Papers by Keyword: Nitrogen Diffusion

Abstract: We report nitrogen (N) doping of 4H-SiC by KrF excimer laser irradiation in liquid N₂. In comparison to phosphorus (P) doping performed using phosphoric acid solution, the liquid-N₂ immersion-laser doping can introduce N atoms deeper (~ 1 μm depth) into the 4H-SiC, which results in reduction of doped layer resistance by approximately 3 orders of magnitude. Doping is shown to proceed by the thermal diffusion of species, while loss of the host material from the surface by ablation takes place at the same time. Chemical analysis shows that high density carbon (C) vacancies are generated in the N doped region, which suggests enhanced diffusion of N assisted by the presence of C vacancies. pn junction diodes are formed by using the N doping technique. Turn-on voltage is ~ -3V, which is reasonable for a pn junction diode of 4H-SiC.

Abstract: Recent scientific work has opened new fields of application to mechanical treatments such as shot blasting or peening. Indeed, it has been shown that this treatment, performed before a nitriding treatment on the surface of ferrous alloy, lowers processing temperatures and significantly increases the diffusion kinetics. We undertook to test this combination of mechanical pretreatment and thermochemical treatment on stainless steels and nickel-based alloys. The mechanical treatments were done by surface attrition peening. The pretreated samples were then nitrided at low temperature using remote plasma. In this paper, the results obtained after nitriding treatments on samples treated by attrition peening are compared to those nitrided only. The use of X-ray diffraction, microhardness measurement, observations by optical and scanning electron microscopy, texture analysis by EBSD (Electron BackScatered Diffraction) and measurement of nitrogen concentration profiles by SIMS (Secondary Ion Mass Spectrometry) allows quantifying the effects of the combined treatments.

Abstract: Nitriding process through a cyanate liquid salt bath is one of the advanced surface treatment techniques that is recently employed to modify corrosion and wear resistance behaviour of steels. Considering spreading out of P/M alloys application in various industries, especially automotive industry, and the presence of porosities in its structure, in this research the influence of porosities, process duration and temperature parameters in nitrogen diffusion and formation of layers on a P/M Distaloy AE Steel through the advanced cyanate liquid salt bath nitriding process has been investigated. Also it has been analyzed microstructure of layers by means of OEM, SEM and microhardness deep profile investigations. Existence of ε (Fe2-3N) and γ' (Fe4N) phases was detected by XRD analyzing. Results demonstrated that with increasing porosities, it was configured a non-uniform diffusion regions on the surface due to nitrogen atoms dispersion.