Cement Pastes and Mortars Containing Nitrogen-Doped and Oxygen-Functionalized Multiwalled Carbon Nanotubes

Figure 7

X-ray diffraction patterns for cement pastes with MWCNT-N_x during the hydration. The pattern for pure cement powder is also shown. After one hour of hydration, the peaks corresponding to the ettringite structure and hydrated calcium silicate emerge in accord with the SEM images. Surprisingly, for zero hours of hydration (few minutes of hydration), several peaks are suppressed; the peak appearing at approximately 27 degrees suggests the presence of carbon nanotubes, and the peak at approximately 55 degrees could be associated with the iron-carbide or α-Fe nanoparticles contained inside carbon nanotubes.