Nano materials preparation

Put simply, nanotechnology includes the aspects of preparation, property characterization, surface improvement, and application of nano materials. It involves many disciplines and its progress needs the cooperation of scientists and engineers from various disciplines. Obviously, among the aspects mentioned above, preparation of nano materials is the basis. If there was nano material preparation any other work related to nano materials would be meaningless, like a tree without roots. 

Alexandre, M. and Dubois, P. 2000. Polymer-layered silicate nano-composites preparation, properties and uses of a new class of materials. Materials Science and Engineering 28 1- 63. 

A review on using sonochemistry for the fabrication of nano-materials has been published by Gedanken (2004). It has been remarked that, in almost all the sono-chemical reactions leading to inorganic products, nano-materials were obtained and it was observed that, in the field of materials science, among the methods developed to prepare nano-particles, the sonochemical techniques are superior to the other methods in the following aspects ... 

In addition, materials prepared by anodization permit the growth of the oxide nanostructured film over a conductive substrate (Ti foil), an important aspect for preparation of robust electrodes. As discussed later, electrical contact with the conductive substrate could be further improved using carbon nano tubes. 

This chapter introduces investigations into the preparation of nano copper and its surface improvement together with the major results the preparation of the other two nano materials, Titania and hydroxyapatite, will be discussed in later chapters. 

Comparison is always of interest. Table 14.3 gives a comparison between the mean sizes of nano copper powders prepared with various technologies, different reaction agents and in various reactors. It appears that the SCISR has significant superiority for the preparation of nano materials by liquid reaction- precipitation. 

Surface improvement is a very important link between preparation and application of nano materials the specific method employed for the surface improvement is closely related to the occasion where the nano material is to be used. For nano copper powder the main problem is its easy oxidation, i.e., it has no anti-oxidation nature at room temperature. The partial replacement of Cu by Ag to transform the nano copper powder into the Cu-Ag double metal powder is one of the most feasible methods for the surface improvement of nano copper, because the nano Cu-Ag double metal can meet the requirement of anti-oxidation at room temperature also the latter can be used in the preparation of electro-conductive materials and electro-conductive rubbers etc. to replace some expensive metals such as silver and palladium. 

As for other inorganic nano materials, a number of preparation methods have been proposed for nano Titania. Because of its economic advantages and its simplicity, Li... 

In this chapter, we will focus on the automated preparation of CdSe quantum dots (which have been extensively studied and characterized in the scientific literature), but the principles and techniques we describe are general ones that may be applied to a variety of nanomaterials. Indeed, the following paragraphs outline some selected studies which have reported the use of microfluidic reactors for the synthesis of compound semiconductor nano materials. 

Thus, among various organic materials cellulose is the most appropriate for preparation of various types of nano-materials, since this most abundant semicrystalline polysaccharide has a nanostructured organization that promotes the isolation of free nanoconstituents such as nanofilaments, nanofibrils, crystalline, and ANP. 

The structural study of materials was always of a high priority, because the physical properties of materials depend very much on their structme. There are several levels of structural study, which start with the investigation of the morphology of the material surfaces, closely related to their in-plane ordering. Many nano-structured materials prepared with the help of layer-by-layer deposition techniques, such as LB or electrostatic self-assembly, have a distinctive periodicity in the direction normal to the surface, which determines their main electrical and optical properties. This is why the study of the layer-by-layer structure of such materials is of crucial importance. 

The ability of siloxane surfactants to stabilize different chemical reactions allows the preparation of different nano-materials. For example, gemini surfactants containing a siloxane moiety have been used as templates for the preparation of mesopoious metal oxides sueh as zirconium, titanium, and vanadium oxides. The siloxane segment seems to play an important nano-propping role during the surfactant removal by direct calcination [105]. 

Although siloxane surfactants and especially silicone polyethers are known and produced for some decades, they continue to incite the interest of the scientific world. New structures are emerging, new methods are used for their investigation and new applications are discovered. In particular, biocompatible surfactants are of great importance nowadays, as well as those obtained from renewable sources. Nano-materials may be prepared with siloxane-containing surfactants, which are active both in water and in organie media. 

Hsu K-F, Tsay S-Y, Hwang B-J. Synthesis and characterization of nano-sized LiFePO cathode materials prepared by a citric acid-based sol-gel route. J Mater Chem 2004 14 2690-5. 

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