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1、Thermoelectrics：EverylittlehelpsHEREisathought:approximately60%oftheenergyconvertedinpowergenerationiswasted.Thepriceofenergyishigh,bothintermsoftheactualcosttotheconsumerandtheconsequencesoftheclimatechangethatgeneratingpowerfromfossilfuelscauses.Ifevenasmallproportio
2、nofthiswastedheatcouldbeconvertedtousefulpower,itwouldbeagoodthing.Atthisweek’smeetingoftheAmericanPhysicalSociety,inBaltimore,MercouriKanatzidisofMichiganStateUniversityproposedsuchascheme.Headvocatesattachingthermoelectricdevicesthatconvertheatintoelectricitytochimne
3、ystacksandvehicleexhausts,tosqueezemoreusefulenergyfrompowergeneration.Thetechnologytodosohasexistedforyears.Ifoneendofanelectricalconductorisheatedwhiletheotheriskeptcool,asmallvoltageiscreatedbetweenthetwo.Placingtwodissimilarmetals,orotherelectricallyconductivemater
4、ials,incontactwitheachotherandthenheatingthemalsogeneratesavoltage.Suchdevices,calledthermocouples,arenowadaysusuallymadeusingsemiconductors.Theyarewidelyusedasthermometers.Butiftheycouldbemadecheaper,ormoreefficient,orboth,theycouldalsobeemployedtogeneratepower.DrKana
5、tzidisisdevelopingnewthermoelectricmaterialsdesignedtobecapableofconvertingupto20%oftheheatthatwouldotherwisebewastedintousefulelectricity.Thechallengeliesinfindingasubstancethatconductselectricitywellandheatbadly.Thesetwopropertiesdefinewhatphysicistscallthe“figureofm
6、erit”ofathermoelectricsubstance,whichdescribesthepoweradevicemadeofthatsubstancecouldgenerate.DrKanatzidis’sgroupaimstomakematerialswithhigherfiguresofmeritthanthoseattainablewithtoday’ssemiconductors.Sincetheelectricalpropertiesofsolidsdependontheircrystalstructures,h
7、isgroupisexperimentingwithnewatomiclattices.Inparticular,theyareworkingonagroupofchemicalscalledchalcogenides.Thesearecompoundsofoxygen,sulphur,seleniumandtelluriumthatarethoughttobeparticularlysuitableforthermoelectricapplicationsbecausetheirstructureallowselectriccur
8、rentstoflowwhileblockingthermalcurrents.Theythushaveahighfigureofmerit.DrKanatzidis’sgroupisdevelopingnewwaysofmaking
