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Thermal and Photocatalytic Analysis of Nanomaterials

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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Materials Chemistry".

Deadline for manuscript submissions: closed (31 July 2023) | Viewed by 18707

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Dr. Imre Miklós Szilágyi

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Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Budapest, Hungary
Interests: materials science; nanotechnology; analytical chemistry; photocatalysis; gas sensing; nanofluids; atomic layer deposition; nanocomposites
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Dr. Omid Mahian

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School of Chemical Engineering and Technology, Xi'an Jiaotong University, Xi'an 710049, China
Interests: solar energy systems; entropy generation and exergy analysis in energy systems; heat transfer in nanofluids; solar stills
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Dr. Klára Hernádi

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Institute of Physical Metallurgy, Metal Forming and Nanotechnology, University of Miskolc, 3515 Miskolc, ‎Hungary
Interests: heterogeneous catalysis; photocatalytic materials; carbon nanotubes; nanocomposite materials
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Dr. Ottó Horváth

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Research Group of Environmental and Inorganic Photochemistry, Center for Natural Sciences, Faculty of Engineering, University of Pannonia, P.O. Box 1158, H-8210 Veszprém, Hungary
Interests: photoinduced behavior of coordination compounds and photoactive semiconductors in homogeneous and heterogeneous systems; environmental photochemistry; environmental analysis
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The thermal properties of nanomaterials are important in both their preparation and application. Several nanostructured compounds are prepared by thermal decomposition of their precursors, and detailed knowledge of the decomposition scheme is vital to be able to control the structure, composition, and morphology of the as-prepared nanomaterials. It is also well known that the synthesis of nanomaterials produces amorphous products, and a further annealing step is needed to make them crystalline. Heating is also often used to remove unreacted precursors and byproducts. When complex nanomaterials are prepared using sacrificial templates (e.g., hollow nanoparticles and inverse opals), annealing is one method of removing organic core materials. The thermal stability of a nanostructure is important for many applications that require elevated temperatures (e.g., fuel cells, gas sensing, catalysis). For some nanosystems, temperature and heat change or transfer are central to their applications, e.g., phase change materials, nanofluids, etc.

Among the many possible applications of nanomaterials, photocatalysis is notable. It uses solar energy as a renewable source, making it one of the most promising technologies for the elimination of toxic compounds from water due to the advantages of high activity, photochemical stability, and cost-efficiency. Beside aqueous applications, it can also significantly increase indoor air quality and contribute to eliminating pollutants such as VOCs indoors or outdoors. In addition to oxidation, photocatalytic reduction in harmful molecules (e.g., NOx) is an emerging field.

Photocatalytic synthesis is also a major field of green chemistry. It ranges from artificial photosynthesis by converting CO₂ and H₂O into organic raw molecules, to performing photocatalytic synthetic versions of more sophisticated organic processes.

There are many exciting materials and processes appearing in contemporary photocatalytic research, including photonic bandgap structures and all-organic photocatalysts. Using computation chemistry and applying extreme laser infrastructure to understand photon absorption, excitation, and dissipation processes and the photochemical reactions that occur therewith are also hot topics in this field.

The present Special Issue aims to collect studies and results of the latest developments in the thermal and photocatalytic properties of nanomaterials.

Dr. Imre Miklós Szilágyi
Dr. Omid Mahian
Dr. Klára Hernádi
Dr. Ottó Horváth
Guest Editors

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

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Keywords

nanotechnology
thermal
decomposition
nanofluid
photocatalysis
decontamination
synthesis

Related Special Issue

Thermal and Photocatalytic Analysis of Nanomaterials: 2nd Edition in Molecules (1 article)

Published Papers (10 papers)

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Research

23 pages, 6357 KiB

Open AccessArticle

Carbon-Based Ternary Nanocomposite: Bullet Type ZnO–SWCNT–CuO for Substantial Solar-Driven Photocatalytic Decomposition of Aqueous Organic Contaminants

by Santu Shrestha, Kamal Prasad Sapkota, Insup Lee, Md Akherul Islam, Anil Pandey, Narayan Gyawali, Jeasmin Akter, Harshavardhan Mohan, Taeho Shin, Sukmin Jeong and Jae Ryang Hahn

Molecules 2022, 27(24), 8812; https://doi.org/10.3390/molecules27248812 - 12 Dec 2022

Cited by 1 | Viewed by 1675

Abstract

A facile two-step synthesis of ternary hetero-composites of ZnO, CuO, and single-walled carbon nanotubes (SWCNTs) was developed through a recrystallization process followed by annealing. A series of nanocomposites were prepared by varying the weight ratio of copper(II) acetate hydrate and zinc(II) acetate dihydrate and keeping the weight ratio of SWCNTs constant. The results revealed the formation of heterojunctions (ZnO–SWCNT–CuO, ZSC) of three crystal structures adjacent to each other, forming a ternary wurtzite-structured nanoparticles along with defects. Enhanced charge separation (electron-hole pairs), reduced band gap, defect-enhanced specific surface area, and promoted oxidation potential were key factors for the enhanced photocatalytic activity of the ternary nanocomposites. OH^• radicals were the main active species during dye degradation, and O₂^−• and h⁺ were also involved to a lesser extent. A type II heterojunction mechanism approach is proposed based on the charge carrier migration pattern. Among the synthesized nanocomposites, the sample prepared using copper(II) acetate hydrate and zinc(II) acetate dihydrate in a 1: 9 ratio (designated a ZSC3) showed the highest photocatalytic activity. ZSC3 achieved 99.2% photodecomposition of methylene blue in 20 min, 94.1% photodecomposition of Congo red in 60 min, and 99.6% photodecomposition of Rhodamine B in 40 min under simulated sunlight. Additionally, ZSC3 showed excellent reusability and stability, maintaining 96.7% of its activity even after five successive uses. Based on overall results, the ZSC sample was proposed as an excellent candidate for water purification applications. Full article

(This article belongs to the Special Issue Thermal and Photocatalytic Analysis of Nanomaterials)

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17 pages, 3347 KiB

Open AccessArticle

Green Synthesis of NiO-SnO₂ Nanocomposite and Effect of Calcination Temperature on Its Physicochemical Properties: Impact on the Photocatalytic Degradation of Methyl Orange

by Sirajul Haq, Anum Sarfraz, Farid Menaa, Nadia Shahzad, Salah Ud Din, Hanadi A. Almukhlifi, Sohad A. Alshareef, Ethar M. Al Essa and Muhammad Imran Shahzad

Molecules 2022, 27(23), 8420; https://doi.org/10.3390/molecules27238420 - 01 Dec 2022

Cited by 5 | Viewed by 1444

Abstract

Background: Nickel stannate nanocomposites could be useful for removing organic and toxic water pollutants, such as methyl orange (MO). Aim: The synthesis of a nickel oxide–tin oxide nanocomposite (NiO-SnO₂ NC) via a facile and economically viable approach using a leaf extract from Ficus elastica for the photocatalytic degradation of MO. Methods: The phase composition, crystallinity, and purity were examined by X-ray diffraction (XRD). The particles’ morphology was studied using scanning electron microscopy (SEM). The elemental analysis and colored mapping were carried out via energy dispersive X-ray (EDX). The functional groups were identified by Fourier transform infrared spectroscopy (FTIR). UV–visible diffuse reflectance spectroscopy (UV–vis DRS) was used to study the optical properties such as the absorption edges and energy band gap, an important feature of semiconductors to determine photocatalytic applications. The photocatalytic activity of the NiO-SnO₂ NC was evaluated by monitoring the degradation of MO in aqueous solution under irradiation with full light spectrum. The effects of calcination temperature, pH, initial MO concentration, and catalyst dose were all assessed to understand and optimize the physicochemical and photocatalytic properties of NiO-SnO₂ NC. Results: NiO-SnO₂ NC was successfully synthesized via a biological route using F. elastica leaf extract. XRD showed rhombohedral NiO and tetragonal SnO₂ nanostructures and the amorphous nature of NiO-SnO₂ NC. Its degree of crystallinity, crystallite size, and stability increased with increased calcination temperature. SEM depicted significant morphological changes with elevating calcination temperatures, which are attributed to the phase conversion from amorphous to crystalline. The elemental analysis and colored mapping show the formation of highly pure NiO-SnO₂ NC. FTIR revealed a decrease in OH, and the ratio of oxygen vacancies at the surface of the NC can be explained by a loss of its hydrophilicity at increased temperatures. All the NC samples displayed significant absorption in the visible region, and a blue shift is seen and the energy band gap decreases when increasing the calcination temperatures due to the dehydration and formation of compacted large particles. NiO-SnO₂ NC degrades MO, and the photocatalytic performance decreased with increasing calcination temperature due to an increase in the crystallite size of the NC. The optimal conditions for the efficient NC-mediated photocatalysis of MO are 100 °C, 20 mg catalyst, 50 ppm MO, and pH 6. Conclusions: The auspicious performance of the NiO-SnO₂ NCs may open a new avenue for the development of semiconducting p–n heterojunction catalysts as promising structures for removing undesirable organic pollutants from the environment. Full article

(This article belongs to the Special Issue Thermal and Photocatalytic Analysis of Nanomaterials)

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24 pages, 4510 KiB

Open AccessArticle

Characterization of Various Titanium-Dioxide-Based Catalysts Regarding Photocatalytic Mineralization of Carbamazepine also Combined with Ozonation

by Gábor Kocsis, Erzsébet Szabó-Bárdos, Orsolya Fónagy, Evelin Farsang, Tatjána Juzsakova, Miklós Jakab, Péter Pekker, Margit Kovács and Ottó Horváth

Molecules 2022, 27(22), 8041; https://doi.org/10.3390/molecules27228041 - 19 Nov 2022

Cited by 1 | Viewed by 1173

Abstract

Titanium-dioxide-based semiconductors proved to be appropriate for photocatalytic application to efficiently degrade emerging organic pollutants such as various herbicides, pesticides, and pharmaceuticals in waters of environmental importance. The characterization of various TiO₂ catalysts, both bare and modified (Ag- and/or N-doped), by mechanochemical treatment was carried out in this work, regarding their structure, morphology, and photocatalytic activity. For the latter investigations, carbamazepine, an antidepressant, proved to be applicable and versatile. The photocatalytic behavior of the catalysts was studied under both UV and visible light. Besides the decomposition efficiency, monitoring the intermediates provided information on the degradation mechanisms. Mechanochemical treatment significantly increased the particle size (from 30 nm to 10 μm), causing a considerable (0.14 eV) decrease in the band gap. Depending on the irradiation wavelength and the catalyst, the activity orders differed, indicating that, in the mineralization processes of carbamazepine, the importance of the different oxidizing radicals considerably deviated, e.g., Ag-TiO₂ < DP25-TiO₂ < ground-DP25-TiO₂ < N-TiO₂ ≈ N-Ag-TiO₂ for O₂^•− and N-TiO₂ ≈ Ag-TiO₂ < N-Ag-TiO₂ < ground-DP25-TiO₂ ≈ DP25-TiO₂ for HO^• generation under UV irradiation. Toxicity studies have shown that the resulting intermediates are more toxic than the starting drug molecule, so full mineralization is required. This could be realized by a synergistic combination of heterogeneous photocatalysis and ozonation. Full article

(This article belongs to the Special Issue Thermal and Photocatalytic Analysis of Nanomaterials)

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13 pages, 4757 KiB

Open AccessArticle

Pt-Chitosan-TiO₂ for Efficient Photocatalytic Hydrogen Evolution via Ligand-to-Metal Charge Transfer Mechanism under Visible Light

by Yanru Liu, Jingyun Mao, Yiwei Huang, Qingrong Qian, Yongjin Luo, Hun Xue and Songwei Yang

Molecules 2022, 27(15), 4673; https://doi.org/10.3390/molecules27154673 - 22 Jul 2022

Cited by 9 | Viewed by 1459

Abstract

The Pt-chitosan-TiO₂ charge transfer (CT) complex was synthesized via the sol-gel and impregnation method. The synthesized photocatalysts were thoroughly characterized, and their photocatalytic activity were evaluated toward H₂ production through water reduction under visible-light irradiation. The effect of the preparation conditions of the photocatalysts (the degree of deacetylation of chitosan, addition amount of chitosan, and calcination temperature) on the photocatalytic activity was discussed. The optimal Pt-10%DD75-T200 showed a H₂ generation rate of 280.4 μmol within 3 h. The remarkable visible-light photocatalytic activity of Pt-chitosan-TiO₂ was due to the CT complex formation between chitosan and TiO₂, which extended the visible-light absorption and induced the ligand-to-metal charge transfer (LMCT). The photocatalytic mechanism of Pt-chitosan-TiO₂ was also investigated. This paper outlines a new and facile pathway for designing novel visible-light-driven photocatalysts that are based on TiO₂ modified by polysaccharide biomass wastes that are widely found in nature. Full article

(This article belongs to the Special Issue Thermal and Photocatalytic Analysis of Nanomaterials)

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15 pages, 3681 KiB

Open AccessArticle

Effects of Preparation Conditions on the Efficiency of Visible-Light-Driven Hydrogen Generation Based on Ni(II)-Modified Cd₀.₂₅Zn₀.₇₅S Photocatalysts

by Maali-Amel Mersel, Lajos Fodor, Péter Pekker, Éva Makó and Ottó Horváth

Molecules 2022, 27(13), 4296; https://doi.org/10.3390/molecules27134296 - 04 Jul 2022

Cited by 5 | Viewed by 1698

Abstract

Hydrogen as an environmentally friendly fuel can be produced by photocatalytic procedures from aqueous systems, utilizing H₂S, an industrial side-product, by conversion and storage of renewable solar energy. Although composites of CdS and ZnS prepared by co-precipitation are very efficient in heterogeneous photocatalytic H₂ generation, the optimal conditions for their synthesis and the effects of the various influencing factors are still not fully clarified. In this work, we investigated how the efficiency of Cd₀.₂₅Zn₀.₇₅S composites modified with Ni(II) was affected by the doping method, Ni-content, hydrothermal treatment, and presence of a complexing agent (ammonia) used in the preparation. The composition, optical, and structural properties of the photocatalysts prepared were determined by ICP, DRS, XRD, TEM, and STEM-EDS. Although hydrothermal treatment proved preferable for Ni-free composites, Ni-modification was more efficient for untreated composites precipitated from ammonia-containing media. The best efficiency (14.9% quantum yield at 380 nm irradiation, 109.8 mmol/g/h hydrogen evolution rate) achieved by surface modification with 0.1–0.3% Ni(II) was 15% and 20% better than those for hydrothermally treated catalyst and similarly prepared Pt-modified one, respectively. Structural characterization of the composites clearly confirmed that the Ni²⁺ ions were not embedded into the CdS-ZnS crystal lattice but were enriched on the surface of particles of the original catalyst in the form of NiO or Ni(OH)₂. This co-catalyst increased the efficiency by electron-trapping, but its too high amount caused an opposite effect by diminishing the excitable surface of the CdS-ZnS particles. Full article

(This article belongs to the Special Issue Thermal and Photocatalytic Analysis of Nanomaterials)

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21 pages, 6725 KiB

Open AccessArticle

Designing Novel Strategy to Produce Active Nanohybrids in Sunlight for Purification of Water Based on Inorganic Nanolayers, Magnetic Nanocomposites and Organic Species

by Osama Saber, Mostafa Osama, Nagih M. Shaalan, Aya Osama, Adil Alshoaibi and Doaa Osama

Molecules 2022, 27(12), 3673; https://doi.org/10.3390/molecules27123673 - 07 Jun 2022

Cited by 3 | Viewed by 1211

Abstract

Energy and water related problems have attracted strong attention from scientists across the world because of deficient energy and water pollution. Following this line, new strategy depended on preparing nanolayers of Al/Zn and magnetic nanoparticles of cobalt iron oxides nanocomposite in addition to long chains of hydrocarbons of stearic acid to be used as roofs, fillers and pillars; respectively, to design optical-active nanohybrids in sunlight for removing the colored pollutants from water in few minutes. By using long chains of hydrocarbons of stearic acid, X-ray diffraction (XRD) results and TEM images showed expansion of the interlayered spacing from 0.76 nm to 2.02 nm and insertion of magnetic nanoparticles among the nanolayers of Al/Zn. The optical properties and activities showed that the nanohybrid structure based on zinc oxide led to clear reduction of the band gap energy from 3.3 eV to 2.75 eV to be effective in sunlight. Photocatalytic degradation of the dye of acid green 1 confirmed the high activity of the prepared zinc oxide nanohybrids because of a complete removal of the dye after ten minutes in sunlight. Finally, this strategy was effective for producing photo-active nanohybrids for using renewable and non-polluting energy for purifying water. Full article

(This article belongs to the Special Issue Thermal and Photocatalytic Analysis of Nanomaterials)

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13 pages, 3041 KiB

Open AccessArticle

Preparation and Photocatalytic Performance of TiO₂ Nanowire-Based Self-Supported Hybrid Membranes

by Mohammed Ahmed Shehab, Nikita Sharma, Andrea Valsesia, Gábor Karacs, Ferenc Kristály, Tamás Koós, Anett Katalin Leskó, Lilla Nánai, Klara Hernadi and Zoltán Németh

Molecules 2022, 27(9), 2951; https://doi.org/10.3390/molecules27092951 - 05 May 2022

Cited by 10 | Viewed by 1940

Abstract

Nowadays, the use of hybrid structures and multi-component materials is gaining ground in the fields of environmental protection, water treatment and removal of organic pollutants. This study describes promising, cheap and photoactive self-supported hybrid membranes as a possible solution for wastewater treatment applications. In the course of this research work, the photocatalytic performance of titania nanowire (TiO₂ NW)-based hybrid membranes in the adsorption and degradation of methylene blue (MB) under UV irradiation was investigated. Characterization techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray powder diffractometry (XRD) were used to study the morphology and surface of the as-prepared hybrid membranes. We tested the photocatalytic efficiency of the as-prepared membranes in decomposing methylene blue (MB) under UV light irradiation. The hybrid membranes achieved the removal of MB with a degradation efficiency of 90% in 60 min. The high efficiency can be attributed to the presence of binary components in the membrane that enhanced both the adsorption capability and the photocatalytic ability of the membranes. The results obtained suggest that multicomponent hybrid membranes could be promising candidates for future photocatalysis-based water treatment technologies that also take into account the principles of circular economy. Full article

(This article belongs to the Special Issue Thermal and Photocatalytic Analysis of Nanomaterials)

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13 pages, 2823 KiB

Open AccessArticle

Photocatalytic Degradation of Paracetamol in Aqueous Medium Using TiO₂ Prepared by the Sol–Gel Method

by Raquel Trujillano, Vicente Rives and Inés García

Molecules 2022, 27(9), 2904; https://doi.org/10.3390/molecules27092904 - 02 May 2022

Cited by 8 | Viewed by 1757

Abstract

Two titania photocatalysts have been prepared using the sol–gel method using TiCl₄ as a precursor, and two different alcohols, namely, ethanol or propanol (Et or Pr). The main aim of this work was to study the effect of the nature of the alcohol on the chemical, structural and photocatalytic properties for paracetamol photodegradation of the final solids. The TiCl₄/alcohol molar ratio to obtain the corresponding alkoxides (TiEt and TiPr) was 1/10. These alkoxides were calcined at 400 °C to prepare the oxide catalysts (named as TiEt400 and TiPr400). Powder X-ray diffraction (PXRD) of the original samples showed the presence of anatase diffraction peaks in sample TiPr, while TiEt is a completely amorphous material. Contrary to commercial TiO₂-P25, the PXRD diagrams of the calcined samples showed anatase as the exclusive crystalline phase in both solids. The specific surface area (S_BET) of sample TiPr400 was larger than that of sample TiEt400, and both larger than that of TiO₂-P25. The three solids have been tested in the photodegradation of paracetamol in aqueous solution. It has been established that the alcohol used influences the properties and catalytic activity of the final oxides. The synthesized solids exhibit a higher activity than commercial TiO₂-P25, because of their structural characteristics and larger S_BET. Full article

(This article belongs to the Special Issue Thermal and Photocatalytic Analysis of Nanomaterials)

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17 pages, 2546 KiB

Open AccessArticle

Photocatalytic Degradation of Orange G Dye by Using Bismuth Molybdate: Photocatalysis Optimization and Modeling via Definitive Screening Designs

by Brijesh Kumar Shukla, Shalu Rawat, Mayank Kumar Gautam, Hema Bhandari, Seema Garg and Jiwan Singh

Molecules 2022, 27(7), 2309; https://doi.org/10.3390/molecules27072309 - 02 Apr 2022

Cited by 15 | Viewed by 2452

Abstract

In the current study, Bismuth molybdate was synthesized using simple co-precipitation procedure, and their characterization was carried out by various methods such as FT-IR, SEM, and P-XRD. Furthermore, the photocatalytic degradation of Orange G (ORG) dye using synthesized catalyst under visible light irradiation was studied. Response surface Method was used for the optimization of process variables and degradation kinetics evaluated by modeling of experimental data. Based on the experimental design outcomes, the first-order model was proven as a practical correlation between selected factors and response. Further ANOVA analysis has revealed that only two out of six factors have a significant effect on ORG degradation, however ORG concentration and irradiation time indicated the significant effects sequentially. Maximum ORG degradation of approximately 96% was achieved by keeping process parameters in range, such as 1 g L⁻¹ loading of catalyst, 50 mg L⁻¹ concentration of ORG, 1.4 mol L⁻¹ concentration of H₂O₂ at pH 7 and a temperature of 30 °C. Kinetics of ORG degradation followed the pseudo first order, and almost complete degradation was achieved within 8 h. The effectiveness of the Bi₂MoO₆/H₂O₂ photo-Fenton system in degradation reactions is due to the higher number of photo-generated e- available on the catalyst surface as a result of their ability to inhibit recombination of e- and h+ pair. Full article

(This article belongs to the Special Issue Thermal and Photocatalytic Analysis of Nanomaterials)

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12 pages, 4447 KiB

Open AccessArticle

Experimental Study of Halloysite Nanofluids in Pool Boiling Heat Transfer

by Thong Le Ba, Ahmed Baqer, Mohammed Saad Kamel, Gyula Gróf, Vincent Otieno Odhiambo, Somchai Wongwises, Lezsovits Ferenc and Imre Miklós Szilágyi

Molecules 2022, 27(3), 729; https://doi.org/10.3390/molecules27030729 - 23 Jan 2022

Cited by 9 | Viewed by 2417

Abstract

Halloysite nanotube (HNT) which is cheap, natural, and easily accessible 1D clay, can be used in many applications, particularly heat transfer enhancement. The aim of this research is to study experimentally the pool boiling heat transfer (PBHT) performance of novel halloysite nanofluids at atmospheric pressure condition from typical horizontal heater. The nanofluids are prepared from halloysite nanotubes (HNTs) nanomaterials-based deionized water (DI water) with the presence of sodium hydroxide (NaOH) solution to control pH = 12 to obtain stable nanofluid. The nanofluids were prepared with dilute volume concentrations of 0.01–0.5 vol%. The performance of PBHT is studied via pool boiling curve and pool boiling heat transfer coefficient (PBHTC) from the typical heater which is the copper horizontal tube with a thickness of 1 mm and a diameter of 22 mm. The temperatures of the heated tube surface are measured to obtain the PBHTC. The results show an improvement of PBHTC for halloysite nanofluids compared to the base fluid. At 0.05 vol% concentration, HNT nanofluid has the best enhancement of 5.8% at moderate heat flux (HF). This indicates that HNT is a potential material in heat transfer applications. Full article

(This article belongs to the Special Issue Thermal and Photocatalytic Analysis of Nanomaterials)

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