PDF Publication Title:
Text from PDF Page: 037
19 20 US 10,991,944B2 usingamulti-chanelbaterytester(BiologicVMP3).Elec- inmicro/mesopores.ThesulfurcontentintheCNFs/S trochemicalimpedancespectroscopy(EIS)measurements compositedeterminedbyTGAwas50wt%. wereperformedbetwen10mHzto10MHzfrequency rangeusinganACperturbationof10mVrmsamplitude (BiologicVMP3). 5 ResultsandDiscussion MaterialCharacterization FIG.7providesaschematicoutlineofaLi-Scelwith agammamonoclinicphasesulfurbasedcathodeincarbon ateelectrolyte.Briefly,activatedcarbonnanofibers(CNFs)10thermaltreatment werepreparedbyelectrospining10wt%polyacrylonitrile (PAN)inDMF.Theas-spunmatswerethensubjectedtoair stabilizationfolowedbycarbonizationinaninertenviron mentandCO2treatmentfor1hourtoformfre-standing TABLE 1 carbonnanofibers.The scaningelectronmicroscopy15bareCNFsandaftersulfurdeposition.ThebareCNFs (SEM)imagesinFIG.8Ashowasmoothcarbonnanofiber displaynosignificantdifractionpeaks.Awidehumpissen surfacewithanaveragediameterof-150nm.Aftersulfur from2thetaof20-30degresduetotheamorphousnature depositionintheautoclave,SEMimagesrevealaconsis- ofcarboninCNFs.However,afterthesulfurdeposition,we tentlyroughfibermorphologysugestinguniformandcon- searareandmetastablephaseofsulfur—themonoclinic formalcoatingofsulfur(FIG.8B).Fewregionsdisplay20gammaphase(Rosykite).Thisisstrikingbehaviorsince blocksofsulfurdepositedwithintheinter-fiberspacing. onlyorthorhombic-alpha(S8),rhombohedral(56),hexago Overaltheseimagesprovideclearevidencethatthesulfur nal(S8)andpolymericalotropesofsulfurareknowntobe islargelyontheoutercarbonnanofibersurface. stableatroomtemperature24.Nevertheles,repeatableXRD Tofurtherunderstandtheefectofsulfurdepositionon signaturesaftersulfurdepositiontreatmentshowthepres surface area and pore sizes of CNFs,Brunauer-Emmett- 25 ence of gamma-monoclinic sulfur in the samples. It is Teler(BET)surfaceareaanalysiswasconducted.FIGS. establishedintheliteraturethatthemonoclinicphases 8D-8EshowtheN2absorption/desorptionisothermplots (largelyaandB)arestableonlyattemperatures>95°C.2,23 andporesizedistributionofCNFsbeforeandaftersulfur andbelowthistemperaturethemonoclinicphasequickly deposition.ForCNFs,thegasuptakeincreasestoahigh convertsbacktothestableorthorhombicform.Onlya valueatalowrelativepresure(PZP<0.05),andtheadsorp-30handfulofreportsinthepasttwocenturieshaveven tionisothermexhibitsaplateauatmidleandhighrelative presures.ThehysteresislopatP/P0=0.2-1.0represents mesoporosity.Theadsorptionisothermisacombinationof IUPACtypesI&IVisothermswhichconfirmsthepresence ofbothmicroandmesoporesonCNFs21.However,afterthe35showntobestableforatleast395daysatromtemperature sulfurdepositionintheautoclave,weobservethechangeof theisothermsugestingadecreaseinsurfaceporeswith significantlylowergasuptake.PoresizedistributioninFIG. thatthecarbonhostcanfacilitatethestabilizationofa 8EdenotesCNFsportrayamulti-modalporestructureinthe monoclinicsulfurphaseifthenumberofcarbonatoms nanoscaleregimewithanaverageporesizeof2.916nmand40exceds0.3perS8unitcrystalstructure28.Inadition,itwas aporevolumeof0.409cm°/g.Afterthesulfurdeposition, recentlysugestedbyMoonetal.thatcarbonfacilitatesthe theCNFsdisplayanenormousreductioninporevolume formationandhelpsinretainingthemonoclinicstructureat (0.054cm/g)sugestingporefilingbysulfur.Porestruc- roomtemperatureforlongerperiods25.Inourstudy,we turalparametersofalthematerialsaresummarizedinTable hypothesizethatthemonoclinicgammaphaseformedat 1.TheBETandSEMdatasugestthatsulfurispartialy45elevatedtemperaturespenetratestheporouscarbonstruc confinedwithinthecarbonnanopores.Nevertheles,thereis turesandretainsitscrystalstructureevenaftercolingdue clearevidenceofexposedunconfinedsulfurontheexternal tothelocalcarbondensitywithinthepores.Thisunique carbonsurfacewhichdiferentiatesthestructureofthe crystalstructureoncetrapedwithintheporesposibly presentinventionfrompriorartstructureswherethedepos- propagatesthroughoutthesulfurblocksincludingthosethat itedsulfurisconfinedwithintheporesofthematerial.For50areexternalydepositedinan“unconfined”state. example,atleast2wt%,oratleast5wt%oratleast10wt FIGS.9Band9CshowtheEDX mappingandcore %oratleast20wt%ofthesulfurisdepositedonthe spondinglowmagnificationSEMimageexhibitinguniform surface.FIG.8Fshowsthethermogravimetricanalysison distributionofsulfur.Toconfirmthechemicalcomposition sulfur-depositedCNFsconductedininertnitrogenatmo- andsurfacepropertiesofpristinegamma-monoclinic-sulfur spherewithaheatingrateof10°C./minfromroomtem-5basedCNFcathodes(gammasulfurdepositedCNFs),XPS peratureto600°C.TheTGAcurveshowsmildinitialweight measurementswereperformedandtheresultsaredisplayed losbelow10°C.asociatedwithevaporationofadsorbed inFIGS.9D-9F.Thesurveyspectra,showninFIG.17, moisture.Acontinuousweightlosbeyondthispointwas showstheexistenceofCls,S2p,andOlspeaksinthe observedoverawidetemperaturewindowuntil300°C.with composite.Thepeakscenteredat284.6eV,531.0eV,and twodistinctdegradationrates.Themeltingofsulfurocurs6053eVcorespondtotheCls,Olsandtheadsorbedsurface at19°C.andsulfurstartstoevaporatesonafterduetoits hydroxylgroup(OH),respectively29.FIG.9Dshowsthe highvaporpresure.Thewidedecompositiontemperature high-resolutionS2pspectraofthecomposite.TheS2P3/2 rangeandmultipledegradationratesobservedinTGA peakat163.7eVandS2P1/2peakat164.9eVwithanarea furthercoroboratepartialpore-confinementofsulfur.While ratioof1:2anddeltaEof1.18eVarethecharacteristic thehigher-ratelower-temperatureweightlossugests65peaksofsolidsulfurinthecomposite30.Anotherbroadpeak evaporationofexposedunconfinedsulfur,thelower-rate centeredat168.8eVcanbeatributedtothesurfaceoxida higher-temperatureloscanbeatributedtosulfurconfined tionofsulfurduringhigh-temperaturesulfurdeposition Sample SBET CNFs before 558.4 0.2712 0.215 31.78 0.02603 0.00542 2.916 6.821 CNFs after thermaltreatment V. (még) (cm/g) (cm/g) (nm) FIG.9AshowstheroomtemperatureXRD paternsof mentionedthepresenceofgamma-monoclinicsulfurat roomtemperatureforshortperiods25-27. However,thepresentgammam-onoclinicphasehasben anditremainsstable,showingnosignsofphasechange.A recentDFTstudyonstabilizationofmetastablesulfurshows Averagepore diameterPDF Image | SYNTHESIS OF GAMMA MONOCLINIC SULFUR
PDF Search Title:
SYNTHESIS OF GAMMA MONOCLINIC SULFUROriginal File Name Searched:
US10991944.pdfDIY PDF Search: Google It | Yahoo | Bing
Sulfur Deposition on Carbon Nanofibers using Supercritical CO2 Sulfur Deposition on Carbon Nanofibers using Supercritical CO2. Gamma sulfur also known as mother of pearl sulfur and nacreous sulfur... More Info
CO2 Organic Rankine Cycle Experimenter Platform The supercritical CO2 phase change system is both a heat pump and organic rankine cycle which can be used for those purposes and as a supercritical extractor for advanced subcritical and supercritical extraction technology. Uses include producing nanoparticles, precious metal CO2 extraction, lithium battery recycling, and other applications... More Info
CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com (Standard Web Page)