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Author

B. Luan

Bio: B. Luan is an academic researcher from National Research Council. The author has contributed to research in topics: Alloy & Coating. The author has an hindex of 25, co-authored 42 publications receiving 3824 citations. Previous affiliations of B. Luan include University of Western Ontario & University of Science and Technology Beijing.
Topics: Alloy, Coating, Corrosion, Electrode, Magnesium alloy

Papers
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Journal ArticleDOI
TL;DR: In this paper, the state of the art in coating and surface modification technologies, applied to magnesium-based substrates for improved corrosion and wear resistance, are discussed, including electrochemical plating, conversion coatings, anodizing, gas phase deposition processes, laser surface alloying/cladding and organic coatings.

2,240 citations

Journal ArticleDOI
TL;DR: In this article, the state of the art in coating and surface modification technologies, applied to magnesium-based substrates for improved corrosion and wear resistance, are discussed, including electrochemical plating, conversion coatings, anodizing, gas phase deposition processes, laser surface alloying/cladding and organic coatings.
Abstract: Magnesium and its alloys have excellent physical and mechanical properties for a number of applications. In particular its high strength:weight ratio makes it an ideal metal for automotive and aerospace applications, where weight reduction is of significant concern. Unfortunately, magnesium and its alloys are highly susceptible to corrosion, particularly in salt-spray conditions. This has limited its use in the automotive and aerospace industries, where exposure to harsh service conditions is unavoidable. The simplest way to avoid corrosion is to coat the magnesium-based substrate to prevent contact with the environment. This review details the state of the art in coating and surface modification technologies, applied to magnesium based substrates for improved corrosion and wear resistance. The topics covered include electrochemical plating, conversion coatings, anodizing, gas-phase deposition processes, laser surface alloying/cladding and organic coatings.

320 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of electrical parameters including frequency and duty cycle on the microdischarge behavior and coating growth was investigated at constant current, and a new conceptual model was proposed to explain the concentration distribution of Si on the surface of coatings prepared at different duty cycles.
Abstract: Ceramic coatings were created on the surface of 6061 aluminum alloy using a plasma electrolytic oxidation (PEO) process employing a pulsed direct current (DC) power mode in an alkaline electrolyte. The effect of electrical parameters including frequency and duty cycle on the microdischarge behavior and coating growth was investigated at constant current. Surface features of coatings were studied using scanning electron microscopy. Energy dispersive spectroscopy was employed to investigate elemental distribution on the coating surfaces and cross-sections. Applying lower duty cycles was found to result in increased breakdown voltages and microdischarges with higher spatial density and lower intensity. Further, applying a lower duty cycle was also found to promote the uniformity of silicon distribution in the coating. Based on these new findings, a new conceptual model is proposed to explain the concentration distribution of Si on the surface of coatings prepared at different duty cycles.

203 citations

Journal ArticleDOI
TL;DR: In this article, the effect of electrical parameters including pulse frequency, duty cycle and current density on phase formation in the coatings was revealed using conventional and glancing angle X-ray diffraction.
Abstract: Oxide coatings were produced on a 6061 aluminum alloy using a pulsed unipolar plasma electrolytic oxidation (PEO) process. The effect of electrical parameters including pulse frequency, duty cycle and current density on phase formation in the coatings was revealed using conventional and glancing angle X-ray diffraction. The results show that PEO coatings are mainly composed of γ-Al2O3. Depending on the electrical parameters employed, the coatings can also contain α-Al2O3 and mullite with varying concentrations. Higher current densities and higher duty cycle were found to favor the formation of mullite. Under the experimental conditions used, the ratio of the integrated XRD peaks for α- and γ-Al2O3 varied from 0 to about 0.6, indicating that the relative content of α-Al2O3 in the PEO coatings varied over a wide range. Longer pulse on-times and higher current densities promoted the gamma to alpha-alumina phase transformation. Depth profiling of PEO ceramic coatings using glancing angle XRD with different incident beam angles revealed that mullite was more concentrated in the top surface of the coatings. No significant variation in α-Al2O3 concentration across the coatings could be concluded in this study, unlike the results of some other studies.

116 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of two electroless nickel bath stabilizers, thiourea and maleic acid, were investigated in terms of surface morphology, microstructure, phase, and composition.

92 citations


Cited by
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Journal ArticleDOI
TL;DR: A review of the properties, biological performance, challenges and future directions of magnesium-based biomaterials can be found in this paper, where the authors explore the properties and challenges of magnesium biomaterial.

3,757 citations

Journal ArticleDOI
28 Jan 2011-ACS Nano
TL;DR: Graphene films grown by chemical vapor deposition are demonstrated for the first time to protect the surface of the metallic growth substrates of Cu and Cu/Ni alloy from air oxidation, allowing pure metal surfaces only one atom away from reactive environments.
Abstract: The ability to protect refined metals from reactive environments is vital to many industrial and academic applications. Current solutions, however, typically introduce several negative effects, including increased thickness and changes in the metal physical properties. In this paper, we demonstrate for the first time the ability of graphene films grown by chemical vapor deposition to protect the surface of the metallic growth substrates of Cu and Cu/Ni alloy from air oxidation. In particular, graphene prevents the formation of any oxide on the protected metal surfaces, thus allowing pure metal surfaces only one atom away from reactive environments. SEM, Raman spectroscopy, and XPS studies show that the metal surface is well protected from oxidation even after heating at 200 °C in air for up to 4 h. Our work further shows that graphene provides effective resistance against hydrogen peroxide. This protection method offers significant advantages and can be used on any metal that catalyzes graphene growth.

1,190 citations

Journal ArticleDOI
TL;DR: There remains growing interest in magnesium (Mg) and its alloys, as they are the lightest structural metallic materials Mg alloys have the potential to enable design of lighter engineered systems, including positive implications for reduced energy consumption as mentioned in this paper.

1,173 citations

Journal ArticleDOI
TL;DR: The analysis of the literature showed that many studies have focused on calcium phosphate coatings produced either using conversion or deposition methods which were developed for orthopaedic applications, however, the control of phases and the formation of cracks still appear unsatisfactory.

1,042 citations

Posted Content
TL;DR: In this paper, the ability of graphene films grown by chemical vapor deposition to protect the surface of the metallic growth substrates of Cu and Cu/Ni alloy from air oxidation was demonstrated.
Abstract: The ability to protect refined metals from reactive environments is vital to many industrial and academic applications. Current solutions, however, typically introduce several negative effects, including increased thickness and changes in the metal physical properties. In this paper, we demonstrate for the first time the ability of graphene films grown by chemical vapor deposition to protect the surface of the metallic growth substrates of Cu and Cu/Ni alloy from air oxidation. SEM, Raman spectroscopy, and XPS studies show that the metal surface is well protected from oxidation even after heating at 200 \degree C in air for up to 4 hours. Our work further shows that graphene provides effective resistance against hydrogen peroxide. This protection method offers significant advantages and can be used on any metal that catalyzes graphene growth.

992 citations