The prebreakdown state of magnetic fluids at influence of electrical and magnetic field

The development of electric breakdown in magnetic fluids (MFs) has been analyzed. MFs have been consisted of magnetic particles (Fe3O4) of nanometric size, coated with oleic acid as a surfactant, dispersed in transformer oil. The electro-physical processes, which appear at action of the DC electric field and constant magnetic field on MFs, were observed. These processes have effect on electric breakdown. The especial attention was devoted to state in MFs before breakdown, during breakdown and post breakdown

Analýza I(t) závislosti počas štrukturalizácie magnetických nanočastíc v magnetickej kvapaline

The previous experiments were devoted to observation of structuralization processes in magnetic fluids in dependence on time at constant value of homogenous magnetic fields. The average value of clusters of magnetite particles reached stabilized length that depended on volume concentration of magnetite particles in magnetic fluids. This work is oriented on observation and explanation of anomaly on dependences of current intensity (I) on time (t) in magnetic fluids with help of observation of structuralization processes results at respecting of space charge. This anomaly was detected at upper concentration of magnetite particles (>1%) on I(t) dependences in given time region that characterizes the change of energetic conditions in magnetic fluids

Dielektrické a magnetoelektrické vlastnosti magnetických kvapalin

Výskum dielektrických a magnetodielektrických vlastností magnetických kvapalín je úzko spojený s magnetodielektrickým javom, ktorý sa prejavuje magnetodielektrickou anizotropiou [3]. Výsledky výskumu elektrickej pevnosti magnetických kvapalín s rôznymi koncentráciami magnetitových častíc (0,125%-4%) pri voľbe vyššie uvedeného usporiadania taktiež poukázali na magnetodielektrickú anizotropiu, ktorá sa prejavuje značnou odlišnosťou elektrickej pevnosti sledovanej magnetickej kvapaliny v závislosti od orientácie elektrického a magnetického poľa. Jednou z pozorovaných makroskopických výpovedeschopných veličín je relatívna permitivita (er) magnetickej kvapaliny. Permitivita je funkciou aplikovaného poľa [1] a vzájomnej orientácie intenzity elektrického a magnetického poľa

Magnetodielectric anisotropy in magnetic fluids in temperature interval from 20 °C to 80 °C

Substitution of transformer oil as insulator medium by magnetic fluid in transformers requires observation of electric properties of magnetic fluids at temperatures higher than 20 °C. That´s why important physical quantities were measured at temperature in interval from 20 °C to 80 °C. The magnetodielectric anisotropy was studied at the same temperature region. Two important quantities have been measured: specific electric conductivity and dielectric breakdown strength of magnetic fluids at volume concentrations from 0,185 % to 2 %. So the behavior of magnetic fluids as insulator medium could be observed at working conditions of transformers

Néel and Brownian rotations in ferronematics

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