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Corrosion Protective Conversion Coatings on Magnesium Disk. Using a Hydrothermal Technique

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Journal of Materials Science & Technology 2014年第1期30卷 47-53页

作者： R.k.Gupta k.mensah-darkwa D.k.mar Department of Chemistry Pittsburg State University Engineering Research Center for Revolutionizing Metallic Biomaterials(ERC-RMB) Department of Mechanical EngineeringNorth Carolina A&T State University

A uniform, compact, and well adherent conversion coating of magnesium hydroxide has been formed on bioresorbable magnesium disk. by means of a hydrothermal technique. Electrochemical results indicate that the coating brings about a significant reduction in magnesium corrosion in phosphate buffered saline （PBS） solution. It is also observed that corrosion resistance of the coating increases with an increase in treatment time, which in turn, increases the coating thick.ess. The protective behavior of magnesium hydroxide coating is attributed to its chemical inertness in PBS solution. The coatings are found to be free from pores that reduce the direct contact between corroding media and underlying magnesium.

关键词： Magnesium Polarization Electrochemical impedance spectroscopy (EIS) Scanning electron microscopy (SEM) Conversioncoating Corrosion

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Mechanical and Corrosion Properties of Magnesiume-Hydroxyapatite (MgeHA) Composite Thin Films

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Journal of Materials Science & Technology 2013年第9期29卷 788-794页

作者： k.mensah-darkwa R.k.Gupta D.k.mar Engineering Research Center of Revolutionizing Metallic Biomaterials Department of Mechanical Engineering North Carolina A & T State University Department of Chemistry Pittsburg State University

Magnesium(Mg)-hydroxyapatite(Ca10(PO4)6(OH)2,abbreviated as HA) composite films have been grown on Mg plates using a pulsed laser deposition *** property measurements and analysis have indicated that hardness and Young’s modulus of nMge(100e n)HA composite coatings increase with Mg content in the coatings and reach a maximum at a 70Mge 30HA composition.n and 100e n in the nMge(100e n)HA represent the relative number of laser pulses impinging on Mg and HA targets,*** current potentiodynamic polarization studies have shown that the corrosion of Mg plate(control) decreases with an increase in the HA ratio in the composite *** example,the corrosion current density of Mg plate reduces by w350 times after coating the Mg plate with 10Mge 90HA composite *** reduction in corrosion current density of Mg plates was also accompanied by a positive shift in the corrosion potential(w6%) due to this *** mechanism behind the reduction in corrosion behavior of Mg plates due to nMge(100e n) HA composite coatings has been understood by electrochemical impedance spectroscopy.

关键词： Magnesium Hydroxyapatite Scanning electron microscopy Pulsed laser deposition Corrosion Impedance spectroscopy

Enhanced corrosion resistance of phytic acid coated magnesium by stearic acid treatment

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Transactions of Nonferrous Metals Society of China 2013年第5期23卷 1237-1244页

作者： R.k.GUPTA k.mensah-darkwa J.SANk.R D.k.MAR Engineering Research Center for Revolutionizing Metallic Biomaterials(ERC-RMB) North Carolina A&T State University

A green chemical conversion coating for magnesium was obtained with a phytic acid solution. The microstructure and corrosion properties of phytic acid conversion coated magnesium were further improved by soak.ng in stearic acid solution. The phytic acid conversion coated magnesium after soak.ng in the stearic acid showed no micro-crack. and the surface became very smooth. The corrosion behavior of the uncoated and coated magnesium samples was studied by electrochemical methods. The corrosion resistance of the stearic acid treated sample was much higher than that of phytic acid conversion coated magnesium or uncoated magnesium. The electrochemical results indicated that the stearic acid treated coating provided effective corrosion protection to the magnesium sample.

关键词： magnesium phytic acid stearic acid corrosion impedance spectroscopy

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Evaluation of Fuel Properties of Six Tropical Hardwood Timber Species for Briquettes

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Journal of Sustainable Bioenergy Systems 2014年第1期4卷 1-9页

作者： Stephen J. Mitchual k.asi Frimpong-mensah Nicholas A. darkwa Department of Construction and Wood Technology Education University of Education Winneba Kumasi Campus Kumasi Ghana Department of Wood Science and Technology Kwame Nkrumah University of Science and Technology Kumasi Ghana

The fuel potential of six tropical hardwood species namely: Triplochiton scleroxylon, Ceiba pentandra, Aningeria robusta, Terminalia superba, Celtis mildbreadii and Piptadenia africana were studied. Properties studied included species density, gross calorific value, volatile matter, ash content, organic carbon and elemental composition. Fuel properties were determined using standard laboratory methods. The result indicates that the gross calorific value (GCV) of the species ranged from 20.16 to 22.22 MJ/k. and they slightly varied from each other. Additionally, the GCV of the biomass materials were higher than that of other biomass materials lik.;wheat straw, rice straw, maize straw and sugar cane. The ash and volatile matter content varied from 0.6075 to 5.0407%, and 75.23% to 83.70% respectively. The overall rating of the properties of the six biomass materials suggested that Piptadenia africana has the best fuel property to be used as briquettes and Aningeria robusta the worse. This study therefore suggests that a holistic assessment of a biomass material needs to be done before selecting it for fuel purpose.

关键词： Ash Content Briquette Calorific Value Elemental Composition Species Volatile Matter

Relationship between Physico-Mechanical Properties, Compacting Pressure and Mixing Proportion of Briquettes Produced from Maize Cobs and Sawdust

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Journal of Sustainable Bioenergy Systems 2014年第1期4卷 50-60页

This study examined the relationship between selected physico-mechanical properties, compacting pressure and mixing proportion of briquettes produced from combination of maize cob particles and sawdust of low, medium and high density timber species. Particle sizes of maize cobs and sawdust used for the study were ≤1 mm. The two materials were combined at mixing percentages of 90:10, 70:30 and 50:50 (Sawdust:maize cobs). Briquettes were produced at room temperature (28°C) using compacting pressures 20, 30, 40 and 50 MPa. The results suggested that combining maize cob particles with sawdust of low, medium and high density wood species could significantly enhance the relaxed density, compressive strength in cleft and impact resistance index of briquettes produced from agricultural biomass residue lik. maize cobs. The results further indicated that the physical and mechanical characteristics of briquettes produced from combinations of sawdust of low density species and maize cobs were exceptionally higher than that produced from combinations of maize cob particles, and medium density and high density timber species. The R2 values for the regression model between the independent variables (mixing percentage and compacting pressure) and relaxed density, compressive strength in cleft and impact resistance index of briquettes produced from combinations of maize cob particles and sawdust of low density species (Ceiba pentandra) were 0.966, 0.932 and 0.710 respectively. This study provides a hope for briquetting maize cobs at room temperature using a low compacting pressure.

关键词： Briquette Compacting Pressure Maize Cobs Mixing Proportions Physico-Mechanical Properties Sawdust