Nanostructured materials, enhanced properties

Both the discovery of new synthesis processes for nanostructured materials and the demonstration of the highly reactive properties of these materials have increased rapidly within recent years. The new synthesis processes have made available nanostructured materials in a wide variety of compositions of metal oxides and metals supported on metal oxides, which have led to recognition of their exceptional chemical, physical, and electronic properties. The objective of this review is to provide recent results on synthesis of nanostructured materials using the novel processes that were developed in these laboratories recently and to contrast them to other important, new methods. Because some of the most important applications of nanostructured materials are as catalysts for chemical processing, several key reports on enhanced catalytic reactivity of nanostructured grains will be discussed along with the pertinent theory responsible for controlling both activity and selectivity of these new catalysts. 

Furthermore, this technique allows variation of the grain size [30-33] this is important because many chemical and physical properties of nanostructured materials depend on the grain size. Only by variation of the crystallite size - this is a novd aspect in materials sdence and technology [34] - is it possible to tune and hopefully improve certain physical properties of one and the same material for example, the enhanced hardness of nano-Au, the toughness of nano-Ni/P alloys [35], the soft magnetic properties of nano-Ni [36] and the resistance of nanostructured materials [37, 38] promise industrial applications [39-41],... 

Successful separation of alkanes and alkenes has been documented when microporous membranes have been used [79,138]. The physiochemical properties, size, and shape of the molecules will play an important role for the separation, hence critical temperatures and gas molecule configurations should be carefully evaluated for the gases in mixture. On the basis of gas properties and process conditions, the separation may be performed according to selective surface flow or molecular sieving (refer to Section 4.2 on transport). The transport may also be enhanced by having a Ag compound in the membrane. The Ag ion will form a reversible complex with the alkene, and facilitated transport results. Selectivities in the range of 200-300 have been reported for separation of ethene-ethane and propene-propane [138]. Successful separation of alkanes and alkenes will be important for the petrochemical industry. Today the surplus hydrocarbons in the purge gas are usually flared. Membranes which should be suitable for this application are the carbon molecular sieves (see Section 4.3.2) and nanostructured materials (Section 4.3.3). 

A follow-up study demonstrated that Qi phases further enhance the performance of LLC-BR composite membranes in both water transport and harmful chemical vapor rejection [170]. A cross-linkable, gemini phospho-nium amphiphile (Fig. 23) was blended with BR and cross-linked to form films exhibiting a Qi-phase nanostructure. Materials with a Qi-phase showed 300 times greater water vapor permeability and 500 times greater permeability selectivity for water/CEES than pure cross-linked BR. Furthermore, these Qi-phase composite films were far superior to their Hu and L analogues in both water vapor permeability and water/CEES transport selectivity. Further studies were planned to process thinner films as well as test their rejection properties against other types of chemical agents. 

Nanocomposites are materials that are created by introducing nanostructured materials (often referred to as filler) into a macroscopic sample material (often referred to as matrix). After adding nanostructured materials to the matrix material, the resulting nanocomposite may exhibit drastically enhanced properties such as electrical and thermal conductivity, optical, dielectric and mechanical properties. 

Being in the nanotechnology era, novel nanostructured composite materials are expected to be designed showing improved properties due to nanostructuration. Moreover, composite electrodes from expensive metals (gold, platinum, etc.) can be prepared using the NPs as conductive fillers, with enhanced properties but at lower prices compared to their pure conductor counterparts. 

It is known that more highly conducting nanodomains exist within the essentially amorphous ICP host structure and that electrochemical switching speeds can be extremely rapid in nanowires composed of these materials. It is also known that control of nanotopography in other biomaterials can have a profound effect on the adhesion of mammalian cells. Given the explosion of activity in the area of ICP nanostructures, there is no doubt that these enhanced properties should translate into more effective biomolecular sensors and actuators. 

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