Nanocomposites analysis methods

HREM methods are powerful in the study of nanometre-sized metal particles dispersed on ceramic oxides or any other suitable substrate. In many catalytic processes employing supported metallic catalysts, it has been established that the catalytic properties of some structure-sensitive catalysts are enhanced with a decrease in particle size. For example, the rate of CO decomposition on Pd/mica is shown to increase five-fold when the Pd particle sizes are reduced from 5 to 2 nm. A similar size dependence has been observed for Ni/mica. It is, therefore, necessary to observe the particles at very high resolution, coupled with a small-probe high-precision micro- or nanocomposition analysis and micro- or nanodiffraction where possible. Advanced FE-(S)TEM instruments are particularly effective for composition analysis and diffraction on the nanoscale. ED patterns from particles of diameter of 1 nm or less are now possible. 

Recently, Ahmadi et al. [320] prepared EPDM/clay nanocomposites with organoclay that was intercalated with MA-grafted EPDM (MA-g-EPDM) and EPDM-clay composites with pristine clay via indirect melt intercalation method. Authors characterized the dispersion of the silicate layers in the EPDM matrix by XRD and TEM analysis methods. They showed that the particles of organoclay were completely exfoliated in EPDM matrix, and the mechanical, thermal, and chemical properties of nanocomposites were significantly improved compared with conventional composites. 

The produced fibres were examined using SEM/EDS (Nova NanoSEM, FEI) method in order to determine morphology and distribution of the nanofillers. Changes in the materials structure caused by the presence of the nanofiller were assessed on the basis of thermal analysis methods (DSC/TG, STA 449F3, Netzsch). The measurements were performed in nitrogen atmosphere with temperature ramp 10 deg/min up to 600°C. The method was used to examine both the fibres and the prepared polymer foils. Comparison between results of the thermal analysis of the polymer foils and the electrospun fibres allowed to asses the influence of the forming method on structure of the nanocomposite material. 

Numerous nanocomposite characterization methods are available thermogravimetric analysis (TGA), differential scanning calorimetry [DSC], transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), nuclear magnetic resonance (NMR), IR spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, dielectric relaxation spectroscopy, atomic force microscopy [AFM], electron spin resonance, continuous-wave and pulsed ESR spectroscopy and others [59]. Among all of the methods, TGA, DSC, wide-angle scattering diffraction [WAXS], and TEM are the most commonty used and will be discussed in detail. 

The incorporation of unmodified and organically modified montmorillonite nanoclays (namely 15A and 30B) in chlorinated polyethylene (CPE) by the solution intercalation method and their influence on mechanical properties of the nanocomposites have been studied by Kar et al. [137]. The o-MMT-embedded nanocomposites show enhanced tensile strength and Young s modulus in comparison to the nanocomposites containing the unmodified nanoclay. They have shown from and XRD analyses that organically modified clay shows better dispersion in the CPE matrix. This has been further substantiated from FTIR analysis, which proves an interaction between the CPE matrix and the clay intercalates. 

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. 

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