简介:AnewapproachtothemassiveproductionofTiCwhiskerswithhighpurityandlowcostwaspresented.Itisamodifiedcarbothermalreductionmethod(MCTR)characterizedbyargonstreamflowingverticallyandpassingthroughtheinteriorofthemixtureofrawmaterials.Itisfoundforthefirsttimethatthereisanoptimumflowoftheupwardflowingargonstream,atwhichlargequantityofhighqualityTiCcanbeobtained.Thispaperdescribedthenewmethod,analyzedthemechanismandconditionsfortheformationofhighpurityTiCwhiskersonalargescale,andcomparedMCTRwiththetraditionalcarbothermalreductionmethod(TCTR).Basedontheanalysisandcomparison,itisconcludedthatinordertoproducehighqualitytransitionmetalcarbides,nitridesandcarbonitrideswithlowcostTCTRmustbereplacedbyMCTR.
简介:Si3N4/TiCnanocompositeceramicshavebeenfabricatedbyhotpressingtechniquewithAl2O3andY2O3asadditives.TheresultsshowedthatwelldispersedcompositepowderwascarriedoutbyaddingdispersantandadjustingpHvaluesofsuspensions.RemarkableincreaseinflexuralstrengthatroomtemperatureswasobtainedbyaddingnanoparticlesinSi3N4matrixwith10%(wtpct)ofnano-Si3N4and15%ofnano-TiC.Theflexuralstrength,fracturetoughnessandhardnesswere1025MPa,7.5MPa·1/2and15.6GPa,respectively.Themicrostructuresofmaterialswereanalyzedbyscanningelectronmicroscopy(SEM)andtransmissionelectronmicroscopy(TEM),whichindicatedthatTiCnanoparticlesdistributeinthematrixandatthegrainboundaries.Accordingtothefractureform,lowcontentsofnanoparticlescouldrefinematrixgrainsandleadtothecrackdeflectionaswellascrackpinning.Themultiplexmicrostructurewasformedbymixingnano-Si3N4particles.Thecracktrajectoriesexhibitedcrackdeflection,rod-likegrainbridgingandpull-out.
简介:ThemicrostructureandcompositionofTiC-Al2O3/Fefunctionallygradedmaterials(FGM)preparedbyself-propagatinghightemperaturesynthesisandpseudo-hotisostaticpressing(SHS/PHIP)werestudied,andtheresistingthermalshockbehaviorswereanalyzed.TheresultsshowthatTiC-Al2O3/FeFGMhasgradedcompositiondistribution.Nocross-sectioncrackthroughthelayerswasfoundinthetestsofthermalshockandfatigue.