Coatings

10 pages, 3934 KiB

Open AccessArticle

Marine Biofilm Model Comprising a Loop-Type Biofilm Reactor and a Halomonas Strain HIG FST4 1, an Active Biofilm-Forming Bacterium

by Akiko Ogawa, Shoya Hosaka, Hideyuki Kanematsu and Michiko Yoshitake

Coatings 2022, 12(10), 1605; https://doi.org/10.3390/coatings12101605 - 21 Oct 2022

Cited by 2 | Viewed by 1302

Abstract

In ocean and coastal waters, the formation of biofilms on artificial matters often causes intractable phenomena such as the deterioration of surface functions and corrosion, resulting in significant economic damage. Thus, methods for inhibiting biofilm formation are in high demand, and many new [...] Read more.

In ocean and coastal waters, the formation of biofilms on artificial matters often causes intractable phenomena such as the deterioration of surface functions and corrosion, resulting in significant economic damage. Thus, methods for inhibiting biofilm formation are in high demand, and many new anti-biofilm products are being designed on a daily basis. However, practical and safe assays for evaluating anti-biofilm formation have not yet been established. In this study, we developed a more practical and safer biofilm formation test system composed of a loop-type laboratory biofilm reactor (LBR) and HIG FST4 1, a Halomonas strain derived from ballast seawater, in comparison with a slowly rotating test-tube culture (TTC) test. To evaluate biofilm formation in an LBR and TTC, three materials (pure iron, pure aluminum, and soda lime glass) were tested, and Raman spectroscopic analysis was used for the identification and relative quantification of the biofilm contents. Regardless of the test method, biofilm formation progressed in the order of soda lime glass < pure aluminum < pure iron. The Raman peaks showed that the LBR test samples tended to remove polysaccharides compared to the TTC test samples and that the proportion of proteins and lipids in the LBR test samples was much higher than that of the TTC test samples. These results show that the combination of HIG FST4 1 and LBR is suitable for biofilm formation in a practical marine environment. Full article

(This article belongs to the Special Issue Formation of Biofilms and Its Applications)

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14 pages, 5737 KiB

Open AccessArticle

Mitigating CMAS Attack in Model YAlO₃ Environmental Barrier Coatings: Effect of YAlO₃ Crystal Orientation on Apatite Nucleation

by Amanda Velázquez Plaza and Amanda R. Krause

Coatings 2022, 12(10), 1604; https://doi.org/10.3390/coatings12101604 - 21 Oct 2022

Cited by 2 | Viewed by 1957

Abstract

Environmental barrier coatings (EBCs) are used to protect ceramic-matrix composites from undesirable reactions with steam and calcia–magnesia–alumina–silicate (CMAS) particulates found in gas-turbine engine environments. Effective EBCs contain yttria or rare earth ions that will react with molten CMAS to form a protective apatite [...] Read more.

Environmental barrier coatings (EBCs) are used to protect ceramic-matrix composites from undesirable reactions with steam and calcia–magnesia–alumina–silicate (CMAS) particulates found in gas-turbine engine environments. Effective EBCs contain yttria or rare earth ions that will react with molten CMAS to form a protective apatite layer that prevents further attack. Methods to improve the EBCs’ CMAS mitigation capabilities focus on improving the apatite yield but neglect optimizing the apatite formation behavior. This study investigates the effect of apatite nucleation behavior on CMAS penetration by comparing the CMAS attack at 1350 °C of four different single crystal orientations of yttria aluminate perovskite (YAP), a promising EBC candidate. The EBC/CMAS interfacial energy and, thus, reaction behavior varies with YAP orientation. In regions with low CMAS loading, rapid apatite growth is seen on YAP substrates with orientations associated with high EBC/CMAS interfacial energy. However, CMAS penetration is most significant in these samples because the apatite growth is facilitated by recession of the YAP substrate nearby. Such behavior is not observed in regions with high CMAS loading where small apatite crystals form on top of an yttrium aluminate garnet (Y₃Al₅O₁₂, YAG) phase. This study shows that strategies that control the nucleation and growth of apatite will provide better protection against CMAS. Full article

(This article belongs to the Special Issue Advances in Environmental Barrier Coatings/Ceramic Matrix Composites)

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12 pages, 7283 KiB

Open AccessArticle

Simulation of a Painting Arc Connecting Surface by Moving the Nozzle Based on a Sliding Mesh Model

by Wenzhuo Chen, Yan Chen, Shanqiang Wang, Zhenyu Han, Meng Lu and Shiming Chen

Coatings 2022, 12(10), 1603; https://doi.org/10.3390/coatings12101603 - 21 Oct 2022

Cited by 4 | Viewed by 1177

Abstract

The paper proposes a sliding mesh model-based method to conduct a dynamic painting simulation for an arc connecting surface. In order to meet the requirements for using a sliding mesh model, the computational domain was designed with three parts—a stationary part, a translational [...] Read more.

The paper proposes a sliding mesh model-based method to conduct a dynamic painting simulation for an arc connecting surface. In order to meet the requirements for using a sliding mesh model, the computational domain was designed with three parts—a stationary part, a translational part and a rotational part. The film-forming model based on the Euler–Euler model and the conservation equation for a sliding mesh model were established. The dynamic painting of arc connecting surface with the angles of 60, 90 and 120 degrees under the nozzle speed of 100 mm/s were simulated. It was found that the thickness on the arc surface section was larger than those on the plane sections, and through an analysis of the vector distribution, the reason for this was that more paint would be deposited on the arc surface section than on the plane sections due to the concavity of the arc surface. The results obtained from the simulation were in a reasonable agreement with the experimental results, which indicates the proposed method would be effective and applicable in simulating a dynamic painting process. Full article

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11 pages, 4186 KiB

Open AccessArticle

Femtosecond Laser Texturization on Coated Steel

by Tomás Baldi-Boleda, Carles Colominas and Andrés García-Granada

Coatings 2022, 12(10), 1602; https://doi.org/10.3390/coatings12101602 - 21 Oct 2022

Cited by 1 | Viewed by 1449

Abstract

Surface textures such as laser-induced periodic surface structures (LIPSS) are of great interest to obtain industrial nanopatterns. In this work, plain uncoated 1.2344 steel with and without Chromium Nitride (CrN) and CrN plus diamond-like carbon (DLC) coatings were used in experiments. The laser [...] Read more.

Surface textures such as laser-induced periodic surface structures (LIPSS) are of great interest to obtain industrial nanopatterns. In this work, plain uncoated 1.2344 steel with and without Chromium Nitride (CrN) and CrN plus diamond-like carbon (DLC) coatings were used in experiments. The laser texturing variables studied were the laser speed (3000–4000 mm/s) and the distance between laser lines (1–10 microns). These structures were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM) to obtain an overview of the roughness and to analyze the heights of the obtained structures. A two-dimension fast Fourier transform (2D-FFT) of the SEM images and its characteristic frequencies was used to assess the periodicity of the textured surfaces and thus quantify the far-range order. The speed of laser depth ablation is related to the laser energy density for each coating and textures are qualified using the FFT approach. Full article

(This article belongs to the Special Issue Surface Function Enhancement Film and Coating Technology)

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11 pages, 4776 KiB

Open AccessArticle

Bond Strength between Different Zirconia-Based Ceramics and Resin Cement before and after Aging

by Marcos Paulo Motta Silveira, Nathália de Carvalho Ramos, Guilherme da Rocha Scalzer Lopes, João Paulo Mendes Tribst and Marco Antonio Bottino

Coatings 2022, 12(10), 1601; https://doi.org/10.3390/coatings12101601 - 21 Oct 2022

Cited by 7 | Viewed by 1653 | Correction

Abstract

The objective of this study was to evaluate the bond strength of different stabilized zirconias with resin cement and evaluate the susceptibility to thermal aging of the adhesive interface. Zirconia discs (Vita Zahnfabrik, Bad Säckingen, Germany) were obtained: 3Y-TZP first generation (translucent), 3Y-TZP [...] Read more.

The objective of this study was to evaluate the bond strength of different stabilized zirconias with resin cement and evaluate the susceptibility to thermal aging of the adhesive interface. Zirconia discs (Vita Zahnfabrik, Bad Säckingen, Germany) were obtained: 3Y-TZP first generation (translucent), 3Y-TZP third generation (high-translucent), 4Y-PSZ (super-translucent), and 5Y-PSZ (extra-translucent). Each disc had its surface polished with a standardized protocol. The specimens were cleaned and sintered according to the manufacturer’s recommendation (conventionally: ~12 h). However, 3Y-TZP groups were subdivided into subgroups and sintered following the speed sintering process (~80 min). After their sintering shrinkage, the dimensions of the final discs were 12 mm × 2 mm. The specimens were blasted with 50 μm aluminum oxide (1 cm distance, 2 bar pressure, and 2 s/cm²), cleaned, and silanized with an MDP primer. After the surface treatment, a resin cement cylinder was built on the ceramic surface (Ø = 1 mm; h = 2 mm). Half of the specimens of each group were subjected to a microshear bond strength test in a universal testing machine after 24 h of cementation, while the other half were subjected to thermocycling prior to the bond strength test (6000 cycles; 5 °C–55 °C, 30 s for each bath). Bond strength data were submitted to two-way ANOVA and Tukey’s test (95%), as well as Weibull analysis, to determine adhesive reliability. Bond strength was statistically different among the materials, and only 3Y-TZP third generation and 4Y-PSZ were not affected by thermal aging. The speed sintering method was statistically similar to the conventional process for 3Y-TZP first generation. However, 3Y-TZP third generation showed higher immediate bond strength when speed sintered. The Weibull modulus was superior for conventional 3Y-TZP third generation and 4Y-PSZ. In this study, thermal aging caused a degradation of the adhesive interfaces of 3Y-TZP first generation and 5Y-PSZ with the resin cement; however, it did not affect the interfaces of 3Y-TZP third generation and 4Y-PSZ. The speed sintering method did not affect the long-term bond strength with the resin cement. Adhesive reliability was superior for 3Y-TZP third generation and 4Y-PSZ. Full article

(This article belongs to the Special Issue The Relationship between Surfaces Coating and Biological, Mechanical and Clinical Behaviour)

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14 pages, 2265 KiB

Open AccessArticle

The Influence of Extractant Composition on the Asphaltenes Extracted from Asphalt

by Dachuan Sun, Yang Song and Feiyong Chen

Coatings 2022, 12(10), 1600; https://doi.org/10.3390/coatings12101600 - 21 Oct 2022

Cited by 2 | Viewed by 1364

Abstract

The compositions of extractants containing xylene (G) and n-heptane (P) recovered and reused in the asphaltene extraction process were determined by densimetry and the extracted asphaltenes were analyzed to study the influence of extractant composition on their elemental, spectral and structural properties. With [...] Read more.

The compositions of extractants containing xylene (G) and n-heptane (P) recovered and reused in the asphaltene extraction process were determined by densimetry and the extracted asphaltenes were analyzed to study the influence of extractant composition on their elemental, spectral and structural properties. With increasing the number of extraction, the G/P ratio in extractant increases, which dissolves more asphaltenes of higher aromaticity and causes a decrease of asphaltene yield, the polarity and aromaticity in molecular structure of the extracted asphaltenes. Asphaltenes extracted at a higher G/P ratio were found to have less fractions of N and O elements as well as higher fractions of H and S elements, a lower C/H atom ratio and molecular unsaturation. Moreover, they have a smaller fraction of aromatic rings and aromatic carbon ratio, a higher substitution rate on aromatic rings, a higher fraction of alkyl chain and free ends in their average molecular structure. Compared with the base asphalt, asphaltenes’ infrared absorptions generally move towards smaller wave numbers owing to more aromaticity in their molecules and subsequent stronger conjugative and inductive effects. The asphaltenes extracted at a higher G/P ratio have a denser packing of alkyl chains and a looser packing of aromatic rings, according to their spectra of X-ray diffraction. Full article

(This article belongs to the Special Issue Current Research in Cement and Building Materials)

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10 pages, 3155 KiB

Open AccessFeature PaperArticle

Carbon Nanocoils and Polyvinyl Alcohol Composite Films for Fiber-Optic Fabry–Perot Acoustic Sensors

by Yanming Sun, Zhe Dong, Zhezhe Ding, Neng Wang, Lei Sun, Heming Wei and Guo Ping Wang

Coatings 2022, 12(10), 1599; https://doi.org/10.3390/coatings12101599 - 21 Oct 2022

Cited by 4 | Viewed by 1466

Abstract

Carbon nanocoils (CNCs) are widely used in functional devices due to their helical morphology, which can be utilized in the fabrication of functional materials with unique properties. In this study, CNCs/polyvinyl alcohol (PVA) composite films were prepared using an electrostatic spinning method and [...] Read more.

Carbon nanocoils (CNCs) are widely used in functional devices due to their helical morphology, which can be utilized in the fabrication of functional materials with unique properties. In this study, CNCs/polyvinyl alcohol (PVA) composite films were prepared using an electrostatic spinning method and used to form a diaphragm for Fabry–Perot acoustic sensors. With the addition of CNCs, the fabricated composite film showed enhanced mechanical performance responding to acoustic wave pressure. Considering the optical and mechanical response, the content of CNCs was set as 0.14 wt.%; the highest acoustic wave pressure response of the sensor was 1.89 V/Pa at 16.2 kHz, which was relatively higher than that of devices with pure polymer films. Additionally, the sensor had a broadband frequency response from 2 to 10 kHz. The results indicate that the proposed composite film acoustic sensor is suitable for low-frequency acoustic sensing, which lays the foundation for the extended application of functional sensors based on CNCs. Full article

(This article belongs to the Special Issue Enhanced Thin-Film Application on Sensors)

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13 pages, 3573 KiB

Open AccessArticle

Phosphonium Modified Nanocellulose Membranes with High Permeate Flux and Antibacterial Property for Oily Wastewater Separation

by Kun Peng, Chenglong Wang, Chunyu Chang and Na Peng

Coatings 2022, 12(10), 1598; https://doi.org/10.3390/coatings12101598 - 21 Oct 2022

Cited by 8 | Viewed by 1599

Abstract

Nanocellulose membranes could efficiently separate oily wastewater because of their super-hydrophilic and underwater super-oleophobic property and nano-porous structure. However, the practical application and storage of nanocellulose membranes is limited by their low water permeation flux and easy corrosion by bacteria, respectively. Herein, nanocellulose [...] Read more.

Nanocellulose membranes could efficiently separate oily wastewater because of their super-hydrophilic and underwater super-oleophobic property and nano-porous structure. However, the practical application and storage of nanocellulose membranes is limited by their low water permeation flux and easy corrosion by bacteria, respectively. Herein, nanocellulose membranes with high permeate flux and antibacterial property were fabricated by grafting tetrakis(hydroxymethyl) phosphonium chloride (THPC) onto the surface of TEMPO-oxidized tunicate cellulose nanofibers (TCNFs) via esterification reaction. The introduction of THPC groups with tetrahedral structure on the surface of TCNFs significantly improved the pore size and interlayer space of nanocellulose membranes, resulting in an increase in water permeation flux. These THPC@TCNF membranes were super-hydrophilic and underwater super-oleophobic, which could effectively separate various oil/water nano-emulsions. Moreover, THPC@TCNF membranes possessed excellent durability, mechanical stability and cycling performance. Due to the presence of positively charged phosphonium groups, THPC@TCNF membranes exhibited excellent antibacterial property against B. subtilis, a typical Gram-positive bacterium presenting in oily wastewater. This work provides a simple method to endow nanocellulose membrane with high permeate flux and antibacterial property. Full article

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15 pages, 4764 KiB

Open AccessReview

Recent Advances of Sustainable Textile Fabric Coatings for UV Protection Properties

by Nour F. Attia, Rokaya Osama, Sally E. A. Elashery, Abul Kalam, Abdullah G. Al-Sehemi and Hamed Algarni

Coatings 2022, 12(10), 1597; https://doi.org/10.3390/coatings12101597 - 21 Oct 2022

Cited by 16 | Viewed by 4323

Abstract

The rapid progress in the use of textile fabric materials in various industrial and domestic applications requires the inclusion of smart functions to achieve comfortable and safety properties to the end users. However, among these functions is the protection against harmful UV rays [...] Read more.

The rapid progress in the use of textile fabric materials in various industrial and domestic applications requires the inclusion of smart functions to achieve comfortable and safety properties to the end users. However, among these functions is the protection against harmful UV rays that cause harmful effects to human beings and textile materials. To this end, coatings for smart textile fabrics have to be incorporated into textile fabrics. Therefore, in this review, recent advances in the development of coatings for sustainable textile fabrics for UV protection will be reviewed. Hence, the precursors, the synthesis routes and the types of coatings for sustainable textile fabrics will be reviewed. Furthermore, the UV protection action of the coatings for the protection of textile fabrics will be covered and studied. Interestingly, the multifunctional effect of the treated coatings, such as the antibacterial properties of the developed textile fabrics, will be also studied. Full article

(This article belongs to the Special Issue Coatings for Antimicrobial Textiles)

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17 pages, 4702 KiB

Open AccessReview

A Review of Effects of Femtosecond Laser Parameters on Metal Surface Properties

by Hongfei Sun, Jiuxiao Li, Mingliang Liu, Dongye Yang and Fangjie Li

Coatings 2022, 12(10), 1596; https://doi.org/10.3390/coatings12101596 - 21 Oct 2022

Cited by 14 | Viewed by 3093

Abstract

As a laser technology, the femtosecond laser is used in biomedical fields due to its excellent performance—its ultrashort pulses, high instantaneous power, and high precision. As a surface treatment process, the femtosecond laser can prepare different shapes on metal surfaces to enhance the [...] Read more.

As a laser technology, the femtosecond laser is used in biomedical fields due to its excellent performance—its ultrashort pulses, high instantaneous power, and high precision. As a surface treatment process, the femtosecond laser can prepare different shapes on metal surfaces to enhance the material’s properties, such as its wear resistance, wetting, biocompatibility, etc. Laser-induced periodic surface structures (LIPSSs) are a common phenomenon that can be observed on almost any material after irradiation by a linearly polarized laser. In this paper, the current research state of LIPSSs in the field of biomedicine is reviewed. The influence of laser parameters (such as laser energy, pulse number, polarization state, and pulse duration) on the generation of LIPSSs is discussed. In this paper, the applications of LIPSSs by femtosecond laser modification for various purposes, such as in functional surfaces, the control of surface wettability, the surface colonization of cells, and the improvement of tribological properties of surfaces, are reviewed. Full article

(This article belongs to the Special Issue Surface Modification Technology of Biomedical Metals)

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13 pages, 2711 KiB

Open AccessFeature PaperArticle

Investigation of Hybrid Films Based on Fluorinated Silica Materials Prepared by Sol–Gel Processing

by Violeta Purcar, Valentin Rădiţoiu, Florentina Monica Raduly, Alina Rădiţoiu, Simona Căprărescu, Adriana Nicoleta Frone, Cristian-Andi Nicolae and Mihai Anastasescu

Coatings 2022, 12(10), 1595; https://doi.org/10.3390/coatings12101595 - 20 Oct 2022

Cited by 1 | Viewed by 1868

Abstract

In this research, fluorinated silica materials were prepared through sol–gel processing with tetraethylorthosilicate (TEOS), triethoxymethylsilane (MTES), and trimethoxyhexadecylsilane (HDTMES), using a fluorinated solution (FS) under acidic medium. The fluorinated solution (FS) was obtained by diluting the perfluorooctanoic acid (PFOA) in 2-propanol. These fluorinated [...] Read more.

In this research, fluorinated silica materials were prepared through sol–gel processing with tetraethylorthosilicate (TEOS), triethoxymethylsilane (MTES), and trimethoxyhexadecylsilane (HDTMES), using a fluorinated solution (FS) under acidic medium. The fluorinated solution (FS) was obtained by diluting the perfluorooctanoic acid (PFOA) in 2-propanol. These fluorinated sol–gel silica materials were placed on the glass surfaces in order to achieve the antireflective and hydrophobic fluorinated hybrid films. The structure and surface properties of the final samples were investigated by Fourier transform infrared spectroscopy (FTIR), ultraviolet/visible spectroscopy, thermogravimetric analysis (TGA), atomic force microscopy (AFM), and contact angle (CA) determinations. FTIR spectra demonstrated the presence of a silica network modified with alkyl and fluoroalkyl groups. Thermal analysis showed that the fluorinated sol–gel silica materials prepared with HDTMES have a good thermostability in comparison with other samples. Ultraviolet/visible spectra indicated that the fluorinated hybrid films present a reflectance of ~9.5%, measured at 550 nm. The water contact angle analysis found that the wettability of fluorinated hybrid films was changed from hydrophilic (64°) to hydrophobic (~104°). These hybrid films based on fluorinated sol–gel silica materials can be useful in various electronics and optics fields. Full article

(This article belongs to the Special Issue Functional Films/Coatings Processing Technologies: Deposition and Process)

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13 pages, 4082 KiB

Open AccessArticle

Enhanced Pickering Emulsion Stabilization of Cellulose Nanocrystals and Application for Reinforced and Hydrophobic Coatings

by Fan Zhang, Haoran Tao, Yilin Li, Yanbing Wang, Yingying Zhou, Qunna Xu and Jianzhong Ma

Coatings 2022, 12(10), 1594; https://doi.org/10.3390/coatings12101594 - 20 Oct 2022

Cited by 2 | Viewed by 1540

Abstract

For oil-in-water (O/W) Pickering emulsions, a new polymer stabilizer of butyl acrylate (BA) grafted cellulose nanocrystals (BA-g-CNC_S) has been developed. By adjusting the BA concentration, the hydrophilic and hydrophobic surfaces of BA-g-CNCs could be systematically modified based [...] Read more.

For oil-in-water (O/W) Pickering emulsions, a new polymer stabilizer of butyl acrylate (BA) grafted cellulose nanocrystals (BA-g-CNC_S) has been developed. By adjusting the BA concentration, the hydrophilic and hydrophobic surfaces of BA-g-CNCs could be systematically modified based on the controllable interface activity. Specifically, the emulsification stability of the as-prepared stabilizer was examined as a function of BA content, BA-g-CNC_S usage, and oil type. The results showed that the Pickering emulsion stabilized by BA-g-CNC_S had a 98% volume fraction of emulsion with long-term stability. Importantly, BA-g-CNC_S could be a promising choice for polymer stabilizers and could generate high internal phase Pickering emulsions without cross-linking when combined with 13% BA and 1.75% BA-g-CNC_S. Furthermore, it was established that BA-g-CNCs possessed self-emulsifying quality, worked as hydrophobic coatings, and improved the mechanical properties. This was of fundamental interest to polymer stabilizer and functional coatings, allowing for promising applications in coating fields such as fabrics, leather, paper, controlled encapsulation, and the release of actives in material science. Full article

(This article belongs to the Special Issue Trends in Coatings and Surface Technology)

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17 pages, 6968 KiB

Open AccessArticle

Microstructure and Properties of TiAl Composite Coatings Prepared by Laser Cladding under Multi-Phase β₀/CoAl₂Ti Phase Strengthening

by Yuming Zhu, Xiaojie Song, Guoliang Ma, Hao Chen, Di Jiang, Minglei Liu, Quanzhi Wang, Xiaofeng Zhao, Hushan Niu and Hongzhi Cui

Coatings 2022, 12(10), 1593; https://doi.org/10.3390/coatings12101593 - 20 Oct 2022

Cited by 2 | Viewed by 1213

Abstract

Ceramic-reinforced TiAl matrix composite coatings are fabricated by laser cladding on Ti-6Al-4V (TC4) surfaces. The present work focuses on matching of the ceramic phase with the TiAl matrix to achieve a strength–toughness matching through the multi-scale multi-phase structure. The results indicated that the [...] Read more.

Ceramic-reinforced TiAl matrix composite coatings are fabricated by laser cladding on Ti-6Al-4V (TC4) surfaces. The present work focuses on matching of the ceramic phase with the TiAl matrix to achieve a strength–toughness matching through the multi-scale multi-phase structure. The results indicated that the structure of composites coatings, including γ, α₂, β₀, CoAl₂Ti, and TiC phases, significantly improved the properties of the composite coatings. The TiAl composite coating reached a maximum hardness of 741.17 Hv_0.2, and the 10 at% tungsten carbide (10 WC) coating has the lowest wear volume of 8.8 × 10⁷ μm³, the friction performance was approximate five times that of TC4. Detailed explanation of the friction properties and friction mechanism of the composite coating based on crystallographic orientation relationships and nanoindentation results. The study found that strength–toughness matching is important for the improvement of friction performance. Based on the TiAl alloy generated in the non-equilibrium solidification state in this paper, the solidification process and microstructure evolution are analyzed in detail. Full article

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15 pages, 4063 KiB

Open AccessArticle

Structural and Magnetic Specificities of Fe-B Thin Films Obtained by Thermionic Vacuum Arc and Magnetron Sputtering

by Cornel Staicu, Claudiu Locovei, Andrei Alexandru Dinu, Ion Burducea, Paul Dincă, Bogdan Butoi, Oana Gloria Pompilian, Corneliu Porosnicu, Cristian Petrica Lungu and Victor Kuncser

Coatings 2022, 12(10), 1592; https://doi.org/10.3390/coatings12101592 - 20 Oct 2022

Cited by 1 | Viewed by 1185

Abstract

Fe-B based compounds are of high interest due to their special properties and the wide range of involved applications. While B is the element that facilitates the increase in the hardness and the degree of wear resistance, it is also an effective glass [...] Read more.

Fe-B based compounds are of high interest due to their special properties and the wide range of involved applications. While B is the element that facilitates the increase in the hardness and the degree of wear resistance, it is also an effective glass former, controlling the formation of a much-desired amorphous structure with specific magnetic properties. Major difficulties related to the proper engineering of Fe-B thin films lay especially in their preparation under well-defined compositions, which in turn, should be accurately determined. The present study closely analyzes the morpho-structural and magnetic properties of thin coatings of Fe-B of approximately 100 nm thickness and with the nominal B content ranging from 5 at. % to 50 at. %. The comparison between films obtained by two preparation methods, namely, the thermionic vacuum arc and the magnetron sputtering is envisaged. Morpho-structural properties were highlighted using X-ray diffraction supplemented with X-ray reflectometry and scanning electron microscopy, whereas the elemental investigations were performed by X-ray dispersive spectroscopy and Rutherford back-scattering spectroscopy. The magnetic properties of the Fe-B layers were carefully investigated by the vectorial magneto-optic Kerr effect and conversion electron Mössbauer spectroscopy. The high capability of Mössbauer Spectroscopy to provide the phase composition and the B content in the formed Fe-B intermetallic films was proven, in correlation to Rutherford back-scattering techniques, and to explain their magnetic properties, including the magnetic texture of interest in many applications, in correlation with longitudinal magneto-optic-Kerr-effect-based techniques. Full article

(This article belongs to the Special Issue Advances of Nanoparticles and Thin Films)

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19 pages, 4134 KiB

Open AccessArticle

Modification of Shellac with Clove (Eugenia caryophyllata) and Thyme (Satureja hortensis) Essential Oils: Compatibility Issues and Effect on the UV Light Resistance of Wood Coated Surfaces

by Maria Cristina Timar and Emanuela Carmen Beldean

Coatings 2022, 12(10), 1591; https://doi.org/10.3390/coatings12101591 - 20 Oct 2022

Cited by 1 | Viewed by 1798

Abstract

Shellac (SL) is a natural resin employed for wood finishing, while clove (Eugenia caryophyllata) and thyme (Satureja hortensis) essential oils (C-EO, T-EO) are organic natural products of vegetal origin with antifungal, antimicrobial and antioxidant properties. The present paper aims [...] Read more.

Shellac (SL) is a natural resin employed for wood finishing, while clove (Eugenia caryophyllata) and thyme (Satureja hortensis) essential oils (C-EO, T-EO) are organic natural products of vegetal origin with antifungal, antimicrobial and antioxidant properties. The present paper aims at exploring the potential of modifying alcoholic shellac solutions with essential oils (C-EO, T-EO), focussing on the recurrent effects of this modification on the traditional wood finishing technique, the colour and the UV light resistance of the wood coated surfaces. The compatibility of C-EO and T-EO with ethyl alcohol and the alcoholic reference SL solution was evaluated, and modified SL solutions with a content of 5% and 10% C-EO and T-EO were prepared. Wood samples of European maple (Acer pseudoplatanus) and European walnut (Juglans regia) were finished with reference and modified SL solutions. An accelerated UV ageing test was run, and the samples were evaluated after 24, 48 and 72 h of exposure. Colour measurements in the CIELab system and FTIR–ATR investigation were employed for monitoring colour and surface chemistry changes. Coating with SL resulted in visible colour changes for both wood species (ΔE values of 31.06 for maple and 13.00 for walnut) and increased UV resistance, reducing colour changes after 72 h UV exposure (by 83% for maple and by 59% for walnut) as compared to the uncoated controls. Modification of SL solutions with C-EO and T-EO only slightly influenced the colour of finished surfaces (ΔE = 1.88–5.41 for maple, ΔE = 1.36–3.41 for walnut) and their UV resistance. The colour changes (ΔE) of coated surfaces after 72 h exposure varied in the range 1.63–4.53 for maple and 2.39–3.58 for walnut, being generally slightly higher (by 1.7–2.9 units for maple and 0–1 unit for walnut) for the modified SL solutions. FTIR investigation highlighted only minor chemical changes of the shellac coating films after 72 h of UV exposure. A photo-induced oxidative process of eugenol seemed possible in the case of SL modified with C-EO. Full article

(This article belongs to the Special Issue Wood Coatings: Formulation, Testing and Performance)

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15 pages, 4809 KiB

Open AccessArticle

Effect of Gamma Radiation on Structural and Optical Properties of ZnO and Mg-Doped ZnO Films Paired with Monte Carlo Simulation

by Mivolil Duinong, Rosfayanti Rasmidi, Fuei Pien Chee, Pak Yan Moh, Saafie Salleh, Khairul Anuar Mohd Salleh and Sofian Ibrahim

Coatings 2022, 12(10), 1590; https://doi.org/10.3390/coatings12101590 - 20 Oct 2022

Cited by 2 | Viewed by 1712

Abstract

In space, geostationary electronics located within the outer van Allen radiation belt are vulnerable to gamma radiation exposure. In terms of application, implementing an electronic system in a high radiation environment is impossible via conventional engineering materials such as metal alloys as they [...] Read more.

In space, geostationary electronics located within the outer van Allen radiation belt are vulnerable to gamma radiation exposure. In terms of application, implementing an electronic system in a high radiation environment is impossible via conventional engineering materials such as metal alloys as they are prone to radiation damage. Exposure to such radiation causes degradation and structural defects within the semiconductor component, significantly changing their overall density. The changes in the density will then cause electronic failure, known as the single event phenomena. Thus, the radiation response of material must be thoroughly investigated before the material is applied in a harsh radiation environment, specifically for flexible space borne electronic application. In this work, potential candidates for space-borne application devices: zinc oxide (ZnO) and Mg-doped ZnO thin film with a film thickness of 300 nm, were deposited onto an indium tin oxide (ITO) substrate via radio frequency (RF) sputtering method. The fabricated films were then irradiated by Co-60 gamma ray at a dose rate of 2 kGy/hr. The total ionizing dose (TID) effect of ZnO and Mg-doped ZnO thin films were then studied. From the results obtained, degradation towards the surface morphology, optical properties, and lattice parameters caused by increasing TID, ranging from 10 kGy–300 kGy, were evaluated. The alteration can be observed on the morphological changes due to the change in the roughness root mean square (RMS) with TID, while structural changes show increased strain and decreased crystallite size. For the optical properties, band gap tends to decrease with increased dose in response to colour centre (Farbe centre) effects resulting in a decrease in transmittance spectra of the fabricated films. Full article

(This article belongs to the Special Issue Optical Thin Film and Photovoltaic (PV) Related Technologies)

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16 pages, 5626 KiB

Open AccessArticle

Carbon Nanotube (CNT) Encapsulated Magnesium-Based Nanocomposites to Improve Mechanical, Degradation and Antibacterial Performances for Biomedical Device Applications

by Jinguo Zhao, Ma Haowei, Abbas Saberi, Zahra Heydari and Madalina Simona Baltatu

Coatings 2022, 12(10), 1589; https://doi.org/10.3390/coatings12101589 - 20 Oct 2022

Cited by 9 | Viewed by 2166

Abstract

Nowadays, magnesium (Mg) composites are gaining much attention in biomedical device applications due to their biocompatibility and biodegradability properties. This research is to study the microstructure, mechanical, corrosive and antibacterial properties of Mg−2.5Zn−0.5Zr/xCNT (x = 0, 0.3, 0.6, 0.9) composites made with mechanical [...] Read more.

Nowadays, magnesium (Mg) composites are gaining much attention in biomedical device applications due to their biocompatibility and biodegradability properties. This research is to study the microstructure, mechanical, corrosive and antibacterial properties of Mg−2.5Zn−0.5Zr/xCNT (x = 0, 0.3, 0.6, 0.9) composites made with mechanical alloying and semi-powder metallurgy (SPM) processes, accompanied by SPS. Based on the microstructural characteristics, CNTs were almost uniformly distributed in the Mg matrix. The results displayed that the hardness and ultimate compressive strength (UCS) of the composites were meaningfully increased compared to a Mg matrix. Moreover, the degradation rate of Mg composites was almost halved in the presence of small amounts of CNTs in the Kokubo simulated body fluid (SBF). Due to the slowed degradation process, the Mg−2.5Zn−0.5Zr/0.6CNT biocomposites exhibited excellent cellular compatibility. Evaluation of antibacterial activity displayed that adding CNTs to the Mg matrix could significantly prevent the growing of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). In general, the research results showed that CNTs are an efficient reinforcement for Mg−2.5Zn−0.5Zr/CNTs biocomposites, which leads to improved mechanical, degradation and antibacterial performances. Full article

(This article belongs to the Special Issue Application, Processing and Testing of Modern Biomaterials)

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15 pages, 4147 KiB

Open AccessArticle

Corrosion of Fe-Cr-Si Alloys in Oxidizing and Sulphidizing-Oxidizing Atmospheres

by Wenbo Li, Chenghao Xu, Ken Chen, Lanlan Liu, Haiyun Yang, Qiao Cheng and Minyu Zeng

Coatings 2022, 12(10), 1588; https://doi.org/10.3390/coatings12101588 - 20 Oct 2022

Cited by 3 | Viewed by 1795

Abstract

To clarify the mechanism of the third-element effect in sulphur-containing and sulphur-free oxidation environments, the corrosion behaviours of four kinds of Fe-xCr-ySi (x = 5, 10 at.% and y = 5, 10 at.%) alloys were studied at 600 °C in a H₂ [...] Read more.

To clarify the mechanism of the third-element effect in sulphur-containing and sulphur-free oxidation environments, the corrosion behaviours of four kinds of Fe-xCr-ySi (x = 5, 10 at.% and y = 5, 10 at.%) alloys were studied at 600 °C in a H₂-CO₂ and a H₂-CO₂-H₂S gaseous mixture with the same oxygen partial pressure. The results showed that, in the pure oxidizing atmosphere, thin and slowly growing protective oxide layers were formed on the alloys surfaces. Conversely, all alloys formed a corrosion product layer with an outer layer of FeS and an inner layer of a mix of oxides and sulphides in the oxidizing-sulphidizing atmosphere, which meant that adding Cr into the alloy as the third element had less of an effect on improving the alloy in the harsh sulphidizing-oxidizing environment. The oxidation and sulphidation mechanism as well as the effects of chromium and silicon on the corrosion resistance of the alloys was discussed. Full article

(This article belongs to the Topic Properties of the Corroding Interface)

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13 pages, 31471 KiB

Open AccessArticle

Magnetron Deposition of Cr Coatings with RF-ICP Assistance

by Dmitrii V. Sidelev, Vladislav A. Grudinin, Konstantin A. Zinkovskii, Kamila Alkenova and Galina A. Bleykher

Coatings 2022, 12(10), 1587; https://doi.org/10.3390/coatings12101587 - 20 Oct 2022

Cited by 2 | Viewed by 1248

Abstract

The article describes a comparative analysis of chromium coatings deposited by magnetron sputtering with and without ion assistance induced by a radiofrequency inductively coupled plasma (RF-ICP) source. Four series of 2 µm-thick Cr coatings were prepared, and then their cross-sectional microstructure, crystal structure [...] Read more.

The article describes a comparative analysis of chromium coatings deposited by magnetron sputtering with and without ion assistance induced by a radiofrequency inductively coupled plasma (RF-ICP) source. Four series of 2 µm-thick Cr coatings were prepared, and then their cross-sectional microstructure, crystal structure and corrosion resistance were investigated by scanning and transmission electron microscopy, X-ray diffraction and a potentiodynamic polarization method. RF-ICP assistance led to significant enhancement (almost twofold) of ion current density in a substrate. The role of RF-ICP assistance in coating properties for planetary-rotated substrates was defined in terms of ion-to-atom ratio in particle flux entering a substrate. Calculations of particle and ion flux densities revealed an increase in ion-to-atom ratio from 0.18 to 1.43 and 0.11 to 0.84 in substrate positions distant from the magnetron sputtering systems depending on their design. RF-ICP assistance is beneficial for depositing dense Cr coatings with increased corrosion resistance in a 3.5 wt.% NaCl solution. The corrosion rate of AISI 321 steel can be decreased from 6.2 × 10⁻⁶ to 4.0 × 10⁻⁸ mm/year by deposition of the dense Cr coating. Full article

(This article belongs to the Special Issue Advanced Coatings for Accident Tolerant Fuel Claddings)

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17 pages, 885 KiB

Open AccessReview

Metal Nanoparticles in Agriculture: A Review of Possible Use

by Amani Gabriel Kaningini, Aluwani Mutanwa Nelwamondo, Shohreh Azizi, Malik Maaza and Keletso Cecilia Mohale

Coatings 2022, 12(10), 1586; https://doi.org/10.3390/coatings12101586 - 20 Oct 2022

Cited by 18 | Viewed by 4624

Abstract

Deterioration of soils over the years has led to a decline in crop yields and nutritional qualities, resulting from the oversupply of conventional fertilizers, which are unsustainable, costly and pose a threat to the environment. Nanoparticles are gaining a reputation in the field [...] Read more.

Deterioration of soils over the years has led to a decline in crop yields and nutritional qualities, resulting from the oversupply of conventional fertilizers, which are unsustainable, costly and pose a threat to the environment. Nanoparticles are gaining a reputation in the field of agriculture for the remediation of soil degradation in a sustainable way. Recently, they have been recognized as potential fertilizers with properties that make them more absorbable and readily available for plant use than their bulk counterpart. However, there is less literature elaborating on the use of nanoparticles as agro-inputs for crop nutrition and protection. This review, therefore, provides insights into the application of nanoscaled nutrient elements such as silver, zinc, copper, iron, titanium, magnesium and calcium as fertilizers. In addition, the review explains the need for utilizing green synthesized nanomaterials as one of the ways to palliate the use of environmentally toxic chemicals in the cropping system and discusses the various benefits of nanoparticles, ranging from plant growth stimulation to defence against pathogens. Full article

(This article belongs to the Special Issue Surface Chemical Modification II)

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15 pages, 24810 KiB

Open AccessArticle

Experimental Study on Fatigue Performance of Welded Hollow Spherical Joints Reinforced by CFRP

by Yutong Duan, Honggang Lei and Shihong Jin

Coatings 2022, 12(10), 1585; https://doi.org/10.3390/coatings12101585 - 20 Oct 2022

Cited by 2 | Viewed by 1160

Abstract

The risk of fatigue failure of welded hollow spherical joints (WHSJs) under alternating loads increases due to the inherent defects, the disrepair, and the demand for tonnage upgrades, of suspension cranes. The finite element analysis results revealed that the ranking of the stress [...] Read more.

The risk of fatigue failure of welded hollow spherical joints (WHSJs) under alternating loads increases due to the inherent defects, the disrepair, and the demand for tonnage upgrades, of suspension cranes. The finite element analysis results revealed that the ranking of the stress concentration factor at the WHSJ was as follows: weld toe in steel tube of tube–ball connection weld > weld toe in steel tube of tube–endplate connection weld > weld toe in sphere of tube–ball connection weld > weld toe in plate of tube–endplate connection weld. Moreover, the peak stress at the weld of the tube–sphere connection was reduced by 32.93% after CFRP bonding reinforcement, which was beneficial for improving the fatigue performance. In this study, 16 full-scale specimens of Q235B WHSJs were tested by an MTS fatigue testing machine to study the strengthening effect of CFRP on the fatigue performance. It was found that the fatigue fracture of WHSJs was transferred from the tube–sphere connection weld to the tube–endplate connection after CFRP reinforcement. According to the fitted S-N curves, the fatigue strength could be increased by 13.26%–18.19% when the cycle number increased from 10,000 to 5,000,000. Full article

(This article belongs to the Special Issue Mechanical, Corrosive and Tribological Degradation of Metal Coatings and Modified Metallic Surfaces)

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23 pages, 10923 KiB

Open AccessArticle

Cyclic Performance of Prefabricated Shear Wall Connected to Columns by Rectangular Concrete-Filled Steel Tube Keys

by Zhijun Zhou, Ming Li, Qian Wu, Shuang Yuan and Li Zhang

Coatings 2022, 12(10), 1584; https://doi.org/10.3390/coatings12101584 - 19 Oct 2022

Viewed by 2777

Abstract

A prefabricated frame–shear wall structure is a major structure in an assembled building. To find a method of connecting a shear wall and columns that can both reduce the amount of wet work required and maintain adequate stiffness, we propose connecting the shear [...] Read more.

A prefabricated frame–shear wall structure is a major structure in an assembled building. To find a method of connecting a shear wall and columns that can both reduce the amount of wet work required and maintain adequate stiffness, we propose connecting the shear wall to the vertical frame using rectangular concrete-filled steel tube keys (RCFSTKs). Static tests of a cast-in-place frame–shear wall structure without keys and a prefabricated structure with RCFSTKs were conducted to compare their seismic performance. The feasibility of the new method was analyzed. Finite element models were then set up to determine if plain concrete blocks between RCFSTKs could be removed and to identify the influence of different parameters on the cyclic performance of the assembled structure. The results show that the use of RCFSTK is practical. Compared with a dimensionally similar cast-in-place shear wall–column construction, a prefabricated shear wall connected to columns by RCFSTKs has a fuller hysteresis curve, better ductility, slightly higher energy dissipation, and slightly slower degradation of stiffness and bearing capacity. The removal of inter-key concrete blocks significantly reduces bearing capacity and initial stiffness. The cyclic performance of the assembled structure is primarily influenced by the number of RCFSTKs, the thickness of the steel tube key wall, and the axial compression ratio, with less effect from key unit height, steel strength, and concrete grade in RCFSTKs. Full article

(This article belongs to the Special Issue Current Research in Cement and Building Materials)

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12 pages, 3442 KiB

Open AccessFeature PaperArticle

Transparent Conductive Indium Zinc Oxide Films: Temperature and Oxygen Dependences of the Electrical and Optical Properties

by Akhmed K. Akhmedov, Eldar K. Murliev, Abil S. Asvarov, Arsen E. Muslimov and Vladimir M. Kanevsky

Coatings 2022, 12(10), 1583; https://doi.org/10.3390/coatings12101583 - 19 Oct 2022

Cited by 5 | Viewed by 2026

Abstract

Achieving high-efficiency optoelectronic devices often requires the development of high transparency in the extended range and high-conductivity materials, which can be ensured by the high mobility of charge carriers being used as the electrode. Among the candidate materials, transparent conductive indium zinc oxide [...] Read more.

Achieving high-efficiency optoelectronic devices often requires the development of high transparency in the extended range and high-conductivity materials, which can be ensured by the high mobility of charge carriers being used as the electrode. Among the candidate materials, transparent conductive indium zinc oxide (IZO) has attracted significant interest because of its superior electron mobility (5−60 cm²/V·s) and the thermal stability of its structure. In this study, the IZO films were deposited by the radio frequency magnetron sputtering of the IZO ceramic target (containing 10 wt.% ZnO) by varying the two variables of the substrate temperature and the oxygen content in the working gas. Here, the importance of the deposition of the IZO films at a low substrate temperature, not exceeding 100 °C, in order to get the minimum values of the film resistivity is revealed. At a substrate temperature of 100 °C, the film deposited in pure argon demonstrated a minimum resistance of 3.4 × 10⁻⁴ Ω·cm. Despite the fact that, with the addition of O₂ in the working gas, an increase in resistivity was observed, the IZO film that deposited under 0.4% O₂ content demonstrated the highest mobility (μ = 35 cm²/V·s at ρ = 6.0 × 10⁻⁴ Ω·cm) and enhanced transparency in the visible (VIS, 400−800 nm) and near-infrared (NIR, 800−1250 nm) ranges (T_VIS ≥ 77% and T_NIR ≥ 76%). At an oxygen content above 0.4%, a significant deterioration in electrical properties and a decrease in optical characteristics were observed. SEM and XRD studies of the microstructure of the IZO films allowed the clarification of the effect of both the substrate temperature and the oxygen content on the functional characteristics of the transparent conducting IZO films. Full article

(This article belongs to the Special Issue Optical Properties of Crystals and Thin Films)

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9 pages, 277 KiB

Open AccessArticle

On the Validity of a Linearity Axiom in Diffusion and Heat Transfer

by Raj Kumar Arya, Devyani Thapliyal, George D. Verros, Neetu Singh, Dhananjay Singh, Rahul Kumar, Rajesh Kumar Srivastava and Anurag Kumar Tiwari

Coatings 2022, 12(10), 1582; https://doi.org/10.3390/coatings12101582 - 19 Oct 2022

Viewed by 1447

Abstract

In this work, the linearity axiom of irreversible thermodynamics for diffusion and heat transfer has been re-examined. It is shown that this axiom is compatible with the entropy production invariance principle with respect to a reference quantity for diffusion and heat transfer in [...] Read more.

In this work, the linearity axiom of irreversible thermodynamics for diffusion and heat transfer has been re-examined. It is shown that this axiom is compatible with the entropy production invariance principle with respect to a reference quantity for diffusion and heat transfer in the Euclidean space. Moreover, the underlying relations of the other principles of irreversible thermodynamics for multi-component diffusion and heat transfer, such as the quasi-equilibrium and the Onsager reciprocal relations (ORR) with the entropy production invariance, are re-examined. It was shown that the linearity principle postulates for diffusion and heat transfer and could be directly derived from the entropy production invariance axiom. It is believed that this work could not only be used for the drying of polymer coatings but also for pedagogical purposes. It may also be generalized; thus, leading to a generalized framework for irreversible thermodynamics. Full article

(This article belongs to the Special Issue Science and Technology of Glassy Coatings)

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21 pages, 5464 KiB

Open AccessArticle

Downstream Electric Field Effects during Film Deposition with a Radio Frequency Plasma and Observations of Carbon Reduction

by Kenneth Scott Alexander Butcher, Vasil Georgiev, Dimka Georgieva, Rositsa Gergova, Penka Terziyska and Peter W. Binsted

Coatings 2022, 12(10), 1581; https://doi.org/10.3390/coatings12101581 - 19 Oct 2022

Cited by 2 | Viewed by 1675

Abstract

Strong electric fields are generated by radio frequency (RF) plasma sources, and though the RF portion is too high a frequency for ions to react, the direct current (DC) portion of these fields has been shown to cause the atomic migration of metals, [...] Read more.

Strong electric fields are generated by radio frequency (RF) plasma sources, and though the RF portion is too high a frequency for ions to react, the direct current (DC) portion of these fields has been shown to cause the atomic migration of metals, which can influence film morphology even downstream of the plasma where ionized plasma species are absent. In particular, we have observed the growth of nanopillars due to metal atoms migrating toward the positive field of the remote plasma. A biased grid placed between the plasma and the substrate can shield the substrate from these fields so that, when grounded, smooth films can be grown to a root mean square roughness of less than 1 nm. Positively biasing the grid returns the growth of nanocolumns. Interestingly, negatively biasing the grid significantly reduced the carbon and hydrocarbon content of gallium nitride films grown at a low temperature (~660 °C) using a nitrogen plasma, as observed using secondary ion mass spectroscopy (SIMS) and optical absorption measurements. The films also showed a notable improvement in conductivity and visible appearance. Full article

(This article belongs to the Special Issue Plasma Processing and Thin Film Deposition)

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11 pages, 2186 KiB

Open AccessArticle

Effect of Ascorbic Acid Combined with Modified Atmosphere Packaging for Browning of Fresh-Cut Eggplant

by Sarengaowa, Liying Wang, Yumeng Liu, Chunmiao Yang, Ke Feng and Wenzhong Hu

Coatings 2022, 12(10), 1580; https://doi.org/10.3390/coatings12101580 - 19 Oct 2022

Cited by 4 | Viewed by 1645

Abstract

The growing demand for fresh-cut products has led to an increasing interest in the study of enhancing the quality of ready-to-eat products. Eggplants are consumed as fresh-cut vegetables, which represent an increasing consumption rate. To extend the shelf life of the product, combination [...] Read more.

The growing demand for fresh-cut products has led to an increasing interest in the study of enhancing the quality of ready-to-eat products. Eggplants are consumed as fresh-cut vegetables, which represent an increasing consumption rate. To extend the shelf life of the product, combination treatments have been proposed to inhibit the browning index (BI). Moreover, the storage temperature (4, 16, 25 °C), the concentration of ascorbic acid (AA) (1, 2, 3, and 4 g/L), and modified atmosphere packaging (MAP) (MAP-1, O₂: 80 Kpa + CO₂: 0 Kpa; MAP-2, O₂: 5 Kpa + CO₂: 15 Kpa; MAP-3, O₂: 10 Kpa + CO₂: 10 Kpa; MAP-4, O₂: 15 Kpa + CO₂: 5 Kpa; MAP-5, O₂: 0 Kpa + CO₂: 80 Kpa) are screened through the BI of fresh-cut eggplant. Then, the effect of AA combined with MAP on the BI, phenolic content, and polyphenol oxidase (PPO) of fresh-cut eggplants is investigated over four days. In particular, two different areas of fresh-cut eggplant with seed and without seed were chosen to measure the BI. The result shows that the proper temperature (16 °C) maintains the BI of fresh-cut eggplant with seed during two days through screening. The screening of AA demonstrates that AA of 2 g/L is the better concentration to protect the color of fresh-cut eggplant with seed and without seed. AA of 2 g/L shows lower BI for fresh-cut eggplant with seed and without seed in MAP-2, MAP-3, MAP-4. The combination of AA (2 g/L) and MAP-2 significantly inhibited the browning of fresh-cut eggplants with seed. The application of AA (2 g/L) combined with MAP-2 inhibits the PPO and total phenol content activity over two and three days. Taken together, using AA combined with MAP may constitute a potential approach for maintaining the quality and inhibiting the browning of fresh-cut eggplants. Full article

(This article belongs to the Special Issue Advanced Edible Films and Coatings for Food Packaging)

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29 pages, 8146 KiB

Open AccessArticle

Gum Acacia- and Gum Tragacanth-Coated Silver Nanoparticles: Synthesis, Physiological Stability, In-Vitro, Ex-Vivo and In-Vivo Activity Evaluations

by Mohammad Javed Ansari, Najeeb Ur Rehman, Elmoatasim Ibnouf, Ahmed Alalaiwe, Majid Ahmad Ganaie and Ameeduzzafar Zafar

Coatings 2022, 12(10), 1579; https://doi.org/10.3390/coatings12101579 - 19 Oct 2022

Cited by 3 | Viewed by 1811

Abstract

The current research article presents development, characterization, stability, antimicrobial activity, antispasmodic activity and antidiarrheal activity of silver nanoparticles synthesized and stabilized by polymeric coating of gum tragacanth solution. The nanoparticles were developed by a chemical reduction of silver nitrate. The reducing sugars and [...] Read more.

The current research article presents development, characterization, stability, antimicrobial activity, antispasmodic activity and antidiarrheal activity of silver nanoparticles synthesized and stabilized by polymeric coating of gum tragacanth solution. The nanoparticles were developed by a chemical reduction of silver nitrate. The reducing sugars and polysaccharides-based natural polymers such as gum acacia, gum tragacanth, alginates and cellulose derivatives were investigated as both reducing agents and stabilizers of silver nanoparticles. Influence of the molar concentration of silver nitrate, type and concentration of reducing agent on the formation and stability of silver nanoparticles have been investigated in detail. The stability or aggregation behavior of silver nanoparticles when diluted with simulated gastric fluid, simulated intestinal fluid and phosphate buffer saline were investigated to understand the influence of biological fluids on the stability of silver nanoparticles. SNPs in basic buffers were found to be more stable compared to those in acidic buffers. Silver nanoparticles were characterized by UV absorption spectrometry, particle size and zeta potential analyzer, FTIR spectroscopy, differential scanning calorimetry, X-ray diffraction and atomic force microscopy. SNPs were found spherical within 2.5–4 nm as per atomic force microscopic studies. The silver nanoparticles developed from gum tragacanth were better and more stable than those produced by gum acacia. The smaller particle size, low polydispersity index and high zeta potential resulted in silver nanosuspensions stable over a period of six months. The silver nanoparticles were found to exhibit significant antimicrobial, antispasmodic and antidiarrheal activities. Full article

(This article belongs to the Section Bioactive Coatings and Biointerfaces)

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21 pages, 7791 KiB

Open AccessArticle

Compressibility and Rarefaction Effects on Particle Dynamics and Heat Transfer in Aerosol Deposition Process

by Bahareh Farahani, Mehdi Jadidi and Sara Moghtadernejad

Coatings 2022, 12(10), 1578; https://doi.org/10.3390/coatings12101578 - 19 Oct 2022

Cited by 1 | Viewed by 1538

Abstract

The aerosol deposition (AD) method is an emerging coating technique to create a dense ceramic or metal layer on a substrate through the kinetic impaction and cumulative deposition of ultrafine solid particles under near-vacuum conditions. Prediction of the particles’ impact velocity and temperature [...] Read more.

The aerosol deposition (AD) method is an emerging coating technique to create a dense ceramic or metal layer on a substrate through the kinetic impaction and cumulative deposition of ultrafine solid particles under near-vacuum conditions. Prediction of the particles’ impact velocity and temperature during the AD process is crucial in enhancing the coating quality. In the present work, a two-way coupled Eulerian-Lagrangian model is developed for an AD system equipped with a converging-barrel nozzle to simulate the supersonic gas flow, particle in-flight behavior, as well as particle conditions upon impact on a flat substrate. The focus of the current study is to understand the effects of compressibility and rarefaction on particle velocity and temperature during the AD process. The effects of compressibility and rarefaction can be assessed using the Mach and Knudsen numbers. Therefore, different models for the drag coefficient and the heat transfer coefficient that take into account the Knudsen, Mach, and Reynolds number effects are implemented into the computational fluid dynamics (CFD) models. The results show that compressibility and rarefaction have significant influence on the particle temperature and velocity. As the particle size reduces, the effects of compressibility and rarefaction become more important. Full article

(This article belongs to the Section Surface Characterization, Deposition and Modification)

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14 pages, 2328 KiB

Open AccessArticle

Proteolysis of β-Lactoglobulin Assisted by High Hydrostatic Pressure Treatment for Development of Polysaccharides-Peptides Based Coatings and Films

by Yang Fei, Zhennai Yang, Sobia Niazi, Gang Chen, Muhammad Adnan Nasir, Imran Mahmood Khan, Abdur Rehman, Rana Muhammad Aadil, Monica Trif and Viorica Coşier

Coatings 2022, 12(10), 1577; https://doi.org/10.3390/coatings12101577 - 18 Oct 2022

Cited by 2 | Viewed by 1361

Abstract

Peptides usually have many bioactive functions. The variety of peptide binding and the modularity of the components allow for their application to additional tissues and materials; hence broadening the range of possible coatings and films. β-lactoglobulin (b-LG) forms spherical microgels or can [...] Read more.

Peptides usually have many bioactive functions. The variety of peptide binding and the modularity of the components allow for their application to additional tissues and materials; hence broadening the range of possible coatings and films. β-lactoglobulin (b-LG) forms spherical microgels or can be used in the formation of coated particles, with the core formed by aggregated b-LG and the coat by polysaccharides. The enzymatic proteolysis of b-LG assisted by high hydrostatic pressure (HHP) treatment was studied. Pretreatment of HHP enhanced the hydrolysis degree (DH) of b-LG. The highest value of DH without pretreatment was 24.81% at 400 MPa, which increased to 27.53% at 200 MPa with pretreatment, suggesting a difference in the DH of b-LG caused by the processing strategy of HHP. Molecular simulation suggested that the flexible regions of b-LG, e.g., Leu140-Ala142 and Asp33-Arg40, might contribute to enzymatic proteolysis. The b-LG hydrolysate exhibited the highest capacity of scavenging free DPPH and OH radicals at 200 MPa. In addition, the 1–2 kDa and 500–1000 Da peptides fractions significantly increased from 10.53% and 9.78% (under 0.1 MPa) to 12.37% and 14.95% under 200 MPa, respectively. The higher yield of short peptides under HHP contributed to the antioxidant capacity of b-LG hydrolysates. Enzymatic hydrolysis also largely reduced the immunoreactivity of b-LG, which is of high importance in the practical application of b-LG in the field of coatings and films in regard to biocompatibility. Hydrolysis of b-LG assisted by high-pressure treatment showed promising potential in the preparation of bioactive peptides for further development of polysaccharide-peptide-based coatings and films. Full article

(This article belongs to the Special Issue Renewable Resources in Films and Coatings Technologies: Part I: Polysaccharides – Gums and Starch)

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15 pages, 4432 KiB

Open AccessArticle

Effect of Working Pressure on Tribological Properties of Ce-Ti/MoS₂ Coatings Using Magnetron Sputter

by Changling Tian, Haichao Cai and Yujun Xue

Coatings 2022, 12(10), 1576; https://doi.org/10.3390/coatings12101576 - 18 Oct 2022

Cited by 1 | Viewed by 1200

Abstract

In preparing MoS₂-based coatings by magnetron sputtering, the working pressure of the vacuum chamber directly affects the number and kinetic energy of sputtering particles, which causes a difference in coatings structure and performance. In this paper, MoS₂ composite coatings with [...] Read more.

In preparing MoS₂-based coatings by magnetron sputtering, the working pressure of the vacuum chamber directly affects the number and kinetic energy of sputtering particles, which causes a difference in coatings structure and performance. In this paper, MoS₂ composite coatings with Ce and Ti binary doping were prepared by unbalanced magnetron sputtering technology, and the variation of composition, structure, and tribological properties of Ce-Ti/MoS₂ coatings under different working pressures was studied. The results demonstrated that Ce and Ti doping improves pure MoS₂ coatings. The Ce-Ti/MoS₂ coatings reached the hardness of 9.02 GPa and the friction coefficient of 0.065 when working pressure was at 0.6 Pa. It was also observed that the deposition efficiency and wear rate reached the optimal value at 0.9 Pa. With the increase of working pressure, the columnar structure of the coating was coarse due to the change of kinetic energy and quantity of particles in the chamber. The intensity of the MoS₂ (002) diffraction peak decreased, which eventually led to a poor lubrication effect and aggravated wear. This study provides technical guidance for preparing metal-doped MoS₂ composite coatings with excellent mechanical and tribological properties. Full article

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