Application Of Nanofluids Research Articles

Cooling characteristics of nanofluids in a snowflake and squid fin composite bionic microchannel heat sink

To improve the heat dissipation performance of electronic components, this study proposed a novel biomimetic microchannel design inspired by snowflakes and squid fins. A numerical simulation method was employed to investigate the cooling characteristics of nanofluids at different concentrations within this biomimetic microchannel heat sink. The microchannel is shaped like a snowflake, while the base plate features a biomimetic squid fin structure. The study focused on analyzing the effects of waveform height (amplitude A = 0.1–0.4 mm) and waveform frequency (B = 0.5–2π) on heat transfer performance. The results indicated that when nanofluids flow over a base plate with a wavelength frequency of B = 0.5π, there is a significant enhancement in heat exchange while simultaneously reducing flow resistance. In the microchannel heat sink (A = 0.3 mm, B = π), the thermal conductivity of the nanofluids can be increased by up to 32.56 %, with a maximum comprehensive evaluation index of 1.68. This research provides important guidance for the application of nanofluids and biomimetic microchannels in the thermal control of electronic devices.

From Solid to Fluid: Novel Approaches in Neuromorphic Engineering.

Neuromorphic engineering is rapidly developing as an approach to mimicking processes in brains using artificial memristors, devices that change conductivity in response to the electrical field (resistive switching effect). Memristor-based neuromorphic systems can overcome the existing problems of slow and energy-inefficient computing that conventional processors face. In the Introduction, the basic principles of memristor operation and its applications are given. The history of switching in sandwich structures and granular metals is reviewed in the Historical Overview. Particular attention is paid to the fundamental articles from the pre-memristor era (the 1960s-70s), which demonstrated the first evidence of resistive switching and predicted the filamentary mechanism of switching. Multi-dimensionality in neuromorphic systems: Despite the powerful computational abilities of traditional memristor arrays, they cannot repeat many organizational characteristics of biological neural networks, i.e., their multi-dimensionality. This part reviews the unconventional nanowire- and nanoparticle-based neuromorphic systems that demonstrate incredible potential for use in reservoir computing due to the unique spiking change in conductance similar to firing in neurons. Liquid-based neuromorphic devices: The transition of neuromorphic systems from solid to liquid state broadens the possibilities for mimicking biological processes. In this section, ionic current memristors are reviewed and, the working principles of which bring us closer to the mechanisms of information transmittance in real synapses. Nanofluids: A novel direction in neuromorphic engineering linked to the application of nanofluids for the formation of reconfigurable nanoparticle networks with memristive properties is given in this section. The Conclusion t summarizes the bullet points of the Review and provides an outlook on the future of liquid-state neuromorphic systems.

Enhancing thermal management systems: a machine learning and metaheuristic approach for predicting thermophysical properties of nanofluids

Abstract In thermal engineering, predicting nanofluid thermophysical properties is essential for efficient cooling systems and improved heat transfer. Traditional methods often fall short in handling complex datasets. This study leverages machine learning (ML) and metaheuristic algorithms to predict key nanofluid properties, such as specific heat capacity (SHC), thermal conductivity (TC), and viscosity. By utilizing Artificial Neural Networks (ANN), Support Vector Regression (SVR), Gradient Boosting (GB), and Linear Regression (LR), alongside metaheuristic models like Differential Evolution (DE) and Particle Swarm Optimization (PSO), we achieve superior prediction accuracy compared to traditional models. The integration of these computational techniques with empirical data demonstrates their effectiveness in capturing the complex dynamics of thermofluids. Our results validate the precision of ML and metaheuristic models in predicting nanofluid properties and underscore their potential as robust tools for researchers and practitioners in thermal engineering. This work paves the way for future exploration of ML algorithms in thermal management, marking a significant advancement in optimizing nanofluid applications in industry and research.

Heat and mass transfer in MHD flow of SWCNT and graphene nanoparticles suspension in Casson fluid

AbstractThe exceptional mechanical properties of carbon nanotubes (CNTs) and graphene nanoparticles, particularly their high aspect ratio and flexibility, position them as highly promising materials for the next generation of armor technology. Their incorporation into protective wear, such as bullet‐proof vests, offers the potential for significant improvements in both performance and cost efficiency. By replacing traditional materials with CNTs and graphene, the durability and maintenance of these protective devices could be substantially enhanced, leading to more effective and sustainable solutions for personal safety. This study focuses on the complex phenomena of heat and mass transport within a suspension of CNTs and graphene nanoparticles dispersed in a Casson fluid, particularly under the influence of an applied magnetic field. The analysis begins by reformulating the governing equations using similarity variables to transform them into a dimensionless form to simplify the problem. The resulting dimensionless equations are then solved using the three‐stage Lobatto IIIa finite difference method, a robust numerical technique well‐suited for solving boundary value problems in fluid dynamics. The results of this investigation highlight a significant 78.41% reduction in skin friction when compared with traditional CNT‐water nanofluid systems. This considerable decrease in skin friction not only reveals the superior performance of the CNT‐graphene nanofluid suspension but also opens up new possibilities for the design and development of advanced protective materials. These findings contribute to the growing body of knowledge on nanofluid applications and offer valuable insights for future research in the field of advanced armor technology.

MgO and ZnO nanofluids passive cooling effects on the electricity production of photovoltaic panels: a comparative study

AbstractOverheating of solar panels stands as a pivotal factor that impacts their conversion efficiency. Therefore, implementing cooling for solar panels is a key strategy to enhance the electrical output; due to regulating their thermal properties. This study is set out to examine, experimentally, the back-passive cooling impact of MgO and ZnO water-based nanofluids at volume concentrations of 0.01%, 0.03%, and 0.05% on the thermal and electrical characteristics of polycrystalline silicon solar panels, compared with not cooled and water-cooled panels at the same time and under the same weather conditions. The system design is cost-effective and facilitates the direct contact between the cooling fluids and the photovoltaic system. The experimental results demonstrate that the application of MgO nanofluid introduces more improvement compared to the ZnO nanofluid and conventional water cooling. The electrical efficiency enhancement attains its maximum at a volume concentration of 0.05% with 20.90% and 21.65% for MgO and ZnO nanofluids, respectively, over the non-cooled panel. Simultaneously, at this concentration, the temperature reduction achieved by MgO nanofluid is 20.72%, surpassing the 15.80% reduction achieved by the ZnO nanofluid in comparison with the reference panel.

Electro-osmotic flow instability of viscoelastic fluids in a nanochannel

The study of the complex rheological properties of viscoelastic fluids in nanochannels will facilitate the application of nanofluidics in biomedical and other fields. However, the flow of viscoelastic fluids in nanochannels has significant instabilities, and numerical simulation failures are prone to occur at high Weissenberg numbers (Wi). In this study, the simplified Phan-Thien-Tanner viscoelastic fluid model is solved using the log-conformation tensor approach, and the effects of rheological parameters of the viscoelastic fluid, such as the Weissenberg number (Wi), extensibility parameter (ε), and viscosity ratio (β), on the flow characteristics and flow instability within the nanochannel are investigated. The results indicate that the variation of rheological parameters of viscoelastic fluids has a significant effect on the flow state and flow instability of fluids in nanochannels. When the rheological parameters are in a specific range, the flow velocity and outlet current in the nanochannel exhibit relatively regular periodic fluctuations. As the flow transitions from an up-and-down moving single-vortex state to a symmetric double-vortex state, the average velocity of the central axis in the nanochannel is increased by about 15%. Furthermore, when Wi increases from 150 to 400, the length and height of the vortex increase by 50% and 100%, respectively.

Synergistic enhancement of oil recovery: Integrating anionic-nonionic surfactant mixtures, SiO2 nanoparticles, and polymer solutions for optimized crude oil extraction

Enhanced oil recovery (EOR) methods are essential for optimizing oil extraction from modern reservoirs. This research delved into the synergistic impact of combining anionic and nonionic surfactant mixtures with silica (SiO2) nanoparticles (NPs) in sodium chloride (NaCl) solutions, alongside the added enhancement of polymers, to improve crude oil recovery. The study comprehensively evaluated stability, rheological characteristics, interfacial tension (IFT) behavior, wettability alterations, and EOR experiments using mixtures of sodium dodecyl sulfate (SDS) and triton X-100 (TX-100) surfactants. Scenarios both with and without SiO2 NPs in a base solution containing 3000 ppm NaCl and 2000 ppm xanthan gum (XG) polymer were examined. Core flooding tests were carried out on San-Saba sandstone core specimens with low permeability. The stability tests and dynamic light scattering (DLS) analysis were performed to assess the stability of NPs in low saline-surfactant-polymer solution. It was observed that NPs significantly reduced the IFT between the test solutions and crude oil, with nanofluids exhibiting satisfactory stability at a 0.4 wt% SiO2 NPs concentration. Core flooding studies demonstrated a synergistic interaction between NPs and the binary surfactant-polymer mixture, resulting in substantially greater incremental recovery of oil in comparison with the case of using binary surfactant-polymer combination alone. The mechanisms contributing to EOR with nanofluids, such as IFT reduction and wettability alteration, were explored. Incorporating NPs at concentrations of 0.1, 0.2, and 0.4 wt% led to incremental oil recoveries of 4.01 %, 12.35 %, and 12.73 % of the original oil in place (OOIP), respectively, as opposed to the recovery achieved using only SDS + TX-100 + XG. Consequently, these findings advance the understanding of the potential application of SiO2 NPs in combination with the binary surfactant-polymer mixture as effective chemical EOR agents. Additionally, these insights aid in identifying suitable sandstone reservoirs for nanofluid application, contributing to the optimization of oil recovery strategies.

Numerical Investigation of Thermal Performance Enhancement in a Newly Designed Shell and Tube Heat Exchanger using 〖"TiO" 〗_"2" Nanofluids

This study investigates the use of titanium dioxide (TiO2) nanofluids to enhance the thermal performance of shell and tube heat exchangers. A comparative computational fluid dynamics (CFD) analysis is conducted using water and a 0.5% TiO2 nanofluid. The heat exchanger is modelled using computer-aided design (CAD), with dimensions closely resembling commercial units. The CFD model is validated through a grid-independence study, with a mesh of 4,112,679 elements yielding grid-independent results. The key findings show that the 0.5% TiO2 nanofluid increases the cold fluid outlet temperature by 11.44% compared to water (36.04°C vs. 33.63°C). The average heat transfer coefficient is enhanced by 12.3% when using the nanofluid. The CFD results are consistent with experimental data, with a maximum deviation of 4.2% in the outlet temperatures. This study demonstrates the successful integration of TiO2 nanofluids with an optimized shell and tube heat exchanger design. The novelty lies in the application of nanofluids to improve the thermal performance of industrial heat exchangers. The presented methodology, combining CAD modelling and CFD analysis, provides a foundation for further optimization and experimental validation of nanofluid-enhanced heat transfer systems.

Enhanced nanofluid stability of Zn-doped iron oxide: Applications of ascorbic acid nanofluid in enhanced oil recovery

Ascorbic acid-coated, transition metal-doped Fe3O4 nanoparticles were successfully synthesized via coprecipitation. The synthesized Zn-doped Fe3O4 nanoparticles have an average diameter of approximately 30 nm. These nanoparticles exhibit ferromagnetic properties at room temperature, with the highest saturation magnetization approaching 40 emu/g and decreasing coercivity. The surface was functionalized with ascorbic acid, which served as a surfactant to ensure high dispersibility and stability of the Fe3O4 nanoparticles in a brine solution containing 30,000 ppm NaCl. Zeta potential and interfacial tension (IFT) measurements were conducted to assess the suspension quality, confirming the effectiveness of the ascorbic acid coating in stabilizing the nanoparticles.

Impact of silicon carbide, boron nitride, and zirconium dioxide nanoparticles on ester‐based dielectric fluids

AbstractThis research study investigates the influence of various nanoparticles on the dielectric breakdown voltage, oil dissipation factor, viscosity, and thermal conductivity of nanofluids. Nanofluids were prepared using synthetic ester oil as the base fluid, and three nanoparticles, silicon carbide (SiC), boron nitride (BN), and zirconium dioxide (ZrO2), were added at different concentrations (0.125 wt%, 0.250 wt%, and 0.375 wt%), which are basically the nano‐sized powder that can be blended in the oil. The dielectric breakdown voltage testing was conducted to evaluate the electrical performance of the nanofluids. Additionally, rheological measurements were performed to study the kinematic viscosity, while thermal conductivity was determined using appropriate techniques. The enhancements in each property were evaluated and compared for the different nanoparticle concentrations and types. Previous studies focused only on the investigation of the electrical properties of nanofluids. However, in the present study, the electrical as well as thermo‐physical characterisation of nanofluids is performed and analysed as they directly affect the cooling performance of transformers. The results provide dielectric and thermo‐physical characterisation that exhibit excellent insulation and cooling functionalities and valuable insights into the potential applications of nanofluids as dielectrics in various high‐voltage electrical equipment. ZrO2 and SiC nanoparticles exhibited a reduction in the oil dissipation factor. SiC consistently improved breakdown voltage (Bdv), while ZrO2 nanoparticles showed concentration‐dependent effects, enhancing Bdv at low concentrations but degrading it at higher ones. Unexpectedly, nanoparticle dispersion and lubrication effects can lead to viscosity reductions, countering conventional expectations. Surprisingly, at the highest concentration, the thermal conductivity decreases compared to the lower nano‐concentrations in synthetic ester oil.

Design and theoretical simulations of nano check valve constructed of graphene sheets

The unidirectional flow of nanofluids holds paramount importance in numerous nanofluidic applications. However, there remains a void in the practical implementation of a nano check valve specifically designed for ensuring such unidirectional flow. In this work, a nano check valve consisting of a diaphragm and a valve seat is designed and its forward opening and reverse shutoff processes are investigated using molecular dynamic simulations. Additionally, the effects of the modified groups of the diaphragm of the nano check valve are studied. The results demonstrate that the nano check valve can be opened efficiently under a certain forward differential pressure. Besides the differential pressure, the interaction between diaphragm and water molecules contributes to the opening process. Conversely, the non-bonding interaction between diaphragm and the valve seat prevents the opening. The reverse shutoff simulations reveal that the reverse shutoff function can be achieved under the backward pressure even when the nano check valve is firstly opened. It is observed that the ratio of hydroxyl to hydrogen groups on the edge of diaphragm has a significantly effect on the opening pressure due to the non-bond interaction of diaphragm and water molecules. This suggests that the opening pressure of the nano check valve could be regulated by changing the modifier groups.

Entropy optimization in ternary hybrid nanofluid flow over a convectively heated bidirectional stretching sheet with Lorentz forces and viscous dissipation: A Cattaneo–Christov heat flux model

Bidirectional stretching sheet models can represent surfaces in heat exchangers where fluids flow under continuous deformation. Ternary hybrid nanofluids could be employed in these systems to increase heat transfer rates between fluids in heat exchangers and improve the efficiency of energy conversion processes. In this work, we explore the novel application of a ternary hybrid nanofluid (water with titanium dioxide, cobalt ferrite, and magnesium oxide nanoparticles) for enhanced heat transfer in heat exchangers modeled by a bidirectional stretching sheet. This approach offers a potential advancement over traditional nanofluids (with one or two nanoparticles). Furthermore, we present a comprehensive analysis that incorporates ohmic heating, Cattaneo–Christov heat flux, thermal radiation, viscous dissipation, and irreversibility. The governing equations are transformed into a system of nonlinear ordinary differential equations using appropriate similarity transformations and then solved using the bvp4c solver, a MATLAB built-in function. This study's findings reveal that the Eckert number and radiation parameter increase fluid temperature, while the thermal relaxation parameter leads to a reduction in the temperature of the fluid. It is detected that an increase in magnetic field parameter and volume fraction of [Formula: see text] results in a decline of the skin friction factors in both directions. It is revealed that there is a reduction in the Nusselt number with the rise in Eckert number ([Formula: see text]), and the same number declines at a rate of 0.8252 when [Formula: see text]. It is noticed that the skin friction coefficient declines at a rate of 0.62179204 (in case of x-direction) and 0.621791816 (in case of y-direction), respectively, when the values of magnetic field parameter lie between 0 and 3.5. Furthermore, it is noticed that an upsurge in thermal relaxation parameter results in a fall in the temperature of the fluid.

The physical mechanism of heat transfer enhancement for Al2O3-water nanofluid forced flow in a microchannel with two-phase lattice Boltzmann method

PurposeThe purpose of this paper is to analyze the mechanism of nanofluid enhanced heat transfer in microchannels and promote the application of nanofluids in industrial processes such as solar collectors, electronic cooling and automotive batteries.Design/methodology/approachThe two-phase lattice Boltzmann method was used to calculate the flow and heat transfer characteristics of Al2O3 nanofluids in a microchannel at Re = 50. By comparing the simulation results of pure water, nanofluids without calculated nanoparticle-fluid interaction forces and nanofluids with calculated nanoparticle-fluid interaction forces, the effects of physical properties improvement and interaction forces on flow and heat transfer are quantified.FindingsThe findings show that the nanofluid (φ = 3%, R = 10 nm) increases the average Nusselt number by 22.40% at Re = 50. In particular, 16.16% of the improvement relates to nanoparticles optimizing the thermophysical parameters of the base fluid. The remaining 6.24% relates to the disturbance of the thermal boundary layer caused by the interaction between nanoparticles and the base fluid. Moreover, the nanoparticle has a negligible effect on the average Fanning friction factor. Ultimately, we conclude that the nanofluid is an excellent heat transfer working medium based on its performance evaluation criterion, PEC = 1.225.Originality/valueTo the best of the authors' knowledge, this research quantifies for the first time the contribution of nanoparticle-liquid interactions and nanofluids physical properties to enhanced heat transfer, advancing the knowledge of the nanoparticle's behavior in liquid systems.

Thermal study of single phase nanofluid model using radiative γAl2O3 nanomaterial under Hall current and momentum slip phenomena

The applications of nanofluids frequently occur in thermal insulation, cooling of electronic instruments, chemical engineering and to control the heat transfer during many experimental setups, interaction of nanoparticles with water for plants growth, crop improvement, crop protection, plant biology and biological sciences. Therefore, this research emphasis on the performance of radiated γAl2O3/H2O by adding the influential physical constraints (momentum slip and Hall current). The governing model for the flow through a disk with slippery surface is transformed into the final version via necessary mathematical operations and analyzed the problem numerically. Further, the thermal conductivity is computed using Effective Prandtl Number Model (EPNM) by taking nanoparticles amount up to 0.06%. After careful analysis of the problem, it is examined that when Al2O3 nanoparticles amount added in the range of 0.01%-0.06% then EPN increased from 100.398% to 102.636%, density from 100.298% to 101.786% and dynamic viscosity from 100.742% to 104.823%, respectively. Moreover, the electrical and thermal conductivities varied from 100.3% to 101.811% to 101.65%. The moving dynamics of Al2O3/water can be increased or controlled for [Formula: see text] and [Formula: see text], respectively. The Hall index n from 1.0, 3.0, 5.0, 7.0 strongly opposed the velocity and unsteadiness number slightly favor it. Further, the heat transport rate of Al2O3/water improved from 1.05371 to 1.41891 and the shear drag enhanced absolutely from [Formula: see text] to [Formula: see text] against the high nanoparticles amount.

A review of ceramic nanofluids and their applications

Various heat transfer technologies necessitate effective source-to-sink and sink-to-source heat transfer control. Nanoparticles are one of the hot topics in the industrial industry. It has caught a lot of attention because of its benefits. Nanoparticles are small, with a range of 1–100 nm. Despite their small size, their properties are excellent in terms of thermal properties, heat transfer, tribology properties, and many more. There are many types of nanoparticles, and different types of nanoparticles have their excellent properties and performances. This article mainly focuses on ceramic nanoparticles’ performances, preparation methods, stability, thermophysical properties, and applications. Numerous uses of nanoparticles are made possible in several industries because of their regulated size, surface functionalization, porosity, surface area-to-volume ratio, and excellent heat transfer. Based on the information in the literature, the current contribution intends to describe the most recent advancements in ceramic nanofluids’ preparation, characterization, and stability. This article mainly focuses on ceramic nanoparticles’ performances, preparation methods, stability, thermophysical properties, and applications. The discussion ends with applications of nanofluids, which will guide future work on creating very stable nanofluids.

Nanofluids' thermal assessment: Active and passive control approach

The nanofluids are decomposition of nano-sized metallic particles with base materials maintaining peak thermal properties. Owing to enhanced thermal features, various applications of nanofluids are observed in enhancing energy resources and cooling processes. The objective of current work is exploring the thermal impact of nanofluid associated to the oblique stagnation point flow. The thermal interpretation of nanofluid is subject to active and passive control approach. The heat trnasfer analysis is identified by using convective thermal flow constraints. The Buongiorno nanofluid model is adopted, endorsing the Brownian and thermophoresis consequences. The flow problem is first simplfied intodimensionless form. The numerical computations are performed by using famous shooting scheme with justifiable accuracy. A comparative change in the thermal phenomenon given the passive and active frameworks is presented. It is exmained that heat transfer reduces for stretching ratio parameter. The concentration profile reduces for angle of incidence for both active and passive control approach.

Submegahertz Nucleation of Plasmonic Vapor Microbubbles near a Solid Vertical Boundary.

Laser triggered and photothermally induced vapor bubbles have emerged as promising approaches to facilitate optomechanical energy conversion for numerous applications in microfluidics and nanofluidics. Here, we report an observation of spontaneously triggered periodic nucleation of plasmonic vapor bubbles near a rigid sidewall with readily tuned nucleation frequency from 0.8kHz to over 200kHz. The detailed collapsing process of the vapor bubbles was experimentally and numerically investigated. We find that the lateral migration of residual bubbles toward the sidewall refreshes the laser spot area, terminates the subsequent steady bubble growth, and leads to the repeatable bubble nucleation. A mathematic model regarding the Kelvin impulses was derived. It shows that the competition between the rigid boundary induced Bjerknes force and laser irradiation caused thermal Marangoni force on collapsing bubbles governs the process. The model also leads to a criterion of γζ<0.34 for repeatable bubble nucleation, where γ is the normalized distance and ζ thermal Marangoni coefficient. This study demonstrates nucleation of violent vapor bubbles at extreme high frequencies, providing an approach to remotely realize strong localized flows in microfluidics and nanofluidics.

Unveiling the Triple Diffusion Bioconvective Applications for Couple Stress Nanofluid Due To an Oscillating Regime with Variable Thermal Features

Thermal engineering and industrial processes see various multidisciplinary applications due to the enhanced thermal performances of nanomaterials. The nanomaterials preserve a profound breakthrough in enhancing the heat transfer phenomenon. The objective of the current investigation is to address the thermal applications of couples-stress nanofluid in the presence of triple diffusion effects. The analysis is subject to the bioconvective significance of the suspension of microbes. The viscosity and thermal conductivity of a couple stress fluids are assumed to be variable. Moreover, we endorse linear thermal radiation effects and approach the problem with an effective Prandtl number. The source of flow is an oscillatory, porous stretching surface. Based on suggested flow assumptions, the model is represented via nonlinear couple partial differential equations (PDEs). We employ the homotopy analysis scheme to forecast the analytical simulations. The physical outcomes for the involved parameters are observed for the modeled problem. Various aspects based on the deduced results are claimed. Based on the performed analysis, it is observed that the magnitude of skin friction decreases due to variations in the couple-stress fluid parameter. The heat increases with the modified Dufour number and variable thermal conductivity coefficient. Furthermore, an increasing behavior of nanoparticle solutal concentration has been observed due to the Dufour-Lewis number.

Visualization investigation on heat and mass transfer of Al2O3 nanofluid in vapor chamber

As the vapor chamber (VC) moves towards ultra-thinness to meet the thermal management of microelectronic devices, achieving efficient heat transfer within a limited space poses severe challenges. In this study, a visualization VC with a thickness of only 0.9 mm was designed to investigate the heat transfer effect and boiling behavior of nanofluid applied on VC. The influences of Al2O3-deionized water (Al2O3-DW) with different mass concentrations and filling ratios on the heat transfer characteristics and flowing behavior were explored. The results indicated that the addition of nanoparticles improved the temperature uniformity and startup performance of VC. At 0.3 wt%, nanofluid promoted bubbles generation and growth, enhancing the phase-change process. The minimum thermal resistance was 1.46 K/W, representing a 13.6 % reduction compared to that of DW. However, at 0.6 wt% and under high filling ratios or heat load, excessive nanoparticles tended to accumulate on the surface of bubbles by surface tension during the boiling process and were pushed to the gas–liquid interface under the pressure gradient, resulting in deteriorated heat transfer. The results also found that deposition of nanoparticles further enhanced heat transfer. Nonetheless, the nanoparticles were detached from the substrate as the bubbles boiled, and the enhancement effect gradually diminished. The relevant research findings provide guidance for the application of nanofluids in ultra-thin VC.

Synthesis of aqueous NiFe2O4-Fe3O4 hybrid magnetic nanofluids and investigation on electrical conducting behaviour

Highly stable aqueous magnetic mono nanofluids of nickel ferrite (NiFe2O4), magnetite (Fe3O4), and hybrid magnetic nanofluids of NiFe2O4-Fe3O4 are synthesized through a two-step method. The structural analysis of the NiFe2O4 and Fe3O4 nanoparticles made through X-ray diffraction identifies their spinel cubic structure. The magnetic studies indicate their superparamagnetic nature, which is further confirmed through the Langevin fitting of the experimental data. The monodomain nature of nanoparticles is verified using the coupling constant, and a spherical morphology is observed using a transmission electron microscope. The surface charge of the nanoparticles is studied through zeta potential analysis. The electrical conductivity of the aqueous mono and hybrid magnetic nanofluids is measured for various concentrations and temperatures. The hybrid magnetic nanofluids show higher electrical conductivity values than those of both the mono nanofluids. For instance, NiFe2O4-Fe3O4 (1.2 vol%) hybrid nanofluid is found to have a conductivity value of 18.91 μS/cm that is 1.5 times enhanced than that of Fe3O4 mono nanofluid (12.87 μS/cm) and three times enhanced than that of NiFe2O4 (6.43 μS/cm) mono nanofluid of same volume percentage at 303 K. A Maximum enhancement of 136 % is obtained for 1.2 vol% hybrid nanofluid with respect to water at 303 K and this enhancement further increases to 196 % with the rise in temperature to 323 K. There is no theoretical model found in literature to explain the electrical conductivity of hybrid nanofluids. Maxwell, Bruggeman, Cruz, and Shen models are applied to explain the conductivity of hybrid magnetic nanofluids. Through a comparison of experimental values with theoretical values, it is found that the Shen model, if modified suitably, can explain the electrical conduction of hybrid magnetic nanofluids. Also, the electrical conduction mechanism in hybrid magnetic nanofluids is described in terms of electrophoretic charge transportation and the Brownian motion. In addition, the magneto-electrical conductivity study is performed by measuring the electrical conductivity by applying a magnetic field of various strengths. The electrical conductivity, magneto-electrical conductivity studies and an understanding of electrical conduction mechanism are highly significant for magnetically transportable electronic cooling and conducting applications of hybrid magnetic nanofluids.