The preparation of metal-polymer composite materials using ultrasound radiation
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The preparation of metal-polymer composite materials using ultrasound radiation Shlomit Wizel, Ruslan Prozorov, Yair Cohen, Doron Aurbach, Shlomo Margel, and Aharon Gedanken Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel (Received 25 March 1997; accepted 3 June 1997)
Ultrasound radiation is used to prepare a composite material made of polymethylacrylate and amorphous iron nanoparticles. Two preparation methods are described, in which the monomer, methylacrylate, is the starting material. The magnetic properties of the composite material are measured and reveal a superparamagnetic behavior.
I. INTRODUCTION
The propagation of ultrasound waves through a fluid causes the formation of cavitation bubbles.1 The collapse of these bubbles, described as an implosion in the hot-spot theory, is the origin of extreme local conditions: high temperatures (5000–25000 K) and high pressures (1000 atm).1 The cooling rates obtained during the collapse are greater than 107 Kys.2,3 These high cooling rates have been utilized by Suslick and his coworkers in sonicating Fe(CO)5 as a neat liquid or in solution,2,3 where amorphous iron nanoparticles were the sole reaction products. Suslick et al. have also prepared amorphous Co4 and an amorphous Fe–Co alloy.5 Following Suslick’s method, we have reported on being able to control the particle size of the amorphous iron nanoparticles by varying the concentration of Fe(CO)5 in its solution.6 We have also prepared amorphous Ni7 and amorphous Fe2 O3 ,8 all having nanometer size particles. The application of high intensity ultrasound radiation in polymer chemistry has been an active research area.9,10,11 Most of the published work in this area has been concerned with the degradation of the polymer, where its molecular weight is reduced by sonication in dilute solutions.10 The first polymerization reaction synthesis using ultrasound radiation was that of acrylonitrile in aqueous solution.12 Two groups, Kruus and his co-workers and Price and his coworkers, have published most of the work in this field. Kruus has studied the polymerization of nitrobenzene,13 methyl methacrylate,14,15 bromobenzene,15 isoprene,15 and styrene,15,16 while Price’s favorite molecule has been methyl methacrylate.17,18 The preparation of polymer films containing dispersed metallic clusters or metallic colloids has been of great interest,19–25 because of both its practical and fundamental importance. Griffiths25 claims that the potential use of colloidal iron dispersions in polymers lies in magnetic recording devices and pigments. The application of polymers containing dispersed metallic clusters to catalysis was the motivation for all the electrochemical J. Mater. Res., Vol. 13, No. 1, Jan 1998
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studies.19–24 Apart from their useful catalytic activity toward technologically important substrates, they provide unique opportunities for exploring novel types of catalyst-support interactions. The two main
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