Coatings

3 pages, 167 KiB

Open AccessEditorial

Special Issue “Wood Modification: Characterization, Modelling, and Applications”

by Anna Sandak and Jakub Sandak

Coatings 2021, 11(7), 869; https://doi.org/10.3390/coatings11070869 - 20 Jul 2021

Cited by 1 | Viewed by 1707

Wood has been recognized as an attractive alternative to several other traditional construction solutions, and it is often called the “building material of the 21st century” [...] Full article

(This article belongs to the Special Issue Wood Modification: Characterization, Modelling and Applications)

12 pages, 6800 KiB

Open AccessArticle

Thermal Cycling Behavior of Air Plasma-Sprayed and Low-Pressure Plasma-Sprayed Environmental Barrier Coatings

by Dianying Chen, Aaron Pegler, Gopal Dwivedi, Daniel De Wet and Mitchell Dorfman

Coatings 2021, 11(7), 868; https://doi.org/10.3390/coatings11070868 - 20 Jul 2021

Cited by 15 | Viewed by 3386

Abstract

Yb₂Si₂O₇/Si environmental barrier coatings (EBCs) were produced by air plasma spray (APS) and low-pressure plasma spray (LPPS) processes. The phase composition, microstructure, and bonding strength of APS and LPPS EBCs were investigated. Thermal cycling tests were performed [...] Read more.

Yb₂Si₂O₇/Si environmental barrier coatings (EBCs) were produced by air plasma spray (APS) and low-pressure plasma spray (LPPS) processes. The phase composition, microstructure, and bonding strength of APS and LPPS EBCs were investigated. Thermal cycling tests were performed in air and in steam atmosphere respectively at 1316 °C for both APS and LPPS EBCs. There is no coating failure in air atmosphere for both APS and LPPS EBCs after 900 cycles. In contrast, APS EBCs have an average life of 576 cycles in a steam cycling test in 90% H₂O + 10% air at 1316 °C while LPPS EBCs survived 1000 cycles without failure. The superior durability of the LPPS EBCs compared to APS EBCs in the same steam cycling environment is attributed to the significantly reduced thermally grown oxide (TGO) growth rate because of the denser and crack-free microstructure, higher bonding strength, and reduced coefficient of thermal expansion (CTE) mismatch (less Yb₂SiO₅ phase) in the LPPS Yb₂Si₂O₇/Si EBCs. Full article

(This article belongs to the Special Issue Coatings for Extreme Environments)

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12 pages, 4115 KiB

Open AccessArticle

TiN/NbN Nanoscale Multilayer Coatings Deposited by High Power Impulse Magnetron Sputtering to Protect Medical-Grade CoCrMo Alloys

by Arunprabhu Arunachalam Sugumaran, Yashodhan Purandare, Krishnanand Shukla, Imran Khan, Arutiun Ehiasarian and Papken Hovsepian

Coatings 2021, 11(7), 867; https://doi.org/10.3390/coatings11070867 - 20 Jul 2021

Cited by 7 | Viewed by 3076

Abstract

This study describes the performance of nanoscale multilayer TiN/NbN coatings deposited on CoCrMo medical-grade alloys by utilising novel mixed high power impulse magnetron sputtering (HIPIMS) and direct current unbalanced magnetron sputtering (UBM) technique in an industrial size vacuum coater. Scanning electron microscopy analysis [...] Read more.

This study describes the performance of nanoscale multilayer TiN/NbN coatings deposited on CoCrMo medical-grade alloys by utilising novel mixed high power impulse magnetron sputtering (HIPIMS) and direct current unbalanced magnetron sputtering (UBM) technique in an industrial size vacuum coater. Scanning electron microscopy analysis showed that these coatings were extremely dense without any intercolumnar voids. The coating exhibited high hardness of 28 GPa, as well as low friction and wear coefficient of 0.7 and 1.4 × 10⁻¹⁴ m³·N⁻¹·m⁻¹, respectively, as compared to the bare material. Scratch tests revealed superior coating to substrate adhesion due to the HIPIMS etching prior to coating deposition. Energy-dispersive X-ray analysis of the wear debris generated during the impact test together with focused ion beam cross-section analysis in different locations of the impact crater revealed the coating failure mechanism and further confirmed the excellent coating to substrate bonding strength. Potentiodynamic polarisation tests in NaCl and Hank’s solutions revealed the clear passivation behaviour, several orders of magnitude lower corrosion currents, and high pitting potentials of the coating, which guarantee excellent protection to the base alloy in such aggressive environments. Inductively coupled plasma mass spectrometry analysis of Hank’s solution containing corrosion debris of the coated sample revealed that the leaching of harmful metal ions from the base material was reduced to below the detection limit of the technique, thus demonstrating the high barrier properties of the coating. Full article

(This article belongs to the Special Issue Hard Coatings for Surface Engineering Solutions)

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8 pages, 1241 KiB

Open AccessCommunication

Atmospheric-Pressure Air Plasma Jet and Its Striation Discharge Mode for Treatment of Thermally Sensitive Materials

by Yong-Cheol Hong

Coatings 2021, 11(7), 866; https://doi.org/10.3390/coatings11070866 - 20 Jul 2021

Cited by 2 | Viewed by 3241

Abstract

A hollow inner electrode covered with a dielectric tube was inserted into an outer electrode and airflow was fed through the inner electrode. The electrodes were then connected to a transformer operated at an alternating voltage with sinusoidal waveform at a frequency of [...] Read more.

A hollow inner electrode covered with a dielectric tube was inserted into an outer electrode and airflow was fed through the inner electrode. The electrodes were then connected to a transformer operated at an alternating voltage with sinusoidal waveform at a frequency of 20 kHz. The resulting discharge is ejected out of the outer electrode from a 0.7 mm hole in the form of a plasma jet into ambient air. The attributes of the discharged plasma jet were evaluated by monitoring the voltage and current behavior and by investigating the optical emissions. The discharge patterns in the atmospheric-pressure air plasma jet in the form of striations could be observed by the naked eye. Furthermore, we reported the striation mechanism by ion acoustic wave propagation by utilizing a simple calculation. Full article

(This article belongs to the Special Issue Surface Modification by Plasma-Based Processes)

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15 pages, 443 KiB

Open AccessReview

Factors Influencing Marginal Bone Loss around Dental Implants: A Narrative Review

by Jakub Kowalski, Barbara Lapinska, Joseph Nissan and Monika Lukomska-Szymanska

Coatings 2021, 11(7), 865; https://doi.org/10.3390/coatings11070865 - 19 Jul 2021

Cited by 22 | Viewed by 7774

Abstract

Implant supported dental prostheses are increasingly used in dental practice. The aim of this narrative review is to present the influence of transmucosal surface of prosthetic abutment and implant on peri-implant tissue. The article describes causes of bone loss around the dental implant. [...] Read more.

Implant supported dental prostheses are increasingly used in dental practice. The aim of this narrative review is to present the influence of transmucosal surface of prosthetic abutment and implant on peri-implant tissue. The article describes causes of bone loss around the dental implant. Moreover, properties of different materials are compared and discussed. The advantages, disadvantages, and biomechanical concept of different implant-abutment connections are presented. The location of connections in relation to the bone level and the influence of microgap between the abutment and implant are described. Additionally, the implant abutments for cemented and screwed prosthetic restorations are compared. The influence of implant and abutment surface at the transmucosal level on peri-implant soft tissue is discussed. Finally, the biological aspect of abutment-implant connection is analyzed. Full article

(This article belongs to the Special Issue Surface Properties of Dental Materials and Instruments)

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13 pages, 10540 KiB

Open AccessArticle

Structural, Optical, and Electrical Properties of Copper Oxide Films Grown by the SILAR Method with Post-Annealing

by Wen-Jen Lee and Xin-Jin Wang

Coatings 2021, 11(7), 864; https://doi.org/10.3390/coatings11070864 - 19 Jul 2021

Cited by 29 | Viewed by 3695

Abstract

Copper oxides are widely used in photocatalysts, sensors, batteries, optoelectronic, and electronic devices. In order to obtain different material properties to meet the requirements of different application fields, varied technologies and process conditions are used to prepare copper oxides. In this work, copper [...] Read more.

Copper oxides are widely used in photocatalysts, sensors, batteries, optoelectronic, and electronic devices. In order to obtain different material properties to meet the requirements of different application fields, varied technologies and process conditions are used to prepare copper oxides. In this work, copper oxide films were grown on glass substrates by a successive ionic layer adsorption and reaction (SILAR) method with subsequent annealing under an atmospheric environment. The films were characterized by using an X-ray diffractometer, Raman spectrometer, Scanning electron microscope, UV-Visible-NIR spectrophotometer, and Hall Effect measurement. The results show that the as-deposited film has a Cu₂O crystal structure, which begins to transform into Cu₂O-CuO mixed crystal and CuO crystal structure after annealing at 300 °C for a period of time, resulting in the bandgap of being reduced from 1.90 to 1.34 eV. The results show that not only are the crystal structure and bandgap of the films affected by the post-annealing temperature and time, but also the resistivity, carrier concentration, and mobility of the films are varied with the annealing conditions. In addition, the film with a Cu₂O-CuO mixed crystal shows a high carrier mobility of 93.7 cm²·V⁻¹·s⁻¹ and a low carrier concentration of 1.8 × 10¹² cm⁻³ due to the formation of a Cu₂O-CuO heterojuction. Full article

(This article belongs to the Special Issue Multilayer and Functional Graded Coatings)

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15 pages, 4359 KiB

Open AccessArticle

Optimization of the Active Layer P3HT:PCBM for Organic Solar Cell

by Mohamed Shaban, Mohamed Benghanem, Abdullah Almohammedi and Mohamed Rabia

Coatings 2021, 11(7), 863; https://doi.org/10.3390/coatings11070863 - 19 Jul 2021

Cited by 27 | Viewed by 5188

Abstract

ITO/PEDOT:PSS/P3HT:PC₆₀BM/Mg-Al organic solar cells (OSCs) were fabricated depending on optimization of Poly(3-hexylthiophene-2,5-diyl) (P3HT) and phenyl-C61-Butyric-Acid-Methyl Ester (PC₆₀BM). The optimization of the active layer, P3HT:PC₆₀BM, was carried out under different spin frequencies coating from 900 to 3000 rpm. [...] Read more.

ITO/PEDOT:PSS/P3HT:PC₆₀BM/Mg-Al organic solar cells (OSCs) were fabricated depending on optimization of Poly(3-hexylthiophene-2,5-diyl) (P3HT) and phenyl-C61-Butyric-Acid-Methyl Ester (PC₆₀BM). The optimization of the active layer, P3HT:PC₆₀BM, was carried out under different spin frequencies coating from 900 to 3000 rpm. The post-production annealing temperature of all prepared OSC was studied from 130 to 190 °C. The holes transport layer, poly(3,4-ethylene dioxythiophene) polystyrene sulfonate (PEDOT:PSS), was prepared under constant conditions of 3000 rpm for 35 s, and annealing temperature 178 °C for 15 min. From our study, the optimum conditions for P3HT:PC₆₀BM were spin coating of 3000 rpm, and annealing temperature of 160 °C for 5 min. The optimum J-V parameters values for the prepared OSC were J_SC = 12.01 mA/cm², V_OC = 660 mV, FF = 59%, PCE = 4.65%, and EQE = 61%. A complete OSC with acceptable efficiency was designed using simple and low-cost techniques that may be utilized in the industry. Furthermore, the cost of the synthesized solar cell is projected to be around 1 $/cm², with the goal of lowering the cost and increasing efficiency in the future by incorporating more commercial nanostructured electron/hole transport components. Full article

(This article belongs to the Special Issue Optical Thin Films: Preparation, Application and Development)

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14 pages, 1611 KiB

Open AccessArticle

Effect of Selenium Nanoparticles on Germination of Hordéum Vulgáre Barley Seeds

by Shahida Anusha Siddiqui, Andrey Vladimirovich Blinov, Alexander Vladimirovich Serov, Alexey Alekseevich Gvozdenko, Alexander Aleksandrovich Kravtsov, Andrey Ashotovich Nagdalian, Vladislav Viktorovich Raffa, David Guramievich Maglakelidze, Anastasiya Alexandrovna Blinova, Anna Vitalievna Kobina, Alexey Borisovich Golik and Salam A. Ibrahim

Coatings 2021, 11(7), 862; https://doi.org/10.3390/coatings11070862 - 19 Jul 2021

Cited by 47 | Viewed by 5629

Abstract

Within the framework of this study, the effect of nanoparticles of the essential trace element selenium stabilized by Polyvinylpirrolidone (PVP) C15 (8 ± 2 kDa) and ascorbic acid on the germination of barley seeds has been studied. Selenium nanoparticles stabilized by PVP C15 [...] Read more.

Within the framework of this study, the effect of nanoparticles of the essential trace element selenium stabilized by Polyvinylpirrolidone (PVP) C15 (8 ± 2 kDa) and ascorbic acid on the germination of barley seeds has been studied. Selenium nanoparticles stabilized by PVP C15 (8 ± 2 kDa) and ascorbic acid, characterized by a spherical shape, monodisperse size distribution, and a diameter of about 70 ± 5 nm, were obtained by the chemical reduction method. The experiment compared the effect of selenium nanoparticles and selenous acid on seed germination. The positive effect of preparation of selenium nanoparticles stabilized by PVP C15 (8 ± 2 kDa) and ascorbic acid on the length of roots and shoots, the number of roots, and the percentage of seed germination has been revealed. It was determined that the highest percentage of Hordeum vulgare L. culture seed germination was achieved using a preparation of selenium nanoparticles stabilized by PVP C15 (8 ± 2 kDa) and ascorbic acid at a concentration of of 4.65 µg/mL. Analysis of the results showed that selenium in the form of nanoparticles has an order of magnitude that is less toxic than in the form of selenous acid. The study of morphological and functional parameters during the germination of Hordeum vulgare L. seeds allowed us to conclude that selenium nanoparticles can be successfully used in agronomy and agriculture to provide plants with the essential microelement selenium, which is necessary for the normal growth and development of crops. Full article

(This article belongs to the Collection Advanced Surface Coating of Nanoparticles)

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8 pages, 2091 KiB

Open AccessArticle

Mechanistic Study on Gold-Like Luster Development of Solution-Cast Oligo(3-methoxythiophene) Film

by Minako Kubo, Minako Tachiki, Terumasa Mitogawa, Kota Saito, Ryota Saito, Satoru Tsukada, Takahiko Horiuchi and Katsuyoshi Hoshino

Coatings 2021, 11(7), 861; https://doi.org/10.3390/coatings11070861 - 18 Jul 2021

Cited by 3 | Viewed by 1818

Abstract

Solution-cast coating films of perchlorate-doped oligo(3-methoxythiophene) exhibited a gold-like luster similar to that of metallic gold despite the involvement of no metals. However, the development mechanism of the luster remains ambiguous. To understand the mechanism, we performed scanning electron microscopic analysis, variable-angle spectral [...] Read more.

Solution-cast coating films of perchlorate-doped oligo(3-methoxythiophene) exhibited a gold-like luster similar to that of metallic gold despite the involvement of no metals. However, the development mechanism of the luster remains ambiguous. To understand the mechanism, we performed scanning electron microscopic analysis, variable-angle spectral reflectance measurements, and ellipsometry measurements on ClO₄⁻-doped oligo(3-methoxythiophene) cast film with a gold-like luster. The results revealed that the lustrous color of the film was not induced by the submicron-sized regular structures (structural color), nor by the high-density free electrons (reflective response based on Drude model), but by the large optical constants (refractive index and extinction coefficient) of the film, as speculated previously. Full article

(This article belongs to the Section Functional Polymer Coatings and Films)

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11 pages, 5248 KiB

Open AccessArticle

α-MnO₂ Nanowires as Potential Scaffolds for a High-Performance Formaldehyde Gas Sensor Device

by Ahmad Umar, Ahmed A. Ibrahim, Rajesh Kumar, Hassan Algadi, Hasan Albargi, Faheem Ahmad, Wen Zeng and M. Shaheer Akhtar

Coatings 2021, 11(7), 860; https://doi.org/10.3390/coatings11070860 - 17 Jul 2021

Cited by 10 | Viewed by 2416

Abstract

Herein, we report a chemi-resistive sensing method for the detection of formaldehyde (HCHO) gas. For this, α-MnO₂ nanowires were synthesized hydrothermally and examined for ascertaining their chemical composition, crystal phase, morphology, purity, and vibrational properties. The XRD pattern confirmed the high crystallinity [...] Read more.

Herein, we report a chemi-resistive sensing method for the detection of formaldehyde (HCHO) gas. For this, α-MnO₂ nanowires were synthesized hydrothermally and examined for ascertaining their chemical composition, crystal phase, morphology, purity, and vibrational properties. The XRD pattern confirmed the high crystallinity and purity of the α-MnO₂ nanowires. FESEM images confirmed a random orientation and smooth-surfaced wire-shaped morphologies for as-synthesized α-MnO₂ nanowires. Further, the synthesized nanowires with rounded tips had a uniform diameter throughout the length of the nanowires. The average diameter of the α-MnO₂ nanowires was found to be 62.18 nm and the average length was ~2.0 μm. Further, at an optimized temperature of 300 °C, the fabricated HCHO sensor based on α-MnO₂ nanowires demonstrated gas response, response, and recovery times of 19.37, 18, and 30 s, respectively. Full article

(This article belongs to the Section Thin Films)

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16 pages, 2410 KiB

Open AccessArticle

Improvement of Water Resistance of Vegetable Proteins by the Use of Synthetic Origin Additives: Trials with Resins and Metal Ions

by Ilaria Santoni and Benedetto Pizzo

Coatings 2021, 11(7), 859; https://doi.org/10.3390/coatings11070859 - 17 Jul 2021

Cited by 2 | Viewed by 2026

Abstract

The adhesives industry is increasingly interested in products coming from natural and renewable resources. The aim of the present work was to improve the water resistance of soy-based proteins by using synthetic and formaldehyde-free additives. These include polyamide-amine epichlorohydrin (PAE), different types of [...] Read more.

The adhesives industry is increasingly interested in products coming from natural and renewable resources. The aim of the present work was to improve the water resistance of soy-based proteins by using synthetic and formaldehyde-free additives. These include polyamide-amine epichlorohydrin (PAE), different types of isocyanates, and combinations of these cross-linkers between them and with other agents, including metal ions. In addition, the effect of both curing temperature and maturation time was assessed. Performances were evaluated by means of shear strength tests, solubility tests, and spectroscopic analysis. The obtained results showed that while isocyanates reacted completely but with water instead of proteins, tests with PAE were generally successful. In fact, the insoluble residue as well as the shear strength in wet conditions dramatically increased after PAE addition. Moreover, the wet performances of protein/PAE formulations appreciably increased gluing at 60 °C instead of room temperature. Furthermore, the maturation time had a positive effect on the formulations where metal ions were added, both for solubility and wet shear strength. Actually, for the very long conditioning time of 3 months, a significant and substantial increase of wet shear strength was observed for the series protein/PAE/aluminum. Full article

(This article belongs to the Special Issue New Challenges in Wood Adhesives and Coatings)

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12 pages, 2987 KiB

Open AccessArticle

Sintering of Potassium Doped Hydroxy-Fluorapatite Bioceramics

by Jihen Ben Slimen, Mustapha Hidouri, Marwa Ghouma, Ezzedine Ben Salem and Sergey V. Dorozhkin

Coatings 2021, 11(7), 858; https://doi.org/10.3390/coatings11070858 - 17 Jul 2021

Cited by 6 | Viewed by 2379

Abstract

The present study describes the influence of potassium and hydroxyl substitutions on the structural, thermal and mechanical properties of fluorapatite bioceramics. A set of non-stoichiometric ion-substituted compounds, with a chemical formula of Ca_10−xK_x(PO₄)₆F₍₂₋₂ [...] Read more.

The present study describes the influence of potassium and hydroxyl substitutions on the structural, thermal and mechanical properties of fluorapatite bioceramics. A set of non-stoichiometric ion-substituted compounds, with a chemical formula of Ca_10−xK_x(PO₄)₆F_(2−2x)(OH)_x with 0 ≤ x ≤ 1 synthesized by the wet precipitation method, were found to be single-phase apatites crystallizing in the hexagonal P6₃/m space group. The structural parameters, as well as the crystallite sizes, increased accordingly to the amount of added dopant-ions. The thermal behavior of these compounds, studied within the temperature range 500–1200 °C, indicated a partial decomposition of the apatitic phase and its transformation to tricalcium phosphate β-Ca₃(PO₄)₂ at temperatures exceeding 750 °C. A relative density of the sintered samples achieved the highest value with x = 0.25 and reached about 95% after sintering at 1050 °C for 1 h. The microstructures of the sintered samples were of a trans-granular aspect and experienced an increase in the radius of their pores as x increased. The prepared bioceramic materials were mechanically characterized by means of Young’s modulus, flexural strength and fracture toughness measurements. The overall trend of these parameters evolved comparably to the relative density, and the maximum values obtained for x = 0.25 were measured to be 96 MPa, 47 MPa and 1.14 MPa·m^1/2, respectively. Full article

(This article belongs to the Special Issue Hydroxyapatite Based Coatings for Biomedical Applications)

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11 pages, 7326 KiB

Open AccessFeature PaperArticle

Bioactive Plasma Coatings on Orthodontic Brackets: In Vitro Metal Ion Release and Cytotoxicity

by Lasni Samalka Kumarasinghe, Neethu Ninan, Panthihage Ruvini Lakshika Dabare, Alex Cavallaro, Esma J. Doğramacı, Giampiero Rossi-Fedele, Craig Dreyer, Krasimir Vasilev and Peter Zilm

Coatings 2021, 11(7), 857; https://doi.org/10.3390/coatings11070857 - 17 Jul 2021

Cited by 4 | Viewed by 2250

Abstract

The metal ion release characteristics and biocompatibility of meta-based materials are key factors that influence their use in orthodontics. Although stainless steel-based alloys have gained much interest and use due to their mechanical properties and cost, they are prone to localised attack after [...] Read more.

The metal ion release characteristics and biocompatibility of meta-based materials are key factors that influence their use in orthodontics. Although stainless steel-based alloys have gained much interest and use due to their mechanical properties and cost, they are prone to localised attack after prolonged exposure to the hostile oral environment. Metal ions may induce cellular toxicity at high dosages. To circumvent these issues, orthodontic brackets were coated with a functional nano-thin layer of plasma polymer and further immobilised with enantiomers of tryptophan. Analysis of the physicochemical properties confirmed the presence of functional coatings on the surface of the brackets. The quantification of metal ion release using mass spectrometry proved that plasma functionalisation could minimise metal ion release from orthodontic brackets. Furthermore, the biocompatibility of the brackets has been improved after functionalisation. These findings demonstrate that plasma polymer facilitated surface functionalisation of orthodontic brackets is a promising approach to reducing metal toxicity without impacting their bulk properties. Full article

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14 pages, 3444 KiB

Open AccessArticle

Tensile Load Distribution Improvement of Three-Row Riveted Lap Joint Based on Different Squeezing Displacement Combinations

by Changyi Lei, Qinggai Huang and Yunbo Bi

Coatings 2021, 11(7), 856; https://doi.org/10.3390/coatings11070856 - 16 Jul 2021

Cited by 1 | Viewed by 2525

Abstract

Many previous studies have mainly focused on the effects of riveting parameters on single-row riveted lap joints. Little attention has been paid to multi-row riveted lap joints. The outer rows of a normal multi-row riveted lap joint usually bear a larger part of [...] Read more.

Many previous studies have mainly focused on the effects of riveting parameters on single-row riveted lap joints. Little attention has been paid to multi-row riveted lap joints. The outer rows of a normal multi-row riveted lap joint usually bear a larger part of the tensile load. However, none of the studies relate the phenomenon to the squeezing displacement combination of a multi-row riveted lap joint. To improve the performance of a three-row riveted lap joint, this paper aims to reveal the internal relation between tensile load distribution, structural deformation and squeezing displacement combination. Theoretical discussion, numerical simulation and an experimental test have been conducted. Four different squeezing displacement combinations have been studied. The result indicates that an appropriate squeezing displacement combination can effectively make tensile load distribution more homogeneous. Each rivet can take approximately 33% tensile load. Structural deformation magnitude can be reduced as well. Compared with the worst situation, at the region most sensitive to tensile load, the max strain value can reduce about 53.22–79.76%. A suitable squeeze displacement combination is a simple approach for the performance enhancement of a three-row riveted lap joint. It can be practically applied in aircraft manufacturing without any additional equipment or skill learning. Full article

(This article belongs to the Special Issue Advanced Joining Technologies of Alloys and Composites in the Automotive, Aeronautic and Astronautic Fields)

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24 pages, 34519 KiB

Open AccessFeature PaperArticle

Application of Adaptive Materials and Coatings to Increase Cutting Tool Performance: Efficiency in the Case of Composite Powder High Speed Steel

by Sergey N. Grigoriev, Mars S. Migranov, Yury A. Melnik, Anna A. Okunkova, Sergey V. Fedorov, Vladimir D. Gurin and Marina A. Volosova

Coatings 2021, 11(7), 855; https://doi.org/10.3390/coatings11070855 - 16 Jul 2021

Cited by 7 | Viewed by 3189

Abstract

The paper proposes a classification of adaptive materials and coatings for tool purposes, showing the ability to adapt to external heat and power influences, thereby improving tool life. Creating a cutting tool made of composite powder high speed steels containing refractory TiC, TiCN, [...] Read more.

The paper proposes a classification of adaptive materials and coatings for tool purposes, showing the ability to adapt to external heat and power influences, thereby improving tool life. Creating a cutting tool made of composite powder high speed steels containing refractory TiC, TiCN, and Al₂O₃ compounds for milling 41CrS4 steel demonstrated the effectiveness of the adaptive materials. The tool material characteristics under the external loads’ influence and the surface layer adaptation to the heat–power exposure conditions were shown by the temperature field study using a semiartificial microthermocouple method (the level of fields is reduced by 20%–25% for 80% HSS + 20% TiCN), frictional interaction high-temperature tribometry (the coefficient of friction did not exceed 0.45 for 80% HSS + 20% TiCN at +20 and 600 °C), laboratory performance tests, and spectrometry of the surface layer secondary structures. Spectral analysis shows the highest spectrum intensity of TiC₂ after 5 min of running in. After 20 min of milling (V = 82 m/min, f = 0.15 mm/tooth), dicarbide decomposes and transits to thermally stable secondary phase films of good lubricity such as TiO (maximum) and TiN (partially). There was an increase in tool life of up to 2 times (>35 min for 80% HSS + 20% TiCN), and a decrease in the roughness of up to 2.9 times (R_a less than 4.5 µm after 25 min of milling). Full article

(This article belongs to the Special Issue Technologies of Coatings and Surface Hardening for Tool Industry)

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13 pages, 20256 KiB

Open AccessArticle

Simple and Rapid Preparation of MIL-121 with Small Particles for Lithium Adsorption from Brine

by Qinyan Wei, Bingqian Shi, Fei Wang, Shuoshuo Shao, Liang Zhu and Xiaoyu Zhao

Coatings 2021, 11(7), 854; https://doi.org/10.3390/coatings11070854 - 16 Jul 2021

Cited by 10 | Viewed by 3793

Abstract

A novel method to generate an aluminum-based MOF material named as MIL-121 was investigated. MIL-121, [Al(OH)(H₂BTEC)·(H₂O)]n is a prototypal aluminum MOF with 1,2,4,5-benzenetetracarboxylic acid (BTEC) linkers, which was normally produced by the hydrothermal method. Different from the hydrothermal method, [...] Read more.

A novel method to generate an aluminum-based MOF material named as MIL-121 was investigated. MIL-121, [Al(OH)(H₂BTEC)·(H₂O)]n is a prototypal aluminum MOF with 1,2,4,5-benzenetetracarboxylic acid (BTEC) linkers, which was normally produced by the hydrothermal method. Different from the hydrothermal method, the developed novel method does not involve high temperature and high pressure, instead the MOF material was produced by the traditional cooling crystallization method at ambient pressure and low temperature below 100 °C. The MIL-121 obtained by the novel method possesses the same lithium adsorption performance as that obtained by hydrothermal method, but with lower energy consumption and more environmentally friendly. Compared with hydrothermal method, this method has more advantage to be scaled up to industrialized production. The formation mechanism of MIL-121 in the novel method including nucleation and growth process of MOF crystal was studied. The results indicated that the size and morphology of MIL-121 crystals were influenced by the temperature and additives, respectively. As the reaction temperature increased to 100 °C, the operation time can be shortened to 2–5 h. The crystal habit that was predicted by Material studio software using BFDH, which is a model for crystal habit prediction proposed by Bravais, Friedel, Donnay, and Harker based on the crystal lattice parameters and crystal symmetry in the Morphology module, the simulated morphology of MIL-121 was in accord with that of the products obtained by cooling crystallization. The thermal stability of MIL-121 obtained by cooling crystallization is better than that obtained by the hydrothermal method. Full article

(This article belongs to the Section Environmental Aspects in Colloid and Interface Science)

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11 pages, 6323 KiB

Open AccessArticle

Optimization Study of Fluffy Materials Flocking Drainage Pipes to Resist Blockage Based on MD Binding Energy

by Shiyang Liu, Xuefu Zhang, Yuanfu Zhou and Feng Gao

Coatings 2021, 11(7), 853; https://doi.org/10.3390/coatings11070853 - 15 Jul 2021

Cited by 4 | Viewed by 1822

Abstract

Drainage pipe blockage resulting from crystals is one of the causes for cracking and leakage of tunnel lining. Therefore, effective prevention from drainage pipe blockage caused by crystals is crucial to ensure the safety and stability of lining structures during the operation of [...] Read more.

Drainage pipe blockage resulting from crystals is one of the causes for cracking and leakage of tunnel lining. Therefore, effective prevention from drainage pipe blockage caused by crystals is crucial to ensure the safety and stability of lining structures during the operation of tunnel drainage system. Based on a large number of indoor model tests and numerical simulation analyses, binding energy between four materials and the calcium carbonate aqueous solution (“solid + liquid” system) and that between the four materials and the two typical growth crystals of calcium carbonate (“solid + solid” system) were studied. The research results indicated that: (1) The four materials all had an adsorption effect on the calcium carbonate aqueous solution system, and the PA6 had the greatest adsorption effect while the PP had the smallest adsorption effect; (2) There was spontaneous adsorption between the PVC or PA6 and the two typical growth crystals of calcium carbonate and no adsorption between the PP or SiC and the two typical growth crystals of calcium carbonate unless external energy was in place; (3) The PP and SiC can be used as the materials for drainage pipe flocking, but it shall be ensured that the fluffy material has a good geometrical property. The prevention technology for crystallization that causes drainage pipe blockage fills the gap in the research of drainage pipe blockage caused by crystals, which can reduce the maintenance cost for the operation of the tunnel drainage system and ensure safe and normal operation of the tunnel. Full article

(This article belongs to the Special Issue Corrosion and Degradation of Materials)

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16 pages, 823 KiB

Open AccessArticle

Continuous Mechanical Extraction of Fibres from Linseed Flax Straw for Subsequent Geotextile Applications

by Saif Ullah Khan, Laurent Labonne, Pierre Ouagne and Philippe Evon

Coatings 2021, 11(7), 852; https://doi.org/10.3390/coatings11070852 - 15 Jul 2021

Cited by 5 | Viewed by 2669

Abstract

Linseed flax is a multipurpose crop. It is cultivated for its seeds and particularly for its oil. The main contributors for this crop are Canada, France and Belgium. In general, straws of linseed flax are buried in the fields or burnt. However, these [...] Read more.

Linseed flax is a multipurpose crop. It is cultivated for its seeds and particularly for its oil. The main contributors for this crop are Canada, France and Belgium. In general, straws of linseed flax are buried in the fields or burnt. However, these solutions are not good practices for the environment and from an economical point of view. In this study, straws of linseed flax (six batches in total) with different dew retting durations and harvesting techniques were studied to possibly use them for producing innovative geotextiles. Two different fibre extraction processes were investigated. A first process (A) involved horizontal breaker rollers and then a breaking card. A second one (B) consisted in using vertical breaker rollers, and an “all fibre” extraction device (fibre opener) followed by sieving. The chemical composition of fibres in parietal constituents appeared to be globally equivalent to the one of textile flax with a pectic content decreasing as a function of the dew retting duration. This contributed to an increase in the cellulose content. The fibre content was situated in a range from 29% to 33%, which corresponds to a good yield for linseed flax fibre. The level of purity can reach values of up to 90% for method A (without extra-sieving) and 96% for method B (with extra-sieving), and the length of the fibres (larger for method A than for method B) and their tensile properties make them suitable for structural geotextile yarn manufacturing. Full article

(This article belongs to the Special Issue Natural Fiber Based Composites)

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12 pages, 2032 KiB

Open AccessArticle

Effects of Chromic Treatment on the Surface Properties of Polypropylene (PP) Wood Composites

by Marouan Rejeb, Ahmed Koubaa, Fayez Elleuch, François Godard, Sébastien Migneault, Besma Bouslimi, Mohamed Khlif and Hatem Mrad

Coatings 2021, 11(7), 851; https://doi.org/10.3390/coatings11070851 - 15 Jul 2021

Cited by 1 | Viewed by 2610

Abstract

The moisture sensitivity of wood–polymer composites (WPCs) is mainly related to their hydrophilic wood components. Coatings are among the alternatives that improve the dimensional stability of these composites. However, the adhesion of most coatings to the WPC surface is generally poor. Thus, chemical [...] Read more.

The moisture sensitivity of wood–polymer composites (WPCs) is mainly related to their hydrophilic wood components. Coatings are among the alternatives that improve the dimensional stability of these composites. However, the adhesion of most coatings to the WPC surface is generally poor. Thus, chemical and/or mechanical treatments should be applied to the WPC surface to improve the coating adhesion. Therefore, the main objective of this study was to improve the adhesion coating of polypropylene (PP) WPCs through a chromic treatment. PP was reinforced by three different pulp fibers (kraft, thermomechanical (TMP), and chemothermomechanical (CTMP)) at three fiber contents (50, 60, and 70% w/w). A chromic treatment was applied to the PP-based WPCs to activate the surface of the composites and alter their roughness parameters, creating a higher interfacial zone that improved the bonding of the epoxy coating to the surface of the PP composites. The chromic treatment increased the roughness of the surface. An increase in profile and surface parameters was observed after treatment. This treatment modified the chemical composition of the surface by creating polar carbon–oxygen groups and increasing the carbonyl and hydroxyl indexes. Full article

(This article belongs to the Special Issue Recent Developments and Trends in Wood Coatings)

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15 pages, 3365 KiB

Open AccessArticle

Removal of As(V) Based on Amino-Group Surface-Functionalized Porous Silicon Derived from Photovoltaic Silicon Cutting Powder

by Kaixin Fu, Yi Li, Xiumin Chen, Wenhui Ma, Ziheng Yang, Tong Wang, Jiasen Liu, Zhuang Ma, Ran Chen, Xiuhua Chen and Shaoyuan Li

Coatings 2021, 11(7), 850; https://doi.org/10.3390/coatings11070850 - 15 Jul 2021

Viewed by 2139

Abstract

In this study, amino group surface-functionalized porous silicon adsorbent was successfully prepared for the first time using diamond wire saw silicon powder (DWSSP) as raw material through copper-assisted chemical etching (Cu-ACE) and organic functional group grafting. Amino-functionalized porous silicon adsorbent (TEPA-GTS-NPSi) can be [...] Read more.

In this study, amino group surface-functionalized porous silicon adsorbent was successfully prepared for the first time using diamond wire saw silicon powder (DWSSP) as raw material through copper-assisted chemical etching (Cu-ACE) and organic functional group grafting. Amino-functionalized porous silicon adsorbent (TEPA-GTS-NPSi) can be used for removing As(V) from water. The properties and mechanism of the new adsorbent were characterized by infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (FE-SEM), Brunauer–Emmett–Teller analysis (BET), and thermogravimetric analysis (TGA). The concentration of metal ions in the solution was determined by inductively coupled plasma spectrometry. Meanwhile, the effects of initial pH, adsorption time, initial concentration and adsorbent dosage on the removal of As(V) in an aqueous solution were studied by intermittent adsorption experiments. The results showed that the adsorption equilibrium could be reached rapidly after 30 min soaking. Under the optimized pH of 7, the maximum adsorption capacity was 13.2 mg/g, and the minimum adsorption limit was 3 mg/L. The adsorbent shows good adsorption performance after five successive regenerated cycles. Based on the density functional theory (DFT) analysis results, the adsorption mechanism is attributed to hydrogen bond interaction between the NH₂ group and As(V) ions. Full article

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0 pages, 55074 KiB

Open AccessArticle

Curcuma longa Mediated Synthesis of Copper Oxide, Nickel Oxide and Cu-Ni Bimetallic Hybrid Nanoparticles: Characterization and Evaluation for Antimicrobial, Anti-Parasitic and Cytotoxic Potentials

by Shah Faisal, Najlaa S. Al-Radadi, Hasnain Jan, Abdullah, Sajjad Ali Shah, Sumaira Shah, Muhammad Rizwan, Zobia Afsheen, Zahid Hussain, Muhammad Nazir Uddin, Muhammad Idrees and Nadia Bibi

Coatings 2021, 11(7), 849; https://doi.org/10.3390/coatings11070849 - 14 Jul 2021

Cited by 42 | Viewed by 5118 | Correction

Abstract

Nanoparticles have long been known and their biomedical potent activities have proven that these can provide an alternative to other drugs. In the current study, copper oxide, nickel oxide and copper/nickel hybrid NPs were biosynthesized by using Curcuma longa root extracts as a [...] Read more.

Nanoparticles have long been known and their biomedical potent activities have proven that these can provide an alternative to other drugs. In the current study, copper oxide, nickel oxide and copper/nickel hybrid NPs were biosynthesized by using Curcuma longa root extracts as a reducing and capping agent, followed by characterization via UV-spectroscopy, Fourier transformed infrared spectroscopy (FTIR), energy dispersive X-ray (EDX), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermo galvanometric analysis (TGA), and band gap. FTIR spectroscopy shows the availability of various functional groups and biomolecules such as carbohydrate, protein, polysaccharides, etc. The EDX peak confirmed that the elemental nickel and copper were present in large quantity in the analyzed sample. Scanning electron micrographs showed that the synthesized CuO-NPs and NiO-NPs were polyhedral uniform and homogeneous in morphology, while the copper/nickel hybrid NPs were well dispersed, spherical in shape, and uniform in size. TEM micrographs of CuO-NPs had 27.72 nm, NiO had 23.13 nm and, for their hybrid, the size was 17.38 nm, which was confirmed respectively. The CuO and NiO NPs possessed spherical- to multi-headed shapes, while their hybrid showed a complete spherical shape, small size, and polydispersed NPs. The XRD spectra revealed that the average particle size for CuO, NiO, and hybrid were 29.7 nm, 28 nm and 27 nm, respectively. Maximum anti-diabetic inhibition of (52.35 ± 0.76: CuO-NPs, 68.1 ± 0.93: NiO-NPs and 74.23 ± 0.42: Cu + Ni hybrids) for α-amylase and (39.25 ± 0.18 CuO-NPs, 52.35 ± 1.32: NiO-NPs and 62.32 ± 0.48: Cu + Ni hybrids) for α-glucosidase were calculated, respectively, at 400 µg/mL. The maximum antioxidants capacity was observed as 65.1 ± 0.83 μgAAE/mg for Cu-Ni hybrids, 58.39 ± 0.62 μgAAE/mg for NiO-NPs, and 52.2 ± 0.31 μgAAE/mg for CuO-NPs, respectively, at 400 μg/mL. The highest antibacterial activity of biosynthesized NPs was observed against P. aeuroginosa (28 ± 1.22) and P. vulgaris (25 ± 1.73) for Cu + Ni hybrids, respectively. Furthermore, the antibiotics were coated with NPs, and activity was noted. Significant anti-leishmanial activity of 60.5 ± 0.53 and 68.4 ± 0.59 for Cu + Ni hybrids; 53.2 ± 0.48 and 61.2 ± 0.44 for NiO-NPs; 49.1 ± 0.39 and 56.2 ± 0.45 for CuO-NPs at 400 μg/mL were recorded for promastigote and amastigotes, respectively. The biosynthesized NPs also showed significant anti-cancerous potential against HepG2 cell lines. It was concluded from the study that NPs are potential agents to be used as an alternative to antimicrobial agents. Full article

(This article belongs to the Special Issue New Advance in Nanoparticles, Fiber, and Coatings)

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12 pages, 4360 KiB

Open AccessArticle

Improving the CO and CH₄ Gas Sensor Response at Room Temperature of α-Fe₂O₃(0001) Epitaxial Thin Films Grown on SrTiO₃(111) Incorporating Au(111) Islands

by Aída Serrano, Jesús López-Sánchez, Iciar Arnay, Rosalía Cid, María Vila, Eduardo Salas-Cólera, Germán R. Castro and Juan Rubio-Zuazo

Coatings 2021, 11(7), 848; https://doi.org/10.3390/coatings11070848 - 14 Jul 2021

Cited by 5 | Viewed by 2248

Abstract

In this work, the functional character of complex α-Fe₂O₃(0001)/SrTiO₃(111) and Au(111) islands/α-Fe₂O₃(0001)/SrTiO₃(111) heterostructures has been proven as gas sensors at room temperature. Epitaxial Au islands and α-Fe₂O₃ thin [...] Read more.

In this work, the functional character of complex α-Fe₂O₃(0001)/SrTiO₃(111) and Au(111) islands/α-Fe₂O₃(0001)/SrTiO₃(111) heterostructures has been proven as gas sensors at room temperature. Epitaxial Au islands and α-Fe₂O₃ thin film are grown by pulsed laser deposition on SrTiO₃(111) substrates. Intrinsic parameters such as the composition, particle size and epitaxial character are investigated for their influence on the gas sensing response. Both Au and α-Fe₂O₃ layer show an island-type growth with an average particle size of 40 and 62 nm, respectively. The epitaxial and incommensurate growth is evidenced, confirming a rotation of 30° between the in-plane crystallographic axes of α-Fe₂O₃(0001) structure and those of SrTiO₃(111) substrate and between the in-plane crystallographic axes of Au(111) and those of α-Fe₂O₃(0001) structure. α-Fe₂O₃ is the only phase of iron oxide identified before and after its functionalization with Au nanoparticles. In addition, its structural characteristics are also preserved after Au deposition, with minor changes at short-range order. Conductance measurements of Au(111)/α-Fe₂O₃(0001)/SrTiO₃(111) system show that the incorporation of epitaxial Au islands on top of the α-Fe₂O₃(0001) layer induces an enhancement of the gas-sensing activity of around 25% under CO and 35% under CH₄ gas exposure, in comparison to a bare α-Fe₂O₃(0001) layer grown on SrTiO₃(111) substrates. In addition, the response of the heterostructures to CO gas exposure is around 5–10% higher than to CH₄ gas in each case. Full article

(This article belongs to the Special Issue Advanced Ceramic Films and Coatings)

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25 pages, 10539 KiB

Open AccessReview

Ultrasonic Technique for Production of Nanoemulsions for Food Packaging Purposes: A Review Study

by Hamed Ahari and Mina Nasiri

Coatings 2021, 11(7), 847; https://doi.org/10.3390/coatings11070847 - 14 Jul 2021

Cited by 9 | Viewed by 4144

Abstract

According to the loss of food due to expired shelf life, there is a global concern on food safety among food science researchers, and food microbiologists. So, any approaches contributing to improved food packaging is most welcome. It has been demonstrated that administration [...] Read more.

According to the loss of food due to expired shelf life, there is a global concern on food safety among food science researchers, and food microbiologists. So, any approaches contributing to improved food packaging is most welcome. It has been demonstrated that administration of essential oils, fades away the unsolved obstacles of conventional food packaging, reducing environmental concerns compared with conventional food packaging. Along with substantial progresses in nanoscience, there is a great interest toward usage of nanoemulsions-based delivery systems. They have potentials to simplify targeted delivery of compounds in a high surfaced area, aimed at increasing stability, biodegradability, anti-oxidation, and anti-microbial properties. There are a wide range of methods for fabrication of nanoemulsions. Among them, ultrasonic-based approaches have gained an acceptable efficiency for industrial fabrication of essential oils-based nanoemulsions due to refraining from loss of nutrients through non-thermal approaches. In summary, essential-oils based nanoemulsions are significant due to ability for reduction in microbial load of food-borne pathogens, and prolonged shelf life. Full article

(This article belongs to the Special Issue Recent Advances in the Use of Edible Thin Films/Coatings in Food Industries)

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20 pages, 11813 KiB

Open AccessArticle

Fibre Individualisation and Mechanical Properties of a Flax-PLA Non-Woven Composite Following Physical Pre-Treatments

by Maxime Gautreau, Antoine Kervoelen, Guillaume Barteau, François Delattre, Thibaut Colinart, Floran Pierre, Maxime Hauguel, Nicolas Le Moigne, Fabienne Guillon, Alain Bourmaud and Johnny Beaugrand

Coatings 2021, 11(7), 846; https://doi.org/10.3390/coatings11070846 - 14 Jul 2021

Cited by 5 | Viewed by 2862

Abstract

Pre-treatments for plant fibres are very popular for increasing the fineness of bundles, promoting individualisation of fibres, modifying the fibre-matrix interface or reducing water uptake. Most pre-treatments are based on the use of chemicals and raise concerns about possible harmful effects on the [...] Read more.

Pre-treatments for plant fibres are very popular for increasing the fineness of bundles, promoting individualisation of fibres, modifying the fibre-matrix interface or reducing water uptake. Most pre-treatments are based on the use of chemicals and raise concerns about possible harmful effects on the environment. In this study, we used physical pre-treatments without the addition of chemical products. Flax tows were subjected to ultrasound and gamma irradiation to increase the number of elementary fibres. For gamma pre-treatments, a 20% increase in the number of elementary fibres was quantified. The biochemical composition of pre-treated flax tows exhibited a partial elimination of sugars related to pectin and hemicelluloses depending on the pre-treatment. The hygroscopic behaviour showed a comparable decreasing trend for water sorption-desorption hysteresis for both types of pre-treatment. Then, non-woven composites were produced from the pre-treated tows using poly-(lactid) (PLA) as a bio-based matrix. A moderate difference between the composite mechanical properties was generally demonstrated, with a significant increase in the stress at break observed for the case of ultrasound pre-treatment. Finally, an environmental analysis was carried out and discussed to quantitatively compare the different environmental impacts of the pre-treatments for composite applications; the environmental benefit of using gamma irradiation compared to ultrasound pre-treatment was demonstrated. Full article

(This article belongs to the Special Issue Natural Fiber Based Composites)

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35 pages, 4238 KiB

Open AccessArticle

Application of Machine Learning to Solid Particle Erosion of APS-TBC and EB-PVD TBC at Elevated Temperatures

by Yuan Liu, Ravi Ravichandran, Kuiying Chen and Prakash Patnaik

Coatings 2021, 11(7), 845; https://doi.org/10.3390/coatings11070845 - 13 Jul 2021

Cited by 5 | Viewed by 3282

Abstract

Machine learning (ML) and deep learning (DL) for big data (BD) management are currently viable approaches that can significantly help in high-temperature materials design and development. ML-DL can accumulate knowledge by learning from existing data generated through multi-physics modelling (MPM) and experimental tests [...] Read more.

Machine learning (ML) and deep learning (DL) for big data (BD) management are currently viable approaches that can significantly help in high-temperature materials design and development. ML-DL can accumulate knowledge by learning from existing data generated through multi-physics modelling (MPM) and experimental tests (ETs). DL mainly involves analyzing nonlinear correlations and high-dimensional datasets implemented through specifically designed numerical algorithms. DL also makes it possible to learn from new data and modify predictive models over time, identifying anomalies, signatures, and trends in machine performance, develop an understanding of patterns of behaviour, and estimate efficiencies in a machine. Machine learning was implemented to investigate the solid particle erosion of both APS (air plasma spray) and EB-PVD (electron beam physical vapour deposition) TBCs of hot section components. Several ML models and algorithms were used such as neural networks (NNs), gradient boosting regression (GBR), decision tree regression (DTR), and random forest regression (RFR). It was found that the test data are strongly associated with five key factors as identifiers. Following test data collection, the dataset is subjected to sorting, filtering, extracting, and exploratory analysis. The training and testing, and prediction results are analysed. The results suggest that neural networks using the BR model and GBR have better prediction capability. Full article

(This article belongs to the Special Issue Current Status of Fundamentals and Applications of Thermal Barrier Coatings)

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9 pages, 2811 KiB

Open AccessCommunication

Discontinuous Powder Aerosol Deposition: An Approach to Prepare Films Using Smallest Powder Quantities

by Mario Linz, Jörg Exner, Jaroslaw Kita, Florian Bühner, Martin Seipenbusch and Ralf Moos

Coatings 2021, 11(7), 844; https://doi.org/10.3390/coatings11070844 - 13 Jul 2021

Cited by 4 | Viewed by 2282

Abstract

This work shows that the powder aerosol deposition (PAD) method allows the formation of films in powder quantities of less than 60 mg, rather than the large amounts that are typically required for conventional powder aerosol deposition systems. This was achieved by changing [...] Read more.

This work shows that the powder aerosol deposition (PAD) method allows the formation of films in powder quantities of less than 60 mg, rather than the large amounts that are typically required for conventional powder aerosol deposition systems. This was achieved by changing the operation mode to a discontinuous one, resulting in operation times of several seconds. Semiconducting strontium titanate ferrate SrTi_0.65Fe_0.35O_3−δ (STF35) was used as the powder to prove the equal behavior in terms of adhesion, film quality and electric conductivity compared to conventional powder-aerosol-deposited films. Full article

(This article belongs to the Section Ceramic Coatings and Engineering Technology)

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17 pages, 7351 KiB

Open AccessArticle

Isothermal Oxidation Performance of Laser Cladding Assisted with Preheat (LCAP) Tribaloy T-800 Composite Coatings Deposited on EN8

by Sipiwe Trinity Nyadongo, Sisa Lesley Pityana and Eyitayo Olatunde Olakanmi

Coatings 2021, 11(7), 843; https://doi.org/10.3390/coatings11070843 - 13 Jul 2021

Cited by 7 | Viewed by 1729

Abstract

It is anticipated that laser cladding assisted with preheat (LCAP)-deposited Tribaloy (T-800) composite coatings enhances resistance to structural degradation upon exposure to elevated-temperature oxidation service environments. The oxidation kinetics of LCAP T-800 composite coatings deposited on EN8 substrate and its mechanisms have not [...] Read more.

It is anticipated that laser cladding assisted with preheat (LCAP)-deposited Tribaloy (T-800) composite coatings enhances resistance to structural degradation upon exposure to elevated-temperature oxidation service environments. The oxidation kinetics of LCAP T-800 composite coatings deposited on EN8 substrate and its mechanisms have not been explored in severe conditions that are similar to operational parameters. The isothermal oxidation behaviour of the T-800 composite coating deposited on EN8 via LCAP was studied at 800 °C in air for up to 120 h (5 × 24 h cycles) and contrasted to that of uncoated samples. The mass gain per unit area of the coating was eight times less than that of the uncoated EN8 substrate. The parabolic rate constant

(K_{p})

for EN8 was 6.72 × 10⁻¹² g²·cm⁻⁴·s⁻¹, whilst that for the T-800 composite coating was 8.1 × 10⁻¹³ g²·cm⁻⁴·s⁻¹. This was attributed to a stable chromium oxide (Cr₂O₃) layer that formed on the coating surface, thereby preventing further oxidation, whilst the iron oxide film that formed on the EN8 substrate allowed the permeation of the oxygen ions into the oxide. The iron oxide (Fe₂O₃) film that developed on EN8 spalled, as evidenced by the cracking of oxide when the oxidation time was greater than 72 h, whilst the Cr₂O₃ film maintained its integrity up to 120 h. A parabolic law was observed by the T-800 composite coating, whilst a paralinear law was reported for EN8 at 800 °C up to 120 h. This coating can be used in turbine parts where temperatures are <800 °C. Full article

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11 pages, 2453 KiB

Open AccessArticle

Corrosion Resistance of Epoxy Coatings Modified by Bis-Silane Prepolymer on Aluminum Alloy

by Diping Zeng, Zhiyi Liu, Lihua Zou and Haijiang Wu

Coatings 2021, 11(7), 842; https://doi.org/10.3390/coatings11070842 - 13 Jul 2021

Cited by 14 | Viewed by 2642

Abstract

In this communication, a bis-silane prepolymer was used to modify epoxy resin, aiming to enhance the corrosion resistance of epoxy coatings on aluminum alloy substrates. The bis-silane prepolymer was prepared by tetraethoxysilane (TEOS) and γ-glycidoxypropyl trimethoxysilane (GPTMS). The corrosion behavior of silane-epoxy coatings [...] Read more.

In this communication, a bis-silane prepolymer was used to modify epoxy resin, aiming to enhance the corrosion resistance of epoxy coatings on aluminum alloy substrates. The bis-silane prepolymer was prepared by tetraethoxysilane (TEOS) and γ-glycidoxypropyl trimethoxysilane (GPTMS). The corrosion behavior of silane-epoxy coatings was studied. Compared with silane monomer-modified epoxy coatings, bis-silane-modified epoxy coatings have lower coating capacitance (C_c), higher charge transfer resistances (R_dl), and lower double layer capacitance (C_dl) during long-time immersion. It indicates that bis-silane-modified epoxy coating has stronger waterproof permeability and substrate corrosion protection ability. In addition, due to the leaching of the silane component and cross-linking reaction between different silanes during the immersion process, the bis-silane-modified epoxy coatings exhibit much stronger “self-healing” ability. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in Corrosion, Wear and Erosion Section)

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11 pages, 924 KiB

Open AccessArticle

Encapsulation of Curcumin in Persian Gum Nanoparticles: An Assessment of Physicochemical, Sensory, and Nutritional Properties

by Arash Ershadi, Karim Parastouei, Amin Mousavi Khaneghah, Zahra Hadian and Jose M. Lorenzo

Coatings 2021, 11(7), 841; https://doi.org/10.3390/coatings11070841 - 13 Jul 2021

Cited by 9 | Viewed by 2309

Abstract

Curcumin is the hydrophobic yellow pigment in turmeric with considerable health-promoting effects. However, its low water solubility and stability limit its application. In the current study, curcumin within Persian gum (PG) nanoparticles at 0.5%, 1%, and 1.5% PG concentrations were encapsulated. The size [...] Read more.

Curcumin is the hydrophobic yellow pigment in turmeric with considerable health-promoting effects. However, its low water solubility and stability limit its application. In the current study, curcumin within Persian gum (PG) nanoparticles at 0.5%, 1%, and 1.5% PG concentrations were encapsulated. The size of the nanoparticles was in the range of 326.0–397.4 nm. Based on the TEM images of curcumin-loaded nanoparticles, all samples had a spherical shape and existed in a particular form without aggregation. Encapsulation efficiency was in the range of 86.0–94.0%. Increasing PG concentration enhanced the encapsulation efficiency of curcumin. PG nanoparticles provided good protection on curcumin against light, hydrogen peroxide, and acidic pH. The lowest stability was related to free curcumin, and the highest was related to PG nanoparticles at 1.5% concentration. Curcumin-loaded nanoparticles at 1.5% concentration were added to kefir at 1%, 2%, and 3% concentrations. No significant differences were observed between acidity, pH, apparent viscosity, and consistency index of fortified and unfortified kefir samples. All kefir samples showed non-Newtonian behavior. Feeding rats with fortified kefir samples caused a lower level of low-density lipoprotein (LDL), total cholesterol (TC), and triglycerides (TG) compared to feeding with a standard diet. Full article

(This article belongs to the Special Issue Microencapsulation Technologies and Applications in Coatings and Films)

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15 pages, 9741 KiB

Open AccessArticle

Anethum graveolens Prevents Liver and Kidney Injury, Oxidative Stress and Inflammation in Mice Exposed to Nicotine Perinatally

by Jamaan S. Ajarem, Saleh N. Maodaa, Hamed A. El-Serehy, Naif Altoom, Ahmed A. Allam, Rene Hernandez-Bautista and Ayman M. Mahmoud

Coatings 2021, 11(7), 838; https://doi.org/10.3390/coatings11070838 - 13 Jul 2021

Viewed by 2087

Abstract

Perinatal exposure to nicotine imbalances the redox status in newborns. This study investigated the effect of Anethum graveolens (dill) extract on oxidative stress and tissue injury in the liver and kidney of mice newborns exposed to nicotine perinatally. Pregnant mice received nicotine (0.25 [...] Read more.

Perinatal exposure to nicotine imbalances the redox status in newborns. This study investigated the effect of Anethum graveolens (dill) extract on oxidative stress and tissue injury in the liver and kidney of mice newborns exposed to nicotine perinatally. Pregnant mice received nicotine (0.25 mg/kg) on gestational day 12 to day 5 after birth and/or A. graveolens extract on gestational day 1 to day 15 after birth. Newborn mice exposed to nicotine showed multiple histopathological alterations in the kidney and liver, including inflammatory cell infiltration and degenerative changes. Nicotine exposure increased hepatic and renal reactive oxygen species (ROS), lipid peroxidation, tumor necrosis factor (TNF-α), interleukin-6 (IL-6) and inducible nitric oxide synthase (iNOS) (p < 0.001), and decreased antioxidant defenses (p < 0.001). A. graveolens supplementation significantly prevented liver and kidney injury, suppressed ROS generation (p < 0.001), lipid peroxidation (p < 0.001) and inflammatory response (p < 0.001), and enhanced antioxidant defenses. In addition, A. graveolens upregulated hepatic and renal Nrf2 and HO-1 mRNA and increased HO-1 activity in normal and nicotine-exposed mice. In conclusion, A. graveolens protects against perinatal nicotine-induced oxidative stress, inflammation and tissue injury in the liver and kidney of newborn mice. A. graveolens upregulated hepatic and renal Nrf2/HO-1 signaling and enhanced antioxidant defenses in mice. Full article

(This article belongs to the Special Issue Biomedical Application of Natural Plant Extracts)

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