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Size dependent structural and magnetic behaviour of CaFe2O4
Arvind Samariya,S.N. Dolia,Arun S. Prasad,P.K. Sharma,S.P. Pareek,M.S. Dhawan,Sudhish Kumar 한국물리학회 2013 Current Applied Physics Vol.13 No.5
CaFe2O4 nanocrystalline powders were synthesized through solegel treatment in which the stoichiometric mixing of various nitrates involving calcium and iron in presence of citric acid was performed. Subsequently, the as prepared sample was annealed at various temperatures in order to obtain the fine distribution of size including the bulk counterpart. The samples were then characterized using powder X-ray diffraction followed by 57Fe Mössbauer spectroscopy, SQUID as well as vibrating sample magnetometry. The results of spectroanalyses revealed that the samples were formed in single phase cubic spinel structure and exhibits room temperature superparamagnetism, except the bulk one, which crystallizes in characteristic orthorhombic structure of CaFe2O4 and displays trivial coercivity and remanent magnetization at room temperature.
Sangeeta Kalal,Pinki Bala Punjabi,Narendra Pal Singh Chauhan,Noopur Ameta,Rakshit Ameta,Sudhish Kumar 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.12
The heterogeneous photo-Fenton like process is a green chemical pathway. It has an edge over conven-tional Fenton and photo-Fenton processes as it does not require the removal of ferrous/ferric ions in the form of sludge. We prepeared copper pyrovanadate or Volborthite (Cu3V2(OH)2O7·2H2O) composite photocatalyst by wet chemicalmethod. The photocatalyst was characterized by SEM, XRD, IR, TGA/DSC, EDX and BET. Experiments demon-strated that catalyst could effectively catalyze degradation of neutral red and azure-B in presence of H2O2 in visiblelight. Moreover, the photo-Fenton-like catalytic activity of Cu3V2(OH)2O7·2H2O was much higher than CuO and V2O5,when used alone as photocatalyst. The effect of variation of different parameters, i.e., pH, amount of photocatalyst,concentration of dye, amount of H2O2 and light intensity was also investigated. The degradation was well fitted underpseudo-first-order reaction with a rate constant of 2.081×10−4sec−1and 3.876×10−4sec−1for neutral red and azure-B,respectively. Quality parameters of dye solutions before and after photo-Fenton degradation were also determined. Atentative mechanism involving•OH radical as an oxidant has been proposed. The high catalytic activity may be dueto the Cu3V2(OH)2O7·2H2O shell, which not only increased the surface hydroxyl groups, but also enhanced the interfacialelectron transfer. The catalyst has been found to possess good recyclability.