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SMCs Fe/( 0.4-2.6 wt.%)SiO2/polymer prepared by vacuum/pressure impregnation

  • : Margita Kabatova1, Eva Dudrova2, Jan Fuzer3, Jana Fuzerova4
  • : 1Institute of Materials Research of Slovak Academy of Sciences, 2Institute of Materials Research SAS Kosice, 3UPJS Kosice, 4TU Kosice
  • : PDF Download
  • : 2014

Abstract

The SMCs Fe/(0.4-2.6 wt.%)SiO2/polymer were prepared using nontraditional procedure of vacuum/pressure impregnation (VPI) of low-temperature sintered compacts with removed residual stresses after compaction. The effect of the shape and size of iron particles, method of SiO2 addition (nano-particles and/or sol-gel coating) and effect of polymer type (shellac and/or thermoset SL450) on microstructure, thickness and continuity of electro-insulating layer was microscopically evaluated and correlated with electrical, magnetic and mechanical properties. The results showed that a thin and continuous electro-insulating layer can be achieved for spherical shaped iron particles with a smooth surface, while the use of shellac polymer is more advantageous than thermoset SL450. At addition of 2%SiO2 in the form of coating an acceptable combination of electrical resistance, magnetic coercivity and flexural strength (1123 μΩ.m, 288 A/m, ~ 80 MPa) was reached. An addition of 0.4 wt.%SiO2 in the form of nanopowder results in coercivity decreasing to 174-183 A/m. Irregular shape and rugged surface of iron particles cause local discontinuities of electro-insulating layer and thus decreasing the resistivity. In the case of irregularly shaped iron particles the more appropriate preparation of these composites is by mixing of the Fe/SiO2 powder with polymer, but the disadvantage is high coercivity, up to 800 A/m. The results showed that the VPI method applied for spherical iron powder has the potential to achieve a beneficial combination of electrical and mechanical characteristics and good magnetic properties at frequencies above 1 kHz.
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