Optimization of defect-free protective layer considering the geometrical linearity of condensed phosphates

Kaseem, Mosab,Ko, Young Gun Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.752 No.-

<P><B>Abstract</B></P> <P>The present study looked into the formation of a defect-free protective layer by considering the geometrical linearity of condensed phosphates. For this purpose, Al alloy sample treated by plasma electrolytic oxidation (PEO) in the aluminate-based electrolyte was immersed subsequently in the solutions with condensed phosphates, such as linear sodium tripolyphosphate (LP) and cyclic sodium hexamethaphosphate (CP). Microstructural observations revealed that the geometrical linearity of condensed phosphate would significantly modify the morphology of the oxide layer due to the incorporations of hydration and/or P-containing chemical compounds onto the oxide layer. Per the electrochemical assessment, it was found that the treatment by LP solution would provide superior corrosion resistance to the treatment by CP. This improvement was underlying by the formation of significant amounts of AlPO<SUB>4</SUB> to fill the structural defects through partial hydrolysis of LP whose phenomenon was triggered by hydration of γ-Al<SUB>2</SUB>O<SUB>3</SUB> oxide layer during sealing treatment.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The influences of geometrical linearity condensed phosphates on the characteristics of the PEO coatings was significant. </LI> <LI> The condensed phosphates could effectively modify the morphology of the coating. </LI> <LI> The corrosion resistance of the coating was significantly improved by sealing treatment via linear condensed phosphates. </LI> </UL> </P>

Rheological properties of ABS/wood composites

Kaseem, M.,Hamad, K.,Park, J. H.,Ko, Y. G. Springer Science + Business Media 2015 European journal of wood and wood products Vol.73 No.5

Microstructure and plastic anisotropy of fine grained AZ31 magnesium alloy fabricated by differential speed rolling at 473 and 573 K

Kaseem, M.,Yang, H. W.,Hamad, K.,Kim, Y. G.,Park, B. H.,Ko, Y. G. Informa UK (TaylorFrancis) 2015 Materials research innovations Vol.19 No.5

Electrochemical response of MoO₂-Al₂O₃ oxide films via plasma electrolytic oxidation

Kaseem, M.,Kamil, M.P.,Ko, Y.G. Elsevier 2017 Surface & coatings technology Vol.322 No.-

<P><B>Abstract</B></P> <P>The present investigation looked into the role of current frequency on the structural feature and electrochemical response of MoO<SUB>2</SUB>-Al<SUB>2</SUB>O<SUB>3</SUB> hybrid oxide films formed on Al-Mg-Si alloy subjected to plasma electrolytic oxidation (PEO). The current hybrid coatings were formed in an alkaline-silicate electrolyte containing sodium molybdate with respect to alternate current frequencies, such as 60, 500, and 1200Hz. The results of microstructural observations showed that the oxide film produced at 1200Hz was relatively more compact and less porous than those produced at 60 and 500Hz. This was attributed mainly to the incorporation of MoO<SUB>2</SUB> whose tendency was observed to be increase as current frequency increased in this study. Accordingly, the potentiodynamic polarization tests revealed that the sample coated at 1200Hz exhibited superior corrosion behavior to those coated at 60 and 500Hz. Such electrochemical response underlying the corrosion characteristics of the present alloy was discussed in the context of equivalent circuit model taking the roles of outer and inner layers, and interface between oxide film and substrate into account.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Effect of current frequency on incorporations of MoO<SUB>2</SUB> into oxide layers via PEO is significant. </LI> <LI> A significant change in the morphology is obtained with incorporations of MoO<SUB>2.</SUB> </LI> <LI> The corrosion resistance of Al alloy was improved with incorporations of MoO<SUB>2.</SUB> </LI> </UL> </P>

Corrosion behavior of Al-1wt% Mg-0.85wt%Si alloy coated by micro-arc-oxidation using TiO₂ and Na₂MoO₄ additives: Role of current density

Kaseem, Mosab,Min, Ji Hoon,Ko, Young Gun Elsevier 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.723 No.-

<P><B>Abstract</B></P> <P>The present study reported the formation of the oxide layer incorporating TiO<SUB>2</SUB> and MoO<SUB>2</SUB> particles and their influences on the microstructure and corrosion behavior of the oxide layer formed by micro-arc-oxidation (MAO) with respect to current density. For this purpose, MAO coatings on Al-1wt%Mg-0.85wt%Si alloy sample were performed under an alternating current condition in a silicate-molybdate electrolyte with dispersed TiO<SUB>2</SUB> at three different current densities, such as 100, 150, and 200 mAcm<SUP>−2</SUP>. The incorporation of TiO<SUB>2</SUB> would be attained through the combined effects of electrophoresis and physical mixing with the molten oxide during plasma arcing whilst the incorporation of MoO<SUB>2</SUB> would rely on the decomposition of molybdate ions triggered by plasma-assisted electrochemical reaction. Among three different oxide layers produced at three current densities, the oxide layer produced under 150 mAcm<SUP>−2</SUP> exhibited the lowest corrosion current density value of 2.79 × 10<SUP>−11</SUP> Acm<SUP>−2</SUP> as well as the highest polarization resistance value of 1.76 × 10<SUP>9</SUP> Ωcm<SUP>2</SUP>, which was attributed mainly to the fact that a significant decrease in micro-pore density by the incorporation of particles into the oxide layer was obtained. The electrochemical mechanism affecting corrosion resistance of the MAO-coated samples was elucidated based on the equivalent circuit model consisting of resistor and capacitor elements.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Effect of current density on incorporations of MoO<SUB>2</SUB> and TiO<SUB>2</SUB> into oxide layers via MAO is significant. </LI> <LI> A significant change in the morphology is obtained with incorporations of MoO<SUB>2</SUB> and TiO<SUB>2</SUB>. </LI> <LI> The corrosion resistance of Al alloy was improved with incorporations of MoO<SUB>2</SUB> and TiO<SUB>2</SUB>. </LI> </UL> </P>

A highly compact coating responsible for enhancing corrosion properties of Al-Mg-Si alloy

Kaseem, Mosab,Choi, Kyungsu,Ko, Young Gun Elsevier 2017 Materials letters Vol.196 No.-

<P><B>Abstract</B></P> <P>The formation of a highly compact coating responsible for improvement in corrosion properties of Al-Mg-Si alloy was investigated. In this study, a plasma electrolytic oxidation (PEO) was performed in a citrate-aluminate electrolyte with potassium hexafluorosilicate (K<SUB>2</SUB>SiF<SUB>6</SUB>), and the results were compared to the counterpart without K<SUB>2</SUB>SiF<SUB>6</SUB>. The addition of K<SUB>2</SUB>SiF<SUB>6</SUB> to the present electrolyte would give rise to the highly compact coating due to the insoluble compounds of SiO<SUB>2</SUB> and AlF<SUB>3</SUB> which were incorporated uniformly throughout the coating. This would lead effectively to superior corrosion-protection properties to the case without K<SUB>2</SUB>SiF<SUB>6</SUB>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A compact coating was successfully fabricated on Al-Mg-Si alloy via PEO process. </LI> <LI> A significant change in the morphology is obtained with addition of K<SUB>2</SUB>SiF<SUB>6</SUB>. </LI> <LI> Effect of K<SUB>2</SUB>SiF<SUB>6</SUB> on corrosion properties of Al-Mg-Si alloy via PEO is significant. </LI> </UL> </P>

Material properties of polyethylene/wood composites: A review of recent works

Kaseem, M.,Hamad, K.,Deri, F.,Ko, Y. G. Springer Science + Business Media 2015 Polymer science. Series A, Polymer physics Vol.57 No.6

On the compactness of the oxide layer induced by utilizing a porosification agent

Kaseem, Mosab,Ko, Young Gun Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.473 No.-

<P><B>Abstract</B></P> <P>It is imperative to control the pore density and distribution of pores produced inevitably on the surface of the oxide layer produced by plasma electrolysis (PE) process since these factors could affect the final electrochemical performance of these layers. Up to this study, utilizing a porosification agent in order to optimize the compactness of the oxide layer grown on Al alloy via PE has been rarely reported. Here, a simple novel strategy was proposed in the present work to control these defects by triggering the incorporation of V<SUB>2</SUB>O<SUB>5</SUB> through utilizing a high concentration of phosphate ions which was reported extensively as a porosification agent during PE process. For this aim, Al-Mg-Si alloy samples were treated by PE under AC conditions at a current density of 75 mA/cm<SUP>2</SUP> for 5 min from V<SUB>2</SUB>O<SUB>5</SUB>-based electrolytes with 0, 6 and 18 g/L of Na<SUB>3</SUB>PO<SUB>4</SUB>. It was found that the oxide layer made from electrolyte with 18 g/L Na<SUB>3</SUB>PO<SUB>4</SUB> was less porous and smoother than the counterparts with 0 and 6 g/L Na<SUB>3</SUB>PO<SUB>4</SUB>. This result was attributed to the development of uniform fine plasma sparks at the high concentration of Na<SUB>3</SUB>PO<SUB>4</SUB> responsible for facilitating the incorporation of V<SUB>2</SUB>O<SUB>5</SUB> particles into the oxide layer which resulted eventually in the formation of a conformal black coating. Accordingly, the electrochemical response of the oxide layer with 18 g/L Na<SUB>3</SUB>PO<SUB>4</SUB> was superior to that with 6 g/L Na<SUB>3</SUB>PO<SUB>4</SUB>. This study would potentially pave a way to obtain a fully compact oxide layer with controllable surface properties in optical and aerospace applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A high concentration of a porosification agent would modify the plasma behavior during PE. </LI> <LI> The compactness of the oxide layer was affected by the porosification agent concentration. </LI> <LI> A high concentration of Na<SUB>3</SUB>PO<SUB>4</SUB> leads to excellent electrochemical properties. </LI> </UL> </P>

Electrochemical Response of Al₂O₃-MoO₂-TiO₂ Oxide Films Formed on 6061 Al Alloy by Plasma Electrolytic Oxidation

Kaseem, Mosab,Ko, Young Gun The Electrochemical Society 2016 Journal of the Electrochemical Society Vol.163 No.9

<P>The purpose of this study is to investigate the electrochemical response of Al2O3-MoO2-TiO2 oxide films fabricated on 6061 Al alloy by plasma electrolytic oxidation (PEO). The coatings were fabricated under alternating current conditions using an alkalinesilicate- molybdate electrolyte with TiO2, and the results were compared to those without TiO2. Microstructure observations revealed that when TiO2 was added to the electrolyte, the average size and area fraction of the micro-pores of the oxide layer coated in the electrolyte incorporating TiO2 were respectively smaller. The results of potentiodynamic polarization test in 3.5 wt% NaCl solution clearly indicated that the corrosion resistance of the oxide films was significantly improved by the incorporation of TiO2 particles. High corrosion resistance of the Al2O3-MoO2-TiO2 oxide films was also revealed by impedance tests and analyzed in relation to the equivalent circuit model. (C) 2016 The Electrochemical Society. All rights reserved.</P>

A novel composite system composed of zirconia and LDHs film grown on plasma electrolysis coating: Toward a stable smart coating

Kaseem, Mosab,Ko, Young Gun Elsevier 2018 Ultrasonics sonochemistry Vol.49 No.-

<P><B>Abstract</B></P> <P>A novel composite system composed of zirconia and double hydroxide layers (LDHs) was successfully fabricated on the plasma electrolysis (PE) coating. For this aim, the molybdate-loaded LDHs film grown on the PE film of aluminum alloy was modified additionally by zirconia nanoparticles via a facile dip-coating method. The MoO<SUB>4</SUB> <SUP>2−</SUP> anions which were obtained by anion exchange process from the precursor CeMgAl-LDH film, led to decrease the distance between the flakes of LDHs film where a flower-like structure was successfully developed. Moreover, the inclusion of zirconia helped to decrease the size of pores present in the LDHs films. Accordingly, a superior smart protective film was obtained due to the possible synergetic effects between the MoO<SUB>4</SUB> <SUP>2−</SUP> and Ce<SUP>3+</SUP> ions released from LDHs film as well as the high chemical stability of zirconia. The LDHs film modified by zirconia can be regarded as a stable smart coating, meaning that it has the ability to control the release of corrosion inhibitors and providing an excellent long-term electrochemical performance as well.</P> <P><B>Highlights</B></P> <P> <UL> <LI> LDHs-Mo-Zr film was successfully fabricated onthe porous surface of PE coating. </LI> <LI> ZrO<SUB>2</SUB> was absorbed in the pores of LDHs film, offering a more compact surface. </LI> <LI> The LDHs-Mo-Zr film worked as effective chloride nanotraps. </LI> </UL> </P>