Superheating of Ag nanoparticles embedded in Ni matrix

Nanometer-sized Ag particles embedded in a Ni matrix were prepared by using melt spinning. The uniformly distributed Ag nanoparticles with a mean size of 30 nm exhibit a cube-cube orientation relationship with the Ni matrix, and some Ag nanoparticles are surrounded by {111} and {100} low-energy interfaces. Differential scanning calorimetry (DSc) and in situ X-ray diffraction (XRD) analysis results indicate that the Ag nanoparticles can be substantially superheated above the equilibrium melting point (TO) of the bulk Ag, as much as about 70 K above T-0 in the DSC measurement at a heating rate of 20 K/min. The superheating phenomenon is reproducible upon several heating/cooling cycles. In situ XRD results also indicate that the smaller the Ag particle, the higher the superheating. Our observations can be qualitatively interpreted with thermodynamic considerations. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.