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Coatings, Volume 5, Issue 2 (June 2015) , Pages 95-231

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Cover Story (view full-size image) In the present work, we investigated the photocatalytic activity of a TiO2 nanocoating (aqueous [...] Read more.
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Open AccessArticle
Preservation of Historical Stone Surfaces by TiO2 Nanocoatings
Coatings 2015, 5(2), 222-231; https://doi.org/10.3390/coatings5020222 - 19 Jun 2015
Cited by 13 | Viewed by 2340
Abstract
We proposed the application of titanium dioxide (TiO2) for the preservation of historical (architectural, monumental, archaeological) stone surfaces. Solar light can activate the photocatalytic effect of TiO2 nanoparticles: heterogeneous photocatalysis is the key factor for the development of self-cleaning, depolluting [...] Read more.
We proposed the application of titanium dioxide (TiO2) for the preservation of historical (architectural, monumental, archaeological) stone surfaces. Solar light can activate the photocatalytic effect of TiO2 nanoparticles: heterogeneous photocatalysis is the key factor for the development of self-cleaning, depolluting and biocidal treatments able to photochemically degrade external damaging materials and prolong the durability of treated substrates, maintaining their original aspect and limiting ordinary cleaning activities. In this study, TiO2 nanoparticles dispersed in an aqueous colloidal suspension were applied directly on travertine, a light-colored limestone, by spray-coating in order to obtain a nanometric film on stone samples. To assess the feasibility of use of TiO2, we studied the characteristics of the nanocoating-stone system by monitoring the microscopic features of the coatings, the aesthetical changes induced to coated surfaces and the self-cleaning efficiency. We also monitored the self-cleaning ability over time during an accelerated ageing process to evaluate the durability of TiO2-based treatments. We confirmed both compatibility and effectiveness of TiO2 coating in the short term, anyway its efficiency decreased after artificial ageing. Further studies are necessary to better evaluate and eventually improve the stability of self-cleaning efficiency over prolonged time for outdoor stone surfaces. Full article
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Open AccessEditorial
Coatings Best Paper Award 2015
Coatings 2015, 5(2), 219-221; https://doi.org/10.3390/coatings5020219 - 19 Jun 2015
Cited by 1 | Viewed by 1775
Abstract
With the start of 2015, Coatings is instituting an annual award to recognize outstanding papers related to coatings and surface engineering that meet the aims, scope and high standards of this journal. [...] Full article
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Open AccessReview
Electrodeposition of Alloys and Compounds in the Era of Microelectronics and Energy Conversion Technology
Coatings 2015, 5(2), 195-218; https://doi.org/10.3390/coatings5020195 - 17 Jun 2015
Cited by 37 | Viewed by 3153
Abstract
Electrochemical deposition methods are increasingly being applied to advanced technology applications, such as microelectronics and, most recently, to energy conversion. Due to the ever growing need for device miniaturization and enhanced performance, vastly improved control of the growth process is required, which in [...] Read more.
Electrochemical deposition methods are increasingly being applied to advanced technology applications, such as microelectronics and, most recently, to energy conversion. Due to the ever growing need for device miniaturization and enhanced performance, vastly improved control of the growth process is required, which in turn necessitates a better understanding of the fundamental phenomena involved. This overview describes the current status of and latest advances in electrodeposition science and technology. Electrochemical growth phenomena are discussed at the macroscopic and atomistic scale, while particular attention is devoted to alloy and compound formation, as well as surface-limited processes. Throughout, the contribution of Professor Foresti and her group to the understanding of electrochemical interfaces and electrodeposition, is highlighted. Full article
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Open AccessArticle
Effects of Bell Speed and Flow Rate on Evaporation of Water Spray from a Rotary Bell Atomizer
Coatings 2015, 5(2), 186-194; https://doi.org/10.3390/coatings5020186 - 29 May 2015
Cited by 4 | Viewed by 2102
Abstract
A phase doppler anemometer (PDA) was used to determine the effects of evaporation on water spray for three rotary bell atomizer operational variable parameters: shaping air, bell speed and liquid flow. Shaping air was set at either 200 standard liters per minute (L/min) [...] Read more.
A phase doppler anemometer (PDA) was used to determine the effects of evaporation on water spray for three rotary bell atomizer operational variable parameters: shaping air, bell speed and liquid flow. Shaping air was set at either 200 standard liters per minute (L/min) or 300 L/min, bell speed was set to 30, 40 or 50 thousand rotations per minute (krpm) and water flow rate was varied between 100, 200 or 300 cubic centimeters per minute (cm3/min). The total evaporation between 22.5 and 37.5 cm from the atomizer (cm3/s) was calculated for all the combinations of those variables. Evaporation rate increased with higher flow rate and bell speed but no statistically significant effects were obtained for variable shaping air on interactions between parameters. Full article
(This article belongs to the Special Issue Innovative Coatings for Automotive Industry)
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Open AccessArticle
Deposition of High Conductivity Low Silver Content Materials by Screen Printing
Coatings 2015, 5(2), 172-185; https://doi.org/10.3390/coatings5020172 - 12 May 2015
Cited by 5 | Viewed by 2530
Abstract
A comprehensive experimental investigation has been carried out into the role of film thickness variation and silver material formulation on printing capability in the screen printing process. A full factorial experiment was carried out where two formulations of silver materials were printed through [...] Read more.
A comprehensive experimental investigation has been carried out into the role of film thickness variation and silver material formulation on printing capability in the screen printing process. A full factorial experiment was carried out where two formulations of silver materials were printed through a range of screens to a polyester substrate under a set of standard conditions. The materials represented a novel low silver content (45%–49%) polymer material and traditional high silver content (65%–69%) paste. The resultant prints were characterised topologically and electrically. The study shows that more cost effective use of the silver in the ink was obtained with the low silver polymer materials, but that the electrical performance was more strongly affected by the mesh being used (and hence film thickness). Thus, while optimum silver use could be obtained using materials with a lower silver content, this came with the consequence of reduced process robustness. Full article
(This article belongs to the Special Issue Trends in Coatings and Surface Technology—Feature Papers)
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Open AccessArticle
Correlation of Growth and Surface Properties of Poly(\(p\)-xylylenes) to Reaction Conditions
Coatings 2015, 5(2), 142-171; https://doi.org/10.3390/coatings5020142 - 08 May 2015
Cited by 3 | Viewed by 2517
Abstract
Parylene, a non-critical, non-toxic layer material, which is not only a candidate for low-\(K\) dielectrics, but also well suited for long-term applications in the human body, has been deposited by (plasma-enhanced) chemical vapor deposition of the monomeric species. To that end, a specially-designed [...] Read more.
Parylene, a non-critical, non-toxic layer material, which is not only a candidate for low-\(K\) dielectrics, but also well suited for long-term applications in the human body, has been deposited by (plasma-enhanced) chemical vapor deposition of the monomeric species. To that end, a specially-designed reactor exhibiting a cracker tube at its entrance, which serves as the upstream control, and a cooling trap in front of the downstream control has been applied. The process of polymerization has been traced and is explained by evaporating the dimeric species followed by dissociation in the cracker at elevated temperatures and, eventually, to the coating of the polymeric film in terms of thermodynamics. Alternatively, the process of dissociation has been accomplished applying a microwave plasma. In both cases, the monomerization is controlled by mass spectrometry. The window for surface polymerization could be clearly defined in terms of a factor of dilution by an inert gas for the chemical vapor deposition (CVD) case and in the case of plasma-enhanced chemical vapor deposition (PECVD), additionally by the power density. The characterization of the layer parameters has been carried out by several analytical tools: scanning electron microscopy and atomic force microscopy to determine the surface roughness and density and depth of voids in the film, which influence the layer capacitance and deteriorate the breakdown voltage, a bulk property. The main issue is the conduct against liquids between the two borders' hydrophilic and hydrophobic conduct, but also the super-hydrophobic character, which is the condition for the Lotus effect. The surface tension has been evaluated by contact angle measurements. Fourier-transform infrared spectroscopy has proven the conservation of all of the functional groups during polymerization. Full article
(This article belongs to the Special Issue Trends in Coatings and Surface Technology—Feature Papers)
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Open AccessArticle
Influence of Experimental Parameters Using the Dip-Coating Method on the Barrier Performance of Hybrid Sol-Gel Coatings in Strong Alkaline Environments
Coatings 2015, 5(2), 124-141; https://doi.org/10.3390/coatings5020124 - 30 Apr 2015
Cited by 8 | Viewed by 2529
Abstract
Previous studies have shown that the barrier effect and the performance of organic-inorganic hybrid (OIH) sol-gel coatings are highly dependent on the coating deposition method as well as on the processing conditions. However, studies on how the coating deposition method influences the barrier [...] Read more.
Previous studies have shown that the barrier effect and the performance of organic-inorganic hybrid (OIH) sol-gel coatings are highly dependent on the coating deposition method as well as on the processing conditions. However, studies on how the coating deposition method influences the barrier properties in alkaline environments are scarce. The aim of this experimental research was to study the influence of experimental parameters using the dip-coating method on the barrier performance of an OIH sol-gel coating in contact with simulated concrete pore solutions (SCPS). The influence of residence time (Rt), a curing step between each dip step and the number of layers of sol-gel OIH films deposited on hot-dip galvanized steel to prevent corrosion in highly alkaline environments was studied. The barrier performance of these OIH sol-gel coatings, named U(400), was assessed in the first instants of contact with SCPS, using electrochemical impedance spectroscopy and potentiodynamic methods. The durability and stability of the OIH coatings in SCPS was monitored during eight days by macrocell current density. The morphological characterization of the surface was performed by Scanning Electronic Microscopy before and after exposure to SCPS. Glow Discharge Optical Emission Spectroscopy was used to investigate the thickness of the U(400) sol-gel coatings as a function of the number of layers deposited with and without Rt in the coatings thickness. Full article
(This article belongs to the Special Issue Trends in Coatings and Surface Technology—Feature Papers)
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Open AccessArticle
The Effect of Process Parameters on Twin Wire Arc Spray Pattern Shape
Coatings 2015, 5(2), 115-123; https://doi.org/10.3390/coatings5020115 - 20 Apr 2015
Cited by 3 | Viewed by 2482
Abstract
A design of experiments approach was used to describe process parameter—spray pattern relationships in the Twin Wire Arc process using zinc feed stock in a TAFA 8835 (Praxair, Concord, NH, USA) spray torch. Specifically, the effects of arc current, primary atomizing gas pressure, [...] Read more.
A design of experiments approach was used to describe process parameter—spray pattern relationships in the Twin Wire Arc process using zinc feed stock in a TAFA 8835 (Praxair, Concord, NH, USA) spray torch. Specifically, the effects of arc current, primary atomizing gas pressure, and secondary atomizing gas pressure on spray pattern size, spray pattern flatness, spray pattern eccentricity, and coating deposition rate were investigated. Process relationships were investigated with the intent of maximizing or minimizing each coating property. It was determined that spray pattern area was most affected by primary gas pressure and secondary gas pressure. Pattern eccentricity was most affected by secondary gas pressure. Pattern flatness was most affected by primary gas pressure. Coating deposition rate was most affected by arc current. Full article
(This article belongs to the Special Issue Trends in Coatings and Surface Technology—Feature Papers)
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Open AccessArticle
Antibiofilm Activity of Epoxy/Ag-TiO2 Polymer Nanocomposite Coatings against Staphylococcus Aureus and Escherichia Coli
Coatings 2015, 5(2), 95-114; https://doi.org/10.3390/coatings5020095 - 14 Apr 2015
Cited by 15 | Viewed by 4078
Abstract
Dispersion of functional inorganic nano-fillers like TiO2 within polymer matrix is known to impart excellent photobactericidal activity to the composite. Epoxy resin systems with Ag+ ion doped TiO2 can have combination of excellent biocidal characteristics of silver and the photocatalytic [...] Read more.
Dispersion of functional inorganic nano-fillers like TiO2 within polymer matrix is known to impart excellent photobactericidal activity to the composite. Epoxy resin systems with Ag+ ion doped TiO2 can have combination of excellent biocidal characteristics of silver and the photocatalytic properties of TiO2. The inorganic antimicrobial incorporation into an epoxy polymeric matrix was achieved by sonicating laboratory-made nano-scale anatase TiO2 and Ag-TiO2 into the industrial grade epoxy resin. The resulting epoxy composite had ratios of 0.5–2.0 wt% of nano-filler content. The process of dispersion of Ag-TiO2 in the epoxy resin resulted in concomitant in situ synthesis of silver nanoparticles due to photoreduction of Ag+ ion. The composite materials were characterized by DSC and SEM. The glass transition temperature (Tg) increased with the incorporation of the nanofillers over the neat polymer. The materials synthesized were coated on glass petri dish. Anti-biofilm property of coated material due to combined release of biocide, and photocatalytic activity under static conditions in petri dish was evaluated against Staphylococcus aureus ATCC6538 and Escherichia coli K-12 under UV irradiation using a crystal violet binding assay. Prepared composite showed significant inhibition of biofilm development in both the organisms. Our studies indicate that the effective dispersion and optimal release of biocidal agents was responsible for anti-biofilm activity of the surface. The reported thermoset coating materials can be used as bactericidal surfaces either in industrial or healthcare settings to reduce the microbial loads. Full article
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