research article sonochemical synthesis of cobalt...

Hindawi Publishing CorporationInternational Journal of Chemical EngineeringVolume 2013 Article ID 934234 6 pageshttpdxdoiorg1011552013934234

Research ArticleSonochemical Synthesis of Cobalt Ferrite Nanoparticles

Partha P Goswami1 Hanif A Choudhury2

Sankar Chakma1 and Vijayanand S Moholkar12

1 Department of Chemical Engineering Indian Institute of Technology Guwahati Guwahati Assam 781 039 India2 Center for Energy Indian Institute of Technology Guwahati Guwahati Assam 781 039 India

Correspondence should be addressed to Vijayanand S Moholkar vmoholkariitgernetin

Received 8 August 2013 Revised 28 September 2013 Accepted 4 October 2013

Academic Editor Jose C Merchuk

Copyright copy 2013 Partha P Goswami et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Cobalt ferrite being a hardmagneticmaterial with high coercivity andmoderatemagnetization has foundwide-spread applicationsIn this paper we have reported the sonochemical synthesis of cobalt ferrite nanoparticles usingmetal acetate precursorsThe ferritesynthesis occurs in three steps (hydrolysis of acetates oxidation of hydroxides and in situmicrocalcination ofmetal oxides) that arefacilitated by physical and chemical effects of cavitation bubbles The physical and magnetic properties of the ferrite nano-particlesthus synthesized have been found to be comparable with those reported in the literature using other synthesis techniques

1 Introduction

The spinel ferrite nanoparticles have exceptional electronicand magnetic properties which are quite different from thebulk materials [1] As a result the magnetic ferrite nanopar-ticles have found wide applications in information storagesystems ferrofluids and medical applications like magneticdrug delivery and hyperthermia for cancer treatment [2]Among metal ferrites zinc nickel and cobalt ferrites havebeen mostly applied Cobalt ferrite (CoFe

2O4) is a hard

magnetic material that is known to have high coercivityand moderate magnetization [3] On nanoscale the cobaltferrite achieves properties of high saturation magnetizationhigh coercivity strong anisotropy highmechanical hardnessand high chemical stability [4] Conventional techniquesfor synthesis of metal nanoparticles (including cobalt ferriteparticles) are sol-gel method [5 6] microemulsions [7 8]reverse micelles [9] autocombustion [10] and coprecipita-tion [11] A relatively new technique for synthesis of ferritenanoparticles is the sonochemical route [12ndash16] in which thereaction mixture is exposed to ultrasound irradiation Spec-tacular physical and chemical effects induced by ultrasoundbring about the synthesis of metal ferrites from the metalsalt precursors usually acetates The hydrolysis of acetates

followed by oxidation of the hydroxides to oxides and thereaction between oxides to yield ferrites is brought aboutby ultrasound and its secondary effect cavitation Cavitationis essentially nucleation growth and transient implosivecollapse of gas bubbles driven by ultrasound wave [17] Thistechnique has been well demonstrated for zinc ferrites Inour previous papers [15 16] we have tried to illuminate thelinks between physics of ultrasound and cavitation and thechemistry of zinc ferrite nanoparticles It was revealed inthese studies that chemical species produced during transientcavitation induce the hydrolysis and oxidation of hydroxideswhile shock waves generated by transient cavitation bringabout the calcination of metal oxides to form ferrites [18]

In this study we have extended the same theme for syn-thesis of cobalt ferrite We would like to specifically mentionthat sonochemical preparation of cobalt ferrite nanoparticleshas already been reported by Shafi et al [19] Howeverin their study the precursors were the metal carbonylswhichwere sonochemically decomposed in decalin solvent toyield amorphous oxides that further reacted to form ferrites(with external calcination at 450 and 700∘C) that also hadamorphous character The major problem with this route isthe use of toxic and hazardous metal carbonyl precursorsOur approach is more environmentally friendly in that the

2 International Journal of Chemical Engineering

REMIHeat Stirring

Time 03000 Temp -- -- Pulse -- -- Amp 20

7

1 20

34 5 6

8 9

4

2

3

1

5

Waterbath 6

Figure 1 Schematic diagram of experimental setup for sonochemical synthesis of manganese ferrite (1) Sonic processor (2) transducer (3)reaction mixture (4) magnetic stirrer with hot plate (5) stand and (6) water cooler

precursors used by us are cobalt acetate and iron (II) acetateThe characterization of the particles has been made usingXRD FE-SEM and VSM

2 Materials and Methods

The experimental parameters as well as analysis in thispaper are based on results of these previous papers as wellas some preliminary studies (not reported in this paper)The main hypothesis on which this paper is based is thatphysical and chemical effects of cavitation bubbles inducethe chemistry of ferrite synthesis The metal acetates firstundergo hydrolysis thermal decomposition and oxidationof hydroxides thus formed gives metal oxides which areinsoluble and precipitate in reaction mixture The metaloxide particles get drifted in the shock waves generated bycavitation bubbles and collide at high velocities The energygenerated from these collisions can induce reaction leadingto formation of ferrites All of these steps have been wellproven by previous researchers Sonochemical hydrolysisand thermal decomposition are well-known reactions (forexample Kotronarou et al [20]) High energy collisionsbetween particles induced by shock waves have also beenproven by Doktycz and Suslick in a landmark paper [18]

21 Materials The following chemicals have been used forthe synthesis cobalt acetate tetrahydrate (AR Grade Merck)iron (II) acetate (AR Grade Alfa Aesar) and NaOH pellets(Merck) All chemicals were used as received without anyfurther purification All the reaction mixtures were preparedusing deionized water from Milli-Q Synthesis unit (ModelElix 3 Millipore USA)

22 Experimental Setup A schematic diagram of the exper-imental setup is shown in Figure 1 All experiments werecarried out with 20mL of Millipore water in a borosili-cate glass beaker A desired amount of cobalt acetate wastaken with iron (II) acetate and was placed on a hot plate(Remi Equipments Ltd Model 1-MLH) The ultrasound

was applied for 30min using a high grade titanium alloyultrasonic probe (dia 13mm) with a frequency of 20 kHz(Model VCX-500 20 kHz 500W) The probe was operatedat 20 amplitude with theoretical power dissipation of 100W(500W times 020 = 100W) The microprocessor based controlunit of the processor had facilities of automatic frequencytuning and amplitude compensation which delivers constantpower to the reaction mixture during the sonication periodirrespective of the changes occurring in the reactionmediumThe acoustic pressure amplitude generated by the ultrasoundprobewasmeasured using calorimetricmethod asmentionedby Sivasankar et al [21] For 20 of the theoretical maximumpower the pressure amplitude produced by the probe wasdetermined as 15 bar

23 Synthesis Procedure An amount of 0708 g of cobaltacetate (02M) was taken in a 20mL of Millipore water with139 g of iron (II) acetate (04M) making the molar ratioof cobalt acetate to iron (II) acetate 1 2 The solution wassubjected to sonication for 30min in a pulse mode (20 s onminus5 s off) with actual total sonication time of 24min Thetemperature of the solution was maintained at 70∘C (plusmn4∘C)during the experimentThe initial pH of the reactionmixturein all protocols was 45 The pH of the solution was adjustedto the desire value by dropwise addition of either 01 NNaOHor 01 N HCl No external H

2O2was added to the reaction

mixture during the synthesis of cobalt ferrite nanoparticlesas required for the oxidation of ferrous hydroxide The exactchemistry of the cobalt ferrite synthesis is given by followingchemical reactions

Fe(CH3COO)

2+ 2H2O 997888rarr Fe(OH)

2+ 2CH

3COOH

3Fe(OH)2+H2O2997888rarr Fe

3O4+ 4H2O

Co(CH3COO)

2+ 2H2O 997888rarr CoO + 2CH

3COOH + 2H

2O

2Fe3O4+ 3CoO

[O]997888rarr

ultrasoundcavitation3CoFe

2O4

(1)

International Journal of Chemical Engineering 3

Transient cavitation in the reaction mixture leads to in-situgeneration of H

2O2as follows During expansion of the

cavitation bubble large amount of water vapor evaporatesinto the bubble and diffuses to the core of the bubble Duringthe ensuing compression phase the bubble contracts and thevapor starts diffusing back to the bubble wall (or gas-liquidinterface) However during final moments of the collapsethe bubble wall velocity becomes extremely fast and all of thevapor that has entered the bubble cannot escape (or diffuseback to the bubble wall and condense) This water vaporgets entrapped in the bubble and is subjected to extremeconditions (sim5000K temperature and sim500 bar pressure)generated in the bubble at the moment of transient collapseand undergoes dissociation to generate radicals [22]

H2O 997888rarr H∙ + ∙OH (2)

The hydroxyl radicals generated by the bubble can recombineto yield hydrogen peroxide that leads to oxidation of hydrox-ide to oxides

∙OH+ ∙OH 997888rarr H2O2

H2O +O∙ 997888rarr ∙OH+ ∙OH

H2O +H∙ 997888rarr ∙OH+H

2

HO∙2+H∙ 997888rarr ∙OH+ ∙OH

(3)

Alternatively direct thermal decomposition of hydroxideparticles can also occur in the thin liquid shell surroundingthe cavitation bubble in which the temperature reaches mod-erately high values (sim400ndash600K) at the moment of transientcollapse of the cavitation bubbles [20 23] In our previouspapers [24ndash32] we have reported extensive simulations ofcavitation bubble dynamics using the diffusion limitedmodelof Toegel et al [33] under variety of conditions that givequantitative confirmation of above physical and chemicaleffects of cavitation bubble dynamics We refer the interestedreaders to these papers for greater details on this subject

A blackish solid precipitate was obtained as a productafter 30min of sonication The precipitate was separatedby centrifugation for 20min at 6000 rpm (make HermileModel Z300) The solid product was then dried in a hot airoven for overnight at 100∘C and characterized using powderX-ray diffraction (make Bruker Model Advanced D8) toascertain formation of ferrite phase

In an interesting paper Dang et al [38] have reportedthe sonochemical synthesis of BaTiO

3particles through sol

suspension route using BaCl2and TiCl

4precursors In a

subsequent paper Yasui and Kato [39] have presented anumerical simulation of oriented aggregation of sonochemi-cally synthesized BaTiO

3nanocrystals In the study of Dang

et al [38] the Ti-based sol suspension was obtained by firstpreparing a solution of BaCl

2and later adding TiCl

4to it

Later the pH of the sol suspension was adjusted to 14 withtemperature being 80∘C This suspension was sonicated atdifferent power levels to yield BaTiO

3due to reaction induced

between colloidal particles by collisions between them drivenby transient cavitation events A similar route such as thismay

2400

2100

1800

1500

1200

90020 30 40 50 60 70

2120579 (deg)

Inte

nsity

(au

)

(220

)

(311

)

(400

) (511

) (440

)

Figure 2 X-ray diffraction spectra of CoFe2O4(without external

calcination) at room temperature

also occur in the present case leading to ferrite formationHowever we are unable to distinguish between this route andthe mechanism that we have proposed above

24 Characterization of the Solid Product It should be specif-ically mentioned that external calcination was not applied tothe solid product obtained after sonication Characterizationof the dried solid powder resulting from experiments wasdone using X-ray powder diffractometer (make BrukerModel Advanced D8) with monochromatic CuK

120572(120582 =

15406 A) radiation operated at 40 kV and 40mA in therange from 20 to 70∘ The mean crystallite particle size(119863xrd) of the product was calculated from the most intensepeak observed at (311) using Debye-Scherer equation [4041] 119863xrd = 09 times 120582(120573 times cos 120579) where 120582 is the X-raywavelength 120573 is the half width of the relevant diffractionpeak and 120579 is the Braggrsquos angle The morphology of thecobalt ferrite nano-particles was determined using fieldemission scanning electron microscope (FE-SEM ModelSIGMAVP make Carl Zeiss Microscopy GmbH Germany)The magnetic characteristics of the ferrite particles weredetermined using vibrating sample magnetometer (VSMmake Lakeshor Model 7410)

3 Results and Discussion

The results of the experiments have been presented in Figures2 3 and 4 The X-ray diffractogram of the solid productwas obtained after sonication The diffraction peaks corre-sponding to characteristic crystallographic planes at spinelstructure of ferrites [(220) (311) (400) (511) and (440)] areevident in Figure 2 The ferrite phase is relatively pure in thatno presence of other phases like hematite [(120572-Fe

2O3) between

(220) and (311) or Fe3O4at (333)] or cobalt oxide is seen The

average crystal size of particles as calculated from Debye-Scherer formula is 24 nm It is noteworthy that the cobaltferrite was formed during sonication itself without externalcalcination of the material confirms our earlier hypothesis


200 nm

(a)

200 nm

(b)

Figure 3 FE-SEM images of cobalt ferrite (a) 64KX and (b) 100KX

minus30

minus20

minus10

0

10

20

30

minus11000 minus7000 minus3000 1000 5000 9000

M (e

mu

g)

H (Oe)

Figure 4 Room temperature M-H curve for CoFe2O4

of in-situ micro-calcination of the oxide precursors induceddue to the energetic collisions between the particles as theyget drifted in high pressure amplitude shock wave generatedby the cavitation bubble The FE-SEM micrographs of theas-synthesized ferrite particles are shown in Figure 3 Thesemicrographs show agglomerates of nearly spherical particlesDetermination of exact particle size from these pictures isthus difficult Nonetheless the crystalline structure of theparticles can be deduced from the uniformity of the particlesizes The room temperature magnetization curve of theas-synthesized cobalt ferrite particles is given in Figure 4The saturation magnetization of the sample is 257 emugwith magnetic remanence of 878 emug These values aremuch smaller than the magnetic saturation reported for bulkCoFe2O4material that is 72 emug [19 42] Significantly

lower values of saturation magnetization observed for ourparticles confirm its nanocrystalline nature Shafi et al [19]have discussed possible causes that lead to this effect Thesize of the magnetic particle determines its energy in anexternal field This relation is essentially through the numberof magnetic molecules in an individual magnetic domain

With reduction in particle size the energy of the par-ticle decreases As the energy becomes comparable to 119896119879(119896 Boltzmann constant 119879 Temperature) thermal fluctua-tions will dominate causing reduction in the total magneticmomentThe reduction in saturationmagnetization could beconsequence of noncollinear spin arrangement Cobalt ferriteis essentially an inverse spinel with collinear ferrimagneticspin structure in the bulk form However for particle size innanorange there could be non-collinear spin arrangementat or near the surface of the particle that causes reductionin saturation magnetization Another property which isof relevance to saturation magnetization is the surface-to-volume ratio The larger this ratio (as for the particles innanometer range) the magnetic molecules on surface lackproper coordination due to which their spins are disturbedand total magnetization is reduced Goodarz Naseri et al[34] have reported that the relationship between coercivityfield and remanence ratio and the saturation magnetizationis not simple in that no definite trends are observed GoodarzNaseri et al [34] have concluded that the value of remanenceratio (119877) which varies between 0 and 1 is representative ofexistence or absence of different types of intergrain groupexchanges For 119877 lt 05 the particles interact by magneto-static interaction while 119877 = 05 indicates randomly orientednoninteracting particles which undergo coherent rotationsFor 05 lt 119877 lt 1 indicates existence of exchange couplingparticles According to this criterion the particles interactionin the as-synthesized cobalt ferrite is through magnetostaticinteraction

Table 1 gives a comparative account of the results ofpresent study with published literature It could be seenthat the particle size as well as magnetization characteristicsof the as-synthesized particles is at par with the particlessynthesized using conventional techniques

4 Conclusion

In this study we have explored the sonochemical route ofsynthesis of cobalt ferrite nano-particles The precursorsare the metal acetates that are hydrolyzed and oxidizedunder ultrasound irradiation to form metal oxides In-situmicrocalcination of the oxide particles induced due to high


Table 1 Characterization of cobalt ferrite nanoparticles and comparison with the literature

Method of synthesis Particle size (nm) Coercivity (Oe) Magnetic saturation119872119904(emug)

Magnetic remanence119872119903(emug)

Remanence ratio(119877 = 119872

119903119872119904)

Present study 24 1049 257(No calcination) 878 0341

Autocombustion [10] 227 760 2446(Tcalc = 200∘C) 880 0359

Sonochemical synthesisthrough carbonyl route [19] lt10 ND

Superparamagneticbehavior without

calcination22

(Tcalc = 450∘C)45

(Tcalc = 700∘C)

ND ND

Thermal treatment [34] 41 1002 285(Tcalc = 650∘C) 1161 0407

Sol-gel [5] 15 1215 670(Tcalc = 570∘C) 302 045

Coprecipitation [35] 138 193 583(Tcalc = 80∘C) 165 028

Microemulsion [36] lt50 1440 650(Tcalc = 600∘C) 29 044

Mechanical Milling [37] 122 940 812(Tcalc = 22∘C) 5061 062

Tcalc calcination temperature ND not determined

energy collisions between the particles due to the shockwavesgenerated by cavitation bubble causes synthesis of ferriteMost notably no external calcination is needed Charac-terization of as-synthesized particles with XRD FE-SEMand VSM reveals that ferrite particles have inverse spinelcrystalline structure The physical and magnetic propertiesof the as-synthesized particles are comparable with thosesynthesized using conventional techniques

Conflict of Interests

Theauthors of this paper declare no conflict of interests of anykind

Acknowledgments

Authors gratefully acknowledge stimulating discussions withProffessor M Sivakumar (University of Nottingham Malay-sia) during the preliminary stage of project on sonochemicalferrite synthesis The authors also acknowledge the CentralInstruments Facility (CIF) of IIT Guwahati for providingSEM and VSM facility for analysis of ferrite samples

References

[1] M G Naseri and E B Saion ldquoCrystalization in spinel ferritenanoparticlesrdquo inAdvances in Crystallization Processes pp 349ndash380 2012

[2] E C Snelling Soft Ferrites Properties and Applications Butter-worth London UK 2nd edition 1989

[3] K Maaz A Mumtaz S K Hasanain and A Ceylan ldquoSynthesisand magnetic properties of cobalt ferrite (CoFe

2O4) nanoparti-

cles prepared by wet chemical routerdquo Journal of Magnetism andMagnetic Materials vol 308 no 2 pp 289ndash295 2007

[4] J-S Jung J-H Lim K-H Choi et al ldquoCoFe2O4nanostructures

with high coercivityrdquo Journal of Applied Physics vol 97 no 10Article ID 10F306 pp 1ndash3 2005

[5] B G Toksha S E Shirsath S M Patange and K M JadhavldquoStructural investigations and magnetic properties of cobaltferrite nanoparticles prepared by sol-gel auto combustionmeth-odrdquo Solid State Communications vol 147 no 11-12 pp 479ndash4832008

[6] K Winiarska I Szczygieł and R Klimkiewicz ldquoMangan-eseminuszinc ferrite synthesis by the solminusgel autocombustion meth-od Effect of the precursor on the ferritersquos catalytic propertiesrdquoIndustrial and Engineering Chemistry Research vol 52 pp 353ndash361 2013

[7] Y Ahn E J Choi S Kim and H N Ok ldquoMagnetization andMossbauer study of cobalt ferrite particles from nanophase co-balt iron carbonaterdquo Materials Letters vol 50 no 1 pp 47ndash522001

[8] D O Yener andH Giesche ldquoSynthesis of pure andmanganese-nickel- and zinc-doped ferrite particles in water-in-oil microe-mulsionsrdquo Journal of the American Ceramic Society vol 84 no9 pp 1987ndash1995 2001

[9] Y Lee J Lee C J Bae et al ldquoLarge-scale synthesis of uniformand crystalline magnetite nanoparticles using reverse micellesas nanoreactors under reflux conditionsrdquo Advanced FunctionalMaterials vol 15 pp 503ndash509 2005

[10] S H Xiao W F Jiang L Y Li and X J Li ldquoLow-temperatureauto-combustion synthesis and magnetic properties of cobaltferrite nanopowderrdquo Materials Chemistry and Physics vol 106no 1 pp 82ndash87 2007


[11] I Elahi R Zahira K Mehmood A Jamil and N Amin ldquoCo-precipitation synthesis physical and magnetic properties ofmanganese ferrite powderrdquo African Journal of Pure and AppliedChemistry vol 6 pp 1ndash5 2012

[12] M Sivakumar A Gedanken W Zhong et al ldquoNanophase for-mation of strontium hexaferrite fine powder by the sonochemi-cal method using Fe(CO)

5rdquo Journal of Magnetism andMagnetic

Materials vol 268 no 1-2 pp 95ndash104 2004[13] M Sivakumar A Gedanken D Bhattacharya et al ldquoSono-

chemical synthesis of nanocrystalline rare earth orthoferritesusing Fe(CO)

5precursorrdquo Chemistry of Materials vol 16 no

19 pp 3623ndash3632 2004[14] M Sivakumar A Gedanken W Zhong et al ldquoSonochemical

synthesis of nanocrystalline LaFeO3rdquo Journal of Materials

Chemistry vol 14 no 4 pp 764ndash769 2004[15] B R Reddy T Sivasankar M Sivakumar and V S Moholkar

ldquoPhysical facets of ultrasonic cavitational synthesis of zincferrite particlesrdquo Ultrasonics Sonochemistry vol 17 no 2 pp416ndash426 2010

[16] H A Choudhury A Choudhary M Sivakumar and V SMoholkar ldquoMechanistic investigation of the sonochemical syn-thesis of zinc ferriterdquo Ultrasonics Sonochemistry vol 20 pp294ndash302 2013

[17] K S Suslick Ultrasound Its Chemical Physical and BiologicalEffects VCH New York NY USA 1998

[18] S J Doktycz and K S Suslick ldquoInterparticle collisions drivenby ultrasoundrdquo Science vol 247 no 4946 pp 1067ndash1069 1990

[19] K V P M Shafi A Gedanken R Prozorov and J BaloghldquoSonochemical preparation and size-dependent properties ofnanostructured CoFe

2O4particlesrdquo Chemistry of Materials vol

10 no 11 pp 3445ndash3450 1998[20] A Kotronarou G Mills and M R Hoffmann ldquoUltrasonic

irradiation of p-nitrophenol in aqueous solutionrdquo Journal ofPhysical Chemistry vol 95 no 9 pp 3630ndash3638 1991

[21] T Sivasankar AW Paunikar and V S Moholkar ldquoMechanisticapproach to enhancement of the yield of a sonochemicalreactionrdquo AIChE Journal vol 53 no 5 pp 1132ndash1143 2007

[22] K S Suslick ldquoSonochemistryrdquo Science vol 247 no 4949 pp1439ndash1445 1990

[23] I Hua R H Hochemer and M R Hoffmann ldquoSonpchemicaldegradation of p-nitrophenol in a parallel-plate near-fieldacoustical processorrdquo Environmental Science and Technologyvol 29 no 11 pp 2790ndash2796 1995

[24] J S Krishnan P Dwivedi and V S Moholkar ldquoNumericalinvestigation into the chemistry induced by hydrodynamiccavitationrdquo Industrial and Engineering Chemistry Research vol45 no 4 pp 1493ndash1504 2006

[25] S Chakma and V S Moholkar ldquoNumerical simulation andinvestigation of system parameters of sonochemical processrdquoChinese Journal of Engineering vol 2013 Article ID 362682 14pages 2013

[26] T Sivasankar and V S Moholkar ldquoMechanistic features ofthe sonochemical degradation of organic pollutantsrdquo AIChEJournal vol 54 no 8 pp 2206ndash2219 2008

[27] T Sivasankar and V S Moholkar ldquoPhysical features of sono-chemical degradation of nitroaromatic pollutantsrdquo Chemo-sphere vol 72 no 11 pp 1795ndash1806 2008

[28] T Sivasankar and V S Moholkar ldquoMechanistic approach tointensification of sonochemical degradation of phenolrdquo Chem-ical Engineering Journal vol 149 no 1ndash3 pp 57ndash69 2009

[29] T Sivasankar and V S Moholkar ldquoPhysical insight into thesonochemical degradation of 24-dichlorophenolrdquo Environ-mental Technology vol 31 no 14 pp 1483ndash1494 2010

[30] T Sivasankar and V S Moholkar ldquoPhysical insights into thesonochemical degradation of recalcitrant organic pollutantswith cavitation bubble dynamicsrdquo Ultrasonics Sonochemistryvol 16 no 6 pp 769ndash781 2009

[31] S Chakma and V S Moholkar ldquoPhysical mechanism of sono-fenton processrdquo AIChE Journal vol 59 no 11 pp 4303ndash43132013

[32] N K Morya P K Iyer and V S Moholkar ldquoA physical insightinto sonochemical emulsion polymerization with cavitationbubble dynamicsrdquo Polymer vol 49 no 7 pp 1910ndash1925 2008

[33] R Toegel B Gompf R Pecha and D Lohse ldquoDoes water vaporprevent upscaling sonoluminescencerdquo Physical Review Lettersvol 85 no 15 pp 3165ndash3168 2000

[34] M Goodarz Naseri E B Saion H Abbastabar Ahangar A HShaari and M Hashim ldquoSimple synthesis and characterizationof cobalt ferrite nanoparticles by a thermal treatment methodrdquoJournal of Nanomaterials vol 2010 Article ID 907686 8 pages2010

[35] Y I Kim D Kim and C S Lee ldquoSynthesis and characterizationof CoFe

2O4magnetic nanoparticles prepared by temperature-

controlled coprecipitation methodrdquo Physica B vol 337 no 1ndash4pp 42ndash51 2003

[36] V Pillai and D O Shah ldquoSynthesis of high-coercivity cobaltferrite particles using water-in-oil microemulsionsrdquo Journal ofMagnetism and Magnetic Materials vol 163 no 1-2 pp 243ndash248 1996

[37] E Manova B Kunev D Paneva et al ldquoMechano-synthesischaracterization and magnetic properties of nanoparticles ofcobalt ferrite CoFe

2O4rdquo Chemistry of Materials vol 16 no 26

pp 5689ndash5696 2004[38] F Dang K Kato H Imai S Wada H Haneda and M

Kuwabara ldquoCharacteristics of BaTiO3particles sonochemically

synthesized in aqueous solutionrdquo Japanese Journal of AppliedPhysics vol 48 no 9 Article ID 09KC02 2009

[39] K Yasui andK Kato ldquoNumerical simulations of oriented aggre-gation of sonochemically synthesized BaTiO

3nanocrystalsrdquo

Proceedings of Meetings on Acoustics vol 15 Article ID 045002pp 1ndash7 2012 163rd Meeting Acoustical Society of AmericaHong Kong

[40] V Musat O Potecasu R Belea and P Alexandru ldquoMagneticmaterials from co-precipitated ferrite nanoparticlesrdquo MaterialsScience and Engineering B vol 167 no 2 pp 85ndash90 2010

[41] Y Koseoglu F Alan M Tan R Yilgin and M Ozturk ldquoLowtemperature hydrothermal synthesis and characterization ofMn doped cobalt ferrite nanoparticlesrdquo Ceramics Internationalvol 38 no 5 pp 3625ndash3634 2012

[42] K Haneda and A H Morrish ldquoNoncollinear magnetic struc-ture of CoFe

2O4small particlesrdquo Journal of Applied Physics vol

63 no 8 pp 4258ndash4260 1988

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Chemical EngineeringInternational Journal of Antennas and

Propagation




Navigation and Observation



DistributedSensor Networks



REMIHeat Stirring

Time 03000 Temp -- -- Pulse -- -- Amp 20

7

1 20

34 5 6

8 9

4

2

3

1

5

Waterbath 6

Figure 1 Schematic diagram of experimental setup for sonochemical synthesis of manganese ferrite (1) Sonic processor (2) transducer (3)reaction mixture (4) magnetic stirrer with hot plate (5) stand and (6) water cooler

precursors used by us are cobalt acetate and iron (II) acetateThe characterization of the particles has been made usingXRD FE-SEM and VSM

2 Materials and Methods

The experimental parameters as well as analysis in thispaper are based on results of these previous papers as wellas some preliminary studies (not reported in this paper)The main hypothesis on which this paper is based is thatphysical and chemical effects of cavitation bubbles inducethe chemistry of ferrite synthesis The metal acetates firstundergo hydrolysis thermal decomposition and oxidationof hydroxides thus formed gives metal oxides which areinsoluble and precipitate in reaction mixture The metaloxide particles get drifted in the shock waves generated bycavitation bubbles and collide at high velocities The energygenerated from these collisions can induce reaction leadingto formation of ferrites All of these steps have been wellproven by previous researchers Sonochemical hydrolysisand thermal decomposition are well-known reactions (forexample Kotronarou et al [20]) High energy collisionsbetween particles induced by shock waves have also beenproven by Doktycz and Suslick in a landmark paper [18]

21 Materials The following chemicals have been used forthe synthesis cobalt acetate tetrahydrate (AR Grade Merck)iron (II) acetate (AR Grade Alfa Aesar) and NaOH pellets(Merck) All chemicals were used as received without anyfurther purification All the reaction mixtures were preparedusing deionized water from Milli-Q Synthesis unit (ModelElix 3 Millipore USA)

22 Experimental Setup A schematic diagram of the exper-imental setup is shown in Figure 1 All experiments werecarried out with 20mL of Millipore water in a borosili-cate glass beaker A desired amount of cobalt acetate wastaken with iron (II) acetate and was placed on a hot plate(Remi Equipments Ltd Model 1-MLH) The ultrasound

was applied for 30min using a high grade titanium alloyultrasonic probe (dia 13mm) with a frequency of 20 kHz(Model VCX-500 20 kHz 500W) The probe was operatedat 20 amplitude with theoretical power dissipation of 100W(500W times 020 = 100W) The microprocessor based controlunit of the processor had facilities of automatic frequencytuning and amplitude compensation which delivers constantpower to the reaction mixture during the sonication periodirrespective of the changes occurring in the reactionmediumThe acoustic pressure amplitude generated by the ultrasoundprobewasmeasured using calorimetricmethod asmentionedby Sivasankar et al [21] For 20 of the theoretical maximumpower the pressure amplitude produced by the probe wasdetermined as 15 bar

23 Synthesis Procedure An amount of 0708 g of cobaltacetate (02M) was taken in a 20mL of Millipore water with139 g of iron (II) acetate (04M) making the molar ratioof cobalt acetate to iron (II) acetate 1 2 The solution wassubjected to sonication for 30min in a pulse mode (20 s onminus5 s off) with actual total sonication time of 24min Thetemperature of the solution was maintained at 70∘C (plusmn4∘C)during the experimentThe initial pH of the reactionmixturein all protocols was 45 The pH of the solution was adjustedto the desire value by dropwise addition of either 01 NNaOHor 01 N HCl No external H

2O2was added to the reaction

mixture during the synthesis of cobalt ferrite nanoparticlesas required for the oxidation of ferrous hydroxide The exactchemistry of the cobalt ferrite synthesis is given by followingchemical reactions

Fe(CH3COO)

2+ 2H2O 997888rarr Fe(OH)

2+ 2CH

3COOH

3Fe(OH)2+H2O2997888rarr Fe

3O4+ 4H2O

Co(CH3COO)

2+ 2H2O 997888rarr CoO + 2CH

3COOH + 2H

2O

2Fe3O4+ 3CoO

[O]997888rarr

ultrasoundcavitation3CoFe

2O4

(1)





H2O 997888rarr H∙ + ∙OH (2)





2


(3)






4precursors In a





4to it




2400

2100

1800

1500

1200

90020 30 40 50 60 70

2120579 (deg)

Inte

nsity

(au

)

(220

)

(311

)

(400

) (511

) (440

)





120572(120582 =




2O3) between




200 nm

(a)

200 nm

(b)


minus30

minus20

minus10

0

10

20

30


M (e

mu

g)

H (Oe)






4 Conclusion







119903119872119904)





calcination22

(Tcalc = 450∘C)45

(Tcalc = 700∘C)

ND ND


Sol-gel [5] 15 1215 670(Tcalc = 570∘C) 302 045








Acknowledgments


References




2O4) nanoparti-




















































3nanocrystalsrdquo






63 no 8 pp 4258ndash4260 1988



RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation













H2O 997888rarr H∙ + ∙OH (2)





2


(3)






4precursors In a





4to it




2400

2100

1800

1500

1200

90020 30 40 50 60 70

2120579 (deg)

Inte

nsity

(au

)

(220

)

(311

)

(400

) (511

) (440

)





120572(120582 =




2O3) between




200 nm

(a)

200 nm

(b)


minus30

minus20

minus10

0

10

20

30


M (e

mu

g)

H (Oe)






4 Conclusion







119903119872119904)





calcination22

(Tcalc = 450∘C)45

(Tcalc = 700∘C)

ND ND


Sol-gel [5] 15 1215 670(Tcalc = 570∘C) 302 045








Acknowledgments


References




2O4) nanoparti-




















































3nanocrystalsrdquo






63 no 8 pp 4258ndash4260 1988



RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










200 nm

(a)

200 nm

(b)


minus30

minus20

minus10

0

10

20

30


M (e

mu

g)

H (Oe)






4 Conclusion







119903119872119904)





calcination22

(Tcalc = 450∘C)45

(Tcalc = 700∘C)

ND ND


Sol-gel [5] 15 1215 670(Tcalc = 570∘C) 302 045








Acknowledgments


References




2O4) nanoparti-




















































3nanocrystalsrdquo






63 no 8 pp 4258ndash4260 1988



RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation














119903119872119904)





calcination22

(Tcalc = 450∘C)45

(Tcalc = 700∘C)

ND ND


Sol-gel [5] 15 1215 670(Tcalc = 570∘C) 302 045








Acknowledgments


References




2O4) nanoparti-




















































3nanocrystalsrdquo






63 no 8 pp 4258ndash4260 1988



RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation



















































3nanocrystalsrdquo






63 no 8 pp 4258ndash4260 1988



RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation









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