F. El-Taib Heakal
Cairo University
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Featured researches published by F. El-Taib Heakal.
Journal of Electroanalytical Chemistry | 1983
M. S. El-Basiouny; A.A. Mazhar; F. El-Taib Heakal; M. A. Ameer
Abstract The dissolution behaviour of anodic oxide films on Zr in H2SO4 was investigated as a function of acid concentration, formation voltage and temperature, using the results of impedance measurements. In general, the oxide dissolution was found to follow the empirical relation Cm−1=α−βt1/2. The dissolution process suffered a change in its rate as indicated by the change in the value of β. This behaviour indicated that the oxide was of a duplex nature in which the outer layer undergoes dissolution more freely than the inner one. The dissolution process was found to follow a zero-order mechanism.
Journal of The Electrochemical Society | 2008
F. El-Taib Heakal; A.M. Fekry
Two environmentally safe materials, uracil and adenine, were tested experimentally as inhibitors for the corrosion of 70Sn-Ag alloy in aggressive nitric acid solution by electrochemical techniques, as well as theoretically, by comparing some of their quantum chemical properties. Potentiodynamic measurements were used to calculate the corrosion rate in the absence and presence of the inhibitor. Results showed that uracil and adenine molecules can suppress both the cathodic and anodic processes of Sn-Ag alloy corrosion via their adsorption on the alloy surface according to the Langmuir adsorption isotherm. The apparent activation energy was found to increase with increasing inhibitor concentration, and it is always higher for adenine compared to uracil, suggesting that adenine is a more efficient inhibitor than uracil at comparable conditions. This is also corroborated by the values of the resistances for the charge transfer and the adsorbed layer, as well as some thermodynamic functions for adsorption, being all higher for adenine than uracil. The electronic properties of the two inhibitors, obtained using the incomplete neglect of differential overlap quantum chemical approach, were correlated with their experimental findings and support the conclusion that adenine is superior than uracil in inhibiting the acidic corrosion of Sn-Ag alloy.
Journal of Applied Electrochemistry | 1989
A. G. Gad Allah; A. A. Mazhar; F. El-Taib Heakal; M. A. Ameer
The open circuit behaviour of a mechanically polished zirconium electrode in NaOH solution revealed that the oxide building or dissolution process depended on NaOH concentration. Anodic oxide films formed at and below 30 V are fairly stable in NaOH solutions below 1 M. The oxide film is highly unstable, however, when immersed in NaOH at concentrations higher than 1 M. In such cases, oxide dissolution occurs preferentially over oxide building although its extent is much lower if compared with that occurring in acid medium. The results are in accord with the duplex nature of the oxide formed on zirconium.
Corrosion Science | 1987
F. El-Taib Heakal; A.S. Mogoda; A.A. Mazhar; M. S. El-Basiouny
Capacitance and potential measurements vs time show a two stage dissolution process in H3PO4 for the anodic oxide films formed galvanostatically on titanium. The dissolution mechanism of this duplex nature oxide film follows a zero order rate equation: the rate of film thinning, −d(1/Cm)/dt is independent of film thickness, which corresponds to 1/Cm. The oxide film formed at 15 V, which has a thickness larger than the others, is the most stable oxide film in H3PO4 solution and has the highest electrochemical insulating properties. The average rate constant for dissolution of the entire oxide film K (cm2 μF−1 min−1), is found to increase with increasing acid concentration. The effect of anion type of the formation medium on the value of K is also studied. In 0.1 N solutions of different inorganic acids K increases as the formation rate increases, and the order is H2SO4 (low) < HCl < HNO3 < HCLO4 < H3PO4 (high). The results indicate that the oxide film formed in H2SO4 is the most protective one with the lowest structural disorder.
Electrochimica Acta | 1975
A.A. Moussa; H.A. Ghaly; M.M. Abou-Romia; F. El-Taib Heakal
Abstract The differential capacitance of mercury in pure and coumarinated 1·0 N aqueous solutions of Na 2 SO 4 , H 2 SO 4 , KNO 3 , KCl, HCl, and KBr respectively was traced over appropriate potential range at 1 K Hz and 25°C. In Na 2 SO 4 and H 2 SO 4 , assumed not to exhibit specific anion adsorption, the results were most informative with respect to adsorption and orientation of coumarin. Relative coverages at saturation and the associated minimum capacitances could be correlated with molecular areas for planar and vertical orientations. The variation of the relative coverage θ with either potential or surface charge density at different coumarin concentrations displayed almost the same general features. The θ/concentration isotherms at constant potential, however, could be readily identified with pure planar, pure vertical or mixed adsorption and therefore were more informative. With the assumption that an adsorbed planar molecule displaces four water molecules and a vertical one two molecules, the pure isotherms were shown to fit reasonably the Flory—Huggins isotherm. A modification of this isotherm explained only qualitatively the mixed isotherms in absence of specific anion adsorption, while the results were far less convincing in the presence of specific anion adsorption.
Thin Solid Films | 1992
A.S. Mogoda; F. El-Taib Heakal; A.A. Ghoneim
Abstract The galvanostatic anodization of zirconium in phosphoric acid was studied. The results show that the rate of formation of the anodic oxide film on zirconium increases with increasing current density and acid concentration. The currentless dissolution of the oxide film in H3PO4 solutions was investigated using capacitance and potential measurements. The influence of the formation voltage, acid concentration and temperature on the dissolution rate of the oxide film was also studied. The dissolution behaviour of the oxide film in H3PO4 shows a two-stage dissolution process that seems to be related to the duplex nature of the oxide film; the outer layer is more susceptible to dissolution than the inner layer. The dissolution of the oxide film follows a zero-order rate equation. The average rate constant for dissolution of the entire oxide film K was found to increasing formation voltage and acid concentration. Also, an increase in temperature of the dissolving medium enhances the dissolution rate of the oxide film. The activation energy was found to be 37.4 kJ mol−1.
Electrochimica Acta | 1970
A.A. Moussa; M.M. Abou Romia; F. El-Taib Heakal
Abstract Reactivity towards electron transfer of the chloride, azide and bromide ions at 1 M concentration during reduction of Zn 2+ , Cd 2+ , Pb 2+ and In 3+ at the dme has been examined with faradaic impedance measurements. Well-defined pseudocapacitances indicating reversible or quasi-reversible reduction in the three media could be traced. By vector analysis of the faradaic impedance following the simple model, consistent apparent rate-constant values were obtained. The order of reactivity is shown to be Br − > Na 3 − > Cl − . The results are briefly discussed and compared with those previously reported.
Journal of Applied Electrochemistry | 1988
A. A. Mazhar; F. El-Taib Heakal; M. A. Ameer
Galvanostatic anodization of bismuth in different media indicates that the formation of the oxide film depends simultaneously on both pH and the anions present in the anodization medium. Dissolution of these films in NaOH supports this observation. The film is formed of two layers. Open circuit impedance and potential measurements in NaOH indicate film growth. The anodic film formed in NaOH dissolves, however, in NaOH solutions following a zero order mechanism. A number of factors including formation voltage, NaOH concentration, current density and temperature are investigated. The activation energy of the oxide film dissolution is calculated. It may be concluded that the outer layer, in addition to being of a more defective structure, is probably of a higher oxidation state than the inner layer.
RSC Advances | 2017
Ayman E. Elkholy; F. El-Taib Heakal; Nageh K. Allam
We report on the synthesis of manganese cobalt ferrite (MnCoFeO4) nanoparticles via a simple one-pot co-precipitation method and their characterization through energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared (FT-IR) spectroscopy and N2 adsorption/desorption techniques. The MnCoFeO4 supercapacitor showed the maximum specific capacitance of 675 F g−1 at a scan rate of 1 mV s−1. Its energy and power densities were 18.85 W h kg−1 and 337.50 W kg−1, respectively, at a current density of 1.5 A g−1. The cyclic stability was scrutinized via galvanostatic charging/discharging (GCD) and electrochemical impedance spectroscopy (EIS). The degradation of the supercapacitive performance was only 7.14% after 1000 GCD cycles, indicating an excellent long-term stability. The equivalent series resistance (ESR) remained nearly constant even after 1000 GCD cycles.
RSC Advances | 2017
M.A. Deyab; M. M. Osman; A.E. Elkholy; F. El-Taib Heakal
The anti-corrosion action of lemongrass (cymbopogon citratus) extract (LGE) was evaluated for carbon steel in produced oilfield water using weight loss method and electrochemical impedance spectroscopy (EIS). The results revealed that LGE serves as an effective corrosion inhibitor for C-steel via adsorption of its active constituents on the steel surface. The effect of time was studied by weight loss to assess the durability of the adsorbed film in protecting C-steel surface over a period of 28 days. The obtained results were further supported by surface examination of steel samples using FE-SEM, EDX and FTIR analyses. Theoretical study involved quantum chemical calculations and molecular dynamics simulation is also performed for the two most abundant components in lemongrass extract (neral and geranial).