Kinetic studies of the electrochemical reaction between lithium and phthalocyanine II. Reduction reaction mechanism

The effects, during formation, of current density, charge capacity, and concentration and temperature of H₂SO₄ electrolyte on the capacity of tubular electrodes in lead/acid batteries have been studied. Electrode capacity was found to be maximum at a H₂SO₄ concentration of 1.05 sp. gr., a charge amount of 250% theoretical capacity, a current density of 0.44 A dm^?2, and an electrolyte temperature of 40 °C. A study of the soaking process for tubular electrodes showed the electrode capacity to be maximum when the acid absorption was about 170 mg of H₂SO₄ per g of oxide. Finally, the discharge overpotential of tubular electrodes was analyzed by a galvanostatic transient method.     

Structural and electrochemical modification of graphitic carbons by vapor-phase iodine-incorporation

Pristine and mechanically-milled graphitic carbons were chemically modified by vapor-phase iodine-incorporation. The effectiveness of iodine uptake during vapor iodation was gauged for pristine and mechanically-milled graphite. The doping of electronegative iodine, which is capable of triggering charge transfer reaction with carbon, was found to develop structural disordering, carbon-polyiodide covalent compounds (C-I₃, C-I₅), enhanced mesoporosity and reduced BET surface area in graphitic carbons. These intrinsic changes in iodine-modified graphite led to improved non-faradaic capacitance and development of faradaic pseudocapacitive reaction at ∼3.2 V versus Li. As a result, iodation develops manifold (∼100%) increment in gravimetric and volumetric capacity of precursor graphite, when tested versus Li. The effect of iodine-incorporation on physical and electrochemical properties of graphite is reported in detail.     

Anodic behaviour of copper electrodes containing arsenic or antimony as impurities

The anodic behaviour of three different copper electrodes in sulphuric acid medium was investigated using cyclic voltammetry in the potential range between the rest potentialE _i=0=–0.34 V and +0.80 V vs the Hg, Hg₂SO₄/K₂SO₄ saturated (MSE) reference electrode. Arsenic dissolved in the electrode matrix as well as oxygen dissolved in solution were found to delay passivation. The anodic peak current density was proportional to the square root of the potential sweep rate in two consecutive domains. An unusual break was observed for high scan rates (>50 m V s^–1) and was attributed to an increase of the medium viscosity because of the large gradient of concentration near the electrode surface. On the other hand, current oscillations, usually observed in the anodic processes of metallic electrodes, have been studied as a function of the electrode vertical/horizontal positions. Gravity has been found to affect both the frequency and the amplitude of the oscillations. X-ray diffraction measurements conducted on galvanostatically electrolyzed samples revealed, besides copper metal, the presence of copper sulfate pentahydrate and trihydrate for Cu–As and Cu–Sb, respectively. SEM analysis showed the existence of preferential domains of white product on a darker background of metallic copper or copper oxides.     

Synergistic effect of iodide ions and bark resin of Schinus molle for the corrosion inhibition of API5L X70 pipeline steel in H2SO4

The synergistic effect of bark resin of Schinus molle (BRSM) and iodide ions in 0.5 M sulfuric acid has been studied for the first time by potentiodynamic polarization and electrochemical impedance spectroscopy measurements; also, the surface morphology has been analyzed by scanning electron microscopy–energy-dispersive X-ray spectroscopic analysis in the present work. The results show that the BRSM and iodide ions have an evident synergistic inhibition effect in a 0.5-M sulfuric acid solution. The adsorption of the BRSM/iodide ion system follows the Langmuir adsorption isotherm and acts as a mixed-type inhibitor in sulfuric acid. The BRSM/iodide ion system is an effective inhibitor for API5L X70 pipeline steel in the 0.5-M sulfuric acid solution. The maximum percentage inhibition efficiency is equal to 99% at 1 g/L BRSM + 2 mM KI.     

Ambiguity attacks on SVD audio watermarking approach using chaotic encrypted images

In this paper, we study the robustness of the proposed watermarking algorithm by Al-Nuaimy et al. (Digit Signal Process 21(6):764–779 2011) for audio signals which is based on singular value decomposition (SVD). It has been concluded that it is fundamentally flawed in its design, in that it falls to two ambiguity attacks where the extracted watermark is not the embedded one but determined by the reference watermark. In the first attack, when a watermarked audio signal is rewatermarked by an attacker’s watermark, this one can be easily extracted to claim ownership of the original audio signal. In the second attack, during the extracting process when an attacker uses the singular vectors of his watermark, he can extract the attacker’s watermark. Therefore, he can claim ownership of the watermarked audio signal. The experimental results prove that the proposed attacks create a false positive detection in watermark extraction. Therefore, Al-Nuaimy et al. algorithm cannot be used for security systems, data hiding and copyright protection.

     

Hydric,morphological and thermo-physical characterization of glass wools: From macroscopic to microscopic approach

In this paper, experiments to investigate fibrous insulating materials used in buildings have been performed. Two kinds of glass fibers based products were studied. Scanning electron microscopy (SEM) coupled with an EDX detector, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and X-ray diffraction diagnostic method were used to assess materials properties. Through the coupling of thermal analyses with morphological and structural characterization techniques, a fast and safer comparison between the insulators becomes possible. So, after being tested at various rates of humidities, it is shown that the aim cause of ageing in the glass wools studied is mainly due to their binders. In fact, the alteration of glass constituting fibers comes much later. Besides, there is no preferential orientation for the vapor transfer inside glass wools.     

Crack formation and self-healing behavior during the drying of alumina gels: Experimental studies

The high shrinkage of alumina gels during the drying process leads to cracks. In this work, the behavior of four alumina gel formulations was experimentally studied following two drying procedures: (i) at ambient temperature and ambient humidity, outside a convective dryer and (ii) inside the dryer, allowing the application of different conditions of temperature and humidity. During the experiments, the observations in real time showed shrinkage of gels and the formation of cracks on them due to drying. Two of the gels displayed a capacity for self-healing, requiring numerical treatment of pictures to distinguish the closure of cracks due to shrinkage from those due to self-healing. The results show the precise determination of shrinkage steps, the estimation of the “shrinkage diffusivity” and proved that the manifestation of the chemical reaction is responsible for self-healing, activated by both applied temperature conditions and residual water of gels. Additional in situ investigations at microscopic scale using an environmental scanning electronic microscope corroborate the self-healing phenomenon noticed at macroscopic scale.     

Magnetic and electric properties of C-Co thin films prepared by vaccum arc technique

Cobalt doped carbon thin films have been deposited by a pulsed anodic electric arc technique. The films were characterized by high resolution transmission electron microscopy, electric measurements under dc magnetic fields, and ac magnetic susceptibility measurements within a temperature range 15-300 K. An insulating to a metallic state transition at a critical temperature around 60 K was observed.