by other means or strategies.     

Modelisation of thermoelastic linear behaviour of tungsten filaments in simple and twin helical spring configurations

By trying to increase the luminosity or the life expectancy of an incandescent lamp, an idea consists of a series of successive rolling up of the tungsten filament. This gives geometrical configurations of filaments named simple, twin, or triple helical spring, etc… In this paper, we will limit only to the cases of the simple and twin helical spring filaments. Under the combined effects of the high temperature and the stresses induced by its own weight, the filament creeps by becoming plastically deformed in a permanent and a continuously manner, until the rupture. The theoretical study of the behaviour of these filaments needs the knowledge of internal efforts distribution, deformations modes, and their evolutions. The present work consists on an elastic structural analysis which must be the first step. Since the objective is also to study the influence of the filament self-weight solicitation, the orientation (or position) with respect to gravitational direction should be taken into account. Numerical results are obtained by finite element method. They showed a negligible influence of the solicitations due to the variation of the temperature with respect to those of the self-weight, and a relative sensitivity to the position changes for the twin helical spring filament. For this later, we have developed an analytical method which is only valid in the case of a vertical position. Because of some difficulties, the comparison between the numerical and analytical results could not be carried out directly. However, the analytical approach proved to be qualitatively useful for the analysis of numerical results.