Nanocomposites microscopy

This is a nonpolar rubber with very little unsamration. Nanoclays as well as nanotubes have been used to prepare nanocomposites of ethylene-propylene-diene monomer (EPDM) rubber. The work mostly covers the preparation and characterization of these nanocomposites. Different processing conditions, morphology, and mechanical properties have been smdied [61-64]. Acharya et al. [61] have prepared and characterized the EPDM-based organo-nanoclay composites by X-ray diffracto-gram (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy... 

FIGURE 2.8 Transmission electron microscopy (TEM) photographs of clay nanocomposites with acrylonitrile-butadiene rubber (NBR) having (a) 50% and (b) 19% acrylonitrile content, respectively... 

Tsou and Measmer examined the dispersion of organosUicates on two different butyl mbbers, namely BIMS and brominated poly(isobutylene-co-isoprene) (BIIR) with the help of small angle X-ray scattering (SAXS), wide angle X-ray scattering (WAXS), atomic force microscopy (AFM), and TEM [91]. There is also a patent on BIMS nanocomposites for low permeability and their uses in tire inner tubes [92]. 

Recent demands for polymeric materials request them to be multifunctional and high performance. Therefore, the research and development of composite materials have become more important because single-polymeric materials can never satisfy such requests. Especially, nanocomposite materials where nanoscale fillers are incorporated with polymeric materials draw much more attention, which accelerates the development of evaluation techniques that have nanometer-scale resolution." To date, transmission electron microscopy (TEM) has been widely used for this purpose, while the technique never catches mechanical information of such materials in general. The realization of much-higher-performance materials requires the evaluation technique that enables us to investigate morphological and mechanical properties at the same time. AFM must be an appropriate candidate because it has almost comparable resolution with TEM. Furthermore, mechanical properties can be readily obtained by AFM due to the fact that the sharp probe tip attached to soft cantilever directly touches the surface of materials in question. Therefore, many of polymer researchers have started to use this novel technique." In this section, we introduce the results using the method described in Section 21.3.3 on CB-reinforced NR. 

Wang, S.J., Cheng, G., Jiang, X.H., Li, Y.C., Huang, Y.B., and Du, Z.L. (2006) Direct observation of photoinduced charge redistribution of WCfi—Ti02 double layer nanocomposite films by photoassisted Kelvin force microscopy. Applied Physics Letters, 88 (21), 212108. 

Fig. 1.7 Representative EDS spectra of Na-montmoriUonite. Cu peaks arise from the TEM grid. Reprinted with permission from Yaron-Marcovich D, Chen Y, Nir S, Prost R (2005) High resolution electron microscopy (HRTEM) structural studies of organo-clay nanocomposites. Environ Sci Technol 39 1231-1239. Copyright 2005 American Chemical Society...

Gilman JW, Davis RD, BeUayer S et al. (2005) Use of optical probes and laser scanning con-focal fluorescence microscopy for high-throughput characterization of dispersion in polymer layered silicate nanocomposites. PMSE Prepr 92 168-169... 

Cuberes, M. T Assender, H. E Briggs, G. A. D., and Kolosov, O. V. (2000). Heterodyne force microscopy of PMMA/rubber nanocomposites nanomapping of viscoelastic response at ultrasonic frequencies. J. Phys. D Appl. Phys 33, 2347-55. [315]... 

Detailed HRTEM characterization of the specimens showed that all metal-ceramic interfaces in the two different nanocomposites had thin ( 1 nm thick) amorphous films (see Fig. 11.5). In addition, occluded particles were found inside the alumina grains which also had thin amorphous films at their interfaces with alumina. Analytical microscopy showed the films to contain Ca, Si, and Al.41 Hamaker coefficients were calculated for metal-ceramic interfaces in the presence of a Si02-based film, which indicated that a stronger attractive force is expected for intergranular films at metal-alumina interfaces,... 

Finally, the use of transmission electron microscopy (TEM) is of interest when dealing with the study of residual char obtained when MMT nanocomposites decompose. Figure 10.19 compares TEM images of an original PA6/clay sample with that of its residue collected at 17% sample mass... 

The dispersion morphology of prepared materials was studied with a multitechnique approach, by means of rheology, scanning electron microscopy (SEM), x-ray diffraction (XRD), and nuclear magnetic resonance (NMR). The results of these tests showed that the so formulated PA6 nanocomposites used in the present study are fully exfoliated [1,2],... 

Phase-contrast microscopy allows the calculation of the number of erythrocytes in various stages of damage namely discocytes, echinocytes, spherocytes and ghosts. This damage results from external factors causing injurious effects, and by the interaction with nanocomposites. 

The nanotubes were first oxidized in nitric acid before dispersion as the acidic groups on the sidewalls of the nanotubes can interact with the carbonate groups in the polycarbonate chains. To achieve nanocomposites, the oxidized nanotubes were dispersed in THF and were added to a separate solution of polycarbonate in THF. The suspension was then precipitated in methanol and the precipitated nanocomposite material was recovered by filtration. From the scanning electron microscopy investigation of the fracture surface of nanotubes, the authors observed a uniform distribution of the nanotubes in the polycarbonate matrix as shown in Figure 2.3 (19). 

Figure 2.3. Scanning electron microscopy image of the fracture surface of the polycarbonate nanocomposite. Reproduced from reference 19 with permission from American Chemical Society.

Keywords microstructure, microscopy, nanocomposites, properties, microscopic parameters, spectroscopy. 

CNT nanocomposites morphological and structural analysis is often done by TEM but an extensive imaging is required then to ensure a representative view of the material. Moreover, carbon based fillers have very low TEM contrast when embedded in a polymer matrix. The application of microscopy techniques is very useful to control the status of CNTs at any time during the preparation process of CNT/polymer nanocomposites, and moreover, to gain insights on parameters important for a better understanding the performance of the final nanocomposite material based on CNTs. 

Two specific imaging modes developed in combining ESEM (environmental scanning electron microscopy) and STEM and developed in the MATEIS laboratory can be useful for the characterization of CNT and CNT polymer nanocomposites. 

CNT nanocomposites, even at low CNT volume fractions, provided they form a percolating network. In such cases, it appears that SEM observations show not only the nanocomposite surface topology, but also the CNT arrangement near the surface within a thickness of even few pm. On the other hand, as for other electron microscopy methods, spectroscopy analysis can be used for imaging purposes. 

---