Title of article :
Influence of AFM Tip Temperature on THF Hydrate Stability:Theoretical Model and Numerical Simulation
Author/Authors :
Xie, Jingyu Faculty of Engineering - China University of Geosciences - Wuhan 430074, China , Peng, Li Faculty of Engineering - China University of Geosciences - Wuhan 430074, China , Ning, Fulong Faculty of Engineering - China University of Geosciences - Wuhan 430074, China , Li, Wei Faculty of Engineering - China University of Geosciences - Wuhan 430074, China , Sun, Jiaxin Faculty of Engineering - China University of Geosciences - Wuhan 430074, China , Cao, Pinqiang Faculty of Engineering - China University of Geosciences - Wuhan 430074, China , Liu, Zhichao Faculty of Engineering - China University of Geosciences - Wuhan 430074, China
Abstract :
Atomicforcemicroscopy(AFM) indentationiswidelyusedtodeterminemechanicalparametersofvariousmaterials.However,AFMtipmayleadtophasetransitionofthecoldsampleintheregionofcontactarea.Itisalong-standingchallengethatlow-temperaturephase-changematerials (e.g.,iceandhydrate) arehardlycharacterizedbyAFM,especiallyforclathratehydrates. Here,withtheoreticalanalysisandnumericalsimulation,weinvestigatedthetemperatureinfluenceofAFMtiponthetetrahydrofuran(THF)hydratestability. Atfirst,asteady-statemodelofheatconductionwasestablishedbetweenav-shapedprobeandTHFhydratesample. Thetemperatureofthetipwasestimatedatdifferentlaserspotpositionsandlaserintensities.Throughnumericalsimulation,theheatlossbyairconvectionislessthan1%ofthetotallaserheat,andtheinfluenceofambientairontheAFMprobetemperaturecanbeneglected. Meanwhile,thelocaltemperatureintheregionofcontactareawasalsocalculatedattheTHFhydratetemperatureof0°C,-10°C,-20°C,and-30°C.WefoundoutthattheAFMtipcausesthecoldTHFhydratetomelt.ThethermalmeltingthicknessdecreaseswiththereductionoflaserintensityandTHFhydratetemperature .Onthecontrary,itispositivelycorrelatedwiththethicknessofliquid-likelayeronTHFhydratesurfaceandisalsolinearlyincreasedwiththecontactradius.Thisindicatesthatthethermalmeltingcontinuesasthepress-indepthofthetipintoTHFhydrateincreases. ThelocaltemperatureriseswhenthetiptouchestheTHFhydrate. ItiseasierforTHFhydratetobemeltedbyanexternalpressure.Inaddition,theproposedmodelmaybeusefulforguidingforcetestsonlow-temperaturephase-changematerialsbytheAFMindentation.
Keywords :
Influence , AFM Tip Temperature , THF Hydrate Stability , Theoretical Model , Numerical Simulation , Atomicforcemicroscopy(AFM)
