Thermal evolution of WC/C nanostructured coatings by raman and in situ XRD analysis

Said El Mrabet, Manuel David Abad, Carlos López-Cartes, Diego Martínez-Martínez, Juan Carlos Sánchez-López

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In this work, a series of WC/C nanostructured films were deposited on silicon substrates by changing the ratio of sputtering power applied to graphite and WC magnetron sources (Pc/ Pwc: 0, 0.1, 0.5, 1). The thermal stability of WC/C coatings was followed in situ by means of X-ray diffraction measurements up to 1100°C in vacuum (10-1 Pa). Initially, the film microstructure is composed of nanocrystalline WC 1-x and W2C phases. As the Pc/Pwc ratio increases the crystallinity decreases, and WC1-x becomes the predominant phase from Pc/ Pwc = 0.1. The results show that the structural evolution with temperature of all studied layers depends essentially on their initial phase and chemical composition (determined by the synthesis conditions: ratio Pc/Pwc)- The coating deposited at Pc/Pwc = 0 reveals a transformation of W2C phase into W and W3C phases at 400°C. However, the samples with Pc/Pwc greater than 0 exhibits an improved thermal stability up to 600-700°C where the WC1-x begins to transform into W2C and WC phases. At 900°C, WC is the predominant phase, especially for those coatings prepared with higher ratios. Further annealing above 1000°C yields W as the foremost phase. The thermal behaviour was later studied by means of Raman spectroscopy measurements at certain temperatures where the main changes in phase composition were observed. Particularly, a fitting analysis was carried out on the D and G bands typical of disordered and amorphous carbon. The changes induced during heating are discussed in terms of the positions of D and G lines, and full width at half maximum (FWHM).

Idioma originalAnglès
Pàgines (de-a)S444-S449
RevistaPlasma Processes and Polymers
NúmeroSUPPL. 1
Estat de la publicacióPublicada - 2009
Publicat externament


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