Mazen Khaled | Qatar University (original) (raw)

Papers by Mazen Khaled

Journal of Agricultural and Food Chemistry, 2001

Journal of The American Chemical Society, 1994

Resonance Studies of C60-3 c602-, and C6o3- ... Mazen M. Khaled, Richard T. Carlin,t Paul C. Trul... more Resonance Studies of C60-3 c602-, and C6o3- ... Mazen M. Khaled, Richard T. Carlin,t Paul C. Trulove,t Careth R. Eaton, and Sandra S. Eaton' ... Contribution from the Department of Chemistry, University of Denver, Denver, Colorado 80208, and Frank J. Seiler Research ...

The Open Nanomedicine Journal, 2008

A novel method using the layer by layer (LBL) technique was investigated to deposit polyelectroly... more A novel method using the layer by layer (LBL) technique was investigated to deposit polyelectrolytes with antibacterial properties. A glass substrate was coated by a cationic biguanide followed by the anionic polystyrene sulfonate until a total of twenty layers were deposited. The layers thickness was measured by ellipsometry and the surface morphology was scanned by an atomic force microscope. The layers thickness reached 60nm. The coated and uncoated glass was immersed into tubes containing a nutrient broth media inoculated with Proteus sp., (a gram negative , rod, glucose fermenting bacteria) in a concentration of (~10 5 cells/mL) and incubated at 37°C for 24 hours. The SEM (Scanning Electron Microscope) micrographs showed a significant reduction in the settlement of Proteus sp. Colonies on the glass coated with polyelectrolytes.

Chemical Physics Letters, 1991

The hybrid density functional theory method B3LYP is employed to study the -carotene radical cati... more The hybrid density functional theory method B3LYP is employed to study the -carotene radical cation. The radical is characterized by means of its geometry, spin distribution, and isotropic and anisotropic hyperfine coupling constants. It is shown that the spin is delocalized over the whole π-conjugated system, including the double bonds of the headgroups. This delocalization results in methyl hyperfine coupling constants lower than 9 MHz, in excellent agreement with recent experimental couplings of the carotene radical in Photosystem II and in vitro, but in conflict with previous theoretical calculations. It is also demonstrated that rotation of the headgroups can affect the properties of the radical, in particular the spin delocalization to the ring.

The Journal of Physical Chemistry, 1990

... C. Kenneth White and Reuben D. Rieke ... simulations of theo-retical EPR spectra were done us... more ... C. Kenneth White and Reuben D. Rieke ... simulations of theo-retical EPR spectra were done using a Fortran IV program for mix-tures employing Lorentzian line shapes written by RG Griffin.24 The program used for the Huckel MO calculations was written by Munch and RiekeZ5 ...

Chemical Physics, 1991

The lifetime of the lowest excited singlet state of a highly polarizable polyene, all-trans-7',7'... more The lifetime of the lowest excited singlet state of a highly polarizable polyene, all-trans-7',7'dicyano-7'-apo-p-carotene, 1, was measured as a function of solvent dielectric constant at 295 K and temperature from 7.4295 K. The polyene was excited in separate experiments with 610 nm, 2 ps, and 450 nm, 4 ps laser pulses. The broad 400-650 nm absorption band of the polyene bleaches immediately upon excitation, while a strong absorption centered between 680-705 nm appears. Both the recovery of the ground state absorption band and the disappearance of the 680-705 nm excited state absorption band exhibit the same single exponential kinetics that depend on both solvent dielectric constant and on temperature. As the dielectric constant of the solvent increases from 1.9 to 36, the lifetime of the lowest excited singlet state of 1 decreases from 11.7 ps to 1.9 ps. As the temperature is lowered the lifetime of the lowest excited singlet state of 1 approaches that observed in low dielectric constant media. The behavior of 1 is ascribed to a large change in dipole moment between the ground and lowest excited singlet state. Interaction of the excited state dipole with solvent dipoles results in enhanced charge transfer character within the excited state, which in turn enhances nonradiative decay of the excited state. The excited state dipole moments of the ground, first, and second excited states of both 1 and P-8'-apocarotenal, 2 were calculated using the AM1 molecular orbital method. The calculations predict that 1 has a 5.1 Debye difference in dipole moment between the ground and first excited state.

The lifetime of the lowest excited singlet state of a highly polarizable polyene, all-trans-7',7'... more The lifetime of the lowest excited singlet state of a highly polarizable polyene, all-trans-7',7'dicyano-7'-apo-p-carotene, 1, was measured as a function of solvent dielectric constant at 295 K and temperature from 7.4295 K. The polyene was excited in separate experiments with 610 nm, 2 ps, and 450 nm, 4 ps laser pulses. The broad 400-650 nm absorption band of the polyene bleaches immediately upon excitation, while a strong absorption centered between 680-705 nm appears. Both the recovery of the ground state absorption band and the disappearance of the 680-705 nm excited state absorption band exhibit the same single exponential kinetics that depend on both solvent dielectric constant and on temperature. As the dielectric constant of the solvent increases from 1.9 to 36, the lifetime of the lowest excited singlet state of 1 decreases from 11.7 ps to 1.9 ps. As the temperature is lowered the lifetime of the lowest excited singlet state of 1 approaches that observed in low dielectric constant media. The behavior of 1 is ascribed to a large change in dipole moment between the ground and lowest excited singlet state. Interaction of the excited state dipole with solvent dipoles results in enhanced charge transfer character within the excited state, which in turn enhances nonradiative decay of the excited state. The excited state dipole moments of the ground, first, and second excited states of both 1 and P-8'-apocarotenal, 2 were calculated using the AM1 molecular orbital method. The calculations predict that 1 has a 5.1 Debye difference in dipole moment between the ground and first excited state.

The lifetime of the lowest excited singlet state of a highly polarizable polyene, all-trans-7',7'... more The lifetime of the lowest excited singlet state of a highly polarizable polyene, all-trans-7',7'dicyano-7'-apo-p-carotene, 1, was measured as a function of solvent dielectric constant at 295 K and temperature from 7.4295 K. The polyene was excited in separate experiments with 610 nm, 2 ps, and 450 nm, 4 ps laser pulses. The broad 400-650 nm absorption band of the polyene bleaches immediately upon excitation, while a strong absorption centered between 680-705 nm appears. Both the recovery of the ground state absorption band and the disappearance of the 680-705 nm excited state absorption band exhibit the same single exponential kinetics that depend on both solvent dielectric constant and on temperature. As the dielectric constant of the solvent increases from 1.9 to 36, the lifetime of the lowest excited singlet state of 1 decreases from 11.7 ps to 1.9 ps. As the temperature is lowered the lifetime of the lowest excited singlet state of 1 approaches that observed in low dielectric constant media. The behavior of 1 is ascribed to a large change in dipole moment between the ground and lowest excited singlet state. Interaction of the excited state dipole with solvent dipoles results in enhanced charge transfer character within the excited state, which in turn enhances nonradiative decay of the excited state. The excited state dipole moments of the ground, first, and second excited states of both 1 and P-8'-apocarotenal, 2 were calculated using the AM1 molecular orbital method. The calculations predict that 1 has a 5.1 Debye difference in dipole moment between the ground and first excited state.

The Journal of Physical Chemistry, 1994

A series of substituted phenyl-7'-apocarotenoids with varying electron donating and accepting sub... more A series of substituted phenyl-7'-apocarotenoids with varying electron donating and accepting substituents was examined by cyclic voltammogram (CV) and simultaneous electrochemical electron paramagnetic resonance (SEEPR). Carotenoids substituted with electron donating groups are more easily oxidized than those with electron accepting substituents. Comproportionation constants for the dication and the neutral species were measured by SEEPR techniques and by simulation of the CVs. The AHpp of the SEEPR spectrum of the cation radicals varies from 13.2 to 15.6 G, and the g factors are 2.0021 f 0.0002. These EPR parameters suggest a polyene ?r-cation radical structure. The CVs are calculated using DigiSim, a C V simulation program, and the proposed mechanism involves three electrode reactions and two homogeneous reactions.

The Journal of Physical Chemistry, 1991

A series of substituted phenyl-7'-apocarotenoids with varying electron donating and accepting sub... more A series of substituted phenyl-7'-apocarotenoids with varying electron donating and accepting substituents was examined by cyclic voltammogram (CV) and simultaneous electrochemical electron paramagnetic resonance (SEEPR). Carotenoids substituted with electron donating groups are more easily oxidized than those with electron accepting substituents. Comproportionation constants for the dication and the neutral species were measured by SEEPR techniques and by simulation of the CVs. The AHpp of the SEEPR spectrum of the cation radicals varies from 13.2 to 15.6 G, and the g factors are 2.0021 f 0.0002. These EPR parameters suggest a polyene ?r-cation radical structure. The CVs are calculated using DigiSim, a C V simulation program, and the proposed mechanism involves three electrode reactions and two homogeneous reactions.

Surface & Coatings Technology, 2007

The corrosion susceptibility of steel and HVOF-coated steel in solutions simulating the alkaline ... more The corrosion susceptibility of steel and HVOF-coated steel in solutions simulating the alkaline concrete pore environment and with the addition of chloride was investigated using potentiodynamic polarization and potential step techniques. The surface characterization was performed using SEM and the surface elemental analysis was determined by EDS. The concentration of chloride was 2.8 M to simulate the concentration of chloride spread in many local regions of Saudi Arabia and called Sabkha. It was found that, in the case of the simulated concrete pore electrolytes, the HVOF coating resulted in an anodic shift of the corrosion potential with marginal effect on the corrosion current. However, upon addition of 2.8 M chloride solution, the corrosion rate of the HVOF-coated steel was found to increase by a factor of two. SEM showed a network of pores within the coating which provides a path for the electrolyte. This would result in preferential corrosion around splat boundaries and confirmed by EDS which showed that the corroded splats have higher oxide contents. Potential step experiments at 400 mV above open circuit potential showed a suppressed current of the HVOF-coated steel compared to the steel substrate alone. The corrosion potential versus time experiments resulted in a more anodic Ecorr which decreased with time and became equal to the Ecorr of the bare steel after 34 h. After that, the corrosion potential of the HVOF-coated steel decreased due to the increase in galvanic coupling between the steel and the HVOF coating.

Surface & Coatings Technology, 2006

The corrosion properties of duplex-treated and nitrided Ti-6Al-4V have been investigated in 0.025... more The corrosion properties of duplex-treated and nitrided Ti-6Al-4V have been investigated in 0.025, 0.25 and 2.5 M NaCl using electrochemical techniques, Positron Annihilation Spectroscopy (PAS), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometry (EDS). The electrochemical results showed a three-fold increase in corrosion rate for every ten-fold increase in chloride concentration. The morphology and surface composition studied by XRD showed the presence of TiN and Ti 2 N layers. SEM and EDS showed the presence of pitting and the presence of oxide and chloride products. At the lowest concentration of NaCl no aluminum was detected in the surface layers while at the highest concentration no chloride byproducts were detected. PAS indicated that the damage caused by the NaCl changes in nature and becomes shallower as the concentration increases.

Surface & Coatings Technology, 2001

... a, Chemistry Department, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi... more ... a, Chemistry Department, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia. b, Mechanical Engineering Department, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia. ...

Journal of Materials Engineering and Performance, 2009

Laser surface melting of aluminum alloy 8022 is considered and electrochemical studies of the las... more Laser surface melting of aluminum alloy 8022 is considered and electrochemical studies of the laser-melted and as-received alloy surface are carried out. The surface morphology and metallurgical changes in the laser-melted region are examined using optical microscopy, electron scanning microscopy (SEM), and atomic force microscopy (AFM). Elemental changes in the specimens after the laser-melting process are examined using energy dispersive spectroscopy (EDS), and x-ray diffraction (XRD) is used for assessment of the compound formed after the laser-treatment process. Nitrogen is used as an assisting gas during the laser-melting process to prevent high-temperature oxidation reactions. It is found that the laser-melted surfaces is free from cracks and deep cavities. The oxygen diffusion in the surface region of the melt layer forms Al2O3 compound in the surface vicinity. The corrosion current increases significantly for the laser-melted specimens due to the irregular surface structure. AC impedance results showed a decrease in pores resistant and an increase in pores capacitance. In addition, the surface morphology resulting from the laser melting gives rise to pitting sites at the surface.

Industrial Lubrication and Tribology, 2011

Purpose -Laser bending is a good candidate to replace the flame bending process. The electrochemi... more Purpose -Laser bending is a good candidate to replace the flame bending process. The electrochemical response of laser bending region changes due to the microstructural modifications and high level of residual stress developed in the laser-irradiated region after the bending process. Consequently, investigation into laser bending and microstructural changes in the irradiated region as well as the electrochemical response of bending section becomes essential. This paper aims to focus on the laser bending process. Design/methodology/approach -The laser bending of steel sheets was carried out. The microstructural changes in the bending region are examined using the scanning electron microscopy and X-ray diffraction. The electrochemical response of the bended sections is investigated through potentiodynamic tests. Findings -It is found that laser-irradiated surface is free from cracks and cavitations. However, deep pit sites due to secondary pitting are observed in the bending sections.

International Journal of Hydrogen Energy, 1998

... in Great Britain 03603199 98 I19.00+0.00 HYDROGEN EMBRITTLEMENT OF Ti6Al4V ALLOY WITH SURFACE... more ... in Great Britain 03603199 98 I19.00+0.00 HYDROGEN EMBRITTLEMENT OF Ti6Al4V ALLOY WITH SURFACE MODIFICATION BY TiN COATING BS YILBAS, A. COBAN+, R. KAHRAMANI and MM KHALED * Department of Mechanical Engineering, King Fahd University of ...

Surface & Coatings Technology, 2006

... et al. [15]. They indicated that (Ti,Al)N coating improved the corrosion performance of the c... more ... et al. [15]. They indicated that (Ti,Al)N coating improved the corrosion performance of the coated surface. Microstructural and corrosion evaluation of laser nitrided titanium alloy was studied by Geetha et al. [16]. They showed ...

Polyelectrolyte multilayer (PEM) thin films consisting of alternate layers of two PEM systems, th... more Polyelectrolyte multilayer (PEM) thin films consisting of alternate layers of two PEM systems, that is poly(diallyl dimethyl ammonium chloride)/poly(vinyl sulfate) (PDAC/PVS) and poly(allyl amine hydrochloride) (PAH)/ are successfully deposited on polysulfone (PSF) support using spin-assisted layer-bylayer assembly. The films are characterized using atomic force microscope, Fourier transform Infrared, and contact angle measurement. The salt (NaCl) rejection and water flux of the [PDAC/PVS] and [PAH/PVS] membranes are also evaluated using a crossflow permeation test cell. The permeation test shows that 120 bilayers of [PAH/PVS] on PSF substrate provide salt rejection of 53% and water flux of 37 L/m 2 h, whereas that of PDAC/PVS on PSF substrate provide salt rejection of 21% and water flux of 90 L/m 2 h for a 2000-ppm NaCl solution feed at a pressure of 40 bar and temperature of 25 C.

Journal of Agricultural and Food Chemistry, 2001

Journal of The American Chemical Society, 1994

Resonance Studies of C60-3 c602-, and C6o3- ... Mazen M. Khaled, Richard T. Carlin,t Paul C. Trul... more Resonance Studies of C60-3 c602-, and C6o3- ... Mazen M. Khaled, Richard T. Carlin,t Paul C. Trulove,t Careth R. Eaton, and Sandra S. Eaton' ... Contribution from the Department of Chemistry, University of Denver, Denver, Colorado 80208, and Frank J. Seiler Research ...

The Open Nanomedicine Journal, 2008

A novel method using the layer by layer (LBL) technique was investigated to deposit polyelectroly... more A novel method using the layer by layer (LBL) technique was investigated to deposit polyelectrolytes with antibacterial properties. A glass substrate was coated by a cationic biguanide followed by the anionic polystyrene sulfonate until a total of twenty layers were deposited. The layers thickness was measured by ellipsometry and the surface morphology was scanned by an atomic force microscope. The layers thickness reached 60nm. The coated and uncoated glass was immersed into tubes containing a nutrient broth media inoculated with Proteus sp., (a gram negative , rod, glucose fermenting bacteria) in a concentration of (~10 5 cells/mL) and incubated at 37°C for 24 hours. The SEM (Scanning Electron Microscope) micrographs showed a significant reduction in the settlement of Proteus sp. Colonies on the glass coated with polyelectrolytes.

Chemical Physics Letters, 1991

The hybrid density functional theory method B3LYP is employed to study the -carotene radical cati... more The hybrid density functional theory method B3LYP is employed to study the -carotene radical cation. The radical is characterized by means of its geometry, spin distribution, and isotropic and anisotropic hyperfine coupling constants. It is shown that the spin is delocalized over the whole π-conjugated system, including the double bonds of the headgroups. This delocalization results in methyl hyperfine coupling constants lower than 9 MHz, in excellent agreement with recent experimental couplings of the carotene radical in Photosystem II and in vitro, but in conflict with previous theoretical calculations. It is also demonstrated that rotation of the headgroups can affect the properties of the radical, in particular the spin delocalization to the ring.

The Journal of Physical Chemistry, 1990

... C. Kenneth White and Reuben D. Rieke ... simulations of theo-retical EPR spectra were done us... more ... C. Kenneth White and Reuben D. Rieke ... simulations of theo-retical EPR spectra were done using a Fortran IV program for mix-tures employing Lorentzian line shapes written by RG Griffin.24 The program used for the Huckel MO calculations was written by Munch and RiekeZ5 ...

Chemical Physics, 1991

The lifetime of the lowest excited singlet state of a highly polarizable polyene, all-trans-7',7'... more The lifetime of the lowest excited singlet state of a highly polarizable polyene, all-trans-7',7'dicyano-7'-apo-p-carotene, 1, was measured as a function of solvent dielectric constant at 295 K and temperature from 7.4295 K. The polyene was excited in separate experiments with 610 nm, 2 ps, and 450 nm, 4 ps laser pulses. The broad 400-650 nm absorption band of the polyene bleaches immediately upon excitation, while a strong absorption centered between 680-705 nm appears. Both the recovery of the ground state absorption band and the disappearance of the 680-705 nm excited state absorption band exhibit the same single exponential kinetics that depend on both solvent dielectric constant and on temperature. As the dielectric constant of the solvent increases from 1.9 to 36, the lifetime of the lowest excited singlet state of 1 decreases from 11.7 ps to 1.9 ps. As the temperature is lowered the lifetime of the lowest excited singlet state of 1 approaches that observed in low dielectric constant media. The behavior of 1 is ascribed to a large change in dipole moment between the ground and lowest excited singlet state. Interaction of the excited state dipole with solvent dipoles results in enhanced charge transfer character within the excited state, which in turn enhances nonradiative decay of the excited state. The excited state dipole moments of the ground, first, and second excited states of both 1 and P-8'-apocarotenal, 2 were calculated using the AM1 molecular orbital method. The calculations predict that 1 has a 5.1 Debye difference in dipole moment between the ground and first excited state.

The lifetime of the lowest excited singlet state of a highly polarizable polyene, all-trans-7',7'... more The lifetime of the lowest excited singlet state of a highly polarizable polyene, all-trans-7',7'dicyano-7'-apo-p-carotene, 1, was measured as a function of solvent dielectric constant at 295 K and temperature from 7.4295 K. The polyene was excited in separate experiments with 610 nm, 2 ps, and 450 nm, 4 ps laser pulses. The broad 400-650 nm absorption band of the polyene bleaches immediately upon excitation, while a strong absorption centered between 680-705 nm appears. Both the recovery of the ground state absorption band and the disappearance of the 680-705 nm excited state absorption band exhibit the same single exponential kinetics that depend on both solvent dielectric constant and on temperature. As the dielectric constant of the solvent increases from 1.9 to 36, the lifetime of the lowest excited singlet state of 1 decreases from 11.7 ps to 1.9 ps. As the temperature is lowered the lifetime of the lowest excited singlet state of 1 approaches that observed in low dielectric constant media. The behavior of 1 is ascribed to a large change in dipole moment between the ground and lowest excited singlet state. Interaction of the excited state dipole with solvent dipoles results in enhanced charge transfer character within the excited state, which in turn enhances nonradiative decay of the excited state. The excited state dipole moments of the ground, first, and second excited states of both 1 and P-8'-apocarotenal, 2 were calculated using the AM1 molecular orbital method. The calculations predict that 1 has a 5.1 Debye difference in dipole moment between the ground and first excited state.

The lifetime of the lowest excited singlet state of a highly polarizable polyene, all-trans-7',7'... more The lifetime of the lowest excited singlet state of a highly polarizable polyene, all-trans-7',7'dicyano-7'-apo-p-carotene, 1, was measured as a function of solvent dielectric constant at 295 K and temperature from 7.4295 K. The polyene was excited in separate experiments with 610 nm, 2 ps, and 450 nm, 4 ps laser pulses. The broad 400-650 nm absorption band of the polyene bleaches immediately upon excitation, while a strong absorption centered between 680-705 nm appears. Both the recovery of the ground state absorption band and the disappearance of the 680-705 nm excited state absorption band exhibit the same single exponential kinetics that depend on both solvent dielectric constant and on temperature. As the dielectric constant of the solvent increases from 1.9 to 36, the lifetime of the lowest excited singlet state of 1 decreases from 11.7 ps to 1.9 ps. As the temperature is lowered the lifetime of the lowest excited singlet state of 1 approaches that observed in low dielectric constant media. The behavior of 1 is ascribed to a large change in dipole moment between the ground and lowest excited singlet state. Interaction of the excited state dipole with solvent dipoles results in enhanced charge transfer character within the excited state, which in turn enhances nonradiative decay of the excited state. The excited state dipole moments of the ground, first, and second excited states of both 1 and P-8'-apocarotenal, 2 were calculated using the AM1 molecular orbital method. The calculations predict that 1 has a 5.1 Debye difference in dipole moment between the ground and first excited state.

The Journal of Physical Chemistry, 1994

A series of substituted phenyl-7'-apocarotenoids with varying electron donating and accepting sub... more A series of substituted phenyl-7'-apocarotenoids with varying electron donating and accepting substituents was examined by cyclic voltammogram (CV) and simultaneous electrochemical electron paramagnetic resonance (SEEPR). Carotenoids substituted with electron donating groups are more easily oxidized than those with electron accepting substituents. Comproportionation constants for the dication and the neutral species were measured by SEEPR techniques and by simulation of the CVs. The AHpp of the SEEPR spectrum of the cation radicals varies from 13.2 to 15.6 G, and the g factors are 2.0021 f 0.0002. These EPR parameters suggest a polyene ?r-cation radical structure. The CVs are calculated using DigiSim, a C V simulation program, and the proposed mechanism involves three electrode reactions and two homogeneous reactions.

The Journal of Physical Chemistry, 1991

A series of substituted phenyl-7'-apocarotenoids with varying electron donating and accepting sub... more A series of substituted phenyl-7'-apocarotenoids with varying electron donating and accepting substituents was examined by cyclic voltammogram (CV) and simultaneous electrochemical electron paramagnetic resonance (SEEPR). Carotenoids substituted with electron donating groups are more easily oxidized than those with electron accepting substituents. Comproportionation constants for the dication and the neutral species were measured by SEEPR techniques and by simulation of the CVs. The AHpp of the SEEPR spectrum of the cation radicals varies from 13.2 to 15.6 G, and the g factors are 2.0021 f 0.0002. These EPR parameters suggest a polyene ?r-cation radical structure. The CVs are calculated using DigiSim, a C V simulation program, and the proposed mechanism involves three electrode reactions and two homogeneous reactions.

Surface & Coatings Technology, 2007

The corrosion susceptibility of steel and HVOF-coated steel in solutions simulating the alkaline ... more The corrosion susceptibility of steel and HVOF-coated steel in solutions simulating the alkaline concrete pore environment and with the addition of chloride was investigated using potentiodynamic polarization and potential step techniques. The surface characterization was performed using SEM and the surface elemental analysis was determined by EDS. The concentration of chloride was 2.8 M to simulate the concentration of chloride spread in many local regions of Saudi Arabia and called Sabkha. It was found that, in the case of the simulated concrete pore electrolytes, the HVOF coating resulted in an anodic shift of the corrosion potential with marginal effect on the corrosion current. However, upon addition of 2.8 M chloride solution, the corrosion rate of the HVOF-coated steel was found to increase by a factor of two. SEM showed a network of pores within the coating which provides a path for the electrolyte. This would result in preferential corrosion around splat boundaries and confirmed by EDS which showed that the corroded splats have higher oxide contents. Potential step experiments at 400 mV above open circuit potential showed a suppressed current of the HVOF-coated steel compared to the steel substrate alone. The corrosion potential versus time experiments resulted in a more anodic Ecorr which decreased with time and became equal to the Ecorr of the bare steel after 34 h. After that, the corrosion potential of the HVOF-coated steel decreased due to the increase in galvanic coupling between the steel and the HVOF coating.

Surface & Coatings Technology, 2006

The corrosion properties of duplex-treated and nitrided Ti-6Al-4V have been investigated in 0.025... more The corrosion properties of duplex-treated and nitrided Ti-6Al-4V have been investigated in 0.025, 0.25 and 2.5 M NaCl using electrochemical techniques, Positron Annihilation Spectroscopy (PAS), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometry (EDS). The electrochemical results showed a three-fold increase in corrosion rate for every ten-fold increase in chloride concentration. The morphology and surface composition studied by XRD showed the presence of TiN and Ti 2 N layers. SEM and EDS showed the presence of pitting and the presence of oxide and chloride products. At the lowest concentration of NaCl no aluminum was detected in the surface layers while at the highest concentration no chloride byproducts were detected. PAS indicated that the damage caused by the NaCl changes in nature and becomes shallower as the concentration increases.

Surface & Coatings Technology, 2001

... a, Chemistry Department, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi... more ... a, Chemistry Department, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia. b, Mechanical Engineering Department, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia. ...

Journal of Materials Engineering and Performance, 2009

Laser surface melting of aluminum alloy 8022 is considered and electrochemical studies of the las... more Laser surface melting of aluminum alloy 8022 is considered and electrochemical studies of the laser-melted and as-received alloy surface are carried out. The surface morphology and metallurgical changes in the laser-melted region are examined using optical microscopy, electron scanning microscopy (SEM), and atomic force microscopy (AFM). Elemental changes in the specimens after the laser-melting process are examined using energy dispersive spectroscopy (EDS), and x-ray diffraction (XRD) is used for assessment of the compound formed after the laser-treatment process. Nitrogen is used as an assisting gas during the laser-melting process to prevent high-temperature oxidation reactions. It is found that the laser-melted surfaces is free from cracks and deep cavities. The oxygen diffusion in the surface region of the melt layer forms Al2O3 compound in the surface vicinity. The corrosion current increases significantly for the laser-melted specimens due to the irregular surface structure. AC impedance results showed a decrease in pores resistant and an increase in pores capacitance. In addition, the surface morphology resulting from the laser melting gives rise to pitting sites at the surface.

Industrial Lubrication and Tribology, 2011

Purpose -Laser bending is a good candidate to replace the flame bending process. The electrochemi... more Purpose -Laser bending is a good candidate to replace the flame bending process. The electrochemical response of laser bending region changes due to the microstructural modifications and high level of residual stress developed in the laser-irradiated region after the bending process. Consequently, investigation into laser bending and microstructural changes in the irradiated region as well as the electrochemical response of bending section becomes essential. This paper aims to focus on the laser bending process. Design/methodology/approach -The laser bending of steel sheets was carried out. The microstructural changes in the bending region are examined using the scanning electron microscopy and X-ray diffraction. The electrochemical response of the bended sections is investigated through potentiodynamic tests. Findings -It is found that laser-irradiated surface is free from cracks and cavitations. However, deep pit sites due to secondary pitting are observed in the bending sections.

International Journal of Hydrogen Energy, 1998

... in Great Britain 03603199 98 I19.00+0.00 HYDROGEN EMBRITTLEMENT OF Ti6Al4V ALLOY WITH SURFACE... more ... in Great Britain 03603199 98 I19.00+0.00 HYDROGEN EMBRITTLEMENT OF Ti6Al4V ALLOY WITH SURFACE MODIFICATION BY TiN COATING BS YILBAS, A. COBAN+, R. KAHRAMANI and MM KHALED * Department of Mechanical Engineering, King Fahd University of ...

Surface & Coatings Technology, 2006

... et al. [15]. They indicated that (Ti,Al)N coating improved the corrosion performance of the c... more ... et al. [15]. They indicated that (Ti,Al)N coating improved the corrosion performance of the coated surface. Microstructural and corrosion evaluation of laser nitrided titanium alloy was studied by Geetha et al. [16]. They showed ...

Polyelectrolyte multilayer (PEM) thin films consisting of alternate layers of two PEM systems, th... more Polyelectrolyte multilayer (PEM) thin films consisting of alternate layers of two PEM systems, that is poly(diallyl dimethyl ammonium chloride)/poly(vinyl sulfate) (PDAC/PVS) and poly(allyl amine hydrochloride) (PAH)/ are successfully deposited on polysulfone (PSF) support using spin-assisted layer-bylayer assembly. The films are characterized using atomic force microscope, Fourier transform Infrared, and contact angle measurement. The salt (NaCl) rejection and water flux of the [PDAC/PVS] and [PAH/PVS] membranes are also evaluated using a crossflow permeation test cell. The permeation test shows that 120 bilayers of [PAH/PVS] on PSF substrate provide salt rejection of 53% and water flux of 37 L/m 2 h, whereas that of PDAC/PVS on PSF substrate provide salt rejection of 21% and water flux of 90 L/m 2 h for a 2000-ppm NaCl solution feed at a pressure of 40 bar and temperature of 25 C.