《纳米复合材料-英文版-05.pdf》由会员分享，可在线阅读，更多相关《纳米复合材料-英文版-05.pdf（33页珍藏版）》请在三一文库上搜索。
1、2011/2/13 1 Characterisation of Nanofillers and Nanocomposites 1 MECH548 Department of Mechanical Engineering Hong Kong University of Science d distance of atomic planes; m order of diffraction. CB=BD=ABsin CBD=2ABsin 6 AB interplanar spacing (d) CBD multiple of the X-rays wavelength for in- phased
2、diffracted rays. 2011/2/13 4 Information from WAXD Immiscible (no d-spacing change) Decomposed/deintercalated (d-spacing decrease) Intercalated (d-spacing increase) Exfoliated (d-spacing outside of WAXD/Disordered signal) 7 WAXD/Disordered signal) Factors Affecting WAXD Measurement Sampling (power v
3、s. solids, alignment of clay platelets)platelets) Experimental parameters (slit width, count time, angle step rate) Crystalline order of the nanoparticles (disordered/amorphous materials show no pattern by WAXD) 8 WAXD can only measure the atomic plane spacing, but not overall (global) dispersion of
4、 the nanoparticles in the sample 2011/2/13 5 WAXD Study of Clay 4000 1wt% I30P 2.38 nm 0 1000 2000 3000 2345678910 2(degree) Intensity 3wt% I30P 5wt% I30P I30P Powder 4.4 nm Disappearance of peak 9 Complete disappearance of (001) basal plane after curing, suggesting satisfactory dispersion (interlay
5、er distance: 2.38 nm ? 4.4 nm) with a mixture of full intercalation and exfoliation Scanning Electron Microscope (1/3) A microscope that uses electronsuses electrons rather than light to form an image. Key advantages: Large depth of field Images of high 10 Images of high resolution Relatively simple
6、 in sample preparation JEOL-6700F SEM Ultra-high resolution Scanning Electron Microscope 2011/2/13 6 Scanning Electron Microscope (2/3) Beam of electrons is generated in the electron gun This beam is attracted through the anode, condensed by a condenseranode, condensed by a condenser lens, and focus
7、ed as a very fine point on the sample by the objective lens. The scan coils are energized (by varying the voltage produced by the scan generator) and create a magnetic field which deflects the beam back and forth in a controlled pattern. 11 p The electron beam hits the sample, producing secondary el
8、ectrons from the sample. These electrons are collected by a secondary detector or a backscatter detector, converted to a voltage, and amplified and form the topography of the sample. Scanning Electron Microscope (3/3) 12 Although all these signals are present in any SEM study, not all of them are us
9、ed for information. The most commonly used signals are the Secondary Electrons, the Backscattered Electrons (topographical) and X-rays (compositions). 2011/2/13 7 SEM images of Graphite Natural graphiteGIC 13 Expanded graphite SEM Images of GNP 14 Expanded graphiteGNP 2011/2/13 8 6000060000 80000 10
10、0000 s 80000 100000 s 12000 16000 12000 16000 ts 0.34nm 0.34nm WAXD Study of GNP 0 20000 40000 0 20000 40000 6000060000 0102030405001020304050 Degree CountCount 0 4000 8000 01020304050 0 4000 8000 01020304050 Degree Count GIC GNP The distance between the graphene layers remains 15 The distance betwe
11、en the graphene layers remains the same before and after formation of GNP, suggesting that the GNP consists of multilayer graphenes. Transmission Electron Microscopy (TEM) One of the methods for direct imaging of individual nanoparticles. Transmission electron microscopyTransmission electron microsc
12、opy (TEM) is an imaging technique whereby a beam of electrons is transmitted through a specimen, then an image is formed, magnified and directed to appear either on a fluorescent screen or layer of photographic film, or to be detected by a sensor such as a CCD camera. 16 CCD camera. Provides real sp
13、ace image on the interfaces, structure and atomic distribution of materials. Also possible in providing chemical information at a spatial resolution of 1nm or better to identify the chemistry of a single nanocrystal. JEOL 2010F TEM Analytical Transmission Electron Microscope (TEM), Lattice resolutio
14、n = 0.102 nm, Field Emission Gun, EDS, Electron Energy Loss Spectrometer (EELS), MSC CCD Camera 2011/2/13 9 Sample Preparation of TEM Critical in determining the g quality of TEM picture. Specimen has to be thin enough to be transparent to the electron beam. Clean without 17 Clean, without much dama
15、ge or contamination. TEM of Clay Dispersion With sonicationWithout sonication 18 Sonication improved significantly the dispersion of clay aggregates within epoxy matrix. A mixture of full intercalation and exfoliation of organoclay with d-spacing about 8 nm. 2011/2/13 10 TEM of Carbon Nanotubes SEM
16、19 TEM of Functionalized CNT ? Endohedral: Capillary effect between guest atoms or molecules and CNTCNT 20 CNT filled with C60 moleculesCNT filled with Ag atoms * Smith Ammine: CH4N, -C2H6N and -C3H8N; Amide: -C3H6NO (-CH2CH2-CO-NH2). Comparisons Amongst Various Techniques (1/3) 32 2011/2/13 17 Comp
17、arisons Amongst Various Techniques (2/3) 33 Comparisons Amongst Various Techniques (3/3) 34 2011/2/13 18 Raman Spectroscopy When light is scattered from a molecule most photons are elastically scattered. The scattered photons have the same energy (frequency) and, therefore, wavelength, as the incide
18、nt photons. However, a small fraction of light ,g (approximately 1 in 107photons) is scattered at optical frequencies different from, and usually lower than, the frequency of the incident photons. The process leading to this inelastic scatter is the termed the Raman effect. Raman scattering can occu
19、r with a change in vibrational, rotational or electronic energy of a molecule. Chemists are concerned primarily with the vibrational Raman effect. (Raman fftibtil Rfft) 35 effect = vibrational Raman effect). The difference in energy between the incident photon and the Raman scattered photon is equal
20、 to the energy of a vibration of the scattering molecule. A plot of intensity of scattered light versus energy difference is a Raman spectrum. Provides info on non-polar groups. Renishaw MicroRaman / Photoluminescence System A B Structure Analysis of CNT by Raman Spectroscopy Raman spectra of differ
21、ent CNTs (A: CNTs milled without NH4HCO3; B: CNTs milled with NH4HCO3) Two major peaks of CNTs: 1570 cm-1: G band graphitic structure in CNTs 36 Intensity ratios of ID/IG 1570 cm-1: G band, graphitic structure in CNTs 1340 cm-1: D band, impurities or ill-structured graphite ID/IG ratios: Both the sa
22、mples increased with milling time, confirming progressive creation of new defects onto CNTs and disordered carbon. More pronounced ratio for CNTs milled with NH4HCO3 2011/2/13 19 Fourier Transform Infrared Spectroscopy Molecule may absorb infrared radiation of the appropriate frequency to excite it
23、from one vibrational or rotational ll tthlevel to another. FT-IR measures the absorption spectra which characterize the particular molecular and its molecular motions. Identify unknown chemicals by matching spectra with 37 by matching spectra with known database. Better for polar compounds. Better s
24、ensitivity and more comprehensive catalogs of IR spectra when compared with Raman. Bio-Rad UMA500 Surface Functionalities of MWNTs FT-ir Analysis (1) After UV/O3treatment, peaks at 1174, 1570,peaks at 1174, 1570, 1660, 1716 and 3100- 3400 cm-1 corresponding to C=O, O-H and C-O bonds in COOH function
25、al groups started to 38 groups started to appear, and their presence became clearer with increasing the exposure time 2011/2/13 20 Surface Functionalities of MWNTs FT-ir Analysis (2) Amino-terminated amide derivatives Untreated CNT amine were noticed after 30 mins of UV/O3 treatment followed by the
26、TETA treatment It appears that the previous carboxylic Absorbance Untreated CNT TETA treated CNT N-H stretching amine hydroxyl 39 previous carboxylic functional groups due to the UV/O3 treatment reacted with the amine functional groups in TETA 6001600260036004600 Wavenumber, cm-1 After UV/O3treatmen
27、t for 30 min followed by amino-functionalization with TETA Particle Size Analysis (1/5) Typically based on theories of light scattering (particle ttii titlscattering intensity angular pattern) to measure the particle size. Based on the refractive indices of sample and medium, under the specified wav
28、elength and polarization of the light, BkCltLS 2 Si 40 polarization of the light, particles of different sizes have different angular patterns. Beckman Coulter LS 2 Series Measuring range: 0.04 - 2000 m laser particle size 2011/2/13 21 Particle Size Analysis (2/5) Large particles: scattering intensi
29、ty is 41 gpgy stronger at small angles. Small particles: weaker scattering intensity and more evenly distributed over a broad angular range Particle Size Analysis (3/5) 42 Scattering Pattern of Spheres 2011/2/13 22 Particle Size Analysis (4/5) CNT/epoxy Nanocomposites ConditionDispersion method AAs
30、received CNTs + epoxyAAs-received CNTs + epoxy shear mixing for 30min at 3000rpm BCNTs dispersed by sonication for 1h in acetone + epoxy sonication for 2h at 60oC CUV/O3treatment of CNT for 1h and sonication for 2h in acetone + epoxy shear mixing for 30min at 3000rpm 43 DCNTs were ball milled for 2
31、h, sonicated in toluene for 1h and UV/O3treated for 2 h, followed by silane treatment +epoxy sonicated for 2h at 60oC 13692.4m 34.713.5m Particle Size Analysis (5/5) Average Agglomerate Size 0.290.1m 0.110.1m A (Shear Mixing only)B (Sonication in acetone (b) DSC. Differential Scanning Calorimetry (D
32、SC) & Differential Thermal Analysis (DTA) -2/2 Stress Tm othermic Heat Flow Tg Relief Ordering Cold Crystallization Curing Degradation Start up Transient endo ermic 50 Temperature Process exoth 2011/2/13 26 Thermogravimetric Analyzer (TGA) -1/2 A quantitative measurement of any weight changes associ
33、ated with thermally induced transitions, e.g. dehydration or decomposition. Changes in weight result from physical and chemical bonds forming 51 chemical bonds forming and breaking at elevated temperatures. Thermogravimetric Analyzer (TGA) -2/2 52 2011/2/13 27 To provide measurements of penetration,
34、 expansion, contraction, and tifti l Thermomechanical Analysis (TMA) -1/2 Measuring probe extension of materials as a function of temperature. High resolution load, displacement and temperature control system. Direct measurements of dimensional changes of Measuring probe Sample Sample temperature se
35、nsor Sample support Schematic drawing on CTE measurement 53 dimensional changes of cured resin with temperature to determine the CTEs. Thermomechanical Analysis (TMA) -2/2 54 2011/2/13 28 Dynamic Mechanical Analysis (DMA) -1/2 Perkin Elmer Pyris 7e Schematic drawing of the DMA 55 Designed to charact
36、erize the viscoelastic properties of polymer High sensitivity in load, displacement and temperature measurements. Dynamic Mechanical Analysis (DMA) -2/2 T or Tg (6)(6) For purely crystalline materials, no Tgoccurs. ( (5 5) ) (4)(4) E/Pa Rubbery Plateau (2) Rubbery plateau is related to M between cro
37、sslinks or For thermosets, no Tmoccurs. Beta transitions are often related to the toughness. Tg is related to Molecular mass up to a limiting value. In semicrystalline polymers, a crystal-crystal slip, T* occurs. Tllin some ( )( ) (4)(4) (3)(3) 56 Temperature /K Tm - melting (1) (6)(5)(4)(3)(2)(1) (
38、5)(4)(3)(2)(1) localbendsidegradual largechain motions andgroupsmainscaleslippage stretchchainchain to Mebetween crosslinks or entanglements. ll amorphous polymers 2011/2/13 29 Summary of Various Thermal Analysis Techniques DSC Heat flow vs. Temp - Tm, Tc, Tg - H, curing time, curing degree - Reacti
39、on rate, kinetics TGAWeight Loss vs. Temp - Decomposition temperature - %Wt percentage - Oxidative time TMADimensional Change vs. Temp - CTE ( 1, 2) T 57 - Tg - Softening point DMAViscoelastic property vs. Temp -Storage/Loss/Complex Modulus (E, E”, E*) - tan - Viscosity and master curve Contact Angl
40、e Measurement To demonstrate the relationship between the properties and chemistry of aproperties and chemistry of a surface: Wettability (ability of a fluid to cover a surface) varies with both the completeness of the monolayer and its degree of order. Wettability also varies with the polarity of t
41、he monolayer surface functional groups 58 surface functional groups. To determine the surface free energy of the monolayers by measuring contact angles as a function of surface tension of a series of liquids. Automatic contact measuring machine 2011/2/13 30 C-mode Scanning Acoustic Microscope (C-SAM
42、) C-mode Scanning Acoustic Microscope (C-SAM) C-SAM is used to define the exact nature of internal defects An acoustic lens generates a focused acoustic pulse into the sample, and return echoes are produced at the sample surface and at specific interfaces within the sample. 59 Frequency of 10-300MHz
43、 60 2011/2/13 31 Imaging Modes 61 62 2011/2/13 32 Transducer & Focusing UHF Connector Backing Material (Epoxy) Transducer Element (Piezo Electric Crystal) 63 Focused Aperture (Acoustic Lens) Crack Propagation Profile under SAM Study 64 2011/2/13 33 65 Concluding Remarks It is always important to und
44、erstand the basic working mechanisms and expectedbasic working mechanisms and expected results of various measuring techniques in order to facilitate the measurements and proper result interpretation as well as to increase the creditability of the results. Proper sample preparation is also the 66 Proper sample preparation is also the fundamental in obtaining reliable results, and determining the success of the entire experiments.