(221t) Method of Controlling the Shape of Cube-like Hematite Particles and Influence of Externalmagnetic Field on the Aggregate Structures
AIChE Annual Meeting
2019
2019 AIChE Annual Meeting
Engineering Sciences and Fundamentals
Poster Session: Fluid Mechanics
Monday, November 11, 2019 - 3:30pm to 5:15pm
Since the magnetization of hematite particles is significantly smaller than that of ferromagnetic
particles, the application of their magnetic particles have not been paid attention up to the present as a
research subject. However, as the size of particles is increased and approaches micron-order, the
magnetic particle-particle interaction energy surpasses the thermal energy, and therefore as a result,
physical characteristics such as particle aggregate structure are significantly influenced by their magnetic
properties and the applied magnetic field strength. Moreover, the gravitational force comes to have a
significant influence on the particle motion in a suspension. Monte Carlo simulations[1] have already
predicted that a phase change in the particle aggregate structure arises dependent on the magnetic
particle-particle and particle-field interaction strengths. The final goal of the present study is to verify
this phage change in a cubic hematite particle suspension in an experimental approach. To this end, the
first study is to develop a synthesis technique for obtaining a well mono-dispersed cubic hematite
particles with a desirable diameter, and the second study is to clarify the influence of an applied
magnetic field on the aggregate structures. In the study on the synthesis technique, we have
investigated the dependence of the particle size and shape on the aging time and the decantation
interval for a variety of conditions of these factors. From this experiment, it is seen that the aging time is
the main factor for determining the particle shape and the decantation interval plays a main role to
determine the degree of the mono-dispersibility of cubic particles. In the study of aggregation
phenomena in the gravitational field, we have observed the aggregate structures formed at the bottom
surface after the sedimentation using an inverted light microscope. In the situation of terrestrial
magnetism, the magnetic moments of the cubic particles are not strongly restricted to the field direction,
and therefore particles form relatively thin chain-like clusters and these clusters do not show a strong
orientational characteristic along the field direction. In contrast, in the situation of an applied magnetic
field, thick and long chain-like clusters are formed along the magnetic field direction. From this
difference in the aggregate structures, we understand that they are possibly controlled by the applied
magnetic field strength and a phase change in the internal structure of the aggregates is expected to
arise within a narrow range of the change in the applied magnetic field strength.
particles, the application of their magnetic particles have not been paid attention up to the present as a
research subject. However, as the size of particles is increased and approaches micron-order, the
magnetic particle-particle interaction energy surpasses the thermal energy, and therefore as a result,
physical characteristics such as particle aggregate structure are significantly influenced by their magnetic
properties and the applied magnetic field strength. Moreover, the gravitational force comes to have a
significant influence on the particle motion in a suspension. Monte Carlo simulations[1] have already
predicted that a phase change in the particle aggregate structure arises dependent on the magnetic
particle-particle and particle-field interaction strengths. The final goal of the present study is to verify
this phage change in a cubic hematite particle suspension in an experimental approach. To this end, the
first study is to develop a synthesis technique for obtaining a well mono-dispersed cubic hematite
particles with a desirable diameter, and the second study is to clarify the influence of an applied
magnetic field on the aggregate structures. In the study on the synthesis technique, we have
investigated the dependence of the particle size and shape on the aging time and the decantation
interval for a variety of conditions of these factors. From this experiment, it is seen that the aging time is
the main factor for determining the particle shape and the decantation interval plays a main role to
determine the degree of the mono-dispersibility of cubic particles. In the study of aggregation
phenomena in the gravitational field, we have observed the aggregate structures formed at the bottom
surface after the sedimentation using an inverted light microscope. In the situation of terrestrial
magnetism, the magnetic moments of the cubic particles are not strongly restricted to the field direction,
and therefore particles form relatively thin chain-like clusters and these clusters do not show a strong
orientational characteristic along the field direction. In contrast, in the situation of an applied magnetic
field, thick and long chain-like clusters are formed along the magnetic field direction. From this
difference in the aggregate structures, we understand that they are possibly controlled by the applied
magnetic field strength and a phase change in the internal structure of the aggregates is expected to
arise within a narrow range of the change in the applied magnetic field strength.