Correlating the Dipolar Interactions Induced Magneto‐Viscoelasticity and Thermal Conductivity Enhancements in Nanomagnetic Fluids

Abstract

The effective thermal management of electronic system holds the key to maximize their performance. The recent miniaturization trends require a cooling system with high heat flux capacity, localized cooling, and active control. Nanomagnetic fluids (NMFs) based cooling systems have the ability to meet the current demand of the cooling system for the miniaturized electronic system. However, the thermal characteristics of NMFs have a long way to go before the internal mechanisms are well understood. This review mainly focuses on the three aspects to establish a correlation between the thermal and rheological properties of the NMFs. First, the background, stability, and factors affecting the properties of the NMFs are discussed. Second, the ferrohydrodynamic equations are introduced for the NMFs to explain the rheological behavior and relaxation mechanism. Finally, different theoretical and experimental models are summarized that explain the thermal characteristics of the NMFs. Thermal characteristics of the NMFs are significantly affected by the morphology and composition of the magnetic nanoparticles (MNPs) in NMFs as well as the type of carrier liquids and surface functionalization that also influences the rheological properties. Thus, understanding the correlation between the thermal characteristics of the NMFs and rheological properties helps develop cooling systems with improved performance.

Multifaceted properties of TiO2 nanoparticles synthesized using Mangifera indica and Azadirachta indica plant extracts: antimicrobial, antioxidant, and non-linear optical activity investigation for sustainable agricultural applications

“…39 However, non-conventional methods, such as microfluidic reactors, microwave-assisted synthesis, and sonochemical synthesis, have gained recognition for their efficiency, speed, and eco-friendliness. 40 Although conventional methods provide a sturdy foundation, non-conventional methods offer promising avenues for innovation and customization. 41 In our study, we prefer conventional methods rooted in the pursuit of well-defined, reproducible results.…”

Incidence of the Brownian Relaxation Process on the Magnetic Properties of Ferrofluids

“…This model has its limitations: both the distribution of particle size and interactions between particles can result in deviation from the proposed behavior, and the expressions usually used for describing characteristic times are only valid in small magnetic fields. Despite all these limitations, the relaxation time approximation seems to describe dilute ferrofluids with well-defined particle sizes quite accurately [1,13,14].…”

“…Néel relaxation is different as it originates from the magnetic anisotropy energy and is present in both liquid and solid phases (above the so-called blocking temperature, which can be thought of as a temperature threshold, above which the thermal energy overcomes the magnetic energy barrier between preferred directions) [15]. The time scale of this mechanism depends exponentially on both the inverse temperature and the particle size, resulting in drastically varying relaxation time values [13,14,16].…”

“…This, in turn, is governed by the two different aforementioned relaxation processes. In the first one, the particle is static and its magnetization rotates (known as the Néel process), and in the second one, the entire particle rotates (known as the Brownian process) while its magnetization is unchanged with respect to the particle [14]. The first one is typical for smaller particles (typically with diameters below 10 nm, this value is dependent both on the atomic structure and the geometry of the nanoparticles), and the second one occurs for larger particles [1,13,17,18].…”

“…Temperature-and magnetic-field-dependent studies in nanomagnetic ferrofluids have focused mostly on Néel-dominated samples [5,9,16,[19][20][21][22][23][24] using DC magnetometry, with a limited effort for larger particles with Brownian relaxation [8,9,21]. These effects were also theoretically studied for various models, including ferrohydrodynamics [1,5,14,25,26], the Fokker-Planck equation [27], or the egg model using the Landau-Lifsitz-Gilbert theory [21,28,29]. The most common approach in the investigation of dilute ferrofluids is to use linear response theory [21], but it is also possible to consider higher-order terms in the magnetic response [29].…”