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1、Thermoelectrics：EverylittlehelpsHEREisathought:approximately60%oftheenergyconvertedinpowergenerationiswasted.Thepriceofenergyishigh,bothintermsoftheactualcosttotheconsumerandtheconsequencesoftheclimatechangethatgeneratingpowerfromfossilfuelscauses.Ifevenasmallproportionofthiswas
2、tedheatcouldbeconvertedtousefulpower,itwouldbeagoodthing.Atthisweek’smeetingoftheAmericanPhysicalSociety,inBaltimore,MercouriKanatzidisofMichiganStateUniversityproposedsuchascheme.Headvocatesattachingthermoelectricdevicesthatconvertheatintoelectricitytochimneystacksandvehicleexh
3、austs,tosqueezemoreusefulenergyfrompowergeneration.Thetechnologytodosohasexistedforyears.Ifoneendofanelectricalconductorisheatedwhiletheotheriskeptcool,asmallvoltageiscreatedbetweenthetwo.Placingtwodissimilarmetals,orotherelectricallyconductivematerials,incontactwitheachotherand
4、thenheatingthemalsogeneratesavoltage.Suchdevices,calledthermocouples,arenowadaysusuallymadeusingsemiconductors.Theyarewidelyusedasthermometers.Butiftheycouldbemadecheaper,ormoreefficient,orboth,theycouldalsobeemployedtogeneratepower.DrKanatzidisisdevelopingnewthermoelectricmater
5、ialsdesignedtobecapableofconvertingupto20%oftheheatthatwouldotherwisebewastedintousefulelectricity.Thechallengeliesinfindingasubstancethatconductselectricitywellandheatbadly.Thesetwopropertiesdefinewhatphysicistscallthe“figureofmerit”ofathermoelectricsubstance,whichdescribesthep
6、oweradevicemadeofthatsubstancecouldgenerate.DrKanatzidis’sgroupaimstomakematerialswithhigherfiguresofmeritthanthoseattainablewithtoday’ssemiconductors.Sincetheelectricalpropertiesofsolidsdependontheircrystalstructures,hisgroupisexperimentingwithnewatomiclattices.Inparticular,the
7、yareworkingonagroupofchemicalscalledchalcogenides.Thesearecompoundsofoxygen,sulphur,seleniumandtelluriumthatarethoughttobeparticularlysuitableforthermoelectricapplicationsbecausetheirstructureallowselectriccurrentstoflowwhileblockingthermalcurrents.Theythushaveahighfigureofmerit
8、.DrKanatzidis’sgroupisdevelopingnewwaysofmaking
