简介:Tostudytheroom-temperaturestabledefectsinducedbyelectronirradiation,commercialborosilicateglasseswereirradiatedby1.2MeVelectronsandthenultraviolet(UV)opticalabsorption(OA)spectraweremeasured.Twocharacteristicbandswererevealedbeforeirradiation,andtheywereattributedtosilicondanglingbond(E’-center)andFe3+species,respectively.TheexistenceofFe3+wasconfirmedbyelectronparamagneticresonance(EPR)measurements.Afterirradiation,theabsorptionspectrarevealedirradiation-inducedchanges,whilethecontentofE’-centerdidnotchangeinthedeepultraviolet(DUV)region.TheslightlyreducedOAspectraat4.9eVwassupposedtotransformFe3+speciestoFe2+speciesandthistransformationleadstotheappearanceof4.3eVOAband.Bycalculatingintensityvariation,thetransformationofFewasestimatedtobeabout5%andtheopticalabsorptioncrosssectionofFe2+speciesiscalculatedtobe2.2timeslargerthanthatofFe3+species.Peroxylinkage(POL,≡Si–O–O–Si≡),whichresultsina3.7eVOAband,isspeculatednottobefromSi–ObondbreakbutfromSi–O–Bbond,Si–O–Albond,orSi–O–Nabondbreak.Theco-presencedefectwithPOLisprobablyresponsiblefor2.9-eVOAband.
简介:Itisimportanttoquantitativelyunderstandthemethaneadsorptionandtransportmechanismincoalforanevaluationofthereservesandforitsproductionforecast.Inthiswork,ablockcoalsamplewaschosentoperformtheCH4adsorptionexperimentsusingthegravimetricmethodattemperaturesof293.60K,311.26K,332.98Kand352.55Kandpressuresupto19MPa.TheexcessadsorptioncapacityofCH4indryblockanthraciteincreased,followedbyasequencedecreasewiththeincreasingpressure.Hightemperaturerestrainedthegrowthoftheexcessadsorptionduetothattheadsorptionisanintrinsicallyphysicalandexothermicprocess.Theexcessadsorptionpeakdecreasedslowlywiththeincreaseoftemperatureandintersectedatapressureofmorethan18MPa;meanwhile,thepressureattheexcessadsorptionpeakincreased.Theexistingcorrelationswereexaminedintermsofdensityratherthanpressure.TheDR+kcorrelation,withanaveragerelativedeviationof±0.51%,fittedourdatabetterthantheothers,withanaveragerelativedeviationofupto2.29%.ThetransportationcharacteristicsofCH4adsorptionwasalsoinvestigatedinthisstudy,includingtheadsorptionrateanddiffusioninblockcoal.Thekineticdatacouldbedescribedbyamodifieduniporemodel.Theadsorptionrateswerefoundtoexhibitdependenceonpressureandtemperatureatlowpressures,whilethecalculateddiffusivitiesexhibitedlittletemperaturedependence.Inaddition,thekineticcharacteristicswerecomparedbetweenCH4andCO2adsorptionontheblockcoal.TheexcessadsorptionratiosofCO2toCH4obtainedfromtheDR+kmodeldecreasedwiththeincreasingpressure.