Properties of carbon microspheres with magnetic graphite nanostructures

E. Sharoyan, A. Manukyan, A. Mirzakhanyan, C. Sanchez, A. Kocharian, O. Bernal
California State University. Los Angeles,
United States

Keywords: magnetization, susceptibility, graphite nanostructures


In recent years, the carbon microspheres attract great attention due to applications in various areas, namely, in supercapacitors, filters of gases and fluids, fuel cells as substrates. Among practical applications is a high-temperature magnetism, observed in various carbon-based materials, etc. Below we present a number of preliminary results related to synthesis and investigation of carbon microspheres with interesting magnetic properties. Carbon microspheres have been prepared by using the method of solid-phase pyrolysis where as a precursor metal-free phthalocyanine was used, according to the reaction H2(C32H16N8) -> 32C. By changing the pyrolysis conditions we prepared carbon microspheres with a mean diameter 2-3.8 μm consisting of graphitized nanocrystallites with a thickness of 5-15 graphene layers and width of 5-20 nm and sufficiently narrow size distribution. In particular, at T_pyr=700°C and tpyr=60 min we obtained carbon microspheres with a mean diameter d=3.4±0.15 μm. Magnetic characteristics of these samples were investigated with a vibrational magnetometer in the temperature range 5-300К, in magnetic fields up to 80 kOe, as well as with the ESR method. Analysis of curves М-Т and М-Н presented shows the presence of paramagnetic centers with the concentration n=3∙10^19 spin/g and temperature-independent diamagnetism with susceptibility of χ_Dia=1.5∙10^-6 emu/g∙Oe. The parameters of ESR spectrum were measured at 300K: the g-factor 2.0031 and intensity ~5∙10^19 spin/g.