Experimental Thermal Conductivity Studies of Agar-Based Aqueous Suspensions with Lignin Magnetic Nanocomposites

Author(s)

Bishal Gautam, University of Dayton
Saja M. Nabat Al-Ajrash (0000-0002-0147-991X), University of Dayton
Mohammad Jahid Hasan, University of Texas at San Antonio
Abhishek Saini, University of Cincinnati
Sarah J. Watzman (0000-0002-5244-2340), University of Cincinnati
Esteban Ureña-Benavides (0000-0002-5525-488X), University of Texas at San Antonio
Erick S. Vasquez-Guardado (0000-0002-4811-6155), University of Dayton

Document Type

Article

Publication Date

2-10-2024

Publication Source

Magnetochemistry

Abstract

Nanoparticle additives increase the thermal conductivity of conventional heat transfer fluids at low concentrations, which leads to improved heat transfer fluids and processes. This study investigates lignin-coated magnetic nanocomposites (lignin@Fe₃O₄) as a novel bio-based magnetic nanoparticle additive to enhance the thermal conductivity of aqueous-based fluids. Kraft lignin was used to encapsulate the Fe₃O₄ nanoparticles to prevent agglomeration and oxidation of the magnetic nanoparticles. Lignin@Fe₃O₄ nanoparticles were prepared using a pH-driven co-precipitation method with a 3:1 lignin to magnetite ratio and characterized by X-ray diffraction, FT-IR, thermogravimetric analysis, and transmission electron microscopy. The magnetic properties were characterized using a vibrating sample magnetometer. Once fully characterized, lignin@Fe₃O₄ nanoparticles were dispersed in aqueous 0.1% w/v agar–water solutions at five different concentrations, from 0.001% w/v to 0.005% w/v. Thermal conductivity measurements were performed using the transient line heat source method at various temperatures. A maximum enhancement of 10% in thermal conductivity was achieved after adding 0.005% w/v lignin@Fe₃O₄ to the agar-based aqueous suspension at 45^◦C. At room temperature (25^◦C), the thermal conductivity of lignin@Fe₃O₄ and uncoated Fe₃O₄ agar-based suspensions was characterized at varying magnetic fields from 0 to 0.04 T, which were generated using a permanent magnet. For this analysis, the thermal conductivity of lignin magnetic nanosuspensions initially increased, showing a 5% maximum peak increase after applying a 0.02 T magnetic field, followed by a decreasing thermal conductivity at higher magnetic fields up to 0.04 T. This result is attributed to induced magnetic nanoparticle aggregation under external applied magnetic fields. Overall, this work demonstrates that lignin-coated Fe₃O₄ nanosuspension at low concentrations slightly increases the thermal conductivity of agar aqueous-based solutions, using a simple permanent magnet at room temperature or by adjusting temperature without any externally applied magnetic field.

ISBN/ISSN

2312-7481

Document Version

Published Version

Comments

Copyright © 2024 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

https://doi.org/ 10.3390/magnetochemistry10020012

Publisher

MDPI

Volume

10

Peer Reviewed

yes

Issue

2

Keywords

lignin@Fe3O4, lignin nanocomposites, thermal conductivity measurements, magnetic nanoparticles, lignin, transient line heat source method

eCommons Citation

Gautam, Bishal; Al-Ajrash, Saja M. Nabat; Hasan, Mohammad Jahid; Saini, Abhishek; Watzman, Sarah J.; Ureña-Benavides, Esteban; and Vasquez-Guardado, Erick S., "Experimental Thermal Conductivity Studies of Agar-Based Aqueous Suspensions with Lignin Magnetic Nanocomposites" (2024). Chemical and Materials Engineering Faculty Publications. 243.
https://ecommons.udayton.edu/cme_fac_pub/243