Papers by Author: Khaled Habib

Abstract: A white light, i.e., Fabry-Perot, interferometry was unprecedently applied to determine the rate change of the current density (J) of aluminum samples during the anodization processes of the samples in aqueous solutions. The current density(J) values were obtained by Fabry-Perot interferometry rather than the direct current (DC) or alternating current (AC), methods. Therefore, the abrupt rate change of the J was called electrochemical-emission spectroscopy. The anodization of the aluminum samples was conducted by an external DC source in 0.0,2,4,6,8,10% sulfuric acid (H₂SO₄) solutions at room temperature. In the meantime, the Fabry-Perot interferometry was used to determine the difference between the J of two subsequent values, dJ, as a function of the elapsed time of the DC experiment for the aluminum samples in 0.0,2,4,6,8,10% H₂SO₄ solutions. The Fabry-Perot interferometry was based on a fiber-optic sensor in order to make real time-white light interferometry possible at the aluminum surfaces in the sulfuric acid solutions. As a result, a new spectrometer was developed based on the combination of the Fabry-Perot, i.e., white light, interferometry and DC method for studying in situ the electrochemical behavior of metals in aqueous solutions.

Abstract: The technique of electrochemical impedance spectroscopy (EIS) is widely used in laboratories and industries for materials evaluation. The aim of this investigation is to monitor the thickness of the anodized (oxide) aluminium sheets (samples) by using the EIS in a laboratory and a field study at a predetermined exposure duration in the field, i.e., 0, 1, 3, 6, 9, 12 months, in 0-10 % sulphuric acid. Four experimental stations were built out of KISR in order to monitor the thickness of the anodized (oxide) layer and the electrochemical parameters of anodized aluminium sheets by using the EIS. The zero state results at 0 exposure duration, indicating that as the concentration of the sulphuric acid increased from 0-10% H₂SO₄, the polarization resistance was observed to decrease from 3.15E+05 to 9.80E+03 Ohms, except at a concentration of 4% H₂SO₄, where the polarization resistance was observed to increase from 5.20E+03 to 2.90E+04 Ohms. On the contrary, the value of the solution resistance was observed to vary several times between 1.33E+04 to 1.53E+00 Ohms as a function of the increase of the sulphuric acid concentration from 0-10% H₂SO₄. In similar fashion to the polarization resistance, as the concentration of the sulphuric acid increased from 0-10% H₂SO₄, values of the alternating current impedance were found to vary several times between 1.94E+09 to 3.95E+05 Ohms, in a non-linear fashion. A similar behavior was observed on the values of the double layer capacitance as a function of the sulphuric acid increased, from 0-10% H₂SO₄, in which the values of the double layer capacitance was observed to change several times from 2.24E-09 to 2.53E-06 μF. The optimum thickness of the oxide film was detected (26.5 nm) at 8% H₂SO₄ of the sulphuric acid concentration. In order to determine the performance of the anodized aluminium-sheet in surrounding areas of Kuwait, a plan was arranged for such a field study. The field study consists of setting up four racks of sample panels in different locations in Kuwait. The racks were installed in the main field of Kuwait Institute for Scientific Research (KISR) in Shuwaikh area, in a residential area of South Sura area, in the main field of the Petroleum Research Department and Studies Center (PRSC) of Kuwait Institute for Scientific Research (KISR), in an industrial area of Ahmadi city, and in the main field of the fishery department of Kuwait Institute for Scientific Research (KISR) in a marine area of Salmia. The investigation planned to take a sheet each three months, for a 12 months duration, in order to determine the electrochemical parameters and the oxide film thickness of the sheets by the EIS technique in the field and to compare the data with those obtained in this report, at zero state.

Abstract: In a recent study conducted by the author, microcrystallites were observed to exist in amorphous, short range ordered, structures of several metallic glasses. The observation is based on X-Ray Diffraction (XRD) and Electron Diffraction (ED) and Transmission Electron Microscopy (TEM). The data from the X-ray diffraction shows that the metallic glasses have typical amorphous structures. However, the data from the Electron Diffraction indicates that the metallic glasses possess polycrystalline structures. This discrepancy between the XRD and ED data can be interpreted and explained by diffraction theory [1,2] with the aid of Transmission Electron Microscopy. In fact results in the recent work show that with a mathematical relationship originally derived by Sherrer [1], one can determine the boundary line between microcrystallites in amorphous, short range ordered, structures and crystalline, long range ordered, structures. The boundary line of microcrystallites is defined with the aid of Transmission Electron Microscopy in which the size of subgrains, of the metallic glasses was determined from the mathematical relationship.

Abstract: A general model of transport of gases in an artificial epidermal layer (membrane) was established. The model was developed based on Dusty Gas Model (DGM), solution diffusion and surface diffusion. As a result, solutions of the model for different transport conditions were derived. In this investigation, parameters of oxygen and carbon dioxide gases through an artificial “epidermal” membrane of varying porosity were used to calculate semi-empirical solutions of the general model. In other words, the solutions of the general model were analytically obtained for different transport conditions, using experimentally obtained parameters of oxygen and carbon dioxide gases through the artificial “epidermal” membrane of varying porosity. The obtained solutions of the general model were for the oxygen and carbon dioxide gases through the artificial “epidermal” membrane of the varying porosity.

Abstract: In the present investigation, holographic interferometry was utilized for the first time to measure in situ the thickness of the oxide film, alternating current (A.C.) impedance, and double layer capacitance of aluminium samples during anodization processes in aqueous solution without any physical contact. The anodization process (oxidation) of the aluminium samples was carried out by the electrochemical impedance spectroscopy (EIS), in different concentrations of sulphuric acid (0.5-2.5 % H2SO4) at room temperature. In the mean time, the real-time holographic interferometric was used to measure the thickness of anodized (oxide) film of the aluminium samples in aqueous solutions. Also, mathematical models were applied to measure the alternating current (A.C.) impedance, and double layer capacitance of aluminium samples by holographic interferometry, during anodization processes in aqueous solution. Consequently, holographic interferometric is found very useful for surface finish industries especially for monitoring the early stage of anodization processes of metals, in which the thickness of the anodized film, the A.C. impedance, and the double layer capacitance of the aluminium samples in sulphuric acid (0.5-2.5 % H2SO4) can be determined in situ. Futhermore, a comparison was made between the electrochemical values obtained from the holographic interferometry measurements and from measurements of electrochemical impedance spectroscopy(EIS) on aluminium samples in sulphuric acid (0.5-2.5 % H2SO4). The comparison indicates that there is good agreement between the obtained electrochemical data from both techniques. However, there is a drastic difference between the measurement of the oxide film thickness by both techniques. The oxide film thickness of the aluminium samples in 0, 0.5, 1.0, 1.5, 2.0, 2.5% H2SO4 by the optical interferometry is in a micrometer scale. However, the oxide film thickness of the aluminium samples in 0, 0.5, 1.0, 1.5, 2.0, 2.5% H2SO4 by the E.I.Spectroscopy in a nanometer scale. This can be explained due to the fact that the E.I.Spectroscopy is useful technique to measure the electrochemical parameters and the thickness of the barrier (compact) oxide films. In contrast, the optical interferometry is found useful technique to characterize and measure the thickness of the porous oxide layer. Also, the optimum thickness of the oxide barrier film was detected to be equivalent to 0.612nm in sulphuric acid concentration of 2.5% H2SO4 by E.I. spectroscopy.

Abstract: In the present work, the electrochemical behavior and the oxide barrier-film thickness of anodized aluminum-magnesium (Al-Mg) alloy were determined in the as-received and annealed conditions by using electrochemical techniques. Electrochemical parameters such as the polarization resistance, solution resistance, alternating-current (AC) impedance, and the doublelayer capacitance of the anodized Al-Mg alloy were determined in boric acid solutions, with 0 to 10%H3BO3, by using electrochemical impedance spectroscopic (EIS) methods. The oxide barrierfilm thickness of the anodized Al-Mg alloy was then deduced, from the electrochemical parameters obtained, as a function of the boric acid concentration (0 to 10%H3BO3). The optimum thickness of the oxide barrier-film was detected for as received samples (1.17nm) and for annealed samples (1.22nm) at a boric acid concentration of 4%H3BO3.

Abstract: In the present work, thermal expansion coefficients of a number of ceramic coatings were studied by a non-destructive technique (NDT) known as shearography. Ceramic coatings, i.e., a white enamel and a yellow Acrylic Lacquer on a metallic alloy, i.e., carbon steels, were investigated at a temperature range simulating the severe weather temperatures in Kuwait, especially between the daylight and the night time temperatures, 20-60 0C. The investigation was focused on determining the in-plane displacement of the coating, which corresponds to the thermal deformation (strain), with respect to the applied temperature range. A mathematical relationship was derived along with the experimental data. The mathematical relationship described the thermal deformation of a coated film as a function of temperature. Furthermore, results of shearography indicate that the technique is found very useful NDT method not only for determining the thermal expansion coefficients of different coatings, but also the technique can be used as a 2D- microscope for monitoring the deformation of various coatings in at a submicroscopic scale.

Abstract: In the present work, thermal expansion coefficients of a number of organic coatings were studied by a non-destructive technique (NDT) known as shearography. An organic coating, i.e., epoxy, on a metallic alloy, i.e., carbon steels, was investigated at a temperature range simulating the severe weather temperatures in Kuwait especially between the daylight and the night time temperatures, 20-60 0C. The investigation focused on determining the in-plane displacement of the coating, which amounts to the thermal deformation (strain ) with respect to the applied temperature range. Along with the experimental data, a mathematical relationship was derived describing the thermal deformation of a coated film as a function of temperature. Furthermore, results of shearography indicate that the technique is very useful NDT method not only for determining the thermal expansion coefficients of different coatings, but also the technique can be used as a 2Dmicroscope for monitoring the deformation of the coatings in real-time at a submicroscopic scale.