research article reduction of electromagnetic interference...

Research ArticleReduction of Electromagnetic Interference Using ZnO-PCLNanocomposites at Microwave Frequency

Abubakar Yakubu1 Zulkifly Abbas1 Nor Azowa Ibrahim2 and Ahmad Fahad3

1Department of Physics Universiti Putra Malaysia (UPM) 43400 Serdang Selangor Malaysia2Department of Chemistry Universiti Putra Malaysia (UPM) 43400 Serdang Selangor Malaysia3Institute of Mathematical Research (INSPEM) Universiti Putra Malaysia (UPM) 43400 Serdang Malaysia

Correspondence should be addressed to Abubakar Yakubu abulect73yahoocom

Received 9 March 2015 Revised 21 May 2015 Accepted 26 May 2015

Academic Editor Markku Leskela

Copyright copy 2015 Abubakar Yakubu 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

In industrial equipment and home appliance applications the electromagnetic compatibility compliance directive (ECCD)demands that electromagnetic interference side effects be eliminated or marginally minimized The equipment must not disturbradio and telecommunication as well as other appliances Additionally the ECCD also governs the immunity of such equipmentto interference and seeks to ensure that this equipment is not disturbed by radio emissions when used as intended Many types ofabsorbing materials are commercially available However many are expensive and not environmentally friendly It is in the lightof the above that we studied the electromagnetic absorption properties of ZnO-PCL nanocomposites prepared from cheap andabundant resources which are environmentally friendly (zinc and polycaprolactone) The test was carried out using a microstripopen ended coaxial probe and vector network analyzer Amongst other findings result showed that the ZnO-PCL nanocompositehas the capability of attenuating microwave frequency up to minus182 dB due to their very high specific surface areas attributed to thenanofillers at 12GHz

1 Introduction

The organic-inorganic hybrid materials possess interestingfunctions through the amalgamation of the important prop-erties from both components [1ndash3] Nanocomposites basedon oxide-polymermixtures have been an active area of recentresearch owing to their range of applications in microwaveabsorption and electromagnetic interference shielding (EMI)[4]

Nanocomposites are a special class of materials havingunique properties and wide application potential in diverseareas [5] The term nanocomposites can be obtained bysuccessfully joining together two different materials in asinglematrixThe addition ofmaterial in the nanometer scalewill in no small measure change the properties of the hostpolymer matrices It is reported that to enhance the apparentdielectric constant of polymer nanodielectrics a significantamount (gt30 vol) of spherical nanoparticles needs to beincorporated into the polymer matrix [6]

Oxide-polymer nanocomposites possess unique physicaland chemical properties compared to their bulk counter partsdue to their nanodimension In comparison to traditionalcomposites nanocomposites are certainly advantageous inhomogeneous structure no fibre rupture optical trans-parency and improved or unchanged processability [7]

Some of themain factors which determine the absorptionproperties of the composites are the quality of the dispersiondielectric properties and the filler matrix interaction Pro-cessing methods suitable for nanocomposites as well as theirapplications have been developed by in situ reactive blendingmelt-mixing thermokinetic mixing extrusion blowing andinjection [7 8] Materials such as polyethylene polypropy-lene and polyethylene terephthalate epoxy polyamide andpolyimide have been used in nanocomposites as polymersSome of the fillers used in pioneering researches involvingpolymer oxides nanocomposites include Al

2O3 TiO2 and

SiO2 The major drawback faced with the earlier researches

was the cost of raw materials used ZnO as one of the

Hindawi Publishing CorporationAdvances in Materials Science and EngineeringVolume 2015 Article ID 132509 7 pageshttpdxdoiorg1011552015132509

2 Advances in Materials Science and Engineering

multifunctional inorganic particles has drawn increasingattention in recent years due to its many significant physi-cal and chemical stabilities high catalytic activity effectiveantibacterial and bactericide function and intensive ultra-violet and infrared absorption [9 10] For these reasons itis selected to serve as filler in its nanoform in the polymercomposites On the basis of the above description this paperwill investigate the use of ZnO nanoparticles as filler inthe oxide-polymer composites processing methods experi-mental work and results and discussion on electromagneticproperties as it affects radiation attenuation

2 Processing Method

For the preparation of the nanocomposites used in thisstudy the following were used zinc oxide (ZnO) 999purity with density of 5606 gcm3 (Sigma Aldrich)ethylenediaminetetraacetic acid (EDTA) 998 purity withdensity of 860mgmL (Sigma Aldrich) polycaprolactone(PCL) (C

6H10O2) 970 purity with density of 1146 gcm3

(Sigma Aldrich) deionized water (DIW) (H2O) with density

10 gcm3 and polyvinyl alcohol (PVA) 8689 purity (AlfaAesar) In our work the ZnO-PCL nanocomposites wereprepared via the melt blend technique using the ThermoHaake extruder polydrive three-phase motor with a drive of15 kW 3times 230V and 40A and speed range of 0ndash120 rpmThemelt blend method is characterized by the fact that organic-inorganic materials are made at relatively low temperatures(80∘C) and in principle consists of mixing of constituentmaterials and subsequent polycondensation to jelly-like formbefore hardening after cooling It allows incorporation oforganic and inorganic additives which is rather physical thanchemical at low temperature Mix blending is started frommelting of the polymer in aThermoHaake blendingmachineat 80∘C After melting in the machine for about 10 minutesrequired amount of nanofiller is introduced into the chamberwhere the polymer is kept The process is allowed to rotate inthe machine for 20 minutes before it is taken out and fabri-cated to required dimension using the hot or cold mouldingmethod The process is repeated for different percentages ofthe nanofiller and polymerThemelt blendmethod is suitablefor mass production However it is not the key technologyfor composites preparationThe biggest advantage of themeltblend technique is that it is very easy to use The picture ofprepared ZnO-PCL nanocomposites pellets after undergoingthe melt blend process is shown in Figure 1

The absorption properties and chemical bonding of thecomposites were verified using Fourier transform infraredspectrophotometer (FTIR) Perkin 69 Elmer in the range of380 to 4000 cmminus1 The ZnO nanoparticles prepared wereanalyzed using the Hitachi 7100 TEM (Tokyo Japan) at 75 kVFor microwave properties measurement Agilent 85070Bdielectric probe kit a sensor probe a mounting bracket acable a 35 inch high density shorting block for calibrationadapters and a software for data collection and plotting wereused The network vector analyzer model used was AgilentPNA-L N5230AThe calibration for the complex permittivitymeasurement was performed using the through-reflect-linecalibration module

Figure 1 Prepared pellets of ZnO-PCL nanocomposites

3 Measurement Technique

The material properties were studied in X-band (8ndash12GHz)regions of the microwave frequency spectra The dimensionof the microstrip used is 60 times 36 cmwith thickness of 8mmThe sample dimensions were fabricated carefully to matchthe microstrip dimensions A vector network analyzer basedmicrostripmeasurement techniquewas employed tomeasure119878-parameters of the two-port network formed by placing thesample on top of themicrostrip whilst the open ended coaxialprobe was used to measure the dielectric properties of thesamples under study 119878-parameters measured by the vectornetwork analyzer were used to calculate the absorption andattenuation of the sample The accuracy of the constitutivematerial properties depends on the accuracy with which119878-parameters are measured The through-reflect-line (TRL)calibration method was used to eliminate the systematicerrors occurring in the measurement since the experimentalsetup involves several components such as cables and con-nectors Thus proper care has to be taken to ensure that theentire system remains stable over the measurement periodreducing reflection losses to be less than dB This techniquehas been successfully applied to measure common thin filmmaterials and ferrite powders [11 12] The measurementtheory calibration and data evaluation method used in ourexperimental setup does not require initial guess parameterswhich reduces the error arising due to phase ambiguity

4 Result on Electromagnetic Properties

The sample was measured by transmission-reflection waveg-uide technique in X-band from 8 to 12GHz after usingthrough-reflect-line calibration The spectra for measuredvalue of scattering parameters are shown in Figure 2 Thesevalues were used to calculate the attenuation of the ZnO-PCL nanocomposites It is expected that at higher frequencythere is high attenuation of electromagnetic waves whichpropagates through sample thereby leading to diminishedtransmitted waves More so based on the impedance mis-match theory the higher the dielectric properties the lower|119878

21|magnitude [13] In addition if the materials have higher

loss factor then they tend to absorb more energy of theelectromagnetic waves that were propagating through the

Advances in Materials Science and Engineering 3

0

01

02

03

04

05

06

8 9 10 11 12Frequency (GHz)

253545

5070

|S21|

(a)

253545

5070

0

02

04

06

08


|S11|

(b)

Figure 2 Variation in 119878-parameter using microstrip at X-band

8 9 10 11 12

Atte

nuat

ion

(dB)

Frequency (GHz)

253545

5070

minus20

minus18

minus16

minus14

minus12

minus10

minus8

minus6

minus4

Figure 3 Attenuation for different ZnO-PCL nanocomposites

sample resulting in a diminished 11987821magnitude [13] Figure 2

depicts the theory as reported by Pozar [13]119878

21magnitude behaviour for the composites can be

further confirmed by the analysis undertaken using the FTIRspectral analysis (Figure 8) which showed that the highestabsorption (attenuation)was for the highest percentage ZnO-PCL nanocomposites (70 ZnO nanofiller) Higher concen-tration of filler is reported to result in formation of fillermultilayer inside the polymer that reduces the intensity oflight passing through polymer films as is evident in Figure 2Besides multilayer effect it was also suggested that theinterparticle distance of nanofiller decreases as the amountof nanofiller in polymer nanocomposites increases [14] TheX-band spectra for attenuation were calculated using theformula [13]

Attenuation = 20 log (11987821) (1)

1

2

3

4

5

6

7

8 9 10 11 12

Die

l co

nsta

nt

Frequency (GHz)

25354550

70ZnOPCL

Figure 4 Variation in dielectric constant of samples

The calculated attenuation of the ZnO-PCL nanocompositesis shown in Figure 3

An attenuator is a radio frequency (RF) device specificallydesigned to reduce the power of a signal without affectingor reducing the waveform of the signal and for impedancematching due to its absorptive and dissipative nature Inelectronic devices standard attenuation values can be rangedfrom minus0 to minus60 dB maximum attenuation with frequencymaximums that range from 1GHz to 50GHz dependingon attenuators type [15] Observation on Figure 3 showedthat attenuation from the different composites ranges fromminus6 to minus182 dB There was a clear indication of a sharpincrease in attenuation as filler content increased to above50 This increase is associated with the reduced particlesizes which results in an increase in the zinc oxide specificsurface area thus providing good interaction between thecrosslinking agent particles and the polymer chains therebyincreasing attenuation as the ZnO nanofiller increases [16]


25354550

70ZnOPCL

0

04

08

12

16

8 85 9 95 10 105 11 115 12

Loss

fact

or

Frequency (GHz)

Figure 5 Variation in loss factor of samples

Table 1 Real and imaginary parts of permittivity for all samples at8ndash12GHz

Sample Dielectric const Loss factor 120576119903= 120576

1015840minus 119895120576

10158401015840

Pure PCL 279 024 279 minus 119895024

ZnO nano 648 141 648 minus 119895141

ZnO-PCL-25ZnO 295 027 295 minus 119895027

ZnO-PCL-35ZnO 315 039 315 minus 119895039

ZnO-PCL-45ZnO 334 046 334 minus 119895046

ZnO-PCL-50ZnO 354 050 354 minus 119895050

ZnO-PCL-70ZnO 399 063 399 minus 119895063

The measured attenuation values fall within the range oflow power attenuators in microwave devices However thecomposite percentage can be tailored to provide attenuationabove minus20 dB which is mostly used in microwave devicesHigher attenuation of the composite can be achieved byincreasing the percentage of the filler in the composites lead-ing to increased level of RF attenuation and low magnitudeof RF leakage It is important to note that attenuation canvary greatly depending on the frequency of operation Inconclusion depending on the application the composites canbe tailored to suit the application for which it is intended

It is reported that materials with higher permittivityvalues tend to possess higher attenuation at higher frequencyranges To understand the phenomena the dielectric prop-erties of the composites were measured The real permit-tivity of the ZnO nanoparticles pure PCL and ZnO-PCLnanocomposite showing decrease in dielectric constant asfrequency increases is presented in Figure 4 This decreasein magnitude may be attributed to the real permittivitydispersionwhich is an interfacial polarizationThis interfacialpolarization can occur since the two materials have differentpermittivity and conductivity hence when electrical field isapplied to the composite space charges provided by the Zn2+phase accumulate at the interface of the two materials Thisbehavior is not usually intrinsic but is rather associated withthe heterogeneous conduction in the multiphase structure ofthe composite [17]

The increase in dielectric magnitude of the ZnO-PCLnanocomposites is also due to the number of Zn2+ added tothe polymer matrix The increase in the number of chargedions within the composite has contributed to the increase inthe real permittivity of the ZnO-PCL nanocomposites whilstthe loss factor shown in Figure 5 depicts the loss in energy ofthe propagatedwaves through the samplesThe result showedthat the 70 ZnO-PCL nanocomposites had the lowest losswhich is in good agreement with the result obtained for thescattering parameters and FTIR analysis In addition thedielectric measurement result confirms the integration of theparticle into the polymer matrix

The higher percentage of nanofiller used in this workwas done so as to produce composites whose dielectricconstant would be close to the value of ZnOnanoparticleTheobjective of higher filler content in the polymer matrix is toboost the complex permittivity value of the nanocompositeswhich in turn leads to higher attenuation as reported by Pozarin [13] The use of higher percentage of ZnO nanofiller inthe composites is also supported by the work carried by [6]The effect of using higher value of filler is clearly expressed inTable 1 Careful observation on Table 1 showed that 70 ZnOnanofiller has successfully enhanced the dielectric constant ofthe composites which is about 612 the value of the dielectricconstant of the ZnO nanoparticles

For the magnetic permeability shown in Figure 6 it wasobserved that the difference from one weight percent to otherwas very small The value of permeability from the lowestto highest ZnO nanofiller is 1034 to 1 041 However thepermeability values are higher than unity because 8GHz liesin the low frequency tail of the broad magnetic resonanceabsorption band appearing at lower microwave frequenciesThe higher the percentage of the ZnO nanofiller the higherthe values of the permeability 1205831015840 The infinitesimal changein the real part of permeability for all the composites mightbe attributed to the homogeneous nature of the compositesattributed to good sample preparation technique [18]

However the imaginary part of permeability shownin Figure 7 exhibits a significant change in magnitude forthe different () ZnO-PCL nanocomposites as frequencyincreases The result showed a general increase of about 25times from 10GHz to 12GHz which is attributed to theincrease in the ZnO nanofiller content

All the analyses undertaken were further supported usinga tool called the FTIR The FTIR is used to confirm thebonding interaction andmost of all the absorbing propertiesof the compositesThe principal peaks from FTIR analysis forthe ZnO-PCL nanocomposite after nanoinclusion shown inFigure 8 are the 280 cmminus1 peak due to the Zn-O-Zn stretchingvibrations the 730 cmminus1 peak due to long chain rockingvibrations the 1200 cmminus1 peak due to C-O-C aliphatic etherstretching vibrations the 1726 cmminus1 peak due to the C-Ostretching vibrations the 2941 cmminus1 peak due to CH

2stretch-

ing vibrations and additional new peak at 3470 cmminus1 Thenew isolated band peak exhibited by the ZnO-PCL nanocom-posites at 3470 cmminus1 may be attributed to O-H species in thecomposites [19 20]The lattice vibration bands between 3470and 3420 cmminus1 3070 and 2720 cmminus1 and 455 and 755 cmminus1 of


0900

1000

1100

1200

8 85 9 95 10 105 11 115 12

Real

per

mea

bilit

y

Frequency (GHz)

253545

5070ZnO

(a)

1032

1037

1042

1047

95 10 105

Real

per

mea

bilit

y

Frequency (GHz)

253545

5070ZnO

(b)

Figure 6 Variation in real permeability of ZnO-PCL nanocomposites

8 9 10 11 12

Imag

per

mea

bilit

y

Frequency (GHz)

354550

70ZnO

minus01

minus006

minus002

002

006

01

Figure 7 Variation in imaginary permeability of ZnO-PCL nanocomposites

Tran

smitt

ance

()

ZnO2535

4550Pure PCL

Wave number (cmminus1)

100

90

80

70

60

50

40

30

20

10

04200 3700 3200 2700 2200 1700 1200 700 200

(a)

Tran

smitt

ance

()

ZnO2535

4550Pure PCL


100

95

90

85

80

75

70

65

60

553050 3000 2950 2900 2850 2800 2750

(b)

Figure 8 FTIR spectrum for different () of ZnO-PCL nanocomposites ZnO and PCL


the pure PCLwhen compared to the ZnOnanoparticles fillersshowed an increase in absorption peaks for all weight percentthus providing evidence that the ZnO layers have been dopedinto the PCL matrix by the melt blending process therebyforming the ZnO-PCL nanocomposites as clearly shown inFigure 8(b) The increase in ZnO nanofiller increases theabsorption peaks of the composites as is evident in [21]

TEM analysis was carried out so as to gain knowledge onthe particle size distribution of the prepared ZnO particlesThe analysis showed spherical particle size distribution ofZnO nanoparticles that was dispersed in the polymer Theaverage particles size was calculated to be 415 nm

5 Error Analysis

Experimental uncertainties (random errors) were minimizedby repeating each measurement six times for each sampleSome other components identified that can cause randomerrors in measurement are the connectors between thenetwork analyzer andmicrostrip which canmake the systemsensitive to noise and driftThese errors can be minimized bykeeping the whole system clean and stable whilst systematicerrors caused by the imperfections of the systemwere reducedby careful calibration of the whole measurement systembefore the actual measurements were undertaken

6 Conclusion

The microstrip based transmission-reflection measurementtechnique has been successfully applied to calculate the atten-uation of ZnO-PCL nanocomposites in the wide frequencyrange of 8ndash12GHz for the first timeThe results obtained showstability in the values of the measured parameters The meltblend ZnO-PCL nanocomposites show great applicabilityin microwave attenuation The substrates were fabricated atlow temperature with easy preparation steps unlike othertechniques It was found that frequency is proportionalto the magnetization despite the use of semiconductingnanocomposites material These relationships correspond toSnoekrsquos limitation rule From these results it was clarified thatZnO-PCL nanocomposites having magnetization larger thatSnoekrsquos limit are suitable for high-microwave devices absorb-ing applications The knowledge of the material properties isnecessary to understand the potential use of these materialsin high frequency applicationsThese substrates will be usefulformanymicrowave applications such as antennas inductorsfilters and absorbers

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The authors wish to thank the Universiti Putra Malaysia(UPM) for its support and for the provision of enablingenvironment to carry out this work

References

[1] L Cumbal J Greenleaf D Leun andA K SenGupta ldquoPolymersupported inorganic nanoparticles characterization and envi-ronmental applicationsrdquo Reactive and Functional Polymers vol54 no 1ndash3 pp 167ndash180 2003

[2] Y D Zhang S H Wang D T Xiao J I Budnick and W AHines ldquoNanocomposite CoSiO

2softmagneticmaterialsrdquo IEEE

Transactions on Magnetics vol 37 no 4 pp 2275ndash2277 2001[3] S Sindhu S Jegadesan A Parthiban and S Valiyaveettil ldquoSyn-

thesis and characterization of ferrite nanocomposite spheresfrom hydroxylated polymersrdquo Journal of Magnetism and Mag-netic Materials vol 296 no 2 pp 104ndash113 2006

[4] M Matsumoto and Y Miyata ldquoPolymer absorbers containingmagnetic particles effect of polymer permittivity on waveabsorption in the quasi-microwave bandrdquo Journal of AppliedPhysics vol 91 no 12 pp 9635ndash9637 2002

[5] R Dai G Wu W Li Q Zhou X Li and H Chen ldquoGela-tincarboxymethylcellulosedioctyl sulfosuccinate sodium mi-crocapsule by complex coacervation and its application for elec-trophoretic displayrdquo Colloids and Surfaces A Physicochemicaland Engineering Aspects vol 362 no 1ndash3 pp 84ndash89 2010

[6] JWang F Guan L Cui J Pan QWang and L Zhu ldquoAchievinghigh electric energy storage in a polymer nanocomposite atlow filling ratios using a highly polarizable phthalocyanineinterphaserdquo Journal of Polymer Science B Polymer Physics vol52 no 24 pp 1669ndash1680 2014

[7] T Tanaka G C Montanari and R Mulhaupt ldquoPolymer nano-composites as dielectrics and electrical insulation-perspectivesfor processing technologies material characterization andfuture applicationsrdquo IEEE Transactions on Dielectrics and Elec-trical Insulation vol 11 no 5 pp 763ndash784 2004

[8] R Kochetov Thermal and electrical properties of nanocompos-ites including material processing [PhD thesis] LappeenrantaUniversity of Technology Lappeenranta Finland 2012

[9] Y Yang H Chen B Zhao and X Bao ldquoSize control of ZnOnanoparticles via thermal decomposition of zinc acetate coatedon organic additivesrdquo Journal of Crystal Growth vol 263 no1ndash4 pp 447ndash453 2004

[10] R Wu and C Xie ldquoFormation of tetrapod ZnO nanowhiskersand its optical propertiesrdquo Materials Research Bulletin vol 39no 4-5 pp 637ndash645 2004

[11] A Sharma and M N Afsar ldquoAccurate permittivity and per-meability measurement of composite broadband absorbers atmicrowave frequenciesrdquo in Proceedings of the IEEE Interna-tional Instrumentation andMeasurement Technology Conference(I2MTC rsquo11) pp 1ndash6 IEEE May 2011

[12] A Sharma and M N Afsar ldquoMicrowave complex permeabil-ity and permittivity measurements of commercially availablenano-ferritesrdquo IEEE Transactions on Magnetics vol 47 no 2pp 308ndash312 2011

[13] D M Pozar Microwave Engineering John Wiley amp Sons 3rdedition 2009

[14] M A A Rahman S Mahmud A Karim Alias and A F MNor ldquoEffect of nanorod zinc oxide on electrical and optical pro-perties of starch-based polymer nanocompositesrdquo Journal ofPhysical Science vol 24 no 1 pp 17ndash28 2013

[15] X Liu X Yin L Kong et al ldquoFabrication and electromagneticinterference shielding effectiveness of carbon nanotube rein-forced carbon fiberpyrolytic carbon compositesrdquo Carbon vol68 pp 501ndash510 2014


[16] M Przybyszewska and M Zaborski ldquoThe effect of zinc oxidenanoparticle morphology on activity in crosslinking of car-boxylated nitrile elastomerrdquo eXPRESSPolymer Letters vol 3 no9 pp 542ndash552 2009

[17] BW Li Y Shen Z X Yue andCWNan ldquoInfluence of particlesize on electromagnetic behavior and microwave absorptionproperties of Z-type Ba-ferritepolymer compositesrdquo Journal ofMagnetism and Magnetic Materials vol 313 no 2 pp 322ndash3282007

[18] S Seema and M V N A Prasad ldquoDielectric spectroscopy ofnanostructured polypyrrole-NiO compositesrdquo Journal of Poly-mers vol 2014 Article ID 950304 5 pages 2014

[19] P Mitra and S Mondal ldquoStructural and morphological charac-terization of ZnO thin films synthesized by SILARrdquo Progress inTheoretical and Applied Physics vol 1 pp 17ndash31 2013

[20] A Pakdel and F E Ghodsi ldquoInfluence of drying conditionson the optical and structural properties of sol-gel-derived ZnOnanocrystalline filmsrdquo PramanamdashJournal of Physics vol 76 no6 pp 973ndash983 2011

[21] H Peng Y Han T LiuW C Tjiu and C He ldquoMorphology andthermal degradation behavior of highly exfoliatedCoAl-layereddouble hydroxidepolycaprolactone nanocomposites preparedby simple solution intercalationrdquoThermochimica Acta vol 502no 1-2 pp 1ndash7 2010

Submit your manuscripts athttpwwwhindawicom

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Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


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MaterialsJournal of


Nano

materials


Journal ofNanomaterials


multifunctional inorganic particles has drawn increasingattention in recent years due to its many significant physi-cal and chemical stabilities high catalytic activity effectiveantibacterial and bactericide function and intensive ultra-violet and infrared absorption [9 10] For these reasons itis selected to serve as filler in its nanoform in the polymercomposites On the basis of the above description this paperwill investigate the use of ZnO nanoparticles as filler inthe oxide-polymer composites processing methods experi-mental work and results and discussion on electromagneticproperties as it affects radiation attenuation

2 Processing Method

For the preparation of the nanocomposites used in thisstudy the following were used zinc oxide (ZnO) 999purity with density of 5606 gcm3 (Sigma Aldrich)ethylenediaminetetraacetic acid (EDTA) 998 purity withdensity of 860mgmL (Sigma Aldrich) polycaprolactone(PCL) (C

6H10O2) 970 purity with density of 1146 gcm3

(Sigma Aldrich) deionized water (DIW) (H2O) with density

10 gcm3 and polyvinyl alcohol (PVA) 8689 purity (AlfaAesar) In our work the ZnO-PCL nanocomposites wereprepared via the melt blend technique using the ThermoHaake extruder polydrive three-phase motor with a drive of15 kW 3times 230V and 40A and speed range of 0ndash120 rpmThemelt blend method is characterized by the fact that organic-inorganic materials are made at relatively low temperatures(80∘C) and in principle consists of mixing of constituentmaterials and subsequent polycondensation to jelly-like formbefore hardening after cooling It allows incorporation oforganic and inorganic additives which is rather physical thanchemical at low temperature Mix blending is started frommelting of the polymer in aThermoHaake blendingmachineat 80∘C After melting in the machine for about 10 minutesrequired amount of nanofiller is introduced into the chamberwhere the polymer is kept The process is allowed to rotate inthe machine for 20 minutes before it is taken out and fabri-cated to required dimension using the hot or cold mouldingmethod The process is repeated for different percentages ofthe nanofiller and polymerThemelt blendmethod is suitablefor mass production However it is not the key technologyfor composites preparationThe biggest advantage of themeltblend technique is that it is very easy to use The picture ofprepared ZnO-PCL nanocomposites pellets after undergoingthe melt blend process is shown in Figure 1

The absorption properties and chemical bonding of thecomposites were verified using Fourier transform infraredspectrophotometer (FTIR) Perkin 69 Elmer in the range of380 to 4000 cmminus1 The ZnO nanoparticles prepared wereanalyzed using the Hitachi 7100 TEM (Tokyo Japan) at 75 kVFor microwave properties measurement Agilent 85070Bdielectric probe kit a sensor probe a mounting bracket acable a 35 inch high density shorting block for calibrationadapters and a software for data collection and plotting wereused The network vector analyzer model used was AgilentPNA-L N5230AThe calibration for the complex permittivitymeasurement was performed using the through-reflect-linecalibration module

Figure 1 Prepared pellets of ZnO-PCL nanocomposites

3 Measurement Technique

The material properties were studied in X-band (8ndash12GHz)regions of the microwave frequency spectra The dimensionof the microstrip used is 60 times 36 cmwith thickness of 8mmThe sample dimensions were fabricated carefully to matchthe microstrip dimensions A vector network analyzer basedmicrostripmeasurement techniquewas employed tomeasure119878-parameters of the two-port network formed by placing thesample on top of themicrostrip whilst the open ended coaxialprobe was used to measure the dielectric properties of thesamples under study 119878-parameters measured by the vectornetwork analyzer were used to calculate the absorption andattenuation of the sample The accuracy of the constitutivematerial properties depends on the accuracy with which119878-parameters are measured The through-reflect-line (TRL)calibration method was used to eliminate the systematicerrors occurring in the measurement since the experimentalsetup involves several components such as cables and con-nectors Thus proper care has to be taken to ensure that theentire system remains stable over the measurement periodreducing reflection losses to be less than dB This techniquehas been successfully applied to measure common thin filmmaterials and ferrite powders [11 12] The measurementtheory calibration and data evaluation method used in ourexperimental setup does not require initial guess parameterswhich reduces the error arising due to phase ambiguity

4 Result on Electromagnetic Properties

The sample was measured by transmission-reflection waveg-uide technique in X-band from 8 to 12GHz after usingthrough-reflect-line calibration The spectra for measuredvalue of scattering parameters are shown in Figure 2 Thesevalues were used to calculate the attenuation of the ZnO-PCL nanocomposites It is expected that at higher frequencythere is high attenuation of electromagnetic waves whichpropagates through sample thereby leading to diminishedtransmitted waves More so based on the impedance mis-match theory the higher the dielectric properties the lower|119878

21|magnitude [13] In addition if the materials have higher

loss factor then they tend to absorb more energy of theelectromagnetic waves that were propagating through the


0

01

02

03

04

05

06


253545

5070

|S21|

(a)

253545

5070

0

02

04

06

08


|S11|

(b)


8 9 10 11 12

Atte

nuat

ion

(dB)

Frequency (GHz)

253545

5070

minus20

minus18

minus16

minus14

minus12

minus10

minus8

minus6

minus4







1

2

3

4

5

6

7

8 9 10 11 12

Die

l co

nsta

nt

Frequency (GHz)

25354550

70ZnOPCL





25354550

70ZnOPCL

0

04

08

12

16

8 85 9 95 10 105 11 115 12

Loss

fact

or

Frequency (GHz)




1015840minus 119895120576

10158401015840

Pure PCL 279 024 279 minus 119895024

ZnO nano 648 141 648 minus 119895141

ZnO-PCL-25ZnO 295 027 295 minus 119895027

ZnO-PCL-35ZnO 315 039 315 minus 119895039

ZnO-PCL-45ZnO 334 046 334 minus 119895046

ZnO-PCL-50ZnO 354 050 354 minus 119895050

ZnO-PCL-70ZnO 399 063 399 minus 119895063








2stretch-



0900

1000

1100

1200

8 85 9 95 10 105 11 115 12

Real

per

mea

bilit

y

Frequency (GHz)

253545

5070ZnO

(a)

1032

1037

1042

1047

95 10 105

Real

per

mea

bilit

y

Frequency (GHz)

253545

5070ZnO

(b)


8 9 10 11 12

Imag

per

mea

bilit

y

Frequency (GHz)

354550

70ZnO

minus01

minus006

minus002

002

006

01


Tran

smitt

ance

()

ZnO2535

4550Pure PCL


100

90

80

70

60

50

40

30

20

10

04200 3700 3200 2700 2200 1700 1200 700 200

(a)

Tran

smitt

ance

()

ZnO2535

4550Pure PCL


100

95

90

85

80

75

70

65

60

553050 3000 2950 2900 2850 2800 2750

(b)





5 Error Analysis


6 Conclusion




Acknowledgment


References
































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0

01

02

03

04

05

06


253545

5070

|S21|

(a)

253545

5070

0

02

04

06

08


|S11|

(b)


8 9 10 11 12

Atte

nuat

ion

(dB)

Frequency (GHz)

253545

5070

minus20

minus18

minus16

minus14

minus12

minus10

minus8

minus6

minus4







1

2

3

4

5

6

7

8 9 10 11 12

Die

l co

nsta

nt

Frequency (GHz)

25354550

70ZnOPCL





25354550

70ZnOPCL

0

04

08

12

16

8 85 9 95 10 105 11 115 12

Loss

fact

or

Frequency (GHz)




1015840minus 119895120576

10158401015840

Pure PCL 279 024 279 minus 119895024

ZnO nano 648 141 648 minus 119895141

ZnO-PCL-25ZnO 295 027 295 minus 119895027

ZnO-PCL-35ZnO 315 039 315 minus 119895039

ZnO-PCL-45ZnO 334 046 334 minus 119895046

ZnO-PCL-50ZnO 354 050 354 minus 119895050

ZnO-PCL-70ZnO 399 063 399 minus 119895063








2stretch-



0900

1000

1100

1200

8 85 9 95 10 105 11 115 12

Real

per

mea

bilit

y

Frequency (GHz)

253545

5070ZnO

(a)

1032

1037

1042

1047

95 10 105

Real

per

mea

bilit

y

Frequency (GHz)

253545

5070ZnO

(b)


8 9 10 11 12

Imag

per

mea

bilit

y

Frequency (GHz)

354550

70ZnO

minus01

minus006

minus002

002

006

01


Tran

smitt

ance

()

ZnO2535

4550Pure PCL


100

90

80

70

60

50

40

30

20

10

04200 3700 3200 2700 2200 1700 1200 700 200

(a)

Tran

smitt

ance

()

ZnO2535

4550Pure PCL


100

95

90

85

80

75

70

65

60

553050 3000 2950 2900 2850 2800 2750

(b)





5 Error Analysis


6 Conclusion




Acknowledgment


References
































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




25354550

70ZnOPCL

0

04

08

12

16

8 85 9 95 10 105 11 115 12

Loss

fact

or

Frequency (GHz)




1015840minus 119895120576

10158401015840

Pure PCL 279 024 279 minus 119895024

ZnO nano 648 141 648 minus 119895141

ZnO-PCL-25ZnO 295 027 295 minus 119895027

ZnO-PCL-35ZnO 315 039 315 minus 119895039

ZnO-PCL-45ZnO 334 046 334 minus 119895046

ZnO-PCL-50ZnO 354 050 354 minus 119895050

ZnO-PCL-70ZnO 399 063 399 minus 119895063








2stretch-



0900

1000

1100

1200

8 85 9 95 10 105 11 115 12

Real

per

mea

bilit

y

Frequency (GHz)

253545

5070ZnO

(a)

1032

1037

1042

1047

95 10 105

Real

per

mea

bilit

y

Frequency (GHz)

253545

5070ZnO

(b)


8 9 10 11 12

Imag

per

mea

bilit

y

Frequency (GHz)

354550

70ZnO

minus01

minus006

minus002

002

006

01


Tran

smitt

ance

()

ZnO2535

4550Pure PCL


100

90

80

70

60

50

40

30

20

10

04200 3700 3200 2700 2200 1700 1200 700 200

(a)

Tran

smitt

ance

()

ZnO2535

4550Pure PCL


100

95

90

85

80

75

70

65

60

553050 3000 2950 2900 2850 2800 2750

(b)





5 Error Analysis


6 Conclusion




Acknowledgment


References
































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0900

1000

1100

1200

8 85 9 95 10 105 11 115 12

Real

per

mea

bilit

y

Frequency (GHz)

253545

5070ZnO

(a)

1032

1037

1042

1047

95 10 105

Real

per

mea

bilit

y

Frequency (GHz)

253545

5070ZnO

(b)


8 9 10 11 12

Imag

per

mea

bilit

y

Frequency (GHz)

354550

70ZnO

minus01

minus006

minus002

002

006

01


Tran

smitt

ance

()

ZnO2535

4550Pure PCL


100

90

80

70

60

50

40

30

20

10

04200 3700 3200 2700 2200 1700 1200 700 200

(a)

Tran

smitt

ance

()

ZnO2535

4550Pure PCL


100

95

90

85

80

75

70

65

60

553050 3000 2950 2900 2850 2800 2750

(b)





5 Error Analysis


6 Conclusion




Acknowledgment


References
































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






5 Error Analysis


6 Conclusion




Acknowledgment


References
































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials

















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



research article reduction of electromagnetic interference...

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