Nanoparticle-filled systems

Fig. 11 Dependence of the rate constant k on the temperature T for different systems Arrhenius plot of k measured in the presence of the composite particles SPB-30-Pd9 (filled squares, [Pd composites] = 0.00063 gL-1). In the case of the Microgel-1-Pd9 system (open squares, [Pd composites] = 0.00128 gL-1), we obtained an 5-curve that is similar to that of silver nanoparticles (filled circles, data taken from [59], [Ag composites] = 0.0063 gL-1). The concentrations of the reactants were [4-nitrophenol] = O.lmmolL-1 and [NaBIE] = lOmmolL-1 [24]...

Nanocomposites consist of a nanometer-scale phase in combination with another phase. While this section focuses on polymer nanocomposites, it is worth noting that other important materials can also be classed as nanocomposites—super-alloy turbine blades, for instance, and many sandwich structures in microelectronics. Dimensionality is one of the most basic classifications of a (nano)composite (Fig. 6.1). A nanoparticle-reinforced system exemplifies a zero-dimensional nanocomposite, while macroscopic particles produce a traditional filled polymer. Nanoflbers or nanowhiskers in a matrix constitute a one-dimensional nanocomposite, while large fibers give us the usual fiber composites. The two-dimensional case is based on individual layers of nanoscopic thickness embedded in a matrix, with larger layers giving rise to conventional flake-filled composites. Finally, an interpenetrating network is an example of a three-dimensional nanocomposite, while co-continuous polymer blends serve as an example of a macroscale counterpart. 

Fig. 10.38 Qualitative comparison between the theory and the experimental phase diagram (cloud points) for the PVA/PMMA polymer blend without fillers (filled diamonds) and with 10 wt% fumed silica (open squares). The two curves correspond to the spinodals calculated using equations. It is assumed that both PVA and PMMA had degrees of polymerization (N) 1,000 and that (pN) a + bT, with (a)-lO.O, (b) 0.026374. Finally, assumed that (F) 0.65. For the filled system, we took nanoparticle loading of 14 vol%, with the dimensionless particle radius (R) 20 (corresponding to the real- particle radius of 10 run) (Ginzburg 2005)...

Fiber-reinforced systems have been modeled with use of an MC method to place parallel fibers into a polymer matrix, with a finite element algorithm (FEA) then being used to compute elastic properties (274). A generic meshing algorithm for use in FEA studies of nanoparticle reinforcement of polymers has been developed (275) and applied to the calculation of mechanical properties of whisker and platelet filled systems. The method should be applicable to void-containing low dielectric materials of such great utility in the semiconductor industry. 

Fig. 15 T1O2 nanotubes in drug delivery system, (a) Magnetic nanoparticle filled nanotubes with attached drug (F) for magnetically guided site selective drug delivery. Release is triggered by photocatalytic chain scission upon UV irradiation. Inset an example where a blue fluorescent molecule is released from magnetically actuated nanotubes (reproduced with permission from Ref 276). (b) Amphiphilic nanotubes loaded with drugs or biomolecules which are released upon opening the hydrophobic cap with UV irradiation (reproduced with permission from Ref 202).

Similarly, a substantial decrease in the specific wear rate, w, can be observed in Si02-g-PAAM filled composites with the rise in filler content and all vv values are lower than those of untreated nano-SiOj-filled systems, although the untreated nanoparticles can also result in decreased w, with respect to the unfilled epoxy. Within the filler content range firom 2 to 6 vol.%, the wear resistance of epoxy is increased by a factor of about 20 by the addition of SiOj-g-PAAM. Bearing in mind the fact that 40 wt.% micron-sized SiOj (180 /tm) particles were needed to acquire a significant decrease in the wear rate of epoxy, the present systems are clearly characterized by a broader applicability. 

Once the particle sizes are diminished down to the nanoscale (< 100 nm), the wear performance of these nanocomposites differs significantly from that of micron particle-filled systems. Polymers filled with nanoparticles are recently under discussion because of some excellent properties they have shown under various testing conditions. Some results were achieved in various studies, suggesting that this method is also promising for new processing routes of wear resistant materials. For instance, Xue et al. found that various kinds of SiC particles, i.e., nano, micron and whisker, could reduce the friction and wear when incorporated into a PEEK matrix at a constant filler content, e.g., 10 wt.% ( 4 vol.%). However, nanoparticles resulted in the most effective reduction. Nanoparticles were observed to be of help to the formation of a thin, uniform, and tenacious transfer film, which led to this improvement. The variation of Zr02 nanoparticles from 10 to 100 nm was conducted by Wang et al. The results showed a similar trend as most of the micron particles, i.e., the smaller the particles, the better was the wear resistance of the composites. 

The functionalization of these particles is always required for preparing a PNC in fact nanoparticles have a strong tendency to agglomerate and, consequently, the so-called nanoparticle-filled polymers sometimes contain a number of loosened clusters of particles (Fig. 20.10a) and the final material exhibits properties even worse than conventional particle/polymer systems. 

Controlled cutting and opening of closed carbon systems Direct applications of CNTs (requires 20-100 nm in length) Inner filling and impregnation of CNTs with metal nanoparticles and complexes... 

Silica nanoparticles are a promising component of FR systems because of their effect on viscosity in the molten state and the potential ability to react with many other chemical compounds, particularly during degradation stages of filled polymers. 

Wu et al. [69] have combined microemulsion and inverse-micelle techniques with hydrothermal techniques in the preparation of rutile and anatase Ti02 nanoparticles. They used the system water-cyclohexane-Triton X-100 with n-hexanol as a second emulsifier. The water-filled micellar pockets were acidified (with HCl or HNO3) Ti(OR)4 (R = butyl). Treating the system at 120-200 °C for 12-144 h gave anatase particles. When high HCl concentrations were employed, rutile rods were obtained. 

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