Formation of nickel dispersed carbon spheres from chelate resin and their magnetic properties

Carbon spheres with well-dispersed nickel particles were formed by the carbonization of chelate resin complexed with Ni(II) ions at 600 and 1000°C. When the amounts of nickel after carbonization were less than 1 mass%, more than 90% of Ni species were paramagnetic or superparamagnetic, irrespective of carbonization temperature, indicating that they were dispersed as small clusters. For samples with 2.2–3.4 mass% Ni and formed at 600°C, most of Ni species were ferromagnetic and their coercive force was less than 10 Oe at 280 K. The Ni metal particles in these samples were around 10 nm in size and well dispersed, but the number density of particles was not uniform in the samples of <1 mass% Ni. For samples with 3.4 mass% Ni and formed at 1000°C, more than 80% of Ni species were ferromagnetic and the coercive force slightly increased to about 20 Oe. The results of XRD measurement and TEM observation showed that the Ni metal particles were around 10–30 nm and well dispersed in agreement with the magnetic properties. The results showed that the present method is promising to form the carbon materials containing well dispersed fine metal particles.