Preparation and soft magnetic properties of spark plasma sintered compacts based on Fe-Si-B glassy powder

International audienceAmorphous powder of Fe75Si20B5 (at.%) was prepared by wet mechanical alloying route using benzene as surfactant. The amorphous phase is obtained after 60 h of milling. Structural, morphological, and thermal characteristics were investigated. The as-milled powder consists in micrometric particles with a mean diameter of 10.4 mu m which are formed by the agglomeration of smaller particles. The amorphous powder is thermally stable up to the temperature of 490 degrees C. Spark plasma sintered compacts were prepared from the amorphous powders at sintering temperatures of 800, 850 and 900 degrees C. The phases formation and their evolution was investigated by X-ray diffraction technique showing that Fe3Si and Fe2B are the main phases formed during the spark plasma sintering process. Fe75Si20B5 (at.%) samples in the form of a ring were investigated in DC and AC magnetization regime. It was found that the boride phase formation (during sintering) and the low density of the compacts affect the magnetic properties of the compacts. In addition, a superficial contamination of the compacts with carbon (a layer of 2-3 mu m) was evidenced, contributing thus to their soft magnetic deterioration. Increasing of the saturation induction, maximum relative permeability and initial relative permeability was observed by increasing both sintering temperature and time. It was generally observed that the compacts with high density have higher total core losses at high frequency

Mechanosynthesis, structural, thermal and magnetic characteristics of oleic acid coated Fe3O4 nanoparticles

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Structure-properties changes in ZnO-PbO-GeO 2 glasses

We have studied the structure of ZnO-PbO-GeO2 glasses by Fourier transform infrared spectroscopy and showed that the analysis of the vibrational spectra can lead to a quantitative description of the network structure in terms of the fraction of the local germanate polyhedra. The presence of GeO4, GeO6 and GeO4 with NBOs units was evidenced in the studied glass network. The initial additions of ZnO would introduce modifier Zn2+ ions at the expense of the former PbO4 units. With increasing ZnO content, ZnO4 tetrahedra would mainly replace modifier PbO. The decrease in density when introducing ZnO at the expense of PbO content is not only due to the vast difference in molecular mass between PbO and ZnO, but also due to the formation of Q2 and Q3 units. The glass network of the investigated glasses posseses a more covalent character upon replacing ZnO for PbO. This is the reason for increasing the microhardness and the glass transformation temperature of the glasses investigated with increasing zinc oxide content. The change in the conductivity at certain temperature not only attributed to the change in the covalency of the glass matrix upon replacing PbO by ZnO but also due to a change in the strain energy because of the change in Vm