research article synthesis of nickel and nickel hydroxide

Research ArticleSynthesis of Nickel and Nickel Hydroxide Nanopowders bySimplified Chemical Reduction

Jeerapan Tientong Stephanie Garcia Casey R Thurber and Teresa D Golden

Department of Chemistry University of North Texas 1155 Union Circle No 305070 Denton TX 76203 USA

Correspondence should be addressed to Teresa D Golden tgoldenuntedu

Received 31 July 2013 Revised 3 December 2013 Accepted 4 December 2013 Published 5 February 2014

Academic Editor ThomasThundat

Copyright copy 2014 Jeerapan Tientong 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

Nickel nanopowders were synthesized by a chemical reduction of nickel ions with hydrazine hydrate at pH sim125 Sonicationof the solutions created a temperature of 54ndash65∘C to activate the reduction reaction of nickel nanoparticles The solution pHaffected the composition of the resulting nanoparticles Nickel hydroxide nanoparticles were formed from an alkaline solution(pHsim10) of nickel-hydrazine complexed by dropwise titration X-ray diffraction of the powder and the analysis of the resultingWilliamson-Hall plots revealed that the particle size of the powders ranged from 12 to 14 nm Addition of polyvinylpyrrolidoneinto the synthesis decreased the nickel nanoparticle size to approximately 7 nm Dynamic light scattering and scanning electronmicroscopy confirmed that the particles were in the nanometer rangeThe structure of the synthesized nickel and nickel hydroxidenanoparticles was identified by X-ray diffraction and Fourier transform infrared spectroscopy

1 Introduction

Synthesis of metal nanoparticles or nanoclusters in powdershas attracted increasing attention in recent years due totheir novel electronic optical andmagnetic propertiesThesemetal nanoparticles have various uses in catalysts paintspigments and sensors applications [1ndash4] Generally metalnanopowders are synthesized by the reduction of metal ionsin aqueous or organic solution by a chemical reagent orelectrochemical current [5] Many other methods have beendevised to synthesize these powders including a hydrother-mal reduction method [6 7] microemulsion synthesis [8]chemical reduction at acidic pH [9] and electrochemicalreduction with a rotating cathode [10] Much focus hasbeen on methods that allow control of the particle sizeas there is evidence that particle size directly affects theproperties of the powder [11 12] Other considerations forresearchers include the prevention of agglomeration andoxidization of the particles [13] and quantity synthesis with afocus on industrialization of the process [14] Stabilizers suchas polyvinylpyrrolidone (PVP) are often used for particleprotection and are able to decrease particle size [15 16]

For nickel nanoparticles chemical synthesis usinghydrazine reduction has been a successful synthesis route[17ndash19] While nickel nanoparticles are advantageous forcertain uses nickel hydroxide also has many importanttechnological uses Nickel hydroxide is used for batteryphotocatalysis and fuel cell applications [20 21] Dependingon the pH and other species in the solution either nickel ornickel hydroxide particles can be formed Therefore having asimple technique for synthesis of both is advantageous

In this paper we present a simple inexpensive andefficient chemical method of synthesizing nickel and nickelhydroxide powders with nanometer-sized particles The syn-thesis uses a hydrazine reduction route taking advantage ofsonication at room temperature

2 Experimental

21 Materials All chemicals were of analytical grade andused without further purification nickel chloride (NiCl

2sdot

6H2O) from Fisher Scientific 98 hydrazine hydrate (N

2H4sdot

H2O) fromAldrich and sodiumhydroxide (NaOH) fromEM

Science All solutions were prepared with DI water

Hindawi Publishing CorporationJournal of NanotechnologyVolume 2014 Article ID 193162 6 pageshttpdxdoiorg1011552014193162

2 Journal of Nanotechnology

22 Synthesis of Nickel Nanopowder Thenickel nanopowderswere synthesized by reduction of nickel in an aqueoussolution with hydrazine hydrate acting as the reductantFor solution A 05 g of nickel chloride (NiCl

2sdot 6H2O) was

dissolved in 60mL of distilled water In a separate beakersolution B was prepared by dissolving 10 g of NaOH in20mLDI water and then adding 20mL of hydrazine hydrateSolution B was then added to solution A the combinedsolution turned into a royal blue color and was mixed witha stirring rod for 2 minutes resulting in a pH sim125 solutionFor the synthesis of nickel powder stabilized by PVP solutionB was prepared by dissolving 02 g of PVP in 3mL of absoluteethanol and then slowly introduced into the NaOH solutionthen hydrazine was added and the solution was stirred

According to Chen and Zhou the reaction temperatureneeds to stay below 70∘C in order to prepare ultrafine nickelparticles [22] The solution was sonicated for 15 minutesto sim55∘C allowed to sit for 15 minutes in order to controlthe temperature and then sonicated again for 15 minutes tosim65∘C to activate the precipitation of the nickel particlesDuring the activation period the solution initially becamegrey and coated along the side and bottom of the beaker andthen precipitated out to the bottom as a black powder Thenickel powder solution was centrifuged and washed with DIwater and absolute ethanol and was allowed to dry at roomtemperature

23 Synthesis of Nickel Hydroxide Nanopowder Solution Awas prepared in a 250mL volumetric flask composed of 119 gof nickel chloride dissolved in 50mL DI water then 200mLof absolute ethanol was added to the mark forming a greensolution The solution was transferred into a 500mL conicalflask Solution B was prepared in a 200mL volumetric flaskFirst 04 g of sodium hydroxide was dissolved in 100mL ofDI water 15mL of hydrazine hydrate was added and thendiluted to the mark with DI water Solution B was slowlydropped into solution A from a burette at a rate of sim02mLper minute and mixed with a magnetic stirrer The resultingsolution became cloudy green with precipitate forming assoon as the pH reached 68 and then turned to a cloudy bluegreen The mixed solution finally became a grey blue withthe addition of 80ndash90mL of solution B at a final pH of sim10The precipitated solution was centrifuged The powders werewashed with DI water and absolute ethanol and then freezedried

24 Characterization X-ray diffraction scans were run onthe synthesized nickel and nickel hydroxide powders with aSiemens D-500 diffractometer with Cu K120572 radiation (120582 =015405 nm) XRD scans were run at a step size of 005degrees and dwell time of 1 s The tube source was oper-ated at 40 kV and 30mA A Williamson-Hall analysis wasdone on each sample to calculate the particle size withsilicon powder as the standard for instrumental broadeningDynamic light scattering (DLS) (Beckman-Coulter DelsaNano-C) was used to determine the size of the nanoparticlecolloids in aqueous solution Each of the dried nanoparticlepowders was dispersed into an aqueous environment by

sonication for 30 minutes The samples were allowed toequilibrate for 60 seconds at 25∘C using a peltier device andscanned 40 times during the analysis The nanoparticles ofthe powders were characterized with a FEI Nova nanoSEM230 scanning electronmicroscope (SEM)with an ETD detec-tor Fourier transform infrared spectroscopy (FTIR) (PerkinElmer Spectrum One) spectra were obtained for each of thenanoparticle powders using the Attenuated Total Reflectance(ATR) attachment in the range of 450 to 4000 cmminus1

3 Results and Discussion

Nickel nanoparticles were synthesized from a nickel-hydrazine mixture in a sodium hydroxide environmentat high pH (sim125) which is favorable to form nickelnanoparticles [18 19] Hydrazine (N

2H4) has a standard

reduction potential of minus116 V in an alkaline solutionrepresented by the oxidation reaction (N

2H4+ 4OHminus =

N2+ 4H

2O + 4eminus) when mixed with the nickel ions

[18 23] Nickel which has a standard reduction potentialof minus025V is consequently able to be reduced by hydrazine(2Ni2+ + 4eminus = 2Ni) [18] Therefore a chemical reductionprocess of the nickel ion with hydrazine as a reductantin an alkaline aqueous solution can be simply shown inthe following equation 2Ni2+ + N

2H4+ 4OHminus rarr 2Ni +

N2+ 4H

2O Solution pH influences the synthesis of the

nickel nanoparticles as seen in the Nernst equation (1)The discharge of the nickel nanopowders was enhancedwhen the redox potential the driving force of the reactionincreased because of the increasing pH of the solutionby adding a strong base such as sodium hydroxide at acertain temperature and constant nickel ion concentration[17ndash19] In addition it has been shown that nickel powder agray-black powder cannot be produced if the pH is less than95 [19]

119864 = 119864

119900

minus

119877119879

4119865

ln 1

[OHminus]4[Ni2+]2

= 119864

1199002303

4119865

log [OHminus]4[Ni2+]2

(1)

However in order to avoid precipitation of hydroxide it iscrucial to maintain the reduction process at a high pH [18]This is because the standard reduction potential of Ni(OH)

2

is minus072V for Ni(OH)2+ 2eminus = Ni + 2OHminus

For the synthesis of Ni(OH)2nanopowder hydrazine was

slowly added dropwise into the nickel solution and graduallychanged from a clear green (initial pH of 4) to a cloudyblue green when the pH reached sim7 Hydrazine also actedas a ligand which was able to initially form a complex of[Ni(N

2H4)2]Cl2 [Ni(N

2H4)3]Cl2 or [Ni(N

2H4)6]Cl2in the

nickel solution with respect to the molar ratio of nickelto hydrazine [18] When the pH reached sim7 the complexbegan to form nickel hydroxide nanoparticles where thelocal pH around the hydrazine-sodium hydroxide dropletenvironment tended to be basic The particles were graduallycreated when the pH increased as a result of an enhancementof the reducing power of hydrazine [19] The addition of the

Journal of Nanotechnology 3

30 40 50 60 70 80 90 100 110

(222)

(311)

(220)(200)

(b) Ni-PVP

(a) Ni

Inte

nsity

(cou

nts)

(111)

2120579 (deg)

Figure 1 XRDpattern of (a) nickel and (b) nickel powders stabilizedby PVP precipitated by a chemical reductionmethod and sonicationat temperature 55ndash65∘C

hydrazine-sodium hydroxide solution was stopped at a pH of10 forming a gray blue solutionThe [Ni(N

2H4)3]Cl2complex

can exchange the chloride ion with the hydroxide ion to formnickel hydroxide nanoparticles as seen in the following [18]

[Ni(N2H4)

3

]Cl2+ 2NaOH

997888rarr Ni(OH)2+ 3N2H4+ 2NaCl

(2)

X-Ray diffraction was used to analyze the structure andparticle size of the powders Figure 1(a) shows a typical XRDpattern of the Ni powder sample after sonication filtrationand drying The five characteristic peaks for nickel 2120579 =4445 5171 7641 9296 and 9846∘ corresponding to Millerindices (111) (200) (220) (311) and (222) respectively wereobserved indicating that the resulting powders are face-centered cubic (fcc) nickel (PDF 04-0850) [24] As seenfrom the XRD plot the (111) reflection is the highest intensityfor the peaks After comparing the experimental pattern tothe JCPDS database (PDF 04-0850) the pattern matches arandom powder arrangement for nickel Figure 1(b) displaysthe result of amethodmatching the JCPDS file for nickel afteradding a particle protector PVP to the solution

The crystallite size (for particles lt 1 120583m) can be calculatedfrom the line broadening in the XRD patterns Broadeningthat occurs for X-ray diffraction peaks is mainly due to threefactors instrumental broadening crystallite size and latticestrain Broadening due to stress follows a tan 120579 functionand broadening due to crystallite size follows a 1 cos 120579dependence The Williamson-Hall method can be used todetermine (or separate) the contribution of each factor to thebroadening of the peaks in the XRD patterns when there arethree or more reflections available for measurement [25 26]Contributions of crystallite size and strain are given by thefollowing equation

120573

119903cos 120579 = 119896120582

119871

+ 120578 sin 120579 (3)

where 120582 is the wavelength of the X-rays 120579 is the diffractionangle 120578 is the strain 119871 is the crystallite size 119896 is a constant

03 04 05 06 07 08000

001

002

003

004

005

006

007

008

120573rcos120579

sin120579

Figure 2 Williamson-Hall plot for XRD data of nickel powder(squares blue line fit) and PVP-protected nickel particles (trianglesred fit lines)

(094 for Gaussian line profiles and small cubic crystals ofuniform size) and 120573

119903(in radians) is the corrected full width

at half maximum of the peak given by

120573

2

119903

= 120573

2

119898

minus 120573

2

119904

(4)

where 120573119898is the experimental measured half width and 120573

119904

is the half width of a silicon powder standard with peakscorresponding to the same 2120579 region Equation (4) is usedto correct for instrumental broadening when the observedpeaks have a near-Gaussian shape From (3) a plot of 120573

119903cos 120579

versus sin 120579 (Williamson-Hall plot) yields a straight line witha slope of 120578 and intercept of 119896120582119871 For XRD patterns whichexhibit preferred orientation (have fewer than 3 peaks) theScherrer equation can be used to estimate the crystallite size[25]

Williamson-Hall plots were used to estimate nickel pow-der particle size for the samples (Figure 2) Broader peaks intheXRDpattern (Figure 1) of the solution that contained PVPindicated a smaller particle size and the Williamson-Hallplot (Figure 2) confirmed that PVP-protected particles had anestimated size of 7 nm compared to an estimate of 12 nm fornon-PVP protected particles The particle sizes between thePVP and non-PVP solution only show a small difference invalues

The precipitates of nickel hydroxide powder were sim-ilarly analyzed A typical XRD pattern of nickel hydroxidepowder is shown in Figure 3This patternmatches the JCPDSfile for 120573-Ni(OH)

2(PDF 14-0117) [27] A Williamson-Hall

plot of the nickel hydroxide powder (Figure 4) gives anapproximate particle size of 14 nm Table 1 lists the sizes of thesynthesized powders as measured from the X-ray diffractiondata

Dynamic light scattering experiments of the colloidalsolutions before drying were run to estimate the size of theparticles in solution phase The DLS data is listed in Table 1and shows that the particle sizes in an aqueous solution are


20 40 60 80 100

210203

202201

200103

111

110

102

101

100

001

Inte

nsity

(cou

nts)

2120579 (deg)

Figure 3 XRDpattern of precipitated nickel hydroxide powder pro-duced by titrating nickel chloride with hydrazine-sodium hydroxidesolution at pH sim10

01 02 03 04 05 06 070008

0009

0010

0011

0012

0013

sin120579

120573rcos120579

Figure 4 Williamson-Hall plot for XRD data of Ni(OH)2

synthe-sized powder

Table 1 Particle size of the nanopowders measured using theWilliamson-Hall analysis from the X-ray diffraction data and thedynamic light scattering method

Nanopowders Measured particle size (nm)Williamson-Hall

plotDynamic light

scattering (119899 = 40)Nickel 12 1017 plusmn 256

Nickel-PVP 7 259 plusmn 44

Nickel hydroxide 14 631 plusmn 162

larger than the Williamson-Hall analysis of the dried pow-ders this is due to the agglomeration of particles in solutionThe pure nickel solutions gave a value of 1017 plusmn 256 nm andthe Ni-PVP was 259plusmn44 nmThis result shows that the PVPfor the synthesized nickel can help prevent agglomerationin the aqueous solution during synthesis thus giving small

(a)

(b)

(c)

Figure 5 SEM images of (a) nickel (b) Ni-PVP and (c) Ni(OH)2

powder nanoparticles

nickel nanoparticles The Ni(OH)2particle size was 631 plusmn

162 nm in solution also showing some agglomeration insolution The DLS data places these particles in the nano-range while in solution which are nanopowders when dried

Scanning electronmicroscopywas also used to determineif the nanoparticles were in the nanometer range of sizeFigure 5 shows the SEM image of nickel and nickel hydroxidenanoparticles produced by the simplified chemical reduction


4500 4000 3500 3000 2500 2000 1500 1000 50040

50

60

70

80

90

100

110

120

1586

1240

16011270

PVP

Ni-PVP

Ni

1654

Tran

smitt

ance

()

Wave number (c )mminus1

Figure 6The infrared spectra of synthesized powders of pure PVPNi-PVP and Ni powders

method The measurements using the SEM were at theinstruments limits of size detection however the image stillshows that the powder particles are below 40 nm within thenanometer range measured by XRD

The FTIR spectra of nickel andNi-PVP nanoparticles canbe seen in Figure 6TheFTIR results show apeak at 1654 cmminus1for the carbonyl stretch for pure PVP The C=O stretch redshifts from pure PVP to 1601 cmminus1 as nickel is protected withPVP and continues to shift to pure nickel at 1586 cmminus1 [28]Another region to evaluate is the peaks between 1170 and1270 cmminus1 which signify the CndashN stretch in PVP [28] Inpure PVP the peaks are strong with three different peaksfor each of the CndashN bonds in PVP With Ni-PVP weakshoulder peaks are seen in the region around 1240 cmminus1 andthey completely disappear with pure nickel nanoparticlesThe FTIR spectrum of Ni(OH)

2in Figure 7 shows a hydroxyl

stretch from the Ni(OH)2lattice at 3629 cmminus1 and an ndashOndash

H stretch of the intercalated hydroxyl group from waterbetween 3100 and 3500 cmminus1 [29 30] Also an HndashOndashH bendis observed at 1605 cmminus1 from the vibration of free watermolecules [29]The spectrum also shows a sharpOndashH stretchat 608 cmminus1 from the hydroxyl lattice vibration and a weakpeak at 467 cmminus1 indicating a NindashO lattice vibration [30]

4 Conclusions

Nickel powders with nanosized particles are synthesizedchemically through the reduction of a nickel salt by hydrazinehydrate in a basic aqueous solution (pHsim125) using sonica-tion to control the reduction at around 55ndash65∘C The nickelhydroxide nanopowder was precipitated by titrating nickelchloride solution with hydrazine-sodium hydroxide at a finalmixture pH of sim10 The most notable features of this methodare the simple operation high yield and small particle sizesThe procedure yields pure nanocrystalline powders withparticle sizes ranging from 7 to 14 nm

4000 3500 3000 2500 2000 1500 1000 500

80

90

100

110

120

467

3629

608

3285

1605

Tran

smitt

ance

()

Wave number

Ni(OH)2

(c )mminus1

Figure 7 The infrared spectra of Ni(OH)2

powder

Conflict of Interests

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

Acknowledgment

Stephanie Garciarsquos work was supported by the NationalScience Foundation under Grant no CHE-1004878 as partof an NSF Research Experience for Undergraduates Programin the Department of Chemistry at the University of NorthTexas

References

[1] M T Reetz and W Helbig ldquoSize-selective synthesis of nanos-tructured transition metal clustersrdquo Journal of the AmericanChemical Society vol 116 no 16 pp 7401ndash7402 1994

[2] M Huang Y Shen W Cheng et al ldquoNanocomposite filmscontaining Au nanoparticles formed by electrochemical reduc-tion of metal ions in the multilayer films as electrocatalyst fordioxygen reductionrdquo Analytica Chimica Acta vol 535 no 1-2pp 15ndash22 2005

[3] B P S Chauhan J S Rathore and N Glloxhani ldquoFirst exampleof ldquopalladium-nanoparticlerdquo-catalyzed selective alcoholysis ofpolyhydrosiloxane a new approach to macromolecular graft-ingrdquo Applied Organometallic Chemistry vol 19 no 4 pp 542ndash550 2005

[4] J Zhang X Wang L Li C Li and S Peng ldquoEffect of reductantand PVP onmorphology and magnetic property of ultrafine Nipowders prepared via hydrothermal routerdquo Materials ResearchBulletin vol 48 no 10 pp 4230ndash4234 2013

[5] A Corrias G Ennas G Licheri GMarongiu and G PaschinaldquoAmorphous metallic powders prepared by chemical reductionof metal ions with potassium borohydride in aqueous solutionrdquoChemistry of Materials vol 2 no 4 pp 363ndash366 1990

[6] C Wang X M Zhang X F Qian Y Xie W Z Wang and Y TQian ldquoPreparation of nanocrystallive nickel powders throughhydrothermal-reduction methodrdquo Materials Research Bulletinvol 33 no 12 pp 1747ndash1751 1998


[7] L A Saghatforoush M Hasanzadeh S Sanati and RMehdizadeh ldquoNi(OH)

2

and NiO nanostructures synthesischaracterization and electrochemical performancerdquo Bulletin ofthe Korean Chemical Society vol 33 no 8 pp 2613ndash2618 2012

[8] S Papp and I Dekany ldquoStabilization of palladium nanoparticlesby polymers and layer silicatesrdquo Colloid and Polymer Sciencevol 281 no 8 pp 727ndash737 2003

[9] P K Khanna andV V V S Subbarao ldquoNanosized silver powdervia reduction of silver nitrate by sodium formaldehydesulfoxy-late in acidic pH mediumrdquoMaterials Letters vol 57 no 15 pp2242ndash2245 2003

[10] M Zhou S ChenH Ren LWu and S Zhao ldquoElectrochemicalformation of platinumnanoparticles by a novel rotating cathodemethodrdquo Physica E vol 27 no 3 pp 341ndash350 2005

[11] L Rodrıguez-SanchezMC Blanco andMA Lopez-QuintelaldquoElectrochemical synthesis of silver nanoparticlesrdquo Journal ofPhysical Chemistry B vol 104 no 41 pp 9683ndash9688 2000

[12] M T Reetz M Winter R Breinbauer T Thurn-Albrechtand W Vogel ldquoSize-selective electrochemical preparation ofsurfactant-stabilized Pd- Ni- and PtPd colloidsrdquo Chemistryvol 7 no 5 pp 1084ndash1094 2001

[13] H Feng Z Zhengyi X Yaofu W Wuxiang H Yafang and WRun ldquoA new electrolytic method of preparing ultrafine metallicpowdersrdquo Journal of Materials Processing Technology vol 137no 1ndash3 pp 201ndash203 2003

[14] W Yu and H Liu ldquoQuantity synthesis of nanosized metalclustersrdquo Chemistry of Materials vol 10 no 5 pp 1205ndash12071998

[15] N Aihara K Torigoe and K Esumi ldquoPreparation and charac-terization of gold and silver nanoparticles in layered laponitesuspensionsrdquo Langmuir vol 14 no 17 pp 4945ndash4949 1998

[16] U N Tripathi A Soni V Ganesan andG S Okram ldquoInfluenceof polyvinylpyrrolidone on particle size of Ni nanoparticlespreparationrdquo in Proceedings of the 56th Dae Solid State PhysicsSymposium vol 1447 of AIP Conference Proceedings pp 437ndash438 Kattankulathur India December 2011

[17] S-H Wu and D-H Chen ldquoSynthesis and characterization ofnickel nanoparticles by hydrazine reduction in ethylene glycolrdquoJournal of Colloid and Interface Science vol 259 no 2 pp 282ndash286 2003

[18] J W Park E H Chae S H Kim et al ldquoPreparation of fine Nipowders from nickel hydrazine complexrdquo Materials Chemistryand Physics vol 97 no 2-3 pp 371ndash378 2006

[19] D-P Wang D-B Sun H-Y Yu and H-M Meng ldquoMorphol-ogy controllable synthesis of nickel nanopowders by chemicalreduction processrdquo Journal of Crystal Growth vol 310 no 6 pp1195ndash1201 2008

[20] M B J G Freitas ldquoNickel hydroxide powder for NiO sdotOHNi(OH)

2

electrodes of the alkaline batteriesrdquo Journal of PowerSources vol 93 no 1-2 pp 163ndash173 2001

[21] D S Hall D J Lockwood S Poirier C Bock and B RMacDougall ldquoRaman and infrared spectroscopy of 120572 and 120573phases of thin nickel hydroxide films electrochemically formedon nickelrdquoThe Journal of Physical Chemistry A vol 116 no 25pp 6771ndash6784 2012

[22] R-Y Chen and K-G Zhou ldquoPreparation of ultrafine nickelpowder by wet chemical processrdquo Transactions of NonferrousMetals Society of China vol 16 no 5 pp 1223ndash1227 2006

[23] D V Goia ldquoPreparation and formationmechanisms of uniformmetallic particles in homogeneous solutionsrdquo Journal of Mate-rials Chemistry vol 14 pp 451ndash458 2004

[24] ldquoJoint Committee on Powder Diffraction Standard (JCPDS)rdquoTech Rep 00-004-0850 International Center for DiffractionData (ICDD) Swarthmore Pa USA

[25] B D Cullity and S R Stock Elements of X-ray DiffractionPrentice Hall New York NY USA 3rd edition 2001

[26] H P Klug and L E AlexanderX-ray Diffraction Procedures ForPolycrystalline and Amorphous Materials John Wiley amp SonsNew York NY USA 2nd edition 1974


[28] G G Couto J J Klein W H Schreiner D H Mosca A J Ade Oliveira and A J G Zarbin ldquoNickel nanoparticles obtainedby a modified polyol process synthesis characterization andmagnetic propertiesrdquo Journal of Colloid and Interface Sciencevol 311 no 2 pp 461ndash468 2007

[29] K Harish R Renu and S R Kumar ldquoSynthesis of nickelhydroxide nanoparticles by reverse micelle method and itsantimicrobial activityrdquo Research Journal of Chemical Sciencesvol 1 no 9 pp 42ndash48 2011

[30] Q Song Z Tang H Guo and S L I Chan ldquoStructuralcharacteristics of nickel hydroxide synthesized by a chemicalprecipitation route under different pH valuesrdquo Journal of PowerSources vol 112 no 2 pp 428ndash434 2002

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Journal ofNanomaterials


22 Synthesis of Nickel Nanopowder Thenickel nanopowderswere synthesized by reduction of nickel in an aqueoussolution with hydrazine hydrate acting as the reductantFor solution A 05 g of nickel chloride (NiCl

2sdot 6H2O) was

dissolved in 60mL of distilled water In a separate beakersolution B was prepared by dissolving 10 g of NaOH in20mLDI water and then adding 20mL of hydrazine hydrateSolution B was then added to solution A the combinedsolution turned into a royal blue color and was mixed witha stirring rod for 2 minutes resulting in a pH sim125 solutionFor the synthesis of nickel powder stabilized by PVP solutionB was prepared by dissolving 02 g of PVP in 3mL of absoluteethanol and then slowly introduced into the NaOH solutionthen hydrazine was added and the solution was stirred

According to Chen and Zhou the reaction temperatureneeds to stay below 70∘C in order to prepare ultrafine nickelparticles [22] The solution was sonicated for 15 minutesto sim55∘C allowed to sit for 15 minutes in order to controlthe temperature and then sonicated again for 15 minutes tosim65∘C to activate the precipitation of the nickel particlesDuring the activation period the solution initially becamegrey and coated along the side and bottom of the beaker andthen precipitated out to the bottom as a black powder Thenickel powder solution was centrifuged and washed with DIwater and absolute ethanol and was allowed to dry at roomtemperature

23 Synthesis of Nickel Hydroxide Nanopowder Solution Awas prepared in a 250mL volumetric flask composed of 119 gof nickel chloride dissolved in 50mL DI water then 200mLof absolute ethanol was added to the mark forming a greensolution The solution was transferred into a 500mL conicalflask Solution B was prepared in a 200mL volumetric flaskFirst 04 g of sodium hydroxide was dissolved in 100mL ofDI water 15mL of hydrazine hydrate was added and thendiluted to the mark with DI water Solution B was slowlydropped into solution A from a burette at a rate of sim02mLper minute and mixed with a magnetic stirrer The resultingsolution became cloudy green with precipitate forming assoon as the pH reached 68 and then turned to a cloudy bluegreen The mixed solution finally became a grey blue withthe addition of 80ndash90mL of solution B at a final pH of sim10The precipitated solution was centrifuged The powders werewashed with DI water and absolute ethanol and then freezedried

24 Characterization X-ray diffraction scans were run onthe synthesized nickel and nickel hydroxide powders with aSiemens D-500 diffractometer with Cu K120572 radiation (120582 =015405 nm) XRD scans were run at a step size of 005degrees and dwell time of 1 s The tube source was oper-ated at 40 kV and 30mA A Williamson-Hall analysis wasdone on each sample to calculate the particle size withsilicon powder as the standard for instrumental broadeningDynamic light scattering (DLS) (Beckman-Coulter DelsaNano-C) was used to determine the size of the nanoparticlecolloids in aqueous solution Each of the dried nanoparticlepowders was dispersed into an aqueous environment by

sonication for 30 minutes The samples were allowed toequilibrate for 60 seconds at 25∘C using a peltier device andscanned 40 times during the analysis The nanoparticles ofthe powders were characterized with a FEI Nova nanoSEM230 scanning electronmicroscope (SEM)with an ETD detec-tor Fourier transform infrared spectroscopy (FTIR) (PerkinElmer Spectrum One) spectra were obtained for each of thenanoparticle powders using the Attenuated Total Reflectance(ATR) attachment in the range of 450 to 4000 cmminus1

3 Results and Discussion

Nickel nanoparticles were synthesized from a nickel-hydrazine mixture in a sodium hydroxide environmentat high pH (sim125) which is favorable to form nickelnanoparticles [18 19] Hydrazine (N

2H4) has a standard

reduction potential of minus116 V in an alkaline solutionrepresented by the oxidation reaction (N

2H4+ 4OHminus =

N2+ 4H

2O + 4eminus) when mixed with the nickel ions

[18 23] Nickel which has a standard reduction potentialof minus025V is consequently able to be reduced by hydrazine(2Ni2+ + 4eminus = 2Ni) [18] Therefore a chemical reductionprocess of the nickel ion with hydrazine as a reductantin an alkaline aqueous solution can be simply shown inthe following equation 2Ni2+ + N

2H4+ 4OHminus rarr 2Ni +

N2+ 4H

2O Solution pH influences the synthesis of the

nickel nanoparticles as seen in the Nernst equation (1)The discharge of the nickel nanopowders was enhancedwhen the redox potential the driving force of the reactionincreased because of the increasing pH of the solutionby adding a strong base such as sodium hydroxide at acertain temperature and constant nickel ion concentration[17ndash19] In addition it has been shown that nickel powder agray-black powder cannot be produced if the pH is less than95 [19]

119864 = 119864

119900

minus

119877119879

4119865

ln 1

[OHminus]4[Ni2+]2

= 119864

1199002303

4119865

log [OHminus]4[Ni2+]2

(1)

However in order to avoid precipitation of hydroxide it iscrucial to maintain the reduction process at a high pH [18]This is because the standard reduction potential of Ni(OH)

2

is minus072V for Ni(OH)2+ 2eminus = Ni + 2OHminus

For the synthesis of Ni(OH)2nanopowder hydrazine was

slowly added dropwise into the nickel solution and graduallychanged from a clear green (initial pH of 4) to a cloudyblue green when the pH reached sim7 Hydrazine also actedas a ligand which was able to initially form a complex of[Ni(N

2H4)2]Cl2 [Ni(N

2H4)3]Cl2 or [Ni(N

2H4)6]Cl2in the

nickel solution with respect to the molar ratio of nickelto hydrazine [18] When the pH reached sim7 the complexbegan to form nickel hydroxide nanoparticles where thelocal pH around the hydrazine-sodium hydroxide dropletenvironment tended to be basic The particles were graduallycreated when the pH increased as a result of an enhancementof the reducing power of hydrazine [19] The addition of the


30 40 50 60 70 80 90 100 110

(222)

(311)

(220)(200)

(b) Ni-PVP

(a) Ni

Inte

nsity

(cou

nts)

(111)

2120579 (deg)



2H4)3]Cl2complex


[Ni(N2H4)

3

]Cl2+ 2NaOH


(2)



120573

119903cos 120579 = 119896120582

119871

+ 120578 sin 120579 (3)


03 04 05 06 07 08000

001

002

003

004

005

006

007

008

120573rcos120579

sin120579





120573

2

119903

= 120573

2

119898

minus 120573

2

119904

(4)


119904


119903cos 120579








20 40 60 80 100

210203

202201

200103

111

110

102

101

100

001

Inte

nsity

(cou

nts)

2120579 (deg)


01 02 03 04 05 06 070008

0009

0010

0011

0012

0013

sin120579

120573rcos120579


synthe-sized powder



plotDynamic light





(a)

(b)

(c)







4500 4000 3500 3000 2500 2000 1500 1000 50040

50

60

70

80

90

100

110

120

1586

1240

16011270

PVP

Ni-PVP

Ni

1654

Tran

smitt

ance

()








4 Conclusions


4000 3500 3000 2500 2000 1500 1000 500

80

90

100

110

120

467

3629

608

3285

1605

Tran

smitt

ance

()

Wave number

Ni(OH)2

(c )mminus1


powder



Acknowledgment


References









2















2



















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




30 40 50 60 70 80 90 100 110

(222)

(311)

(220)(200)

(b) Ni-PVP

(a) Ni

Inte

nsity

(cou

nts)

(111)

2120579 (deg)



2H4)3]Cl2complex


[Ni(N2H4)

3

]Cl2+ 2NaOH


(2)



120573

119903cos 120579 = 119896120582

119871

+ 120578 sin 120579 (3)


03 04 05 06 07 08000

001

002

003

004

005

006

007

008

120573rcos120579

sin120579





120573

2

119903

= 120573

2

119898

minus 120573

2

119904

(4)


119904


119903cos 120579








20 40 60 80 100

210203

202201

200103

111

110

102

101

100

001

Inte

nsity

(cou

nts)

2120579 (deg)


01 02 03 04 05 06 070008

0009

0010

0011

0012

0013

sin120579

120573rcos120579


synthe-sized powder



plotDynamic light





(a)

(b)

(c)







4500 4000 3500 3000 2500 2000 1500 1000 50040

50

60

70

80

90

100

110

120

1586

1240

16011270

PVP

Ni-PVP

Ni

1654

Tran

smitt

ance

()








4 Conclusions


4000 3500 3000 2500 2000 1500 1000 500

80

90

100

110

120

467

3629

608

3285

1605

Tran

smitt

ance

()

Wave number

Ni(OH)2

(c )mminus1


powder



Acknowledgment


References









2















2



















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




20 40 60 80 100

210203

202201

200103

111

110

102

101

100

001

Inte

nsity

(cou

nts)

2120579 (deg)


01 02 03 04 05 06 070008

0009

0010

0011

0012

0013

sin120579

120573rcos120579


synthe-sized powder



plotDynamic light





(a)

(b)

(c)







4500 4000 3500 3000 2500 2000 1500 1000 50040

50

60

70

80

90

100

110

120

1586

1240

16011270

PVP

Ni-PVP

Ni

1654

Tran

smitt

ance

()








4 Conclusions


4000 3500 3000 2500 2000 1500 1000 500

80

90

100

110

120

467

3629

608

3285

1605

Tran

smitt

ance

()

Wave number

Ni(OH)2

(c )mminus1


powder



Acknowledgment


References









2















2



















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




4500 4000 3500 3000 2500 2000 1500 1000 50040

50

60

70

80

90

100

110

120

1586

1240

16011270

PVP

Ni-PVP

Ni

1654

Tran

smitt

ance

()








4 Conclusions


4000 3500 3000 2500 2000 1500 1000 500

80

90

100

110

120

467

3629

608

3285

1605

Tran

smitt

ance

()

Wave number

Ni(OH)2

(c )mminus1


powder



Acknowledgment


References









2















2



















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





2















2



















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 synthesis of nickel and nickel hydroxide

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