DSC课件

DifferentialScanningCalorimetry(DSC)Theory&Applications差示扫描量热仪(DSC)DSC测量样品吸热和放热与温度或时间的关系吸热热流入样品，即样品吸收外界热量，为负值。放热热流出样品，即样品对外界放出热量，为正值。国际标准ISO11357-1:：DSC就是测量在程序控制温度下，输入到试样和参比物之间的功率差（dH/dt）与温度(T)的关系的一种技术。该热流差能反映样品随温度或时间变化所发生的焓变：样品吸收能量时，焓变为吸热；当样品释放能量时，焓变为放热。-0.4-0.3-0.2-0.10.00.1HeatFlow(W/g)0255075100125150Temperature(°C)ExoUpEndothermicHeatFlowHeatflowsintothesampleasaresultofeitherHeatcapacity(heating)GlassTransition(Tg)MeltingEvaporationOtherendothermicprocessesEndothermic-0.10.00.1HeatFlow(W/g)020406080100120140160Temperature(°C)ExoUpExothermicHeatFlowHeatflowsoutofthesampleasaresultofeitherHeatcapacity(cooling)CrystallizationCuringOxidationOtherexothermicprocessesExothermicDSC与DTA测定原理的不同DSC是在控制温度变化情况下，以温度（或时间）为横坐标，以样品与参比物间温差为零所需供给的热量为纵坐标所得的扫描曲线。DTA是测量T-T的关系，而DSC是保持T=0，测定H-T的关系。两者最大的差别是DTA只能定性或半定量，而DSC的结果可用于定量分析。DSC:WhatDSCCanTellYouGlassTransitions（玻璃化转变，Tg）MeltingandBoilingPoints（熔点和沸点）Crystallizationtimeandtemperature（结晶时间和温度）PercentCrystallinity（结晶度）Polymorphism（多种形态）HeatsofFusionandReactions（熔化和反应热）SpecificHeat（比热）Oxidative/ThermalStability（氧化/热稳定性）RateandDegreeofCure（固化速率和程度）ReactionKinetics（反应动力学）Purity（纯度）DSC:典型DSC转变温度热流-放热玻璃化转变结晶熔化交联(固化)氧化或分解热流型(HeatFlux)在给予样品和参比品相同的功率下，测定样品和参比品两端的温差T，然后根据热流方程，将T（温差）换算成Q（热量差）作为信号的输出。功率补偿型(PowerCompensation)在样品和参比品始终保持相同温度的条件下，测定为满足此条件样品和参比品两端所需的能量差，并直接作为信号Q（热量差）输出。调制热流型(ModulatedHeatFlux)在传统热流型DSC线性变温基础上，叠加一个正弦震荡温度程序，最后效果是可随热容变化同时测量热流量，利用傅立叶变换将热流量即时分解成热容成分动力学成分。1、DSC的基本原理FurnaceThermocouplesSampleReferencePlatinumAlloyPRTSensorPlatinumResistanceHeaterHeatSink热流型DSC功率补偿型DSCSample传统量热仪内部示意图精确的温度控制和测量更快的响应时间和冷却速度高分辨率基线稳定高灵敏度热流DSC炉子剖面图DynamicSampleChamberReferencePanSamplePanLidGasPurgeInletChromelDiscHeatingBlockChromelDiscAlumelWireChromelWireThermocoupleJunctionThermoelectricDisc(Constantan)热流式DSC-工作原理sfsssRTTQrfrrrRTTQrsQQQRsRrTfsTrsTsTrRrTTRTTQQQfrrsfssrs热流式DSC-工作原理假设:1,传感器绝对对称，Tfs=Tfr，Rs=Rr=R2,样品和参比端的热容相等Cpr-Cps3,样品和参比的加热速率永远相同4,样品盘及参比盘的质量（热容）相等5,样品盘、参比盘与传感器之间没有热阻或热阻相等RTRTTRTTTTRrTTRTTQQQrsfrrfssfrrsfssrsHeatFluxDSC:TheoreticalTMeasurementTToTpTr=ReferenceTemperatureTs=SampleTemperatureTo=OnsetofMeltTp=PeakofMeltTheoretically:To=TpTimeTemperatureActualHeatFluxData-4-20DeltaT/HeatFlow156.0156.5157.0157.5ReferenceTemperature(°C)156.0156.5157.0157.5SampleTemperature(°C)5.25.35.45.55.65.75.8Time(min)Sample:Indium+2°C/minSize:1.7900mgComment:MultipleHeatingandCoolingRatesDSCFile:\\...\TA\Data\DSC\Shick\Indium5.018Operator:CaulfieldRunDate:08-Sep-200616:51Instrument:DSCQ1000V9.6Build290ExoUpSlopeduetothermallagTViolationsofAssumptionsPanandcalorimeterheatcapacitiesareignored•Sampleandreferenceheatcapacitiesareassumedtobethesameandtoheatatthesamerate.•Ingeneralthesampleandreferencecalorimeterheatcapacitiesdonotmatchcontributingtonon-zeroemptyDSCheatflowratebaseline.•DuringtransitionsandMDSC®experimentsthesampleandreferenceheatingratesdifferandthemeasuredheatflowrateisincorrectbecausethesampleandreferencesensorandpanheatcapacitiesstoreorreleaseheatatdifferentrates.ExpandedPrincipleofOperationQ=Ts-Tr+A+B+CRThermalResistanceImbalanceThermalCapacitanceImbalanceHeatingRateImbalanceTfsTsRsTfrTrRrCsCrNotBeingMeasuredw/ConventionalDSCQ-SeriesDSCSchematicSample&ReferencePlatformsTzero™ThermocoupleConstantanBodyChromelWireChromelAreaDetectorConstantanWireChromelWireBaseSurfaceThinWallTubeSamplePlatformReferencePlatformQ-SeriesHeatFlowMeasurementTrTsRsCsCrRrToTfQ-SeriesDSCTheTzerothermocoupleprovidesanobjectivereferencepointsothatthosefactorspreviouslyassumedcanbedirectlymeasured.Tzero™HeatFlowMeasurementRsRrqsqrCsCrTrT0TsHeatFlowRateEquationsHeatFlowSensorModelThesampleandreferencecalorimeterthermalresistancesandheatcapacitiesobtainedfromTzerocalibrationareusedintheheatflowratemeasurements.rsTTTsTTT00dtdTCRTqsss0dtdTCRTTqrrr0DifferentialTemperaturesTzero®HeatFlowTermContributionsPrincipalheatflowprovidesmainheatflowsignalThermalresistanceandheatcapacityimbalancetermsimprovebaselineHeatingratedifferencetermimprovesresolutionandMDSCperformancedTdCddTCCRRTRTqrssrrsr110To技术的四相热流方程dTdCddTCCRRTRTqrssrrsr110基本热流热阻不平衡热容不平衡加热速率不平衡标准DSC的单项热流方程To技术提供的额外项T0及高级T0技术对DSC测量的改进：T0不需假设（Q200/Q100DSC):1,传感器绝对对称，Tfs=Tfr，Rs=Rr=R2,样品和参比端的热容相等Cpr-Cps3,样品和参比的加热速率永远相同高级To不需假设(Q2000/Q1000DSC)：4,样品盘及参比盘的质量（热容）性等5,样品盘、参比比盘与传感器之间没有热阻或热阻相等dTdCddTCCRRTRTqrssrrsr110BaselineBowImprovementSuperiorResolutiononaPharmaceuticalSampleAnalysisAdvancedTzero®Results6165697377Temperature(癈)-25-20-15-10-50HeatFlow(mW)AdvancedTzeroTzeroDSCConventionalDSCAdvancedTzeroDSC1.13mgDotriacontane10癈/minMDSC®测量什么?MDSC将热流分解成与变化的升温速率相关和不相关的两部分MDSC将变化的升温速率叠加在线性的升温速率上是为了测量与变化的升温速率相关的热流一般来讲,只有热容与熔融的变化与变化的升温速率相关.MDSC的可逆和不可逆信号绝不能样品可逆和不可逆性质的测量MDSC®原理MDSC®同时采用两种升温速率平均升温速率提供平均升温速率，它相当与普通标准DSC@在同样升温速率下的信号调制升温速率目的是为了在得到热流信号的同时得到热容的信号平均&调制温度信号调制温度平均温度Modulate+/-0.42°Cevery40secondsRamp4.00°C/minto290.00°C525456586062ModulatedTemperature(°C)525456586062Temperature(°C)13.013.514.014.515