Influence of magnetic field on properties of nanoparticles produced by electro spark method

Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.Electrospark dispersion (ESD) is one of the production methods of fine-grained powders (FGP) of metals and alloys [1-2]. This method has a series of physical and technological advantages. It is simple enough as installation, ecologically clean, has no waste products, has low energy intensity and high efficiency. More over, high temperatures (>4000K) in zone of powders synthesis, super high rates of cooling (>109 K/s), high degree dispersion of obtained product (10 ÷ 1000 nm) are characteristic for this method. Under spark discharge duration in zone of plasma channel and surrounding liquid the electric and magnetic fields of complex shapes arise, which evidently influence on dispersion process. In this connection, investigation of external persistent magnetic field influence on phase composition and dispersion of fine-grained Fe powders was the main objective of the work.dc201

Temperature dependence of specific magnetization of metal carbon nano-composites synthesized by arc discharge in liquid

Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.Many of unusual physical and chemical properties of nanoparticles are defined by high ratio of their surface area to volume. Possibilities of changing surface area and its chemical composition open far-reaching perspectives for synthesis of new magnetic materials. Evaporation of metals in carbon-containing liquids or simultaneously with graphite allows the preparation of nanometallic particles in the carbon matrix which properties are scantily known. In the present work, Me-C composites have been produced by the arc discharge method in toluene using a powder metal anode (ADLP); their structure, phase composition and magnetic properties have been studied. The performed studies have shown that Me-C composites have a significantly changed phase composition. α-Fe powder transforms into Fe3C carbide almost completely, and solid carbon solution in nickel, Ni-C forms in the Ni powder. Heating the synthesized nanocomposites also leads to the change in their phase composition: after heating, a crystalline phase, Ni-C disappears in the Ni(B-2) powder, and oxides, FeO and Fe3O4 appear in the powder Fe(B-5-2) as well as the ratio of crystalline phases, α-Fe and Fe3С changes