Morphological Analysis of the Amorphous Carbon Embedded Nickel-Silica Composite Submitted at Gradual Oxidation

Abstract

Amorphous embedded nickel-silica composites can be directly obtained by Polymeric Precursor Method when the polymeric precursor is pyrolysed in controlled atmosphere. The metallic particles dispersion into the matrix composite is very important to material applications, but the resistance against the oxidation under extreme conditions is also required. In this work, nickel-silica nanocomposite sample was synthesized for containing amorphous carbon as matrix interphase through the direct route based on the Polymeric Precursor Method. The composite sample was obtained by pyrolysis of polymeric precursor at 600 oC for 1 hour under nitrogen flow and then submitted to oxidation in oxygen flow at 400 oC up to 7 hours. It was observed by Transmission Electron Microscopy the metallic nickel nanoparticles present high dispersion into matrix composite. However, in spite of the border of the composite particles are easily oxidized and originate nickel oxide phase, as proven by X-Ray Diffraction, the amorphous carbon phase acts as protective phase for the majority of the composite sample. By Nitrogen Adsorption-Desorption Isotherms at 77 K it was demonstrated the carbon phase also preserves significantly the mesoporous nature of the composite under oxidation process.