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Electrodeposition mechanism of palladium nanotube and nanowire arrays.
Cherevko, Serhiy,Fu, Jie,Kulyk, Nadiia,Cho, Sung Min,Haam, Seungjoo,Chung, Chan-Hwa American Scientific Publishers 2009 Journal of Nanoscience and Nanotechnology Vol.9 No.5
<P>Palladium nanotube and nanowire arrays were fabricated by electrodeposition into anodic alumina oxide (AAO) templates. By using alumina templates with different pore sizes and hole mouth morphologies, nanotubes with various diameters and lengths were obtained. The mechanism of nano-structure formation was studied by analyzing the current-time curves. It was found that the time needed for the transformation of the nanostructure from a tube to a wire depends on the size and structure of the template. However, the overall behaviour of the current-time transient is similar and can be divided into four main stages, which provides a powerful in-situ method to control nanotube-nanowire transition during growth. The palladium nanotube arrays have a polycrystalline structure, but a preferred orientation along the (110) direction was observed for the arrays of nanowires. Moreover, the degree of texture increases with decreasing alumina pore size.</P>
Cherevko, Serhiy,Kulyk, Nadiia,Chung, Chan-Hwa American ChemicalSociety 2012 Langmuir Vol.28 No.6
<P>Electrodeposition of high-surface-area nanoporous Au-Cu foams under conditions of hydrogen codeposition is studied. The honeycomb-like AuxCu100-x foams with 0 <= x <= 100 are electrodeposited by controlling the amount of corresponding ions in the solution. The amount of metal ions in deposited films follows that in used electrolytes. Compared to monometallic foams, the AuxCu100-x structures are characterized by smaller ligament or particle sizes (less than 10 nm) and improved stability. The addition of even a small amount of Cu to the Au matrix is found to dramatically improve the stability of the structure in air environment or an acidic medium. Pt@AuxCu100-x structures are formed by the galvanic displacement of Cu from AuxCu100-x templates. During the displacement of Cu by Pt, Au serves as a buffer, decreasing mechanical stresses and preventing the detachment of the foam from the substrate. The surface ratio of Pt to Au atoms is controlled by adjusting the amount of Cu in the template. Pt@AuxCu100-x electrodes are investigated as novel electrocatalysts for methanol oxidation in alkaline media. The Au-enriched surfaces show higher catalytic activity toward methanol oxidation, while the electrodes with a higher amount of Pt are more stable.</P>
Cherevko, Serhiy,Kulyk, Nadiia,Chung, Chan-Hwa The Royal Society of Chemistry 2012 Nanoscale Vol.4 No.1
<P>High surface area Pd foams with roughness factors of more than 1000 and a specific surface area of 60 m(2) g(-1) are obtained by electrodeposition. The foams are composed of dendrites with branches on the 10 nm scale. The resulting electrodes show high activity towards the oxidation of C(2) alcohols.</P>
Cherevko, Serhiy,Kulyk, Nadiia,Chung, Chan-Hwa The Royal Society of Chemistry 2012 Nanoscale Vol.4 No.2
<P>Hydrogen evolution assisted electrodeposition is a new bottom-up technique allowing the fast and simple synthesis of nanometals. Electrochemical dealloying is a top-down approach with the same purpose. In this work, we show that a combination of these two methods in sequence by pulse-reverse electrodeposition can be used to prepare high-surface-area nanostructured metals. Highly porous adherent platinum is obtained by the deposition of CuPt alloy during the cathodic cycles and the selective dissolution of copper during the anodic cycles. The convection created by the movement of the hydrogen bubbles increases the deposition rate and removes the dissolved copper ions from the diffusion layer, which ensures the deposition of a film with the same stoichiometry throughout the whole process. Due to the relatively high ratio of copper atoms on the surface in the as-deposited layer, it is proposed that the dealloying kinetics is significantly higher than that usually observed during the dealloying process in a model system. The proposed approach has several advantages over other methods, such as a very high growth rate and needlessness of any post-treatment processes. A detailed analysis of the effect of pulse-reverse waveform parameters on the properties of the films is presented. Mesoporous platinum with pores and ligaments having characteristic sizes of less than 10 nm, an equivalent surface area of up to ca. 220 m(2) cm(-3), and a roughness factor of more than 1000 is fabricated.</P>
Characterization of FePt film electrodeposited with a ferric electrolyte
Serhiy Cherevko,Jie Fu,Ki Youn Song,Chan-Hwa Chung 한국화학공학회 2009 Korean Journal of Chemical Engineering Vol.26 No.6
The electrodeposition of FePt alloy film in a novel ferric electrolyte that could be an alternative electrolyte to the usual non-stable baths was investigated. The influence of the applied current density and electrolyte temperature on the composition of the alloy was studied. It was found that co-deposition of oxygen can be reduced by deposition at higher temperature of 65℃ than room temperature. The as-deposited film had a face-centered cubic (γ-Fe,Pt) structure, and after an additional annealing process, the structure was changed to a face-centered tetragonal structure. The as-deposited FePt film also shows good resistance to corrosion and its coercivity was about 0.1T, which makes it suitable for use in applications compatible with silicon technology.
Using The Internet As A Tool For The Illicit Sale Of Drugs And Potent Substances
Manzhai, Oleksandr,Cherevko, Kyrylo,Chycha, Ruslan,Burlaka, Iryna,Piadyshev, Volodymyr International Journal of Computer ScienceNetwork S 2022 International journal of computer science and netw Vol.22 No.6
The article analyzes the regulations of current criminal law and current issues, combating drug crime on the Internet, as well as measures to combat drug crime in the field of modern information technology. In connection with the growth of crimes in the field of drug trafficking committed with the use of information and telecommunications technologies, the urgent task of the state is to find effective ways to reduce drug crime. The article considers criminologically significant aspects of the mechanism of illicit drug trafficking, which is carried out with the use of information and telecommunication technologies and means of remote communication.
Boiko, Olha,Oborska, Svitlana,Kyrylenko, Kateryna,Cherevko, Svitlana,Lebid, Olha,Kulko, Viktoriia International Journal of Computer ScienceNetwork S 2021 International journal of computer science and netw Vol.21 No.4
The article proposes the process of formation of the teacher's innovative competence in the space of lifelong education the foundations of the formation of the teacher's innovative competence in the space of continuous education. The concept of the formation of the teacher's innovative competence in the space of lifelong education is proposed; it includes initial ideas, goals, objectives, patterns, principles, stages, content and technologies implementation of this process.