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Open AccessArticle

Numerical Analysis of Surfactant Influence on Heat Transfer Behavior of TiO₂ Nanocolloid in Laminar Flow

by George Catalin Tofan, Catalin Andrei Tugui, Alina Adriana Minea, Emilian Turcanu and Elena Ionela Chereches

ChemEngineering 2026, 10(6), 75; https://doi.org/10.3390/chemengineering10060075 - 15 Jun 2026

Viewed by 378

Abstract

Nanocolloid research has undergone a complete transformation, renouncing the empirical estimation of properties and relying on real case scenarios. The main objective of this paper is to compare a large number of samples that were experimentally studied in terms of thermophysical properties in order to be able to draw a conclusion in terms of the heat transfer efficiency of a certain surfactant addition to a 2 wt.% TiO₂ nanoparticle-enhanced fluid. The analysis discusses both the advantages and drawbacks in terms of surfactant type and concentration influence over the Prandtl number, thermal diffusivity, and Nusselt number, as well as the heat transfer coefficient for different Reynolds numbers in laminar flow. The investigation also includes a different figure of merits and performance evaluation criteria that are extensively employed in the literature in order to have a complete overview of the efficiency of surfactants in improving nanocolloids. In conclusion, even if surfactants are considered for improving nanocolloid stability, their drawbacks have not been debated in depth in the open literature. The main conclusion that arises from this study outlines that among all tested samples, F127 at a concentration of 0.25 wt.% consistently demonstrates the best overall performance, achieving an optimal balance between enhanced thermal properties and acceptable pumping requirements. Full article

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25 pages, 5809 KB

Open AccessEditor’s ChoiceArticle

The Dominance of Pretransitional Effects in Liquid Crystal-Based Nanocolloids: Nematogenic 4-methoxybenzylidene-4′–butylaniline with Transverse Permanent Dipole Moment and BaTiO₃ Nanoparticles

by Aleksandra Drozd-Rzoska, Joanna Łoś and Sylwester J. Rzoska

Nanomaterials 2024, 14(8), 655; https://doi.org/10.3390/nano14080655 - 9 Apr 2024

Cited by 8 | Viewed by 2861

Abstract

The report presents static, low-frequency, and dynamic dielectric properties in the isotropic liquid, nematic, and solid phases of MBBA and related nanocolloids with paraelectric BaTiO₃ nanoparticles (spherical, d = 50 nm). MBBA (4-methoxybenzylidene-4′–butylaniline) is a liquid crystalline compound with a permanent dipole moment transverse to the long molecular axis. The distortions-sensitive analysis of the dielectric constant revealed its hidden pretransitional anomaly, strongly influenced by the addition of nanoparticles. The evolution of the dielectric constant in the nematic phase shows the split into two regions, with the crossover coinciding with the standard melting temperature. The ‘universal’ exponential-type behavior of the low-frequency contribution to the real part of the dielectric permittivity is found. The critical-like pretransitional behavior in the solid phase is also evidenced. This is explained by linking the Lipovsky model to the Mossotti catastrophe concept under quasi-negative pressure conditions. The explicit preference for the ‘critical-like’ evolution of the apparent activation enthalpy is worth stressing for dynamics. Finally, the long-range, ‘critical-like’ behavior of the dissipation factor (D = tgδ), covering the isotropic liquid and nematic phases, is shown. Full article

(This article belongs to the Special Issue Morphological Design and Synthesis of Nanoparticles (Second Edition))

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14 pages, 12135 KB

Open AccessArticle

Experiments on the Electrical Conductivity of PEG 400 Nanocolloids Enhanced with Two Oxide Nanoparticles

by Elena Ionela Chereches and Alina Adriana Minea

Nanomaterials 2023, 13(9), 1555; https://doi.org/10.3390/nano13091555 - 5 May 2023

Cited by 10 | Viewed by 2572

Abstract

This paper aims to provide some insights into the pH and electrical conductivity of two classes of nanocolloids with PEG 400 as the base fluid. Thus, nanoparticles of two oxides—MgO and TiO₂—were added to the base fluid in 5 mass concentrations in the range 0.25–2.5 %wt. The stability was evaluated in terms of pH at ambient temperature, while the electrical conductivity was discussed at both ambient temperature and up to 333.15 K. The electrical conductivity of PEG 400 was previously discussed by this group, while the behavior of the new nanocolloids was debated in terms of the state of the art. More precisely, the influence of MgO increases electrical conductivity, and an enhancement of up to 48% for 0.25% MgO was found, while the influence of TiO₂ nanoparticles was found to be in similar ranges. In conclusion, electrical conductivity varies with temperature and the addition of nanoparticles to the base fluid, although the mechanisms that are driving the nanoparticle type and concentration influence are not yet entirely assumed in the available literature. Full article

(This article belongs to the Special Issue Current Advances in Nanoelectronics, Nanosensors and Devices)

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14 pages, 4970 KB

Open AccessArticle

A Study of a PID Controller Used in a Micro-Electrical Discharge Machining System to Prepare TiO₂ Nanocolloids

by Kuo-Hsiung Tseng, Yur-Shan Lin, Chaur-Yang Chang and Meng-Yun Chung

Nanomaterials 2020, 10(6), 1044; https://doi.org/10.3390/nano10061044 - 29 May 2020

Cited by 6 | Viewed by 2721

Abstract

This study developed a micro-electrical discharge machining (micro-EDM) system for producing TiO₂ nanocolloids. When a proportional–integral–derivative controller designed using the Ziegler–Nichols method was adopted to control the interelectrode gap, TiO₂ nanocolloids were obtained from spark discharges generated between two titanium wires immersed in deionized water. For a pulse on time–off time of 40–40 μs and a colloid production time of 100 min, TiO₂ nanocolloids were produced that had an absorbance of 1.511 at a wavelength of 245 nm and a ζ potential of −47.2 mV. They had an average particle diameter of 137.2 nm, and 64.2% of particles were smaller than 91.28 nm. The minimum particles were spherical. The characteristics of colloids confirmed that the micro-EDM system can produce TiO₂ nanocolloids with excellent suspension stability. The colloid production method proposed in this study has the advantages of low equipment cost and no dust diffusion in the process environment. These advantages can improve the competitiveness of the electric spark discharge method for high-quality TiO₂ nanoparticle production. The colloids produced in this study did not contain elements other than titanium and oxygen, and they may prevent secondary environmental pollution. Full article

(This article belongs to the Special Issue Future and Prospects in Nanofluids Research)

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15 pages, 3543 KB

Open AccessArticle

Advanced Photocatalysts Based on Reduced Nanographene Oxide–TiO₂ Photonic Crystal Films

by Angeliki Diamantopoulou, Elias Sakellis, Spiros Gardelis, Dimitra Tsoutsou, Spyridon Glenis, Nikolaos Boukos, Athanasios Dimoulas and Vlassis Likodimos

Materials 2019, 12(16), 2518; https://doi.org/10.3390/ma12162518 - 7 Aug 2019

Cited by 14 | Viewed by 4277

Abstract

Surface functionalization of TiO₂ inverse opals by graphene oxide nanocolloids (nanoGO) presents a promising modification for the development of advanced photocatalysts that combine slow photon-assisted light harvesting, surface area, and mass transport of macroporous photonic structures with the enhanced adsorption capability, surface reactivity, and charge separation of GO nanosheets. In this work, post-thermal reduction of nanoGO–TiO₂ inverse opals was investigated in order to explore the role of interfacial electron transfer vs. pollutant adsorption and improve their photocatalytic activity. Photonic band gap-engineered TiO₂ inverse opals were fabricated by the coassembly technique and were functionalized by GO nanosheets and reduced under He at 200 and 500 °C. Comparative performance evaluation of the nanoGO–TiO₂ films on methylene blue photodegradation under UV-VIS and visible light showed that thermal reduction at 200 °C, in synergy with slow photon effects, improved the photocatalytic reaction rate despite the loss of nanoGO and oxygen functional groups, pointing to enhanced charge separation. This was further supported by photoluminescence spectroscopy and salicylic acid UV-VIS photodegradation, where, in the absence of photonic effects, the photocatalytic activity increased, confirming that fine-tuning of interfacial coupling between TiO₂ and reduced nanoGO is a key factor for the development of highly efficient photocatalytic films. Full article

(This article belongs to the Special Issue Advanced Photocatalytic Materials)

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