Woody approach to recyclingconcrete.docx

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1、teinnanowiresmorequickly,moreeffi-ciently,andatlowercost.Theyhavealreadysucceededinmakingthewell-knownlabmicrobeEscherichiacoliintoaproteinnanowirefactorybysplicingintherequisiteGeobactergenes.Suchadevelopmentwouldremoveoneofthebottlenecksopeninguprapiddevelopmentofthetechnology,allowingthemtomasspr

2、oducetheproteinnanowiresthroughfermentationusingestablishedE.colitechnology.DavidBradley1369-7021hnpsdoi.org10.1016.mattod.2020.03.014Woody approach to recycling concreteForallitsincrediblydiversearrayofuses,concreteisaproblematicmaterialwhenitcomestodisposalattheendofusefullifeofabuildingorotherstr

3、ucture.However,theadditionofwoodfibersduringitsrecyclingmightgiveanewleaseoflifetowastematerialfromdemolishedbuildingsandcivilengineeringstructuresincludingbridges,accordingtoresearchfromTheUniversityofTokyo.TheteamattheUniversitysInstituteofIndustrialSciencehasdemonstratedthatwiththeappropriateprop

4、ortionsofwasteconcreteanddiscardedwooditispossibletomakeanewmaterialwithabendingstrengthsuperiortothatoftheoriginalconcrete.Giventheinitialenvironmentalcostsofmanufacturingcementandmakingconcrete,methodsofrecyclingwasteconcreteareanimportantpartofanyplansforconstructionsustainability.Concretehasbeen

5、usedinconstructionfordecades,itbuildsbridgesandreachesforthesky.Itsproductionusesconsiderableamountsofenergyandgenerateslargevolumesofcarbondioxide.Therehavebeeneffortstogreenwtheproductionprocesswithvaryingdegreesofsuccess.Ofcourse,concretehastwomaincomponents-aggregate,whichiscommonlygravelandcrus

6、hedstone,sand,andthecementthatbindsitalltogetherandallowsthemixturetobepouredintomouldsoronsurfacesafterwhichithardensintothetoughstructuralmaterialswithwhichtheworldisveryfamiliar.1.iLiang,firstauthorofnewworkreportedbytheteamatTheSixthInternationalConferenceonConstructionMaterials(ConMat20),points

7、outthatsimplyreusingaggregatefromoldconcretedoesnotimprovesustainabilityasitistheproductionofnewcementthatisdrivingclimatechangeemissions.Evenreusingtheaggregatewillrequirenewcement.Anew,environmentallyfriendlyapproachisnowneededtoclosethecircleonconcreteeconomics.Theresearchershavenowoptimizedtheir

8、methodbyadjustingthemixtureproportion,pressure,temperature,pressingduration,andwatercontenttomakeanewtypeofconcrete.Rigiditycomesfromhighlycross-linkedorganicpolymersinwood,ligninasitfiIlsthegapsintheconcreteandfunctionsasabindingagentwhenwasteconcretepowderisheated.uMostoftherecycledproductswemadee

9、xhibitedbetterbendingstrengththanthatofordinaryconcrete,addsseniorauthorYuyaSakai.Thesefindingscanpromoteamovetowardagreener,moreeconomicalconstructionindustrythatnotonlyreducesthestoresofwasteconcreteandwood,butalsohelpsaddresstheissueofclimatechange.*Thenewmaterialhasanotherputativeadvantageoverco

10、nventionalrecycledconcrete-itcouldbebiodegradable,atleastinthesensethatbio-degradingagentsmightultimatelybeusedtobreakdownthewood-containingmaterials,whichmightthenfindanotheruse.Theteamsuggeststhattheirmethodmightbeextendedtousingotherdiscardedplantmatter,ratherthanwood,tooptimizethepropertiesforot

11、herdifferentapplications.DavidBradley13697021httprdoi.og10.1016j.mattod.2020.03.013BetweenthesheetsTwo-dimensionalmaterialsremainahottopicandfindingwaystomakethemfromlayeredvanderWaalscrystalscouldopenupnewapplicationsinelectronics,optoelectronics,andquantumdevices.Now,researchersColumbiaUniversity,

12、NewYork,haveusedultra-flatgoldtapetoexfoliatevdWsinglecrystalslayerbylayerintonewmonolayers.Theobtainyieldsclosetounityandthesizeoftheir2Dlayersarelimitedonlybythedimensionsoftheoriginalbulkcrystal;uptothecentimeterscale.TheresearchersreportthatwMuIti-Iayerscouldbereassembledtoartificialstructures,s

13、uchasaMoSe2WSe2singlecrystalbilayerwithatwistanglechosentoquenchintralayerexcitonformation.Liuetal.,Science(2020)367,6480:903;Doi:https:/doi.Org/10.1126/science.aba1416.Theapproachisreminiscentoftheoriginalstickytapeexperimentsthatledtothefirstproductionofgraphene,madebypeelingoffamonolayerfromapenc

14、ilmarkonaglassslide.Theareaspossiblewiththisnewlyreportedgoldtapeexfoliationare,however,approximatelyamilliontimeslarger.Theteamexplainsthattheycanassemblethemonolayersintomacroscopicartificialstructures.Thesestructuresareinaccessiblethroughconventionalbulkcrystalgrowth.Forinstance,theycanproducelay

15、ersofmolybdenumdisulfidethatarealignedwitheachother.Theresultingstackslackmirrorsymmetryandsodemonstratestronglynonlinearopticalresponses.Inthatparticularexample,thematerialabsorbsredlightandemitsultravioletlightthroughsecond-harmonicgeneration.ThisapproachtakesUSonestepclosertomassproductionofmacro

16、scopicmono-layersandbulk-likeartilicialmaterialswithcontrollableproperties/explainsoneoftheprincipalinvestigatorsonthework,JamesHone.Theworkrepresentsanewwaytoscaleuptheproductionof2DmaterialsthathasnotbeenpossiblewithconventionalapproachessofarwherethinfiImgrowthhasvariouslimitationsintermsofmaterialquality,reproducibility,andtherequirementforhightemperatures.Otherteamshaveusedgoldtoexfoliatelarge2