A novel method for the modification of magnetite nanoparticles for the enhancement of its dispersibility in hydrophobic media

Abstract

Different mixing methods were used for the fatty acid modification of magnetite nanoparticles. The magnetite nanoparticles were dissolved in ethanol with a previously dissolved oleic or stearic acid solution. The mix was then homogenized and washed to eliminate the unreacted fatty acid. The modified nanoparticles were FTIR analysis confirmed that the modified nanoparticles presented the characteristic groups of the fatty acids. The vibrating sample magnetometer analysis (VSM) showed a very slight decrease in the magnetic properties of the magnetite, from 88.7 to 53.7 emu/g, which obviously was due to the presence of the fatty acids. TGA showed that the fatty acid modification degree of the magnetite was less than that reported elsewhere, nonetheless, during the precipitation tests in toluene; it was observed that the modification was sufficient to maintain the stability of the dispersion without affecting the magnetic properties. Additionally, TEM micrographs showed that the modified magnetite nanoparticles formed a cluster, with the fatty acids surrounding the magnetite nanoparticles. Confirming that the fatty acid layer was deposited as monolayers on the magnetite particle surface of approximately 2 nm in thickness with OA and 2.3 nm with SA. It was observed that the use of the two fatty acids produced inter-digitation among the fatty acids. Finally, nanocomposites based on liquid silicone rubber (LSR) were prepared with modified and unmodified magnetite and their rheological and magnetic behavior was studied. This fatty acid modification of magnetite particles improved the dispersion and distribution of modified particles into the silicon matrix.