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High temperature characterization of the particle surface coating on soft magnetic powder components using electron microscopy

Bergström, Henrik LU (2022) KASM10 20221
Centre for Analysis and Synthesis
Abstract
This master’s thesis evaluates the feasibility of using in situ transmission electron microscopy (TEM) to study the effects of high temperature heat treatments of a coated soft magnetic composite (SMC) sample. SMCs are an increasingly competitive magnetic powder material which finds use in for instance electric motors. A heat treatment following compaction for SMCs is an essential part of manufacturing which improves magnetic properties and relieves built-up stresses. It has previously been established that the maximum heat treatment temperature of a
coated SMC is determined by the thermal stability of the coating. The aim of this work is therefore to evaluate a method using in situ TEM to locally study the thermally induced breakdown of... (More)
This master’s thesis evaluates the feasibility of using in situ transmission electron microscopy (TEM) to study the effects of high temperature heat treatments of a coated soft magnetic composite (SMC) sample. SMCs are an increasingly competitive magnetic powder material which finds use in for instance electric motors. A heat treatment following compaction for SMCs is an essential part of manufacturing which improves magnetic properties and relieves built-up stresses. It has previously been established that the maximum heat treatment temperature of a
coated SMC is determined by the thermal stability of the coating. The aim of this work is therefore to evaluate a method using in situ TEM to locally study the thermally induced breakdown of the coating to provide insights that are useful in the development of new coating technologies. The SMC sample from Höganäs AB was first cut, embedded and polished in order to prepare it for ion milling using a focused ion beam (FIB). A 200 – 250 nm TEM lamella was mounted on a half-grid using FIB. The sample was heated to around 600° C using a TEM furnace holder and TEM/scanning TEM (STEM) mode images, nanobeam diffraction patterns and energy-dispersive X-ray spectroscopy (XEDS) maps/scans were acquired after heating. The coating was for the most part intact after heating to around 600° C with the exception for one region where it appeared to break down. The interpretation of these results was however complicated by a Si signal that most likely originated from the polishing process. In situ TEM is a very promising technique in the context of the local investigation of SMCs but the Si contamination needs to be further investigated as it potentially makes the results unrepresentative. (Less)
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author
Bergström, Henrik LU
supervisor
organization
course
KASM10 20221
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Materials Chemistry, In situ, Transmission Electron Microscopy, Soft Magnetic Composites, Heat Treatment, Focused Ion Beam
language
English
id
9086760
date added to LUP
2022-07-01 09:09:31
date last changed
2022-07-01 09:09:31
@misc{9086760,
  abstract     = {{This master’s thesis evaluates the feasibility of using in situ transmission electron microscopy (TEM) to study the effects of high temperature heat treatments of a coated soft magnetic composite (SMC) sample. SMCs are an increasingly competitive magnetic powder material which finds use in for instance electric motors. A heat treatment following compaction for SMCs is an essential part of manufacturing which improves magnetic properties and relieves built-up stresses. It has previously been established that the maximum heat treatment temperature of a
coated SMC is determined by the thermal stability of the coating. The aim of this work is therefore to evaluate a method using in situ TEM to locally study the thermally induced breakdown of the coating to provide insights that are useful in the development of new coating technologies. The SMC sample from Höganäs AB was first cut, embedded and polished in order to prepare it for ion milling using a focused ion beam (FIB). A 200 – 250 nm TEM lamella was mounted on a half-grid using FIB. The sample was heated to around 600° C using a TEM furnace holder and TEM/scanning TEM (STEM) mode images, nanobeam diffraction patterns and energy-dispersive X-ray spectroscopy (XEDS) maps/scans were acquired after heating. The coating was for the most part intact after heating to around 600° C with the exception for one region where it appeared to break down. The interpretation of these results was however complicated by a Si signal that most likely originated from the polishing process. In situ TEM is a very promising technique in the context of the local investigation of SMCs but the Si contamination needs to be further investigated as it potentially makes the results unrepresentative.}},
  author       = {{Bergström, Henrik}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{High temperature characterization of the particle surface coating on soft magnetic powder components using electron microscopy}},
  year         = {{2022}},
}