http://www.mdpi.com/journal/coatings Latest open access articles published in Coatings at http://www.mdpi.com/journal/coatings http://www.mdpi.com/2079-6412/3/2/59 The transport behavior of electromagnetic radiation through a polymeric coating or composite is the basis for the material color, appearance, and overall electromagnetic signature. As multifunctional materials become more advanced and next generation in-service applications become more demanding, a need for predictive design of electromagnetic signature is desired. This paper presents various components developed and used in a computational suite for the study and design of electromagnetic radiation transport properties in polymeric coatings and composites. Focus is given to the treatment of the forward or direct scattering problem on surfaces and in bulk matrices of polymeric materials. The suite consists of surface and bulk light scattering simulation modules that may be coupled together to produce a multiscale model for predicting the electromagnetic signature of various material systems. Geometric optics ray tracing is used to predict surface scattering behavior of realistically rough surfaces, while a coupled ray tracing-finite element approach is used to predict bulk scattering behavior of material matrices consisting of microscale and nanoscale fillers, pigments, fibers, air voids, and other inclusions. Extension of the suite to color change and appearance metamerism is addressed, as well as the differences between discrete versus statistical material modeling. Coatings 2013-04-11 3 2 Article 10.3390/coatings3020059 59 81 2079-6412 2013-04-11 doi: 10.3390/coatings3020059 Erik Sapper Brian Hinderliter http://www.mdpi.com/2079-6412/3/1/49 TiO2 thin films were synthesized by sol-gel process: titanium tetraisopropoxide (TTIP) was dissolved in isopropanol, and then hydrolyzed by adding a water/isopropanol mixture with a controlled hydrolysis ratio. The as prepared sol was deposited by “dip-coating” on a glass substrate with a controlled withdrawal speed. The obtained films were annealed at 350 and 500 °C (2 h). The morphological properties of the prepared films were analyzed by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The optical waveguiding properties of TiO2 films were investigated for both annealing temperature using m-lines spectroscopy. The refractive indices and the film thickness were determined from the measured effective indices. The results show that the synthesized planar waveguides are multimodes and demonstrate low propagation losses of 0.5 and 0.8 dB/cm for annealing temperature 350 and 500 °C, respectively. Coatings 2013-03-11 3 1 Article 10.3390/coatings3010049 49 58 2079-6412 2013-03-11 doi: 10.3390/coatings3010049 Tahar Touam Lamia Znaidi Dominique Vrel Iva Ninova-Kuznetsova Ovidiu Brinza Alexis Fischer Azzedine Boudrioua http://www.mdpi.com/2079-6412/3/1/26 Continuous convective-sedimentation assembly (CCSA) is a deposition method that constantly supplies the coating suspension to the meniscus behind the coating knife by inline injection, allowing for steady-state deposition of ordered colloids (which may include particles or cells or live cell-particle blends) by water evaporation. The constant inflow of suspended particles available for transport to the drying front yields colloidal arrays with significantly larger surface areas than previously described and thus expands the ability of convective assembly to deposit monolayers or very thin films of multiple sizes of particles on large surfaces. Using sulfated polystyrene microspheres as a model system, this study shows how tunable process parameters, namely particle concentration, fluid sonication, and fluid density, influence coating homogeneity when the meniscus is continuously supplied. Fluid density and fluid flow-path sonication affect particle sedimentation and distribution. Coating microstructure, analyzed in terms of void space, does not vary significantly with relative humidity or suspended particle concentration. This study evaluated two configurations of the continuous convective assembly method in terms of ability to control coating microstructure by varying the number of suspended polymer particles available for transport to the coating drying front through variations in the meniscus volume. Coatings 2013-02-06 3 1 Article 10.3390/coatings3010026 26 48 2079-6412 2013-02-06 doi: 10.3390/coatings3010026 Jessica Jenkins Michael Flickinger Orlin Velev http://www.mdpi.com/2079-6412/3/1/16 The pencil hardness of a two-component polyurethane coating was improved by adding halloysite nanotubes to the recipe at a weight fraction of less than 10%. The pencil hardness was around F for the unfilled coating and increased to around 2H upon filling. It was important to silanize the surface of the filler in order to achieve good coupling to the matrix. Sonicating the sample during drying also improved the hardness. Scanning electron micrographs suggest that the nanotubes are always well immersed into the bulk of the film. With a thickness between 10 and 20 µm, the optical clarity was good enough to clearly read letters through the film. The films can be used in applications where transparency is required. Coatings 2013-01-18 3 1 Article 10.3390/coatings3010016 16 25 2079-6412 2013-01-18 doi: 10.3390/coatings3010016 Xin Li Irina Nikiforow Katja Pohl Jörg Adams Diethelm Johannsmann http://www.mdpi.com/2079-6412/3/1/1 Metallic biomaterials have been extensively used in orthodontics throughout history. Gold, stainless steel, cobalt-chromium alloys, titanium and its alloys, among other metallic biomaterials, have been part of the orthodontic armamentarium since the twentieth century. Metals and alloys possess outstanding properties and offer numerous possibilities for the fabrication of orthodontic devices such as brackets, wires, bands, ligatures, among others. However, these materials have drawbacks that can present problems for the orthodontist. Poor friction control, allergic reactions, and metal ionic release are some of the most common disadvantages found when using metallic alloys for manufacturing orthodontic appliances. In order to overcome such weaknesses, research has been conducted aiming at different approaches, such as coatings and surface treatments, which have been developed to render these materials more suitable for orthodontic applications. The purpose of this paper is to provide an overview of the coating and surface treatment methods performed on metallic biomaterials used in orthodontics. Coatings 2012-12-27 3 1 Review 10.3390/coatings3010001 1 15 2079-6412 2012-12-27 doi: 10.3390/coatings3010001 Santiago Arango Alejandro Peláez-Vargas Claudia García http://www.mdpi.com/2079-6412/2/4/235 This work surveys the structure, substructure and submicroporosity of Cu metal coatings following condensation both under the conditions of space flight of orbital stations (OS) and under Earth-based conditions. Small-angle X-ray scattering (SAXS) and the method of Ar low-temperature desorption were used for investigation. It has been shown that the condensates deposited in space contain less and relatively equiaxial submicropores (SMPs) distributed more homogeneously than Earth-based disperse films. Coatings 2012-11-20 2 4 Article 10.3390/coatings2040235 235 241 2079-6412 2012-11-20 doi: 10.3390/coatings2040235 Leonid Skatkov Petr Cheremskoy Valeriy Gomozov Boris Bayrachny Gennadiy Tulskiy Svetlana Deribo http://www.mdpi.com/2079-6412/2/4/221 The scratch resistance of coatings used on two highly visible automotive applications (automotive bodies and window glazings) were examined and reviewed. Types of damage (scratch vs. mar), the impact on customers, and the causes of scratch events were investigated. Different exterior clearcoat technologies, including UV curable and self-healing formulations were reviewed, including results from nano- and macro-scratch tests. Polycarbonate hardcoat glazings were tested vs. annealed glass samples using a Taber abraser, with the resulting damage analyzed using transmitted haze measurements and optical profilometry. A correlation between the damage seen in glass samples (many smooth, shallow mars) and the best hardcoat samples (fewer, deeper scratches) and the haze measurements was discussed. Nano-scratch results showed similar fracture forces, but measurably improved mar resistance for the hardcoats/glass system compared to exterior clearcoats. Coatings 2012-11-12 2 4 Review 10.3390/coatings2040221 221 234 2079-6412 2012-11-12 doi: 10.3390/coatings2040221 Christopher Seubert Kenneth Nietering Mark Nichols Rick Wykoff Shannon Bollin http://www.mdpi.com/2079-6412/2/4/210 It has been proposed that a resin coating can serve as a means to protect dental structure after preparation of the tooth for indirect restorations, sealing the exposed dentin. The resin coating is applied on the cut surfaces immediately after tooth preparation and before making an impression by assembling a dentin bonding system and a flowable composite. Resin coatings minimize pulp irritation and improve the bond strength between a resin cement and tooth when bonding the restoration to tooth. Recently, thin-film coating dental materials based on all-in-one adhesive technology were introduced for resin coating of indirect restorations. The thin coating materials are applied in a single clinical step and create a barrier-like film layer on the prepared dentin. The thin coatings play an important role in protecting the dentin from physical, chemical, and biological irritation. In addition, these thin-film coating materials reportedly prevent marginal leakage beneath inlays or crown restorations. In light of the many benefits provided by such a protective layer, these all-in-one adhesive materials may therefore also have the potential to cover exposed root dentin surfaces and prevent caries formation. In this paper, recent progress of the dental coating materials and their clinical applications are reviewed. Coatings 2012-10-01 2 4 Review 10.3390/coatings2040210 210 220 2079-6412 2012-10-01 doi: 10.3390/coatings2040210 Toru Nikaido Rena Takahashi Meu Ariyoshi Alireza Sadr Junji Tagami http://www.mdpi.com/2079-6412/2/3/195 This paper presents nano-impact (low cycle fatigue) behavior of as-deposited amorphous nitinol (TiNi) thin film deposited on Si wafer. The nitinol film was 3.5 µm thick and was deposited by the sputtering process. Nano-impact tests were conducted to comprehend the localized fatigue performance and failure modes of thin film using a calibrated nano-indenter NanoTest™, equipped with standard diamond Berkovich and conical indenter in the load range of 0.5 mN to 100 mN. Each nano-impact test was conducted for a total of 1000 fatigue cycles. Depth sensing approach was adapted to understand the mechanisms of film failure. Based on the depth-time data and surface observations of films using atomic force microscope, it is concluded that the shape of the indenter test probe is critical in inducing the localized indentation stress and film failure. The measurement technique proposed in this paper can be used to optimize the design of nitinol thin films. Coatings 2012-08-31 2 3 Article 10.3390/coatings2030195 195 209 2079-6412 2012-08-31 doi: 10.3390/coatings2030195 Nadimul H. Faisal Rehan Ahmed Richard (Yongqing) Fu http://www.mdpi.com/2079-6412/2/3/179 Dental biomaterials and natural products represent two of the main growing research fields, revealing plant-derived compounds may play a role not only as nutraceuticals in affecting oral health, but also in improving physico-chemical properties of biomaterials used in dentistry. Therefore, our aim was to collect all available data concerning the utilization of plant polysaccharides, proteins and extracts rich in bioactive phytochemicals in enhancing performance of dental biomaterials. Although compelling evidences are suggestive of a great potential of plant products in promoting material-tissue/cell interface, to date, only few authors have investigated their use in development of innovative dental biomaterials. A small number of studies have reported plant extract-based titanium implant coatings and periodontal regenerative materials. To the best of our knowledge, this review is the first to deal with this topic, highlighting a general lack of research findings in an interesting field which still needs to be investigated. Coatings 2012-07-26 2 3 Review 10.3390/coatings2030179 179 194 2079-6412 2012-07-26 doi: 10.3390/coatings2030179 Elena M. Varoni Marcello Iriti Lia Rimondini http://www.mdpi.com/2079-6412/2/3/160 Titanium nitride and/or nitrogen ion implanted coated dental materials have been investigated since the mid-1980s and considered in various applications in dentistry such as implants, abutments, orthodontic wires, endodontic files, periodontal/oral hygiene instruments, and casting alloys for fixed restorations. Multiple methodologies have been employed to create the coatings, but detailed structural analysis of the coatings is generally lacking in the dental literature. Depending on application, the purpose of the coating is to provide increased surface hardness, abrasion/wear resistance, esthetics, and corrosion resistance, lower friction, as well as greater beneficial interaction with adjacent biological and material substrates. While many studies have reported on the achievement of these properties, a consensus is not always clear. Additionally, few studies have been conducted to assess the efficacy of the coatings in a clinical setting. Overall, titanium nitride and/or nitrogen ion implanted coated dental materials potentially offer advantages over uncoated counterparts, but more investigation is needed to document the structure of the coatings and their clinical effectiveness. Coatings 2012-07-26 2 3 Review 10.3390/coatings2030160 160 178 2079-6412 2012-07-26 doi: 10.3390/coatings2030160 Youssef S. Al Jabbari Jennifer Fehrman Ashley C. Barnes Angela M. Zapf Spiros Zinelis David W. Berzins http://www.mdpi.com/2079-6412/2/3/138 Different coatings are used in dentistry in an attempt to prevent caries, improve bonding of restorative materials to tooth tissues, and coat implant surfaces in efforts to speed up osseointegration. These are just a few of the many coating applications used in dentistry. The intention of this review is not to cover the entire field of different coatings used in dentistry, because that topic is just too big to be covered in one single paper. Therefore, this review aims to highlight some fundamental coating principles and present these principles to an audience consisting mainly of dentists. To do so, this review will focus on the fundamental principles of coatings, namely surface properties/adhesives in general, since these topics form the foundation for most coating procedures used in dentistry. Coatings 2012-07-26 2 3 Review 10.3390/coatings2030138 138 159 2079-6412 2012-07-26 doi: 10.3390/coatings2030138 Karl-Johan M. Söderholm http://www.mdpi.com/2079-6412/2/3/120 The aim of this study was to produce a 3D mesh of defect free electrospun cellulose acetate nanofibres and to use this to produce a prototype composite resin containing nanofibre fillers. This might find use as an aesthetic orthodontic bracket material or composite veneer for restorative dentistry. In this laboratory based study cellulose acetate was dissolved in an acetone and dimethylacetamide solvent solution and electrospun. The spinning parameters were optimised and lithium chloride added to the solution to produce a self supporting nanofibre mesh. This mesh was then silane coated and infiltrated with either epoxy resin or an unfilled Bis-GMA resin. The flexural strength of the produced samples was measured and compared to that of unfilled resin samples. Using this method cellulose acetate nanofibres were successfully electrospun in the 286 nm range. However, resin infiltration of this mesh resulted in samples with a flexural strength less than that of the unfilled control samples. Air inclusion during preparation and incomplete wetting of the nanofibre mesh was thought to cause this reduction in flexural strength. Further work is required to reduce the air inclusions before the true effect of resin reinforcement with a 3D mesh of cellulose acetate nanofibres can be determined. Coatings 2012-07-11 2 3 Article 10.3390/coatings2030120 120 137 2079-6412 2012-07-11 doi: 10.3390/coatings2030120 Stephen A. Boyd Bo Su Jonathan R. Sandy Anthony J. Ireland http://www.mdpi.com/2079-6412/2/3/95 The mechanical and biological properties of bone implants need to be optimal to form a quick and firm connection with the surrounding environment in load bearing applications. Bone is a connective tissue composed of an organic collagenous matrix, a fine dispersion of reinforcing inorganic (calcium phosphate) nanocrystals, and bone-forming and -degrading cells. These different components have a synergistic and hierarchical structure that renders bone tissue properties unique in terms of hardness, flexibility and regenerative capacity. Metallic and polymeric materials offer mechanical strength and/or resilience that are required to simulate bone tissue in load-bearing applications in terms of maximum load, bending and fatigue strength. Nevertheless, the interaction between devices and the surrounding tissue at the implant interface is essential for success or failure of implants. In that respect, coatings can be applied to facilitate the process of bone healing and obtain a continuous transition from living tissue to the synthetic implant. Compounds that are inspired by inorganic (e.g., hydroxyapatite crystals) or organic (e.g., collagen, extracellular matrix components, enzymes) components of bone tissue, are the most obvious candidates for application as implant coating to improve the performance of bone implants. This review provides an overview of recent trends and strategies in surface engineering that are currently investigated to improve the biological performance of bone implants in terms of functionality and biological efficacy. Coatings 2012-07-02 2 3 Review 10.3390/coatings2030095 95 119 2079-6412 2012-07-02 doi: 10.3390/coatings2030095 Ruggero Bosco Jeroen Van Den Beucken Sander Leeuwenburgh John Jansen http://www.mdpi.com/2079-6412/2/2/94 The authors wish to make the following correction to this paper: the correct number of the project granted by the Czech Science Foundation is P108/12/1872. [...] Coatings 2012-06-19 2 2 Correction 10.3390/coatings2020094 94 94 2079-6412 2012-06-19 doi: 10.3390/coatings2020094 Pavel Ctibor Zdenek Pala Hanna Boldyryeva Josef Sedláček Viliam Kmetík http://www.mdpi.com/2079-6412/2/2/76 A single splat is the building block of a thermal spray coating; thus, investigating single splats is essential to understanding thermal spray coatings and their properties. In this study, the spreading behavior and the morphology of flame sprayed ethylene methacrylic acid (EMAA) splats, deposited at various stand-off distances (SODs) onto glass and mild steel substrates were investigated using optical microscopy, back scattered scanning electron microscopy and secondary electron scanning electron microscopy. The results of this study indicate that the spread factor increases with an increase in the stand-off distance up to 30 cm for glass and 25 cm for steel substrates. Further increase of the stand-off distance results in a decreased spread factor. The aspect ratio of EMAA single splats on both glass and mild steel substrates decreases with increased stand-off distances, indicating that more circular shapes occur at higher stand-off distances. On mild steel substrates, the minimum unevenness ratio (η) occurs at 35 cm SOD. The unevenness ratio (η) on glass substrates decreases from 1.9 (at 20 cm SOD) to 1.77 (at 25 cm SOD), and from 1.8 (at 30 cm SOD) to 1.3 (at 35 cm SOD). The lowest unevenness ratio (η) is found at 35 cm SOD. The highest unevenness ratio (η) is at 25 cm SOD. This paper discusses the effect of surface chemistry on the underside of an EMAA single splat morphology. It includes Raman spectrum analysis of EMAA and the X-ray diffraction of the EMAA powder. This work analyses the splat morphology and classifies the taxonomy of single splats of EMAA. Coatings 2012-06-15 2 2 Article 10.3390/coatings2020076 76 93 2079-6412 2012-06-15 doi: 10.3390/coatings2020076 Wei Xie James Wang Christopher C. Berndt http://www.mdpi.com/2079-6412/2/2/64 Lead zirconate titanate (PZT) was plasma sprayed onto various substrates of different character. Additionally, a free-standing body made by plasma spraying was investigated. X-ray diffraction analyses of a decomposition of the as-sprayed coating products detected components of the PT-PZ system as well as binary oxides—PbO and ZrO2. Due to the comparatively complex phase character, the Curie temperature monitored by DTA, had a smeared appearance without pronounced maxima. The corresponding electrical properties are comparable with those typically observed for CaTiO3, but are worse than the normal values of bulk PZT due to defective stoichiometry. Coatings 2012-03-28 2 2 Article 10.3390/coatings2020064 64 75 2079-6412 2012-03-28 doi: 10.3390/coatings2020064 Pavel Ctibor Zdenek Pala Hanna Boldyryeva Josef Sedláček Viliam Kmetík http://www.mdpi.com/2079-6412/2/1/45 Polymer clay nanocomposites (NCs) show remarkable potential in the field of drug delivery due to their enhanced barrier properties. It is hypothesised that well dispersed clay particles within the polymer matrix create a tortuous pathway for diffusing therapeutic molecules, thereby resulting in more sustained release of the drug. As coatings for medical devices, these materials can simultaneously modulate drug release and improve the mechanical performance of an existing polymer system without introducing additional materials with new chemistries that can lead to regulatory concerns. In this study, polyurethane organosilicate nanocomposites (PUNCs) coated onto stainless steel wires were evaluated for their feasibility as blood compatible coatings and as drug delivery systems. Heparin was selected as the model drug to examine the impact of silicate loading and modifier chain length in modulating release. Findings revealed that better dispersion was achieved from samples with lower clay loadings and longer alkyl chains. The blood compatibility of PUNCs as assessed by thrombin generation assays showed that the addition of silicate particles did not significantly decrease the thrombin generation lag time (TGT, p = 0.659) or the peak thrombin (p = 0.999) of polyurethane (PU). PUNC coatings fabricated in this research were not cytotoxic as examined by the cell growth inhibition assay and were uniformly intact, but had slightly higher growth inhibition compared to PU possibly due to the presence of organic modifiers (OM). The addition of heparin into PUNCs prolonged the TGT, indicating that heparin was still active after the coating process. Cumulative heparin release profiles showed that the majority of heparin released was from loosely attached residues on the surface of coils. The addition of heparin further prolonged the TGT as compared to coatings without added heparin, but a slight decrease in heparin activity was observed in the NCs. This was thought to be from competitive interactions between clay-heparin that influenced the formation of the ternary complex between heparin, ATIII thrombin. In summary, the feasibility of using PUNC as drug delivery coatings was shown by the good uniformity in the coating, absence of by-products from the coating process, and the release of active molecules without significantly interfering with their activity. Coatings 2012-02-27 2 1 Article 10.3390/coatings2010045 45 63 2079-6412 2012-02-27 doi: 10.3390/coatings2010045 Johnson H. Y. Chung Menno L. W. Knetsch Leo H. Koole Anne Simmons Laura A. Poole-Warren http://www.mdpi.com/2079-6412/2/1/8 A study has been made of permalloy (iron-nickel) contacts of reed switches before and after ion-induced surface modification using atomic force and optical microscopy, Auger electron and X-ray photoelectron spectroscopy. It has been found that the formation of surface nitride layers enhances corrosion and erosion resistance of contacts. We proposed to produce such layers directly into sealed reed switches by means of pulsing glow-discharge nitrogen plasma. Coatings 2012-02-24 2 1 Article 10.3390/coatings2010008 8 44 2079-6412 2012-02-24 doi: 10.3390/coatings2010008 Karen Arushanov Igor Zeltser Sergey Karabanov Rafail Maizels Evgeny Moos Alexander Tolstoguzov http://www.mdpi.com/2079-6412/2/1/1 Electroplated coatings for reed switches were developed and investigated. The optimal compositions of industrial electrolytes currently used in the mass production of reed switches were given. The pros and cons of the different electroplated coatings, including those containing precious metals and with barrier layers of base metal alloys, were discussed. Coatings 2011-12-23 2 1 Article 10.3390/coatings2010001 1 7 2079-6412 2011-12-23 doi: 10.3390/coatings2010001 Lyudmila Shishkina Olga Lokshtanova Sergey Karabanov http://www.mdpi.com/2079-6412/1/2/117 A fundamentally new family of thermal spray processes has emerged. These new processes, collectively known as very low pressure plasma spray or VLPPS, differ from traditional thermal spray processes in that coatings are deposited at unusually low chamber pressures, typically less than ~800 Pa (6 Torr). Depending upon the specific process, deposition may be in the form of very fine molten droplets, vapor phase deposition, or a mixture of vapor and droplet deposition. Resulting coatings are similar in quality to coatings produced by alternative coating technologies, such as physical vapor deposition (PVD) or chemical vapor deposition (CVD), but deposition rates can be roughly an order of magnitude higher with VLPPS. With these new process technologies modified low pressure plasma spray (LPPS) systems can now be used to produce dense, high quality coatings in the 1 to 100 micron thickness range with lamellar or columnar microstructures. A history of pioneering work in VLPPS technology is presented, deposition mechanisms are discussed, potential new applications are reviewed, and challenges for the future are outlined. Coatings 2011-12-20 1 2 Review 10.3390/coatings1020117 117 132 2079-6412 2011-12-20 doi: 10.3390/coatings1020117 Mark F. Smith Aaron C. Hall James D. Fleetwood Philip Meyer http://www.mdpi.com/2079-6412/1/2/108 Porous light-absorbing and thermoregulating low-vacuum aluminum coatings (AC) precipitated by thermal evaporation were the object of this study. The small-angle X-ray scattering (SAXS), electron microscopy, precision hydrostatic weighing, and the dynamical technique for argon low-temperature desorption were used for our investigations. It was shown that AC pore formation in open space (OS) is conditioned by the reduction of molecular flow orienting impact and the increase of the diffusing-vacancy mechanism on coatings formation in zero-gravity conditions, which causes the formation of coarse and equiaxed pores with lowered polydispersity levels. Coatings 2011-12-13 1 2 Communication 10.3390/coatings1020108 108 116 2079-6412 2011-12-13 doi: 10.3390/coatings1020108 Leonid Skatkov Petr Cheremskoy Valeriy Gomozov Boris Bayrachny Gennadiy Tulskiy Svetana Deribo http://www.mdpi.com/2079-6412/1/2/88 Reactive plasma spraying is a promising technology for the in situ formation of aluminum nitride (AlN) coatings. Recently, it became possible to fabricate cubic-AlN-(c-AlN) based coatings through reactive plasma spraying of Al powder in an ambient atmosphere. However, it was difficult to fabricate a coating with high AlN content and suitable thickness due to the coalescence of the Al particles. In this study, the influence of using AlN additive (h-AlN) to increase the AlN content of the coating and improve the reaction process was investigated. The simple mixing of Al and AlN powders was not suitable for fabricating AlN coatings through reactive plasma spraying. However, it was possible to prepare a homogenously mixed, agglomerated and dispersed Al/AlN mixture (which enabled in-flight interaction between the powder and the surrounding plasma) by wet-mixing in a planetary mill. Increasing the AlN content in the mixture prevented coalescence and increased the nitride content gradually. Using 30 to 40 wt% AlN was sufficient to fabricate a thick (more than 200 µm) AlN coating with high hardness (approximately 1000 Hv). The AlN additive prevented the coalescence of Al metal and enhanced post-deposition nitriding through N2 plasma irradiation by allowing the nitriding species in the plasma to impinge on a larger Al surface area. Using AlN as a feedstock additive was found to be a suitable method for fabricating AlN coatings by reactive plasma spraying. Moreover, the fabricated coatings consist of hexagonal (h-AlN), c-AlN (rock-salt and zinc-blend phases) and certain oxides: aluminum oxynitride (Al5O6N), cubic sphalerite Al23O27N5 (ALON) and Al2O3. The zinc-blend c-AlN and ALON phases were attributed to the transformation of the h-AlN feedstock during the reactive plasma spraying. Thus, the zinc-blend c-AlN and ALON phases were not included in the feedstock and were not formed through nitriding of the Al. Coatings 2011-10-03 1 2 Abstract 10.3390/coatings1020088 88 107 2079-6412 2011-10-03 doi: 10.3390/coatings1020088 Mohammed Shahien Motohiro Yamada Toshiaki Yasui Masahiro Fukumoto http://www.mdpi.com/2079-6412/1/1/72 Niobium coatings deposited by magnetron sputtering were evaluated as a possible surface modification for stainless steel (SS) substrates in biomedical implants. The Nb coatings were deposited on 15 mm diameter stainless steel substrates having an average surface roughness of 2 mm. To evaluate the biocompatibility of the coatings three different in vitro tests, using human alveolar bone derived cells, were performed: cellular adhesion, proliferation and viability. Stainless steel substrates and tissue culture plastic were also studied, in order to give comparative information. No toxic response was observed for any of the surfaces, indicating that the Nb coatings act as a biocompatible, bioinert material. Cell morphology was also studied by immune-fluorescence and the results confirmed the healthy state of the cells on the Nb surface. X-ray diffraction analysis of the coating shows that the film is polycrystalline with a body centered cubic structure. The surface composition and corrosion resistance of both the substrate and the Nb coating were also studied by X-ray photoelectron spectroscopy and potentiodynamic tests. Water contact angle measurements showed that the Nb surface is more hydrophobic than the SS substrate. Coatings 2011-09-22 1 1 Article 10.3390/coatings1010072 72 87 2079-6412 2011-09-22 doi: 10.3390/coatings1010072 René Olivares-Navarrete Jhon Jairo Olaya Claudia Ramírez Sandra Elizabeth Rodil http://www.mdpi.com/2079-6412/1/1/53 Hydroxyapatite (HA) coating of hard tissue implants is widely employed for its biocompatible and osteoconductive properties as well as its improved mechanical properties. Plasma technology is the principal deposition process for coating HA on bioactive metals for this application. However, thermal decomposition of HA can occur during the plasma deposition process, resulting in coating variability in terms of purity, uniformity and crystallinity, which can lead to implant failure caused by aseptic loosening. In this study, CoBlastTM, a novel blasting process has been used to successfully modify a titanium (V) substrate with a HA treatment using a dopant/abrasive regime. The impact of a series of apatitic abrasives under the trade name MCD, was investigated to determine the effect of abrasive particle size on the surface properties of both microblast (abrasive only) and CoBlast (HA/abrasive) treatments. The resultant HA treated substrates were compared to substrates treated with abrasive only (microblasted) and an untreated Ti. The HA powder, apatitic abrasives and the treated substrates were characterized for chemical composition, coating coverage, crystallinity and topography including surface roughness. The results show that the surface roughness of the HA blasted modification was affected by the particle size of the apatitic abrasives used. The CoBlast process did not alter the chemistry of the crystalline HA during deposition. Cell proliferation on the HA surface was also assessed, which demonstrated enhanced osteo-viability compared to the microblast and blank Ti. This study demonstrates the ability of the CoBlast process to deposit HA coatings with a range of surface properties onto Ti substrates. The ability of the CoBlast technology to offer diversity in modifying surface topography offers exciting new prospects in tailoring the properties of medical devices for applications ranging from dental to orthopedic settings. Coatings 2011-09-13 1 1 Article 10.3390/coatings1010053 53 71 2079-6412 2011-09-13 doi: 10.3390/coatings1010053 Caroline O’Sullivan Peter O’Hare Greg Byrne Liam O’Neill Katie B. Ryan Abina M. Crean http://www.mdpi.com/2079-6412/1/1/17 In this work High Velocity Oxy-fuel (HVOF) thermal spray techniques, spraying process optimization, and characterization of coatings are reviewed. Different variants of the technology are described and the main differences in spray conditions in terms of particle kinetics and thermal energy are rationalized. Methods and tools for controlling the spray process are presented as well as their use in optimizing the coating process. It will be shown how the differences from the starting powder to the final coating formation affect the coating microstructure and performance. Typical properties of HVOF sprayed coatings and coating performance is described. Also development of testing methods used for the evaluation of coating properties and current status of standardization is presented. Short discussion of typical applications is done. Coatings 2011-09-02 1 1 Article 10.3390/coatings1010017 17 52 2079-6412 2011-09-02 doi: 10.3390/coatings1010017 Maria Oksa Erja Turunen Tomi Suhonen Tommi Varis Simo-Pekka Hannula http://www.mdpi.com/2079-6412/1/1/3 CoNiCrAlY powders with similar granulometry and chemical composition, but different starting reactivity toward oxygen, were sprayed onto superalloy substrates by High Velocity Oxygen-Fuel producing coatings of similar thicknesses. After spraying, samples were maintained at 1,273 K in air for different test periods of up to 5,000 hours. Morphological, microstructural, compositional and electrochemical analyses were performed on the coated samples in order to assess the high temperature oxidation resistance provided by the two different powders. The powder with higher starting reactivity towards oxygen improves the oxidation resistance of the coated samples by producing thinner and more adherent thermally grown oxide layers. Coatings 2010-11-26 1 1 Article 10.3390/coatings1010003 3 16 2079-6412 2010-11-26 doi: 10.3390/coatings1010003 Alessio Fossati Martina Di Ferdinando Alessandro Lavacchi Andrea Scrivani Carlo Giolli Ugo Bardi http://www.mdpi.com/2079-6412/1/1/1 The journal Coatings is starting its activity as a peer-reviewed, open access journal. As editors, we believe that it will fulfill an important role in the community of researchers and developers in the field of coatings. There already exists several high quality journals dedicated to coatings, but none of them has “free access”, a characteristic that we believe is very important in a field which is traditionally very close  to  industrial  activity  and  where  researchers  aim  not  only  at  academic  research  but  toward products  of  an  industrial  and  marketable  value.  For  these  researchers,  it  is  important  that  they  can publish their results in a journal that guarantees quality that comes from peer-review, but that at the same time breaks the traditional boundaries of academic journals which need a subscription or a pay-per-view option to access the published data. [...] Coatings 2010-09-22 1 1 Editorial 10.3390/coatings1010001 1 2 2079-6412 2010-09-22 doi: 10.3390/coatings1010001 Ugo Bardi Alessandro Lavacchi