Pd-Impregnated NiCo2O4nanosheets/porous carbon composites as a free-standing and binder-free catalyst for a high energy lithium-oxygen battery

Agyeman, Daniel Adjei,Park, Mihui,Kang, Yong-Mook The Royal Society of Chemistry 2017 Journal of Materials Chemistry A Vol.5 No.42

<P>A novel free-standing air electrode with various structural and electrochemical merits was designed for a highly reversible lithium-oxygen battery. Interconnected NiCo2O4nanosheets were grown almost perpendicular to the surface of carbon foam acting as a gas diffusion layer<I>via</I>a hydrothermal method combined with low temperature calcination and then decorated with palladium (Pd). Basically, this novel class of heterostructured catalysts consists of hierarchical nanosheets that can provide enough catalytic surface and open space, which is advantageous for oxygen or lithium ion transfer. In addition, the intrinsic porous structure of carbon foam better facilitates barrier-free oxygen transport and electrolyte penetration, while the introduction of Pd can modify the electronic structure of NiCo2O4, thereby enhancing electron transport all over the electrode. Because Pd incorporation also evolves the surface oxygen vacancies, which helps the discharge product (Li2O2) grow into a flower-like form, its formation or decomposition in the free-standing Pd@NiCo2O4electrode could be rendered extremely reversible, finally realizing low charge over-potential, high discharge capacity (the maximum capacity reaches about 4000 mA h g<SUP>−1</SUP>) and long cycle life (extremely stable cyclic retention almost up to 100 cycles under the capacity limitation of 1000 mA h g<SUP>−1</SUP>).</P>

Does the polarity of radial head arthroplasty affect functional outcomes? A systematic review and meta-analysis

Kofi Agyeman,Arya Minaie,Seth D. Dodds 대한견주관절학회 2024 대한견주관절의학회지 Vol.27 No.2

Background: Radial head arthroplasty allows a high degree of customizability, and implant polarity has emerged as an important variable. The purpose of this meta-analysis was to evaluate differences in functional and clinical outcomes between patients receiving monopolar and bipolar radial head prosthetic implants. Methods: A systematic review and meta-analysis were employed, and 65 articles were identified in three databases. Twelve articles contained non-English or insufficient text and were consequently excluded, and 20 others did not contain sufficient data or follow-up. The remaining 33 articles were qualitatively and quantitatively reviewed. Results: In total, 33 populations were identified, with 809 unduplicated patients: 565 with monopolar and 244 with bipolar implants. In these respective patients, the mean follow-up was 40.2 and 56.9 months. Average Mayo Elbow Performance Score were 86.7 and 87.4 (P=0.80), respectively; average Disability of the Arm, Shoulder, and Hand scores were 17.9 and 14.7 (P=0.47), and average final flexion/extension arcs were 119.4° and 118.7° (P=0.48). Revision rates were 4.07% and 6.56%, while complication rates were 19.65% and 20.08% in the respective monopolar and bipolar patients. These increased relative risks associated with bipolar implants were not significant. Conclusions: Radial head implant polarity does not appear to affect functional outcomes. While bipolar prosthetic design may increase the risks of revision and complications, the increases were not significant. Level of evidence: IV.

Characterization of some selected Ghanaian clay minerals for potential industrial applications

B. Onwona-Agyeman,N. Lyczko,D. P. Minh,A. Nzihou,A.Yaya 한양대학교 세라믹연구소 2020 Journal of Ceramic Processing Research Vol.21 No.1

The aim of this work was to study five (5) selected local raw clay materials from Ghana using different characterizationtechniques such as Thermogravimetric/Differential Thermal Analysis (TG/DTA), X-ray diffraction (XRD), Fourier TransformInfra-red Spectroscopy (FTIR), Scanning Electron Microscopy equipped with Energy Dispersive X-ray Spectroscopy (SEMEDX)and Nitrogen Desorption (Brunauer-Emmett-Teller, BET) specific surface area analysis. The clay samples studied are;Nkroful kaolin (NK), Amanfrom kaolin (AK), Ball clay (BC), Akyem Feldspar (AF) and Akwatia silica (AS). SEM and EDXshow the morphological features of the five clay samples and also confirm the presence of some dominant elementalcompositions such as aluminium and silicon in all the samples. FTIR show that the vibrations spectra in the region around3,600-3,700 cm−1 and 700-800 cm−1 are due to M-OH groups and that at 900-1000 cm−1 corresponds to Si-O-Si modes. BETanalysis gives specific surface area of the clay samples as NK (4.6 m2/g), AK (21.9 m2/g), BC (25.50 m2/g), AS (0.79 m2/g) andAF (0.49 m2/g). X-ray diffraction pattern confirm the presence of quartz as the major reflection in all the samples analysedand only kaolinite reflections appeared in three of the samples (NK, AK and BC). All the kaolinite clays (NK, AK and BC)are suitable starting materials for the fabrication of electroporcelain insulators, catalytic converters and diesel particulate filters.

Polydopamine-induced surface functionalization of carbon nanofibers for Pd deposition enabling enhanced catalytic activity for the oxygen reduction and evolution reactions

Tamakloe, Wilson,Agyeman, Daniel Adjei,Park, Mihui,Yang, Junghoon,Kang, Yong-Mook The Royal Society of Chemistry 2019 Journal of Materials Chemistry A Vol.7 No.13

<P>A detailed understanding of the surface modification or coating of materials is becoming more important for the design and development of hybrid materials for their advanced applications. The characteristics of polydopamine-coated surfaces were explored by varying dopamine concentration and polymerization time for noble metal deposition, which is a key for the development of advanced catalysts. The variation of these parameters for dopamine coating on carbon nanofibers (CNFs) finally modulated the amount of palladium (Pd) nanoparticles deposited on the dopamine-coated surface, which is CNFs. The results showed that the higher the dopamine concentration, the larger the amount of deposited Pd, while the polymerization time is inversely proportional to the amount of Pd deposited. Thereby, the optimally functionalized surface for Pd deposition was found with a dopamine concentration of 3 mg mL<SUP>−1</SUP> and a reaction time of 6 hours (PDAT1). This optimum Pd/CNF hybrid material showed very promising electrochemical and catalytic performances with a high discharge capacity of about 5.26 mA h cm<SUP>−2</SUP> which could be maintained up to the 67th cycle at a cut-off capacity of 0.2 mA h cm<SUP>−2</SUP> in non-aqueous Li-O2 batteries and an impressive catalytic activity for the oxygen reduction reaction <I>via</I> the preferred 4 electron pathway in aqueous electrolyte.</P>

A Review of the Design Strategies for Tailored Cathode Catalyst Materials in Rechargeable Li-O2 Batteries

Song, K.,Agyeman, D. A.,Jung, J.,Jo, M. R.,Yang, J.,Kang, Y. M. LASER PAGES PUBLISHING LTD 2015 Israel Journal of Chemistry Vol.55 No.5

CNT@Ni@Ni-Co silicate core-shell nanocomposite: a synergistic triple-coaxial catalyst for enhancing catalytic activity and controlling side products for Li-O₂ batteries

Li, Ziwei,Yang, Junghoon,Agyeman, Daniel Adjei,Park, Mihui,Tamakloe, Wilson,Yamauchi, Yusuke,Kang, Yong-Mook The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.22

<P>A great challenge in the application of carbon-based materials to Li-O2 batteries is to prevent the formation of carbonate-based side products, thereby extending the cycle life of Li-O2 batteries. Herein, for the first time, CNT@Ni@NiCo silicate core-shell nanocomposite is designed and used as a cathode catalyst in Li-O2 batteries. This nanocomposite shows a promising electrochemical performance with a discharge capacity of 10 046 mA h gcat<SUP>−1</SUP> and a low overpotential of 1.44 V at a current density of 200 mA gcat<SUP>−1</SUP>, and it can sustain for more than 50 cycles within the voltage range of 2-4.7 V. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) characterizations prove that the formation of Li2CO3 and other side products are prevented, likely due to the encapsulation of CNTs by NiCo silicates and Ni nanoparticles, which may help decompose the side products. Finally, the synergistic effects, which are contributed by the high electrical conductivity of CNTs, high surface area, the high oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities of NiCo silicate, and the simple decomposition of side products by Ni nanoparticles enable outstanding performance of the CNT@Ni@NiCo silicate core-shell nanocomposite as a cathode catalyst for Li-O2 batteries.</P>

Alabama Forest Products and the Potential Impacts of FTAA Price Changes

Mostafa Malki,Osei-Agyeman Yeboah,Henry Thompson 세종대학교 경제통합연구소 2010 Journal of Economic Integration Vol.25 No.1

The Free Trade Area of the Americas FTAA will increase import competition for some forest product industries in Alabama but create export opportunities for others. Forest products loom large in the Alabama economy, both in terms of income and pollution. The present paper gauges the potential impacts of a range of price changes for forest products in an applied specific factors model of production. Pollution adjusts with forest product outputs. The potential impacts on outputs, capital returns, and pollution are substantial. Anticipated price changes also raise the wage and lower energy demand.

A Specific Factor Model of FTAA and North Carolina Textile and Apparel Industries

Mostafa Malki,Henry Thompson,Osei-Agyeman Yeboah 한국국제경제학회 2009 International Economic Journal Vol.23 No.2

Textile and apparel industries in the US face import competition that promises to increase under the Free Trade Area of the Americas. The present paper utilizes a specific factors model of production and trade to predict the potential impact of FTAA on the textile and apparel industries in North Carolina. Income is redistributed across six labor skill groups in North Carolina, and returns to capital in textiles and apparel fall as does output. In spite of falling prices for textiles and apparels, the model predicts higher wages based on rising prices of other products.

Alabama Forest Products and the Potential Impacts of FTAA Price Changes

( Henry Thompson ),( Mostafa Malki ),( Osei Agyeman Yeboah ) 세종대학교 경제통합연구소 (구 세종대학교 국제경제연구소) 2010 Journal of Economic Integration Vol.25 No.1

The Free Trade Area of the Americas FTAA will increase import competition for some forest product industries in Alabama but create export opportunities for others. Forest products loom large in the Alabama economy, both in terms of income and pollution. The present paper gauges the potential impacts of a range of price changes for forest products in an applied specific factors model of production. Pollution adjusts with forest product outputs. The potential impacts on outputs, capital returns, and pollution are substantial. Anticipated price changes also raise the wage and lower energy demand.

Genetic Variability of Cassava Progenies Developed through Introgression of Cassava Mosaic Disease Resistance into Ghanaian Landraces

Manu-Aduening, Joseph Akwasi,Peprah, Bright Boakye,Agyeman, Adelaide 한국작물학회 2013 Journal of crop science and biotechnology Vol.16 No.1

Availability of genetic diversity is important in selecting suitable cultivars for crop improvement. Progenies of crosses between 19 farmer-preferred cassava landraces and Cassava Mosaic Disease (CMD)-resistant cultivar TME 11 were evaluated and compared with their maternal parents to assess their genetic variability and genetic gains based on CMD tolerance, some growth variables and root yield. The combined analysis of variance for the traits showed significant genotypic differences amongst the progenies and the parents. Apart from a few instances, the differences in replications and years were also significant. Genetic variability components showed high heritability ranging from 92.3 to 99.6% and moderately high genetic gains of 54.1 to 99.6% for the parental cultivars. Apart from canopy spread and plant height, heritability and genetic gains of the progenies were slightly lower than the parents indicating high variability within families of the progenies. The phenotypic coefficient of variation was slightly greater than genotypic coefficient of variation indicating minimal influence of environment on the genotypes. For most of the characters evaluated, the mean performance of the progenies was higher than their corresponding parental lines. Although the genotypes differed significantly (P < 0.001) for all traits evaluated, cultivars such as Afebankye, Bosome nsia, Cedi bankye, 262 Debor, Kwadaso 25, Nkaakom 57 and Sisipe were found to constitute a pool of germplasm with adequate variability. The negative correlation between CMD incidence and other traits evaluated showed significant progress made in the breeding program.