V. N. Bovenko, R. Yu. Gerassimov

The results of experimental and theoretical researches of interaction of ultra-high frequency radio-waves with powder particles characterized by fractal structure, appeared in processing of fine jet grinding of granular mediums at supersonic speed of colliding of particle beams, are given. The researches were carried out in the range from 2,0 to 4,2 GHz on silicon carbide powders which the primary size of particles lie in range 4-5, 20-28 and 50-63 micrometers.. Test sample powders were located in the capacitive resonator, the induced radiation arising in it, arrived on the reception aerial of the broadband receiver which carried out a role of the spectrum analyzer. Resolution of the analyzer made 0,01-0,10 Hz. Changes of the form of registered signals, spectrum displacements in Stocks area of frequencies and the build-up of peak component of a spectrum with increasing of powder particle sizes were experimentally observed. All analyses of the peak-frequency characteristics of signal spectra started from assumptions of the excitation of Lemba resonator modes in the particles of granular medium and the fractal law of polymodal particle-size distribution. As a result the analytical dependence of the sensitivity of the spectrum displacements in relation to the changes of the primary sizes of particles was established. The high precision in the definition of frequency (10-9...10-10) has allowed to reach the sensitivity of spectrum displacement in the Stocks area of frequencies (5-6)?109 Hz/m = 5-6 Hz/nm. The calculations of rasonator frequencies of powder particles corresponding the fractal law of polymodal particle-size distribution with the scale set Bλ = 2,6, allow to assert that in the investigated conditions of irradiation occur the excitations of acoustic waves in the granular medium of powders extending with the speed, approximately on one-two order smaller, than longitudinal and transverse speeds of a sound in crystals.