University of Madras

About: University of Madras is a education organization based out in Chennai, Tamil Nadu, India. It is known for research contribution in the topics: Ring (chemistry) & Lipid peroxidation. The organization has 8496 authors who have published 11369 publications receiving 211152 citations. The organization is also known as: Madras University & University of Chennai.

A perspective on the biotechnological potential of microalgae.

Abstract: Microalgae are the untapped resource with more than 25,000 species of which only 15 are in use. In recent years, microalgal culture technology is a business oriented line owing to their different p...

Electrical conductivity and dielectric behaviour of nanocrystalline NiFe2O4 spinel

Abstract: Electrical conductivity and dielectric measurements have been performed for nanocrystalline NiFe2O4 spinel for four different average grain sizes, ranging from 8 to 97 nm. The activation energy for the grain and grain boundary conduction and its variation with grain size have been reported in this paper. The conduction mechanism is found to be due to the hopping of both electrons and holes. The high-temperature conductivity shows a change of slope at about 500 K for grain sizes of 8 and 12 nm and this is attributed to the hole hopping in tetrahedral sites of NiFe2O4. Since the activation energy for the dielectric relaxation is found to be almost equal to that of the dc conductivity, the mechanism of electrical conduction must be the same as that of the dielectric polarization. The real part e' of the dielectric constant and the dielectric loss tanδ for the 8 and 12 nm grain size samples are about two orders of magnitude smaller than those of the bulk NiFe2O4. The anomalous frequency dependence of e' has been explained on the basis of hopping of both electrons and holes. The electrical modulus analysis shows the non-Debye nature of the nanocrystalline nickel ferrite.

Magnetic properties of nanostructured ferrimagnetic zinc ferrite

Abstract: Nanostructured ZnFe2O4 ferrites with different grain sizes were prepared by high energy ball milling for various milling times. Both the average grain size and the root mean square strain were estimated from the x-ray diffraction line broadening. The lattice parameter initially decreases slightly with milling and it increases with further milling. The magnetization is found to increase as the grain size decreases and its large value is attributed to the cation inversion associated with grain size reduction. The Fe-57 Mossbauer spectra were recorded at 300 K and 77 K for the samples with grain sizes of 22 and 11 nm. There is no evidence for the presence of the Fe2+ charge state. At 77 K the Mossbauer spectra consist of a magnetically ordered component along with a doublet due to the superparamagnetic behaviour of small crystalline grains with the superparamagnetic component decreasing with grain size reduction. At 4.2 K the sample with 11 nm grain size displays a magnetically blocked state as revealed by the Mossbauer spectrum. The Mossbauer spectrum of this sample recorded at 10 K in an external magnetic field of 6 T applied parallel to the direction of gamma rays clearly shows ferrimagnetic ordering of the sample. Also, the sample exhibits spin canting with a large canting angle, maybe due to a spin-glass-like surface layer or grain boundary anisotropies in the material.

Visible light degradation of textile effluent using novel catalyst ZnO/γ-Mn2O3

Abstract: The novel ZnO/γ-Mn2O3 (various weight percentages) nanocomposite catalysts were prepared by thermal decomposition method and their size, shape, and surface area were characterized by various techniques. Further, the prepared samples were used to degrade methylene blue (MB) and methyl orange (MO) in aqueous medium under visible light irradiation. Finally, the best catalyst was employed to degrade phenol and a textile effluent. The recycling ability and their efficiency of catalyst are discussed in detail.