10物性分析與微觀成像技術(shù)

1、10 物性分析與微觀成像技術(shù)激光粒度儀Scanning Electron Microscopy (SEM)Scanning Electron Microscopy (SEM)分辨率一般為2-6nm，最高可達0.5nm；場深大、三百倍于光學顯微鏡；放大倍數(shù)可達20-100 0000 倍；樣品座為3-5mm，大的樣品座為30-50mm，樣品高度一般在 5-10mm。Transmission Electron Microscope (TEM)Transmission Electron Microscope (TEM)透射電鏡的分辨率為0.1-0.2nm，放大倍數(shù)為幾萬-幾十萬倍。由于電子易散射或被物

2、體吸收，故穿透力低，必須制備更薄的超薄切片（通常為50-100nm）。透過樣品后的電子束撞擊到熒光屏上，由電能轉(zhuǎn)變成光能，形成了濃淡不同的圖像。confocal laser scanning microscopy(CLSM)共聚焦光學系統(tǒng)中，只有與焦點重合的圖象會被輸出，光斑、無用的散亂光都被屏蔽掉了。分辨力約是普通光學顯微鏡的3倍。 奶酪中脂肪球融化過程A：25，B：50；C：70BLG凝膠過程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(xiàn)：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臺掃描隧道顯微鏡( scanning tunneling microscope ,STM), 1986 年,Binnig 和Rohrer 被授予諾貝爾物理學獎。衍生出一系列掃瞄探針顯微鏡（Scanning Probe microscope）STM 的探針是由針尖與樣品之間的隧道電流的變化決定的, STM要求樣品表面能夠?qū)щ姡荒苤苯佑^察導體和半導體的表面結(jié)構(gòu)。

5、 對于非導電的物質(zhì)則要求樣品覆蓋一層導電薄膜，但導電薄膜的粒度和均勻性難以保證，且掩蓋了物質(zhì)表面的細節(jié)。將原子線度的極細探針和被研究物質(zhì)的表面作為兩個電極，當樣品與針尖的距離非常接近 (通常小于1nm) 時，在外加電場的作用下，電子會穿過兩個電極之間的勢壘流向另一電極。Atomic Force Microscopy隧道電流強度對針尖和樣品之間的距離有著指數(shù)依賴關(guān)系，當距離減小0.1nm，隧道電流即增加約一個數(shù)量級。因此，根據(jù)隧道電流的變化，我們可以得到樣品表面微小的高低起伏變化的信息，如果同時對x-y方向進行掃描，就可以直接得到三維的樣品表面形貌圖，這就是掃描隧道顯微鏡的工作原理。掃描隧道顯微

6、鏡主要有兩種工作模式：恒電流模式和恒高度模式。 Atomic Force MicroscopyAtomic Force Microscopy接觸式 以斥力為主，探針與材料表面僅幾納米。對于柔軟表面有損傷的可能。非接觸式 以吸力為主，探針與材料表面有十幾納米，適用于柔軟材料。敲擊式 探針以一定頻率敲擊材料表面，降低了側(cè)向力對材料表面的影響，是柔軟材料首選模式。Atomic Force Microscopy直接獲取樣品表面圖像（3D），分辨率可達納米級； 光學1000倍，電子顯微鏡100萬倍，原子力10億倍。 圖像檢測可在空氣中或者液體中，可實時獲取生物材料和化學反應真實過程； 可檢測其他力：附著

7、力，磁力，摩擦力等機械特性。掃描速度慢，面積小。Atomic Force MicroscopyAtomic Force MicroscopyAtomic Force MicroscopyAtomic Force Microscopy （AFM）羅格斯大學Rutgers UniversityAtomic Force Microscopy黃桃表面黃桃水溶性果膠黃桃堿溶性果膠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.量熱法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應用示例DSC應用示例淀粉糊化溫度與水分關(guān)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）同時發(fā)現(xiàn)核磁共振（NMR）現(xiàn)象，1952年獲諾貝爾獎。 Griffiths et al. (1981)獲人類腫瘤圖譜。 Lauterbur (1973) 獲2D和3D圖像，稱為 MRI。質(zhì)子旋轉(zhuǎn)產(chǎn)生磁場Ma

20、gnetic Resonance ImageMagnetic Resonance Image脈沖使縱向磁力消失橫向磁力感應出信號中斷脈沖Magnetic Resonance ImageT1曲線（自旋晶格松弛）Magnetic Resonance Image橫向松弛Magnetic Resonance ImageT2曲線（自旋自旋松弛）Magnetic Resonance ImageT1 and T2核磁共振NMRI把生物材料放在磁場中；發(fā)射無線電波；關(guān)閉無線電波；生物材料發(fā)射信號，檢測并成圖像。Magnetic Resonance Image原子核是帶電的自旋體。具有奇數(shù)質(zhì)子和中子的原子核，具

21、有磁矩。氫核具有磁矩，這是檢測生物體的先決條件。磁場強度是靈敏度和分辨率的關(guān)鍵：永久磁鐵、電磁鐵、低溫超導磁鐵等。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