Woody approach to recyclingconcrete.docx

teinnanowiresmorequickly,moreeffi-ciently,andatlowercost.Theyhavealreadysucceededinmakingthewell-known"lab"microbeEscherichiacoliintoaproteinnanowirefactorybysplicingintherequisiteGeobactergenes.Suchadevelopmentwouldremoveoneofthebottlenecksopeninguprapiddevelopmentofthetechnology,allowingthemtomassproducetheproteinnanowiresthroughfermentationusingestablishedE.colitechnology.DavidBradley1369-7021hnpsdoi.org10.1016.mattod.2020.03.014Woody approach to recycling concreteForallitsincrediblydiversearrayofuses,concreteisaproblematicmaterialwhenitcomestodisposalattheendofusefullifeofabuildingorotherstructure.However,theadditionofwoodfibersduringitsrecyclingmightgiveanewleaseoflifetowastematerialfromdemolishedbuildingsandcivilengineeringstructuresincludingbridges,accordingtoresearchfromTheUniversityofTokyo.TheteamattheUniversity'sInstituteofIndustrialSciencehasdemonstratedthatwiththeappropriateproportionsofwasteconcreteanddiscardedwooditispossibletomakeanewmaterialwithabendingstrengthsuperiortothatoftheoriginalconcrete.Giventheinitialenvironmentalcostsofmanufacturingcementandmakingconcrete,methodsofrecyclingwasteconcreteareanimportantpartofanyplansforconstructionsustainability.Concretehasbeenusedinconstructionfordecades,itbuildsbridgesandreachesforthesky.Itsproductionusesconsiderableamountsofenergyandgenerateslargevolumesofcarbondioxide.Therehavebeeneffortsto"greenwtheproductionprocesswithvaryingdegreesofsuccess.Ofcourse,concretehastwomaincomponents-aggregate,whichiscommonlygravelandcrushedstone,sand,andthecementthatbindsitalltogetherandallowsthemixturetobepouredintomouldsoronsurfacesafterwhichithardensintothetoughstructuralmaterialswithwhichtheworldisveryfamiliar.1.iLiang,firstauthorofnewworkreportedbytheteamatTheSixthInternationalConferenceonConstructionMaterials(ConMat'20),pointsoutthatsimplyreusingaggregatefromoldconcretedoesnotimprovesustainabilityasitistheproductionofnewcementthatisdrivingclimatechangeemissions.Evenreusingtheaggregatewillrequirenewcement.Anew,environmentallyfriendlyapproachisnowneededtoclosethecircleonconcreteeconomics.Theresearchershavenowoptimizedtheirmethodbyadjustingthemixtureproportion,pressure,temperature,pressingduration,andwatercontenttomakeanewtypeofconcrete.Rigiditycomesfromhighlycross-linkedorganicpolymersinwood,ligninasitfiIlsthegapsintheconcreteandfunctionsasabindingagentwhenwasteconcretepowderisheated.uMostoftherecycledproductswemadeexhibitedbetterbendingstrengththanthatofordinaryconcrete,"addsseniorauthorYuyaSakai."Thesefindingscanpromoteamovetowardagreener,moreeconomicalconstructionindustrythatnotonlyreducesthestoresofwasteconcreteandwood,butalsohelpsaddresstheissueofclimatechange.*Thenewmaterialhasanotherputativeadvantageoverconventionalrecycledconcrete-itcouldbebiodegradable,atleastinthesensethatbio-degradingagentsmightultimatelybeusedtobreakdownthewood-containingmaterials,whichmightthenfindanotheruse.Theteamsuggeststhattheirmethodmightbeextendedtousingotherdiscardedplantmatter,ratherthanwood,tooptimizethepropertiesforotherdifferentapplications.DavidBradley13697021httprdoi.o<g10.1016j.mattod.2020.03.013BetweenthesheetsTwo-dimensionalmaterialsremainahottopicandfindingwaystomakethemfromlayeredvanderWaalscrystalscouldopenupnewapplicationsinelectronics,optoelectronics,andquantumdevices.Now,researchersColumbiaUniversity,NewYork,haveusedultra-flatgoldtapetoexfoliatevdWsinglecrystalslayerbylayerintonewmonolayers.Theobtainyieldsclosetounityandthesizeoftheir2Dlayersarelimitedonlybythedimensionsoftheoriginalbulkcrystal;uptothecentimeterscale.TheresearchersreportthatwMuIti-Iayerscouldbereassembledtoartificialstructures,suchasaMoSe2WSe2singlecrystalbilayerwithatwistanglechosentoquenchintralayerexcitonformation.Liuetal.,Science(2020)367,6480:903;Doi:https:/doi.Org/10.1126/science.aba1416.Theapproachisreminiscentoftheoriginalstickytapeexperimentsthatledtothefirstproductionofgraphene,madebypeelingoffamonolayerfromapencilmarkonaglassslide.Theareaspossiblewiththisnewlyreportedgoldtapeexfoliationare,however,approximatelyamilliontimeslarger.Theteamexplainsthattheycanassemblethemonolayersintomacroscopicartificialstructures.Thesestructuresareinaccessiblethroughconventionalbulkcrystalgrowth.Forinstance,theycanproducelayersofmolybdenumdisulfidethatarealignedwitheachother.Theresultingstackslackmirrorsymmetryandsodemonstratestronglynonlinearopticalresponses.Inthatparticularexample,thematerialabsorbsredlightandemitsultravioletlightthroughsecond-harmonicgeneration."ThisapproachtakesUSonestepclosertomassproductionofmacroscopicmono-layersandbulk-likeartilicialmaterialswithcontrollableproperties/explainsoneoftheprincipalinvestigatorsonthework,JamesHone.Theworkrepresentsanewwaytoscaleuptheproductionof2DmaterialsthathasnotbeenpossiblewithconventionalapproachessofarwherethinfiImgrowthhasvariouslimitationsintermsofmaterialquality,reproducibility,andtherequirementforhightemperatures.Otherteamshaveusedgoldtoexfoliatelarge2