We investigate the temperature-dependence of the light emission properties of Cu-dominated plasmas with pressures in the order of 1 bar and for currents between 0 and 2 kA. While the wavelength of Cu I 3d 9 4s5s transitions for currents above 1 kA is essentially constant, a 0.1 nm Stark blueshift is observed with decreasing current from 1 kA to zero. Using a lineshape analysis of the light emission spectra, which is based on solving a one-dimensional radiative transfer equation along the line-of-sight across the arc, we show that the transition wavelength increases linearly with temperatures in the 5000-10 000 K range. Based on this observation, we propose a simple method for the temperature diagnostic of plasmas that neither requires an absolute calibration of the intensity of the detected signal, nor complex simulation tools.

Abstract:Surface nitriding of tetragonal zirconia (t-ZrO 2 ) has been performed with the aim of combining the optical properties of zirconium nitride (ZrN) with the hardness and toughening properties of tetragonal zirconia. A high current d.c. arc plasma source has been used to create a reactive environment of atomic hydrogen and NH radicals. Plasma analysis showed that a highly reductive atmosphere is necessary to transform the tetragonal zirconia. X-ray diffraction and transmission electron microscopy analysis show an efficient transformation of the t-ZrO 2 at the surface which exhibits the typical yellow-gold color of ZrN and high wear resistance. For a 2 hours treatment at 750 °C the nitriding is accompanied by the formation of a 250 nm thick gradient layer of ZrN structure and a partial transformation of t-ZrO 2 into cubic zirconia deeper in the bulk.

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