Introduction
Boron(B)isalightelementthatformsstableborideswithtransitionmetals,amongwhichcompoundswithhighmeltingpointsareformedwithelementsofgroupIVA,groupVAandgroupVIA.Thecrystalstructureofborideisdeterminedbythestructuralcharacteristicsoftheboronatom.ThechemicalstabilityofboridesgraduallydecreasesfromIVAtoVIA.ThemoststableboridesareTiB2,ZrB2andHfB2Wait.
People'sresearchonboridefilmsisfarlessin-depthandsufficientthannitrideandcarbidefilms.Intermsofhardness,boridesareequivalenttocarbides,andsomeareslightlyhigher.Thisisbecausethedegreeofcovalentbondingofboridesishigherthanthatofcarbides.However,borideisquitebrittle,itsinertnessisstrong,anditschemicalpropertiesarestable,soitisusedinsomefields.Suchasprotectivecoatingandhardalloycoatedtools.MostboridefilmsarepreparedbyCVDmethod,butreactivesputteringanddirectsputteringmethodsarealsousedtoprepareboridefilms.
Crystalstructureofboride
Singlebond,doublebond,networkandspatialframeworkformstructuralunitsbetweenboronatomsintheboridelattice.Astherelativecontentofboronintheborideincreases,thestructuralunitbecomesmorecomplex.(Asshownin"TheConfigurationofBoronAtomsinBorides")
Generallyspeaking,themorecomplexthestructureoftheboronatom,thelesslikelyitistobehydrolyzed,andthemorestableitisagainstoxidationandnitridation.
Intransitionmetalborides,thechemicalbondbetweenthemetalatomandtheboronatomisanelectronicbond,sothattheboronatomistransformedintoapositivelychargedionoratomicskeleton,andthereisacovalentbondbetweentheboronatoms.key.
Preparationmethodofborides
Themainmethodofmanufacturingrefractorymetalboridesis
①Metalandboronaredirectlycombinedathightemperatureandthereactionformulais
Me+B—→MeB
②Reducingthemixtureofmetaloxideandboricanhydridewithcarbonis
2MeO+B2O3+5C—→2MeB+5CO
③Aluminum(silicon,magnesium)thermalmethod,aluminumorsilicon,magnesiumreducesoxides,sothatthegeneratedmetalandboronfurtherinteractThefunctionis
MeO+B2O3+AI(Si,Mg)—→MeB+Al(Si,Mg)oxide
p>④Useboroncarbideandcarbontoreducemetaloxidesto
4MeO+B4C+3C—→4MeB+4CO
⑤Useborontoreducerefractorymetaloxidesas
xMeO+2xB—→xMeB+(BO)x
Typesofboride
Borontribromide
Productintroduction:colorlessorslightlyyellowfumingliquidwithastrongpungentodor.Thecriticaltemperatureis300°Candtherefractiveindexis1.5312.
Titaniumdiboride
Productintroduction:Titaniumdiborideisoff-whitehexagonalcrystalorpowder,odorless.Ithasameltingpointof2980°C,adensityof4.5to4.52,andahardness(Hi)of3600.Ithasexcellentoxidationresistanceandelectricalconductivity.TheaverageparticlesizeD=4～8μm.
ChromiumDiboride
Productintroduction:meltingpoint1760℃,goodoxidationresistance,hightemperaturestrength.
Calciumhexaboride
I.Properties:
ThemolecularformulaofcalciumhexaborideisCaB6,whichisadarkgraypowder.Meltingpointis2235℃,relativedensity(15℃)2.33g/cm3,hardness(Mohs)9,insolubleinhydrochloricacid,hydrofluoricacid,dilutesulfuricacid.Itisinsolubleinwaterandcanbecorrodedbyoxidantssuchaschlorine,fluorine,nitricacidandhydrogenperoxide,andreactsveryslowlywithalkali.Atroomtemperature,itisstableandnon-flammableintheair.Ithassemiconductorpropertiesandneutronabsorptionproperties,andisnon-toxic.
2.Quality:
B≥55.5%Ca≥30%C≤8%
Granularity:20#～60#,20#～80#,100#,325#～400#oraccordingtocustomerrequirements2.Usedasaboron-containingadditiveforanti-oxidation,anti-erosionandimprovingthermalstrengthofdolomiteandmagnesiumdolomiterefractories;
3,usedasadeoxidizinganddegassingagentforhigh-conductivitycoppertoincreasestrengthandDeoxidizerforoxygen-freecopperandpurecoppercastings
4.Usedasanewtypeofanti-neutronmaterialinthenuclearindustry;
5.Usedasaspin-electroniccomponentwithaCurietemperatureof900KNewsemiconductormaterialsused;
6,usedasrawmaterialsforthemanufactureofborontrichloride(BCl3)andamorphousboron;
7,usedForthemanufactureofhigh-puritymetalborides(TiB2,ZrB2,HfB2,etc.)andhigh-purityboronalloys(Ni-B,Co-B,Cu-B,etc.)rawmaterials;
8,usedtomanufacturecatalyst-containingcalcium-boronnitride(Ca3B2AmixtureofN4)andhexagonalnitride,usingittoproducecrystallinecubicboronnitridewithexcellentperformance;
9.Usedasadesulfurization,deoxygenationandboronadditionagentforboronalloycastiron;
10.Usedasdesulfurization,deoxidationandboronincreaseagentforboronsteel;
11.Crystalrefinerinspecialsteel.
Propertiesandusesofboride
Boridehasthecharacteristicsofhighconductivity,highmeltingpoint,highhardnessandhighstability:Boridehasrelativelyhighthermalconductivityandstrength,soThethermalstabilityisrelativelygood,andtheoxidationresistanceofboridesathightemperaturesisthebestinGroupIVBmetalborides.
Theboridesaresolubleinmoltenalkali.Theboridesofrareearthandalkalineearthmetalsarenotcorrodedbyhumidairordilutehydrochloricacid,butaresolubleinnitricacid.Almostallborideshavetheappearanceandpropertiesofmetals,withhighconductivityandpositivetemperaturecoefficientofresistance.TheboridesofTi,Zr,andHfhavebetterconductivitythantheirmetals.
Thecreepresistanceofboridesisverygood.Forgasturbinesandrocketsthatrequirematerialstoworkathightemperaturesforalongtime,andcanmaintainstrength,resistdeformation,resistcorrosion,andheatshockresistance,boronChemicalshaveveryimportantsignificance.Variousalloysorcermetsbasedonborides,carbides,andnitridescanbeusedtomanufacturerocketstructuralcomponents,aviationequipmentcomponents,turbinecomponents,sampleholdersforhigh-temperaturematerialtestingmachines,partsofinstruments,bearings,andmeasurementofhightemperatureConeheadforhardnessandsomestructuralpartsofnuclearenergydevice,etc.