X-ray diffraction evidence of a phase transformation in zirconia by the presence of graphite and carbon nanotubes in zirconia toughened alumina composites

摘要

We have demonstrated by X-ray diffraction a transformation from the r-ZrO_2 phase into the m-ZrO_2 phase by the presence of multiwall carbon nanotubes (MWCNTs) and graphite powder (GP) in zirconia toughened alumina composites sintered in air. The phase transformation does not occur in sintering under an argon atmosphere. The quantitave phase analysis was carried out by fitting the X-ray diffraction profile with the Rietveld method making use of the FullProf software. The obtained amounts of m-Zr02 phase by the presence of GP and MWCNTs were 5% and 2.2%, respectively, at a sintering temperature of 1520 °C for 1 h.