Metal oxide-polymer composites

To solve the problem of poor adhesion between fiber mats and the substrate, Kim et al. (2006) introduced an additional hot-pressing step after titania fiber deposition. Besides improving adhesion, this treatment was found to have an impact on the microstracture of the fibers as shown in Fig. 2.11. The as-spun metal oxide-polymer composite fibers exhibit a range of diameters from 200 to 500 nm (Fig. 2.11a). When calcined without hot-pressing to remove the organic vehicle, a bundle structure composed of sheaths of 200-500 mn diameters was obtained. In some cases, the outer sheaths were broken, revealing cores filled with 10-nm-thick fibrils as shown in Fig. 2.11c. By introducing the... 

The metal oxides prepared by conventional baking or by the CVD method are, in general, chemically stable, crystalline materials, and show excellent mechanical, electrical, optical, and physical properties. Flexible porous gel films obtained by the surface sol-gel process are totally different. In this chapter, we described a new preparative method for ultrathin metal oxide films by stepwise adsorption of various metal alkoxides. We named this method the surface sol-gel process. Structural characterization of the gel films thus obtained, the electrical property, and formation of nano-composites with organic compounds, were also explained. The soft porous gel contains many active hydroxyl groups at the surface and interior of the film. This facilitates adsorption of organic compounds, and consequent preparation of ultrathin metal oxide/polymer nano-composite films and organization of functional small molecules. In the nano-composites, proper selection of polymer components leads to the design of new materials with unique electrical, optical, and chemi-... 

Electrodeposition is a unique, versatile technique for fabrication of metal oxide, polymer, and composite electrodes for electrochemical supercapacitors. Composition, crystal structure, and morphology of the deposits can be easily manipulated by adjusting the electrodeposition parameters to achieve improved capacitive behavior. Current progress, however, is far from the commercial expectations for electrochemical supercapacitors. 

Thin-film metal (metal oxide)/polymer nanocomposites with different inorganic phase contents were obtained by using the cold-wall vacuum co-deposition technique. A range of metals was shown to be applicable to form nanocomposite thin films with PPX, i.e., Al, Ti, Pd, and Sn. AFM studies show the metal nanoparticles to have a size of 7-50 nm. Within the composite the polymer forms more or less spherical globules with a maximum size of about 200 nm. The interfacial regions between neighbouring polymeric spherulites contain nanoparticles of the inorganic filler. 

Figure 21.5 Strategies for understanding nanomaterial enviromnental health and safely, toxicity and biological response include nanomaterial classihcalion, that is, compositional classification (metal, metal oxide, polymer, senticonductor, carbon-based, etc.) for a material that has one dimension between 1 and 100 mn chentical composition in terms of bulk and surface size considerations, primary and secondary (aggregate) sizes and geometric structure which includes shape and porosity.

System Metal-Oxide-Polymer-Humid Air Usually, at atmospheric conditions reactive metals are covered with a thin native metal oxide. Consequently, the real polymer-metal interface consists of an interfacial inorganic nonmetallic layer, which influences the reactivity of the composite system. In this case, the Volta potential difference is given by Ref [150]... 

Friend, R.H., and Snailh, H.J. (2008) High efficiency composite metal oxide-polymer electroluminescent devices a morphological and material based investigation. Adv. Mater., 20, 3447—3452. 

There have been attempts to use metal oxide-CB composites for gas sensor design (Liou and Lin 2007). However, such an approach does not give any improvement in operating characteristics in comparison with conventional metal oxide or CB-polymer-based gas sensors. 

The incorporation of metals in polymers will not be covered in detail because only a limited number of reports exist on this subject. The major interactions that have been used for the incorporation of metals in polymers are those of ftmctional groups that form polymer-metal oxide-based composites. The incorporation of metals leads to dramatic changes in the properties of polymers, such as an increase of the glass-transition temperature Polybutadiene or polyisoprene incorporating palladium salts can imdergo crosslinking, mediated by palladium, between polymer... 

Surface analysis has made enormous contributions to the field of adhesion science. It enabled investigators to probe fundamental aspects of adhesion such as the composition of anodic oxides on metals, the surface composition of polymers that have been pretreated by etching, the nature of reactions occurring at the interface between a primer and a substrate or between a primer and an adhesive, and the orientation of molecules adsorbed onto substrates. Surface analysis has also enabled adhesion scientists to determine the mechanisms responsible for failure of adhesive bonds, especially after exposure to aggressive environments. The objective of this chapter is to review the principals of surface analysis techniques including attenuated total reflection (ATR) and reflection-absorption (RAIR) infrared spectroscopy. X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and secondary ion mass spectrometry (SIMS) and to present examples of the application of each technique to important problems in adhesion science. 

Strength, brittleness, and solvent permeability properties are limited because of lack of control of the ceramic composition on a macro- and microlevel. Even small particle sizes are large compared with the molecular level. There have been a number of attempts to produce uniform ceramic powders including the sol-gel synthesis in which processing involves a stable liquid medium, coprecipitation in which two or more ions are precipitated simultaneously. More recently, Carraher and Xu have used the thermal degradation of metal containing polymers to deposit metal atoms and oxides on a molecular level. 

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. 

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