Effect of synthesis conditions on preparation of nickel metal nanopowders via hydrothermal reduction technique E.A. Abdel-Aal a, ⁎ , S.M. Malekzadeh b , M.M. Rashad a , A.A. El-Midany a , H. El-Shall b a Central Metallurgical Research and Development Institute, P.O. Box: 87 Helwan, Cairo, Egypt b Particle Engineering Research Center, Materials Science and Engineering Department, University of Florida, FL 32611, USA Received 5 June 2006; received in revised form 10 August 2006; accepted 27 September 2006 Available online 5 October 2006 Abstract Synthesis of nickel nanopowders from aqueous solution using hydrothermal reduction method with hydrazine hydrate as a reducing agent and Cetyl trimethyl ammonium bromide (CTAB) as a surfactant was investigated. Statistical design was used to study the effects of reaction time, concentration of nickel chloride, and concentration of surfactant on the nickel particles size. Formed nickel particles were characterized using XRD and SEM. The formation of nickel single phase was revealed from XRD patterns. On the other hand, SEM showed that the nickel particles are in nanosized ranges from 55 nm to 250 nm. The analysis of the results indicated that the reaction time and surfactant addition were the controlling factors. The reduction of nanocrystalline nickel hydroxide Ni(OH) 2 into Ni is the possible formation mechanism. © 2006 Elsevier B.V. All rights reserved. Keywords: Statistical design; Nickel; Nanoparticles; Hydrothermal reduction; Surfactant 1. Introduction Fine nickel powders have been studied extensively over the past decade due to their potential technological applications such as conducting paints [1], rechargeable batteries [2], chemical catalysts [3], optoelectronic [4], magnetic recording media [5], ferrofluids [6] etc. Recently, nickel nanoparticles have attracted a great deal of attention as an inexpensive internal electrode in a multiplayer ceramic capacitor (MLCC) due to their good electrical conductivity, high melting temperature and low cost. The preparation of economically and non-agglomer- ated spherical powders with the narrow size distribution, is the most desirable state for compacting and sintering the electrode materials [7]. For the preparation of nanosized metal particles, ball milling [8], electro-deposition [9,10], thermal plasma [11], polyol process [12–14], gas deposition method (GDM) [15], radiolytic reduction [16], sonochemical method [17], and many other methods [18] have been utilized. However most of these methods are not convenient for the massive production of metals fine powders due to the technical difficulties and the expensive equipment involved. Special attentions have been paid to wet chemical methods. Wu et al. [19] synthesized nickel nanotubules (500–1000 nm) by reduction of nickel chloride using metallic zinc in the presence of ethanol amine at room temperature. Lian [20] prepared spherical ultra-fine Ni powder (300 nm) by hydrothermal reduction of Ni(OH) 2 slurry with an anthraquinone catalyst. Gao et al. [21] prepared nanocrystalline nickel powder (58–102 nm) from nickel chloride solution in the presence of surfactant and hydrazine hydrate as reducing agent at pH 9–10 and temperature of 85–95 °C. In addition, Zhang et al. [22] prepared size-controlled nickel nanocrystals (20–60 nm) by decomposition of nickel acetylacetone in a noncoordinating reagent, oleylamine. Moreover, Hou et al. [23] prepared Ni nanoparticles (3– 11 nm) by reduction-reaction of nickel acetonate with sodium borohydride in the presence of hexadecylamine and trioctylpho- sphine oxide at 120–160 °C. On the other hand, Mi et al. [24] prepared hexagonal close-packed nickel by thermal reduction of nickel chloride by KBH 4 at 300 °C. Kim et al. [25] prepared Powder Technology 171 (2007) 63 – 68 www.elsevier.com/locate/powtec ⁎ Corresponding author. Tel.: +20 202 5010642; fax: +20 202 5010639. E-mail address: eabde@Yahoo.com (E.A. Abdel-Aal). 0032-5910/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.powtec.2006.09.013