Catalytic Synthesis of High Energy Density Nanocomposite Dielectric Materials (26136)
process affording homogeneously dispersed ceramic nanoparticles within the matrix of processable, high-strength polymers. The high energy density polymer-metal oxide composites provide effective high energy storage in capacitor and insulator applications.
ADVANTAGES: Polymer-metal oxide composite materials exhibiting excellent permittivities and high breakdown strength insulator properties in a readily processable matrix for high energy dielectric applications. The scaleable preparation promises cost effective manufacture.
SUMMARY: Future pulsed-power capacitors will require dielectric materials having very large energy densities, with operating voltages > 10 kV, and msec-µsec charge/discharge times with reliable operation near dielectric breakdown. The operating characteristics of current state-of-the-art pulsed power and power electronic capacitors, which utilize either ceramics or polymers as dielectric materials, fall significantly short of this goal. Nanocomposites combining inorganic constituents exhibiting high permittivity and polymer matrices with high breakdown strength, mechanical flexibility, and facile processability have been explored but not achieved all necessary performance requirements.
This invention utilizes in situ propylene polymerization using metallocene catalysts supported on ferroelectric oxide nanoparticles such as barium titanate (BaTiO3) or titanium dioxide (TiO2) to generate homogeneously dispersed ceramic nanoparticles within the matrix of a processable, high-strength polymer. Physical characterization established the nanoparticles to be uniformly dispersed in a highly isotactic polypropylene matrix. Representative electrical measurements reveal the nanocomposites to be excellent insulators with leakage current densities ~ 10-9-10-12 A/cm2, permittivities as high as 7.2, and breakdown strengths ~ 4 MV/cm. Energy densities of the nanocomposites are estimated to be as high as 11 J/cm3 comparable or exceeding values reported for ceramic, polymer and composite dielectrics. The reported properties are obtained at relatively low inorganic inclusion volume fractions. This novel utilization of in situ supported metallocene olefin polymerization to produce metal oxide-polymer nanocomposites affording respectable permittivities and high breakdown strengths promises a new family of dielectric materials for future high energy capacitor applications.
Tobin Marks, Neng Guo, Sara DiBenedetto, Mike Lanagan
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