| Thermal plasmas have been found to be an excellent activation source for chemical vapor deposition (CVD) in coating applications. The objective of this investigation has been to advance the understanding of certain aspects of thermal plasma CVD with diamond deposition as a focal point. The aspects investigated in this study include the effects of liquid feedstock use with respect to mass transport enhancement and oxygen presence, as well as the effect of substrate rotation on diamond CVD. Characterization studies of the triple torch plasma reactor (TTPR) system by enthalpy probe measurements were conducted to understand the effects of processing parameters and to allow for deposition system optimization. Finally, the deposition process of a composite AlN-diamond coating produced in the TTPR system is described, including mechanical property characterization.; Investigation of these aspects of thermal plasma CVD are conducted by a combination of modelling and experimental work. General conclusions of this study include that liquid feedstock use can enhance mass transport of active growth species to the substrate surface, and the presence of oxygen in liquid precursors may enhance carbon utilization efficiency. Further, the TTPR system provides excellent process gas entrainment, and large process volume for CVD and plasma spraying applications. Substrate rotation can enhance film uniformity, mass deposition rates and area of deposit, primarily by helping to produce more uniform substrate temperatures. Finally, the deposition of a hard, relatively elastic AlN-diamond composite film is shown feasible including a novel AlN deposition process, using the TTPR system. |
