ChemInform Abstract: Electron Microscopy and Magnetic Studies of the Interaction Between Nickel and Silica: Considerations on Possible Anchoring Sites.
Abstract
Highly dispersed silica-supported Ni particles have been prepared by cation exchange from a nickel nitrate solution in NH3 and H2 reduction at 275 K. The dispersion is more homogeneous than for samples prepared by classical im?regnation and the particle size is found to be 1.8 nm with a slight discrepancy in the values measured by TEM, FMR and magnetic susceptibility.
ChemInform Abstract
Highly dispersed silica-supported Ni particles have been prepared by cation exchange from a nickel nitrate solution in NH3 and H2 reduction at 275 K. The dispersion is more homogeneous than for samples prepared by classical im?regnation and the particle size is found to be 1.8 nm with a slight discrepancy in the values measured by TEM, FMR and magnetic susceptibility. This discrepancy can be explained by the flattened shape of the particles leäding to characteristic magnetic anisotropies as evidenced by FMR and by the existence of a chemisorbed phase which demagnetizes the surface atoms. EPR, UV-VIS and near-IR studies indicate that Ni+ and Ni" ions are located at the metal - support interface and act as anchoring sites. The resistance to sintering, the shape of the particles, and the metal - support stress can be understood consistently as a direct congequence of the anchoring effect of Ni+ and Ni" ions.
