The contact angle of nanofluids as thermophysical property

Hernaíz, Marta; Alonso, Vicente Gutiérrez; Estellé, Patrice; Wu, Zan; Sundén, Bengt; Doretti, Luca; Mancin, Simone; Çobanoğlu, Nur; Karadeniz, Ziya Haktan; Garmendia, Nere; Lasheras-Zubiate, M.; López, Leonor Hernández; Mondragón, Rosa; Martínez‐Cuenca, Raúl; Barison, S.; Kujawska, A.; Turgut, Alpaslan; Amigo, Alfredo; Huminic, Gabriela; Huminic, Angel; Kalus, Mark-Robert; Schroth, K.-G.; Buschmann, Matthias

doi:10.1016/j.jcis.2019.04.007

Cited by 52 publications

(41 citation statements)

References 34 publications

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“…Air-water interfacial tension was determined at room temperature and the result showed a deviation lower than 2% with surface tension data reported for water in [38]. Experimental uncertainty in measurements performed with this device was estimated to be 1% (SFT) [39], while a maximum relative deviation of 0.52% was obtained in [36] Like continuous and dispersed phases, nano-emulsions containing 2 and 4% mass concentrations of paraffin are mainly Newtonian within the studied shear rate range. However, a slight decrease in shear viscosity with increasing shear rate (pseudo-plastic behavior) was observed for the 10 wt.% paraffin loading in the region of low shear rates.…”

Section: Surface Propertiesmentioning

confidence: 54%

“…Surface tension measurements were carried out in the range between 275 and 303 K, both increasing and decreasing temperature with steps of 2-5 K. The contact angles of water and nano-emulsion droplets formed using a 15-gauge needle and deposited on a stainless steel substrate were analyzed at 278 and 298 K using Young-Laplace equation. This substrate was previously utilized in the framework of a round robin test [36] in which nine independent European research centers of the Cost Action NanoUptake program [37] took part. A thoroughly characterization of substrate roughness is presented in Hernaiz et al [36].…”

Section: Surface Propertiesmentioning

confidence: 99%

“…This substrate was previously utilized in the framework of a round robin test [36] in which nine independent European research centers of the Cost Action NanoUptake program [37] took part. A thoroughly characterization of substrate roughness is presented in Hernaiz et al [36]. Recommendations such as substrate cleaning proposed in [36] were followed in this study.…”

Section: Surface Propertiesmentioning

confidence: 99%

“…A thoroughly characterization of substrate roughness is presented in Hernaiz et al [36]. Recommendations such as substrate cleaning proposed in [36] were followed in this study. For the three physical properties, values were determined within a few seconds after drops were formed (IFT and SFT) or deposited in the stainless substrate (CA).…”

Section: Surface Propertiesmentioning

confidence: 99%

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Dynamic Viscosity, Surface Tension and Wetting Behavior Studies of Paraffin–in–Water Nano–Emulsions

et al. 2019

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This work analyzes the dynamic viscosity, surface tension and wetting behavior of phase change material nano–emulsions (PCMEs) formulated at dispersed phase concentrations of 2, 4 and 10 wt.%. Paraffin–in–water samples were produced using a solvent–assisted route, starting from RT21HC technical grade paraffin with a nominal melting point at ~293–294 K. In order to evaluate the possible effect of paraffinic nucleating agents on those three properties, a nano–emulsion with 3.6% of RT21HC and 0.4% of RT55 (a paraffin wax with melting temperature at ~328 K) was also investigated. Dynamic viscosity strongly rose with increasing dispersed phase concentration, showing a maximum increase of 151% for the sample containing 10 wt.% of paraffin at 278 K. For that same nano–emulsion, a melting temperature of ~292.4 K and a recrystallization temperature of ~283.7 K (which agree with previous calorimetric results of that emulsion) were determined from rheological temperature sweeps. Nano–emulsions exhibited surface tensions considerably lower than those of water. Nevertheless, at some concentrations and temperatures, PCME values are slightly higher than surface tensions obtained for the corresponding water+SDS mixtures used to produce the nano–emulsions. This may be attributed to the fact that a portion of the surfactant is taking part of the interface between dispersed and continuous phase. Finally, although RT21HC–emulsions exhibited contact angles considerably inferior than those of distilled water, PCME sessile droplets did not rapidly spread as it happened for water+SDS with similar surfactant contents or for bulk–RT21HC.

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Section: Surface Propertiesmentioning

confidence: 54%

Section: Surface Propertiesmentioning

confidence: 99%

Section: Surface Propertiesmentioning

confidence: 99%

Section: Surface Propertiesmentioning

confidence: 99%

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Dynamic Viscosity, Surface Tension and Wetting Behavior Studies of Paraffin–in–Water Nano–Emulsions

et al. 2019

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“…It should be noted that while wetting properties (like contact angle) of molten salts and molten salts nanofluids are widely discussed in the literature [11][12][13], their control to avoid creeping is rarely discussed. In particular, a round-robin test was reported in Reference [11] to identify the effect of nanoparticles doping on the contact angle of molten nitrate salt. The method of capillary rise was applied to molten carbonate salt and porous electrodes [12].…”

Section: Introductionmentioning

confidence: 99%

Wettability Control for Correct Thermophysical Properties Determination of Molten Salts and Their Nanofluids

et al. 2019

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Proper recording of thermophysical properties for molten salts (MSs) and molten salts based nanofluids (MSBNs) is of paramount importance for the thermal energy storage (TES) technology at concentrated solar power (CSP) plants. However, it is recognized by scientific and industrial communities to be non-trivial, because of molten salts creeping (scaling) inside a measuring crucible or a sample container. Here two strategies are proposed to solve the creeping problem of MSs and MSBNs for the benefit of such techniques as differential scanning calorimetry (DSC) and laser flash apparatus (LFA). The first strategy is the use of crucibles with rough inner surface. It was found that only nanoscale roughness solves the creeping problem, while micron-scale roughness does not affect the wetting phenomena considerably. The second strategy is the use of crucible made of or coated with a low-surface energy material. Both strategies resulted in contact angle of molten salt higher than 90° and as a result, repeatable measurements in correspondence to the literature data. The proposed methods can be used for other characterization techniques where the creeping of molten salts brings the uncertainty or/and unrepeatability of the measurements.

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The Challenge of Superhydrophobicity: Environmentally Facilitated Cassie–Wenzel Transitions and Structural Design

Zhong,

Xie,

Guo

2023

Advanced Science

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Superhydrophobic materials can be used in various fields to optimize production and life due to their unique surface wetting properties. However, under certain pressure and perturbation conditions, the droplets deposited on superhydrophobic materials are prone to change from Cassie state to Wenzel state, which limits the practical applications of the materials. In recent years, a large number of works have investigated the transition behavior, transition mechanism, and influencing factors of the wetting transition that occurs when a superhydrophobic surface is under a series of external environments. Based on these works, in this paper, the phenomenon and kinetic behavior of the destruction of the Cassie state and the mechanism of the wetting transition are systematically summarized under external conditions that promote the wetting transition on the material surface, including pressure, impact, evaporation, vibration, and electric wetting. In addition, superhydrophobic surface morphology has been shown to directly affect the duration of the Cassie state. Based on the published work the effects of specific morphology on the Cassie state, including structural size, structural shape, and structural level, are summarized in this paper from theoretical analyses and experimental data.

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The contact angle of nanofluids as thermophysical property

Cited by 52 publications

References 34 publications

Dynamic Viscosity, Surface Tension and Wetting Behavior Studies of Paraffin–in–Water Nano–Emulsions

Dynamic Viscosity, Surface Tension and Wetting Behavior Studies of Paraffin–in–Water Nano–Emulsions

Wettability Control for Correct Thermophysical Properties Determination of Molten Salts and Their Nanofluids

The Challenge of Superhydrophobicity: Environmentally Facilitated Cassie–Wenzel Transitions and Structural Design

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