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1、CapillaryBridgesandCapillary-BridgeForces469Chapter11inthebook:P.A.KralchevskyandK.Nagayama,“ParticlesatFluidInterfacesandMembranes”(AttachmentofColloidParticlesandProteinstoInterfacesandFormationofTwo-DimensionalArrays)Elsevier,Amsterdam,2001;pp.469-502
2、.CHAPTER11CAPILLARYBRIDGESANDCAPILLARY-BRIDGEFORCESTheimportanceofcapillarybridgeshasbeenrecognizedformanysystemsandphenomenalikeconsolidationofgranulesandsoils,wettingofpowders,capillarycondensationandbridgingintheatomic-force-microscopemeasurements,etc
3、.Thecapillarybridgeforceisorientednormallytotheplaneofthethree-phasecontactlineandconsistsofcontributionsfromthecapillarypressureandsurfacetension.Thetoroid(circle)approximationcanbeappliedtoquantifytheshapeofcapillarybridgesandthecapillary-bridgeforce.M
4、orereliableresultscanbeobtainedusingtheexactprofileofthecapillarybridge,whichisdeterminedbythePlateausequenceofshapes:(1)nodoidwith“neck”,(2)catenoid,(3)unduloidwith“neck”,(4)cylinder,(5)unduloidwith“haunch”,(6)sphereand(7)nodoidwith“haunch”.Fortheshapes
5、(1-5)thecapillary-bridgeforceisattractive,itiszeroforsphere(6)andrepulsiveforthenodoid(7).Equationsconnectingtheradiusoftheneck/haunchwiththecontactangleandradiusarederived.Theproceduresforshapecalculationsareoutlinedforthecasesofbridgesbetweenaplaneanda
6、naxisymmetricbody,andbetweentwoparallelplanes.Intheasymptoticcase,inwhichthecontactanglebelongstotherange70<c<90,theellipticintegralsreducetoelementaryalgebraicfunctionsandthecapillarybridgecanbedescribedintermsofthetoroidapproximation.Someuppergeomet
7、ricalandphysicalstabilitylimitsforthelengthofthecapillarybridgesareconsidered;thelattercanbeestablishedbyanalysisofdiagramsofvolumevs.pressure.Attentionispaidalsotothethermodynamicsofnucleationofcapillarybridgesbetweentwosolidsurfaces.Twoplane-parallelpl
8、atesareconsideredasanexample.Thetreatmentissimilarforliquid-in-gasbridgesbetweentwohydrophilicplatesandforgas-in-liquidbridgesbetweentwohydrophobicplates.Nucleationofcapillarybridgesispossiblewhenthedistancebetweentheplate