Journal of Alloys and Compounds 460 (2008) 191–195 Synthesis and characterization of Ag doped Cu nanoparticles C. Duhamel, J.L. Bonnentien, Y. Champion ∗ ICMPE-CNRS UMR 7182, Universit´ e Paris 12, 15, rue Georges Urbain, 94407 Vitry-sur-Seine Cedex, France Received 1 December 2006; received in revised form 16 May 2007; accepted 17 May 2007 Available online 21 May 2007 Abstract The synthesis of Cu 100-x Ag x (0.05 at.% < x < 0.30 at.%) nanoparticles using an evaporation–condensation process has been studied. Particular attention has been paid to the composition of the as-prepared powders. Compared to the master alloy, systematic enrichment in Ag of the particles is observed at the beginning of the synthesis but a continuous decrease in the Ag content of the powders is observed during the process. Even though, after de-agglomeration, the chemical composition of the powders is, in average, homogeneous. We have shown that optimized synthesis conditions give spherical particles with a mean diameter of 50 nm and a reasonable yield rate. © 2007 Elsevier B.V. All rights reserved. Keywords: Nanocrystalline particles; Copper; Condensation; X-ray diffraction 1. Introduction Decreasing the grain size of a polycrystalline material leads to a higher volume fraction of the intercrystalline regions (grain boundaries and triple junctions) [1]. For small grain sizes, typi- cally d < 100 nm, the intergranular zones become non-negligible (atomic fraction in grain boundaries, GB >1%) and are likely to influence the properties of the material, among which the mechanical behavior. It has been reported that, in ultrafine- grained metals, non-equilibrium GB and low angle GB lead to higher stress levels [2] whereas high angle GB favor dislocation absorption and grain recovery [3]. Ma et al. [4] have shown that nano-twinned copper, with a mean lamellae spacing of 200 nm exhibits significantly enhanced ductility under tensile loading. However, although extensive studies are carried out on this topic, the micro-mechanisms responsible for such a behavior are still unclear. An alternative approach to understand the role of GB is to compare nanocrystalline metals with various GB chemistries. This purpose needs to synthesize bulk nanocrystalline metals which GB are selectively doped with foreign atoms. It should be emphasized as well, that the presence of impurities at the GB should increase the stability of nanocrystalline materials by inhibiting both mechanically and thermally driven grain growth [5,6]. ∗ Corresponding author. Tel.: +33 56 70 30 41; fax: +33 1 46 75 04 33. E-mail address: champion@glvt-cnrs.fr (Y. Champion). The powder metallurgy technique is one of the main routes to produce bulk nanocrystalline metals. Synthesis of fully dense bulk nanocrystalline copper by densification of nanoparticles has already been achieved [7]. The as-prepared material exhibits interesting mechanical properties such as a near-perfect elasto- plastic behavior with 12% ductility in tension [8]. The synthesis of the nanoparticles is the first step of the processing route. In an attempt to obtain bulk nanocrystalline metals with GB doped with foreign elements, the nanopowders have to fulfill several requirements: (i) a small particle size, (ii) a spherical shape to facilitate further densification, (iii) a reasonable yield rate and (iv) a good chemical homogeneity. The nanopowders are pro- duced using the cryogenic melting technique. This technique is based on the evaporation of a molten metallic droplet immersed in a cryogenic liquid and the condensation of the surrounding supersaturated metallic vapor [9]. Production of nanoparticles of pure metals such as Cu, Fe and Al with a reasonable yield rate has been already successfully achieved [10,11]. However, gas con- densation techniques are rarely used to synthesize nanoparticles of alloys [12–14]. Because of the difference in the evaporation rates of the two elements, deviation in composition between the master alloy and the resulting powders is expected and the final composition of the particles is usually unpredictable [15]. The present work reports on the synthesis and charac- terization of Ag doped Cu nanoparticles prepared by the cryogenic melting technique. The chemical composition and the homogeneity of the as-prepared powders have been carefully 0925-8388/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2007.05.064