A Jamrozik

A. Malolepszy

A. Slawska-Waniewska

BT Hanga

C de las Casas

D. Wasik

EF Kukovitsky

G. Kowalski

H Pan

I Kuryliszyn-Kudelska

J Kong

J. Borysiuk

KY Xie

L Stobinski

L. Stobinski

M. Krajewski

M. Tokarczyk

RM Cornell

S Iijima

S. Lewinska

Y Zhang

YH Li

Z Liu

English

Crossref

J Supercond Nov Magn (2015) 28:901–904DOI 10.1007/s10948-014-2794-7ORIGINAL PAPERPreparation and Characterization of Hematite-MultiwallCarbon Nanotubes NanocompositeM. Krajewski · A. Malolepszy · L. Stobinski ·S. Lewinska · A. Slawska-Waniewska · M. Tokarczyk ·G. Kowalski · J. Borysiuk · D. WasikReceived: 7 June 2014 / Accepted: 12 September 2014 / Published online: 16 October 2014© The Author(s) 2014. This article is published with open access at Springerlink.comAbstract The aim of this work is to study the preparationand characterization of a new nanocomposite which con-sists of chemically-modified multiwall carbon nanotubescovered by randomly-deposited nanoparticles of hematite.The morphology, structural and physical properties of theinvestigated nanomaterial were determined by means oftransmission electron microscopy, X-ray diffraction andvibrating sample magnetometry at ambient conditions. Thepresence of residual catalyst nanospheres inside multiwallcarbon nanotubes was confirmed by transmission electronmicroscopy. The signal coming from this contamination wasunder the detection limit of X-ray diffractometer, thereforeit was not registered.Keywords Hematite · Multiwall carbon nanotubes ·CVD · TEM · XRD · VSMM. Krajewski () · M. Tokarczyk · G. Kowalski · J. Borysiuk ·D. WasikFaculty of Physics, Institute of Experimental Physics,University of Warsaw, Hoza St.69, 00-681 Warsaw, Polande-mail: marcin.krajewski@fuw.edu.plA. MalolepszyFaculty of Materials Science and Engineering, Warsaw Universityof Technology, Woloska St. 141, 02-507 Warsaw, PolandL. StobinskiInstitute of Physical Chemistry, Polish Academy of Sciences,Kasprzaka St. 44/52, 01-224 Warsaw, PolandL. StobinskiUniversity Research Centre “Functional Materials”, WarsawUniversity of Technology, Woloska St. 141, 02-507 Warsaw,PolandS. Lewinska · A. Slawska-Waniewska · J. BorysiukInstitute of Physics, Polish Academy of Sciences, Al. Lotnikow32/46, 02-668 Warsaw, Poland1 IntroductionIn 1991, Iijima managed to prepare the first multiwall car-bon nanotubes (MWCNTs) via arc discharge process [1].Since then, carbon nanotubes (CNTs) became the sourceof advanced studies in the field of physics, chemistry andmaterial sciences. At the same time, CNTs started to playa significant role in numerous applications in many fieldsincluding: medicine [2], high-performance adsorbents [3],sector of energy storage and conversion [4, 5], etc.There are four commonly-used CNTs fabrication tech-niques: arc discharge [1], laser ablation [6], chemical vapordeposition (CVD) [7] and vapor–liquid–solid (VLS) method[8]. However, the two latter techniques seem to have cer-tain advantages over the other. For instance, they are nothigh temperature processes. The growth and dimensions ofCNTs (via CVD or VLS) can be easily-controlled by fittingreaction parameters such as: temperature, source of carbon,or catalyst concentration. However, CNTs growth complica-tions arise when using metallic catalysts such as iron (Fe),cobalt (Co) or nickel (Ni) because they form metal car-bides together with carbon precursors which become theseeds for carbon nanotubes growth. Therefore, they oftenremain built into the tubes and become an integral part ofthe nanomaterial.So far, it has been reported that the purification of con-taminated CNTs could be achieved via the functionalizationof carbon nanotubes [9]. Through this procedure, it is pos-sible to cover the CNTs surface by various chemical groupssuch as: -OH, -COOH, COONH4, etc. Furthermore, it hasbeen proven that the traces of catalyst are gradually removedfrom the nanotubes at the same time [10].Another material which is interesting in the case of thiswork is hematite (α-Fe2O3). This oxide belongs to the groupof low-cost and environmentally-friendly transition metal902 J Supercond Nov Magn (2015) 28:901–904Fig. 1 TEM images ofMWCNTs-COONH4 (a),multiwall carbon nanotube filledby the trace of catalyst (b), andMWCNTs-COONH4 coatedrandomly by α−Fe2O3 (c)oxides. Moreover, α-Fe2O3 is the most thermodynamicallystable iron oxide and it is extensively used in the productionof pigments, jewelry, catalysts, sensors, hard and soft mag-nets, devices for energy storage and conversion, etc. [11].The purpose of this work is to synthesize and charac-terize a new nanocomposite which consists of chemically-modified multiwall carbon nanotubes (MWCNTs) cov-ered by randomly-deposited nanoparticles of hematite(α-Fe2O3). Such nanomaterial promises to combine thefeatures of both MWCNTs and α-Fe2O3 making it anuseful material in many fields for future applications.2 Experimental DetailsThe raw multiwall carbon nanotubes (MWCNTs; 93 %of purity; CNT CO., Ltd. from South Korea) weremanufactured via CVD process with iron (Fe) as thecatalyst. Such MWCNTs were chemically-modified byheating at 120 ◦C in concentrated nitric acid (68 %HNO3) for 50 h under a reflux. Then, they were fil-tered and washed with distilled water until the pH valueof the filtrate reached 6. Thereby, the MWCNTs wereFig. 2 XRD patterns of MWCNTs-COONH4 (a), α−Fe2O3/MWCNTs (b), and commercial α−Fe2O3 (c)oxidized and formed carboxylic groups attached to theends and the walls of CNTs (MWCNTs-COOH) [12].Such functionalized CNTs were treated with a 25 % aque-ous solution of ammonia and then rinsed with distilled waterduring filtration to obtain the ammonium salt (MWCNTs-COONH4). After that, 1 g of MWCNTs-COONH4 wasdispersed in 500 ml of distilled water and cooled to 4 ◦C.In two other beakers 0.215 g of iron dichloride tetrahy-drate (FeCl2· 4H2O; 98 % of purity; Sigma-Aldrich) and0.588 g of iron trichloride hexahydrate (FeCl3· 6H2O; 97 %of purity; Sigma-Aldrich) were dissolved in distilled waterand added by droplets to the previously prepared carbonnanotube dispersion mixed with a magnetic stirrer. After30 min, the pH of dispersion was brought up to 10 with 1 MNaOH. The obtained product was heated up to 100 ◦C ona hot plate with magnetic stirring for 30 min. Finally, theprepared nanocomposite was centrifuged and washed withdistilled water until the value of pH reached 7.The obtained nanomaterial was studied using a PhillipsX’Pert diffractometer (XRD) equipped with a Cu X-raysource and a parallel beam Bragg reflection mirror, a JEOLJEM 3010 transmission electron microscope (TEM) andan Oxford Instruments Ltd. vibrating sample magnetometer(VSM) in the range of magnetic field between −0.6 T andFig. 3 Magnetization hysteresis loops of MWCNTs-COONH4 (a)and α−Fe2O3/MWCNTs (b)J Supercond Nov Magn (2015) 28:901–904 9030.6 T. The XRD and VSM measurements were performedunder ambient conditions.Additionally, the results for commercially-available ref-erence samples of α-Fe2O3 powder (99.98 % of purity; CarlRoth GmbH) and the chemically-modified multiwall car-bon nanotubes (MWCNTs-COONH4) are presented in thiswork.3 Results and DiscussionTEM images of chemically-modified MWCNTs andα-Fe2O3/MWCNTs nanocomposite are presented in Fig. 1aand 1c. A residual amount of catalyst coming from thepreparation process can also be seen built into the nan-otube (Fig. 1b). TEM studies show that MWCNTs arevery disordered, braided, and are successfully coated by therandomly-dispersed hematite nanoparticles. The diameter ofCNTs varies from 10 to 40 nm. The average diameters of α-Fe2O3 and traces of catalyst are approximately 50 nm and12 nm, respectively.XRD has great advantages in comparison with the otherexperimental techniques because it is simple in terms ofimplementation and it also has the ability of measuringfor a long period of time without any negative effectson the sample. Therefore, the XRD technique is a goodtool to study the structure of α-Fe2O3/MWCNTs nanocom-posite and reference samples. These results are presentedin Fig. 2. Recorded XRD patterns confirm that MWC-NTs are successfully coated by hematite. The positionsof peaks originating from α-Fe2O3 and the chemically-modified MWCNTs lie at the same angle positions for allstructures. Moreover, no significant changes in the function-alized MWCNTs structure after deposition of hematite areobserved.Figure 3 presents the magnetization hysteresis loops ofMWCNTs-COONH4 and α-Fe2O3/MWCNTs. The differ-ences in curve shapes indicate different magnetic behav-iors. The functionalized MWCNTs contain the encapsulatedtraces of catalyst coming from the CVD process. The previ-ous studies performed on this nanomaterial have shown thatthe residual amount of catalyst is associated with the pres-ence of non-stoichiometric iron carbide (FexC), α-Fe andferrihydrite [10]. Most of these iron compounds are ferro-magnetic, therefore magnetization hysteresis of MWCNTs-COONH4 reveals the ferromagnetic behavior. On the otherhand, the shape of the magnetization curve for the stud-ied nanocomposite exhibits more complex behavior with acoercivity and large high field susceptibility. It is related tothe strong influence of α-Fe2O3 deposited on the surfaceof carbon nanotubes being superimposed on the ferromag-netic behavior of the catalyst residue, of which the content inthe investigated material is much lower than hematite. Therecorded values of saturated magnetization (MS), remnantmagnetization (MR) and coercivity (HC) for MWCNTs-COONH4 are equal 0.26 emu/g, 0.10 emu/g and 0.04 T(400 Oe), respectively. For α-Fe2O3/MWCNTs, the rem-nant magnetization equals 0.11 emu/g and the coercivityequals 0.03 T (300 Oe). Taking into account that all mag-netic moment values are given in this work per unit oftotal mass (emu/g), considering all compounds inside andoutside of CNTs and also the nanotubes mass, it is verydifficult to perform further analysis of the obtained results.Nevertheless, the presence of encapsulated catalyst tracesin CNTs and diamagnetic contribution of the graphitic nan-otubes play important roles for the magnetic properties ofboth MWCNTs-COONH4 and α-Fe2O3/MWCNTs.4 ConclusionThis work confirms that α-Fe2O3/MWCNTs nanocompos-ite could be simply prepared via the proposed chemicalmethod. Morphology and structural and magnetic featuresof this material were determined. Moreover, the investigatednanomaterial is interesting due to the variety of possibleapplications; for example in the lithium-ion batteries [4, 13]and/or the supercapacitors [5, 14]. Therefore, it is supposedto be a very perspective material with regards to futureresearch.Acknowledgments This work was supported by the Foundation forPolish Science International PhD Projects Programme co-financed bythe EU European Regional Development Fund, A.M. thanked the sup-port from the European Union funds by the European Social Fund andL.S. thanked the National Center for Research and Development forsupport by the project no. PBS1/A5/15/2012. Sincere thanks towardsDr. J. Syzdek for the research consultations.Open Access This article is distributed under the terms of the Cre-ative Commons Attribution License which permits any use, distribu-tion, and reproduction in any medium, provided the original author(s)and the source are credited.References1. Iijima, S.: Nature 354, 56–58 (1991)2. Liu, Z., Chen, K., Davis, C., Sherlock, S., Cao, Q., Chen, X., Dai,H.: Cancer Res. 68, 6652–6660 (2008)3. Li, Y.H., Wang, S.G., Zhang, X.F., Wei, J.Q., Xu, C., Luan, Z.K.,Wu, D.H.: Mater. Res. Bull. 38, 469–476 (2003)4. de las Casas, C., Li, W.Z.: J. Power Sources 208, 74–85(2012)5. Pan, H., Li, J., Feng, Y.: Nanoscale Res. Lett. 5, 654–668 (2010)6. Zhang, Y., Gu, H., Iijima, S.: Appl. Phys. Lett. 73, 3827–3829(1998)904 J Supercond Nov Magn (2015) 28:901–9047. Kong, J., Soh, H.T., Cassell, A.M.: Nature 395, 878–881(1998)8. Kukovitsky, E.F., L’vov, S.G., Sainov, N.A.: Chem. Phys. Lett.317, 65–70 (2000)9. Jamrozik, A., Mazurkiewicz, M., Malolepszy, A., Stobinski, L.,Matlak, K., Korecki, J., Kurzydłowski, K.J., Burda, K.: Phys.Status Solidi A-Appl. Mat. 208, 1783–1786 (2011)10. Kuryliszyn-Kudelska, I., Małolepszy, A., Mazurkiewicz, M., Sto-binski, L., Kurzydłowski, K.J., Dobrowolski, W.: Phys. StatusSolidi A-Appl. Mat. 208, 1787–1790 (2011)11. Cornell, R.M., Schwertmann, U.: The iron oxides. structure,properties, reactions, occurrences and uses: structure, properties,reactions, occurrences and uses. Wiley-VCH, Weinheim (2003)12. Stobinski, L., Lesiak, B., Kover, L., Toth, J., Biniak, S.,Trykowski, G., Judek, J.: J. Alloys Compd. 501, 77–84 (2010)13. Hanga, B.T., Watanabe, I., Doi, T., Okada, S., Yamaki, J.I.: J.Power Sources 161, 1281–1287 (2006)14. Xie, K.Y., Li, J., Lai, Y.Q., Lu, W., Zhang, Z., Liu. Y.X.,Zhou, L.M., Huang, H.T.: Electrochem. Commun. 13, 657–660 (2011)

Journal of Superconductivity and Novel Magnetism

Preparation and Characterization of Hematite-Multiwall Carbon Nanotubes Nanocomposite

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Preparation and Characterization of Hematite-Multiwall Carbon Nanotubes Nanocomposite

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