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Iron/SiO2/Shellac Composites Prepared by Vacuum/Pressure Impregnation

  • : Kabátová M. 1, Dudrová E. 1, Füzer J. 2, Füzerová J. 3, Kollár P. 2
  • : 1Institute of Materials Research of SAS, 2P.J.Šafárik University, 3Technical University Košice 1Institute of Materials Research of SAS, 2P.J.Šafárik University, 3Technical University Košice 1Institute of Materials Research of SAS, 2P.J.Šafárik University, 3Technical University Košice 1Institute of Materials Research of SAS, 2P.J.Šafárik University, 3Technical University Košice 1Institute of Materials Research of SAS, 2P.J.Šafárik University, 3Technical University Košice
  • : 2013, Vol 3, p. 157-162
  • : PDF Download
  • : 2013

Abstract

Fe/SiO2/shellac composites on the basis of iron powder with irregularly and/or spherically shaped particles were prepared using vacuum/pressure impregnation (VPI). SiO2 was implemented either as nanopowder or by sol-gel coating. VPI of low-temperature sintered Fe/SiO2 compacts (850°C for 15min) with shellac dissolved in ethanol (14g/100ml) was performed in a steel container at vacuum of ~10-2 kPa/15 min followed by pressure of ~500 kPa/15min. The influence of the shape and size of the iron particles on the properties of the electro-insulating layer and the values of electrical resistance and coercivity of studied composites was evaluated. The results showed that the continuity of insulating layer as well as electrical resistivity and coercivity are primarily controlled by the shape of iron particles. A rough particle surface may lead to discontinuities of the insulating layer. In the case of spherically shaped iron particles with a smooth surface the continuous and a uniform insulating layer was attained resulting in improving electrical resistivity by three orders of magnitude when compared to the composites based on irregularly shaped iron particles.

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