Nanoparticles and Composites

In this chapter, the particles are divided into two subgroups sihca and metal oxide particles, because both systems have different challenges. In addition, the chapter is also divided in accordance with the preparation routes toward the nanopartides, namely, aqueous and nonaqueous sol-gel processes. For the implementation of the nanopartides into devices, it is often necessary to carry out a surface functionalization, which is also part of this chapter. In the concluding paragraphs, the effect of the thus formed particles on properties of nanocomposites has been discussed. 

The Sol-Gel Handbo Synthesis, Characterization, and Applications, First Edition. 

The aqueous sol-gel process is one of the most important processes employed for the production of oxide nanoparticles, particularly if particle redispersion in a solvent or surface functionalization is requested [1]. Generally, molecular compounds are hydrolyzed in an aqueous environment, the intermediates consisting of E—OH (E = semiconductor element or metal) groups are not stable under the given reaction conditions and condensation reactions occur. Thus, E—O—E bonds are formed and a three-dimensional network is also formed. 

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Simulation method of structural, quantitative and deformation properties of nanoparticles and composites based on them is offered. The model allows to study the dynamic characteristics nanoobjects throughout the life cycle of their use, starting from the processes of formation of nanoparticles and ending its influence on the mechanical parameters of the composite. 

Clusters are intennediates bridging the properties of the atoms and the bulk. They can be viewed as novel molecules, but different from ordinary molecules, in that they can have various compositions and multiple shapes. Bare clusters are usually quite reactive and unstable against aggregation and have to be studied in vacuum or inert matrices. Interest in clusters comes from a wide range of fields. Clusters are used as models to investigate surface and bulk properties [2]. Since most catalysts are dispersed metal particles [3], isolated clusters provide ideal systems to understand catalytic mechanisms. The versatility of their shapes and compositions make clusters novel molecular systems to extend our concept of chemical bonding, stmcture and dynamics. Stable clusters or passivated clusters can be used as building blocks for new materials or new electronic devices [4] and this aspect has now led to a whole new direction of research into nanoparticles and quantum dots (see chapter C2.17). As the size of electronic devices approaches ever smaller dimensions [5], the new chemical and physical properties of clusters will be relevant to the future of the electronics industry. 

The results of the mechanical properties can be explained on the basis of morphology. The scanning electron micrographs (SEM) of fractured samples of biocomposites at 40 phr loading are shown in figure. 3. It can be seen that all the bionanofillers are well dispersed into polymer matrix without much agglomeration. This is due to the better compatibility between the modified polysaccharides nanoparticles and the NR matrix (Fig. 4A and B). While in case of unmodified polysaccharides nanoparticles the reduction in size compensates for the hydrophilic nature (Fig. 3C and D). In case of CB composites (Fig. 3E) relatively coarse, two-phase morphology is seen. 

It is said that the 21st century is the age of nanotechnology since nanoparticles are applicable to an increasing number of areas. Therefore, this research field will occupy the much attention of scientists. Precisely controlling the primary size and structure of metallic nanoparticles, i.e., size, shape, crystal structure, and composition, however, is... 

Many different topics are involved in the study of metallic nanoparticles and many fundamental issues can be present for example, which is the infiuence of the nanoparticle size, shape and composition on the chemical activity of heterogeneous catalysts Or, considering another problem, at what size does a small particle behave like the bulk material, for example, changing from an insulator to a semiconductor [9-12] An enormous amount of literature is published on metallic nanoclusters this review is focusing on the relevant problem concerning the characterization of metallic nanosized materials from the morphological and... 

The recent liquid phase synthetic techniques provide us the metal nanoparticles with the standard deviation smaller than 10%. So a lot of scientists have been attracted by an investigation on the transition from molecular to bulk properties from both the fundamental and technological points of view. Here we present our recent liquid phase techniques to control the size and composition of Au and FePt nanoparticles. 

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