Microstructural evolution during mechanical treatment of ZnO and black NiO powder mixture
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Microstructural evolution during mechanical treatment of ZnO and black NiO powder mixture M. Kakazey,1,* M. Vlasova1, Y. Vorobiev2, I. Leon3, M. Cabecera Gonzalez4, E.A. Chávez Urbiola2 1 CIICAp-Universidad Autonoma del Estado de Morelos, Cuernavaca, Mexico 2 Unidad Querétaro del CINVESTAV-IPN, Querétaro, Mexico 3 CIQ-Universidad Autonoma del Estado de Morelos, Cuernavaca, Mexico 4 FCQI-Universidad Autonoma del Estado de Morelos, Cuernavaca, Mexico ABSTRACT Kinetics of the microstructural evolution in ZnO and NiO black powder mixture during prolonged mechanical processing (MP) was investigated by Scanning electron microscopy (SEM), Laser Particle Sizer (LPS), X-ray diffraction, electron paramagnetic resonance (EPR), infrared absorption (FTIR) and UV-Visible diffuse reflection methods. INTRODUCTION ZnO-NiO system has attracted particular attention as the basis for creating ultraviolet lightemitting diodes [1, 2], transparent p-NiO/n-ZnO semiconductors [3, 4], seeking opportunities to create the room temperature ferromagnetism [5] etc. This study provides information about the production and behavior of native defect states in ZnO-NiO system with increasing mechanical treatment time. The structural defects in initial components of samples as well as the defects which are formed in zones of destruction are subjected to: a local hyper-rapid ultrahightemperature spike (at the moment of destruction), significantly prolonged collective hightemperature influences (at the moment of ball loading), and accumulative thermal effects. EXPERIMENTAL RESULTS The basic starting materials were the commercially available ZnO powder (Reasol, Milan, Italy) and the nickel oxide black powder (99.26 % purity; Fluka Chemie J.). The ZnO + 1% wt. NiO mixture was prepared. MP of samples was carried out in a Planetary Ball-Mill (type PM 400/2, Retsch Inc.) using the rotation speed of 400 rev×min-1. The durations of mechanical processing, tMP, were: 1, 3, 9, 30, 90 and 390 min. The Scanning electron microscopy (SEM), model LEO 1450 VP; the Laser Particle Sizer (LPS), Analysette 22 COMPACT, FRITSCH; the X-ray diffractometer, Siemens D-500 with CuKa radiation; the Electron Paramagnetic Resonance equipment (EPR), SE/X 2547 – Radiopan; an infrared (IR) spectrophotometer (Bruker Vector 22, FTIR) and the UV-Vis diffuse reflectance spectroscope (DRS), with Pelkin−Elmer Lamda 2 spectrometer, were used in this work. SEM results. The initial samples consisted of ZnO-particles with a spherical-like shape. The ZnO is estimated of ~ 250 nm. The NiO large granules are average ZnO particle size, DSEM characterized by a spherical-like shape as well with the size from 3 to 10 mm. Thus, the initial ZnO with increasing tMP NiO (black) powder is a granular powder. A consecutive reduction of DSEM has been detected.
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ZnO LPS results. The initial sample consisted of the particles with sizes: D LPS ~ 3×102 – 5-
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ZnO d 300 nm 8×10 nm. For tMT equal to 30 min the quantity of fine fraction particles with D LPS increased from 1 to 3%) and the maximum of size distri
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