Revista Mexicana de Fısica S58 (2) 134–137 DICIEMBRE 2012

Compositional, thermal and magnetic analysis of bamboo fibers covered withmagnetite nanoparticles by in-situ co-precipitation

S. Calvoa, N. Arias-Duqueb, O. Giraldob, and A. Rosales-Riveraa

aLaboratorio de Magnetismo y Materiales Avanzados, Facultad de Ciencias Exactas y Naturales,Universidad Nacional de Colombia, Sede Manizales, Manizales, Colombia.

bLaboratorio de Materiales Nanoestructurados y Funcionales, Facultad de Ciencias Exactas y Naturales,Sede Manizales, Manizales, Colombia.

e-mail: ohgiraldoo@unal.edu.co

Recibido el 25 de junio de 2010; aceptado el 29 de noviembre de 2010

Several angustifolia kunth bamboo fibers were covered with magnetite nanoparticles (MNPs) of Fe2+ and Fe3+ by in-situ co-precipitationmethod with NaOH or NH4OH. In natural and coated fibers, it was evaluated the global composition by atomic absorption (A.A) technique,structural charactererization by X-ray diffraction (XRD), thermal stability with thermogravimetric analysis (TGA) in nitrogen atmosphereat temperature range between 23◦C to 800◦C and magnetic behavior at room temperature using vibrating sample magnetometry (VSM)technique applying a magnetic field between -27000 Oe and 27000 Oe. The results show a dependence of thermal stability and magnetizationwith the synthesis method used for covering the angustifolia kunth bamboo fibers, where an improved magnetic response was observed whenNaOH solution is used for coated fibers.

Keywords: Magnetite; angustifolia kunth bamboo; magnetization; in-situ co-precipitation.

Se recubrieron fibras de guadua angustifolia kunth con nanopartıculas de magnetita (NPsM) mediante el metodo de co-precipitacion in-situde Fe2+ y Fe3+ en NH4OH o en NaOH. Para las fibras naturales y recubiertas se evaluo: la composicion global por medio de la tecnica deabsorcion atomica (A.A.), la estructura mediante difraccion de rayos X (XRD), la estabilidad termica mediante analisis termogravimetrico(TGA) en atmosfera de nitrogeno en un rango de 23◦C a 800◦C y el comportamiento magnetico se evaluo mediante magnetometrıa demuestra vibrante (VSM) a temperatura ambiente en un rango de -27000 Oe a 27000 Oe. Los resultados mostraron una dependencia de laestabilidad termica y del comportamiento magnetico con el metodo de sıntesis utilizado en el recubrimiento de la fibra de guadua angustifoliakunth, observandose mejor respuesta magnetica cuando se utilizo la solucion NaOH.

Descriptores: Magnetita; guadua angustifolia kunth; magnetizacion; co-precipitacion in-situ.

PACS: 75.50.Gg; 75.75.Cd; 61.05.cp

1. Introduction

The angustifolia bamboo is the most common native bam-boo in tropical America, being the angustifolia kunth kind,the most important one in Colombia. Morphologically, thisspecies of bamboo can be distinguished by the followingparts: root, stem, leaves, flowers and fruits, of which thestem, and particularly the culm, has been used for differentapplications in the field of architecture and civil engineering,as these parts have very interesting mechanical properties likethe resistance to tension and its flexibility [1]. The culmsand stems of the bamboo are largely comprised of fibers,which in turn are composed of cellulose, hemi-cellulose andlignin [2]. These fibers have very interesting mechanicalproperties; they possess a tensile strength which is compa-rable with the resistance of some major natural and syntheticfibers currently used in concrete reinforcement. [1].

One of the qualities of natural fibers composed of ligno-cellulose as the bamboo fibers is the ability to incorporatemagnetic materials which has been very useful in prepar-ing magnetic paper, having great properties for use in elec-tromagnetic shielding building, paper to record information,magnetograph printing, etc... [3].

Magnetite (Fe3O4) is a magnetic material of great inter-est to be incorporated in natural fibers, since they have somevery interesting properties such as: very low coercive fields,superparamegnetic behavior, ease to be attracted to sourcesof magnetic field [4]. These particles also have other qual-ities such as their compatibility with biological systems andhigh effective surface area [5].

The magnetic properties of magnetite nanoparticles andmechanical properties of bamboo fibers represent the advan-tage of generating a hybrid material combining both quali-ties. Nowadays, there are two types of synthesis methodsfor incorporated magnetic nanoparticles to surfaces of ligno-cellulosic material like kenaf and kraft to the best of the au-thors’ knowledge, reported in the scientific literature. Theseare as follow: (1) lumen loading process; (2) in-situ co-precipitation synthesis [6]. In the first method, the magneticparticles are surrounded by cell walls inside the fibers (lu-men) [7], allowing them to keep some mechanical propertiesof the fiber, but restricting the effective surface of the parti-cles for potential applications as support [8]. In the secondmethod, the magnetic particles are formed in the presence ofnatural fibers allowing them to attach the magnetite in theouter fibers, This kind of synthesis offers greater control ofthe magnetic properties and the variety of magnetic particles

COMPOSITIONAL, THERMAL AND MAGNETIC ANALYSIS OF BAMBOO FIBERS COVERED WITH MAGNETITE. . . 135

can be incorporated into the final product which allows a highspecific surface, important for the development of catalyticapplications [9].

In this paper, we used the synthesis of in-situ co-precipitation for covering natural fibers of angustifolia kunthbamboo with magnetite nanoparticles. We used two differentalkaline solutions (NaOH and NH4OH) for the synthesis ofmagnetite nanoparticles. Compositional, structural, thermaland magnetic characterizations were developed to evaluatethe effect of alkaline solution in the behavior of synthesizedmaterial. To the best of the authors’ knowledge, this is thefirst time that angustifolia kunt bamboo fibers were coveredwith magnetite.

2. Materials and experimental methods

Materials

The materials used in this research were as follow: Angustin-folia kunth bamboo fibers of 50 mm x 0.5 mm, Fe(III) chlo-ride 97%-102% Carlo Erba, Fe(II) chloride 102.7% JT Baker,sodium hydroxide 99% Carlo Erba and ammonium hydrox-ide 25% Aldrich.

Samples preparation

The Fe (II) and Fe (III) chloride solutions of 0.2 M and 0.3 Mconcentration, respectively, were mixed by continuous mag-netic stirring, subsequently bamboo fibers were added understirring leaving for a period of time. Next, alkaline solution(NaOH or NH4OH) 4 M was added drop by drop and the sus-pension color changed from red to black, indicating the for-mation of magnetite (Fe3O4) nanoparticles. This suspensionwas left in agitation for 24 h. The covered fibers were re-moved and washed three times with deionized distilled water(DDW) and a last additional washing with acetone. Finally,these fibers were dried for 3 days at 30◦C.

The samples were labeled as FG-0, FG-1, and FG-3 (seeTable I):

Characterization

Elemental analysis by Atomic Absorption (AA):AA wascarried out in a Perkin Elmer 3110. The samples were cal-cinated and digested in HCl and HF solutions in order to findthe global metal composition.Thermogravimetric analysis (TGA):for the evaluation ofthermal stability of materials, the samples were subjected toTGA studies using a TA instrument Q500. An analysis was

TABLE I. Label of fibers

Name Fiber Type

FG-0 Raw natural fiber

FG-1 Fibers covered with magnetite In NaOH solution

FG-4 Fibers covered with magnetite in NH4OH solution

performed from room temperature to 800◦C at a heating rateof 5◦C/min in a nitrogen atmosphere.X-ray diffraction patterns (XRD): the X-ray diffractionpatterns of the samples were obtained using a Siemensdiffractometer Rigaku MiniFlex II with Cu Kα radiation(λ = 1.540562 A) in the 2θ range of 3–70◦, at a voltageof 30 kV, current of 15mA and scan rate of 5◦/min.Vibrating Sample magnetometer (VSM):the hysteresiscycles of the samples were obtained using a VibratingSample Magnetometer (VSM)-VersaLab, Quantum Design,Inc. The dc applied field (H) was varied in the range−27≤H≤27 kOe. Data were obtained for consecutiveH = 0.1 kOe steps, stabilizingH before each reading, atT = 300 K.

3. Results and discussion

Global Composition

Table II shows the presence of Fe in the materials. The FG-1sample has higher Fe content than the FG-4 sample. This factsuggests a deposition, more efficient of magnetite on the sur-face of the bamboo fibers. The remaining metals analyzed didnot show significant changes with the treatment performed.

TABLE II. Global Composition of metals (%w)

Global Composition (%)

Sample K Fe Ca Mg Si Na

FG-0 0.54 0.01 0.03 0.01 0.04 0.01

FG-1 0.02 4.81 0.02 0.01 0.09 0.48

FG-4 0.02 2.46 0.03 0.01 0.04 0.03

FIGURE 1. XRD patterns of fibers: (a) FG-0, (b) FG-1, and(c) FG-4.

Rev. Mex. Fis. S58 (2) (2012) 134–137

136 S. CALVO, N. ARIAS-DUQUE, O. GIRALDO, AND A. ROSALES-RIVERA

FIGURE 2. TGA curves: FG-0, FG-1 and FG-4 at heating rateR=5◦C/min.

XRD Analysis

Figure 1 shows the diffraction pattern of the materials usedin this study. All samples exhibit characteristic diffractionspeaks of celluloseα andβ, localized at 5.9A and 4.12A[ref]. These peaks are related to the crystallographic planesof native cellulose; also, this type of cellulose is very com-mon in materials from plant sources such as wood [10]. Forthe FG-4 sample, the second peak moved slightly towards ahigher angle of diffraction, suggesting a change in the cellu-lose structure.

The FG-1 and FG-4 samples present additional diffrac-tion peaks localized at angles of 34.8◦ 2θ (Fig. 1b) and35.04◦ 2θ (Fig. 1c), respectively. These peaks are relatedwith crystallographic plane(311) characteristic of magnetitestructure as reported in the literature [11].

Thermal Analysis (TGA)

The Fig. 1 and Table III show a difference in mass losses ofthe analyzed materials. Losses below 200◦C can be assignedto physisorbed water. For the FG-O sample, the weight lossbetween 200◦C and 360◦C are due to the decomposition ofhemi-cellulose [12], above 360◦C temperature decarboxyla-tion reactions occur to form aldehydes, ketones and esters [3]and finally there is the carbon formation [13].

The weight loss in these regions for other materials FG-1and FG-4, suggest a cooperative effect of decomposition ofthe organic matrix and structural phase changes of magnetiteto maghemite (270◦C) and its transformation to hematite(480◦C) [14].

Magnetic Measurements

Figure 3 shows the hysteresis cycles for each of the fibers, co-ercivity and remnant magnetization is not evident, but thereare changes in the magnetization, taking a paramagnetic be-havior for FG-0 sample and a ferromagnetic behavior for

TABLE III. Lost weight bamboo fibers (TGA)

SampleTemperature Range (◦C)

23 -200 200-350 360-600 600-800

FG-0 8.44% 49.2% 34.87% 7.73%

FG-1 8.08% 46.04% 38.82% 7.29%

FG-4 5.99% 54.17% 33.7% 6.73%

FIGURE 3. Hysteresis cycles showing the differences in magneticbehavior between the FG-0, FG-1 and FG-4 samples, at room tem-perature.

FG-1 and FG-4 samples. It is also noted that the FG-1 sampleshows better magnetic response given by increased presenceof iron (see Table II); this is indicative of a higher amount ofmagnetite nanoparticles by covering the fibers.

The FG-1 and FG-4 samples did not display saturationat H = 27 kOe, this is due to the nanoparticles of magnetitehosted in the fibers, as these present a superparamagnetic be-havior and the saturation field is aroundH = 50 kOe [15].

4. Conclusions

Angustifolia kunth bamboo fibers were covered with mag-netite nanoparticles using two types of alkaline solutions(NaOH or NH4OH) which caused a change in the magne-tization of natural fibers, becoming from paramagnetic to aferromagnetic material. We also observed a difference in themagnetization depending on an alkaline solution used in thesynthesis, probably associated to a variation in the iron con-tent, since the sample with highest content of iron, showed ahigher magnetization.

We can conclude that the NaOH solution increased theformation of magnetite in the surface of angustifolia kuntbamboo fibers. According to tour knowledge, this is the firsttime that angustifolia kunt bamboo fibers were covered withmagnetite nanoparticles.

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COMPOSITIONAL, THERMAL AND MAGNETIC ANALYSIS OF BAMBOO FIBERS COVERED WITH MAGNETITE. . . 137

Acknowledgements

Research work at Universidad Nacional de Colombia, Branchof Manizales is supported by the Research Office (DIMA)under Financial Aid for Postgraduate Programs.

1. L. Moreno, L. Osorio, and E. Trujillo,Ingenierıa & Desarrollo.20 (2006) 125-133.

2. X. Londono, G. Camayo, N. Riano, and Y. Lopez,The Journalof the American Bamboo Society.16 (2002) 13-31.

3. C.H. Chia, S. Zakaria, K.L. Nguyen, and M. Abdul-lah,Iindustrial crops and products.28 (2008) 333–339.

4. T. Hosono, H. Takahashi, A. Fujita, R. JustinJoseyphus, K. To-hji, and B. JeyadevanJournal of Magnetism and Magnetic Ma-terials.321(2009) 3019–3023.

5. A.S. Lubbe, C. Bergemann, J. Brock, and D.G. Mc-Clure,Journal of Magnetism and Magnetic Materials194(1999) 149-155.

6. A.C. Small J.H. Johnston,Journal of Colloid and Interface Sci-ence.331(2009) 122–126.

7. S. Zakaria, B.H. Ong, S.H. Ahmad, M. Abdullah, and T. Ya-mauchi,Materials Chemistry and Physics, 89 (2005) 216–220.

8. S. Zakaria, B.H. Ong, and T.G.M. van de Ven,Colloids andSurfaces A: Physicochem. Eng. Aspects.251(2004) 31–36.

9. K. Can, M. Ozmen, and M. Ersoz,Colloids and Surfaces B:Biointerfaces. 71 (2009) 154–159.

10. M. Deramanet al.,Journal of materials science letters18(1999) 249-253.

11. X. Wen, J. Yang, B. He, and Z. GuCurrent Applied Physics8(2008) 535-541.

12. H. Yang, R. Yan, H. Chen, D. Ho Lee, and C. Zheng,Fuel.86(2007) 1781–1788.

13. K. Xie, X. Gao, and W. Zhao,Carbohydrate Polymers.81(2010) 300–304.

14. J. Mazo, C.A. Barrero1, J. Dıaz, and A. Jerez,Hyperfine Inter-actions. 148/149(2003) 153–161.

15. J. Giri, S.G. Thakurta, J. Bellare, A.K. Nigam, and D. Bahadur,Journal of Magnetism and Magnetic Materials.293(2005) 62–68.

Rev. Mex. Fis. S58 (2) (2012) 134–137