Preparation of CrO2 nanoparticles via oxidation method

Nanoparticles of CrO2 were obtained by oxidation method under high pressure of oxygen with raw materials of Cr(OH)(3)center dot 1.1H(2)O in a closed system. Reaction temperature, time and initial oxygen pressure were 350 degrees C, 10 min and 6 MPa, respectively. The sizes of nanoparticles were from 55 nm to 89 nm, and the magnetization (Ms) of the nanosized CrO2 was 35.522 emu/g. The specific surface area of Cr(OH)(3)center dot 1.1H(2)O was 124 m(2)/g after ball milling method and the sizes of particles were very small. Very small particles of the precursor Cr(OH)(3)center dot 1.1H(2)O led to the formation of CrO2 nanoparticles under the preparation conditions of CrO2. The phase purity and composition were verified by X-ray technique, and the microstructure was observed by field emission scanning electron microscope. Among the four factors influencing the sizes of CrO2, the degree sequence was arranged as follows: reaction temperature > mass of H2O > initial pressure of O-2 > reaction time. (C) 2012 Elsevier B.V. All rights reserved