Defense Date

2022

Document Type

Thesis

Degree Name

Master of Science

Department

Mechanical and Nuclear Engineering

First Advisor

Radhika Barua, Ph. D.

Second Advisor

Karla Mossi, Ph. D.

Third Advisor

Ravi Hadimani, Ph. D.

Fourth Advisor

Everett Carpenter, Ph. D.

Abstract

Additive manufacturing (AM) is an emerging process to fabricate net shape, intricate, engineering components with minimal material waste; however, traditionally it has been largely applied to structural materials. AM of functional materials, such as magnetic materials, has received much less attention and the field is still in its infancy. To date, AM of magnetocaloric regenerators for magnetic refrigeration (an energy-efficient alternative to the conventional vapor-compression cooling technology), remains a challenge. There are several magnetic refrigerator device designs in existence today that are predicted to be highly energy-efficient, on condition that suitable working materials can be developed. This challenge in manufacturing magnetocaloric devices is unresolved, mainly due to issues related to shaping the mostly brittle magnetocaloric alloys into thin-walled channeled regenerator structures to facilitate efficient heat transfer between the solid refrigerant and the heat exchange fluid in an active magnetic regenerator (AMR) cooling device. To address this challenge, we explore the possibility of using extrusion-based additive manufacturing (AM) for 3D printing magnetocaloric structures in this work.

Nominal compositions of LaFexCoySi13-x-y alloys were used for this investigation. The effects of extrusion printing on the composition were evaluated by microstructural, crystal structure, and magnetic characteristics probing. Chemical stability of precursor powders was assessed by simulating partial in-operando conditions of an Active Magnetic Regenerator (AMR) setup where heat transfer fluid (DI water) was circulated through the magnetocaloric structure with the aid of a circulating rig. 3D printed parts were immersed in a beaker setup with room temperature tap water (300ml) placed on a magnetic stirrer to simulate flow. Results were presented as comparisons of precursor powders and 3D printed scaffold in terms of composition as well as magnetic properties. X-Ray Diffractometry (XRD) data showed no changes in the composition of the 3D printed samples with similar amounts LaFeCoSi and α-Fe phases present in the structure. Immersed samples of precursor powders showed introduction of Fe3O4 oxide phases where higher compositions of oxide were seen for samples of longer immersion. Magnetometry data showed degradation of magnetocaloric response in polymer blended 3D printed structures with a ΔSmag decrease of 35% and lowered saturation magnetization (Ms). Water immersed precursor powders showed gradual degradation of ΔSmag­ for longer immersion times as well as lowered Ms with no changes in the curie temperature (Tc) among all the samples. Broadly speaking, this work demonstrated the printability of the magnetocaloric material into a functional regenerator type structure and the poor chemical stability of LaFexCoySi13-x-y alloys.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

5-19-2022

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