Novel one-pot sol-gel synthesis route of Fe_3C/few-layered graphene core/shell nanoparticles embedded in a carbon matrix

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Fe_3C/few-layered graphene core/shell nanoparticles embedded in a carbon matrix are synthesized by a novel two-step surfactant sol-gel strategy, where the processes of hydrolysis, polycondensation and drying take place in a one-pot. The present approach is based on the combined action of oleic acid and oleylamine, which act sterically on the precursor micelles when a densification temperature is performed in a reducing atmosphere. The structural and magnetic evolution of the formed compounds is investigated, ranging from iron oxides such as Fe_3O_4 and FeO, to the formation of pure Fe_3C/C samples from 700 degrees C onwards. Interestingly, Fe_3C nanoparticles with a size of similar to 20 nm crystallize immersed in the carbon matrix and the surrounding environment forms an oriented encapsulation built by few-layered graphene. The nanostructures show a saturation magnetization of similar to 43 emu/g and a moderate coercivity of similar to 500 Oe. Thereby, an innovative chemical route to produce single phase Fe_3C nanoparticles is described, and an effective method of few-layered graphene passivation is proposed, yielding a product with a high magnetic response and high chemical stability against environmental corrosion.
CRUE-CSIC (Acuerdos Transformativos 2022) ©2022 The Authors. Published by Elsevier B.V. This work has been supported by the Ministerio de Ciencia e Innovacion (MCINN), Spain, through the projects: MAT2015-65445-C2-1-R, MAT2017-86450-C4-1-R, MAT2015-67557-C2-1-P, RTI2018-095856-B-C21, RTI2018-095303-A-C52, PIE: 2021-60-E-030, PIE: 2010-6-OE-013; and Comunidad de Madrid, Spain, by S2013/MIT-2850 NANOFRONTMAG and S2018/NMT-4321 NANOMAGCOST. The authors are also grateful for the electron mi-croscopy characterization performed in the Centro Nacional de Microscopia Electronica at the Universidad Complutense de Madrid (ICTS ELECMI, UCM) , support from MCINN grant #RTI2018-097895-B-43. C.G.-M. acknowledges the financial support from MICINN through the "Juan de la Cierva" Program (FJC2018-035532-I).