Dependence of viscosity of suspensions of ceramic nanopowders in ethyl alcohol on concentration and temperature

This work presents results of measurements of viscosity of suspensions including yttrium oxide (Y(2)O(3)), yttrium aluminum garnet (Y(3)Al(5)O(12)) and magnesium aluminum spinel (MgAl(2)O(4)) nanopowders in ethanol. Nanoparticles used in our research were either commercially available (Baikowski) or nanopowders newly developed in the Institute of Ceramics and Building Materials in Warsaw, Poland. The study was conducted in a wide range of shear rates (0.01 to 2,000 s(−1)) and temperature interval from -15°C to 20°C. A Haake Mars 2 rheometer from Thermo Fisher, Germany, was used in the Biophysics Laboratory at Rzeszów University of Technology. Most of the samples show a non-Newtonian behaviour. It was confirmed with a Rheo-NMR system from Bruker that 10% by weight of Y(2)O(3) suspension is a non-Newtonian fluid. In this work, we also report an unexpected behaviour of the viscosity of some samples (Y(2)O(3) and Y(3)Al(5)O(12)) due to sedimentation effect

Thermophysical, rheological and dielectric behaviour of stable carbon black dispersions in PEG200

Phase change materials can store or release large amounts of energy during phase change. An increasing number of authors are studying the influence of the dispersion of nanometric particles on these materials. This article presents the design and experimental characterization of temporal stability, thermal conductivity, isobaric heat capacity, phase change transitions, rheological behaviour, and dielectric properties of nano-enhanced phase change materials based on carbon black (CB) dispersions in polyethylene glycol (PEG200) by using polyvinylpyrrolidone (PVP) as surfactant. We studied the temporal stability of carbon black nanoparticles dispersed in PEG200 using dynamic light scattering and spectrophotometry techniques. All the samples showed good temporal stability, since the measurements of the hydrodynamic size of the nanoparticles are practically constant over time and the wavelength observed by UV–vis shows a small variation of around 4% for static conditions. We observed small changes in thermal conductivity and isobaric heat capacity. Nevertheless, the thermograms evidence how the latent heat clearly increases with the load of carbon black nanoparticles up to four times that of the PEG200. The viscosity studies do not show variation with shear rate, indicating a Newtonian behaviour, excluding the 2.0 wt% CB/PVP + PEG200 nanofluid. Additionally, we noticed frequency dependent and independent regions for permittivityAgencia Estatal de Investigación | Ref. PID2020-112846RB-C21Agencia Estatal de Investigación | Ref. PDC2021-121225-C21Ministerio de Universidades | Ref. 33.50.460A.752European Cooperation in Science and Technology | Ref. IG15119Universidade de Vigo/CISU

Advances in Rheological Behavior of Nanofluids and Ionanofluids – an Editorial Note

International audienceThis editorial note is dedicated to the Virtual Special Issue about the “Advances in Rheological Behavior of Nanofluids and Ionanofluids”. After a brief presentation of the objectives of this VSI, the contributions published in the Journal of Molecular Liquids are introduced

Nanofluids in the Service of High Voltage Transformers: Breakdown Properties of Transformer Oils with Nanoparticles, a Review

The continuous development of electrical systems and high voltage transformers builds the need for looking for new insulating media or to improve the insulating properties of commercially available transformer oils (TO) by various modification techniques. One of these techniques is the modification of existing mineral oils by the addition of different types of nanoparticles in various concentrations. These types of materials, suspensions of nanoparticles called nanofluids, have found numerous applications in the energy industry, especially in heat exchanger systems and solar cells. Much research has been done on attempts to replace mineral oils (MO), which are harmful for the environment, with natural ester oils (NE), but to make this possible, it is necessary to improve the insulating properties of these oils, for example by adding nanoparticles. This paper presents an extensive overview of the insulating properties; including for AC, DC and the lightning impulse breakdown voltage; for both mineral and natural ester oils containing various type of nanoparticles (NP). It is presented that the use of nanofluids could improve the efficiency of existing high voltage infrastructures with a low financial cost

Ionic Liquid and Ionanofluid-Based Redox Flow Batteries—A Mini Review

Stationary energy storage methods such as flow batteries are one of the best options to integrate with smart power grids. Though electrochemical energy storage using flow battery technologies has been successfully demonstrated since the 1970s, the introduction of ionic liquids into the field of energy storage introduces new dimensions in this field. This reliable energy storage technology can provide significantly more flexibility when incorporated with the synergic effects of ionic liquids. This mini-review enumerates the present trends in redox flow battery designs and the use of ionic liquids as electrolytes, membranes, redox couples, etc. explored in these designs. This review specifically intends to provide an overview of the research prospects of ionic liquids for redox flow batteries (RFB)

Ionic Liquid and Ionanofluid-Based Redox Flow Batteries—A Mini Review

Stationary energy storage methods such as flow batteries are one of the best options to integrate with smart power grids. Though electrochemical energy storage using flow battery technologies has been successfully demonstrated since the 1970s, the introduction of ionic liquids into the field of energy storage introduces new dimensions in this field. This reliable energy storage technology can provide significantly more flexibility when incorporated with the synergic effects of ionic liquids. This mini-review enumerates the present trends in redox flow battery designs and the use of ionic liquids as electrolytes, membranes, redox couples, etc. explored in these designs. This review specifically intends to provide an overview of the research prospects of ionic liquids for redox flow batteries (RFB)

Experimental Investigation of Thermal Conductivity of Water-Based Fe₃O₄ Nanofluid: An Effect of Ultrasonication Time

Nanofluid preparation is a crucial step in view of their thermophysical properties as well as the intended application. This work investigates the influence of ultrasonication duration on the thermal conductivity of Fe3O4 nanofluid. In this work, water-based Fe3O4 nanofluids of various volume concentrations (0.01 and 0.025 vol.%) were prepared and the effect of ultrasonication time (10 to 55 min) on their thermal conductivity was investigated. Ultrasonication, up to a time duration of 40 min, was found to raise the thermal conductivity of Fe3O4 nanofluids, after which it starts to deteriorate. For a nanofluid with a concentration of 0.025 vol.%, the thermal conductivity increased to 0.782 W m−1K−1 from 0.717 W m−1K−1 as the ultrasonication time increased from 10 min to 40 min; however, it further deteriorated to 0.745 W m−1K−1 after a further 15 min increase (up to a total of 55 min) in ultrasonication duration. Thermal conductivity is a strong function of concentration of the nanofluid; however, the optimum ultrasonication time is the same for different nanofluid concentrations

Thermal and physical characterization of PEG phase change materials enhanced by carbon-based nanoparticles

This paper presents the preparation and thermal/physical characterization of phase change materials (PCMs) based on poly(ethylene glycol) 400 g·mol−1 and nano-enhanced by either carbon black (CB), a raw graphite/diamond nanomixture (G/D-r), a purified graphite/diamond nanomixture (G/D-p) or nano-Diamond nanopowders with purity grades of 87% or 97% (nD87 and nD97, respectively). Differential scanning calorimetry and oscillatory rheology experiments were used to provide an insight into the thermal and mechanical changes taking place during solid-liquid phase transitions of the carbon-based suspensions. PEG400-based samples loaded with 1.0 wt.% of raw graphite/diamond nanomixture (G/D-r) exhibited the lowest sub-cooling effect (with a reduction of ~2 K regarding neat PEG400). The influences that the type of carbon-based nanoadditive and nanoparticle loading (0.50 and 1.0 wt.%) have on dynamic viscosity, thermal conductivity, density and surface tension were also investigated in the temperature range from 288 to 318 K. Non-linear rheological experiments showed that all dispersions exhibited a non-Newtonian pseudo-plastic behavior, which was more noticeable in the case of carbon black nanofluids at low shear rates. The highest enhancements in thermal conductivity were observed for graphite/diamond nanomixtures (3.3–3.6%), while nano-diamond suspensions showed the largest modifications in density (0.64–0.66%). Reductions in surface tension were measured for the two nano-diamond nanopowders (nD87 and nD97), while slight increases (within experimental uncertainties) were observed for dispersions prepared using the other three carbon-based nanopowders. Finally, a good agreement was observed between the experimental surface tension measurements performed using a Du Noüy ring tensiometer and a drop-shape analyzer.EU COST | Ref. COST-STSM-CA15119-42918EU COST | Ref. COST-STSM-CA15119-45590EU COST | Ref. COST-STSM-CA15119-45123Ministerio de Economía y Competitividad | Ref. ENE2017-86425-C2-1-R

Electrical Conductivity and Dielectric Properties of Ethylene Glycol-Based Nanofluids Containing Silicon Oxide–Lignin Hybrid Particles

This paper presents results of experimental investigation into dielectric properties of silicon oxide lignin (SiO2-L) particles dispersed with various mass fractions in ethylene glycol (EG). Measurements were conducted at a controlled temperature, which was changed from 298.15 to 333.15 K with an accuracy of 0.5 and 0.2 K for dielectric properties and direct current (DC) electrical conductivity, respectively. Dielectric properties were measured with a broadband dielectric spectroscopy device in a frequency range from 0.1 to 1 MHz, while DC conductivity was investigated using a conductivity meter MultiLine 3410 working with LR925/01 conductivity probe. Obtained results indicate that addition of even a small amount of SiO2-L nanoparticles to ethylene glycol cause a significant increase in permittivity and alternating current (AC) conductivity as well as DC conductivity, while relaxation time decrease. Additionally, both measurement methods of electrical conductivity are in good agreement