Open AccessArticle
Oxidation Behavior and Mechanism of Al4SiC4 in MgO-C-Al4SiC4 System
Coatings 2017, 7(7), 85; doi:10.3390/coatings7070085 -
Abstract
Al4SiC4 powder with high purity was synthesized using the powder mixture of aluminum (Al), silicon (Si), and carbon (C) at 1800 °C in argon. Their oxidation behavior and mechanism in a MgO-C-Al4SiC4 system was investigated at 1400–1600
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Al4SiC4 powder with high purity was synthesized using the powder mixture of aluminum (Al), silicon (Si), and carbon (C) at 1800 °C in argon. Their oxidation behavior and mechanism in a MgO-C-Al4SiC4 system was investigated at 1400–1600 °C. XRD, SEM, and energy dispersive spectrometry (EDS) were adopted to analyze the microstructure and phase evolution. The results showed that the composition of oxidation products was closely related to the atom diffusion velocity and the compound oxide layer was generated on Al4SiC4 surface. In addition, the effect of different CO partial pressure on the oxidation of Al4SiC4 crystals was also studied by thermodynamic calculation. This work proves the great potential of Al4SiC4 in improving the MgO-C materials. Full article
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Open AccessArticle
Corrosion Protection of Steel by Epoxy-Organoclay Nanocomposite Coatings
Coatings 2017, 7(7), 84; doi:10.3390/coatings7070084 -
Abstract
The purpose of the present work was to study the corrosion behavior of steel coated with epoxy-(organo) clay nanocomposite films. The investigation was carried out using salt spray exposures, optical and scanning electron microscopy examination, open circuit potential, and electrochemical impedance measurements. The
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The purpose of the present work was to study the corrosion behavior of steel coated with epoxy-(organo) clay nanocomposite films. The investigation was carried out using salt spray exposures, optical and scanning electron microscopy examination, open circuit potential, and electrochemical impedance measurements. The mechanical, thermomechanical, and barrier properties of pristine glassy epoxy polymer and epoxy-clay nanocomposites were examined. The degree of intercalation/exfoliation of clay nanoplatelets within the epoxy polymer also was determined. The mechanical, thermomechanical, and barrier properties of all the epoxy-clay nanocomposites were improved compared to those of the pristine epoxy polymer. In addition, both the pristine epoxy and the epoxy nanocomposite coatings protected the steel from corrosion. Furthermore, the protective properties of the nanocomposite coatings were superior compared to those of the pristine epoxy polymer. The protective properties of the nanocomposite coatings varied with the modified clay used. The epoxy-montmorillonite clay modified with primary octadecylammonium ions, Nanomer I.30E, had a better behavior than that modified with quaternary octadecylammonium ions, Nanomer I.28E. Full article
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Open AccessArticle
Silica-Based Sol-Gel Coating on Magnesium Alloy with Green Inhibitors
Coatings 2017, 7(7), 86; doi:10.3390/coatings7070086 -
Abstract
In this work, the performances of several natural organic inhibitors were investigated in a sol-gel system (applied on the magnesium alloy Mg AZ31B substrate). The inhibitors were quinaldic acid (QDA), betaine (BET), dopamine hydrochloride (DOP), and diazolidinyl urea (DZU). Thin, uniform, and defect-free
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In this work, the performances of several natural organic inhibitors were investigated in a sol-gel system (applied on the magnesium alloy Mg AZ31B substrate). The inhibitors were quinaldic acid (QDA), betaine (BET), dopamine hydrochloride (DOP), and diazolidinyl urea (DZU). Thin, uniform, and defect-free sol-gel coatings were prepared with and without organic inhibitors, and applied on the Mg AZ31B substrate. SEM and EDX were performed to analyze the coating surface properties, the adhesion to the substrate, and the thickness. Electrochemical measurements, including electrochemical impedance spectroscopy (EIS) and anodic potentiodynamic polarization scan (PDS), were performed on the coated samples to characterize the coatings’ protective properties. Also, hydrogen evolution measurement—an easy method to measure magnesium corrosion—was performed in order to characterize the efficiency of coating protection on the magnesium substrate. Moreover, scanning vibrating electrode technique (SVET) measurements were performed to examine the efficiency of the coatings loaded with inhibitors in preventing and containing corrosion events in defect areas. From the testing results it was observed that the formulated sol-gel coatings provided a good barrier to the substrate, affording some protection even without the presence of inhibitors. Finally, when the inhibitors’ performances were compared, the QDA-doped sol-gel was able to contain the corrosion event at the defect. Full article
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Open AccessArticle
Aluminizing via Ionic Liquid Electrodeposition and Pack Cementation: A Comparative Study with Inconel 738 and a CoNiCrAlY
Coatings 2017, 7(6), 83; doi:10.3390/coatings7060083 -
Abstract
A novel aluminizing process based upon room temperature Al-electrodeposition from Ionic Liquids followed by diffusion heat treatment was applied on bare- and CoNiCrAlY-coated Inconel 738 (IN738). The aluminized samples were tested by isothermal oxidation at 1000 °C in air. The microstructural and chemical
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A novel aluminizing process based upon room temperature Al-electrodeposition from Ionic Liquids followed by diffusion heat treatment was applied on bare- and CoNiCrAlY-coated Inconel 738 (IN738). The aluminized samples were tested by isothermal oxidation at 1000 °C in air. The microstructural and chemical evolution of the samples were determined as function of oxidation time and compared with the currently applied coatings obtained via pack cementation. The newly proposed method is suitable for the CoNiCrAlY coating, but not for the bare IN738. In the latter, the formed Al-enriched layer is much thinner and the anticorrosion properties resulted in being reduced. This is probably due to the presence of precipitates, which slow down the aluminum inward diffusion impairing the formation of a well-developed interdiffusion zone (IDZ). Traces of the electrolyte, embedded during the Al-electrodeposition process, can be seen as the origin of these precipitates. Full article
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Open AccessArticle
Maximum Deformation Ratio of Droplets of Water-Based Paint Impact on a Flat Surface
Coatings 2017, 7(6), 81; doi:10.3390/coatings7060081 -
Abstract
In this research, the maximum deformation ratio of water-based paint droplets impacting and spreading onto a flat solid surface was investigated numerically based on the Navier–Stokes equation coupled with the level set method. The effects of droplet size, impact velocity, and equilibrium contact
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In this research, the maximum deformation ratio of water-based paint droplets impacting and spreading onto a flat solid surface was investigated numerically based on the Navier–Stokes equation coupled with the level set method. The effects of droplet size, impact velocity, and equilibrium contact angle are taken into account. The maximum deformation ratio increases as droplet size and impact velocity increase, and can scale as We1/4, where We is the Weber number, for the case of the effect of the droplet size. Finally, the effect of equilibrium contact angle is investigated, and the result shows that spreading radius decreases with the increase in equilibrium contact angle, whereas the height increases. When the dimensionless time t* < 0.3, there is a linear relationship between the dimensionless spreading radius and the dimensionless time to the 1/2 power. For the case of 80° ≤ θe ≤ 120°, where θe is the equilibrium contact angle, the simulation result of the maximum deformation ratio follows the fitting result. The research on the maximum deformation ratio of water-based paint is useful for water-based paint applications in the automobile industry, as well as in the biomedical industry and the real estate industry. Please check all the part in the whole passage that highlighted in blue whether retains meaning before. Full article
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Open AccessReview
Functionalized Textile Based Therapy for the Treatment of Atopic Dermatitis
Coatings 2017, 7(6), 82; doi:10.3390/coatings7060082 -
Abstract
Atopic dermatitis (AD) is a common chronic inflammatory skin condition characterized by intense puritus and skin dryness. The pathogenesis for AD has not been fully understood to date. Complementary therapies are very popular as effective treatment for AD among clinical practitioners. This study
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Atopic dermatitis (AD) is a common chronic inflammatory skin condition characterized by intense puritus and skin dryness. The pathogenesis for AD has not been fully understood to date. Complementary therapies are very popular as effective treatment for AD among clinical practitioners. This study presents a comprehensive review of published works associated with textiles-based complementary therapies for AD treatment such as wet-wrap dressing, functionalized textiles, and the application of hydrogel techniques in the textile industry to provide a better understanding of the development and design of new textiles-based transdermal therapies. Full article
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Open AccessArticle
Development of a TiC/Cr23C6 Composite Coating on a 304 Stainless Steel Substrate through a Tungsten Inert Gas Process
Coatings 2017, 7(6), 80; doi:10.3390/coatings7060080 -
Abstract
The aim of this study was to develop a composite coating on 304 stainless steel employing a TIG (tungsten inert gas) process. Ti wire cored with graphite powder was used as the means of coating material. The process parameters were controlled to develop
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The aim of this study was to develop a composite coating on 304 stainless steel employing a TIG (tungsten inert gas) process. Ti wire cored with graphite powder was used as the means of coating material. The process parameters were controlled to develop a coating with optimum characteristics (i.e., hardness and wear resistance). The microstructure of the coating was analyzed with SEM and XRD. It was found that both the hardness and the wear resistance increase as the current increases, while both of these properties decrease as travelling speed increases. It was found that the coated samples with composite layers were harder than the substrate and can range up to 1100 HV, almost 4.5 times higher than the hardness of 304 stainless steel. Likewise, the wear resistance of the coating was observed to be 4.5 times higher than that of the substrate. The high performance of the coating, as revealed by microstructural analysis, was due to the formation of TiC and Cr23C6.The optimum conditions for producing the coating are thus proposed to include a 120 A current and a 3.17 mm/s travel speed. Full article
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Open AccessArticle
Nitrogen Trapping Ability of Hydrogen-Induced Vacancy and the Effect on the Formation of AlN in Aluminum
Coatings 2017, 7(6), 79; doi:10.3390/coatings7060079 -
Abstract
This paper presents the ternary interaction of N, H, and vacancy point defects and the nitrogen trapping ability of aluminum vacancies induced by hydrogen by means of DFT methods employed in VASP (Vienna Ab initio Simulation Package) and Abinit packages. The obtained vacancy
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This paper presents the ternary interaction of N, H, and vacancy point defects and the nitrogen trapping ability of aluminum vacancies induced by hydrogen by means of DFT methods employed in VASP (Vienna Ab initio Simulation Package) and Abinit packages. The obtained vacancy formation energy of 0.65 eV is close to experimental values. Although the N–vacancy complex is unstable with the negative binding energy of −0.51 eV, the stability of H–vacancy–N is proved by the positive binding energy of 0.59 eV and the appearance of the orbital hybridization in the density of state (DOS) of atoms connecting to this complex. Moreover, Al vacancies can trap more than 4 N atoms, which prevents the formation of aluminum nitride and subsequently affects not only the hardness of the Al surface but also many practical applications of AlN coating. Full article
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Open AccessLetter
Mn-Promoted Growth and Photoluminescence of Molybdenum Disulphide Monolayer
Coatings 2017, 7(6), 78; doi:10.3390/coatings7060078 -
Abstract
Molybdenum disulphide (MoS2) monolayer is a two-dimensional semiconductor material with potential applications in nano electronic devices. However, it is still a challenge to reproducibly synthesize single layer MoS2 in high quality. Herein, we report the growth of monolayer of MoS
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Molybdenum disulphide (MoS2) monolayer is a two-dimensional semiconductor material with potential applications in nano electronic devices. However, it is still a challenge to reproducibly synthesize single layer MoS2 in high quality. Herein, we report the growth of monolayer of MoS2 on the SiO2/Si substrate with manganese heterogeneous nucleation. It was shown that the Mn promotes the growth of monolayer MoS2 via heterogeneous nucleation. The growth temperature range expanded two-fold, the nucleation density increased as well. The monolayer prepared in the presence of Mn exhibits a unique red emission peak at 732 nm at room temperature compared to the sample in the absence of Mn. Full article
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Open AccessArticle
Optimization of the Laser Hardening Process by Adapting the Intensity Distribution to Generate a Top-hat Temperature Distribution Using Freeform Optics
Coatings 2017, 7(6), 77; doi:10.3390/coatings7060077 -
Abstract
Laser hardening is a surface hardening process which enables high quality results due to the controllability of the energy input. The hardened area is determined by the heat distribution caused by the intensity profile of the laser beam. However, commonly used top-hat laser
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Laser hardening is a surface hardening process which enables high quality results due to the controllability of the energy input. The hardened area is determined by the heat distribution caused by the intensity profile of the laser beam. However, commonly used top-hat laser beams do not provide an ideal temperature profile. Therefore, in this paper the beam profile, and thus the temperature profile, is optimized using freeform optics. The intensity distribution is modified to generate a top-hat temperature profile on the surface. The results of laser hardening with the optimized distribution are thereupon compared with results using a top-hat intensity distribution. Full article
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Open AccessArticle
Alternative Fillers for the Production of Bituminous Mixtures: A Screening Investigation on Waste Powders
Coatings 2017, 7(6), 76; doi:10.3390/coatings7060076 -
Abstract
There has been a significant increase in the demand for using recycled materials in construction because of the lack and limitation of available natural resources. A number of industrial and domestic waste products are being used in the replacement of traditional materials for
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There has been a significant increase in the demand for using recycled materials in construction because of the lack and limitation of available natural resources. A number of industrial and domestic waste products are being used in the replacement of traditional materials for road construction, and many studies have been carried out in recent years on the use of different recycled materials in substitution of conventional fillers in Asphalt Concretes (AC). The aim of this laboratory research is to analyze the physical characteristics of three different recycled fillers and compare them with those of a traditional limestone filler. The alternative fillers presented in this paper are: a waste bleaching clay that comes from two consecutive stages in the industrial process for decolouring vegetable oils and producing biogas (Ud filler), a dried mud waste from a tungsten mine (MW filler) and a recycled glass powder (Gl filler). Results show significant differences between the fillers, and, in particular, Rigden Voids (RV) seem to have the largest potential influence on the rheology of ACs. Full article
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Open AccessArticle
Surface Erosion of Low-Current Reed Switches
Coatings 2017, 7(6), 75; doi:10.3390/coatings7060075 -
Abstract
The erosion model of the surface coatings of reed switches considering different physicochemical processes occurring on the contact surfaces and inside the inter-electrode gap was proposed. According to that, the discrete electron avalanche (ecton) introduced in the explosive electron emission theory
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The erosion model of the surface coatings of reed switches considering different physicochemical processes occurring on the contact surfaces and inside the inter-electrode gap was proposed. According to that, the discrete electron avalanche (ecton) introduced in the explosive electron emission theory by Mesyats is considered as the main motive force responsible for the surface modification and mass transfer of materials in the course of breaking/shorting of the contacts. By means of SEM imaging and energy dispersive X-ray microanalysis of the contact surfaces after various numbers of switching cycles, the energy threshold of the ecton generation defining the erosion stability of the coatings was found to be proportional to the specific sublimation and ionization energies of coating materials. It has been shown that the total erosion of the coatings on the working surface of the contacts after the commutation test possess the resultant character; i.e., the specificities of erosion occurring after each commutation event are characteristic for the whole of the commutation test. In further development of our model, we suggested that a few monolayers of metals (or alloys) with low ionization potential deposited on the main coatings can improve the erosion stability of contacts. Full article
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Open AccessArticle
Fabrication of Luminescent Antireflective Coatings with CaMoO4:Eu3+/Ag Composite Structure
Coatings 2017, 7(6), 74; doi:10.3390/coatings7060074 -
Abstract
Highly transparent and luminescent CaMoO4:Eu3+/Ag composite films were fabricated on glass substrates as multifunctional antireflective (AR) coatings. The films were deposited through a combination of a sol–gel dip-coating technique and a hot water treatment. With the addition of an
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Highly transparent and luminescent CaMoO4:Eu3+/Ag composite films were fabricated on glass substrates as multifunctional antireflective (AR) coatings. The films were deposited through a combination of a sol–gel dip-coating technique and a hot water treatment. With the addition of an aluminum source in coating solutions, the sol–gel-derived films underwent a remarkable microstructural change during the hot water treatment due to the reaction between an amorphous alumina phase and water. This change brought both an antireflective effect (suppression of Fresnel reflection) and luminescence enhancement (suppression of total internal reflection) to the films. The introduction of Ag nanoparticles into the films further increased luminescence intensity without losing the antireflective effect. Full article
Open AccessArticle
Combustion Synthesis of UHTC Composites from Ti–B4C Solid State Reaction with Addition of VIb Transition Metals
Coatings 2017, 7(6), 73; doi:10.3390/coatings7060073 -
Abstract
UHTC composites were prepared by self-propagating high-temperature synthesis (SHS) from the Ti–B4C reaction system with addition of Cr, Mo, and W. The starting sample composition was formulated as (3−x)Ti + B4C + xMe with x =
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UHTC composites were prepared by self-propagating high-temperature synthesis (SHS) from the Ti–B4C reaction system with addition of Cr, Mo, and W. The starting sample composition was formulated as (3−x)Ti + B4C + xMe with x = 0.1–1.0 and Me = Cr, Mo, or W. For all samples conducted in this study, self-sustaining combustion was well established and propagated with a distinct reaction front. With no addition of Cr, Mo, or W, solid state combustion of the 3Ti + B4C sample featuring a combustion front temperature (Tc) of 1766 °C and a combustion wave velocity (Vf) of 16.5 mm/s was highly exothermic and produced an in situ composite of 2TiB2 + TiC. When Cr, Mo, or W was adopted to replace a portion of Ti, the reaction exothermicity was lowered, and hence, a significant decrease in Tc (from 1720 to 1390 °C) and Vf (from 16.1 to 3.9 mm/s) was observed. With addition of Cr, Mo, and W, the final products were CrB-, MoB-, and WB-added TiB2–TiC composites. The absence of CrB2, MoB2, and WB2 was attributed partly to the loss of boron from thermal decomposition of B4C and partly to lack of sufficient reaction time inherent to the SHS process. Full article
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Open AccessArticle
Ammonia Generation via a Graphene-Coated Nickel Catalyst
Coatings 2017, 7(6), 72; doi:10.3390/coatings7060072 -
Abstract
A novel graphene-coated Ni electrode was developed in this investigation to improve corrosion resistance while unexpectedly enhancing the ammonia generation rate in the electrochemically induced urea to ammonia (eU2A) process, which is an electrochemical onsite ammonia generation method. The development of the electrode
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A novel graphene-coated Ni electrode was developed in this investigation to improve corrosion resistance while unexpectedly enhancing the ammonia generation rate in the electrochemically induced urea to ammonia (eU2A) process, which is an electrochemical onsite ammonia generation method. The development of the electrode is crucial for the eU2A reactions since in the ammonia generation process, the concentration of ammonia is inevitably high on the surface of the electrode, leading to severe corrosion of the electrode and the loss of generated ammonia as well. In this paper, the graphene was derived from raw coal by using the chemical vapor deposition method and self-lifted onto a Ni electrode to form a protective layer for corrosion prevention. Transmission electron microscopy showed the synthesized graphene had few-layers and Raman spectroscopy indicated that the coating of graphene was stable during the eU2A reaction. As a result, the ammonia corrosion of the Ni electrode was dramatically reduced by ~20 times with the graphene coating method. More importantly, a higher ammonia generation rate (~2 times) was achieved using the graphene-coated Ni working electrode compared to a bare Ni electrode in the eU2A process. Full article
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Open AccessArticle
Predicting the Wear of High Friction Surfacing Aggregate
Coatings 2017, 7(5), 71; doi:10.3390/coatings7050071 -
Abstract
High friction surfacing (HFS) is a specialist type of road coating with very high skid resistance. It is used in the UK at locations where there is significant risk of serious or fatal accidents. This paper considers the aggregate used in HFS. Calcined
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High friction surfacing (HFS) is a specialist type of road coating with very high skid resistance. It is used in the UK at locations where there is significant risk of serious or fatal accidents. This paper considers the aggregate used in HFS. Calcined bauxite is the only aggregate that provides the highest levels of skid resistance over the longest period. No naturally occurring aggregate has been found to give a comparable level of in-service performance. This paper reviews the historical development of HFS in the UK relating to aggregate. In-service performance is predicted in the laboratory using the Wear test which subjects test specimens to an estimated 5–8 years simulated trafficking. Examples are given of Wear test data. They illustrate why calcined bauxite performs better than natural aggregate. They show how the amount of calcined bauxite can be reduced by blending with high skid resistant natural aggregates. Data from the Wear test can be related to every HFS laboratory experiment and road trial carried out in the UK for over the last 50 years. Anyone considering the prediction of HFS performance needs to carefully consider the data given in this paper with any other test method currently being considered or used to investigate HFS. Full article
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Open AccessArticle
A New Finite Element Formulation for Nonlinear Vibration Analysis of the Hard-Coating Cylindrical Shell
Coatings 2017, 7(5), 70; doi:10.3390/coatings7050070 -
Abstract
In this paper, a four-node composite cylindrical shell finite element model based on Love’s first approximation theory is proposed to solve the nonlinear vibration of the hard-coating cylindrical shell efficiently. The developed model may have great significance for vibration reduction of the cylindrical
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In this paper, a four-node composite cylindrical shell finite element model based on Love’s first approximation theory is proposed to solve the nonlinear vibration of the hard-coating cylindrical shell efficiently. The developed model may have great significance for vibration reduction of the cylindrical shell structures of the aero engine or aircraft. The influence of the strain dependence of the coating material on the complex stiffness matrix is considered in this model. Nonlinear iterative solution formulas with a unified iterative method are theoretically derived for solving the resonant frequency and response of the composite cylindrical shell. Then, a cylindrical shell coated with a thin layer of NiCoCrAlY + yttria-stabilized zirconia (YSZ) is chosen to demonstrate the proposed formulation, and the rationality is validated by comparing with the finite element iteration method (FEIM). Results show that the developed finite element method is more efficient, and the hard-coating cylindrical shell has the characteristics of soft nonlinearity due to the strain dependence of the coating material. Full article
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Open AccessArticle
Influence of Heating Conditions for Formation of a Thin Apatite Film on Zirconia Using a Molecular Precursor Method
Coatings 2017, 7(5), 69; doi:10.3390/coatings7050069 -
Abstract
The influence of heating conditions, heating temperature, and heating time on the formation of a thin carbonate-containing hydroxyapatite (CA) film onto partially stabilized zirconia using a molecular precursor method was evaluated. The molecular precursor solution was prepared from a mixture of calcium-ethylenediaminetetraacetic acid
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The influence of heating conditions, heating temperature, and heating time on the formation of a thin carbonate-containing hydroxyapatite (CA) film onto partially stabilized zirconia using a molecular precursor method was evaluated. The molecular precursor solution was prepared from a mixture of calcium-ethylenediaminetetraacetic acid complex and phosphate compounds at Ca/P ratio of 1.67. After the application of molecular precursor solution onto zirconia, four different heating conditions—namely, 600 °C-2 h, 800 °C-2 h, 1000 °C-2 h, and 600 °C-4 h—were applied. No distinct difference of surface appearance of CA coating was observed between 600 and 800 °C-2 h. Fusion of apatite crystals was observed at 1000 °C-2 h. Surface roughness of CA film at 1000 °C-2 h was significantly higher than those under other heating conditions. Heating at 800 °C produced a significantly more hydrophilic surface and higher degree of crystallization. No significant differences were recognized in the critical load at the first crack in the coating among the four samples by scratch tests. After 30 days’ immersion in phosphate buffered saline, the four different CA coating films were still present. Simulated body fluid immersion experiments were performed as in vitro biocompatibility tests. After 48 h immersion, the CA film at 800 °C-2 h showed a greater amount of spherical crystal precipitation. It was suggested that properties of CA coating on partially stabilized zirconia using a molecular precursor method were influenced by the heating temperature and time. Full article
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Open AccessArticle
Stiffness of Plasma Sprayed Thermal Barrier Coatings
Coatings 2017, 7(5), 68; doi:10.3390/coatings7050068 -
Abstract
Thermal spray coatings (TSCs) have complex microstructures and they often operate in demanding environments. Plasma sprayed (PS) thermal barrier coating (TBC) is one such ceramic layer that is applied onto metallic components where a low macroscopic stiffness favors stability by limiting the stresses
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Thermal spray coatings (TSCs) have complex microstructures and they often operate in demanding environments. Plasma sprayed (PS) thermal barrier coating (TBC) is one such ceramic layer that is applied onto metallic components where a low macroscopic stiffness favors stability by limiting the stresses from differential thermal contraction. In this paper, the Young’s modulus of TBC top coat, measured using different techniques, such as four-point bending, indentation and impulse excitation is reported, along with a brief description of how the techniques probe different length scales. Zirconia-based TBC top coats were found to have a much lower global stiffness than that of dense zirconia. A typical value for the as-sprayed Young’s modulus was ~23 GPa, determined by beam bending. Indentation, probing a local area, gave significantly higher values. The difference between the two stiffness values is thought to explain the wide range of TBC top coat Young’s modulus values reported in the literature. On exposure to high temperature, due to the sintering process, detached top coats exhibit an increase in stiffness. This increase in stiffness caused by the sintering of fine-scale porosity has significant impact on the strain tolerance of the TBC. The paper discusses the different techniques for measuring the Young’s modulus of the TBC top coats and implications of the measured values. Full article
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Open AccessArticle
Characterization of the Anti-Graffiti Properties of Powder Organic Coatings Applied in Train Field
Coatings 2017, 7(5), 67; doi:10.3390/coatings7050067 -
Abstract
The widespread prevalence of the phenomenon of graffiti and the growth of the removal cost—in particular in public transport systems—has pushed the research for technical solutions to this problem. Suitable solutions to address graffiti-related concerns are needed in order to reduce the cleaning
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The widespread prevalence of the phenomenon of graffiti and the growth of the removal cost—in particular in public transport systems—has pushed the research for technical solutions to this problem. Suitable solutions to address graffiti-related concerns are needed in order to reduce the cleaning costs as well as the downtime of trains. Graffiti are a big problem for painted metal, because the protective coatings and graffiti have the same chemical nature (polymeric matter). A permanent coating is expected to be able to resist the highest possible number of cleanings of the graffiti without modifying its aesthetic and corrosion protection properties. The purpose of this study is to develop a methodological approach for the characterization of graffiti-resistant organic coatings. For this purpose, a critical review of the existing standards is carried out. The anti-graffiti properties of a polyurethane organic coating were investigated before and after accelerated weathering. In order to understand the behavior of the coatings during cleaning, the aging of the coating in contact with the remover was carried out. The effect on the corrosion protection properties was assessed during the accelerated aging. The resistance of the coating was proved to be strongly affected by the surface finishing. UV exposure modified surface properties and graffiti removal efficiency. Full article
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