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Manufacturing, Characterization, and Applications of Functionally Gradient Nanomaterials

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A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Materials Science and Engineering".

Deadline for manuscript submissions: closed (20 November 2023) | Viewed by 20169

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Dr. Maria Amélia Ramos Loja

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Centro de Investigação em Modelação e Optimização de Sistemas Multifuncionais (CIMOSM), Instituto Superior de Engenharia de Lisboa (ISEL), Av. Conselheiro Emídio Navarro 1, 1959-007 Lisboa, Portugal
Interests: composite materials; advanced composites; numerical modeling; structural optimization; reverse engineering
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Special Issue Information

Dear Colleagues,

It is our pleasure to present this new Special Issue of Applied Sciences on “Manufacturing, Characterization, and Applications of Functionally Gradient Nanomaterials”, which will be open to submissions until 31 May 2021.

Over the years, nanomaterials and nanocomposites research has drawn the attention of many researchers in a wide variety of scientific and technological fields, ranging from medical sciences to engineering and from design to manufacturing, leading to significant advances and published work in the development of new theoretical, experimental, and manufacturing techniques.

Nanocomposites, as the name suggests, result from the inclusion of nanoparticles in a continuous material phase. As in other composite materials, these nano-inclusions also maintain their own properties; however, as a whole, the resulting nanocomposite can provide improved material properties, and depending on the phases’ involved, a multifunctional character can be also achieved. Graded distributions of such nano-inclusions may constitute an additional design variable and contribute to a better fit among materials design and manufacturing, and functional materials’ capabilities’ and structures’ operating requirements.

Therefore, design and manufacturing of functionally graded nanomaterials in close relationship with their capabilities and performance assessment, either experimentally or theoretically, constitute very relevant technological and scientific topics.

This Special Issue aims to constitute a dissemination vehicle of recent research in the wide area of manufacturing, characterization and applications of functionally gradient nanocomposites, welcoming the whole diversity of perspectives this topic can be looked at.

Hence, it is our pleasure to invite you to consider submitting a manuscript on your recent work for this Special Issue. Full papers, communications and reviews are all welcome.

We look forward to receiving your valuable contribution.

Dr. Maria Amélia Ramos Loja
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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. Applied Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

Nanocomposites
Nanomaterials
Functionally graded nanocomposites
Manufacturing techniques and processes
Nanocomposites and nanomaterials characterization
Multifunctional nanocomposites
Multiscale materials

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Published Papers (10 papers)

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Research

17 pages, 10172 KiB

Open AccessArticle

Production and Characterization of Cu/CNT Nanocomposites

by Íris Carneiro, Beatriz Monteiro, Bernardo Ribeiro, José V. Fernandes and Sónia Simões

Appl. Sci. 2023, 13(6), 3378; https://doi.org/10.3390/app13063378 - 7 Mar 2023

Cited by 7 | Viewed by 2102

Abstract

In this research, copper nanocomposites reinforced with carbon nanotubes (CNTs) were produced by ultrasonication and conventional sintering, followed by cold rolling. These nanocomposites may be good candidates due to their excellent properties for components in the electrical, electronics, or aerospace industries with highly demanding requirements. The main objectives of this work were to produce and characterize the Cu/CNT nanocomposites, identify the strengthening mechanisms, and study the deformation behavior of the nanocomposites during cold rolling. The nanocomposites exhibited an improvement in hardness and tensile strength of 17 and 67%, respectively, attesting to the strengthening effect of the reinforced material. The yield strength of the nanocomposites was determined considering different mechanisms: (1) load transfer, (2) grain refinement or texture, (3) dislocation, and (4) Orowan strengthening mechanisms. The microstructural and calculated results show that the mechanism that contributes the most to the increase in the properties of the nanocomposite is the load transfer. The nanocomposites show a different texture evolution of the Cu matrix during cold rolling. This can be due to differences in the active slip planes between the matrix and the nanocomposite, which affects the lattice rotation. Full article

(This article belongs to the Special Issue Manufacturing, Characterization, and Applications of Functionally Gradient Nanomaterials)

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15 pages, 4620 KiB

Open AccessArticle

Influence of Perfluorooctanoic Acid on Structural, Morphological, and Optical Properties of Hybrid Silica Coatings on Glass Substrates

by Violeta Purcar, Valentin Rădiţoiu, Florentina Monica Raduly, Alina Rădiţoiu, Simona Căprărescu, Adriana Nicoleta Frone, Raluca Şomoghi, Mihai Anastasescu, Hermine Stroescu and Cristian-Andi Nicolae

Appl. Sci. 2023, 13(3), 1669; https://doi.org/10.3390/app13031669 - 28 Jan 2023

Cited by 2 | Viewed by 1587

Abstract

In recent years, various coatings based on fluorinated materials, used in a commercial application, have been created through many preparation routes. However, the techniques utilized to realize these coatings required either expensive and complex equipment, imply multiple manufacturing steps, or are time- or cost-consuming. In this paper, the major target was to develop fluorinated hybrid coatings presenting sustainable hydrophobicity and good transparency simultaneously. The sol–gel method was proposed to obtain these fluorinated hybrid coatings because it does not require expensive equipment, or the existence of stabilizing agents that reduce the storage period, it consumes less energy, and it is easy to implement. The influence of perfluorooctanoic acid, utilized in the sol–gel processing of hybrid silica materials, on the structural, morphological, and optical properties of coatings deposited on glass substrates, was evaluated. Different silane precursors (tetraethyl orthosilicate (TEOS), triethoxymethylsilane (MTES), and trimethoxyhexadecylsilane (HDTMES)) were utilized to synthesize hybrid silica materials. The properties of the obtained materials were characterized by FTIR, UV–Vis, TEM, TGA, AFM, Ellipsometry, and Contact Angle analyses. FTIR spectroscopy shows the formation of a silica network tailored with organofunctional and fluoroalkyl groups. The fluorinated silica coatings presented smooth surfaces and good transparency, with a transmittance of ~90% in the visible range. It was found that the fluorinated silica materials improved the coating’s hydrophobicity (~110° in contact angle with water). These fluorinated silica materials can create multifunctional structures with antireflective and hydrophobic coatings for possible optical devices. Full article

(This article belongs to the Special Issue Manufacturing, Characterization, and Applications of Functionally Gradient Nanomaterials)

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8 pages, 2247 KiB

Open AccessCommunication

Phase-Pure Epitaxial b-Axis-Oriented Bronze TiO₂ Films

by Andreas Herklotz, Frank Herklotz and Florina Stefania Rus

Appl. Sci. 2023, 13(1), 209; https://doi.org/10.3390/app13010209 - 24 Dec 2022

Viewed by 1579

Abstract

We demonstrate the heteroepitaxial growth of phase-pure bronze-phase TiO₂ films using pulsed laser deposition on MgAl₂O₄ single-crystal substrates. While the growth on cubic substrates with smaller lattice parameters favors the stabilization of an out-of-plane-oriented anatase phase, and the use of substrates with larger lattice parameters leads to formation of the rutile phase, MgAl₂O₄ lies in a narrow intermediate range where the bronze phase is stabilized. X-ray diffraction shows that the b-axis is oriented out-of-plane, while the a–c lattice plane lies within the film plane. The bronze films show twinned domains due to their monoclinic structure that are aligned along all four in-plane directions of the MgAl₂O₄ lattice. In a subsequent step, TiO₂ films are grown on top of MgAl₂O₄-buffered MgO single crystals in order to demonstrate a route to stabilize the bronze phase on a larger variety of substrates. The growth of bronze-type TiO₂ films with the unique, open, one-dimensional framework aligned along the film normally may allow for the investigation of its basic functional properties related to ion diffusion that cannot otherwise be studied easily in other crystal forms. Full article

(This article belongs to the Special Issue Manufacturing, Characterization, and Applications of Functionally Gradient Nanomaterials)

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15 pages, 2690 KiB

Open AccessArticle

Influence of Process Parameters and Reducing Agent on the Size of MoS₂ Nanoparticles Obtained in Impinging Jet Reactor

by Zuzanna Bojarska, Mateusz Mężydło, Marta Mazurkiewicz-Pawlicka and Łukasz Makowski

Appl. Sci. 2022, 12(21), 11293; https://doi.org/10.3390/app122111293 - 7 Nov 2022

Viewed by 1758

Abstract

Molybdenum disulfide (MoS₂) is an emerging material with exciting properties. Many consider it an excellent catalyst, particularly for hydrogen evolution reaction. Currently, it is used on a larger scale as a lubricant. The size of MoS₂ is a crucial parameter defining its properties. A preparation method that is easily scalable and cheap is currently being sought. A solution might be a wet chemical synthesis method carried out in an impinging jet reactor. The simple design of the reactor and the possibility of continuous operation make this method unique. In this study, the influence of the reactor was investigated using numerical simulations. The S-type reactor showed better mixing and more control over the working conditions than T-type. Therefore, the S-type reactor was chosen as better for nanoparticle synthesis. We also investigated the influence of the process conditions on the size of the precipitated MoS₂ particles. The best operating conditions (i.e., Mo concentration of 0.2 mol/m³, reagent flow velocity of 20 mL/min, reaction temperature of 20 °C) were chosen to obtain the smallest particles (~200 µm). Additionally, two different reducing agents were also tested. The use of formic acid allowed obtaining smaller particle sizes but these were less stable than in the case of citric acid. Full article

(This article belongs to the Special Issue Manufacturing, Characterization, and Applications of Functionally Gradient Nanomaterials)

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10 pages, 18016 KiB

Open AccessArticle

In Situ Annealing Behavior of Cu Thin Films Deposited over Co-W Diffusion Barrier Layers

by Bruno M. C. Oliveira, Ruben F. Santos and Manuel F. Vieira

Appl. Sci. 2022, 12(19), 9778; https://doi.org/10.3390/app12199778 - 28 Sep 2022

Viewed by 1798

Abstract

The development of new materials for the electronics industry has been in focus in recent years, as circuit miniaturization poses challenges for conventional solutions. Dewetting of Cu films over diffusion-barrier layers has fostered an interest in developing new solutions with lower interfacial energies, to withstand processing and service life. Co-W is a candidate material for seedless Cu-interconnect deposition, but its behavior during annealing is still not properly addressed. This study used an in situ scanning-electron-microscopy (SEM) approach to assess how heating rates affect dewetting behavior, as well as to determine the limits of annealing of 40 nm-thick Cu films deposited over this substrate. The 10 °C/min heating rate used showed copper dewetting starting at 450 °C, whereas the higher 30 °C/min rate induced dewetting at 400 °C. The Cu film deposited over Ta exhibited slightly different dewetting, with its onset starting earlier, but developing a slower progression throughout the temperature range analyzed in the annealing treatments. Full article

(This article belongs to the Special Issue Manufacturing, Characterization, and Applications of Functionally Gradient Nanomaterials)

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16 pages, 12341 KiB

Open AccessArticle

Deformation Behaviour of Cold-Rolled Ni/CNT Nanocomposites

by Íris Carneiro, José V. Fernandes and Sónia Simões

Appl. Sci. 2022, 12(19), 9471; https://doi.org/10.3390/app12199471 - 21 Sep 2022

Cited by 4 | Viewed by 1638

Abstract

Metal matrix nanocomposites (MMNCs) reinforced by carbon nanotubes (CNTs) are good candidates to produce structural components in the mobility industry, given their unique properties. The manufacture of these components can involve plastic deformation. Therefore, it is crucial to understand whether reinforcement can influence the deformation behaviour of these nanocomposites. Thus, this work aims to study the deformation behaviour of MMNCs, given their importance and the lack of studies on this topic. Although nickel is not the most widely used metal as a matrix of nanocomposites, it presents mechanical properties superior to other matrices, such as aluminium. In addition, this metal has proven to establish a strong interface and integration of carbon nanotubes, making it an exciting material for the production and study of these nanocomposites. In that sense, nickel matrix nanocomposites are reinforced by 1.00 %vol. CNTs were produced by powder metallurgy using ultrasonication as a dispersion/mixture method. For comparison purposes, a nickel matrix was produced under the same conditions. Samples with and without CNTs were cold-rolled with thickness reductions between 10 and 60% (logarithmic strains between 0.11 and 0.92) to investigate the deformation behaviour. Microstructural characterization was performed using scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD). Microhardness tests were applied to evaluate their mechanical properties. The results revealed that the nanocomposites exhibited a softening for small strains (0.11 and 0.22). This decrease in hardness was attributed to the decline in dislocation density observed by EBSD, due to the rearrangement and annihilation of pre-existing dislocations that originated during production. A possible inversion can explain the decrease in dislocation density when minor strains are applied in the dislocation or deformation trajectory, known as the Bauschinger effect. The difference in the texture evolution of the nanocomposites can be explained by the initial crystallographic orientations, which are influenced by the presence of CNTs. Full article

(This article belongs to the Special Issue Manufacturing, Characterization, and Applications of Functionally Gradient Nanomaterials)

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6 pages, 4446 KiB

Open AccessCommunication

Electrothermally Activated CNT/GNP-Doped Anti-icing and De-Icing Systems: A Comparison Study of 3D Printed Circuits versus Coatings

by Alejandro Cortés, Alberto Jiménez-Suárez, Alejandro Ureña, Silvia G. Prolongo and Mónica Campo

Appl. Sci. 2022, 12(17), 8875; https://doi.org/10.3390/app12178875 - 4 Sep 2022

Cited by 1 | Viewed by 1432

Abstract

The present work studies the electrical and electrothermal properties of CNT/GNP-doped nanocomposites for optimizing their anti-icing and de-icing capabilities. Here, a comparison between 3D-printed circuits and coatings based on these materials is carried out. In this regard, the higher electrical conductivity that is achieved by the specimens when increasing the nanoparticle content and the higher cross-sectional area of the coatings with regard to the 3D-printed circuits induces a higher heat generated by the Joule’s effect. Moreover, the successful de-icing test performed by the specimen with the highest self-heating capability, evinces that the studied nanocomposites are suitable for de-icing purposes. Full article

(This article belongs to the Special Issue Manufacturing, Characterization, and Applications of Functionally Gradient Nanomaterials)

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11 pages, 3950 KiB

Open AccessArticle

Photosensitivity of Infrared Glasses under Femtosecond Laser Direct Writing for mid-IR Applications

by Pierre Delullier, Laurent Calvez, Guillaume Druart, Florence De La Barrière, Christophe Humbert, Bertrand Poumellec and Matthieu Lancry

Appl. Sci. 2022, 12(17), 8813; https://doi.org/10.3390/app12178813 - 1 Sep 2022

Cited by 3 | Viewed by 1739

Abstract

Chalcogenide glasses are increasingly being developed for photonic applications, particularly in the field of mid-infrared optical imaging. In this paper, we study the photosensitivity of one chalcogenide to direct femtosecond laser writing and its possible applications to micro-optics. Particular attention has been paid to the creation of phase changes and related refractive index variations. This chalcogenide glass was compared with two commercial heavy oxide glasses: Schott SF10 and Corning 9754. We observed different types of permanent modifications depending on the writing speed and the laser pulse energy. Index variations were measured at

Δ n > + 0.055

in the chalcogenide glass while maintaining spectral transmission similar to the pristine materials before irradiation. This provides a good candidate to design optical components for infrared application and helps to unlock the potential of the femtosecond laser direct writing technique to implement at high writing speed and high index changes with low optical losses. Full article

(This article belongs to the Special Issue Manufacturing, Characterization, and Applications of Functionally Gradient Nanomaterials)

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10 pages, 3336 KiB

Open AccessArticle

Electrofenton with Reticular Vitreous Carbon and Iron Oxide Nanoparticles for Dye Removal: A Preliminary Study

by Fernanda L. Rivera, Nieves Menendez, Eva Mazarío and Pilar Herrasti

Appl. Sci. 2022, 12(16), 8293; https://doi.org/10.3390/app12168293 - 19 Aug 2022

Cited by 3 | Viewed by 1594

Abstract

In this work, an RVC electrode coated with magnetic iron oxide nanoparticles was used for the degradation of methylene blue as a model dye. The electrofenton process was carried out by the reduction of oxygen dissolved in the electrolyte on the modified RVC electrode to produce hydrogen peroxide. The presence of the magnetite/maghemite nanoparticles in the structure produces the formation of OH^∙ radicals that oxidize methylene blue. The RVC/coated was prepared by two different methodologies: Methodology A: by immersion of the electrode in a solution saturated with magnetite nanoparticles; and Methodology B: by electrochemical synthesis. Scanning electron microscopy, X-ray diffraction and Mössbauer spectroscopy shows a uniform coating of the electrode. The Mössbauer spectroscopy determines the only presence of maghemite using methodology A and the presence of 60% of magnetite and a 40% of maghemite when methodology B was used. The dipping methodology is the one that has provided the best results in the electrofenton degradation of methylene blue, obtaining a 100% removal after 35 min, applying a current of 100 mA in a 20 mg L⁻¹ solution of methylene blue, and a concentration of 50 mM sodium sulfate. Full article

(This article belongs to the Special Issue Manufacturing, Characterization, and Applications of Functionally Gradient Nanomaterials)

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20 pages, 6189 KiB

Open AccessArticle

α-MnO₂ Nanowire Structure Obtained at Low Temperature with Aspects in Environmental Remediation and Sustainable Energy Applications

by Bogdan-Ovidiu Taranu, Stefan Danica Novaconi, Madalina Ivanovici, João Nuno Gonçalves and Florina Stefania Rus

Appl. Sci. 2022, 12(13), 6821; https://doi.org/10.3390/app12136821 - 5 Jul 2022

Cited by 10 | Viewed by 3841

Abstract

Hydrothermally obtained α-MnO₂ nanowire characterizations confirm the tetragonal crystalline structure that is several micrometers long and 20–30 nm in diameter with narrow distributions in their dimensions. The absorption calculated from diffuse reflectance of α-MnO₂ occurred in the visible region ranging from 400 to 550 nm. The calculated band gap with Quantum Espresso using HSE approximation is ~2.4 eV for the ferromagnetic case, with a slightly larger gap of 2.7 eV for the antiferromagnetic case, which is blue-shifted as compared to the experimental. The current work also illustrates the transformations that occur in the material under heat treatment during TGA analysis, with the underlying mechanism. Electrochemical studies on graphite supports modified with α-MnO₂ compositions revealed the modified electrode with the highest electric double-layer capacitance of 3.444 mF cm⁻². The degradation rate of an organic dye—rhodamine B (RhB)—over the compound in an acidic medium was used to examine the catalytic and photocatalytic activities of α-MnO₂. The peak shape changes in the time-dependent visible spectra of RhB during the photocatalytic reaction were more complex and progressive. In two hours, RhB degradation reached 97% under sun irradiation and 74% in the dark. Full article

(This article belongs to the Special Issue Manufacturing, Characterization, and Applications of Functionally Gradient Nanomaterials)

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