简介:Ni-dopedphenolresinwaspreparedwith1∶100massratioofNi(NO_3)_2·6H_2Otothermosettingphenolresintooptimizethestructureandpropertiesofpyrolyticcarbonderivedfromphenolresinandincreaseitscarbonyield.Thespecimenswerecuredat200℃andcarbonizedunderdifferentatmospheres(carbon-embeddedatmosphereandAratmosphere)andatdifferenttemperatures(600,800,1000and1200℃)for3h,respectively.Thecarbonyieldwasmeasured.ThermaldecompositioncharacteristicsofNi-dopedphenolresin,andtheoxidationresistance,phasecompositionandmicrostructureofpyrolyticcarbonwerecharacterizedbydifferentialscanningcalorimetry,X-raydiffraction,energydispersivespectroscopy,scanningelectronmicroscopyandtransmissionelectronmicroscopy.TheresultsshowthatthecarbonyieldofNi-dopedphenolresincarbonizedat800or1000℃isincreasedsignificantly,comparedwiththatwithoutanydopants.ThegraphitizationdegreeofpyrolyticcarbonstructurederivedfromNi-dopedphenolresinincreaseswiththeincreaseofcarbonizationtemperature.Themassivemulti-wallcarbonnanotubesof50-100nmindiameterandofmicrometrescaleinlengtharegeneratedat1000℃.Comparedwiththecarbonembeddedatmosphere,carbonnanotubescanbemoreeasilygeneratedinAratmosphere,resultinginhighercarbonyieldanddegreeofcrystallinityofthepyrolyticcarbonderivedfromNi-dopedphenolresin.TheoxidationresistanceofthepyrolyticcarbonderivedfromNi-dopedphenolresinat1200℃isimprovedsignificantlyanditshighestoxidationtemperatureisincreasedbyabout84℃,comparedwiththatfromNifreephenolresin.
简介:ThemechanicalpropertiesofpressurelesssinteringFe-Si3N4bondedSiCandSi3N4bondedSiCwithsamemanufactureprocesshavebeencomparedinthispaper.TheoxidizingmechanismofFe-Si3N4bondedSiCceramicmatrixcompositehasbeeninvestigatedespeciallythroughTG-DSC(thermogravimetricanalysis-differentialscanningcalorimeter)experiment.DuringoxidationprocedurethemainreactionistheoxidationofSiCandSi3N4,SiO2whichformprotectingfilmtopreventfurtheroxidizing.AndresidualironinthesamplesbecomeFe2O3andFe3O4,theoxidationkineticsat1100~1300℃ofre-Si3N4bondedSiChasbeenstudiedespecially.Theweightgainperunitareaatinitialstagechangesaccordingtobeelinerule,inthemiddleaccordingtoconic,andinthelastoxidationperiodfollowsparabolarule.