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 (T₀) of the bulk Ag, as much as about 70 K above T₀ 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.