Influence of dose and ion concentration on formation of binary Al–Ni alloy nanoclusters Alam Abedini a , Farhad Larki a , Elias Saion a,n , Azmi Zakaria a , M. Zobir Hussein b a Department of Physics, Faculty of science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia b Department of Chemistry, Faculty of science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia HIGHLIGHTS c Synthesized Al–Ni bimetallic nanoparticles by the gamma-ray induced method. c Examined how changes in ion concentration affect particle size. c Increasing dose can decrease the size of bimetallic nanoparticles. c Nanoparticles in uniform size distribution are obtained at higher dose. c Nucleation and aggregation rates can change the size of nanoparticles. article info Article history: Received 24 January 2012 Accepted 21 May 2012 Available online 29 May 2012 Keywords: Al–Ni nanoclusters Gamma reduction technique Particle size abstract Colloidal Al–Ni nanoclusters were prepared in an aqueous polyvinyl alcohol solution containing aluminum chloride and nickel chloride as metal precursors, polyvinyl alcohol as a capping agent, isopropanol as a scavenger of hydroxyl radicals, and distilled water as a solvent. Gamma irradiations were carried out in a 60 Co gamma source chamber at doses up to 100 kGy. The nanocluster properties were characterized by transmission electron microscopy (TEM), UV–visible spectrophotometry, and X-ray diffraction (XRD). By controlling the dose and precursor concentration, nanoclusters with different particle sizes were obtained. The average particle diameter increased with increase of precursor concentration and decreased with increase of dose. This is owing to the competition between nucleation, growth, and aggregation processes in the formation of nanoclusters during irradiation. & 2012 Elsevier Ltd. All rights reserved. 1. Introduction Metallic nanoparticles have drawn considerable interest in recent years due to their unique size-dependent properties and a wide range of application potential in science, medicine, and engineering (Bienert et al., 2009). These particles exhibit physical and chemical properties that differ significantly from the bulk or molecular properties of their respective metals (Fendler and Tian, 1998; Ozin, 1996). In particular, nickel aluminides are important for high performance materials because of their high melting points, relatively low densities, good strength, and high tempera- ture corrosion and oxidation resistance (Cadoret et al., 2005; Cokoja et al., 2007). They showed great application potentials in automobile engines, aircraft, electricity generation, and energy conversion equipment. There are several routes for producing nickel aluminide, such as self-propagation high temperature synthesis (Dong et al., 2002), laser vaporization (Glaspell et al., 2006), chemical vapour synthesis (Sohn et al., 2007), low-energy reaction synthesis (Moussa et al., 2007), and non-transferred DC plasma spray torch synthesis (Suresh and Selvarajan, 2010). Chemically and electro- chemically synthesized bimetallic nanoparticles have some dis- advantages such as impurities, solvent toxicity, insolubility and difficulty in their preparation that limit their commercialization potential. The search for alternative methods that overcome some unfavorable characteristics such as long tedious process, poor compatibility, high cost and low production is continuing. In all methods, control of the atom aggregation and controlling the size and uniformity of the nanoparticles are the most important steps. The gamma irradiation induced technique has proven to be an appropriate method to prepare monometallics and bimetallic nanoparticles (Belloni, 2006; Keghouche et al., 2005). In this method, aqueous solutions are exposed to g-rays, creating reac- tive species such as hydrated electrons (e  aq ) and hydrogen atoms, which in turn, reduce the metal ions into metal atoms and these Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/radphyschem Radiation Physics and Chemistry 0969-806X/$ - see front matter & 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.radphyschem.2012.05.015 n Corresponding author. Tel.: þ60 172459439; fax: þ60 389454454. E-mail address: elias@science.upm.edu.my (E. Saion). Radiation Physics and Chemistry 81 (2012) 1653–1658