Nano effect

What makes metal nanoclusters scientifically so interesting The answer is that they, in many respects, no longer follow classical physical laws as all bulk materials do, but are correctly to be considered by means of quantum mechanics. This is not only valid for metals. In principle any other solid or in some cases even liquid material exhibit so-called nano-effects when reaching a critical size. Nanoscience and nanotechnology are based on those effects. In the course of only 1-2 decades nanosciences and nanotechnology have developed to such an extent that our daily life already is and will be increasingly influenced in a way that cannot be compared with any other technological development in mankind s history [2]. A few examples will help to better understand what is meant. 

In order to produce high-performance elastomeric materials, the incorporations of different types of nanoparticles such as layered silicates, layered double hydroxides, carbon nanotubes, and nanosilica into the elastomer matrix are now growing areas of rubber research. However, the reflection of the nano effect on the properties and performance can be realized only through a uniform and homogeneous good dispersion of filler particles in the rubber matrix. 

The SH(3 effect, which is on 25% greater than for reference (KTP-crystals) was observed. This data confirm significant contribution of nano-effects in the property improvement. 

Special attention has been focused on the flammability and fire stability of PLA needed during ironing. Solarski et al. [220] showed that the incorporation of 4 wt % organomodified layered silicate (Bentone 104) improves the shrinkage properties and reaction to fire of PLA filaments. They concluded that this nano effect" can be considered as permanent (i.e. the separated nanoplatelets are imbedded within the matrix), in contrast to some classical textile finishes, which are sensitive to washing. 

From Eq. (1.37) it follows, that the nanofiller particles (aggregates of particles) surface dimension d is the parameter, controlling the degree of reinforcement of the nanocomposites. From Eqs. (1.4)-(1.6) it follows unequivocally, that the value of ri is defined only by the size of the nanofiller particles (aggregates of particles) R. In turn, it follows from Eq. (1.37), that the degree of reinforcement of the elastomeric nanocomposites EJEJ is defined by the dimension <7 only, or by the size only. This means, that the reinforcement effect is controlled by the nanofiller particle (aggregates of particles) size only and this is the true nano-effect. 

Y. Liang, S. Omachinski, J. Logsdon, J.W. Cho, and Tie Lan, Nano-Effect in In Situ Nylon-6 Nanocomposites, Nanocor Inc, Technical Paper. http //www. nanocor.eom/tech papers/antec2001.asp... 

Grosby, A. J. and Lee, J.-Y. 2007. Polymer nanocomposites The "nano" effect on mechanical properties. Polymer Reviews 47 217-229. 

A.J. Crosby, J.Y. Lee, Polymer nanocomposites the nano effect on the mechanical properties, Polymer Reviews 47 (2007) 217. 

Nanofibers generally have a moderately higher tensile strength and modulus than the bulk or film material due to the inner orientation of polymer molecules. Figure 10.28 [111] shows the Tlmoduli of submicron fibers as a hyperbolic function of the fiber radius as a demonstration of the possibilities for the nanofibers. As fiber diameters are decreased below 300 nm, tensile properties also increase notably [110] and the nano-effect takes place. 

The use of nano-particles to enhance heat transfer is a recent phenomenon, although arguments remain as to how this is manifest, particularly in boiling heat transfer. Of course nano-particles may need to be ranoved from the stream at some point, necessitating good filtration. Some review papers on nano effects in heat transfer are included in Appendix 3. 

He, J.-H., Y.-Q. Wan, and L. Xu (2007b). Nano-effects, quantum-like properties in electrospun nanofibers. Chaos, Solitons Fractals 33(l) 26-37. 

Indirect band-gap materials exhibit no significant photoluminescence (PL) at room temperature. As a specific nano-effect the quantum confinement in semiconductor clusters induces visible room-temperature PL. Thus, nano-colloidal silicon, molybdenum sulfide, and pyrite shows intense luminescence. 

For systems in which the polymer and filler have an affinity for each other [strong adsorption], increases in the surface area/ volume ratio of the filler can result in large changes in the volume fraction of polymer that is henceforth considered to be "bound" to the filler interface. Many changes in physical phenomena related to the polymer chain dynamics, e.g., the glass transition temperature [Tg] and degrees and rates of polymer crystallization, could be drastically altered due to this bound layer. This has been referred to as the "nano-effect." ° In cases where Tg shifts are observed, the effect is somewhat similar to that reported for thin polymer films. The most important result of an increased bound-polymer layer is the consequent changes in mechanical properties of the final composite.i ... 

A well-accepted definition of nanocomposite material is that one of the phases has dimensions in the order of nanometers [51]. Roy et al. [52] present in their paper on alternative perspectives on nanocomposites a summary of features of particle properties when particle size decreases beyond a critical size. As dimensions reach nanoranges, interactions improve dramatically at the interfaces of phases, as do the effect of surface area/volume on the structure-property relationship of the material [53]. There is definite increase in the modulus of the material reinforced with composites, higher dimensional stability to thermal treatment, as well as enhanced barrier, membrane (conductive properties) and flame resistance. Thus, as Paul and Robeson [54] rightly put it, the synergistic advantage of nanoscale dimensions ( nano effect ) relative to larger-scale modifications is an important consideration ... 

By surveying the nanocomposites prepared so far, wear resisting polymer nanocomposites can be regarded as a successful example that brings the so-called nano-effect into full play. At a filler loading of less than 1%, the wear rate of the matrix was lowered by over thousands of times (Table 20.4). Similar enhancement due to the addition of small amounts of fillers is impossible to perceive in microcomposites. The developments in this aspect have broadened the application possibility of particulate composites and solved the dilemma arising from the contradiction between tribological performance improvement and processability deterioration, as often observed in microparticles filled composites. 

---