ContentslistsavailableatScienceDirect
Journal
of
Asian
Ceramic
Societies
jo u r n al h om ep ag e :w w w . e l s e v i e r . c o m / l o c a t e / j a s c e r
Effect
of
alumina
addition
on
the
phase
transformation
and
crystallisation
properties
of
refractory
cordierite
prepared
from
amorphous
rice
husk
silica
Simon
Sembiring
a,∗,
Wasinton
Simanjuntak
b,
Rudy
Situmeang
b,
Agus
Riyanto
a,
Pulung
Karo-Karo
aaDepartmentofPhysics,FacultyofMathematicsandNaturalSciences,UniversityofLampung,Jl.Prof.SoemantriBrojonegoroNo.1,BandarLampung 35145,Indonesia
bDepartmentofChemistry,FacultyofMathematicsandNaturalSciences,UniversityofLampung,Prof.SoemantriBrojonegoroNo.1,BandarLampung, 35145,Indonesia
a
r
t
i
c
l
e
i
n
f
o
Articlehistory:
Received18January2017
Receivedinrevisedform25April2017 Accepted26April2017
Availableonline4May2017
Keywords:
Microstructure Composition Ricehusksilica Structure Refractoriness
a
b
s
t
r
a
c
t
Theeffectofaluminaadditionof5–30%byweightonphasetransformationandcrystallisationproperties ofrefractorycordieriteceramicspreparedfromamorphousricehusksilicafollowedbysintering treat-mentattemperatureof1230◦Cwasstudied.Thecrystallinityandmicrostructureofthesampleswere
characterisedusingX-raydiffraction(XRD)coupledwithRietveldanalysis,scanningelectronmicroscopy (SEM),respectively.Somephysicalpropertiesincludedensity,porosity,hardness,bendingstrength,and thermalexpansioncoefficientofthesampleswithdifferentaluminaadditionsweremeasured.Theresults showthatadditionofaluminapromotedcrystallisationofcordieriteintocrystallinespinel,corundum, cristobalite,inwhichwithadditionof10–30%alumina,thecordieritephasewaspracticallyundetected. Additionofaluminawasalsofoundtoincreasetheamountofspinel,whilecorundumandcristobalite decreasedfollowingaluminaadditionof10–30%.Thepresenceofspinel,corundum,andcristobalite resultedinincreasedofdensity,hardness,bendingstrengthandthermalexpansioncoefficient,whilefor porosity,theoppositewasobserved.Thermalexpansioncoefficientofthesampleswithaluminaaddition of15–30%reachtherelativelyconstantvalueof9.5×10−6/◦C,withthemaincrystallinephasewasspinel,
accompaniedbycorundumandcristobaliteinsmallerquantities.
©2017TheCeramicSocietyofJapanandtheKoreanCeramicSociety.Productionandhostingby ElsevierB.V.ThisisanopenaccessarticleundertheCCBY-NC-NDlicense(http://creativecommons.org/ licenses/by-nc-nd/4.0/).
1. Introduction
Ricehuskhasbecomeanimportantandcompetitivesourceof highpurity,reactive,andamorphoussilica,suitableforpreparation ofvarioussilicabasedadvancedmaterials.Inaddition,this renew-ableagricultureresidueisabundantlyavailableinmanycountries aroundtheworld,ensuringitssustainabilityinthefuture. Utilisa-tionofricehuskasasourceofsilicaissupportedbythesimplicity andlow costof theextractionmethodofthesilica.In the pre-viousinvestigations,severalresearchershaveshownthatsimple acid-leachingmethod[1–3]canbeappliedtoobtainhighpurity silica,which is more advantageous compared toother conven-tionalproduction techniques suchasvapor phase reaction and
∗Correspondingauthor.
E-mailaddress:simon.sembiring@fmipa.unila.ac.id(S.Sembiring).
sol–gelprocessappliedtoproducesilicafromothersources[4–6]. Supportingbyitsexcellentanduniqueproperties,suchashigh sur-facearea,amorphousphase,fineparticlesize,andreactivity,rice husksilicahasbeenconsideredasanattractiverawmaterialfor productionofvariousadvancedmaterialssuchassiliconnitride, magnesiumsilicide[7–9],solargradesilicon[10],siliconcarbide
[11], magnesium–alumina–silica [12], lithium–aluminum–silica
[13],andmullite[14].Inourpreviousinvestigations,reactive sil-icafromricehuskobtainedusingalkalineextractionmethodhas beenusedtosynthesizeseveralceramicsmaterialsinclude borosil-icate[15],carbosil[16],aluminosilicate[17],mullite[18,19]and cordierite[20,21].
Ofvarioussilicabasedmaterials,cordierite(Mg2Al4Si5O18)isan
importantappliedmaterialinmanydifferentbranchesof indus-tryduetoitsexcellentphysicalproperties,suchaslowcoefficient ofthermalexpansion,lowdielectricconstant[22,23],high chem-icalresistance[24],excellentthermalshockresistance[25],high
http://dx.doi.org/10.1016/j.jascer.2017.04.005
refractoriness[26],andhighmechanicalstrength[27].Forthese reasons,cordieritehasbeenoneofthemostpotentialceramics usedinmanyindustrialapplications,suchasrefractoryproducts, microelectronics,andintegratedcircuitboard[28,29],catalyst car-riersforexhaustgaspurification,heatexchangerforgasturbine engines[25,30],refractoryforfurnaces,aswellaselectricaland thermalinsulation[31,32].Inaddition,duetoitslowdielectric con-stantandthermalexpansioncoefficient,cordieriteiswidelyusedas anexcellentelectricinsulatorandhigh-thermalresistantmaterial. Inpreviousstudies[33,34],itwasreportedthatthermalexpansion ofcordieriteis2.2×10−6/◦C,whiletheothersreportedthevalue ofaround3.3× 10−6/◦C[21],1–4× 10−6/◦C [35],0.8–2× 10−6/◦C
[36,37]and2.2–4.5× 10−6/◦C[38].
Refractory materials typically consist of oxides suchas sili-con,aluminium,magnesium,andcalciumoxides.Theuseofthese oxidesisbasedontheirhighmeltingtemperaturesandtheability toformchemicallybondedframework thatcanwithstand tem-peraturesover1550◦C.Thecharacteristicsofrefractorystrongly
depend on the microstructure, crystalline phase, and thermal expansioncoefficient.Inoverall,refractorymaterialshouldexhibit highthermalshockresistance, fullydense,highfracture tough-ness,andlowthermalexpansion.Inourpreviousstudy[21],itwas foundthathardnessandbendingstrengthofrefractorycordierite increasedwithincreaseinsinteringtemperature,whileforthermal expansioncoefficient,theoppositewastrue.Otherstudies[25,39]
attemptedtosynthesizecordieritewithexcellentthermalshock resistancedemonstratedthatmicrostructurestronglyinfluenced thefracturetoughnessanddensificationofcordierite.
Modifyingcrystalwillchangetheirphysical,electrical,thermal, chemicalandmechanicalproperties,resultingmaterialswith supe-riorityanduniqueproperties.However,onlylimitednumbersof fundamentalstudythathavebeenemphasisedonthecordierite crystallisationprocessoccurringinmodifiedcomposition.In pre-viousstudy[40]theinvestigationwasconductedtoevaluatethe synthesisofcordieriteasthecomponentofrefractorymaterialfor highthermalapplicationsbyreducingtheAl2O3moleratiofrom2
to1.4.TheyfoundthatreductionofAl2O3moleratioto1.4,resulted
inbulkdensitytoreachthemaximumvalueof2.5kg/m3,whichis
closetothevaluefordensecordieriteceramic.Banuraizahetal.[41]
investigatedthedensificationofcordieriteandtheresultsobtained revealedthat densificationprocess wasmoreefficient withthe presenceofMgOexcessupto2.8moles,andatthesametime sig-nificantlyincreasethequantityofcordieritephase.Anotherstudy revealedthatadditionof10%aluminaresultedinincreasedporosity anddecreasedmodulusofrupture,whilefurtheradditionupto30% ledtodecreaseddielectricconstant[42].Amistaetal.[43] inves-tigatedtheinfluenceofthecompositiononthecordieritephase andreportedthatstabilityofcordieritephasewasstrongly depen-dentontheexcessofMgOandAl2O3.Theyfoundthattheexcessof
MgO/Al2O3ledtodegradationofcordierite,assuggestedbythe
for-mationofforsteriteandsilimanitephases,andalsothepresenceof spinel[41]andcristobalite[26].Inanotherstudy[44]itwasfound thatincreasedMgOandSiO2contentsenhancedtheformationof
␣-cordierite,andpossibly-cordierite,whereasincreasedalumina contentsuppressedtheformationof␣-cordieriteand-cordierite. Anotherschemeforcompositionmodificationofcordieritethat hasbeenattemptedisadditionofcomponentotherthanMgOand Al2O3.Inpreviousstudy[45]successfulproductionoffullydense
ceramicbyadditionof8wt%ZnOwasreported,inwhichcordierite emergedasthepredominantphase.Otherstudy[46]demonstrated thatcrystallisationofcordieritewithadditionofB2O3,resultedin
anincreaseinthehardnessandadecreaseinthethermal expan-sioncoefficient,withthemainphase ofcordierite.Anwaretal.
[47]reportedenhancedproductionofdenseceramicasaresultof copperadditiontocordierite.Additionofcopperupto40wt%was foundtoledtosignificantimprovementofcompressionstrength
and thermal conductivityof thecordierite, while the hardness decreases.Theresultsofseveralpreviousstudiesdiscussedabove demonstratedthatadditionofappropriateadditivescanpromote theformationofcordieritephase,mostlikelybydecreasingmelting pointandcrystallisationtemperatures.
Followingthesuccessfulutilisationofricehusksilicafor produc-tionofrefractorycordieritebythermaltreatmentinourprevious investigation[21],this current studywasaimed toexpand the investigationwiththeemphasisonmodificationofcomposition with addition of alumina in order to explore the relationship between composition and physical characteristics of refractory cordierite.Utilisationofaluminaisbasedonthefactthatduetoits excellentmechanicalproperties,aluminabasedceramicsarebeing increasinglyusedasasubstitutematerialforseveralapplications suchasabrasiveandcuttingtools.Thepresentstudyisconcerned ontheeffectofAl2O3(alumina)contentrelativetocordieriteonthe
phasetransformation,crystallisation,andphysicalcharacteristics ofrefractorycordieritepreparedfromamorphousricehusksilica. Togaininsightonseveralbasiccharacteristics,thecrystallisationof refractorycordieritewithaluminaadditionwerestudiedbymeans ofX-raydiffraction,andmicrostructuraldevelopmentofrefractory cordieritebySEMstudies.
2. Experimentalmethods
2.1. Materials
Rawhuskusedasasourceofsilicawasfromlocalricemilling industryinBandarLampungProvince,Indonesia.Aluminumoxide (Al2O3)andmagnesiumoxide(MgO)powderswithparticlesize
6.8–8.1mandpurity≥ 98.0%andabsolutealcohol(C2H5OH)were
purchasedfromMerck(kGaA,Damstadt,Germany).Other chemi-calsusedwereKOH5%,HCl5%,NaOH5%,anddistilledwater.
2.2. Procedure
Synthesisofcordieriterefractoryusingthesolid-statereaction methodwasperformedintwosteps,(i)preparationofsilicafrom ricehusk,(ii)preparationofalumina-cordieritewithvariousratios ofcordieritetoalumina.
2.2.1. Preparationofsilicapowderfromricehusk
Ricehusksilicawasproducedusingalkaliextractionmethod followingtheprocedurereportedinpreviousstudies[19,21].For extraction,50gdriedandcleanedhuskwasmixedwith500mlof 5%KOHsolutioninabeakerglass,followedbyboilingofthemixture for30min,andthenthemixturewasleftovernight.Themixture wasthenfilteredandthefiltrate(silicasol)wasacidifiedby drop-wiseadditionof5%HClsolutionuntilconversionofthesolintogel wascompleted.Thegelwasovendriedat110◦Cforeighthours
andthengroundintopowder.
2.2.2. Preparationofalumina-cordierite
Preparationofcordieritewasconductedfollowingthe proce-duresthathavepreviouslybeenapplied[20,21],bymixingraw materialswith thecomposition of MgO:Al2O3:SiO2 of 2:2:5 by
mass.The solid wasgroundinto powderby mortarand sieved toobtain thepowder withthesize of 200meshes. A seriesof alumina-cordieritesampleswithmassratiosofcordieriteto alu-mina of100:0, 95:5,90:10,85:15, 80:20,75:25 and70:30 was preparedbymixingaspecifiedamountsofcordieriteandalumina understirring.Eachofthesampleswaspressedinametaldiewith thepressureof2× 104N/m2toproducecylindricalpelletsandthe pelletsweresinteredattemperatureof1230◦Caccordingthe
Fig.1.TheX-raydiffractionpatternsofthesinteredsamplesattemperatureof 1230◦Cwithdifferentaluminacontent(a)0,(b)5,(c)10,(d)15,(e)20,(f)25,
and(g)30%.p=corundum,q=cristobalite,r=␣-cordierite,s=spinel,m=periclase.
temperatureprogrammedwithaheatingrateof3◦C/minand
hold-ingtimeof4hatpeaktemperatures.
2.2.3. Characterisation
TheXRDpattensofthesampleswereobtainedusingan auto-mated Shimadzu XD-610 X-ray diffractometer at the National AgencyforNuclearEnergy(BATAN),Serpong-Indonesiaoperated withCuK␣ radiation (=0.15418)radiation in the 5◦≤ 2≥ 80◦
range,withastepsizeof0.02,countingtime1s/step.TheX-ray tubewas operated at 40kV and 30mA, witha 0.15◦ receiving
slit.ThediffractiondatawereanalysedusingJADEsoftwareafter subtractingthebackgroundandstrippingtheCuK␣2pattern[48].
Polishedandthermallyetchedsampleswereusedfor microstruc-turalanalysisconductedwithSEM Philips-XL.Bulkdensity and apparentporosity weremeasuredbyArchimedesmethodusing distilledwaterasliquidmedia[49].Vickershardnesswas mea-suredusingaZwicktester,withthreereplicatesmeasurementfor eachloadingposition.Bendingstrengthormodulusrupture(MOR) wasdeterminedbythethree-pointmethodfollowingtheASTM C268-70.Themeasuringofthermalexpansioncoefficientwas con-ductedusingdilatometry(HarropDilatometer),inthetemperature rangeof150–600◦Cataheatingrateof5◦C/min.Thelinear
ther-malexpansioncoefficient(␣)wasautomaticallycalculatedusing thegeneralequation:␣=(L/L)(1/T)where:(L)istheincrease inlength,(T)isthetemperatureintervaloverwhichthesample isheatedand(L)istheoriginallengthofthespecimen.
3. Resultsanddiscussion
3.1. Effectofaluminaadditiononthephasetransformationand crystallisationofrefractorycordierite
TheXRDpatternsofthesampleswithdifferentalumina con-tentsafter sinteredat temperatureof 1230◦C are presented in
Fig. 1a–g. The phases identified with the PDF diffraction lines using search-match method[50],clearly show the presence of
␣-cordierite/Mg2Al4Si5O18(PDF-13-0294)withthemostintense
peakat2=10.50◦,spinel/MgAl
2O4(PDF-21-11520),at2=36.91◦,
corundum/␣-Al2O3(PDF-46-1212)at2=35.12◦,cristobalite/SiO2
(PDF-39-1425),at2=21.51◦,andpericlase/MgO(PDF-45-0946)at
2=42.91◦.
AccordingtoFig.1a,thepredominantcrystallinephaseinthe sample withoutadditionof aluminawas ␣-cordierite and with minorcrystallinephaseswerecorundumandspinel.Theprofiles ofcrystallinephaseofthesampleswithaluminaadditionare gen-erallysimilarFig.1a–g,intermofthecrystallinephasesidentified, exceptforthesamplewith5%aluminaaddition.Forthis partic-ularsample(Fig.1b),compared tothesample withoutalumina addition,theintensitiesofpeaksassociatedwith␣-cordieriteand spineldecreased,whereas corundumincreased,and cristobalite peaksbegantoappearstrongly.Onfurtherincreasingalumina con-tentto10%(Fig.1c),␣-cordieritepeaksdecreasedsignificantly,but spinel,corundum,andcristobaliteincreased,andthenewpeaks ofpericlasewasevidentlyexist.Withincreasingaluminafrom15 to30%,corundumandcristobalitepeaksevidentlydecreasedand spinelpeakclearly increased.Thischangein phasecomposition suggestedthatincreasedamountofaluminaledtomoreintensive diffusivereactionbetweenMgOandAl2O3,toproducemorespinel.
Thetendencyofathis trendalsoindicatedthatbinaryreaction betweenMgOandAl2O3ishighercomparedwithbinaryreaction
betweenMgOandSiO2.Thisbehaviorwasattributedtothe
forma-tionofMg–O–Albondofspinelphase,throughinteractionofAlO6
andMgO6octahedral[51,52,53].Thesefindingsdemonstratedthat
aluminatendstosuppressthegrowthofcordieritecrystals,as sup-portedbypreviousstudy[42].Thisfindingisalsoinagreementwith theresultofpreviousstudy[54],inwhichitwassuggestedthat theformationofspinelismostlikelyasaresultofinter-diffusion betweenaluminaandpericlase.Itwasobservedthatthe crytallisa-tionbecamemoreintensivewithincreasingthealuminacontent. At30%aluminaaddition,thesampleischaracterisedbythe pres-enceofthreedistinctcrystallinephases,namelyspinel,corundum andcristobaliteasseeninFig.1g.AccordingtoRietveldanalysis usingtheRieticaprogramversion1.70[55]andCrystalStructure Database[56],therefinedXRDpatternsofthesamplessinteredat 1230◦Cwiththealuminacontentof5and30%arepresentedin
Fig.2aandb.
Thebestfigureofmeritsandweightpercentage(wt%)forall sampleswerecompiledinTable1.Thegoodnessoffit(GoF)values relativelylowaccordingtobasicprincipleofGoF,inwhichtheGoF valuelessthan4%andtheRwpvalueoflessthan20%are consid-eredacceptable[57].AsshowninTable1,theamountofcordierite decreasedasthealuminacontentincreasedfrom5to30%, suggest-ingthatthephasecrystallisationwasstartedbyadditionof5%to producemorespinelandcontinuedtoproceedupto30%alumina addition,whichimpliesthatmorealuminareactedwithapericlase toformspinel.Thistrendisinagreementwithdecreasedamount ofcordieriteobservedastheamountofaluminaincreased.
Thesurfacemorphologiesofthesampleswithdifferentalumina contentsaftersubjectedtosinteringtemperatureof1230◦Cwere
analysedbySEM.Themicrographs presentedinFig.3a–gshow significanteffectofaluminaadditiononthesizeanddistribution oftheparticlesonthesurface.
Fig.2.XRDRietveldofthesinteredsamplesattemperatureof1230◦Cwithdifferentaluminacontent(a)5%and(b)30%.
Table1
Figure-ofmerits(FOMS)andweightpercentage(wt%)fromrefinementofXRDdataforthesamplessinteredat1230◦Cwithdifferentaluminaadditionfor6h.Estimated
errorsfortheleastsignificantdigitsaregiveninparentheses.[r=␣-cordierite,s=spinel,p=corundum,q=cristobalite,m=periclase].
Alumina(%) Rexp Rwp Rp GoF r s p q m
0 9.52 10.25 11.56 1.21 90.5[3] 4.7[4] 4.8[2] – –
5 8.90 10.52 11.32 1.39 50.6[2] 4.1[2] 15.2[3] 30.1[4] –
10 10.89 11.32 8.20 1.08 0.9[4] 14.5[3] 40.2[4] 42.3[2] 2.1[3]
15 11.23 11.68 8.50 1.06 0.6[2] 30.8[2] 36.9[5] 29.4[4] 2.3[2]
20 11.31 11.72 8.56 1.07 0.3[1] 36.6[2] 34.4[3] 25.3[4] 3.3[4]
25 10.61 10.92 7.92 1.06 0.4[2] 41.7[3] 31.1[5] 24.1[3] 2.7[3]
30 10.50 10.79 7.67 1.05 0.4[1] 45.4[2] 28.7[5] 22.5[4] 3.0[1]
Fig.3.Thescanningelectronmicroscopy(SEM)imagesofthesamplessinteredat1230◦Cwithdifferentaluminacontent(a)0%,(b)5%,(c)10%,(d)15%,(e)20%,(f)25%,and (g)30%.p=corundum,q=cristobalite,r=␣-cordierite,s=spinel.
finegrainsof␣-cordierite,coveredbylargergrainsofspinel, corun-dum,andcristobaliteclusters,whichaccordingtoXRDresultsare composedof␣-cordierite,spinel,corundum,andcristobalite.The presenceofspinel,corundum,andcristobalitephasesinthelast twosamplessuggestthatadditionofaluminaledto decomposi-tionof␣-cordierite,andinhibitedthegrowthof␣-cordieritephase. Theaboveobservationmaybedue toincreasedviscosityofthe glassymatrixasaresultofadditionalalumina,whichsuppressed themigrationofatomsandinhibitedthegrowthofcordierite.This
changeissupportedbytheresultsofXRDanalysispresentedin Fig.1bandc.
Fig.4.Density(a)andporosity(b)ofcordieriteasafunctionofaluminaaddition.
to30%,the␣-cordieritehasdecomposedcompletelyintospinel, corundumandcristobalite.Thesesurfacecharacteristicssuggested thatatthesecompositions,thecordieritephasehasbeenconverted intoliquefied corundum which penetratedthe periclase phase, thuspromotingtheformationofspinelasthedominantphase,as verifiedBytheXRDresults(seeTable1).WiththeRietveld calcu-lation,itwasfoundthatthequantityofspinelincreasedfrom30.8 to45.4wt%anddecreasedcorundumandcristobaliteasalumina increasedfrom15to30%.
3.2. Effectofaluminaadditiononthephysicalcharacteristicsof refractorycordierite
Thephysicalpropertiesofthesinteredsamplesatdifferent alu-minaadditionsareshowninFigs.4–6.
Fig.4representsthevariationofdensityandporositywith addi-tionof alumina.It is clearthatthe samplewithoutaddition of aluminahasthelowestdensity(2.34g/cm3)andthehighest
poros-ity(26.75%).Additionof 5%alumina causesa smallincrease of densityto2.52g/cm3,anddecreaseofporosityto25.65%.Addition
of10%aluminaresultsinasharpincreaseofdensity(3.51g/cm3)
butasmalldecreaseofporosity(24.59%).Thisdensitychangeis mostlikelyattributedtotheincreasedamountofspineland corun-dumphases(Table1),whileasmalldecreaseoftheporositymaybe associatedwithrelativelysmalldifferencebetweenthedensitiesof spinelandcorundumphases.
Further addition of alumina up to 30% shows only a small increaseof density buta sharpdecrease ofporosity (5.78%) up to20%aluminaadditionanda smalldecreaseofporosityupto 30%aluminaaddition.AsshowninFig.4a,thedensitywasslightly increasedandreachedthevalueof3.72g/cm3ataluminacontentof
30%.Asharpdecreaseoftheporosityupto20%aluminais proba-blyduetothematchbetweendensitiesofspinelandcorundum, whereasadditionof aluminain higherquantitiesdidnotcause a remarkabledecrease of porosity.Increasing thealumina con-tentover20%seemstosuppresstheporespropagationinsidethe matrix,causingnoabruptporositychangeoccurred.Althoughthe densityincreasedinasmallextentfrom15to30%alumina, signif-icantchangeoccurredintheporosityofthesesamples.Thisisdue tothehighdensityofspinelandcorundumwhichcauseddensity
Fig.5. Hardness(a)andbendingstrength(b)ofcordieriteasafunctionofalumina addition.
increased,andthehighdensitiesofspinelandcorundumwhich madeporositydecreased.Theseresultsareinaccordancewiththe resultsofothers,whoreportedthatthedensityofcorundum[58], spinel[59,60],andpericlase[61]phasesis higherthanthoseof cordieriteandcristobalite[59].Inthosepreviousstudies,the den-sityofcorundum,spinelandpericlaseare3.97,3.58and3.58g/cm3,
respectively,whileforcordieriteandcristobalite,thereported val-uesare2.3g/cm3and2.6g/cm3respectively.Theseliteraturedata
areinagreementwiththefindingsinthispresentstudy,inwhich increasedamountofaluminawasfoundtoenhancetheformation ofspinel(Table1),asdiscussedabove.
Fig.5representsthechangeofbendingstrengthandhardness ofthesamplesasaresultofaluminaaddition.
Fig.6. Coefficientofthermalexpansionofcordieriteasafunctionofalumina addi-tion.
inphasecompositionandporosityofthesamples.Otherfactors thatcontroltheandhardnessandbendingstrengthareprobably boththehomogeneityandthedistributionoftheparticles,which isinaccordancewiththesurfacemorphologyofthesamples,as showninFig.3d–g.
Fig.6showsthechangeinthermalexpansioncoefficientofthe samplesasafunctionofaluminaadditiontocordierite.
Itisclearlyobservedthatcordieritewithoutadditionofalumina hasthelowestthermalexpansioncoefficient(2.46× 10−6/◦C),and additionof5%aluminacausesasmallincreaseofthermal expan-sioncoefficient(2.52× 10−6/◦C).Theslowincreaseofthethermal
expansioncoefficientwithaluminaadditionof5%isattributedto thedecreaseofcordieriteandthepresenceofcorundumand cristo-balitephasesasshowninTable1.Furtheradditionofaluminaup to15%resultsinasharpincreaseofthethermalexpansion coeffi-cient,andthenslightlyincreasedtothefinalvalueof9.5×10−6/◦C at30%.It canbededucedfromtheresultsthat,asthealumina content increased,the thermal expansion coefficientincreased, most probably due to the decreased amount of cordierite and increasedamountofspinel(Table1),andalsodecreased poros-ity(Fig.4b).Thetrendobservedinthisstudyconcerningthermal expansioncoefficientisconsistentwiththerelationshipbetween thermalexpansioncoefficientwiththevolumefractionofthe sam-pleand porosityas describedin thepreviousstudies,in which itwasexplainedthatthermalexpansioncoefficienthasadirect relationshipwiththeamountofphase andaninverse relation-shipwiththeamountoftheporosity[61–63],withtheequation:
˛=(˛1v1+˛2v2+...+˛nvn)(1− P),where˛1,˛2and˛narethe ther-malexpansioncoefficientsofeachrawmaterial,v1,v2andvnare
thevolume fractions, and Pis theporosity. In this respect,for compositematerials,suchasceramic,thecoefficientofthermal expansionofthematerialiscontributionofthecoefficientof ther-malexpansionofeachphasepresentsinthesample,dependingon thevalueofthecoefficientandvolumefractionofthephase.Itcan beseenthatcoefficientofthermalexpansionofspinel,corundum andpericlasearehigherthanthoseofcordieriteandcristobalite, whichareinagreementwiththeresultsdescribedinpreviousstudy
[60].Morespecifically,itwasreportedthatthecoefficientof ther-malexpansionofpericlase[64],corundum[65],spinel[26,66]are
10.8× 10−6/◦C,8.8× 10−6/◦Cand9.17× 10−6/◦C,respectively,and
cristobaliteis2.6× 10−6/◦C,andthermalexpansioncoefficientof cordieriteis2.65×10−6/◦C[26,66].Inaccordancewiththeabove valuesreportedbyothers,itisclearthatincreasedthermal expan-sioncoefficientofthesamplesinvestigatedinthisstudyismost likelyassociatedwithincreasedamountofspinelanddecreased amountofcordierite,asconfirmedbyXRDresults(Table1),also decreasedporosity(Fig.4b).
4. Conclusions
Thisstudydemonstratedthatrefractorycordieritewas success-fullyproducedformricehusksilicaasrenewablerawmaterials. Furthermore, the cordierite was modified by addition of var-iedamountsofalumina,resultinginenhancedtransformationof cordieriteintospinel,corundumandcristobalite.This transforma-tionledtosignificantchangeofthecharacteristicsofthesamples, includeincreaseddensity,hardness,bendingstrengthandthermal expansion coefficient, followed by decreased porosity. Further-more,thesamplewithaluminaadditionof30%consistsof45.4% spinel,28.7%corundumand22.5%cristobalite.Thus,thesamples arecordieriterich-aluminatypes.Basedonthesecharacteristics,it isevidentthatrefractorycordieriteofthemodifiedsampleswith aluminaexistasdenseformwiththecharacteristicssuitablefor mechanicalapplications,suchasabrasivedevices.
Acknowledgments
TheauthorswishtothankandappreciatetheDirectorate Gen-eralofHigherEducation(DIKTI),MinistryofResearch,Technology, andHigherEducation,RepublicofIndonesiaforresearchfunding providedthroughtheCompetencyResearchGrantProgram,Batch II,2016,withcontractnumber:040/SP2H/LT/DRPM/II/2016 and 79/UN26/8/LPPM/2016.
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Journal of Asian Ceramic Societies
Volume 5 , Issue 2
June 2017
Available online at www.sciencedirect.com
Effect of compaction pressure on the performance of a non-symmetrical NiO–SDC/SDC composite anode fabricated by conventional furnace
M. SEYEDNEZHAD, A. RAJABI, A. MUCHTAR, M.R. SOMALU, P. OOSHAKSARAEI . . . 77
Preparation of forsterite refractory using highly abundant amorphous rice husk silica for thermal insulation
S.K.S. HOSSAIN, L. MATHUR, P. SINGH, M.R. MAJHI . . . 82
Effects of pore distribution of hydroxyapatite particles on their protein adsorption behavior
T. NAGASAKI, F. NAGATA, M. SAKURAI, K. KATO . . . 88
X-ray peak profi le analysis of solid-state sintered alumina doped zinc oxide ceramics by Williamson–Hall and size-strain plot methods
B. RAJESH KUMAR, B. HYMAVATHI . . . 94
Fabrication of hydrophobic polymethylsilsesquioxane aerogels by a surfactant-free method using alkoxysilane with ionic group
G. HAYASE, S. NAGAYAMA, K. NONOMURA, K. KANAMORI, A. MAENO, H. KAJI, K. NAKANISHI . . . 104
Structural and Magnetic properties of lithium ferrite substituted BaTi0.9Zr0.1O3 composite ceramics
G.R. GAJULA, L.R. BUDDIGA, M.P. DASARI, A.K. CHINTHABATTINI, J. KOLTE, S. KURIMELLA . . . 109
Elastic properties of lithium cobalt oxide (LiCoO2)
E.J. CHENG, N.J. TAYLOR, J. WOLFENSTINE, J. SAKAMOTO . . . 113
Effect of hydrophobic nano-silica on the thermal insulation of fi brous silica compacts
T.-W. LIAN, A. KONDO, T. KOZAWA, M. AKOSHIMA, H. ABE, T. OHMURA, W.-H. TUAN, M. NAITO . . . 118
Synthesis of novel green phosphate pigments in imitation of natural ores
H. ONODA, K. SUGIMOTO. . . 123
Dry sliding wear behavior of AA6061 aluminum alloy composites reinforced rice husk ash particulates produced using compocasting
J.A.K. GLADSTON, I. DINAHARAN, N.M. SHERIFF, J.D.R. SELVAM . . . 127
Synthesis, characterization and visible light photocatalytic activity of Mg2+ and Zr4+ co-doped TiO
2 nanomaterial for degradation of methylene blue
D.S. MESHESHA, R.C. MATANGI, S.R. TIRUKKOVALLURI, S. BOJJA . . . 136
Synthesis of galaxite by plasma fusion & its application in refractory for cement rotary kiln
L.N. PADHI, P. SAHU, N. SAHOO, S.K. SINGH, J.K. TRIPATHY . . . 144
Electrical and optical properties of nano-crystalline RE-Ti-Nb-O6 (RE = Dy, Er, Gd, Yb) synthesized through a modifi ed combustion method
F. JOHN, J. JACOB, J.K. THOMAS, S. SOLOMON . . . 151
Fabrication of polylactic acid/hydroxyapatite/graphene oxide composite and their thermal stability, hydrophobic and mechanical properties
M. GONG, Q. ZHAO, L. DAI, Y. LI, T. JIANG . . . 160
Structural and electronic transformations in quadruple iron perovskite Ca1xSrxCu3Fe4O12
I. YAMADA, K. SHIRO, N. HAYASHI, S. KAWAGUCHI, T. KAWAKAMI, R. TAKAHASHI, T. IRIFUNE . . . 169
Roles of ethylene glycol solvent and polymers in preparing uniformly distributed MgO nanoparticles
C. HAI, S. LI, Y. ZHOU, J. ZENG, X. REN, X. LI . . . 176
Synthesis of LaO0.5F0.5BiS2 nanosheets by ultrasonifi cation
A. MIURA, S. ISHII, M. NAGAO, R. MATSUMOTO, Y. TAKANO, S. WATAUCHI, I. TANAKA, N.C. ROSERO-NAVARRO, K. TADANAGA . . . 183
Effect of alumina addition on the phase transformation and crystallisation properties of refractory cordierite prepared from amorphous rice husk silica
S. SEMBIRING, W. SIMANJUNTAK, R. SITUMEANG, A. RIYANTO, P. KARO-KARO . . . 186
Synthesis and thermal study of SnS nanofl akes
M.D. CHAUDHARY, S.H. CHAKI, M.P. DESHPANDE . . . 193
Cordierite containing ceramic membranes from smectetic clay using natural organic wastes as pore-forming agents
W. MISRAR, M. LOUTOU, L. SAADI, M. MANSORI, M. WAQIF, C. FAVOTTO . . . 199
Unique crystallization behavior of sodium manganese pyrophosphate Na2MnP2O7 glass and its electrochemical properties
M. TANABE, T. HONMA, T. KOMATSU . . . 209
Effect of PVP on the synthesis of high-dispersion core–shell barium-titanate–polyvinylpyrrolidone nanoparticles
J. LI, K. INUKAI, Y. TAKAHASHI, A. TSURUTA, W. SHIN . . . 216
Journal of Asian Ceramic Societies
Volume 5, Issue 2, June 2017
Th
e Ceramic Society of Japan and the Korean Ceramic Society.
Journal of Asian Ceramic Societies
Journal of Asian Ceramic Societies
Shanghai Institute of Ceramics, Shanghai, China
LianMeng Zhang
Wuhan University of Technology, Wuhan, China
General Editor
Tokyo Medical and Dental University, Tokyo, Japan
Taras Kolodiazhnyi
National Institute for Materials Science, Tsukuba, Japan
Deug Joong Kim
Shanghai Institute of Ceramics, Shanghai, China
Jing-Feng Li
Tsinghua University, Beijing, China
Zhengyi Fu
Wuhan University of Technology, Wuhan, China
Cewen Nan
Tsinghua University, Beijing, China
Jianrong Qiu
South China University of Technology, Guangzhou, China
Yanchun Zhou
Aerospace Research Institute of Materials and Processing, Beijing, China
Shaoming Dong
Shanghai Institute of Ceramics, Shanghai, China
Guo-Jun Zhang
Shanghai Institute of Ceramics, Shanghai, China
Shu-Hong Yu
University of Science and Technology of China, Hefei, China
Wei-Hsing Tuan
National Taiwan University, Taipei, Taiwan
Chun-Hway Hsueh
National Taiwan University, Taipei, Taiwan
Gordon Thorogood
