Artificial dielectric properties of microscopic metallized filaments in composites

Abstract

Measurements have been made of the dielectric response of distributions of metallized fibers aligned in epoxy matrices for different loading fractions and fiber lengths. These have been shown to be in reasonable agreement with a simple independent particle theory. Use of the theory allows classification of fiber dielectric behavior by fiber conductivity and a characteristic length. Some aggregation of the fibers has been observed, even at relatively low loading densities. Computer simulation suggests enhanced dielectric constants of the composites for a moderate range of separations where the fibers are offset about 75% of their lengths with respect to each other and are closer than about 10 radii. This effect may be significant for aligned fibers which tend to aggregate in the magnetic field with separations and offsets within this range. The resulting composites are rugged and easily machined, and with less than 5% fiber weight loading have large, highly anisotropic dielectric constants of 60 or more at microwave frequencies in the X band. In conjunction with their (predicted) broadband performance characteristics such media should prove useful for a variety of applications.

Lipid Tubules: A Paradigm for Molecularly Engineered Structures

“…The results clearly demonstrated that the high aspect ratios of the metal cylinders led to high dielectric constants that were extremely anisotropic. Stockton et al (48) conducted further investigations over a wider range of concentrations and tubule lengths and also studied conventional fibers. Their results were in substantial agreement with those of Behroozi et al They demonstrated that the small diameter (~0 .…”

“…Metal-clad tubules could be one possible route to the fabrication of such composites. Stockton et al (48) and Behroozi et al (49) have fabricated and . This composite was then cast into rods and sheets.…”

Fabrication and radio frequency characterization of high dielectric loss tubule-based composites near percolation

“…Originally, these composites were designed to avoid percolation by minimizing contact between tubules. [10][11][12] The purpose was to produce artificial dielectrics with large real permittivities and low loss. By using magnetic orientation of ferromagnetically coated rods, random orientational contact between conductors was suppressed.…”

Dielectric Properties of Ceramic Composite with Nanosized Ni on Tubular Halloysite Template Under High Frequency

“…Studies have shown that particle conductivity has a great effect on the imaginary permittivity. 18 In general, the as-plated metal in electroless deposition has a lower conductivity than its bulk. 19 When the composite annealed at 400 C, Ni nanoparticles become complete crystallization, and they are in contact with each other due to their higher content in 80 wt% coaxial sample.…”