Highest Thermal Conductivity Enhancement Research Articles

Flexible Composite Films with Ultrahigh Through-plane Thermal Conductivity yet Low Graphene Content

Graphene-based polymeric composites have become one of the promising thermal interface materials (TIMs) for the high integration electronic devices due to the excellent intrinsic thermal conductivity of graphene. However, the challenges still remain, such as ordered alignment of graphene in elastic polymer and regulation of phonon scattering at graphene/graphene interface. In this study, a vertically oriented graphene framework within a flexible silicone rubber matrix was fabricated by non-solvent induced phase separation (NIPs) coupled with an in in-situ welding technique. The as-prepared film exhibits an outstanding through-plane thermal conductivity of 29.5W/mK at low graphene loading of 7.5wt%, which indicates an exceptionally high thermal conductivity enhancement per 1wt% graphene content (specific TCE) over 1950%/wt%. Furthermore, the composite films demonstrate excellent conformability inherited from the silicone rubber matrix and achieves low contact resistance of 40-70 Kmm2W−1 under various pressure and interfacial conditions. This study contributes to a deeper insight into the development of the high-performance graphene-based polymeric TIMs.

MHD nonlinear thermally radiative Ag − TiO 2/H 2 O hybrid nanofluid flow over a stretching cylinder with Newtonian heating and activation energy

Hybrid nanofluids are significant in biomedical, industrial, transportation, as well as several engineering applications due to their high thermal conductivity and mass transfer enhancement nature in contrast to regular fluids and nanofluids. Taking this into consideration, the present problem explores the flow of hybrid nanofluid (Ag − TiO 2/H 2 O) over a stretching cylinder subject to Newtonian heat and mass conditions. The novel aspect of the current work is to analyze the heat and mass transfer characteristics of MHD hybrid nanofluid flow on Darcy-Forchheimer porous medium in addition to activation energy, nonlinear thermal radiation, heat generation/absorption, viscous and Joulian dissipation. Further, Silver (Ag) and Titanium oxide (TiO 2) are the constituent nanoparticles of the water-based hybrid nanofluid owing to their stable chemical features and extensive industrial manufacturing. By introducing suitable similarity transformations, the governing partial differential equations (PDEs) of the developed model are reduced to ordinary differential equations (ODEs), and then the numerical solution is procured with shooting technique by using MATLAB solver bvp4c. The influence of the pertinent parameters is depicted graphically and described elaborately. The analysis indicates that velocity exhibits a declining trend against the permeability and Forchheimer parameters, while the temperature profiles show opposite behavior. The radiation and conjugate heat parameters (R, γ 1) upgrade the heat transfer rate, while the curvature and conjugate mass parameters (α c , γ 2) amplify the mass transfer rate. The maximum heat transfer rate of Ag − TiO 2/H 2 O hybrid nanofluid is 2.3344 attained for γ 1 = 0.6. The investigation demonstrates larger heat and mass transfer rates for Ag − TiO 2/H 2 O hybrid nanofluid than Ag − H 2 O nanofluid. The outcomes of the present investigation have practical applications in conjugate heat transfer over fins, development of vaccines, effluent treatment plants, solar cells, heat exchangers, and many more. An excellent agreement is achieved on comparing our numerical results with the published results in the literature.

Synthesis and thermophysical property characterization of aqueous graphene quantum dot dispersions for air-conditioning applications

Air-conditioning systems are on track to demand most of the electricity consumed by buildings around the world. The authors propose that dispersing quantum dots into the chilled water loops of air-conditioners represents a path towards improving the efficiency of air-conditioners. As such, the thermophysical properties of carbon-based quantum dot ‘nanofluids’ (e.g., nanoparticles dispersed in liquids) are presented in this study for sub-ambient temperatures (5–15°C)—an under-explored temperature range which requires understanding for air-conditioning applications. This study also explores dispersion stability and materials compatibility—another under-explored area in the literature which is required for commercial uptake. In this study, carbon quantum dots were synthesized via the hydrothermal route and characterized with UV–Vis, FT-IR, Raman spectroscopy, and TEM. Next, the thermophysical properties of specific heat capacity, thermal conductivity, and viscosity of the nanofluids were experimentally measured between 5 and 15°C (not previously reported for aqueous quantum dots). The highest thermal conductivity enhancement was ∼11% (compared to DI water) for 0.3 wt.% at ∼11 °C. Finally, the stability of the fluid was monitored over time and after exposing the fluids to common materials used in air-conditioning systems (e.g., copper, brass, and stainless steel). Unchanged UV–Vis spectra and the lack of sedimentation indicate that the developed dispersions are indeed suitable for chilled water air-conditioning applications.

Thermo-optical characterization of novel MXene/Carbon-dot hybrid nanofluid for heat transfer applications

Nanofluid has emerged as a promising heat transfer fluid (HTF) due to their significant thermophysical, and optical characteristics enhancement over base fluids. Hybrid nanofluids with multiple nanomaterials have the advantage of synergistic properties in comparison to monocomponent nanofluids. The present study proposes an energy-efficient and cleaner synthesis method for developing carbon quantum dot (C-dot), MXene, and a hybrid MXene/C-dot hybrid nanofluids, for heat transfer application. In-situ microwave pyrolysis technique and two-step method were adopted for nanomaterial and nanofluid synthesis. The morphological, phase structural, chemical, and elemental compositional analysis of the nanomaterials was performed. The material characterization confirms the hybridization of C-dot on MXene nanosheets. The thermal conductivity and volumetric heat capacity of the nanofluids were measured using the transient plane source (TPS) method. Thermal conductivity was observed to increase with nanofluid concentration and temperature. Results indicate that MXene has the highest thermal conductivity enhancement (50 %) over water, followed by hybrid (42.2 %) and C-dot nanofluid (33.2 %). The volumetric heat capacity of nanofluids decreased with concentration and temperature. A semi-empirical correlation, as a function of nanofluid concentration and temperature, was coined for predicting thermal conductivity and volumetric heat capacity. Optical property characterization study shows that C-dot nanofluid exhibited considerable absorption along the UV range, while MXene nanofluid showed absorption in the visible and near-infrared (NIR) region. Hybrid nanofluids demonstrated complementary absorption properties of C-dot and MXene nanofluids.

Binary nitrate molten salt magnetic microcapsules modified with Fe3O4-functionalized carbon nanotubes for accelerating thermal energy storage

Molten salts are important media for heat transfer and thermal energy storage in concentrated solar power (CSP) system, but it has drawbacks such as poor thermal conductivity and corrosive properties. This study increases the thermal energy utilization rate and expand the range of applications for phase change materials by developing a multifunctional magnetic microcapsule phase change material composed of SiO2@Solar Salt microcapsule and Fe3O4-functionalized carbon nanotubes (CNTs-Fe3O4). The microcapsules have regular spherical core-shell structure and relatively small size, which improves the disadvantage of corrosiveness of molten salt and prolongs their working life. The microcapsule not only shows a good latent heat-storage capability with satisfactory phase-change enthalpies of over 88.6 J/g under an encapsulation efficiency of over 61.6 %, but also exhibits high temperature stability and cycling stability. The encapsulation of SiO2 and introduction of the CNTs-Fe3O4 high thermal conductivity enhancement phase increased the thermal conductivity of the microcapsules by approximately 53.4 % compared with pure nitrate. The microcapsules also possess superparamagnetic characteristics and photothermal conversion characteristics, both of which may be used as an additional method to improve the thermal storage efficiency. As a result, this novel material provides a promising solution for energy collecting, conversion, and storage.

Thermal Interface Engineering in a 3D-Structured Carbon Framework for a Phase-Change Composite with High Thermal Conductivity.

Phase-change materials (PCMs) are promising thermal storage medium for thermal management due to their efficient thermal energy harvesting capabilities. However, the low thermal conductivity (TC) and poor shape stability of PCMs have hindered their practical applications. Construction of an interconnected three-dimensional (3D) heat-conductive structure is an effective way to build phonon conduits and provide PCM confinement. Phonon scattering at the interface is an unavoidable effect that undermines the TC improvement in the PCM composite and necessitates careful engineering. This study focuses on creating a highly thermally conductive 3D carbon-bonded graphite fiber (CBGF) network to enhance the TC of the PCM, with attention especially on thermal interface engineering considering both filler-matrix (F-M) and filler-filler (F-F) interfaces. The composite with an optimized proportion of F-M and F-F interface area achieves the highest TC of 45.48 W·m-1·K-1, which is 188.5 times higher than that of the pure PCM, and a high TC enhancement per volume fraction of the filler (TCEF) of 831% per 1 vol % loading. This also results in an enhanced spatial construction for PCM confinement during the phase change. The results emphasize the significance of interface engineering in creating high-TC and form-stable phase-change composites, providing insightful guidance for rational structural design.

Thermal conductivity of hydraulic oil-GO/Fe3O4/TiO2 ternary hybrid nanofluid: Experimental study, RSM analysis, and development of optimized GPR model

In the present paper, the thermal conductivity (TC) of a hydraulic oil-based nanofluid in the presence of ternary nano-additives, graphene oxide (GO), iron oxide (Fe3O4), and titanium dioxide (TiO2), is analyzed in a wide range of volume fractions (VFs), temperatures, and mixing ratios (MRs). The stability of ternary hybrid nanofluids (THNFs) and size distribution of nanomaterial is obtained through zeta potential and dynamic light scattering (DLS) tests. Zeta potential and DLS tests indicated the remarkable stability of the samples with the GO(2): Fe3O4(1): TiO2(1) MR. Analysis of the measurements revealed that the enlargement in temperature and VFs improved the TC of THNFs for all MRs (1:1:1, 2:1:1, 1:2:1, 1:1:2). The highest TC enhancement is observed at the highest temperature (65 °C) and VF (1%), which for the MRs of 1:1:1, 1:1:2, 1:2:1, and 2:1:1 equal to 36.04%, 26.28%, 25.95%, and 33.86%, respectively. Furthermore, considering the average TC enhancement in the presence of nano-additives for various temperatures, MRs of GO(1): Fe3O4(1): TiO2(1) and GO(1): Fe3O4(1): TiO2(2) indicated the best and worst efficiency with 30.46% and 22.01%, respectively. The RSM method is applied to provide a simple and efficient formula-based model to describe the TC of THNFs in terms of input variables. In addition, a novel genetic algorithm-based optimization of training/structure parameters of Gaussian process regression (GPR) as a leading machine learning algorithm is developed, which provided thoroughly precise outcomes (Rtest2=0.9994 and Rtrain2=0.9998) for the prediction of TC of THNFs. The sensitivity analysis for the present THNFs revealed that the TC sensitivity is maximized at the highest VF and temperature.

Mussel-inspired strategy to construct 3D silver nanoparticle network in flexible phase change composites with excellent thermal energy management and electromagnetic interference shielding capabilities

Nowadays, efficient thermal management and electromagnetic interference shielding as effective measures for maintaining the normal operation of electronic devices are extremely significant. However, composites with both thermal management and electromagnetic interference shielding performance are rarely reported. In this study, a kind of flexible polydopamine (PDA) and silver nanoparticles (AgNPs) wrapped melamine foam (MF) constructed by adopting the mussel-inspired strategy was used to fabricate MPAχ-PEG phase change materials (PCMs) via encapsulating polyethylene glycol (PEG). PDA was selected to enhance the interface bonding between MF and AgNPs due to its strong adhesion based on mussel-inspired surface chemistry. Continuous AgNPs wrapped on skeleton of MF construct the three-dimensional (3D) thermal/electrical-conductive porous network. MPAχ-PEG PCMs exhibit a relatively high phase change enthalpy of 148.9 J/g and a high thermal conductivity enhancement of 1400% in comparison with that of MF-PEG. Moreover, MPAχ-PEG PCMs are provided with electromagnetic interference (EMI) shielding performance with the mean SET of 82.02 dB and electro-to-thermal energy conversion efficiency (86.3% under the voltage of 1.2 V) due to the 3D conductive AgNPs network. Combining the elasticity of MPAχ foams and the phase change feature of PEG, the MPAχ-PEG PCMs show good solar-induced shape memory performance. The flexible PCMs could avoid the sharp temperature increase of smartphone by the solid-liquid phase change process of PEG. Therefore, this study provides a promising strategy to prepare flexible PCMs, which can achieve various forms of energy conversion, as well as thermal management and EMI shielding performance, can definitely broaden their application prospect in electronic devices.

Unidirectional thermal conduction in electrically insulating phase change composites for superior power output of thermoelectric generators

Owing to their ability to absorb excess heat within narrow temperature ranges, phase change materials (PCMs) have attracted significant interest in the thermal management of power equipment and energy devices. However, the low thermal conductivity of PCMs severely limit their application in high-power devices. Current methods for increasing the thermal conductivity are generally at the cost of lowering the phase change enthalpy (i.e., latent heat) of PCMs. In this study, we developed phase change composites (PCCs) based on highly oriented aramid nanofiber/boron nitride nanosheets (ANF/BNNS) aerogels impregnated with paraffin; the aerogels were prepared by unidirectional freeze-drying method and were impregnated with the PCM, namely, paraffin, by a vacuum assisted method. The ANF/BNNS PCCs exhibited high thermal conductivity enhancement efficiency (TCEE), ultra-high latent heat retention, and superior electrical insulation. For a loading of 2.21 wt% BNNS, the TCEE and the latent heat retention of the PCCs reached impressive values of 89.2%, and 93.64%, respectively. In addition, the PCCs are highly electrically insulating with an electrical conductivity of <1.17 × 10−14 S cm−1. The PCCs also maintain good shape stability even at temperatures higher than the melting point of the PCM (i.e., paraffin). The ANF/BNNS PCCs were shown to reduce the cold-side temperature of thermoelectric generators by more than 10 °C in comparison to that achieved by those operated by air-cooling, resulting in an approximately 300% increase in power output. These PCCs, with both high latent heat retention and TCEE, offer new opportunities for use as advanced thermal management materials in future high-power devices.

Significantly enhanced thermal conductivity of polymer composites via establishing double-percolated expanded graphite/multi-layer graphene hybrid filler network

Utilization of hybrid fillers with high thermal conductivity enhancement (TCE) efficiency is an effective method for the large-scale fabrication of polymeric thermal interface materials (TIMs) with exceptional thermal conductivity. Herein, we report the thermally conductive properties of thermoplastic urethane (TPU) composites incorporated with expanded graphite (EG) and multi-layer graphene (MLG). The effect of percolation behavior of EG/MLG hybrid fillers on the thermal conductivity is systematically revealed. It is found that the high-loading TPU composite with 20 wt% EG and 10 wt% MLG reveals an exceptional thermal conductivity of 8.52 Wm−1K−1, which corresponds to a TCE of 3450% compared to that (0.24 Wm−1K−1) of pure TPU matrix. Notably, the TCE per 1 wt% filler reaches a substantial value of 115%. The thermally conductive mechanism is proposed based on morphology and thermal contact resistance analyses. Moreover, the application of such TPU composites in thermal management of light-emitting diode lamps is exhibited, and the effectiveness is further verified through finite element simulation. Our results shed light on the significant thermal synergy between EG and MLG and demonstrate their application potential in high-performance TIMs.

Efficient synthesis of regular spherical GO/SiO2@Solar Salt microcapsules to enhance heat-storage capacity and cycle stability

The sol–gel method was used to overcome the disadvantages associated with the high water solubility of molten salt into advantages, and a W/O emulsion system was constructed. The interfacial polymerization reaction was initiated by ammonium hydroxide to generate a SiO2 shell layer, which served as a microcontainer for Solar Salt to prepare more stable regular spherical microcapsules with a diameter of 886 nm. Meanwhile, the oxygen-containing functional groups on the surface of graphene oxide (GO) were combined with the shell of the SiO2@Solar Salt phase-change heat-storage microcapsule through shared electron pairs and hydrogen bonds, such that they were uniformly distributed on the GO layer. The synthesized composite material exhibited a typical morphology of microcapsules with a core–shell structure uniformly loaded on the sheet. This study proves that the encapsulation of SiO2 and introduction of the high thermal conductivity enhancement phase increased the thermal conductivity of the microcapsules by approximately 45% compared with pure nitrate and maintained a high specific heat capacity of 1.44 J/(g·K). In addition, the microcapsules exhibited excellent photothermal conversion efficiency, effectively absorbing visible light and increasing the heat storage rate. The addition of GO nanosheets and SiO2 increased the structural stability of the composite material and its cycle life. Owing to the exquisite composite structure, the structural composition of the microcapsule remained unchanged after 500 thermal cycles, maintaining 98.5% latent heat, 99% heat capacity, and good thermal conductivity. This study provides a new solution for the efficient microencapsulation of molten salt heat storage materials.

Spider Web-Inspired Graphene Skeleton-Based High Thermal Conductivity Phase Change Nanocomposites for Battery Thermal Management

HighlightsA three-dimensional spider web-inspired structured graphene skeleton is constructed.The spider web-like skeleton endows paraffin wax with a significantly high longitudinal and transverse thermal conductivity enhancement of ~1260% and ~840%, respectively, at 2.25 vol% skeleton.The resultant composites exhibit outstanding performance on the thermal management of Li-ion batteries.

Novel use of MgO nanoparticle additive for enhancing the thermal conductivity of CuO/water nanofluid

The present work aims to address the low thermal conductivity of CuO/water nanofluid due to the spherical shape of CuO nanoparticles by adding small amount of magnesium oxide (MgO) nanoparticles to the nanofluid. Novel CuO–MgO/water hybrid nanofluid has been synthesised and studied at different volume concentrations (0.125–1.25%) of 80% CuO and 20% MgO nanoparticles suspended in water at different range of temperatures from 25 to 50 °C on its thermal conductivity. The study demonstrated that increasing volume concentration of nanoparticles has enhanced the thermal conductivity, but drops slightly when the volume concentrations are above 1%. Furthermore, the results showed that the effect of temperature on thermal conductivity enhancement is similar to the effect of volume concentration, especially at higher temperatures. The highest enhancement of thermal conductivity of 16% was achieved at volume concentration of 1.25% and temperature of 50 °C. Furthermore, sensitivity analysis showed that the optimum condition to prepare the CuO–MgO/water hybrid nanofluid could be used in industrial applications at volume concentration of 0.75% and temperature of 50 °C. Finally, the study proposed an empirical correlation to measure the thermal conductivity of CuO–MgO/water hybrid nanofluid based on data experiments results.

Synergistic effect of carbon nanotubes and wood-derived carbon scaffold on natural rubber-based high-performance thermally conductive composites

Construction of three-dimensional (3D) heat-conductive network in polymer matrix is essential to effectively transport heat in thermal management materials, but the preparation process remains challenging. In this study, a continuous 3D interconnected filler network was designed and fabricated by incorporating 1D carbon nanotubes (CNT) into 3D wood-derived carbon scaffold (CS), using natural rubber (NR) as a model matrix. The CS/CNT/NR composite exhibited high thermal conductivity (1.1 W m−1 K−1) at 1.67 vol% CNT loading, corresponding to high specific thermal conductivity enhancement (TCE) of 444 %. Importantly, a synergistic effect between CS and CNT was revealed, which played a pivotal role in forming the heat percolation network. These results demonstrate that CS/CNT/NR composite has potential applications in the field of thermal management materials. Compared with similar NR-based thermal management materials, the unique 3D interconnected structure of CS/CNT/NR composite ensures high-speed heat transport. Moreover, the use of biomass materials is an effort devoted for promoting renewable materials and sustainable environment. This work provides new insights into the biomimetic design of efficient 3D filler structure and expands the utilization of wood structure in thermal management materials for efficient heat dissipation.

Carbon nanofillers repair strategy for high-efficiency thermal conductivity enhancement of PBX composites at ultralow mass fraction

Owing to the existence of structural defects of nanofillers and interfacial thermal resistance, realizing high efficiency thermal conductivity (k) enhancement of polymer composites by high k fillers at low mass fraction has proven challenging. Here, aroused by the repair of natural spider web, we reported a novel strategy to mend the structural defects of carbon nanofillers (CNFs) via selective deposited of Ag nanoparticles. The morphology and microstructure of obtained CNFs@Ag were detailed characterized. With a filler loading of 0.5 wt%, a high-efficiency k enhancement had been achieved. The k of PBX composites could reach to 0.722 W/mK, enhanced by 70% compared with pure PBX. Importantly, the temperature gradient and thermal stress distribution in PBX cylinder when facing complicated thermal changes were evaluated by finite element analysis. The study here sheds new light on enhancement of thermal conductivity of polymer composites which severely limits the content of fillers using.

Novel micro-nano epoxy composites for electronic packaging application: Balance of thermal conductivity and processability

Epoxy (EP) composites with comprehensive good processability, low coefficient of thermal expansion (CTE), and high thermal conductivity, but electrical insulation properties are largely demanded in the higher power electric devices. However, micro-fillers have a positive effect on maintaining the good flowability of epoxy composites, while do not bring high thermal conductivity enhancement per unit mass. While nano-fillers with high specific surfaces offer very promising opportunities for heat-conducting network construction, but the nano-fillers dispersion is difficult to control and will cause increased viscosity and processing difficulties. Herein, we expect that the addition of small amounts of silver nanowires (AgNWs) at 0.5 vol% into the EP/S-Al2O3 composites could largely enhance the thermal conductivity but not sacrifice their processability. Owing to the bridging effects of rigid nanowires between the main spherical particles, the thermal conductivity of the micro-nano EP/AgNWs/S-Al2O3 composites with 40 vol% S-Al2O3 and 0.5 vol% AgNWs exhibits a 106.5% increment comparing to that without AgNWs. The limitation of both single micro or nano-sized thermal conductive fillers can be offset by the micro-nano filler network structure. The best combination properties of the EP/AgNWs/S-Al2O3 composites can reach the high thermal conductivity (1.602 W/m·K), low viscosity (55.6 Pa s), low CTE (37.1 ppm/°C), and high glass transition temperature (Tg, 152.1 °C). These results demonstrate that adding multiscale fillers into epoxy composites may solve the tradeoff between thermal conductivity and processability performances and fit the applications in high-power density electronic devices.

Enhanced thermal conductive and mechanical properties of thermoresponsive polymeric composites: Influence of 3D interconnected boron nitride network supported by polyurethane@polydopamine skeleton

Polymeric composites with excellent thermal conductivity are in high demand in modern electronics because of their need for efficient heat dissipation. Whereas, the thermally conductive polymeric composites usually be limited by the insufficient effectiveness of the thermally conductive pathway, at the cost of high filler content and deterioration of mechanical strength. At the same time, they lack multi-functionality. Here, we reported advanced thermoresponsive polymeric composites containing a three-dimensional interconnected boron nitride (BN) network, which simultaneously displayed high thermal conductivity enhancement, thermal transfer performance, improved shape memory, and mechanical properties. Manufactured composites on the basis of commercial polyurethane sponges which were modified by polydopamine and coated with BN through dip-coating assemble method and the subsequent vacuum infiltration. The composites exhibit 2.4 W•m−1•K−1 with 17.5 wt% BN loading, and the through-plane thermal conductivity enhancement reaches 1100%. Furthermore, the mechanical properties of the composites have improved four times compared with pure polyethylene glycol. The obtained composites demonstrate the strong application in thermal management and were simulated in the CPU of the computer. Our fabrication provides a promising strategy to achieve multi-functional polymeric composites through constructing a three-dimensional thermally conductive pathway.

Effect of carbon nanotubes on the thermal conductivity enhancement of synthesized hydroxyapatite filled with water for dental applications: experimental characterization and numerical study

The hydroxyapatite is one of the biocompatible and insulating bioceramics, while the carbon nanotube has a high thermal conductivity potential. This study aims to find an optimal combination and temperature of synthesized hydroxyapatite-carbon nanotube-water hybrid nanofluid achieving both the biocompatibility and the thermal conductivity for dental implant coating. In this study, first, the hydroxyapatite was synthesized, and then, the prepared carbon nanotube was added to the mono-nanofluid of hydroxyapatite (0.2, 0.4, 0.6, 0.8, and 1.0 vol%), obtaining a hybrid nanofluid with the volume ratio of 1:1 for hydroxyapatite/CNT. X-ray powder diffraction, Fourier-transform infrared spectroscopy, Raman spectroscopy, field emission scanning electron microscope, and energy-dispersive X-ray spectroscopy-map tests were used to characterize raw materials and composite products. Zeta potential test and thermal conductivity measurement were used to characterize the hydroxyapatite water (mono-nanofluid) and the composite-water (hybrid nanofluid) in the temperature ranges from 20 to 50 °C. The obtained results show that the highest enhancement of thermal conductivity is 25.83% for the composite sample containing 1.0 vol% of carbon nanotube and temperature of 50 °C compared with mono nanofluids. Also, a numerical study was done to find the best fit correlations for both the mono and the hybrid nanofluids. An artificial neural network was trained to predict the other volume fractions and temperatures.

Impact of magnetic field on the thermal properties of chemically synthesized Sm-Co nanoparticles based silicone oil nanofluid

This work aims to study the enhanced thermal conductivity of silicone oil on increasing mass % of hard magnetic Sm-Co based nanoparticles (NPs) in the presence of external magnetic fields. Sm-Co NPs were synthesized using the low temperature 'Pechini-type sol–gel' process. The presence of mixed phases is evident through XRD, FESEM, and TEM. The average hydrodynamic size of Sm-Co NPs was measured 51 nm by DLS. The study of magnetization vs. magnetic field reveals the weak ferromagnetic ordering along with the paramagnetic behaviour of the Sm-Co NPs. Thermal conductivity enhancement of Sm-Co nanofluids showed an increasing trend with the rising particle concentration and magnetic flux density. A high thermal conductivity enhancement of ~ 373% is reported at 15 mass % concentration of Sm-Co nanofluids and at a magnetic flux density of 0.5 T. The mechanism behind this thermal conductivity enhancement in the presence of an externally applied magnetic field has been discussed on the basis of near field magneto-static interactions of the magnetic nanoparticles. Microstructural, magnetic, and heat transport studies of Sm-Co based MNFs are very useful for device applications.

Graphdiyne-Based Thermal Fluids

Graphdiyne (GDY) exhibits great application potential. However, large-yield and scalable exfoliation of few-layered GDY nanosheets (GDYNSs) remains a huge challenge. Here, we reported a liquid-phase, facile and efficient hydrothermal exfoliation approach to produce mono- or few-layered GDYNSs, which can achieve 82 wt% of high actual yield and 5 mg/ml concentration. The GYDNSs were then dispersed in mineral oil (MO) to act as heat transfer nanofluids for the first time. Typically, at a fraction of 1.0 vol %, the nano-oils showed significantly enhanced thermal conductivity ((Keff/K0)-1) %, up to ∼122%. The low filler fraction and high thermal conductivity enhancement for this GYDNSs/MO nano-oil demonstrates several thermal transfer applications of heavy equipment. Our work provides reasonable insight into the exfoliation and thermal-fluid applications of GDYNSs.