Published online by Cambridge University Press: 21 February 2011
Nanocrystalline compacts of TiO2 and Pd were prepared by first condensing the Ti or Pd vapors in an inert gas atmosphere. The Ti was oxidized in situ to TiO2. Samples were prepared by scraping off and compacting the nanophase materials into thin disks. The small angle neutron scattering was measured in the as-prepared condition and after isothermal anneals of up to 23 hrs at 550°C for the TiO2 and up to 3.3 hrs at 300°C for the Pd. Scattering data were obtained in absolute cross sections. Integrated small angle scattering and maximum entropy methods were used in estimating the structural parameters. The results are interpreted in terms of a model which consists of nanometer sized grains of the materials separated by boundary regions which are, on average, much less dense than the respective bulk materials; 21% for the TiO2 and about 56% for Pd. However, the boundary regions contain voids or pores, which contribute to these density decrements. Possible sources of error are discussed.