Metal particle-polymer composite materials

Recently, ultrafine metai particles have attracted much interest because of their unique properties which differ from those of buiK metals, e.g., quantum size effect, such as low melting point, plasmon resonance absorption and so an It is well known that ultrafine metal particles are quite active because of their large surface area and that they are liable to aggregate and grow in size. Thus, it is necessary to maintain them in stable form in a matrix for size control and tor narrow size distribution. Ultrafine metal partides-polymer composites, which are prepared by embedding ntetal particles in a polymer, can be used as electrical, magnetic, optical or chemically useful materials. The techniques to prepare ultrafine metal partides-polymer composites have been explored end reported by many researchers. Many of these involve co-evaporation or co-sputtering of a metal and polymer . In the case of thesb methods, however, metal-polymer composites have to be prepared at a rate below ca. 10 nm/min so that ultrafine metal particles will not... 

A composite material is a multiphase system composed of matrix material and dispersed material. The matrix material is usually a continuous phase, which consolidates the dispersion material such as fiber or particles. The composite material is commonly categorized into the class of materials that the matrix material belongs to metal matrix composites, inorganic nonmetal matrix composites, and polymer-based composites. For example, the metal matrix composite material is a material included in the scope of metallic materials, while the polymer matrix composite material is included in the scope of the polymer material. The inorganic whiskers filled and modified... 

The TEM is one of the most generally useful microscopes many thousands of them ate in daily use throughout the world. They ate appHcable to the study of ultrafine particles (eg, pigments abrasives and carbon blacks) as well as microtomed thin sections of plant and animal tissue, paper, polymers, composites of all kinds, foods, industrial materials, etc. Even metals can be thinned to sections thin enough for detailed examination. 

Note 6 Electric conductance of a nonconducting polymer can be achieved by dispersing conducting particles (e.g., metal, carbon black) in the polymer. The resulting materials are referred to as conducting polymer composites or solid polymer-electrolyte composites. 

Various metal and metal oxide nanoparticles have been prepared on polymer (sacrificial) templates, with the polymers subsequently removed. Synthesis of nanoparticles inside mesoporus materials such as MCM-41 is an illustrative template synthesis route. In this method, ions adsorbed into the pores can subsequently be oxidized or reduced to nanoparticulate materials (oxides or metals). Such composite materials are particularly attractive as supported catalysts. A classical example of the technique is deposition of 10 nm particles of NiO inside the pore structure of MCM-41 by impregnating the mesoporus material with an aqueous solution of nickel citrate followed by calicination of the composite at 450°C in air [68]. Successful synthesis of nanosized perovskites (ABO3) and spinels (AB2O4), such as LaMnOs and CuMn204, of high surface area have been demonstrated using a porous silica template [69]. 

Although a majority of these composite thermistors are based upon carbon black as the conductive filler, it is difficult to control in terms of particle size, distribution, and morphology. One alternative is to use transition metal oxides such as TiO, VO2, and V2O3 as the filler. An advantage of using a ceramic material is that it is possible to easily control critical parameters such as particle size and shape. Typical polymer matrix materials include poly(methyl methacrylate) PMMA, epoxy, silicone elastomer, polyurethane, polycarbonate, and polystyrene. 

Metal nanoparticles have also been included into MIPs. Such particles can be used, for example, as nanoantennae for the enhancement of electromagnetic waves (plasmonic enhancement). It has been shown by He et al. [122] that a thin layer (20-120 nm) of testosterone-imprinted silica could be synthesized around 350 nm silver particles in a controlled way. The composite material showed specific binding of the testosterone target. Matsui et al. [123] reported a molecularly imprinted polymer with immobilized Au nanoparticles as a sensing material for spectrometry. The sensing mechanism is based on the variable proximity of the Au nanoparticles... 

In general, polymers have low stiffness and strength in comparison with other materials, e.g., metals and ceramics, and consequently these materials present serious difficulties in structural applications. To improve their mechanical properties, polymers are reinforced by the addition of rigid particles or fibers to form composite materials (1). Thus, polymer matrix composite materials are made up of a low modulus phase, the polymer matrix, and a high modulus phase, the reinforcement, which is usually carbon or glass. The modulus of the composite is higher than that of the polymer matrix, and the increment is proportional to the volume fraction of the reinforcement. In general, the properties of the composite depend not... 

The particles in the air over an urban area are of a variety of sizes, shapes and chemical composition, ranging from tiny, spherical metal particles from metallurgical fumes to huge, porous conglomerates of sooty carbon, soil particles, fly ash, and fly dust of all types.The size and shape of the particles will almost totally determine the surface corrosion of polymers, plastics, the polymer in paints and lacquers. The important question is how these particles behave in the air, how far and how fast the wind carry them, and what effects they can have on polymeric materials. 

---