Introduction
Superconductingtechnologyisatechnologywithgreatdevelopmentpotentialandgreatstrategicsignificanceinthe21stcentury.Superconductingmaterialshavehighcurrentcarryingcapacityandlowenergyconsumptioncharacteristics,andcanbewidelyusedinenergy,Defense,transportation,medicalandotherfields.Duetothehighcriticaltemperatureofhigh-temperaturesuperconductors,andthelowpriceofliquidammoniausedforitscooling,theoperationisconvenient,anditisanewenergymaterialwithpracticalsignificance.Sincethediscoveryofoxidesuperconductorsinthe1980s,therehasbeenanupsurgeinstudyinghigh-temperaturesuperconductivityaroundtheworld.Sincethen,peoplehavediscoveredvariousseriesofhigh-temperaturesuperconductingmaterialswithincreasinglyhighersuperconductingtransitiontemperatures.Atpresent,thetransitiontemperatureofmercury-basedsuperconductorshasreachedmorethan130K.Inadditiontobasicresearch,countriesaroundtheworldhavealsoinvestedalotofmanpowerandmaterialresourcesintheindustrializationresearchofsuperconductingmaterials.
History
High-temperaturesuperconductorsusuallyrefertomaterialsthataresuperconductingabovethetemperatureofliquidnitrogen(77K).Whensuperconductorswerediscovered(1911),theywereattractedbytheirpeculiarproperties(ie,zeroresistance,diamagnetism,andquantumtunnelingeffect).Butintheseventy-fiveyearssincethen,allthesuperconductorsthathavebeendiscoveredonlyshowsuperconductivityatextremelylowtemperatures(23K),sotheirapplicationshavebeengreatlyrestricted.
Hightemperaturesuperconductingmaterialsgenerallyrefertosuperconductingmaterialswhosecriticaltemperatureisabove77Kandtheresistanceisclosetozero.Theycanusuallybeusedinacheapliquidnitrogen(77K)refrigerationenvironment.Therearetwomaintypes:YttriumBariumCopperOxide(YBCO)andBismuthStrontiumCalciumCopperOxide(BSCCO).Yttrium-barium-copper-oxygenisgenerallyusedtopreparesuperconductingthinfilms,whichareusedinthefieldsofelectronicsandcommunications;bismuth-strontium-calcium-copper-oxygenismainlyusedforthemanufactureofwires.
In1911,KamerlinOnnisofLeidenUniversityintheNetherlandsaccidentallydiscoveredthatwhenmercurywascooledto-268.98°C,theresistanceofmercurysuddenlydisappeared;laterhediscoveredthatmanymetalsandalloysareIthasthecharacteristicsoflosingresistanceatlowtemperaturesimilartotheabove-mentionedmercury.Becauseofitsspecialconductivity,KamerlinOnniscalleditasuperconductingstate,andhewontheNobelPrizein1913forthis.
In1933,MeissnerandOlsenfeldoftheNetherlandsjointlydiscoveredanotherextremelyimportantpropertyofsuperconductors.Whenthemetalisinasuperconductingstate,themagneticinductioninthissuperconductoriszero.Butitsqueezedoutthemagneticfieldthatoriginallyexistedinthebody.Experimentsonsinglecrystalsolderballsfoundthatwhenthesolderballtransitionstoasuperconductingstate,themagneticfieldaroundthesolderballsuddenlychanges,andthelinesofmagneticforceseemtoberepelledoutofthesuperconductorallatonce.Peoplecallthisphenomenon"stepping".Snaeffect".
SinceCamerinOnnisdiscoveredthesuperconductivityofmercurynear4.2K,newsuperconductingmaterialshavebeendiscoveredalmostallovertheperiodictable,rangingfromthelightelementsboronandlithiumtothetransitionheavymetaluranium.Seriesetc.Theinitialresearchonsuperconductingmaterialsmostlyfocusedonelements,alloys,transitionmetalcarbidesandnitrides.By1973,aseriesofA15superconductorsandternarysuperconductorswerediscovered.Superconductingmaterialsneedtouseliquidheliumasarefrigeranttobeinasuperconductingstate,sotheirapplicationsaregreatlyrestricted.In1986,BernozandMullerdiscoveredthe35Ksuperconductinglanthanumbariumcopperoxygensystem.Thisbreakthroughdiscoveryledtothediscoveryofaseriesofrareearthbariumcopperoxidesuperconductorsathighertemperatures.Throughelementreplacement,atthebeginningof1987,WuMaokun(ZhuJingwu)oftheUnitedStatesandZhaoZhongxianoftheChineseInstituteofPhysicsannouncedthediscoveryofa90Kyttrium-barium-copper-oxygensuperconductor,achievingthefirstbreakthroughinthetemperaturebarrierofliquidnitrogentemperature(77K).BernozandMulleralsowonthe1987NobelPrizeinPhysicsfortheirpioneeringwork.
Thistypeofsuperconductorisusuallycalledahigh-temperaturesuperconductorbecauseitscriticaltemperatureisabovethetemperatureofliquidnitrogen(77K).Thediscoveryofyttrium-barium-copper-oxygensuperconductorsabovethetemperatureofliquidnitrogenhasprovidedordinaryphysicslaboratorieswiththeconditionsforconductingsuperconductingexperiments.Therefore,therehasbeenanupsurgeinexploringnewhigh-temperaturesuperconductorsaroundtheworld.Attheendof1987,ChinesescholarShengZhengzhiandothersfirstdiscoveredthefirstrareearth-freethallium-barium-copper-oxygenhigh-temperaturesuperconductor.Inearly1988,Japandevelopedabismuth-strontium-calcium-copper-oxygensuperconductorwithacriticaltemperatureof110K.InFebruary1988,ShengZhengzhiandothersfurtherdiscoveredthe125Kthalliumbariumcalciumcopperoxygensuperconductor.Afewyearslater(1993)Frenchscientistsdiscovereda135Kmercury-barium-calcium-copper-oxygensuperconductor.
Preparationprocess
Inordertomeettherequirementsofvariousapplications,high-temperaturesuperconductingmaterialsmainlyinclude:filmmaterials(thinfilm,thickfilm),bulkmaterials,wiresandstrips.
Thinfilm
High-temperaturesuperconductorfilmisthebasisofhigh-temperaturesuperconductingelectronicdevices,andthepreparationofhigh-qualityhigh-temperaturesuperconductingfilmsisthekeytodeviceapplications.Thepreparationofhigh-temperaturesuperconductingfilmsisalmostalwayscarriedoutbyvapordepositionorepitaxialgrowthoffilmsonsinglecrystalsubstrates.Aftertenyearsofresearch,thepreparationtechnologyofhigh-temperaturesuperconductingfilmshasbecomematureandhasreachedapracticallevel.Atpresent,thetwomostcommonlyusedandmosteffectivecoatingtechnologiesare:magnetronsputtering(MS)andpulsedlaserdeposition(PLD).Thesetwomethodshavetheirownuniquefeatures.Magnetronsputteringissuitableforlargeareas.Oneofthebestgrowthmethodsfordeposition.Thepulsedlaserdepositionmethodcaneasilymakethechemicalcompositionofthefilmconsistentwiththechemicalcompositionofthetarget,andcancontrolthethicknessofthefilm.
Thickfilm
Thehigh-temperaturesuperconductorthickfilmismainlyusedforHTSmagneticshielding,microwaveresonator,antenna,etc.Itisdifferentfromthefilmnotonlyinthethicknessofthefilm,butalsointhedepositionmethod.Themaindifferencesareinthefollowingthreeaspects:(1)Generally,thedepositionofthinfilmsrequirestheuseofsinglecrystalsubstrates;(2)Thedepositedthinfilmshaveacertaindegreeoforientationrelativetothecrystalorientationofthesubstrate;(3)Generally,themanufactureofthinfilmsrequirestheuseofvacuumtechnology.Therearemanythickfilmmethods:suchaspyrolyticsprayingandelectrophoreticdeposition,andthemostcommonlyusedtechnologiesarescreenprintingandsqueegee.Thesetwomethodshavebeenwidelyusedintheelectronicsindustry.
Wireandstrip
Theapplicationofsuperconductingmaterialsinstrongelectricityrequiresthathigh-temperaturesuperconductorsmustbeprocessedintocompositemulti-filamentwiresorstripscontainingsuperconductorsandacommonmetal.Butceramichigh-temperaturesuperconductorsItisverybrittle,soitcannotbedrawnintothinwires.Amongthemanypreparationmethodsofsuperconductingceramicwires,thebismuthceramicpowdersilvertuberollingmethod(AgPIT)isthemostmatureandidealMethod.Thecriticalcurrentdensityofpressedbismuthstripsismuchhigherthanthatofstripspreparedbyrollingtechnology.
Bulkmaterials
InitialoxidationThematerialsuperconductorispreparedbysolid-phasemethodorchemicalmethod,andthenthebulkmaterialisobtainedbytheusualpowdermetallurgyprocessessuchasmechanicalcompactionandsintering.Thepreparationmethodisrelativelysimple.
Application
Basedonthecurrentdevelopmentofsuperconductingtechnology,superconductingtechnologycanbeappliedandexpandedinthefollowingindustries:
Electricity
Thecombinationofsuperconductingtechnologyandelectricpowertechnologywillgivepowertothepowerindustry.Powergeneration,transmission,anddistributionhavebroughtrevolutionarychanges.Thepowerindustryisthemostimportantapplicationplaceandmarketforthesuperconductingindustry.Theapplicationsofsuperconductingtechnologyinpowermainlyinclude:
1)HightemperaturesuperconductivityCable
Theexpansionofexistingcableshasalwaysplaguedthedevelopmentofurbanpower.Traditionalurbanundergroundtransmissioncableshaveproblemssuchassmallflux,largeloss,thermalandoilpollutiontothesoilandgroundwater,andhighcivilconstructioncosts.Urbanpowercapacityexpansionisbecomingmoreandmoredifficult.High-temperaturesuperconductingcableshavetheadvantagesofsmallsize,lowcost,highenergysaving,nopollution,etc.,havehugeeconomicandenvironmentalbenefits,andwilleventuallyreplacetraditionalcables.
Thelarge-scaleapplicationofhigh-temperaturesuperconductingcablescangreatlyimprovetheoperatingefficiencyofpowertransmissionsystemsandreduceoperatingcosts.Atpresent,theoveralldevelopmenttrendofhigh-temperaturesuperconductingcablesintheworldistodeveloplarge-capacity,lowACloss,andultra-longhigh-temperaturesuperconductingcables.Accordingtoexpertestimates,high-temperaturesuperconductingcablesaremostlikelytobethefirsttobepracticalandcommercialized.
2)Superconductingmotor
Motoristhemostcommonlyusedelectricalequipment,buttraditionalmotorsconsumealotofpower.U.S.industryexpertsestimatethatindustrialmotorswithmorethan1,000horsepowerconsumeapproximately25%oftheU.S.energy.Comparedwithconventionalmotors,superconductingmotorshavetheadvantagesofgoodenergysaving,smallsize,largesingle-machinecapacity,lowcostandoperatingcosts,andgoodstabilityandperformance.Theyhavegoodeconomicandenvironmentalbenefits.Withthesamepowersupply,thesizeofthesuperconductingmotoris1/3oftheconventionalmotor,themanufacturingcostcanbereducedby40%,thecurrentlosscanbereducedby50%,andtheoperatingcostcanbereducedby50%.TheU.S.DepartmentofEnergyestimatesthatthelowlossofhigh-temperaturesuperconductingmotorscanreduceoperatingcostsbybillionsofdollarseachyear.
Inthemilitary,warshipsusehigh-temperaturesuperconductingmotors,whichhavesmallervolumeandweight,moreflexiblespacelayout,morereliableoperationofthepropulsionsystem,higherefficiency,moreconvenientcontrol,andbetterspeedregulationperformance.Itcangreatlyimproveconcealmentandachievehigh-speedandquietoperation,whichhasimportantmilitarysignificance.
3)Superconductingtransformer
Conventionaltransformershavemanyshortcomings,suchashighloadloss,largeweightandsize,lowoverloadcapacity,nocurrentlimitingcapability,oilpollutionandshortlifespanWait.IntheUnitedStates,thetotalinstalledcapacityoftransformersisabout3-4timesthetotalpowergeneration,andthegridlossofitspowersystemisabout7.34%ofthetotalpowergeneration,ofwhich25%istransformerloss.Incomparison,superconductingtransformershavetheadvantagesofsmallsize,lightweight,highvoltageconversionenergyefficiency,lowfireenvironmentalaccidentprobability,andnooilpollution,etc.,whichcanimprovethereliabilityandoperatingperformanceofthepowersystem,reducecosts,andsave
Energy,environmentalprotectionandotheraspectshaveimportantpracticalsignificance.
4)Superconductingcurrentlimiter:
Currentlimiter(FCL)isakindofpowerequipmentthatimprovesthestabilityofthepowergrid.Withthedevelopmentofsociety,thequalityrequirementsofthepowergridaregettinghigherandhigher,anditisdifficultforthetraditionalcurrentlimitertolimitthepulsecurrentofthepowergridinashorttime.Thehigh-temperaturesuperconductingcurrentlimiterjustmakesupfortheshortcomingsofthetraditionalcurrentlimiter.Itscurrentlimittimecanbelessthanonehundredmicroseconds,whichcanquicklyandeffectivelylimitthecurrent.Thesuperconductingcurrentlimiterusesthephysicalcharacteristicsofthesuperconductingstate-normaltransitionofthesuperconductortomeetthecurrentlimitingrequirements.Itcanintegratedetection,triggeringandcurrentlimitingatthesametime.Itisconsideredtobethebestandtheonlyonecurrentlyavailable.Effectiveshort-circuitfaultcurrentlimitingdevice.Since1989,theUnitedStates,Germany,France,SwitzerlandandJapanhavesuccessivelycarriedoutresearchonhigh-temperaturesuperconductingcurrentlimiters.Atpresent,thetechnicalperformanceofhigh-temperaturesuperconductingcurrentlimiterssuitableforpowerdistributionsystemsintheworldisclosetotheapplicationlevel,buttheyarestillinthedemonstrationteststage.
5)Superconductingenergystoragedevices
Superconductingenergystoragedevicesusesuperconductingcoilstodirectlystoreelectromagneticenergy,andthenreturntheelectromagneticenergytothegridorotherloadswhenneededAnelectricalfacility.Sincetheenergystoragecoiliswoundbyasuperconductingwireandmaintainedinasuperconductingstate,theenergystoredinthecoilispermanentlystoredwithalmostnolossuntilitneedstobereleased.Superconductingenergystoragedevicescanbeusednotonlytoadjustthepeaksandvalleysofthepowersystemortosolvetheimpactofinstantaneouspowerfailureofthepowergridonelectricalequipment,butalsotoreduceoreliminatethelow-frequencypoweroscillationofthepowergridtoimprovethevoltageandfrequencycharacteristicsofthepowergrid.ItcanalsobeusedFortheadjustmentofreactivepowerandpowerfactortoimprovethestabilityofthepowersystem.
Medical
1)MRIofthehumanbodyAkindofequipment.TraditionalMRIusesconventionalmagnets.Themagneticfieldissmallanditisdifficulttodetecttheinitiallesions.Atthesametime,themainmagneticfieldisinaclosedmagnetcavity.Duringscanning,thesubjectmustbeplacedinasmallspaceisolatedfromtheoutsideworld,whichiseasytocausepeopletoproduceClaustrophobiahasgreatlyaffectedthewideapplicationofthisdevice,andlow-temperaturesuperconductingmagnetsarethereforewidelyusedinMRI.Duetotheliquidheliumtemperaturerequirementsofcryogenicsuperconducting,itsoperationandmaintenancecostsarehigh.Somecountrieshaveacceleratedtheresearchofhigh-temperaturesuperconductingMRI.In1998,OxfordMagnetTechnologyandSiemensjointlydevelopedahigh-temperaturesuperconductingmagnetforhumanMRI.
Transportation
Magneticlevitationtrain
Withthedevelopmentofthenationaleconomy,thesocietyhashigherandhigherrequirementsfortransportation,andhigh-speedtrainshaveemerged.Comparedwiththeexistingfourtraditionaltransportationmodesofrailway,highway,waterwayandaviation,thesuperconductingmaglevtrainhastheadvantagesofhighspeed,safety,lownoiseandsmallarea,andisanidealtransportationtoolinthefuture.
ITindustry
1)Superconductingcomputers:
High-speedcomputersrequiredenselyarrangedcomponentsandconnectinglinesonintegratedcircuitchips,butdenselyarrangedcircuitsAlotofheatoccursduringwork,andheatdissipationisaproblemfacedbyVLSI.Theverylargescaleintegratedcircuitinthesuperconductingcomputer,theinterconnectionlinebetweenitscomponentsismadeofsuperconductingdeviceswithclosetozeroresistanceandultra-microheating,thereisnoheatdissipationproblem,andthecomputingspeedofthecomputerisgreatlyimproved.Inaddition,scientistsarestudyingtheuseofsemiconductorsandsuperconductorstomaketransistors,andevencompletelyusesuperconductorstomaketransistors.
2)Superconductingswitch:
Superconductingswitchcanbedividedintoresistanceswitchandinductanceswitch.Resistanceswitchusesthefollowingpropertiesofsuperconductors:ifyouchangeanyofthethreeparametersofmagneticfield,currentandtemperature,youcanmakeitchangefromazeroresistancestatetoaresistancestate.Forexample,usingacoldtubeasaswitchistousethemagneticfieldgeneratedbyacompletelysuperconductingcontrolelementtocontroltheresistanceofthegateelementbycausingthegateelementtoundergoasuperconducting---normaltransition.Thelow-resistancestateofthisswitchiszero,andthehigh-resistancestateistypicallyontheorderofmilliohms,sotheswitchratioisinfinite.Theprincipleofinductiveswitchingis:itisnottheinductanceofcircuitcomponentssuchascoilsandwires.Itcanbeusedtochangethesuperconductornearitbetweenthenormalstateandthesuperconductingstate,ortomovethesuperconductingsurfacenearthecircuitcomponenttomakeitthesamechange.