Synthesis of a KNbO 3 particle/polymer hybrid from metalorganics
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A nanocrystalline KNbO3 particle/polymer hybrid was synthesized through controlled hydrolysis and polymerization of metalorganics below 100 °C. A KNbO3 precursor was synthesized from potassium ethoxide, niobium ethoxide, and acetoacetoxyethyl methacrylate. The K–Nb alkoxide precursor was hydrolyzed and polymerized yielding KNbO3 particle/polymer hybrid. The organic matrix included nanometer-sized crystalline particles depending upon the hydrolysis conditions. The nanocrystalline particles were identified to be potassium niobate by electron diffraction and energy dispersive x-ray analysis. The suspension of the hybrid in silicone oil revealed a yield stress dependent upon various conditions, such as concentration and applied field. The hybridization was found to have a pronounced effect on the electrorheological properties of the fluid, including the KNbO3 particle/polymer hybrid.
I. INTRODUCTION
Inorganic/organic hybrid materials have been receiving growing attention because of their novel properties resulting from the synergetic effects based upon the merit of each phase.1–3 Inorganic/organic hybrids are classified into various types depending on their nanostructures between inorganic and organic phase, such as size, layers, and topology.4 The inorganic particle/organic hybrid is one of the particulate-dispersed hybrids, and reveals the size-dependent properties, such as superparamagnetism5 and quantum-size effect.6 The molecular design of the precursors with controlled chemical processing is a key for the synthesis of these materials. The uniform mixing of small magnetic or dielectric particles and polymers is quite difficult because the particles agglomerate during processing by magnetic moment and van der Waals force. Therefore, the in situ formation of magnetic or dielectric particles in a polymer matrix is one of the most advantageous methods for the synthesis of inorganic particle/organic hybrids. Magnetic particle/organic hybrids were successfully synthesized using a chelated iron-organic precursor.7 Iron spinel oxide particle/organic hybrid exhibited the superparamagnetism and quantum-size effect because of the nanosized magnetic particles.8,9 The authors synthesized BaTiO3 nanoparticle/organic hybrids from a designed
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Present address: Center for Integrated Research in Science and Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan. J. Mater. Res., Vol. 18, No. 7, Jul 2003
titanium-barium double alkoxide under controlled hydrolysis conditions below 100 °C.10,11 A nanocrystalline PbTiO3 particle/organic hybrid was synthesized from a lead-titanium organic modified with methacrylate group.12 The uniform formation of a nanocrystalline perovskite phase results from the controlled nucleation and growth, which is attributed to the reactivity of double metalorganic compounds. Electrorheological (ER) fluids are widely studied for various practical applications.13,14 The inorganic nanoparticle/polymer hybrid is a kind of composite particle and is a potential ER guest material for parti
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