An XPS investigation on the thermal stability of the insulating surface layer of soft magnetic composite powder

Abstract

Ferromagnetic powder particles coated with electrical insulating inorganic layers constitute composite materials used as powdered iron cores in electromagnetic applications. The aforementioned surface layers of these soft magnetic composites (SMC) are responsible for their high electrical resistivity. The perseverance of the coating through annealing processing step is crucial to the performance of finalized SMC products. In the present study, the thermal stability and microstructure of an iron phosphate based surface layer from a commercially available SMC powder were investigated by coupling various analytical techniques. The material was annealed at different temperature regimes, both in oxidizing (air) and inert (N2) conditions in order to isolate the effect of temperature from the atmosphere composition on the chemical state of the coating. X‐ray photoelectron spectroscopy (XPS) was utilized to assess the composition of the surface layer at all conditions. Moreover, phosphate‐based chemical standards were processed and analyzed in a similar manner so as to facilitate the interpretation of the observed XPS spectra from the SMC powder. High resolution scanning electron microscopy, energy‐dispersive X‐ray spectrometry and X‐ray diffraction were implemented in order to fully characterize the material under question. The results indicated the transition of the insulating layer from an amorphous state to fully crystalline under annealing in inert atmospheric conditions. Moreover, it was observed that phosphates are still present in the coating in mixture of valance states. Conversely, a thick iron oxide scale was formed under treatment in air, and no phosphorus signal was detected, indicating a total decomposition of the layer. Copyright © 2016 John Wiley & Sons, Ltd.

Surface Modification of ZnO Nanocrystals with Conjugated Polyelectrolytes Carrying Different Counterions for Inverted Perovskite Light-Emitting Diodes

“…33 Meanwhile, the B 1s and P 2p peaks at 193.2 and 135.5 eV were observed for PFN-BF 4 and PFN-PF 6 , respectively, as revealed in Figure S1b,c. 34,35 In addition, the F 1s peak was detected at 685.1 and 685.8 eV for both PFN-BF 4 and PFN-PF 6 , respectively, as shown in Figure S1d. 36 The slight energy difference of the F 1s signal between PFN-BF 4 and PFN-PF 6 can be attributed to different chemical environments of the F element on the BF 4 and PF 6 groups.…”

Recyclable 3D‐Printed Aqueous Lithium‐Ion Battery

“…This is in agreement with the values illustrated in the literature. [ 42 ] Deconvolution of Fe 2 p 3/2 peak showed two peaks at 711.7 and 713.9 eV, while deconvolution of Fe 2 p 1/2 showed two peaks centered at 725.6 and 727.6 eV consistent with Fe(III) in FePO 4 . Similar core‐level emission was observed in FPO after charge–discharge cycling.…”

Tuning Sugar Biomass Waste Conversion for the Preparation of Carbon Materials for Supercapacitors and Catalysts for Oxygen Reduction

“…[40,65] The fourth peak (136 eV) referred to phosphorus in the structure of P 2 O 5 oxide or phosphate groups. [40,85] P-doping in ChP-Bp material introduced many P─O bonds for the formation of a thin layer on the surface of carbon, thereby improved the electrochemical properties. [26] The P2p spectrum of the CChK-Bp sample had only a single peak at 136 eV, corresponding to phosphorus in P 2 O 5 .…”