Nanocomposites granulates

Fig 15.12 Schematic of silicon/carbon nanocomposite granule formation through hierarchical bottom-up assembly, (a-c). Annealed carbon-black dendritic particles (a) are coated by silicon nanoparticles (b) and then assembled into rigid spheres with open interconnected internal channels during C deposition (c) (Reprinted with permission from Magasinsld et al. [89]. Copyright 2010)... 

An alternative possibility is to include nanocomposite granulates in a polymeric matrix of a different composition, using compatibilizer to achieve acceptable properties. It should, however, be noted that nanocomposites with more than one type of polymer present may be more difficult to recycle, while maintaining high quality levels, than when one type of polymer is present [51,84]. 

Processes for preparing biodegradable thermoplastic nanocomposite granules comprise the following steps ... 

Thermogravimetric analysis (TGA) was performed on prue FPVC (unprocessed) and FPVC nanocomposite granulate (following extrasion) in air over a temperature range of 50-600 °C using a TGA 2950 (TA Instruments) at a scan rate of 10 °C/min. 

Shape of granules essentially affects the properties of granular metal. Concerning the nanocomposite structure, it is possible to outline fibrous and laminate composites together with grain nanocomposites, in which shape of granules is close to spherical. In fibrous composites, sizes of inclusions in... 

Value t — 2 for the granular metals has been confirmed experimentally in several papers (see, for example, Ref. [1]) however, for Nix(Si02)i A nanocomposite with granules of nanometer size it was found t x 2.7, g x 2 [65]. It rather essentially differs from the classical theory predictions. Also, the noticeable differences of the experimental values of critical indexes from the theoretical ones have been found in papers [66,67]. Authors of these papers attributed the discrepancy between the experimental data and results of the classical percolation theory to the quantum effects, which lead to the Anderson localization of charge carriers [57,58]. 

Let us notice, at last, that xc in the granular metals often essentially exceeds the values given by the classical percolation theory (0.2-0.3), and it appears M).5 0.6 [5,46,53,65]. This discrepancy is connected not to the quantum effects, but more likely with technological procedure of the nanocomposite preparation, by interaction between metallic granules and a... 

The galvanomagnetic properties of nanocomposites and their conductivity, in particular, near the percolation transition can be described within the two-component model developed for the case by Efros and Shklovskii [73] on the basis of Dykhne theory [74]. This theory was developed just for the description of materials containing two different components with sharp distinction for conductivity values (Dykhne media) and describes well the concentration dependence of the effective conductivity in the case of the classical grain sizes and so in the absence of quantum effects. However, even if quantum effects do not play an essential role, the adequate description of the conductivity dependence on temperature has not been elaborated till now. The reason is that numerous experimental results for granules, with the metal contents x[Pg.612]

Eq. (18) is usually attributed to the variable-range hopping conductivity in presence of the Coulomb gap [34]. However, the analysis [72,75,76] shows that it is unrealistic explanation for the case of nanocomposites, because to fit experimental value on the basis of this theory one has to assume that the length of a single hop is less than the size of granules D and the electron... 

Consideration of a system with widespread granule sizes shows that in the case when the temperature dependence of resistance of a nanocomposite is described by the —1/2 law, the characteristic temperature To oc X 3/2. The temperature dependence of the Hall resistance is described by the same law (see Eq. (18)) ... 

DSC measurements were performed on a TA Instruments 2190 DSC with temperature and enthalpy calibrations performed using an indium reference. Experiments were performed under a nitrogen atmosphere with a flow rate of 50ml/min. Extruded granules of nanocomposites were heated at 2°C/min to 250°C, held isothermally for 5mins, then cooled to room temperature at 2°C/min. All samples were heated twice, first to examine the properties post extrusion and secondly to examine the preferred crystal structures with slow cooling. 

In polypropylene-based nanocomposites the dispersion of clay will normally be done at speed varying between 30-80 rpm. The mixing time varies between 5-10 minutes. This helps in dispersing the clay particles and also facilitates the dispersion of clay as intercalated (or) fully dispersed clay platelets. Following this, the mixed blend may be pelletized into fine granules, so that it can be used as raw material for further component processing. Or else it can be injection molded directly to get components of required shape (or) size. 

This chapter reviews the general context of starch as a material. After a survey of the major sources of starch and their characteristic compositions in terms of amylase and amylopectin, the morphology of the granules and the techniques applied to disrupt them are critically examined. The use of starch for the production of polymeric materials covers the bulk of the chapter, including the major aspect of starch plasticization, the preparation and assessment of blends, the processing of thermoplastic starch (TPS), the problems associated with its degradation and the preparation of TPS composites and nanocomposites. The present and perspective applications of these biodegradable materials and the problems associated with their moisture sensitivity conclude this manuscript. 

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