Kompozyty oparte na kauczuku EPDM napełnione ferrytem strontu

Strontium ferrite was compounded with ethylene-propylene-diene monomer rubber (EPDM) to prepare rubber magnetic composites. Traditional sulfur as well as peroxide curing system were applied for cross-linking of the rubber matrices. The main objective of the work was to investigate the influence of magnetic filler content and type of curing system on the cross-linking, magnetic and physical-mechanical properties of the prepared composites. The results of the study revealed that EPDM based magnetic composites can be efficiently prepared by applying of both, sulfur and peroxide curing systems. Slightly higher values of tensile strength were found to have composites cured with peroxide curing system, what can be attributed to the suitable combination of dicumyl peroxide and co-agent (i.e. ethylene glycol dimethacrylate). The application of strontium ferrite into both type composites leads to a significant improvement of the remanent magnetic induction.Do kauczuku etylenowo-propylenowo-dienowego (EPDM) wprowadzono ferryt strontu w celu uzyskania magnetycznych kompozytów gumowych. Do wulkanizacji mieszanek kauczukowych użyto zarówno tradycyjnych siarkowych, jak i nadtlenkowych zespołów sieciujących. Głównym celem pracy było zbadanie wpływu zawartości magnetycznego napełniacza oraz rodzaju zespołu wulkanizującego na właściwości magnetyczne i fizyko-mechaniczne otrzymanych materiałów kompozytowych. Wyniki uzyskanych badań potwierdziły możliwość efektywnego otrzymywania kompozytów gumowych zarówno poprzez wulkanizację siarkową, jak i nadtlenkową. Nieznacznie większą wytrzymałość na rozciąganie kompozytów usieciowanych za pomocą nadtlenkowego zespołu wulkanizującego można przypisać odpowiedniej kombinacji nadtlenku dikumylu i koagenta (tzn. dimetakrylanu glikolu etylenowego). Zastosowanie ferrytu strontu w obu rodzajach kompozytów przyczyniło się do znacznego zwiększenia szczątkowej indukcji magnetycznej

Analysis of Thermal Field in Mineral Transformer Oil Based Magnetic Fluids

Growing interest in the use of magnetic fluids in power systems especially in transformers as insulation and a coolant is nowadays registered. Magnetisable nanofluids, which are used in cooling systems as an alternative to mineral transformer oil, are characterized by lower concentration of magnetic nanoparticles. The magnetic fluid has better heat transfer and dielectric properties such as breakdown than mineral transformer oil and it can be used to improve heat flow, thereby increasing the ability of the active parts to resist failures such as electromagnetic pulses. External magnetic field may be used for forced circulation of magnetic fluid. Magnetic force inside the magnetic fluid can be adequately controlled by adjusting the incident magnetic field. This paper presents thermal distribution, fluid flow and cooling ability of mineral transformer oil and magnetic fluid based on mineral transformer oil. The concentration of Fe₃O₄ magnetic nanoparticles is 0.15% volume of mineral transformer oil. The thermal field is generated by a steel conductor. Thermal distributions in mineral transformer oil and magnetic fluid are investigated and differences for both cases are discussed in the paper

Generation of Fe₃O₄ Nanoparticle Aggregates in a Ferrofluid Driven by External Electric Field

In the paper the experimental study of magnetic nanoparticle aggregation in a transformer oil based ferrofluid driven by an external electric field is reported. The studied ferrofluid was composed of the magnetite nanoparticles, oleic acid surfactant, and transformer oil. Generally, it is considered that superparamagnetic nanoparticles do not interact in the absence of external magnetic field. In the paper we present an experimental observation of the particle assembly formation in a direct current external electric field by optical microscopy. During the observation no external magnetic field was applied. A diluted low-polarity ferrofluid drop on a glass surface was exposed to the external static inhomogeneous electric field. It is assumed that induced dipole-dipole interaction and subsequent dielectrophoretic motion give rise to the electrohydrodynamic flow in the fluid after a certain time period. As a result, a visible particle chain was formed at the drop electrical equator. This demonstration is expected to contribute to the understanding of the streamer formation and electrical breakdown in transformer oil based ferrofluids