Authors: K-W Wang, S-R Chung, W-H Hung and T-P Perng
Affilation: National Tsing Hua University, Taiwan
Pages: 402 - 405
Keywords: Pd-Ni, nanoparticles, stearic acid, polyethylene glycol, sintering
A series of PdxNi1-x nanoparticles in a diameter of 10 nm were prepared by wet chemical reduction. The surface was modified with 1 wt% stearic acid (SA) or polyethylene glycol (PEG). Desorption of the surfactant from the modified nanoparticles was conducted by a temperature programmed desorption apparatus. The surface energy of the nanoparticles depends on the composition and is related to the desorption temperature of the surfactant. For the alloy with higher Ni content, the surface energy is higher and the desorption temperature of surfactant is also higher. With the same composition, the desorption temperature of SA is always higher than that of PEG, partly because SA has a better thermal resistance, Fig. 1. After surface modification, the surface energy of the nanoparticles is changed. During heating, the more stable nanoparticles have less sintering and grain growth. For example, the SEM morphologies of various Pd70Ni30 samples sintered at 450oC in vacuum are compared in Fig. 2. The nanoparticles modified with SA have higher thermal stability and the sintering is more retarded than those unmodified or modified with PEG. The sintering and growth behavior of the nanoparticles will be discussed in terms of the variation of surface energy due to the surface modification.