Structural and Magnetic Characteristics of Composite Compacts of <inline-formula> <tex-math notation="TeX">${\rm Fe}/{\rm Fe}_{3}{\rm O}_{4}$ </tex-math></inline-formula> Type Obtained by Sintering

Abstract

Soft magnetic composite of Fe/Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> type was synthesized by mechanical milling and reactive sintering starting from a mixture of Fe and Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> commercial powders. During mechanical milling, the Fe and Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> phases start to react after 120 min. A composite powder of Fe/Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> type results after 60 and 120 min of milling. The composite powder obtained by milling was pressed in toroidal shape at 100 up to 300 MPa. The green composite compacts (Fe/Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) were sintered at 1100 °C for 6 h, resulting in Fe/Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> like sintered composite compacts having an amount of FeO phase. The microstructure analysis shows an iron matrix that embeds iron oxide clusters. The magnetic measurements in dc current indicate the positive influence of the increased applied pressure on the magnetic permeability and saturation induction characteristics. The investigations in dc revealed that the milling time has almost no influence on the magnetic characteristics of the sintered composite compacts. ac investigations showed that the magnetic permeability decreases upon increasing the testing frequency. The total losses increase significantly by increasing the frequency due to the excessive increase in eddy currents at higher frequencies.