No abstract

An improved resonator method is developed, which allows for a change in the resonator coupling coefficient at insertion of the sample during the measurement of the imaginary part of the material permittivity. The method makes it possible to measure small samples. The permittivity at a frequency of 27 GHz is measured for rods made of polycrystalline CVD diamond plates of 57 and 100 mm in diameter grown in the microwave plasma in methane−hydrogen mixtures, and the loss tangent tan δ is determined at a level of the order of 10 −3 .

Dielectric properties of biocompatible and biodegradable poly-ε-caprolone (PCL) and polylactide (PLA), as well as their nanocomposites, are measured in the millimeter (MM) wave band. It is found that the complex dielectric permittivity of PCL and its nanocomposites increases with temperature in the interval from 40 to 50℃, while that of PLA and its nanocomposites increases in the interval from 85 to 90℃. The samples of PLA with carbon nanotubes prepared with melamine show much lower absorption compared with the same samples prepared without melamine. The latter fact can be attributed to the formation of clusters of nanotubes in these samples.

No abstract

A new method is proposed to determine the content of alcohol in dielectric liquids. The method is based on measuring the attenuation of a wave propagating in a rectangular waveguide with a longitudinal slot in its narrow wall, immersed in a liquid under test. The propagation constant of the H 10 mode in such a waveguide is calculated numerically for various parameters of the medium and the waveguide. It is shown that the attenuation of the wave depends on the parameters of the dielectric medium outside the waveguide. Experiment is carried out on two different types of waveguide at frequencies from 29 to 37 GHz with a solution of ethyl alcohol in water as the external medium. The results of the measurements show that the method can be used for the on-line measurement of alcohol concentration during fermentation.