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Coatings, Volume 6, Issue 1 (March 2016) – 13 articles

Cover Story (view full-size image): This review presents a summary of the main research achievements in the development of hybrid sol–gel coatings for corrosion protection of steel and aluminum substrates. A rational selection of the most relevant contributions was carried out in order to provide a reliable and a trustworthy analysis of the consolidated know-how and future perspectives for further development in this area. A comparative analysis between the potentialities of hybrid sol–gel coatings with the methods currently available in the mitigation of corrosion is also performed.View this paper.
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Article
Influence of Material Composition on Structural and Optical Properties of HfO2-TiO2 Mixed Oxide Coatings
Coatings 2016, 6(1), 13; https://doi.org/10.3390/coatings6010013 - 22 Mar 2016
Cited by 11 | Viewed by 3266
Abstract
In this paper the influence of material composition on the structural, surface and optical properties of HfO2-TiO2 mixed oxide coatings was investigated and discussed. Five sets of thin films were deposited using reactive magnetron sputtering: HfO2, TiO2 [...] Read more.
In this paper the influence of material composition on the structural, surface and optical properties of HfO2-TiO2 mixed oxide coatings was investigated and discussed. Five sets of thin films were deposited using reactive magnetron sputtering: HfO2, TiO2 and three sets of mixed HfO2-TiO2 coatings with various titanium content. The change in the material composition had a significant influence on the structural, surface and optical properties. All of the deposited coatings, except for (Hf0.55Ti0.45)Ox, were nanocrystalline with crystallites ranging from 6.7 nm to 10.8 nm in size. Scanning electron microscopy measurements revealed that surface of nanocrystalline thin films consisted of grains with different shapes and sizes. Based on optical transmission measurements, it was shown that thin films with higher titanium content were characterized by a higher cut-off wavelength, refractive index and lower optical band gap energy. The porosity and packing density were also determined. Full article
(This article belongs to the Special Issue Recent Advances in Optical Coatings)
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Review
Hybrid Sol-Gel Coatings: Smart and Green Materials for Corrosion Mitigation
Coatings 2016, 6(1), 12; https://doi.org/10.3390/coatings6010012 - 16 Mar 2016
Cited by 75 | Viewed by 9079
Abstract
Corrosion degradation of materials and metallic structures is one of the major issues that give rise to depreciation of assets, causing great financial outlays in their recovery and or prevention. Therefore, the development of active corrosion protection systems for metallic substrates is an [...] Read more.
Corrosion degradation of materials and metallic structures is one of the major issues that give rise to depreciation of assets, causing great financial outlays in their recovery and or prevention. Therefore, the development of active corrosion protection systems for metallic substrates is an issue of prime importance. The promising properties and wide application range of hybrid sol-gel-derived polymers have attracted significant attention over recent decades. The combination of organic polymers and inorganic materials in a single phase provides exceptional possibilities to tailor electrical, optical, anticorrosive, and mechanical properties for diverse applications. This unlimited design concept has led to the development of hybrid coatings for several applications, such as transparent plastics, glasses, and metals to prevent these substrates from permeation, mechanical abrasion, and corrosion, or even for decorative functions. Nevertheless, the development of new hybrid products requires a basic understanding of the fundamental chemistry, as well as of the parameters that influence the processing techniques, which will briefly be discussed. Additionally, this review will also summarize and discuss the most promising sol-gel coatings for corrosion protection of steel, aluminium, and their alloys conducted at an academic level. Full article
(This article belongs to the Special Issue Multifunctional Organic-Inorganic Hybrid Thin Films and Coatings)
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Article
Low Group Delay Dispersion Optical Coating for Broad Bandwidth High Reflection at 45° Incidence, P Polarization of Femtosecond Pulses with 900 nm Center Wavelength
Coatings 2016, 6(1), 11; https://doi.org/10.3390/coatings6010011 - 09 Mar 2016
Cited by 10 | Viewed by 4178
Abstract
We describe an optical coating design suitable for broad bandwidth high reflection (BBHR) at 45° angle of incidence (AOI), P polarization (Ppol) of femtosecond (fs) laser pulses whose wavelengths range from 800 to 1000 nm. Our design process is guided by quarter-wave HR [...] Read more.
We describe an optical coating design suitable for broad bandwidth high reflection (BBHR) at 45° angle of incidence (AOI), P polarization (Ppol) of femtosecond (fs) laser pulses whose wavelengths range from 800 to 1000 nm. Our design process is guided by quarter-wave HR coating properties. The design must afford low group delay dispersion (GDD) for reflected light over the broad, 200 nm bandwidth in order to minimize temporal broadening of the fs pulses due to dispersive alteration of relative phases between their frequency components. The design should also be favorable to high laser-induced damage threshold (LIDT). We base the coating on TiO2/SiO2 layer pairs produced by means of e-beam evaporation with ion-assisted deposition, and use OptiLayer Thin Film Software to explore designs starting with TiO2/SiO2 layers having thicknesses in a reverse chirped arrangement. This approach led to a design with R > 99% from 800 to 1000 nm and GDD < 20 fs2 from 843 to 949 nm (45° AOI, Ppol). The design’s GDD behaves in a smooth way, suitable for GDD compensation techniques, and its electric field intensities show promise for high LIDTs. Reflectivity and GDD measurements for the initial test coating indicate good performance of the BBHR design. Subsequent coating runs with improved process calibration produced two coatings whose HR bands satisfactorily meet the design goals. For the sake of completeness, we summarize our previously reported transmission spectra and LIDT test results with 800 ps, 8 ps and 675 fs pulses for these two coatings, and present a table of the LIDT results we have for all of our TiO2/SiO2 BBHR coatings, showing the trends with test laser pulse duration from the ns to sub-ps regimes. Full article
(This article belongs to the Special Issue Recent Advances in Optical Coatings)
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Review
Hybrid Organic/Inorganic Coatings Through Dual-Cure Processes: State of the Art and Perspectives
Coatings 2016, 6(1), 10; https://doi.org/10.3390/coatings6010010 - 02 Mar 2016
Cited by 27 | Viewed by 4377
Abstract
This paper reviews the current state of the art related to the synthesis and characterization of hybrid organic-inorganic (O/I) coatings obtained through the exploitation of dual-cure processes, which involve a photo-induced polymerization followed by a thermal treatment: this latter allows the occurrence of [...] Read more.
This paper reviews the current state of the art related to the synthesis and characterization of hybrid organic-inorganic (O/I) coatings obtained through the exploitation of dual-cure processes, which involve a photo-induced polymerization followed by a thermal treatment: this latter allows the occurrence of sol-gel reactions of suitable alkoxy precursors already embedded in the UV-curable system. After a brief introduction on hybrid organic-inorganic coatings, the first part of the review is focused on the design and feasibility issues provided by the dual-cure method, emphasizing the possibility of tuning the structure of the final hybrid network on the basis of the composition of the starting liquid mixture. Then, some recent examples of hybrid organic-inorganic networks are thoroughly described, showing their potential advances and the application fields to which they can be addressed. Full article
(This article belongs to the Special Issue Multifunctional Organic-Inorganic Hybrid Thin Films and Coatings)
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Article
Growth and Functionality of Cells Cultured on Conducting and Semi-Conducting Surfaces Modified with Self-Assembled Monolayers (SAMs)
Coatings 2016, 6(1), 9; https://doi.org/10.3390/coatings6010009 - 18 Feb 2016
Cited by 1 | Viewed by 4198
Abstract
Bioengineering of dermal and epidermal cells on surface modified substrates is an active area of research. The cytotoxicity, maintenance of cell phenotype and long-term functionality of human dermal fibroblast (HDF) cells on conducting indium tin oxide (ITO) and semi-conducting, silicon (Si) and gallium [...] Read more.
Bioengineering of dermal and epidermal cells on surface modified substrates is an active area of research. The cytotoxicity, maintenance of cell phenotype and long-term functionality of human dermal fibroblast (HDF) cells on conducting indium tin oxide (ITO) and semi-conducting, silicon (Si) and gallium arsenide (GaAs), surfaces modified with self-assembled monolayers (SAMs) containing amino (–NH2) and methyl (–CH3) end groups have been investigated. Contact angle measurements and infrared spectroscopic studies show that the monolayers are conformal and preserve their functional end groups. Morphological analyses indicate that HDFs grow well on all substrates except GaAs, exhibiting their normal spindle-shaped morphology and exhibit no visible signs of stress or cytoplasmic vacuolation. Cell viability analyses indicate little cell death after one week in culture on all substrates except GaAs, where cells died within 6 h. Cells on all surfaces proliferate except on GaAs and GaAs-ODT. Cell growth is observed to be greater on SAM modified ITO and Si-substrates. Preservation of cellular phenotype assessed through type I collagen immunostaining and positive staining of HDF cells were observed on all modified surfaces except that on GaAs. These results suggest that conducting and semi-conducting SAM-modified surfaces support HDF growth and functionality and represent a promising area of bioengineering research. Full article
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Review
Epoxy Sol-Gel Hybrid Thermosets
Coatings 2016, 6(1), 8; https://doi.org/10.3390/coatings6010008 - 03 Feb 2016
Cited by 40 | Viewed by 5906
Abstract
Sol-gel methodologies are advantageous in the preparation of hybrid materials in front of the conventional addition of nanoparticles, because of the fine dispersion of the inorganic phase that can be reached in epoxy matrices. In addition, the use of organoalkoxysilanes as coupling agents [...] Read more.
Sol-gel methodologies are advantageous in the preparation of hybrid materials in front of the conventional addition of nanoparticles, because of the fine dispersion of the inorganic phase that can be reached in epoxy matrices. In addition, the use of organoalkoxysilanes as coupling agents allows covalent linkage between organic and inorganic phases, which is the key point in the improvement of mechanical properties. The sol-gel process involves hydrolysis and condensation reactions under mild conditions, starting from hydrolysable metal alkoxides, generally alkoxy silanes. Using the sol-gel procedure, the viscosity of the formulation is maintained, which is an important issue in coating applications, whereas the transparency of the polymer matrix is also maintained. However, only the proper combination of the chemistries and functionalities of both organic and inorganic structures leads to thermosets with the desired characteristics. The adequate preparation of hybrid epoxy thermosets enables their improvement in characteristics such as mechanical properties (modulus, hardness, scratch resistance), thermal and flame resistance, corrosion and antimicrobial protection, and even optical performance among others. Full article
(This article belongs to the Special Issue Multifunctional Organic-Inorganic Hybrid Thin Films and Coatings)
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Review
Surface Treatments and Functional Coatings for Biocompatibility Improvement and Bacterial Adhesion Reduction in Dental Implantology
Coatings 2016, 6(1), 7; https://doi.org/10.3390/coatings6010007 - 27 Jan 2016
Cited by 98 | Viewed by 6275
Abstract
Surface modification of dental implants is a key process in the production of these medical devices, and especially titanium implants used in the dental practice are commonly subjected to surface modification processes before their clinical use. A wide range of treatments, such as [...] Read more.
Surface modification of dental implants is a key process in the production of these medical devices, and especially titanium implants used in the dental practice are commonly subjected to surface modification processes before their clinical use. A wide range of treatments, such as sand blasting, acid etching, plasma etching, plasma spray deposition, sputtering deposition and cathodic arc deposition, have been studied over the years in order to improve the performance of dental implants. Improving or accelerating the osseointegration process is usually the main goal of these surface processes, but the improvement of biocompatibility and the prevention of bacterial adhesion are also of considerable importance. In this review, we report on the research of the recent years in the field of surface treatments and coatings deposition for the improvement of dental implants performance, with a main focus on the osseointegration acceleration, the reduction of bacterial adhesion and the improvement of biocompatibility. Full article
Article
Antimicrobial Performance of Two Different Packaging Materials on the Microbiological Quality of Fresh Salmon
Coatings 2016, 6(1), 6; https://doi.org/10.3390/coatings6010006 - 27 Jan 2016
Cited by 17 | Viewed by 3715
Abstract
In the present research the antimicrobial activity of two active packaging materials on the spoilage microbiota of fresh salmon fillets was tested. A PET-coated film (PET: Polyethylene Terephthalate) containing lysozyme and lactoferrin was tested in parallel with a carvacrol-coextruded multilayer film. Salmon fillet [...] Read more.
In the present research the antimicrobial activity of two active packaging materials on the spoilage microbiota of fresh salmon fillets was tested. A PET-coated film (PET: Polyethylene Terephthalate) containing lysozyme and lactoferrin was tested in parallel with a carvacrol-coextruded multilayer film. Salmon fillet samples were stored up to four days at 0 and 5 °C, comparatively. The carvacrol multilayer film was found effective in preventing mesophiles and psychrotrophs at shorter storage time and at lower temperature (4.0 compared to 5.0 log CFU/g in the control sample—CFU: Colony Forming Units). Lysozyme/lactoferrin-coated PET was instead efficient in decreasing H2S-producing bacteria at longer storage time and higher temperature (2.7 instead of 4.7 log CFU/g in the control sample). Even if is not intended as a way to “clean” a contaminated food product, an active package solution can indeed contribute to reducing the microbial population in food items, thus lowering the risk of food-related diseases. Full article
(This article belongs to the Special Issue Functional Coatings for Food Packaging Applications)
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Editorial
Acknowledgement to Reviewers of Coatings in 2015
Coatings 2016, 6(1), 5; https://doi.org/10.3390/coatings6010005 - 22 Jan 2016
Viewed by 2122
Abstract
The editors of Coatings would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2015. [...] Full article
Article
Development of Antibacterial Composite Films Based on Isotactic Polypropylene and Coated ZnO Particles for Active Food Packaging
Coatings 2016, 6(1), 4; https://doi.org/10.3390/coatings6010004 - 22 Jan 2016
Cited by 22 | Viewed by 4211
Abstract
This study was aimed at developing new films based on isotactic polypropylene (iPP) for food packaging applications using zinc oxide (ZnO) with submicron dimension particles obtained by spray pyrolysis. To improve compatibility with iPP, the ZnO particles were coated with stearic acid (ZnOc). [...] Read more.
This study was aimed at developing new films based on isotactic polypropylene (iPP) for food packaging applications using zinc oxide (ZnO) with submicron dimension particles obtained by spray pyrolysis. To improve compatibility with iPP, the ZnO particles were coated with stearic acid (ZnOc). Composites based on iPP with 2 wt % and 5 wt % of ZnOc were prepared in a twin-screw extruder and then filmed by a calender. The effect of ZnOc on the properties of iPP were assessed and compared with those obtained in previous study on iPP/ZnO and iPP/iPPgMA/ZnO. For all composites, a homogeneous distribution and dispersion of ZnOc was obtained indicating that the coating with stearic acid of the ZnO particles reduces the surface polarity mismatch between iPP and ZnO. The iPP/ZnOc composite films have relevant antibacterial properties with respect to E. coli, higher thermal stability and improved mechanical and impact properties than the pure polymer and the composites iPP/ZnO and iPP/iPPgMA/ZnO. This study demonstrated that iPP/ZnOc films are suitable materials for potential application in the active packaging field. Full article
(This article belongs to the Special Issue Functional Coatings for Food Packaging Applications)
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Commentary
On Modulating Interfacial Structure towards Improved Anti-Icing Performance
Coatings 2016, 6(1), 3; https://doi.org/10.3390/coatings6010003 - 14 Jan 2016
Cited by 18 | Viewed by 5012
Abstract
The design of anti-icing surfaces presents an interface with high causal density that has been challenging to quantify in terms of individual contributions of various interactions and environmental factors. In this commentary, we highlight the role of interfacial water structure as uniquely expressing [...] Read more.
The design of anti-icing surfaces presents an interface with high causal density that has been challenging to quantify in terms of individual contributions of various interactions and environmental factors. In this commentary, we highlight the role of interfacial water structure as uniquely expressing the physico-chemical aspects of ice accretion. Recent work on the topic that focuses on control of interfacial structure is discussed along with results by our research group on wettability of chemically modified surfaces and the role of ions in modulating interfacial structure. Suggestions for systematic studies to understand the fundamental interactions at play in ice adhesion at interfaces are made especially in the under-explored areas of cooperative hydrogen bonding and the role of solvated counterions. Insights expected from such studies would contribute to design of robust anti-icing hierarchies. Full article
(This article belongs to the Special Issue Anti-Icing Coatings and Surfaces)
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Article
TiCl4 Barrier Process Engineering in Semiconductor Manufacturing
Coatings 2016, 6(1), 2; https://doi.org/10.3390/coatings6010002 - 12 Jan 2016
Cited by 4 | Viewed by 3437
Abstract
Titanium nitride (TiN) not only was utilized in the wear-resistant coatings industry but it was also adopted in barrier processes for semiconductor manufacturing. Barrier processes include the titanium (Ti) and TiN processes, which are commonly used as diffusion barriers in via/contact applications. However, [...] Read more.
Titanium nitride (TiN) not only was utilized in the wear-resistant coatings industry but it was also adopted in barrier processes for semiconductor manufacturing. Barrier processes include the titanium (Ti) and TiN processes, which are commonly used as diffusion barriers in via/contact applications. However, engineers frequently struggle at the via/contact module in the beginning of every technology node. As devices shrink, barrier processes become more challenging to overcome the both the physical fill-in and electrical performance requirements of advanced small via/contact plugs. The aim of this paper is to investigate various chemical vapor deposition (CVD) TiCl4-based barrier processes to serve the application of advanced small via/contact plugs and the metal gate processes. The results demonstrate that the plasma-enhanced chemical vapor deposition (PECVD) TiCl4-based Ti process needs to select a feasible process temperature to avoid Si surface corrosion by high-temperature chloride flow. Conventional high step coverage (HSC) CVD TiCl4-based TiN processes give much better impurity performance than metal organic chemical vapor deposition (MOCVD) TiN. However, the higher chloride content in HSC film may degrade the long-term reliability of the device. Furthermore, it is evidenced that a sequential flow deposition (SFD) CVD TiCl4-based process with multiple cycles can give much less chloride content, resulting in faster erase speeds and lower erase levels than that of conventional HSC TiN. Full article
(This article belongs to the Special Issue Trends in Coatings and Surface Technology—Feature Papers)
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Review
State of the Art in the Development and Properties of Protein-Based Films and Coatings and Their Applicability to Cellulose Based Products: An Extensive Review
Coatings 2016, 6(1), 1; https://doi.org/10.3390/coatings6010001 - 31 Dec 2015
Cited by 76 | Viewed by 7375
Abstract
There is increasing research towards the substitution of petrochemicals by sustainable components. Biopolymers such as proteins, polysaccharides, and lipids derive from a variety of crop sources and most promisingly from waste streams generated during their processing by the agro food industry. Among those, [...] Read more.
There is increasing research towards the substitution of petrochemicals by sustainable components. Biopolymers such as proteins, polysaccharides, and lipids derive from a variety of crop sources and most promisingly from waste streams generated during their processing by the agro food industry. Among those, proteins of different types such as whey, casein, gelatin, wheat gluten, soy protein or zein present a potential beyond the food and feed industry for the application in packaging. The general protein hydrophilicity promotes a good compatibility to polar surfaces, such as paper, and a good barrier to apolar gases, such as oxygen and carbon dioxide. The present review deals with the development of protein-based coatings and films. It includes relevant discussion for application in paper or board products, as well as an outlook on its future industrial potential. Proteins with suitable functionalities as food packaging materials are described as well as the different technologies for processing the coatings and the current state of the art about the coating formulations for selectively modulating barrier, mechanical, surface and end of life properties. Some insights onto regulations about packaging use, end of life and perspectives of such natural coating for decreasing the environmental impact of packages are given. Full article
(This article belongs to the Special Issue Coatings and Sustainability)
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