Fundamental study on the mechanical strength of soft magnetic composite prepared by ultra-high aspect ratio flake iron powder using ball-milling process

ABSTRACT

Soft magnetic composites (SMCs) are consolidated ferromagnetic powders covered with polymers. Ultra-thin flat powder can effectively reduce eddy current loss of SMCs, even at the frequency at which next-generation semiconductor devices are driven. In this study, pure iron powders were processed with ball-milling to obtain the ultra-thin powder and prepare the SMC. The effect of aspect ratio of the powder on the mechanical strength of SMC was investigated. Although the maximum bending stress of SMC made of iron particles with an aspect ratio of 1140 reached 60% of the strength of sintered iron powder, the increase in the maximum bending stress with increasing aspect ratio slowed down when the aspect ratio exceeded 100. The reason for the slowdown was assumed to be a decrease in insulating film coverage on the particle at high aspect ratio ranges due to the stacking and welding of particles during the ball milling process.

KEYWORDS:

• Ball milling process
• soft magnetic composite
• rule of mixtures
• iron powder
• bend testing

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Koki Ohba

Koki Ohba obtained Bachelor in Engineering in Kyushu Institute of Technology in 2020. He studies about relationships between characteristics of iron powders and magnetic properties of iron cores made by them. His research interests focus on the relationships among powder, mechanical and magnetic properties of iron cores.

Mizuki Tanaka

Mizuki Tanaka obtained Bachelor in Engineering in Kyushu Institute of Technology in 2020. He studies about relationships between characteristics of iron powders and mechanical properties of iron cores made by them. His research interests focus on the relationships among powder and mechanical properties of iron cores.

Satoshi Motozuka

Satoshi Motozuka studied material science at the Tokyo Institute of Technology. In 2013, he joined the group of Prof. Junzo Tanaka, for his diploma research about interfacial design between oxide and metals and received his diploma in engineering in 2015. In 2019, he became associate professor in the department of material science and engineering at Kyushu Institute of Technology. His research interests focus on the interfacial interaction during mechanical powder milling process.

Daichi Noda

Daichi Noda obtained Bachelor in Engineering in Nagaoka University of Technology in 2020. He studies about crystallographic texture on iron powder for iron cores. His current research interests focus on biological properties of powder materials.

Mai Shibahara

Mai Shibahara, bachelor graduated of engineering in Ryukoku University, is mainly devoted to research of functionalized surfaces using ultrathin polymer films.

Takehiro Kawauchi

Takehiro Kawauchi is a professor in the Faculty of Advanced Science & Technology, Ryukoku University. His current research interests are the development of functionalized materials based on polymer complexes, design and synthesis of network polymers, and stereocontrol of vinyl polymers.