10物性分析与微观成像技术

1、10 物性分析与微观成像技术激光粒度仪Scanning Electron Microscopy (SEM)Scanning Electron Microscopy (SEM)分辨率一般为2-6nm，最高可达0.5nm；场深大、三百倍于光学显微镜；放大倍数可达20-100 0000 倍；样品座为3-5mm，大的样品座为30-50mm，样品高度一般在 5-10mm。Transmission Electron Microscope (TEM)Transmission Electron Microscope (TEM)透射电镜的分辨率为0.1-0.2nm，放大倍数为几万-几十万倍。由于电子易散射或被物

2、体吸收，故穿透力低，必须制备更薄的超薄切片（通常为50-100nm）。透过样品后的电子束撞击到荧光屏上，由电能转变成光能，形成了浓淡不同的图像。confocal laser scanning microscopy(CLSM)共聚焦光学系统中，只有与焦点重合的图象会被输出，光斑、无用的散乱光都被屏蔽掉了。分辨力约是普通光学显微镜的3倍。 奶酪中脂肪球融化过程A：25，B：50；C：70BLG凝胶过程D：pH2，50；E：pH2，70；F：pH2， 90；G：pH7，50；H：pH7，70；I： pH7， 90A，B：25 奶酪C，D：35奶酪E，F：90BLGX-ray microtomogra

3、phyThe X-ray microtomographic 1072 scanner is commercially available from Skyscan. It is a high-resolution system with a resolution up to 5 mm that can handle specimens up to 1 cm3. The technique provides three dimensional information regarding the density distribution within the sample. X-raya：5%WP

4、C，26%XWb：5%WPC，34%XWc：15%WPC，26%XWd：15%WPC，34%XWSEMAtomic Force Microscopy1982 年,Gerd Binnig 和Heinrich Rohrer 共同研制成功了第一台扫描隧道显微镜( scanning tunneling microscope ,STM), 1986 年,Binnig 和Rohrer 被授予诺贝尔物理学奖。衍生出一系列扫瞄探针显微镜（Scanning Probe microscope）STM 的探针是由针尖与样品之间的隧道电流的变化决定的, STM要求样品表面能够导电，只能直接观察导体和半导体的表面结构。

5、 对于非导电的物质则要求样品覆盖一层导电薄膜，但导电薄膜的粒度和均匀性难以保证，且掩盖了物质表面的细节。将原子线度的极细探针和被研究物质的表面作为两个电极，当样品与针尖的距离非常接近 (通常小于1nm) 时，在外加电场的作用下，电子会穿过两个电极之间的势垒流向另一电极。Atomic Force Microscopy隧道电流强度对针尖和样品之间的距离有着指数依赖关系，当距离减小0.1nm，隧道电流即增加约一个数量级。因此，根据隧道电流的变化，我们可以得到样品表面微小的高低起伏变化的信息，如果同时对x-y方向进行扫描，就可以直接得到三维的样品表面形貌图，这就是扫描隧道显微镜的工作原理。扫描隧道显微

6、镜主要有两种工作模式：恒电流模式和恒高度模式。 Atomic Force MicroscopyAtomic Force Microscopy接触式 以斥力为主，探针与材料表面仅几纳米。对于柔软表面有损伤的可能。非接触式 以吸力为主，探针与材料表面有十几纳米，适用于柔软材料。敲击式 探针以一定频率敲击材料表面，降低了侧向力对材料表面的影响，是柔软材料首选模式。Atomic Force Microscopy直接获取样品表面图像（3D），分辨率可达纳米级； 光学1000倍，电子显微镜100万倍，原子力10亿倍。 图像检测可在空气中或者液体中，可实时获取生物材料和化学反应真实过程； 可检测其他力：附着

7、力，磁力，摩擦力等机械特性。扫描速度慢，面积小。Atomic Force MicroscopyAtomic Force MicroscopyAtomic Force MicroscopyAtomic Force Microscopy （AFM）罗格斯大学Rutgers UniversityAtomic Force Microscopy黄桃表面黄桃水溶性果胶黄桃碱溶性果胶An excellent example for the use of AFM to relate changes in biopolymer architecture to changes in the material pr

8、operties is the ongoing work of the group from Shanghai Jiao Tong University 810. Their thorough study looked into the changes occurring in yellow peaches (Prunus persica L. Batsch.) stored under a controlled atmosphere. This project appears to systematically analyze the various pectin fractions in

9、the fruit, composed of water-soluble pectin (WSP), chelate-soluble pectin (CSP), and sodium carbonate-soluble pectin (SSP). Being a major cell wall component, the molecular structure of pectin is closely related to thephysical attributes of the higher plant it is composing.量热法Thermal analysis is mad

10、e up of various techniques for studying the thermal behaviour of materials. When a material is heated or cooled its structure and chemical composition undergo changes : fusion, melting, crystallization, oxidation, position, reaction, transition, expansion, sintering .To measure these various transfo

11、rmations the variation in different parameters is followed up as a function of the temperature.DIFFERENTIAL SCANNING CALORIMETRY (DSC)Differential scanning calorimetry is a technique determining the variation in the heat flow given out or taken in by a sample when it undergoes temperature scanning i

12、n a controlled atmosphere.With heating or cooling any transformation taking place in a material is panied by a exchange of heat ; DSC enables the temperature of this transformation to be determined and the heat from it to be quantified.DSCT-measuring systemDSCDSC In the absence of any discrete physi

13、cal or chemical transformations, the baseline signal, as at B above, is related to the heat capacity of the sample.DSC应用示例DSC应用示例淀粉糊化温度与水分关系DIFFERENTIAL THERMAL ANALYSIS (DTA)The DTA curve plots the DTA signal in microvolts on the Y-axis against the reference material temperature on the X-axis. If n

14、othing is occurring in the sample material and the reference material (the reference material has been carefully selected so no reactions or transitions occur throughout the test temperature range) , the heat will pass through both materials at the same rate and raise the temperature of both thermoc

15、ouple beads at the same rate. The difference between the two thermocouple temperatures is zero, so a flat line is generated.Comparing the DTA versus the DSCDTA DSC 1. Provides the same information as the DSC. 1. Provides the same information as the DTA. 2. Larger sample size - to insure sample homog

16、eneity. 2. Small sample size - ideal for polymers, petrochemicals, pharmaceuticals, etc. where sample homogeneity is not a concern. 3. Larger thermal mass furnaces to insure isothermal conditions for samples, slower sample turnaround. 3. Smaller thermal mass furnaces that provide rapid sample turnar

17、ound. 4. Less complicated system, and lower priced than the DSC. 4. More sophisticated, more complex, and more expensive. DSC and DTATHERMOGRAVIMETRY (TG)Thermal Gravimetric Analysis (TGA) is a simple analytical technique that measures the weight loss (or weight gain) of a material as a function of

18、temperature.TGTHERMOGRAVIMETRY (TG)Drying, structural water release, structural position, carbonate position, gas evolution, sulfur oxidation, fluoride oxidation, and re-hydration. THERMOMECHANICAL ANALYSIS (TMA)Thermomechanical analysis is a technique measuring the deformation of a sample under a n

19、on-oscillating stress when it undergoes temperature scanning in a controlled atmosphere. The stress may be compressive, tensile, torsional.TMATMATMATMATMAMagnetic Resonance ImageBloch和Purcell（1946）同时发现核磁共振（NMR）现象，1952年获诺贝尔奖。 Griffiths et al. (1981)获人类肿瘤图谱。 Lauterbur (1973) 获2D和3D图像，称为 MRI。质子旋转产生磁场Ma

20、gnetic Resonance ImageMagnetic Resonance Image脉冲使纵向磁力消失横向磁力感应出信号中断脉冲Magnetic Resonance ImageT1曲线（自旋晶格松弛）Magnetic Resonance Image横向松弛Magnetic Resonance ImageT2曲线（自旋自旋松弛）Magnetic Resonance ImageT1 and T2核磁共振NMRI把生物材料放在磁场中；发射无线电波；关闭无线电波；生物材料发射信号，检测并成图像。Magnetic Resonance Image原子核是带电的自旋体。具有奇数质子和中子的原子核，具

21、有磁矩。氢核具有磁矩，这是检测生物体的先决条件。磁场强度是灵敏度和分辨率的关键：永久磁铁、电磁铁、低温超导磁铁等。Magnetic Resonance ImageIn pure water, The T2 and T1 times are approximately the same, 2-3 seconds. In biological materials, the T2 time is considerably shorter than the T1 time.Fat: T1 Signal Intensity is high (whitish), T2 intermediate.Fibrous Tissue: T1 Signal Intensity is low, and T2 is also lo