Epitaxial dependence of the melting behavior of In nanoparticles embedded in Al matrices
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Epitaxial dependence of the melting behavior of In nanoparticles embedded in Al matrices H. W. Sheng National Key Laboratory for RSA, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015, People’s Republic of China
G. Ren and L. M. Peng Beijing Laboratory of Electron Microscopy, Chinese Academy of Sciences, Beijing 100080, People’s Republic of China
Z. Q. Hu National Key Laboratory for RSA, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015, People’s Republic of China
K. Lu National Key Laboratory for RSA, and International Center for Materials Physics, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015, People’s Republic of China (Received 19 December 1995; accepted 23 September 1996)
Nanometer-sized In particles (5–45 nm) embedded in the Al matrix were prepared by using melt-spinning and ball-milling techniques. Different crystallographic orientationships between In nanoparticles and the Al matrix were constructed by these two approaches. Melting behavior of the In particles were investigated by means of differential scanning calorimetry (DSC). It was found that the epitaxially oriented In nanoparticles (with the Al matrix) in the melt-spun sample were superheated to about 0–38 ±C, whereas the randomly oriented In particles in the ball-milled sample melted below its equilibrium melting point by about 0–22 ±C. We suggest that the melting temperature of In nanoparticles can be either enhanced or depressed, depending on the epitaxy between In and the Al matrix.
I. INTRODUCTION
Studies of the melting process of nanometer-sized crystallites have drawn considerable interest during recent decades, because they are not only helpful to understand the melting mechanism, but also useful to reveal the thermodynamic aspect of nanostructures. A body of evidence shows that the melting temperature of nanometer-sized free particles is often decreased, and the melting temperature depression was found to be inversely proportional to their particle sizes.1–5 This dependence arises mainly because of the increasing surface-to-volume ratio with the decreasing particle size. Such a phenomenon has also been reported for some cases of embedded particles.6–8 A renewed surge of experimental results shows, however, that the melting temperature for the epitaxial precipitates may also be substantially increased, as with the In and Pb embedded in an Al matrix.9–12 Although arguments on this behavior are not in agreement, it is generally related to the interface effect. Cahn suggested that the observed superheating originates from the epitaxy between the embedded particles and the matrix, and no substantial superheating is expected for the incoherent interfaces.13 Therefore, it is necessary to carry out a comparative J. Mater. Res., Vol. 12, No. 1, Jan 1997
study of the melting behavior of the embedded particles with different orientations with the matrix in order to clarify the intrinsic effect of the interface structures on th
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