Bismuth-ceramic nanocomposites with unusual thermal stability via high-energy ball milling

Electrically conducting nanocomposities of bismuth metal and insulating ceramic phases of SiO2 and MgO was generated with high energy ball milling for 24 h using zirconia milling media. The resulting nanocomposities contain Bi nanoparticles with sizes down to 5 nm in diameter. The morphology is a strong function of the oxide phase specifically, the Bi appears to wet MgO while it terms spherical nanoparticle of the SiO2. X-ray diffraction measurements indicate a nominal bismuth grain size of 50 nm, and peak fitting to a simple bidisperse as small as 5 nm are observed in transmission electron microscopy (TEM), but may not constitute a significant volume fraction of the sample. Differential scanning calorimetry reveals dramatic broadening on the temperatures over which melting and freezing occur and a surprising persistence of a nanostructure after thermal cycling above the melting point of the Bi phases.