Materials Science and Engineering B 178 (2013) 1076–1080 Contents lists available at SciVerse ScienceDirect Materials Science and Engineering B jou rn al h om epa ge: www.elsevier.com/locate/mseb Short communication Magnetic, oxidation and reduction behavior of spinel Ni–Cu manganite Ni x Cu 1-x Mn 2 O 4 powders M.M. Rashad a,∗ , M. Bahgat a , M. Rasly a , S.I. Ahmed b a Central Metallurgical Research & Development Institute (CMRDI), P.O. Box: 87, Helwan 11421, Egypt b Department of Physics, Faculty of Science, Ain Shams University, Cairo, Egypt a r t i c l e i n f o Article history: Received 19 February 2013 Received in revised form 24 June 2013 Accepted 27 June 2013 Available online 9 July 2013 Keywords: Spinel manganite CO oxidation Reduction behavior Magnetic properties a b s t r a c t Nickel copper manganites, Ni x Cu 1-x Mn 2 O 4 (where 0 ≤ X ≤ 1), powders have been synthesized via co- precipitation method. The formed particles were obtained from the precipitate precursors annealed at 800 ◦ C for 2 h. The prepared powders were tested for the catalytic oxidation of carbon monoxide (CO) into carbon dioxide (CO 2 ). The results indicated that the intermediate compositions displayed better catalytic activity than the end compositions for CO oxidation due to the phenomena of synergism. The composition of x = 0.3 and 0.5 showed rapid rise in CO conversion with temperature; about 40% conversion was achieved at 200 ◦ C for the produced manganite sample of chemical composition Cu 0 . 7 Ni 0 . 3 Mn 2 O 4 . A correlation between magnetic properties and hydrogen reduction of manganites was demonstrated. Magnetic properties of reduced manganite were found to be duplicated. The saturation magnetization of reduced NiMn 2 O 4 into Ni/MnO was duplicated of order 15 times from initial value. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Emission of carbon monoxide gas in motor engines, industrial process, and even by a burning cigarette is nowadays one of the most significant environmental problems. A facile way to solve such series environmental problem is to convert CO to CO 2 , which is less harmful than carbon monoxide. Spinel manganites are widely used as a catalyst for the oxidation of CO at ambient temperature, com- bustion of many organic compounds including hydrocarbons, as well as halide and nitrogen containing compounds [1–3]. They are also important in respiratory protection, particularly in the min- ing industry [4]. The oxidation process includes many chemical and physical changes which take place simultaneously and have a profound influence on the other. However, many investigators studied kinetics and mechanism of CO oxidation to CO 2 [5–8], many of the related phenomena are not yet fully understood. Therefore, ways that can raise and monitor the catalytic activity of mangan- ites even at low temperature is considered to be a topic of interest. Comparatively, few works deal with magnetic properties of spinel manganites, despite the fact that these materials are expected to be rich in interesting phenomena. Their research has been focused mainly on structural and electrical aspects [9]. Consequently, in the present investigation an attempt has been made to study the catalytic activity of introducing nickel into copper manganites for ∗ Corresponding author. Tel.: +202 5010642; fax: +202 25010639. E-mail address: rashad133@yahoo.com (M.M. Rashad). CO oxidation and pollution control. Moreover, the effect of hydro- gen reduction on the microstructures and magnetic properties of prepared manganites was also studied. 2. Experimental 2.1. Material synthesis The co-precipitation method was employed to prepare sys- tem of Ni x Cu 1-x Mn 2 O 4 (X = 0, 0.3, 0.5, 0.7, and 1.0, respectively). Appropriate amounts of Cu(NO 3 ) 2 .6H 2 O, Ni(NO 3 ) 2 .6H 2 O, and Mn(NO 3 ) 2 .4H 2 O were dissolved in deionized water. The manganite precursors were precipitated using (5 M) sodium hydroxide solu- tion as a base at pH value 10. The aqueous suspensions were stirred at constant 500 rpm for 15 min to achieve good homogeneity and attain a stable pH conditions. The co-precipitates were filtered off, washed with deionized water and then dried in an oven at 100 ◦ C overnight. In order to form the manganite phase, the dry precursors were annealed at 800 ◦ C for 2 h. 2.2. Material characterization The phases of the prepared and reduced powders were iden- tified from the XRD patterns collected using a Brucker axis D8 diffractometer with Cu K  ( = 1.5406 ˚ A) radiation in 2 range from 10 to 80 ◦ . The particle morphology was investigated by scanning electron microscope (SEM JSM-5400). Specific surface area of the produced samples was determined by BET surface area analyzer 0921-5107/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.mseb.2013.06.022