PNC (polymer nanocomposites) comprise very small particles typically having diameters less than 100 nm deposited on the surface of a support or within a host matrix. There exist several techniques to produce nanotubes since their discovery. The primary techniques currently available can be classified into the vaporisa-tion method (arc discharge and laser ablation) and the cata-lytic decomposition of hydrocarbons over metal catalysts alias the chemical vapour deposition method. Uniformly dispersed SWNT (single wall nanotubes) reinforced polyimide nanocomposites were e. g. synthesised by in situ polymerisation of monomers in the presence of sonification. Other methods comprise production of conducting polymer/C60 and a C60 doped conducting polymer/C60 heterojunctions nanoscale composite films by spin-coating or casting the solution containing both organic polymers and fullerenes. A patented PNC has been reported to absorb electromagnetic radiation in a range of 1000 Hz to 1017 Hz and therefore making it a potential aerospace candidate. Another PNC patent claims to be of high-use temperature, lightweight polymer/inorganic nanocomposite materials, having enhanced thermal stability and performance characteristics. Methods and materials for fabrication of alumoxane polymers and provided methods are described for the preparation of carboxylate-alumoxane / polymer composite and hybrid materials through the reactions of amine, hydroxyl, acrylic and vinyl substituted carboxylate-alumoxanes. Regarding MWNT (multiwalled nanotubes), one-way of uniformly dispersing MWNT into solutions of selected matrices is by using a high-energy ultrasonic probe. Another method of producing MWNT/polymer composites involves shear mixing followed by extrusion or injection moulding to fabricate artefacts in the required form. Regarding montmorillonite nanocomposites, polymer-clay nanocomposites have been prepared by four techniques; either through exfoliation-adsorption, in situ intercalative polymerisation, melt intercalation or template synthesis. Nylon-6 /montmorillonite nanocomposite as first polymer/clay composite consist of poly (caprolactone), polystyrene-polyisoprene block copolymers and polypropylene. Researchers interested on exploiting the unique polymeric materials of polyurethane such as non-toxicity, non-air polluter and flame-retardant, developed polyurethane/clay nanocomposite. Other researchers prepared montmorillonite and fluorohectorite clays from diprotonated forms of polyoxy-polypropylene diamines. Others synthesized organically modified layered alumosilicates using the sol-gel-process where the organic groups are incorporated into the molecular structure through the use of organically modified silicon alkoxides. Regarding carbon nanofibers and nanotubes, versatile methods for enabling their growth nanotubes include the use of laser etching, chemical vapour deposition, sol-gels, substrate supported catalysts and catalyst particles suspended as an aerosol. Laser ablation, first used for the production of fullerenes, has been developed over the years to produce both SWNT and MWNT. Its great advantage is the control of space and time of the various interaction processes taking place during evaporation. The Arc Discharge technique involves the use of two high-purity graphite rods as anode and cathode. Arc discharge was the first method available for the production of both MWNT and SWNT. Chemical vapour deposition of hydrocarbons over metal catalysts has been a classical method to produce carbon materials. The synthesis method of CNT using thermal chemical vapour deposition demands first the Fe, Ni, Co, or alloy of the tree catalytic metals be initially deposited on a substrate. Plasma CVD requires specialised plasma equipment but has an advantage of low temperature synthesis over thermal CVD as well as better control over length, diameter and structure of nanotubes. The vapour phase growth method has produced the highest level of SWNT occurring at around 1200 deg C and 10 atm by use of carbon monoxide as the carbon source. The vapour phase growth is a synthesis method that involves directly supplying reaction gas and catalytic metal in the chamber without a substrate. Flame synthesis of SWNT via a simple laboratory-scale diffusion flame is possible too. A metal nanoparticles catalyst formed from a metallocene lowers the energetic constraints for the formation of a CNT and hence acting as an effective interface between the gas-phase reactants and solid carbon precipitate. In flame synthesis method, combustion heat is a heating source of carbon nanotubes produced from combustion of CH4 in the small amount of oxygen atmosphere. MWNT and SWNT are synthesized by flowing hydrocarbon source like C2H2 and catalytic precursors in the diffusion flame atmosphere. Generally, further work is underway examining the characterisation methodologies and properties utilisation as to date for the PNC covered in the present work.


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    Titel :

    Polymer nanocomposites for aerospace applications: fabrication


    Weitere Titelangaben:

    Herstellung von Polymernanoverbundwerkstoffen für Anwendungen in der Luftfahrt


    Beteiligte:

    Erschienen in:

    Erscheinungsdatum :

    2004


    Format / Umfang :

    11 Seiten, 6 Bilder, 1 Tabelle, 83 Quellen




    Medientyp :

    Aufsatz (Zeitschrift)


    Format :

    Print


    Sprache :

    Englisch