Transmission electron microscopy nanocomposite

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... 

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. 

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... 

Intercalated and partially exfoliated PVC-clay nanocomposites were produced by melt blending in the presence and absence of DOP and characterised by X-ray diffraction and transmission electron microscopy. The effects of various factors, including volume fraction of clay, plasticiser content, melt compounding time and annealing, on nanocomposite structure and the thermal and mechanical properties of the nanocomposites were also examined. It was found that the best mechanical properties were achieved at 2% clay loading and 5 to 10% DOP loading. 18 refs. 

Other characterization methods, such as transmission electron microscopy, are necessary for a more complete evaluation of nanocomposite formation. In a similar case, copper hydroxy dodecyl sulfate, with a bilayer packing of anions was found to result in some nanocomposite formation when used in PVE (5). 

These are very intimate mixtures composed of two or more sohd phases that differ in composition and each with particle sizes of 10 to 20 mn. Solid phases of these dimensions produce sols when dispersed in a liquid. Two or more sols of different composition can be uniformly mixed and gelled to obtain compositionally different nanocomposites. Figure 13.1a shows the transmission electron microscopy (TEM) picture of a sol-gel nanocomposite of mulhte composition consisting of spherical sihca particles (20 nm) and rod-like alumina (boehmite) particles (approximately 7 nm). Such a uniform physical mixture can be distinguished from a homogeneous sol-gel material which does not show any nonuniformity because it is mixed on an atomic scale (Figure 13.1b). The compositionally... 

Hence, finite size effects on the optical response of metal nanoparticles are very difficult to take into account in an accurate manner. Moreover, in most experiments carried out on thin nanocomposite films or colloidal solutions the particle size distribution is not mono-dispersed but more or less broad, that can be usually determined by analysis of transmission electronic microscopy images. It should be underlined that the relevant quantity for smdying size effects in the optical response of such media can definitely not be the mean cluster radius , although it is often used in the literature [28-33], since the contribution of one nanoparticle to the optical response of the whole medium is proportional to its volume, i.e. to (cf. Eq. 7). The relevant quantity, that we call the optical mean radius , would then rather be the third-order momentum of the size distribution, = / ... 

The structure of the simple oxides and nanocomposites was characterised by means of X-ray diffraction (XRD), Transmission Electron Microscopy... 

Field emission scanning electron microscopy (FESEM), glancing incidence x-ray diffraction (GIXRD), transmission electron microscopy (TEM), micro Raman scattering, Fourier transform inftaied (FTIR) spectrometry, Rutherford back scattering (RBS) studies and electron probe micro analysis (EPMA) have been carried out to obtain micro-structural and compositional properties of the diamond/p-SiC nanocomposite films. Atomic force microscopy (AFM) and indentation studies have been carried out to obtain film properties on the tribological and mechanical front. 

The morphology of the nanocomposites was studied with Transmission Electron Microscopy (TEM JEM-2000 EX-11 at 200 kV). Samples for TEM were prepared by standard procedures, including separation of the nanocomposite layer from the NaCl substrate in water and the film deposition onto a Cu grid for further derailed investigations. The metal content of the composites was calculated by atomic absorption analysis using a Perkin-Elmer 503 spectrometer. 

For the comprehension of mechanisms involved in the appearance of novel properties in polymer-emhedded metal nanostructures, their characterization represents the fundamental starting point. The microstructural characterization of nanohllers and nanocomposite materials is performed mainly by transmission electron microscopy (TEM), large-angle X-ray diffraction (XRD), and optical spectroscopy (UV-Vis). These three techniques are very effective in determining particle morphology, crystal structure, composition, and particle size. 

Nanocomposites with EPDM have been compatibilized with EPDM-MA. The viscoelastic data resembled those observed for the styrene copolymers small changes in Tg and modulus [Li et al., 2004]. However, the effect of MMT-ODA on depended strongly on T In CPNC with 5 wt% organoclay at -100 °C, , while at 25°C it reaches a maximum value of 2.6, compared with Er= 1.4 at this temperature. According to x-ray diffraction and transmission electron microscopy the CPNC was exfoliated and dispersed uniformly. 

Botana et al. [50] have prepared polymer nanocomposites, based on a bacterial biodegradable thermoplastic polyester, PHB and two commercial montmorillonites [MMT], unmodified and modified by melt-blending technique at 165°C. PHB/Na and PHB/ C30B were characterized by differential scanning calorimetry [DSC], polarized optical microscopy [POM], X-ray diffraction [XRD], transmission electron microscopy [TEM], mechanical properties, and burning behavior. Intercalation/exfoliation observed by TEM and XRD was more pronounced for PHB30B than PHB/Na,... 

Mondragon et al. [250] used unmodified and modified natural mbber latex (uNRL and mNRL) to prepare thermoplastic starch/natural rubber/montmorillonite type clay (TPS/NR/Na+-MMT) nanocomposites by twin-screw extrusion. Transmission electron microscopy showed that clay nanoparticles were preferentially intercalated into the mbber phase. Elastic modulus and tensile strength of TPS/NR blends were dramatically improved as a result of mbber modification. Properties of blends were almost unaffected by the dispersion of the clay except for the TPS/ mNR blend loading 2 % MMT. This was attributed to the exfoliation of the MMT. 

The structures of nanocomposites have been characterized mainly by the techniques of X-Ray DiflEraction (XRD) and transmission electron microscopy (TEM). The TEM analysis gives qualitative information of the sample as a whole, helping to understand the internal structure, partial distribution of various phases... 

---