Enhancing the oxidation resistance of diamond powder by the application of Al2O3 conformal coat by atomic layer deposition

• Diamond particles were coated with aluminum oxide by atomic layer deposition.
• The oxidation resistance of diamond powder was increased.
• The greatest rate of change on the weight loss curve was increased by 50 °C under oxidation in dry air.
• The rate of oxidation of diamond particles was decreased.
• It was demonstrated that the properties of diamond can be improved by surface engineering.

Diamond powders have been coated with thin layers of Al2O3 by atomic layer deposition with the aim of prevent its thermal oxidation. The modified powders were studied by Scanning and Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy; the results show that the coats were conformal. Thermal properties were studied by thermogravimetric Analysis and Differential Thermogravimetric Analysis; it was found that the weight loss onset temperatures (Tonset), that denotes the temperature at which decomposition diamond to CO2 begins, shifted towards higher temperatures (an increment of ≈ 50 K) as result of protective effect of the Al2O3 layer. It is concluded that diffusion mechanism across the protective layers is responsible for the moderately increase of oxidation temperature. The amount of improvement is fairly small to be of use for high temperature applications; however our results confirm that a protective coat can be used to shield diamond from oxidation. Further work is in progress.

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