Advances in Dielectric Materials and Electronic Devices: Magnetic Materials
Sponsored by: ACerS Electronics Division
Program Organizers: Amar Bhalla, University of Texas; Ruyan Guo, University of Texas at San Antonio; Rick Ubic, Boise State University; Matjaž Spreitzer, Jožef Stefan Institute
Monday 2:00 PM
October 18, 2021
Room: B235
Location: Greater Columbus Convention Center
Session Chair: Amar Bhalla, University of Texas at San Antonio
2:00 PM
Magnetocaloric Composites for High Efficiency Thermal Management: Christopher Kovacs1; Timothy Haugan2; Michael McLeod3; Devin Grant4; 1Scintillating Solutions LLC; 2Air Force Research Laboratory; 3University of Dayton Research Institute; 4Central State University
Cooling with magnetocaloric materials has been pursued by numerous agencies and companies, but many of the challenges remain unsolved. Some of these challenges are excessive pressure drop across the magnetocaloric regenerator, mechanical failure from magnetostructural and thermal cycling, and material degradation due to exposure. Presented here is a continuously processed powder-in-tube (PIT) composite in which the tube is a high thermal conductivity metal, and the core is dense GdF3. Using this PIT composite, the magnetocaloric material is not exposed to the external environment. Additionally, the metal sheathing keeps the magnetocaloric material in slight compression to prevent mechanical fatigue. The arrangement of these PIT wires into an axially aligned array results in a high effective thermal conductivity, low demagnetization factor, and low impedance regenerator, overcoming some of the most difficult challenges in proposed magnetocaloric systems.
2:20 PM
Improvement of the Magnetic Characteristics of Materials Due to the Formation of Unidirectional Boundaries of Ferrite during Processing in SHS Conditions: Borys Sereda1; Dmytro Sereda1; Vitalyy Volokh1; 1Dneprovsky State Technical University
To improve the magnetic characteristics of armco-iron, such as magnetic permeability and coercive force, samples were processed in conditions of self-propagating high-temperature synthesis. Heating was carried out to a temperature of 900 ° C, followed by isothermal holding and cooling at various speeds. The study of the microstructure of samples with a carbon content of up to 0.015% showed that grain boundaries are formed, which are divided into three unidirectional sections. Areas are established where both ends of the boundary enter triple joints with opposite angles exceeding 170 or quadruple joints are observed. Due to the non-stationary stage of the SHS process, a fine-grained structure is formed, which leads to an increase in the coercive force from 0.97 A / cm to 1.65 A / cm and, accordingly, to an increase in hardness from 95 to 157 HB.
2:40 PM
The influence of the Microstructure Obtained After Processing in SHS Conditions on the Magnetic Characteristics of Steels: Borys Sereda1; Dmytro Sereda1; Vitalyy Volokh1; 1Dneprovsky State Technical University
Metallographic studies were carried out to establish the influence of the microstructure after cold deformation and subsequent processing under conditions of self-propagating high-temperature synthesis (SHS) on the magnetic characteristics of steels, such as coercive force, grain size, and the relative number of unidirectional boundaries. After processing the cold-deformed material under SHS conditions, the grain size decreases from 10.3 μm to 5.22 μm, and the relative number of unidirectional boundaries increased from 23.7% to 37.2%. The fine-fiber structure is the result of elongation and deformation of grains during material drawing, which is confirmed by the high value of the coercive force of 9.4 A/cm. The non-stationary stage of the process of self-propagating high-temperature synthesis, leads to grain refinement and an increase in magnetic permeability. The value of coercive force allows you to control changes in the structure of the wire at all stages of its metallurgical production.
3:00 PM
The Effect of Deformation of Low Alloy Steels Used in Metallurgy on Their Magnetic Characteristics: Borys Sereda1; Dmytro Sereda1; Vitalyy Volokh1; 1Dneprovsky State Technical University
As a result of studies of steel samples used in metallurgy during uniaxial tension of flat samples, the nature of the growth of the coercive force from the applied stresses was established during the transition of the metal from the elastic zone to the elastoplastic. The coercive force was determined on a KPM-S semi-automatic coercimeter in the central part of the sample. So for steel with 0.17% C, the value of the coercive force varied from 2.9 to 7.8 A/cm with an applied load of up to 500 MPa. The dependences of the coercive force on stress are obtained for materials with a C content of 0.17 to 0.9%. In the course of the studies, it was found that the coercive force in the zone of elastic deformation varies by 9-11%. The obtained studies on the characteristics of magnetism make it possible to assess the technical condition of metallurgical equipment.