DSC培训课件.ppt
Differential Scanning Calorimetry (DSC)差示扫描量热仪差示扫描量热仪 (DSC)nDSC测量样品吸热和放热与温度或时间的关系测量样品吸热和放热与温度或时间的关系吸热吸热 热流入样品，即样品吸收外界热量，为负值。放热放热 热流出样品，即样品对外界放出热量，为正值。国际标准国际标准ISO 11357-1:： DSC就是测量在程序控制温度下，输入到试样和参比物之间就是测量在程序控制温度下，输入到试样和参比物之间的的功率差（功率差（dH/dt）与与温度温度(T)的关系的一种技术。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。吸收能量时，焓变为吸热；当样品释放能量时，焓变为放热。-0.4-0.3-0.2-0.10.00.1Heat Flow (W/g)0255075100125150Temperature (C)Exo UpEndothermic Heat FlowlHeat flows into the sample as a result of either lHeat capacity (heating) lGlass Transition (Tg)lMeltinglEvaporationlOther endothermic processesEndothermic-0.10.00.1Heat Flow (W/g)020406080100120140160Temperature (C)Exo UpExothermic Heat FlowlHeat flows out of the sample as a result of either lHeat capacity (cooling) lCrystallizationlCuringlOxidationlOther exothermic processesExothermicDSC与与DTA测定原理的不同测定原理的不同lDSCDSC是在控制温度变化情况下，以温度（或时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。需供给的热量为纵坐标所得的扫描曲线。lDTADTA是测量是测量 T-T T-T 的关系，而的关系，而DSCDSC是保持是保持 T = T = 0 0，测定测定 H-T H-T 的关系。两者最大的差别是的关系。两者最大的差别是DTADTA只能定性或半定量，而只能定性或半定量，而DSCDSC的结果可用于定量的结果可用于定量分析。分析。DSC: What DSC Can Tell YoulGlass Transitions（玻璃化转变，Tg）lMelting and Boiling Points（熔点和沸点）lCrystallization time and temperature（结晶时间和温度）lPercent Crystallinity（结晶度）lPolymorphism（多种形态）lHeats of Fusion and Reactions（熔化和反应热）lSpecific Heat（比热）lOxidative/Thermal Stability（氧化/热稳定性）lRate and Degree of Cure（固化速率和程度）lReaction Kinetics（反应动力学）lPurity（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 或分解热流型热流型(Heat Flux)(Heat Flux)在给予样品和参比品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相同的功率下，测定样品和参比品两端的温差温差 T T，然后根据热流方程，将然后根据热流方程，将 T T（温差）换算成（温差）换算成 Q Q（热量差）（热量差）作为信号的输出。作为信号的输出。功率补偿型功率补偿型(Power Compensation)(Power Compensation)在样品和参比品始终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件样品和参比品两端所需的能量差，并直接作为信号，并直接作为信号 Q Q（热量（热量差）差）输出。输出。调制热流型调制热流型(Modulated Heat Flux)(Modulated Heat Flux)在传统热流型在传统热流型DSCDSC线性变温基础上，叠加一个正弦震荡温度程序，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。热流量即时分解成热容成分动力学成分。1、DSC的基本原理的基本原理FurnaceThermocouplesSampleReferencePlatinum AlloyPRT SensorPlatinumResistance HeaterHeat Sink热流型热流型 DSC功率补偿型功率补偿型 DSCSample传统量热仪内部示意图传统量热仪内部示意图精确的温度控制和测量精确的温度控制和测量更快的响应时间和冷却速度更快的响应时间和冷却速度高分辨率高分辨率基线稳定基线稳定高灵敏度高灵敏度 热流热流DSC 炉子剖面图炉子剖面图Dynamic Sample ChamberReference PanSample PanLidGas Purge InletChromel DiscHeating BlockChromel DiscAlumel WireChromel WireThermocouple JunctionThermoelectric Disc (Constantan)热流式热流式 DSC - 工作原理工作原理sfsssRTTQrfrrrRTTQrsQQQRsRrTfsTrsTsTrRrTTRTTQQQfrrsfssrs热流式热流式 DSC - 工作原理工作原理假设假设: : 1, 1, 传感器绝对对称，传感器绝对对称，Tfs = TfrTfs = Tfr， Rs = Rr = R Rs = Rr = R2, 2, 样品和参比端的热容相等样品和参比端的热容相等Cpr-CpsCpr-Cps3, 3, 样品和参比的加热速率永远相同样品和参比的加热速率永远相同4, 4, 样品盘及参比盘的质量（热容）相等样品盘及参比盘的质量（热容）相等5, 5, 样品盘、参比盘与传感器之间没有热阻或热样品盘、参比盘与传感器之间没有热阻或热 阻相等阻相等 RTRTTRTTTTRrTTRTTQQQrsfrrfssfrrsfssrsHeat Flux DSC: Theoretical T MeasurementTrTsTToTpTr = Reference TemperatureTs = Sample TemperatureTo = Onset of MeltTp = Peak of MeltTheoretically: To = TpTimeTemperatureActual Heat Flux Data-4-20Delta T/Heat Flow156.0156.5157.0157.5Reference Temperature (C)156.0156.5157.0157.5SampleTemperature (C)5.25.35.45.55.65.75.8Time (min)Sample: Indium +2C/minSize: 1.7900 mgComment: Multiple Heating and Cooling RatesDSCFile: .TADataDSCShickIndium 5.018Operator: CaulfieldRun Date: 08-Sep-2006 16:51Instrument: DSC Q1000 V9.6 Build 290Exo UpSlope due to thermal lagTViolations of AssumptionsPan and calorimeter heat capacities are ignored Sample and reference heat capacities are assumed to be the same and to heat at the same rate. In general the sample and reference calorimeter heat capacities do not match contributing to non-zero empty DSC heat flow rate baseline. During transitions and MDSC experiments the sample and reference heating rates differ and the measured heat flow rate is incorrect because the sample and reference sensor and pan heat capacities store or release heat at different rates.Expanded Principle of Operation Q = Ts - Tr + A + B + C R ThermalResistance Imbalance ThermalCapacitance Imbalance Heating RateImbalanceTfsTsRsTfrTrRrCsCrNot Being Measured w/ Conventional DSCQ-Series DSC SchematicSample & Reference PlatformsTzero ThermocoupleConstantan BodyChromel WireChromel Area DetectorConstantan WireChromel WireBase SurfaceThin Wall TubeSample PlatformReference PlatformQ-Series Heat Flow MeasurementTrTsRsCsCrRrToTfQ-Series DSCThe Tzero thermocouple provides anobjective reference point so that thosefactors previously assumed can be directlymeasured.Tzero Heat Flow Measurement Rs Rr qs qr Cs Cr Tr T0 Ts Heat Flow Rate EquationsHeat FlowSensor ModelThe sample and reference calorimeter thermal resistances and heat capacities obtained from Tzero calibration are used in the heat flow rate measurements.rsTTTsTTT00dtdTCRTqsss0dtdTCRTTqrrr0Differential TemperaturesTzero Heat Flow Term ContributionslPrincipal heat flow provides main heat flow signallThermal resistance and heat capacity imbalance terms improve base
