Magnetic properties of Ni-doped Mo 2 C produced by fixed bed reactor S.L.A. Dantas a , A.L.R. Souza c , F. Bohn a,c , A.L. Lopes-Moriyama b , C.P. Souza a,b , M.A. Correa a,c,⇑ a Programa de Pós-graduação em Ciências e Engenharia de Materiais, Universidade Federal do Rio Grande do Norte, 59078-970 Natal, RN, Brazil b Programa de Pós-graduação em Engenharia Química, Universidade Federal do Rio Grande do Norte, 59078-970 Natal, RN, Brazil c Departamento de Física, Universidade Federal do Rio Grande do Norte, 59078-970 Natal, RN, Brazil article info Article history: Received 17 April 2020 Received in revised form 27 April 2020 Accepted 30 April 2020 Available online 1 May 2020 Keywords: Mo 2 C Transition-metal doped Room-temperature ferromagnetism abstract Mo 2 C and Ni-doped Mo 2 C were obtained according to a well-established fixed bad reactor methodology. The structural properties were studied by X-ray diffraction and scanning electron microscopy. All samples showed a hexagonal structure; however, the micrograph characterization showed a strong dependence of the agglomerate formation with the Ni-concentration. Magnetization properties were measured and confirm the insertion of the Ni onto Mo 2 C. From the results, the Ni-doped Mo 2 C system seems to be a great candidate for usage as multifunctional material, combining both functionalities, catalytic properties of the Mo 2 C material, and the ferromagnetic ones of the Ni material. Ó 2020 Elsevier B.V. All rights reserved. 1. Introduction Great attention has been given on transition-metal carbides (TMCs) due to their physical–chemical properties, in particular, the high melting point and thermal stability [1]. Besides, the TMCs can present high hydrogenolysis catalytic activity [1], hydro- oxidation [2], and isomerization [3]. Between the more studied car- bides, the Molybdenum carbide (Mo 2 C) has received attention due to the catalytic behavior, comparable with the noble metals [4,5]. Recently, studies highlight the structural properties of Mo 2 C as a very interesting two-dimensional superconducting crystal [6]. However, this material can present a negative hydrogen binding energy due to the high energy density of the empty d orbit, related to the Mo atoms [7]. Therefore, it is relevant to optimize the elec- trical structure of Mo 2 C through transition-metal doping [7]. This procedure leads to the optimization of the catalytic performance [8], leveraging distinct technological applications [9,10]. Associ- ated with the electrical properties improvement, the ferromagnetic properties of some transition-metals enable us to produce multi- functional materials [4]. Nevertheless, we verify a lack of research exploring the ferromagnetism of transition-metal-doped Mo 2 C. In this letter, we present a systematic study of the structural and magnetic properties of Ni-doped Mo 2 C (Ni:Mo 2 C) system. The structural properties were verified through X-ray diffraction (XRD) and Scanning electrons microscopy (SEM/FEG). The mag- netic properties were measured in a wide temperature range by using vibrating sample magnetometer (VSM) technique. The struc- tural results show the presence of b-Mo 2 C phase. The micrographs images allow us to verify the catalytic function of the Ni-dopant on Mo 2 C material. The magnetic behavior of the Mo 2 C material presented a weak paramagnetic contribution, while the Ni:Mo 2 C samples show a ferromagnetic-like behavior, even at room- temperature. Our results bring to light an interesting method to produce multifunctional devices combining both functionalities of Mo 2 C and Ni materials. 2. Experiment Ammonium molybdate (CRQ, 99%) and nickel nitrate hexahy- drate (VETEC, 97%) were used as precursor reagents. Here, besides the pure Mo 2 C, we produced Ni-doped Mo 2 C with 5% and 10%, named by Ni5:Mo 2 C and Ni10:Mo 2 C, respectively. After the weigh- ing, the materials were mixed in deionized water at 80 °C and heat dried until complete water evaporation, followed by drying on an electric oven at 70 °C during 7 h [5]. The organometallic precursor was put inside a fixed bed reactor equipped with mass-flow, and temperature controllers. For more detail about the synthesis and structural characterizations can be found on Dantas et al. [5]. The structural characterizations were obtained from XRD (Bruker D8 Advance), with Cu-ka radiation. The morphology was observed by SEM (LEE 1430 ZEISS SEM/FEG). The magnetic properties were studied in two distinct VSMs. For a wide temperature range study (5 K up to 300 K), was employed a Physical Property Measurement System (PPMS-DynaCool). Zero-field-Cooled and Field-Cooled (ZFC-FC) magnetization curves were measured under a static 0.02 T magnetic field. For room-temperature measurements, with https://doi.org/10.1016/j.matlet.2020.127916 0167-577X/Ó 2020 Elsevier B.V. All rights reserved. ⇑ Corresponding author. E-mail address: marciocorrea@fisica.ufrn.br (M.A. Correa). Materials Letters 273 (2020) 127916 Contents lists available at ScienceDirect Materials Letters journal homepage: www.elsevier.com/locate/mlblue