The characterization of the crystallization kinetics of amorphous soft magnetic materials, namely NANOPERM™, a Fe₈₈Zr₇B₄Cu₁ alloy and its derivatives, is presented and discussed in this work. Crystallization kinetics is observed isothermally and nonisothermally by differential scanning calorimetry (DSC), synchrotron x-ray diffraction (XRD) and vibrating sample magnetometry (VSM). Vibrating sample magnetometry and x-ray diffractometry, used concurrently with differential scanning calorimetry in observing crystallization kinetics, is a novel concept that takes advantage of the magnetic property that the Curie temperature of the amorphous phase of the NANOPERM™ alloy is below its primary crystallization temperature. This property allows for crystallization kinetics, i.e. the volume of nanocrystals transformed in the process, to be inferred magnetically, as well as thermally and microstructurally. The Johnson-Mehl-Avrami model for isothermal crystallization kinetics is compared with the Kissinger model for non-isothermal crystallization kinetics using data gathered from the three characterization methods. Linear regression and non-linear regression analysis of the mechanisms of crystallization in NANOPERM™ ribbon and the significance of the values that describe them, namely the activation energy Q and the morphology index n, are investigated for isothermal and constant-heating crystallization. The activation energy for NANOPERM™ ribbon is reported here to be in the range Q = 2.8–3.4 eV, with the crystallization kinetics proceeding by three-dimensional diffusion and immediate nucleation, where the morphology index, n = 1.5. Extensions of the isothermal model for crystallization kinetics to non-isothermal cases are also discussed.

This work also presents several processing techniques for producing soft amorphous ribbons and freestanding nanoparticles. It describes in detail the synthesis of freestanding nanoparticles via a one-step plasma process and the design and implementation of the gas manifold, an apparatus to improve the quench rate of the process. Applications of these amorphous soft magnetic alloys, in particular applications for NANOPERM™ in power electronics, are also discussed in one of the final chapters.