Presentation Information
[P1-50]Optimization of Processing Parameters for High-Performance Anisotropic Bonded Magnets
*Ikenna C. Nlebedim1, Xubo Liu1, Parans Paranthaman2 (1. Division of Critical Materials, Ames National Laboratory (United States of America), 2. Chemical Sciences Division, Oak Ridge National Laboratory (United States of America))
Keywords:
Anisotropic bonded magnets,Magnetic alignment,Rare earth elements magnets,Near-net-shape fabrication,Permanent magnet optimization
This study relates to the correlation between key physical parameters governing the processing of anisotropic bonded magnets. These parameters include the magnetic loading fraction, binder rheological properties, externally applied magnetic field strength, the interaction between the magnet particles, and the degree of particle alignment. Understanding, optimizing and controlling these interdependent variables are crucial for the fabrication of high-performance bonded magnets while concurrently minimizing rare earth (REE) content.
The use of sintered Nd-Fe-B magnets in compact electronic applications frequently necessitates extensive machining which results in significant material wastage [1], [2]. In contrast, bonded magnets, which can be fabricated via near-net-shape processing, can significantly reduce machining-induced waste and, consequently, lead to REE materials resource efficiency. Additionally, given the intrinsically lower magnet fraction in bonded magnets compared to sintered magnets, there exists an opportunity for further reduction in critical REE utilization in applicable devices/systems. Thus, bonded magnets present a viable strategy for mitigating potential supply chain disruptions of REE materials essential for permanent magnet applications.
In this study, bonded magnets were synthesized through extrusion processing of anisotropic MQA powder at 40 and 50 vol.% loadings with an ethylene-vinyl acetate (EVA) copolymer binder. Differential scanning calorimetry (DSC) was employed to characterize the thermal transitions of EVA, both in pristine form and in composite formulations with magnetic powders. Magnetic hysteresis measurements and magnetization (M vs. T) as a function of temperature studies were conducted using a SQUID magnetometer, which also enabled the controlled alignment of samples during processing.
Figure 1 illustrates the M vs. T profiles for the 40 vol.% and 50 vol.% samples subjected to varying alignment field strengths. At an applied field of μ0H = 1 T, both compositions reached maximum alignment at approximately 340 K. The results demonstrate that alignment commences at the onset of EVA melting (~310 K) and culminates at ~340 K. Comparing Fig. 1a and 1b, the change in magnetization between the heating and cooling steps is less for the 50 vol.% sample, relative to the 40 vol.% sample. This result suggests that the degree of alignment achieved, especially at μ0H = 1 T, is higher for the 50 vol.% sample, compared to the 40 vol.% sample. Fig. 1c shows that μ0H = 1 T accomplished more than 80 vol% of the work needed to align the particles. This behavior is due to competing interactions, i.e., Zeeman energy, magnetostatic energy, and the drift force between molten binder and particles. A comprehensive understanding of these competing forces is paramount for refining processing parameters and optimizing the functional performance of bonded magnets.
The use of sintered Nd-Fe-B magnets in compact electronic applications frequently necessitates extensive machining which results in significant material wastage [1], [2]. In contrast, bonded magnets, which can be fabricated via near-net-shape processing, can significantly reduce machining-induced waste and, consequently, lead to REE materials resource efficiency. Additionally, given the intrinsically lower magnet fraction in bonded magnets compared to sintered magnets, there exists an opportunity for further reduction in critical REE utilization in applicable devices/systems. Thus, bonded magnets present a viable strategy for mitigating potential supply chain disruptions of REE materials essential for permanent magnet applications.
In this study, bonded magnets were synthesized through extrusion processing of anisotropic MQA powder at 40 and 50 vol.% loadings with an ethylene-vinyl acetate (EVA) copolymer binder. Differential scanning calorimetry (DSC) was employed to characterize the thermal transitions of EVA, both in pristine form and in composite formulations with magnetic powders. Magnetic hysteresis measurements and magnetization (M vs. T) as a function of temperature studies were conducted using a SQUID magnetometer, which also enabled the controlled alignment of samples during processing.
Figure 1 illustrates the M vs. T profiles for the 40 vol.% and 50 vol.% samples subjected to varying alignment field strengths. At an applied field of μ0H = 1 T, both compositions reached maximum alignment at approximately 340 K. The results demonstrate that alignment commences at the onset of EVA melting (~310 K) and culminates at ~340 K. Comparing Fig. 1a and 1b, the change in magnetization between the heating and cooling steps is less for the 50 vol.% sample, relative to the 40 vol.% sample. This result suggests that the degree of alignment achieved, especially at μ0H = 1 T, is higher for the 50 vol.% sample, compared to the 40 vol.% sample. Fig. 1c shows that μ0H = 1 T accomplished more than 80 vol% of the work needed to align the particles. This behavior is due to competing interactions, i.e., Zeeman energy, magnetostatic energy, and the drift force between molten binder and particles. A comprehensive understanding of these competing forces is paramount for refining processing parameters and optimizing the functional performance of bonded magnets.
