41 research outputs found

    Vitaly Ginzburg and High Temperature Superconductivity: Personal Reminiscences

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    I offer some personal reminiscences from the period of 1976-1983, when I was a M. Sc. and then a Ph.D. student in Vitaly L. Ginzburg's High Temperature Superconductivity group at the P.N. Lebedev Institute in MoscowComment: To be published in proceedings of the Notre Dame Workshop on the Possibility of Room Temperature Superconductivity, June 2005 v.2: an apposite epigraph adde

    Composite Electrodes for Electrochemical Supercapacitors

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    Manganese dioxide nanofibers with length ranged from 0.1 to 1 μm and a diameter of about 4–6 nm were prepared by a chemical precipitation method. Composite electrodes for electrochemical supercapacitors were fabricated by impregnation of the manganese dioxide nanofibers and multiwalled carbon nanotubes (MWCNT) into porous Ni plaque current collectors. Obtained composite electrodes, containing 85% of manganese dioxide and 15 mass% of MWCNT, as a conductive additive, with total mass loading of 7–15 mg cm−2, showed a capacitive behavior in 0.5-M Na2SO4 solutions. The decrease in stirring time during precipitation of the nanofibers resulted in reduced agglomeration and higher specific capacitance (SC). The highest SC of 185 F g−1 was obtained at a scan rate of 2 mV s−1 for mass loading of 7 mg cm−2. The SC decreased with increasing scan rate and increasing electrode mass

    Biomimetic strategies for surface modification, dispersion, charging and electrophoretic deposition of materials

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    Composite Fe3O4-MXene-Carbon Nanotube Electrodes for Supercapacitors Prepared Using the New Colloidal Method

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    MXenes, such as Ti3C2Tx, are promising materials for electrodes of supercapacitors (SCs). Colloidal techniques have potential for the fabrication of advanced Ti3C2Tx composites with high areal capacitance (CS). This paper reports the fabrication of Ti3C2TX-Fe3O4-multiwalled carbon nanotube (CNT) electrodes, which show CS of 5.52 F cm−2 in the negative potential range in 0.5 M Na2SO4 electrolyte. Good capacitive performance is achieved at a mass loading of 35 mg cm−2 due to the use of Celestine blue (CB) as a co-dispersant for individual materials. The mechanisms of CB adsorption on Ti3C2TX, Fe3O4, and CNTs and their electrostatic co-dispersion are discussed. The comparison of the capacitive behavior of Ti3C2TX-Fe3O4-CNT electrodes with Ti3C2TX-CNT and Fe3O4-CNT electrodes for the same active mass, electrode thickness and CNT content reveals a synergistic effect of the individual capacitive materials, which is observed due to the use of CB. The high CS of Ti3C2TX-Fe3O4-CNT composites makes them promising materials for application in negative electrodes of asymmetric SC devices

    Deposition of Organic-Inorganic Nanocomposite Coatings for Biomedical Applications

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    Polymethylmethacrylate (PMMA) is a material of choice for many biomedical coating applications. However, such applications are limited due to the toxicity of the traditional solvents used for the solution processing of PMMA coatings and composites. This problem is addressed using an isopropanol-water co-solvent, which allows for the dissolution of high molecular mass PMMA and the fabrication of coatings by a dip-coating method from concentrated PMMA solutions. The use of the co-solvent offers a versatile strategy for PMMA solubilization and coating deposition, despite the insolubility of PMMA in water and isopropanol. Composite coatings are obtained, containing hydroxyapatite, silver oxide, zinc oxide, micron size silica and nanosilica. Such coatings are promising for the manufacturing of implants with enhanced biocompatibility, bioactivity and antimicrobial properties and the fabrication of biosensors. Ibuprofen, tetracycline and amoxicillin are used as model drugs for the fabrication of PMMA-drug composite coatings for drug delivery. The microstructure and composition of the coatings are analyzed. The versatile dip-coating method of this investigation provides a platform for various biomedical applications

    A Versatile Strategy for the Fabrication of Poly(ethyl methacrylate) Composites

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    Poly(ethyl methacrylate) (PEMA) is dissolved in ethanol, known to be a non-solvent for PEMA, due to the solubilizing ability of an added bile acid biosurfactant, lithocholic acid (LA). The ability to avoid traditional toxic and carcinogenic solvents is important for the fabrication of composites for biomedical applications. The formation of concentrated solutions of high molecular weight PEMA is a key factor for the film deposition using the dip coating method. PEMA films provide corrosion protection for stainless steel. Composite films are prepared, containing bioceramics, such as hydroxyapatite and silica, for biomedical applications. LA facilitates dispersion of hydroxyapatite and silica in suspensions for film deposition. Ibuprofen and tetracycline are used as model drugs for the fabrication of composite films. PEMA-nanocellulose films are successfully prepared using the dip coating method. The microstructure and composition of the films are investigated. The conceptually new approach developed in this investigation represents a versatile strategy for the fabrication of composites for biomedical and other applications, using natural biosurfactants as solubilizing and dispersing agents

    Deposition of Organic-Inorganic Nanocomposite Coatings for Biomedical Applications

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    Polymethylmethacrylate (PMMA) is a material of choice for many biomedical coating applications. However, such applications are limited due to the toxicity of the traditional solvents used for the solution processing of PMMA coatings and composites. This problem is addressed using an isopropanol-water co-solvent, which allows for the dissolution of high molecular mass PMMA and the fabrication of coatings by a dip-coating method from concentrated PMMA solutions. The use of the co-solvent offers a versatile strategy for PMMA solubilization and coating deposition, despite the insolubility of PMMA in water and isopropanol. Composite coatings are obtained, containing hydroxyapatite, silver oxide, zinc oxide, micron size silica and nanosilica. Such coatings are promising for the manufacturing of implants with enhanced biocompatibility, bioactivity and antimicrobial properties and the fabrication of biosensors. Ibuprofen, tetracycline and amoxicillin are used as model drugs for the fabrication of PMMA-drug composite coatings for drug delivery. The microstructure and composition of the coatings are analyzed. The versatile dip-coating method of this investigation provides a platform for various biomedical applications
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