Abstract
The present work investigated the use of conventional hot filament chemical vapor deposition technique (HFCVD) diamond film as a coating on Platinum Thin Film Heat Transfer Gauges to improve their operation performance in the range of Mach 4 to Mach 15 airflow, in order to acquire accurate heat transfer data in hypersonic experiments. The gauge under development has a substrate made of sintered silicon nitride (Si 3N 4). It has cylindrical shape, with 5 mm diameter and 15 mm length. On it's top surface there is a platinum thin film, which is the heat flux-sensing element. Diamond films were deposited at 870 K and 6.5 kPa by HFCVD using a gas mixture of methane 1.0% or 1.5% vol. in hydrogen. For improving the adherence, films were grown onto Pt/Si 3N 4. A SiO 2 interlayer was also used to minimize the dissolution of carbon into the platdinum substrate during film growth. Scanning Electron Microcopy (SEM) has evidenced a faceted polycrystalline grains with orientation (111) and (100) covering the entire surface. Raman spectroscopy has demonstrated a film with high quality and low stress, by considering the small peak shift presents in the spectrum compared to natural diamond.
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