Please cite this article in press as: R. Ivanov, et al., Graphene-encapsulated aluminium oxide nanoﬁbers as a novel type of nanoﬁllers for electroconductive ceramics, J Eur Ceram Soc (2015), http://dx.doi.org/10.1016/j.jeurceramsoc.2015.06.011 ARTICLE IN PRESS G Model JECS-10165; No. of Pages 5 Journal of the European Ceramic Society xxx (2015) xxx–xxx Contents lists available at www.sciencedirect.com Journal of the European Ceramic Society journal homepage: www.elsevier.com/locate/jeurceramsoc Short communication Graphene-encapsulated aluminium oxide nanoﬁbers as a novel type of nanoﬁllers for electroconductive ceramics Roman Ivanov a , Irina Hussainova a,b , Marina Aghayan a , Maria Drozdova a , Domingo Pérez-Coll c , Miguel A. Rodríguez c , Fernando Rubio-Marcos c,∗ a Tallinn University of Technology, Department of Materials Engineering, Ehitajate 5, 19180 Tallinn, Estonia b ITMO University, Kronverksky 49, St. Petersburg, 197101, Russian Federation c Instituto de Cerámica y Vidrio, CSIC, 28049 Madrid, Spain a r t i c l e i n f o Article history: Received 25 May 2015 Received in revised form 9 June 2015 Accepted 10 June 2015 Available online xxx Keywords: Nanoﬁber Graphene Nanocomposite Thermal analysis Raman spectroscopy SPS a b s t r a c t Graphene has attracted tremendous research interest in recent years owing to its exceptional properties. We report the remarkable ability to transform an insulating material, such as Al 2 O 3 , into a highly con- ductive material by ﬁlling the matrix with alumina nanoﬁbers encapsulated by multi-layered graphene. The ﬁbers of 7 nm in diameter were covered by graphene by catalyst-free one-step CVD process for the ﬁrst time. Coupling between graphene layers and Al 2 O 3 nanoﬁbers results in the development of a novel type of ﬁllers for ceramics, which modify the intrinsic electrical properties of the insulating materials by addition of less than 1 wt.% of graphene into the ceramic matrix. We believe that the general strat- egy described in this study will open new avenues in developing of graphene–ceramic composites with enhanced electrical properties that can be then suitable for high-precision electrical discharge machining. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Structural oxide ceramics are intensively used in industry for a wide variety of applications from high-speed cutting tools and wear resistance parts to dental implants and chemical and elec- trical insulators. Over the past few years, much effort has been forwarded to the development of carbon nanotubes (CNT) and/or graphene reinforced electroconductive ceramics [1–4]. Graphene, which is one-atom thick material, has become of a great scientiﬁc interest due to its exceptional thermal, mechanical and electrical properties [5]. Several layers of graphene form graphene platelets or multilayer graphene nanosheets with a large speciﬁc surface area and a thickness of up to 100 nm exhibit outstanding mechanical properties, which makes them excellent nanoﬁllers/additives for ceramic-based composites [4,6,7]. To achieve the required charac- teristics of the composite, it is essential to homogenously disperse the reinforcement additive throughout the matrix, since its agglom- eration deteriorates material reliability [8]. Dispersion of graphene platelets is still a challenge [8,9] motivating development of novel approaches for preparation of the ceramic–graphene composites. ∗ Corresponding author. Fax +34 917355843. E-mail address: frmacos@icv.csic.es (F. Rubio-Marcos). In this study, we propose a novel type of nano ﬁllers representing alumina nanoﬁbres encapsulated into a few layered graphene for fabrication of an electroconductive oxide ceramic composite. While the majority of the works on the ceramic–graphene composites apply a top–down approach to graphene production, such as exfoliating graphite/graphite oxide (GO) with high energy milling or colloidal processing of graphene/GO, in this work a bottom-up method is introduced. The layers of graphene were grown on the surface of  -alumina nanoﬁbers (ANFCs) of a huge aspect ratio of 10 7 [10] with the help of a process of chemical vapour deposition (CVD). In this communication, we herein propose a strategy for the in situ self-assembly of graphene-layers into a  -Al 2 O 3 nanoﬁber. Using this hierarchical structure allows for improved distribution of graphene and therefore the efﬁciency of use. To build this “hier- archical structure”, we developed a simple one-step CVD method that uses a hot-walled chemical vapour deposition procedure at 1000 ◦ C and atmospheric pressure [11], which is summarized in Fig. 1. It should be emphasized that Al 2 O 3 –ANFCs nanocomposite with graphene contents lower than 1 wt.% can exhibit a signiﬁ- cant high electric response with an electrical conductivity as high as 106 S m −1 , which implies an improvement of ∼12 magnitude orders with respect to Al 2 O 3 without ANFCs. http://dx.doi.org/10.1016/j.jeurceramsoc.2015.06.011 0955-2219/© 2015 Elsevier Ltd. All rights reserved.