2-压汞法测量孔分布原理

©2001,2002QuantachromeInstruments1压汞法孔隙度分析MercuryIntrusionPorosimetry©2001,2002QuantachromeInstrumentsAnalysisBasicTheory浸润/非浸润Wetting/Non-wetting接触角ContactAngleWashburn方程压力生成PressureGeneration体积的电容测量Capacitancemeasurementofvolume©2001,2002QuantachromeInstruments基本原理TheFundamentalPrinciple非浸润在颗粒之间的液态汞被压入孔中,被汞侵入的孔径是所加压力的函数.这个特性被用来表征广泛的微粒和固体材料.Theforcedintrusionofliquidmercurybetweenparticlesandintoporesasafunctionofappliedpressureisroutinelyemployedtocharacterizeawiderangeofparticulateandsolidmaterials.©2001,2002QuantachromeInstruments浸润/接触角Wetting/ContactAngles浸润90非浸润90©2001,2002QuantachromeInstrumentsContactAngle:HgonavarietyofmaterialsMaterialMeancontactangle(o)StandarddeviationDimethylglyoxime丁二酮肟139.60.45Galactose半乳糖140.30.43Bariumchromate铬酸钡140.60.41Titaniumoxide二氧化钛140.90.55Zincoxide氧化锌141.40.34Dodecylsodiumsulfate十二烷基硫酸钠141.50.44Antimonyoxide氧化锑141.60.88Fumaricacid富马酸143.10.27Starch淀粉147.20.68Carbon碳154.91.2©2001,2002QuantachromeInstruments毛细管现象Capillarity毛细上升Capillaryrise90毛细下降Capillarydepression90©2001,2002QuantachromeInstruments压汞法测量公式推导一种液体的表面张力是指液体表面一平方厘米所受到的力。当毛细孔的半径r和长度l给定，则单位体积水银的表面面积由下式决定：A=2πrl（1）假设毛细孔是钢性的，则毛细孔壁对水银的压力W1为：W1=-2πrlγcosθ（2）加大压力使水银进入毛细孔中，则外界对水银的压力W2为：W2=Pπr2l（3）因为W1=W2，所以由方程（2）和（3）可得：Pr=-2γcosθ（4）©2001,2002QuantachromeInstrumentsWashburn方程cos2Prm/N480140andr736.0PWherePisinMPaandrinµm©2001,2002QuantachromeInstrumentsWashburn方程它表明在θ和γ不变的前提下，随着压力的逐渐增大，水银将会逐渐进入孔径更小的孔。θ是汞对固体的接触角，γ是汞的表面张力。如果压力从P1改变到P2，分别对应孔径r1、r2，并设法量测出单位质量试样在两种孔径的孔之间的孔内所压入的汞体积△V，则在连续改变测孔压力时，就可测出汞进入不同孔级孔中的汞量，从而得到孔径分布。©2001,2002QuantachromeInstruments压汞法测试中能了解的信息WhatCanWeLearnFromMercuryIntrusion?孔体积Porevolume孔径分布Poresizedistribution孔面积PoreArea孔结构Porestructure粒度分布Particlesizedistribution©2001,2002QuantachromeInstruments孔体积测定范围最主要依赖于仪器的压力范围,但也依赖于接触角.Poresizerangedependspredominantlyontheinstrumentpressurerangebutalsoonthecontactangle.孔径上限受可得到的最低填充压力限制,而孔径下限则受最高填充压力限制.Thelargestporesizeislimitedbythelowestfillingpressureattainableandthesmallestporesizebythehighest.可测定粉末样品的粒度分布.Theparticlesizedistributionofpowderscanbedetermined.应用©2001,2002QuantachromeInstruments在压制和烧结过程的研究中压汞法是极其有用的分析工具.Mercuryintrusionisanextremelyusefulanalyticaltoolintheinvestigationofbothcompactionandsinteringprocesses.在一次测量中，能分析光纤、含纤维材料、织物及过滤介质的孔直径、渗透性和孔曲率.Fibers,fibrousmats,fabricsandfiltermediaingeneralcanbeanalyzedforporesize,fiberdiameter,permeabilityandtortuosityinasinglemeasurement.与汞能形成汞齐的材料不能用压汞法分析。Thosematerialsthatamalgamatewithmercurycannotbeanalyzed.应用©2001,2002QuantachromeInstruments压汞实验的必要条件ExperimentalRequirements样品管(膨胀计)Cell(penetrometer)toholdthetestsample.真空/填充装置,用于从样品管和样品的孔中去除空气并将汞转移进样品管.Vacuumfillingapparatustoremoveairfromthecellandporeswithinthesampleandfortransferringmercuryintothesamplecell.压力发生器.Pressuregenerator能容纳样品管的高压仓(高压腔).High-pressurevesseltocontainthesamplecell.测量电路:监测汞体积的改变,它是所用压力值的函数Measuringcircuitstomonitorchangeinmercuryvolumeasafunctionofappliedpressure.液压油:传导发生器产生的压力至样品管.Hydraulicfluidtotransmitthepressurefromthegeneratortothesamplecell.©2001,2002QuantachromeInstruments样品管SampleCell样品管或膨胀计:用来装样品,并便于注汞/排汞体积的测量.Thesamplecellorpenetrometer(sometimescalledadilatometer)isusedbothtocontainthesampleandtofacilitatethemeasurementofintrusionandextrusionvolumes.©2001,2002QuantachromeInstruments样品管SampleCell样品管或膨胀计:通过金属外套和电极帽(平板电极)进行注汞/排汞体积的测量.Thesamplecellorpenetrometerisusedbothtocontainthesampleandtofacilitatethemeasurementofintrusionandextrusionvolumesviametalsheathandelectrodecap.©2001,2002QuantachromeInstruments康塔公司样品管•Penetrometers(samplecells):onestyleaccommodatesbothpowdersandbulksolidsforreducedpenetrometerinventoryrequirements.Removablemetalsheathallowseasyviewingofpenetrometerstemtoconfirmproperfillandnopowderelutriation(fluidization).Macrocelloptionforcorecylindersupto2.5cmdiameterand3.5cmlong.FIGURE:POREMASTERSHORTSAMPLECELLASSEMBLYFORLOWPRESSUREMEASUREMENTSShortsamplecell(P/N74012)2mmID(P/N74014)4mmIDUpperCellHousing(shortcell)(P/N04000-6405)O-ring(P/N51001-112)CellcontactassemblyP/N01559©2001,2002QuantachromeInstruments压力Pressure注汞Intrusion©2001,2002QuantachromeInstruments实验综述ExperimentalOverview电容法测量体积Volumemeasurement–capacitancetechnique接触角Contactangle(130º-140º)样品管抽真空Samplecellevacuation(preventelutriation)汞填充Fillwithmercury低压注汞/排汞Lowpressureintrusion/extrusion转移至液压系统,排除空气Transfertohydraulicsystem,airpurge高压注汞/排汞(扫描或步进方式)Highpressureintrusion/extrusion(scanorstep)©2001,2002QuantachromeInstruments实验结果综述ResultsOverview©2001,2002QuantachromeInstruments压力值pressure体积变化Volumechange滞留entrapment可逆压缩(无迟滞或滞留)Reversiblecompression(nohysteresisorentrapment)内部孔的迟滞Hysteresisfrominternalpores颗粒间的空隙可能排出其中的汞,也可能不依赖于粉末压紧后的刚性Interparticlevoidsmaygiveuptheirmercuryornotdependingontherigidityofthepowder“compact”颗粒重排Particlerearrangement(大孔/空间largepores/spaces)(小孔/空间smallpores/spaces)曲线的总体观察GeneralObservationsSeegraphicalrepresentationnext…©2001,2002QuantachromeInstruments举例:三段式注汞曲线Example:3StagesofMercury“Intrusion”51015102510351045105PoreDiameter[nm]00.070.140.210.