Journal of Power Sources 185 (2008) 1262–1266 Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour Short communication Nickel-Zirconia cermet processing by mechanical alloying for solid oxide fuel cell anodes Thomaz Augusto Guisard Restivo ∗ , Sonia Regina Homem de Mello-Castanho IPEN – Instituto de Pesquisas Energéticas e Nucleares, Av. Lineu Prestes 2242, Cidade Universitária, 05508000 São Paulo, SP, Brazil article info Article history: Received 9 July 2008 Received in revised form 22 August 2008 Accepted 26 August 2008 Available online 3 September 2008 Keywords: Anode Solid oxide fuel cells Sintering kinetics Mechanical alloying abstract This paper describes the development of a process based on high energy milling (or mechanical alloying—MA) of metallic Ni and YSZ at 40 vol% Ni composition for the preparation of solid oxide fuel cell anode material. The cermet powder is consolidated using the surface activated sintering (SAS) method. The cermet pellets possess microstructural characteristics that can potentially lead to higher electrocat- alytic activity and fuel reforming capability. In addition to the development of a new processing method for this purpose, a further differential of this work is the addition of Cu in partial substitution of Ni as a means to prevent the formation of carbon on its surface and, hence, the anode’s degradation during ser- vice. The prepared powder samples are well dispersed and structured at the nanometric level, showing thin lamellar constituents. Suitable sintered pellets can be obtained from the powders with the required porosity and microstructure. The higher the energy delivered by MA the lower the initial sintering tem- perature. Activation energies are determined by stepwise isothermal dilatometry (SID) for Ni-YSZ and Ni/Cu-YSZ pellets, involving a 2-step sintering process. The Cu additive promotes sintering and leads to a refined microstructure. © 2008 Elsevier B.V. All rights reserved. 1. Introduction The solid oxide fuel cell anodes developed to date have shown some limitations with regard to the use of different fuels and com- mercial applications. It is a well known fact that, besides the high activity for H 2 -bearing fuel oxidation, the major challenge is to design fuel types derived from organic sources such as hydrocar- bons and alcohols. In view of Brazil’s energy matrix, there is much interest in ethanol and biogas fuels. However, these fuels report- edly cause anode catalyst poisoning by surface carbon deposition. Notwithstanding these technical questions, this paper reports on the development of a method to obtain cermet anode materials for SOFC based on mechanical alloying (MA) of metallic Ni and YSZ powders. A suitable cermet processing method is one of the most relevant factors to overcome the cost and lifetime-related limita- tions of SOFC cells. The co-milling MA process of the constituent powders can pro- duce the following effects [1]: (i) refinement of the material’s structure, thereby increasing the 3-phase boundary site number, and (ii) increase of the powder’s sinterability through the exposure of active surfaces during MA and sintering heat cycle. The surface ∗ Corresponding author. Tel.: +55 1131339240; fax: +55 1131339276. E-mail addresses: guisard@dglnet.com.br (T.A.G. Restivo), srmello@ipen.br (S.R.H. de Mello-Castanho). activated sintering (SAS) method, which derives from the latter effect, is used to consolidate the material. The resulting cermets are expected to display microstructural characteristics that improve the electrocatalytic activity and the fuel reforming capability. The addition of Cu by partial replacement of Ni is also investigated as a means to mitigate carbon deposition on the Ni catalyst. 2. Materials and methods The 40 vol% Ni(Cu)-YSZ cermet was prepared from 8 mol% yttria stabilized zirconia (8YSZ Tosoh Co., BET 13.2m 2 g -1 ) and metallic Ni (99.6 mass% purity) with an average grain size of 29.3 m. The purity of the Cu powder exceeded 99.9 mass% and it had an average particle size of 3 m. The main samples were prepared by high energy milling in a shaker mill (SPEX 8000) at a rotation speed of 10 and 19Hz for 1–16-h periods. Ultra-high molecular weight (UHMW) polyethylene and PTFE vials were used in a milling medium of 5 mm diameter tetragonal zirconia YTZ spheres. The powder-to-sphere mass ratio was 1:10. For purposes of compar- ison, two samples – 40vol% Ni-YSZ and 55vol% NiO-YSZ – were prepared by mixing and homogenizing the raw powders in alcohol slurries, and the former is referred to as homogenized cermet. The resulting powders were characterized by physical and chemical methods, and then subjected to uniaxial pressing at 100 MPa to produce pellets. Sintering was performed in a tubular furnace and a vertical TMA/dilatometer (Setaram Labsys TMA), applying 0378-7753/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2008.08.082