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Chromium doped Ni-Cu-Zn nano ferrites with chemical formula Ni 0.2 Cu 0.2 Zn 0.6 Fe 2-x Cr x O 4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) were prepared by using sol-gel auto combustion method. The prepared precursors of Chromium substituted Ni-CuZn ferrites were sintered at 500 °C for 4h. Compositional stoichiometry were confirmed from EDAX patterns. The XRD data revealed that the all samples possess a single phase cubic spinel structure. The Lattice constant, X-ray density, hopping lengths and crystallite size determined from XRD data decreases with increase in Cr 3+ concentration. The IR spectra show two major absorption bands, high frequency band ν 1 ≈ 600 cm -1 and low frequency band ν 2 ≈ 450 cm -1 attributed to the stretching vibration of tetrahedral and octahedral sites respectively. The surface morphology of the prepared samples was studied by Scanning Electron Microscopy and Transmission Electron Morphology.

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The present study demonstrates the simple and easy synthesis of calcium oxide (CaO) from waste egg’s shells. Fine egg’s shells powder were calcinated at 500, 700 and 800 ºC. The structural and morphological evaluation of calcium oxide derived from waste egg’s shell were examined by using XRD, FT-IR, SEM, EDS and TEM techniques. The sintered calcium oxide was used as heterogeneous catalyst for the synthesis of 5-arylidene malononitrile and 5-arylidene barbituric acid derivatives by the condensation of various aromatic aldehyde and active methylene compounds via Knoevenagel condensations reaction under ultrasound irradiation method. The reaction completed within a very short reaction time with high yields of product. The present method describes easy synthesis of calcium oxide catalyst from the waste egg’s shells, short reaction times, simple product isolation, excellent yield and reusability of the catalyst.

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