The Kinetics Study on the Oxidation Mechanism of Nano- and Micron-sized Diamond
Date Issued
2009
Date
2009
Author(s)
Chen, Li-Ying
Abstract
Many studies have discussed the kinetic processes and the mechanism of diamond oxidation; however, there is no convincible theory concerning the reaction mechanism. Moreover, kinetic studies on the oxidation of nano-sized diamond are still lacking. The novelty of this work lies in the fact that we confirmed the mechanism of diamond oxidation controlled by one single mechanism.he research consists of three parts: First is to verify diamond powders crystal phases and purities by X-ray diffractometer (XRD). Observation of the morphology and size distribution of diamond powders is confirmed by scanning electron microscope (SEM). We also use mercury intrusion porosimetry (MIP) equipment to analyze the porosity of the diamond powder aggregates. Moreover, we obtained the specific surface area of diamond powder by BET method. Second is to oxidize a series of diamond powders by thermal gravitometry analyser (TGA) at isothermal conditions. Third is to analyze the weight loss data by kinetic models: Avrami equation and Master Curve Model (MCM). n conclusion, the composition of graphite was not detected by XRD. The fact that diamond oxidation starts from the edge, defect and dislocation was observed by SEM. By the MCM results, we can obtain good fitting curves presenting the relation between reaction percentage, time and temperature. The apparent activation energy of different sized diamond oxidation is around 176.3-272.0 kJ/mol. By XRD and MCM results, diamond oxidation is only controlled by one single mechanism that diamond oxidized by the oxygen directly and without the transformation of graphite. The study of diamond oxidation behaviors may have significant impact on all of the nanotechnology industries, as well as on basic science.
Subjects
diamond oxidation
kinetics
micron-sized
nano-sized
surface effect
Type
thesis
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