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Microstructural Evolution and Mechanical Properties of Misch Metal Added Mg-Si Alloys
K. K. Ajith Kumar,U. T. S. Pillai,B. C. Pai,M. Chakraborty 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.6
Effect of misch metal additions (0.3, 0.6, 0.9 and 1.2 wt%) on the refinement of Mg2Si phase in Mg-1.15Si alloy has been studied and compared with the base alloy. MM addition effectively refines the microstructure by breaking the α-Mg halos and lamellar eutectic phase and the maximum refinement is obtained for 0.6 MM addition. For higher MM additions (0.9 and 1.2 wt%), the refinement effect gets reduced and the formation of RE-Si compound is dominated. Improved tensile properties are obtained with the addition of MM and are attributed to the refinement of microstructure and the presence RE-Si compound. The tensile properties obtained are correlated with the microstructure and mirofractomechnisms.
Pillai, K. Chandrasekara,Muthuraman, G.,Moon, Il-Shik Academic Press 2018 Journal of Colloid and Interface Science Vol. No.
<P><B>Abstract</B></P> <P>Electrocatalytic dechlorination mediated by micelle-solubilized electrocatalysts has attracted considerable current interest for pollutant degradation. Aggregation in micellar assemblies and their interactions with the additives in solution are affected by the surfactant structure. By choosing appropriate surfactant molecules, the system properties may be altered to achieve enhanced dechlorination efficiency. Cetyltrimethylammonium bromide-based surfactants with different hydrocarbon lengths and headgroup structures were studied for their structural effects on [Co(I)(bipyridine)<SUB>3</SUB>]<SUP>+</SUP>-mediated dechlorination reactions. A widely used pollutants allyl chloride derivatives were studied as the substrates. The performance of the surfactants towards various dechlorination reactions was evaluated by cyclic voltammetry (CV) based on the catalytic efficiency. Key micellar parameters were determined by CV and rotating disc electrode using [Co(II)(bipyridine)<SUB>3</SUB>]<SUP>2+</SUP> as the micelle-solubilized redox probe. The surfactants affected the dechlorination reaction to different extents, correlating well with their structure. The catalytic efficiency was explained by the interactions of the Co(II)/Co(I) with the surfactant hydrophobic tail and headgroup. This is the first report <I>quantitatively</I> linking the performance of the surfactants in dechlorination reactions with their molecular structure, showing that is possible to use variant surfactant structures to tune the micellar properties for their application towards the enhanced dechlorination of organic pollutants. Substrate structure-susceptibility to reduction relationships were also discussed.</P> <P><B>Graphical abstract</B></P> <P>A good <I>quantitative</I> correlation has been revealed between the catalytic efficiency for CTAB, TDTAB, and CBDAC surfactants towards electrolytic mediated dechlorination reactions and their structure-dependent micellar parameters for the first time.</P> <P>[DISPLAY OMISSION]</P>
( K. Chandrasekara Pillai ),( A. Senthil Kumar ),문일식 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1
Despite the unparalleled extensive use of ruthenium dioxide (RuO<sub>2</sub>), in both crystalline and amorphous forms, in a wide range of electrochemical applications, the intrinsic electron-transfer (ET) rate constant estimations at RuO<sub>2</sub> electrodes prepared at different temperatures are not reported in detail. In this paper, the ET rate constants for RuO<sub>2</sub> electrodes are estimated by rotating disk electrode (RDE) technique using an oxide-sensitive, non-interacting Fe<sup>3+</sup>/Fe<sup>2+</sup> redox probe. Chemically modified RuO<sub>2</sub> electrodes using oxide powders assembled on Pt support using polyvinylchloride binder are used. RuO2 powders prepared at five temperatures, 300 to 700°C, are studied to investigate the dependence of ET activity of electrodes on the oxide preparation temperature.
Pillai, K. Chandrasekara,Muthuraman, G.,Moon, Il-Shik Elsevier 2017 ELECTROCHIMICA ACTA Vol.232 No.-
<P><B>Abstract</B></P> <P>Epichlorohydrin (ECH) is a volatile organic compound and toxic to human health. Here we investigated clean mediated electrocatalytic dechlorination of ECH in aqueous solutions using electrogenerated [Nickel(I)(hexamethylcyclam)]<SUP>+</SUP> ([Ni(I)(hmc)]<SUP>+</SUP>) at glassy carbon cathode. Ni(II)/Ni(I) redox behavior of [Ni(II)(hmc)]<SUP>2+</SUP>, examined first by cyclic voltammetry in ECH free-aqueous solutions of various anions (Cl<SUP>−</SUP>, Br<SUP>−</SUP>, ClO<SUB>4</SUB> <SUP>−</SUP>, SO<SUB>4</SUB> <SUP>2−</SUP>, phosphate, NO<SUB>3</SUB> <SUP>−</SUP>), showed only Cl<SUP>−</SUP> could provide most stable and reactive low-valent nickel species with highest versatility toward activation of ECH dechlorination. Cyclic voltammetry experiments over a range of scan rates and ECH concentrations elucidated rate limiting mechanism for Ni(I) catalyzed ECH dechlorination, and estimated catalytic reaction rate constant (<I>k</I> <SUB>cat</SUB>). ECH concentration-dependent <I>k</I> <SUB>cat</SUB> and <I>i</I> <SUB>cat</SUB> results revealed ECH dechlorination by Ni(I) followed Michaelis-Menten type <I>inner-sphere</I> electron transfer kinetics at low ECH concentrations (< 20mM), but <I>outer-sphere</I> mechanism at higher concentrations. Interestingly, GC/MS showed complete destruction of ECH and production of three non-chloro products within 3-h bulk electrolysis. A possible mechanism was proposed for the overall Ni(I)(hmc)-catalyzed ECH dechlorination. Fast mediation kinetics, total removal of ECH, non-chloro organics as the only dechlorination products, and highly stable [Ni(I)(hmc)]<SUP>+</SUP> mediator indicate electrocatalytic mediation using [Ni(I)(hmc)]<SUP>+</SUP> in aqueous NaCl solution may be feasible for dechlorination of other organic chloro compounds.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Redox studies of Ni(II)/Ni(I) of hexamethylcyclam in aqueous media of different electrolytes for reversibility </LI> <LI> Electrogenerated [Ni(I)(hexamethylcyclam)]<SUP>+</SUP> strongly catalyzes epichlorohydrin dechlorination in aqueous media only with NaCl electrolyte </LI> <LI> Catalytic reaction rate constant estimation and elucidation of reaction mechanism </LI> <LI> Ni(I)-catalyzed epichlorohydrin dechlorination completely removes epichlorohydrin and produces only non-chloro products </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Mediated electrocatalytic dechlorination of epichlorohydrin pollutant by [Ni(I)(hmc)]<SUP>+</SUP> affords total removal of ECH with the production of three non-chloro organics as the only reduction products with fast dechlorination kinetics.</P> <P>[DISPLAY OMISSION]</P>
Chandrasekara Pillai, K.,Raju, T.,Chung, Sang Joon,Moon, Il-Shik John Wiley Sons, Ltd. 2009 Journal of chemical technology and biotechnology Vol.84 No.3
<P>BACKGROUND: Hydrogen sulfide (H<SUB>2</SUB>S) from industrial activities and anaerobic manure decomposition in commercial livestock animal operations is an offensive malodorous and toxic gas even in small concentrations, causing serious discomfort and health and social problems. The objective of this study was to employ for the first time a novel, attractive, low cost, environmentally benign mediated electrochemical oxidation (MEO) process with Ce(IV) as the redox catalyst for H<SUB>2</SUB>S gas removal from an H<SUB>2</SUB>S–air feed mixture.</P><P>RESULTS: The influence of liquid flow rate (Q<SUB>L</SUB>) from 2–4 L min<SUP>−1</SUP>, gas flow rate (Q<SUB>G</SUB>) from 30–70 L min<SUP>−1</SUP>, H<SUB>2</SUB>S concentration in the H<SUB>2</SUB>S–air feed mixture from 5–15 ppm, and Ce(III) pre-mediator concentration in the electrochemical cell from 0.1–1 mol L<SUP>−1</SUP> on H<SUB>2</SUB>S removal efficiency were investigated. Both liquid and gas flow rates influenced the removal efficiencies, but in opposite directions. Nearly 98% H<SUB>2</SUB>S removal was achieved when the concentration of Ce(IV) mediator ion in the flowing scrubbing liquid reached 0.08 mol L<SUP>−1</SUP>.</P><P>CONCLUSIONS: The new MEO method proved promising for H<SUB>2</SUB>S removal, achieving high removal efficiency. Integration of the electrochemical cell with the scrubber set-up ensured continuous regeneration of the mediator and its repeated reuse for H<SUB>2</SUB>S removal, avoiding use of additional chemicals. Since the process works at room temperature and atmospheric pressure utilizing conventional transition metal oxide electrodes more commonly used in industrial applications, it is also safe and economical. Copyright © 2008 Society of Chemical Industry</P>