Mechanism and Effect of the Dilution Gas Flow Rate on Various Fe–Si/SiO2 Soft Magnetic Composites during Fluidised Bed Chemical Vapour Deposition

Zhaoyang Wu,Jixiang Jia,Zihan Gao,Hui Kong,Mingyang Li,Qian Zhao

doi:10.3390/cryst11080963

Zhaoyang Wu, Jixiang Jia + Show 4 more

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https://doi.org/10.3390/cryst11080963

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Journal: Crystals	Publication Date: Aug 16, 2021
Citations: 3	License type: CC BY 4.0

Affiliation: Ansteel (China), Anhui University of Technology

Abstract

The effect of the dilution gas flow rate on inorganic oxide insulating layers can improve fluidised bed chemical vapour deposition (FBCVD) in Fe–Si/inorganic-oxide soft magnetic composites and obtain excellent magnetic properties. Herein, Fe–Si/SiO2 composite particles coated via FBCVD and deposited at a 125–350 mL/min Ar-dilution gas flow rate were prepared and sintered into soft magnetic composites. Results demonstrate that SiO2 deposited on the Fe–Si substrate particle surface changed from submicron SiO2 clusters (125 mL/min) to an incomplete SiO2 film, then to a complete SiO2 film, and finally to a porous SiO2 film as the Ar-dilution gas flow rate increased. SiO2 layers began to transform from the amorphous to the beta-cristobalite state with a hexagonal crystal structure between 1149.45 K and 1280.75 K. However, the SiO2 amorphous layers’ crystallisation did not affect the Fe–Si substrate particles’ crystal structure. With the increasing Ar-dilution gas flow rate, the saturation magnetisation of Fe–Si/SiO2 soft magnetic composites initially decreased and then increased. The electrical resistivity increased before 150 mL/min, followed by an increase between 150 and 250 mL/min and then decreased, whereas the total core loss exhibited the opposite trend. These results show that magnetic performance can be promoted by selecting a suitable dilution flow rate.

Highlights

For advanced performance, as an energy conversion material in electromagnetic devices [1,2,3] and high-power high-frequency electrical devices [4], Fe–Si/inorganic-oxide soft magnetic composites have been studied by researchers worldwide
The even distribution of these three elements indicates that an excellent and uniform SiO2 layer can be deposited on the surface of the Fe–Si substrate particles through fluidised bed chemical vapour deposition (FBCVD)
The cross-section backscattered images in Figure 2 confirmed that the Fe–Si/SiO2 composite particles could be obtained at a gas flow rate of 125 mL/min for the Ar dilution gas; the optimal Ar dilution gas flow rate range for forming an integrated Fe–Si/SiO2 core/shell heterostructure was between 200 and 300 mL/min

Summary

Introduction

As an energy conversion material in electromagnetic devices [1,2,3] and high-power high-frequency electrical devices [4], Fe–Si/inorganic-oxide soft magnetic composites have been studied by researchers worldwide. To coat an inorganic oxide insulating layer on Fe–Si magnetic particles, several methods, such as ball milling [5], mixed sintering [6], and the sol–gel process [7,8], were used to obtain Fe–Si/inorganic-oxide core–shell particles with high insulating quality. The disadvantage of these methods is the uncontrollability of homogeneity for the inorganic oxide-insulating layer. Laboratory studies demonstrate that the FBCVD technique is a suitable and effective method for coating inorganic oxide-insulating layers on Fe–Si magnetic particles [10]. An 800-nm-thick inorganic oxide insulating layer can be deposited at a rate ranging between 4.2 and 17.6 nm/min on Fe–Si substrate particles [11]

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