Functional magnetic nanocomposites for EMI shielding

J. Azadmanjiri, Cordelia Selomulya, George P. Simon, Kiyonori Suzuki

Research output: Chapter in Book/Report/Conference proceedingConference PaperResearchpeer-review


Microwave heat treatment of iron oxide nanoparticles coated with conductive polymers such as polypyrrole is a simple method to increase the conductivity of the polymer via conversion of it from an amorphous material to a graphitic structure. The combination of magnetic and conductive composite nanoparticles can be used to develop electromagnetic interference (EMI) shielding materials, particularly effective in the high frequency range. However, heat treatment often decreases the magnetization of iron oxide nanoparticles by oxidation to a non-magnetic phase. We have found we can prevent this effect, if maghemite (γ-Fe2O3) nanoparticles are first coated with silica via the sol-gel method. The influence of microwave heat treatment on structure formation and the magnetic behavior of these nanoparticles were subsequently investigated by FT-IR, TGA, XRD, TEM, and VSM. The particles showed core-shell structures with a maghemite core and silica shell. The saturation magnetization (Ms) of silica-coated maghemite nanoparticles after heating in a standard household microwave oven was almost seven times higher than bare maghemite nanoparticles that were similarly heat-treated. The significant reduction of Ms for bare γ-Fe2O3 nanoparticles after microwave treatment was due to a phase change to α-Fe2O3 (hematite). Conversely, silica-coated nanoparticles underwent a phase change to Fe3O4 (magnetite) and Fe2SiO4 (fayalite), which accounted for only a slight reduction in Ms, compared to the pre-heat treated particles.

Original languageEnglish
Title of host publication10AIChE - 2010 AIChE Annual Meeting, Conference Proceedings
Publication statusPublished - 2010
EventAIChE Annual Meeting 2010 - Salt Lake City, United States of America
Duration: 7 Nov 201012 Nov 2010


ConferenceAIChE Annual Meeting 2010
Abbreviated titleAIChE 2010
Country/TerritoryUnited States of America
CitySalt Lake City
Internet address


  • Mahemite
  • Microwave heat treatment
  • Reduction
  • Silica coated

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