Special Issue "Thin Film Coatings for Multifunctional Applications"

A special issue of Coatings (ISSN 2079-6412).

Deadline for manuscript submissions: closed (30 June 2020).

Special Issue Editor

Prof. Dr. Rodica Vlǎdoiu
Website
Guest Editor
Department of Physics and Electronics, Faculty of Applied Science and Engineering, Ovidius University of Constanta, Mamaia Av. no 124, 900524 Constanta, Romania
Interests: thin films deposition; materials characterization; vacuum arc deposition technologies for nanstructures
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Special Issue Information

Dear Colleagues,

Thin film coatings are quickly developing, such that the surface modification of widespread used materials allows us to transform a material with poor properties into a functional product.

This Special Issue is focused on contributions that improve our scientific and mechanistic understanding of the characterization and performance of engineered surfaces and coatings, processing–structure–property–performance relationships, the design of coatings for specific applications, and size effects. Additional emphasis is given to multifunctional and nanocomposite coatings for extreme conditions, nanostructured coatings, lightening and photovoltaic applications, and advances in instrumentation and measurement techniques. This Special Issue will also be devoted to contributions on understanding the role of coating composition and structure in friction and wear reduction.

In particular, the topics of interest include but are not limited to the following:

  • New technology trends and applications;
  • Surfaces, interfaces, and thin films;
  • Processes for coating deposition;
  • Characterization techniques;
  • Experimental condensed matter physics;
  • Substrate influence and sample preparation.

Prof. Dr. Rodica Vlǎdoiu
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 papers will be 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. Coatings is an international peer-reviewed open access monthly 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 1800 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.

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Published Papers (9 papers)

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Research

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Open AccessArticle
Composition, Structure and Mechanical Properties of Industrially Sputtered Ta–B–C Coatings
Coatings 2020, 10(9), 853; https://doi.org/10.3390/coatings10090853 - 31 Aug 2020
Viewed by 778
Abstract
Ta–B–C coatings were non-reactively sputter-deposited in an industrial batch coater from a single segmented rotating cylindrical cathode employing a combinatorial approach. The chemical composition, morphology, microstructure, mechanical properties, and fracture resistance of the coatings were investigated. Their mechanical properties were linked to their [...] Read more.
Ta–B–C coatings were non-reactively sputter-deposited in an industrial batch coater from a single segmented rotating cylindrical cathode employing a combinatorial approach. The chemical composition, morphology, microstructure, mechanical properties, and fracture resistance of the coatings were investigated. Their mechanical properties were linked to their microstructure and phase composition. Coatings placed stationary in front of the racetrack of the target and those performing a 1-axis rotation around the substrate carousel are compared. Utilization of the substrate rotation has no significant effect on the chemical composition of the coatings deposited at the same position compared to the cathode. Whereas the morphology of coatings with corresponding chemical composition is similar for stationary as well as rotating samples, the rotating coatings exhibit a distinct multilayered structure with a repetition period in the range of nanometers despite utilizing a non-reactive process and a single sputter source. All the coatings are either amorphous, nanocomposite or nanocrystalline depending on their chemical composition. The presence of TaC, TaB, and/or TaB2 phases is identified. The crystallite size is typically less than 5 nm. The highest hardness of the coatings is associated with the presence of larger grains in a nanocomposite structure or formation of polycrystalline coatings. The number, density, and length of cracks observed after high-load indentation is on par with current optimized commercially available protective coatings. Full article
(This article belongs to the Special Issue Thin Film Coatings for Multifunctional Applications)
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Open AccessArticle
Digital Transformation Reduces Costs of the Paints and Coatings Development Process
Coatings 2020, 10(7), 703; https://doi.org/10.3390/coatings10070703 - 21 Jul 2020
Viewed by 843
Abstract
An essential characteristic of the new product development process is to develop a new marketable product in the shortest possible time with the lowest reasonable costs. Therefore, the key factor of the process is efficiency. The paints and coatings industry development process contain [...] Read more.
An essential characteristic of the new product development process is to develop a new marketable product in the shortest possible time with the lowest reasonable costs. Therefore, the key factor of the process is efficiency. The paints and coatings industry development process contain numerous laboratory tests to determine the appropriateness of new formulation. It is proven that digital transformation can reduce the number of laboratory tests and consequently shorten the throughput time of the development process. This raised the question of whether the faster development process also reduces the process’ cost, or they even increase due to information and communication technology implementation. Therefore, the research’s purpose was to determine whether reducing the number of laboratory tests, based on the implementation of information and communication technology (ICT), affects reducing costs in the paints and coatings development process. The conventional process and the redesigned process of paints and coatings development were used as the basis of the research. The comparative analysis of the costs incurred during the development process was made. The analysis compares the types and amount of incurred costs. The article proves that digital transformation has a significant impact on up to 48% on reducing costs of the paints and coatings development process. Full article
(This article belongs to the Special Issue Thin Film Coatings for Multifunctional Applications)
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Open AccessArticle
Antibacterial Efficiency of Stainless-Steel Grids Coated with Cu-Ag by Thermionic Vacuum Arc Method
Coatings 2020, 10(4), 322; https://doi.org/10.3390/coatings10040322 - 28 Mar 2020
Viewed by 793
Abstract
Autonomous smart natural ventilation systems (SVS) attached to the glass façade of living quarters and office buildings can help reducing the carbon footprint of city buildings in the future, especially during warm seasons and can represent an alternative to the conventional mechanical ventilation [...] Read more.
Autonomous smart natural ventilation systems (SVS) attached to the glass façade of living quarters and office buildings can help reducing the carbon footprint of city buildings in the future, especially during warm seasons and can represent an alternative to the conventional mechanical ventilation systems. The work performed in this manuscript focuses on the investigation of bacteria trapping and killing efficiency of stainless steel grids coated with a mixed layer of Cu-Ag. These grids are to be employed as decontamination filters for a smart natural ventilation prototype that we are currently building in our laboratory. The tested grids were coated with a mixed Cu-Ag layer using thermionic vacuum arc plasma processing technology. The fixed deposition geometry allowed the variation of Cu and Ag atomic concentration in coated layers as a function of substrate position in relation to plasma sources. The test conducted with air contaminated with a pathogen strain of staphylococcus aureus indicated that the filtering efficiency is influenced by two parameters: the pore size dimension and the coating layer composition. The results show that the highest filtering efficiency of 100% was obtained for fine pore (0.5 × 0.5 mm) grids coated with a mixed metallic layer composed of 65 at% Cu and 35 at% Ag. The second test performed only on reference grids and Cu-Ag (65–35 at%) under working conditions, confirm a similar filtering efficiency for the relevant microbiological markers. This particular sample was investigated from morphological, structural, and compositional point of view. The results show that the layer has a high surface roughness with good wear resistance and adhesion to the substrate. The depth profiles presented a uniform composition of Cu and Ag in the layer with small variations caused by changes in deposition rates during the coating process. Identification of the two metallic phases of the Cu and Ag in the layers evidences their crystalline nature. The calculated grain size of the nanocrystalline was in the range 14–21 nm. Full article
(This article belongs to the Special Issue Thin Film Coatings for Multifunctional Applications)
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Open AccessArticle
One-Step Synthesis of Graphene, Copper and Zinc Oxide Graphene Hybrids via Arc Discharge: Experiments and Modeling
Coatings 2020, 10(4), 308; https://doi.org/10.3390/coatings10040308 - 25 Mar 2020
Cited by 1 | Viewed by 810
Abstract
In this paper, we report on a modified arc process to synthetize graphene, copper and zinc oxide graphene hybrids. The anode was made of pure graphite or graphite mixed with metals or metal oxides. After applying a controlled direct current, plasma is created [...] Read more.
In this paper, we report on a modified arc process to synthetize graphene, copper and zinc oxide graphene hybrids. The anode was made of pure graphite or graphite mixed with metals or metal oxides. After applying a controlled direct current, plasma is created in the interelectrode region and the anode is consumed by eroding. Continuous and abundant flux of small carbon, zinc or copper species, issued from the anode at a relatively high temperature, flows through the plasma and condenses in the vicinity of a water-cooled cathode leading to few-layered graphene sheets and highly ordered carbon structures. When the graphite rod is filled with copper or zinc oxide nanoparticles, few layers of curved graphene films were anchored with spherical Cu and ZnO nanoparticles leading to a one-step process synthesis of graphene hybrids, which combine the synergetic properties of graphene along with nanostructured metals or semiconducting materials. The as-prepared samples were characterized by Raman spectroscopy, X-ray diffraction (XRD), spatially resolved electron energy loss spectroscopy (EELS), energy filtered elemental mapping and transmission electron microscopy (TEM). In addition to the experimental study, numerical simulations were performed to determine the velocity, temperature and chemical species distributions in the arc plasma under specific graphene synthesis conditions, thereby providing valuable insight into growth mechanisms. Full article
(This article belongs to the Special Issue Thin Film Coatings for Multifunctional Applications)
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Open AccessArticle
Organometallic Coatings for Electroluminescence Applications
Coatings 2020, 10(3), 277; https://doi.org/10.3390/coatings10030277 - 17 Mar 2020
Cited by 1 | Viewed by 755
Abstract
Organometallic compounds embedded in thin films are widely used for Organic Light-Emitting Diodes (OLED), but their functionalities are strongly correlated with the intrinsic properties of those films. Controlling the concentration of the organometallics in the active layers influences the OLED performances through the [...] Read more.
Organometallic compounds embedded in thin films are widely used for Organic Light-Emitting Diodes (OLED), but their functionalities are strongly correlated with the intrinsic properties of those films. Controlling the concentration of the organometallics in the active layers influences the OLED performances through the aggregation processes. These aggregations could lead to crystallization processes that significantly modify the efficiency of light emission in the case of electroluminescent devices. For functional devices with organometallic-based thin films, some improvements, such as the optimization of the charge injection, are needed to increase the light output. One dual emitter IrQ(ppy)2 organometallic compound was chosen for the aggregation correlations from a multitude of macromolecular organometallics that exist on the market for OLED applications. The choice of additional layers like conductive polymers or small molecules as host for the active layer may significantly influence the performances of the OLED based on the IrQ(ppy)2 organometallic compound. The use of the CBP small molecule layer may lead to an increase in the electroluminescence versus the applied voltage. Full article
(This article belongs to the Special Issue Thin Film Coatings for Multifunctional Applications)
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Open AccessArticle
Sol-Gel Processing of Bismuth Germanate Thin-Films
Coatings 2020, 10(3), 255; https://doi.org/10.3390/coatings10030255 - 09 Mar 2020
Viewed by 757
Abstract
This study aims to obtain uniform and homogeneous bismuth germanate oxides thin films by spin coating and using the sol-gel technique with different precursors, followed by low-temperature annealing at 560 °C. By using Bi(NO3)3 precursors, we have obtained transparent, yellowish [...] Read more.
This study aims to obtain uniform and homogeneous bismuth germanate oxides thin films by spin coating and using the sol-gel technique with different precursors, followed by low-temperature annealing at 560 °C. By using Bi(NO3)3 precursors, we have obtained transparent, yellowish thin films with a 200 nm thickness. The structural analysis of the initial sol-gel powder has shown the presence of two crystalline structures, the cubic Bi4Ge3O12 (BGO) and monoclinic Bi2GeO5 crystallites, which evolves towards the BGO structure after annealing. The elemental analysis confirmed the composition of the desired compound Bi4Ge3O12 with 60 wt % GeO2 and 40 wt % Bi2O5. On the other hand, by changing the precursor to (Bi(CH3COO)2, the film thickness increased to 500 nm thicker due to the high viscosity of the sol, and a dominant monoclinic Bi2GeO5 crystalline structure appeared. The elemental analysis revealed a nonstoichiometric composition with 38 wt % GeO2 and 62 wt % Bi2O3. Due to the low GeO2 phase content that reacted with metastable Bi2GeO5, we obtained cubic Bi4Ge3O12 as a secondary phase, with Bi2GeO5 as a dominant crystalline phase. The redshifts of both absorptions and emissions spectra peaks confirmed a different disorder structure as an interplay between the cubic Bi4Ge3O12 (BGO) and monoclinic Bi2GeO5 phases. Full article
(This article belongs to the Special Issue Thin Film Coatings for Multifunctional Applications)
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Open AccessFeature PaperArticle
Plasma Diagnostics in Reactive High-Power Impulse Magnetron Sputtering System Working in Ar + H2S Gas Mixture
Coatings 2020, 10(3), 246; https://doi.org/10.3390/coatings10030246 - 06 Mar 2020
Cited by 1 | Viewed by 736
Abstract
A reactive high-power impulse magnetron sputtering system (HiPIMS) working in Ar + H2S gas mixture was investigated as a source for the deposition of iron sulfide thin films. As a sputtering material, a pure Fe target was used. Plasma parameters in [...] Read more.
A reactive high-power impulse magnetron sputtering system (HiPIMS) working in Ar + H2S gas mixture was investigated as a source for the deposition of iron sulfide thin films. As a sputtering material, a pure Fe target was used. Plasma parameters in this system were investigated by a time-resolved Langmuir probe, radio-frequency (RF) ion flux probe, quartz crystal monitor modified for measurement of the ionized fraction of depositing particles, and by optical emission spectroscopy. A wide range of mass flow rates of reactive gas H2S was used for the investigation of the deposition process. It was found that the deposition rate of iron sulfide thin films is not influenced by the flow rate of H2S reactive gas fed into the magnetron discharge although the target is covered by iron sulfide compound. The ionized fraction of depositing particles decreases from r ≈ 40% to r ≈ 20% as the flow rate of H2S, QH2S, changes from 0 to 19 sccm at the gas pressure around p ≈ 1 Pa in the reactor chamber. The electron concentration ne measured by the Langmuir probe at the position of the substrate decreases over this change of QH2S from 1018 down to 1017 m−3 Full article
(This article belongs to the Special Issue Thin Film Coatings for Multifunctional Applications)
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Open AccessArticle
Superhydrophobic Surface with Gamma Irradiation Resistance and Self-Cleaning Effect in Air and Oil
Coatings 2020, 10(2), 106; https://doi.org/10.3390/coatings10020106 - 26 Jan 2020
Cited by 1 | Viewed by 833
Abstract
A superhydrophobic surface was synthesized by a combination of an epoxy/polymethylphenylsiloxane matrix and dual-scale morphology of silica (SiO2) nanoparticles. When the amount of SiO2 reached 30 wt.%, the as-prepared surface showed a high static water contact angle (WCA) of 154° [...] Read more.
A superhydrophobic surface was synthesized by a combination of an epoxy/polymethylphenylsiloxane matrix and dual-scale morphology of silica (SiO2) nanoparticles. When the amount of SiO2 reached 30 wt.%, the as-prepared surface showed a high static water contact angle (WCA) of 154° and a low sliding angle (SA) of 5°, excellent water repellency, and dirt-removal effects both in air and oil (hexamethylene). Even after exposure to as high as a 12.30 Mrad dose of gamma-rays, the composite surface still maintained its superior performance. Full article
(This article belongs to the Special Issue Thin Film Coatings for Multifunctional Applications)
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Review

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Open AccessFeature PaperReview
Thermionic Vacuum Arc—A Versatile Technology for Thin Film Deposition and Its Applications
Coatings 2020, 10(3), 211; https://doi.org/10.3390/coatings10030211 - 27 Feb 2020
Cited by 3 | Viewed by 911
Abstract
This review summarizes the more-than-25-years of development of the so-called thermionic vacuum arc (TVA). TVA is an anodic arc discharge in vapors of the material to be deposited; the energy for its melting is delivered by means of a focused electron beam. The [...] Read more.
This review summarizes the more-than-25-years of development of the so-called thermionic vacuum arc (TVA). TVA is an anodic arc discharge in vapors of the material to be deposited; the energy for its melting is delivered by means of a focused electron beam. The resulting material ions fall at the substrate where they form a well-adhesive layer; the ion energy is controllable. The deposited layers are, as a rule, free from droplets typical for cathodic arc deposition systems and the thermal stress of the substrates being coated is low. TVA is especially suitable for processing refractory metals, e.g., carbon or tungsten, however, in the course of time, various useful applications of this system originated. They include layers for fusion application, hard coatings, low-friction coatings, biomedical-applicable films, materials for optoelectronics, and for solid-state batteries. Apart from the diagnostic of the film properties, also the diagnostic of the TVA discharge itself as well as of the by TVA generated plasma was performed. The research and application of the TVA proceeds in broad international collaboration. At present, the TVA technology has found its firm place among the different procedures for thin film deposition. Full article
(This article belongs to the Special Issue Thin Film Coatings for Multifunctional Applications)
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