Coatings

18 pages, 3656 KiB

Open AccessArticle

Dynamic Fracture Analysis of Functional Gradient Material Coating Based on the Peridynamic Method

by Yu Zhang, Zhanqi Cheng and Hu Feng

Coatings 2019, 9(1), 62; https://doi.org/10.3390/coatings9010062 - 21 Jan 2019

Cited by 10 | Viewed by 4595

Functional gradient materials (FGMs) have tremendous potential due to their characteristic advantage of asymptotic continuous variation of their properties. When an FGM is used as a coating material, damage and failure of the interface with the substrate component can be effectively inhibited. In [...] Read more.

Functional gradient materials (FGMs) have tremendous potential due to their characteristic advantage of asymptotic continuous variation of their properties. When an FGM is used as a coating material, damage and failure of the interface with the substrate component can be effectively inhibited. In order to study the dynamic crack propagation in FGM coatings, a new method, peridynamics (PD), was used in the present study to simulate dynamic fractures of FGM coatings bonded to a homogeneous substrate under dynamic loading. The bond-based PD theory was employed to study crack propagation and branching in the FGM coating. The influences of the coating gradient pattern, loading, and the geometry and size of the structure on crack curving and propagation under impact loading were investigated. The numerical results show that different forms of the elastic modulus of graded material, the geometry of the structure, and the loading conditions have considerate effects on crack propagation in FGM coatings, but a specific form of elastic modulus had a limited effect on the dynamic fracture of FGM coating. Full article

(This article belongs to the Special Issue Functionally Graded Nanocomposite Surfaces)

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14 pages, 3278 KiB

Open AccessArticle

High-Performance Adhesives Based on Maleic Anhydride-g-EPDM Rubbers and Polybutene for Laminating Cast Polypropylene Film and Aluminum Foil

by Sang-Hyub Lee, Se-Woo Yang, Eun-Suk Park, Ji-Young Hwang and Dai-Soo Lee

Coatings 2019, 9(1), 61; https://doi.org/10.3390/coatings9010061 - 21 Jan 2019

Cited by 13 | Viewed by 7864

Abstract

The adhesion between aluminum (Al) foil and cast polypropylene (CPP) film laminated with mixtures of amorphous- and crystalline-maleic anhydride-grafted ethylene-propylene-diene monomer (MAH-g-EPDM) rubbers and highly reactive polybutene (HRPB) as the adhesives was investigated. Specifically, the HRPB was used as an adhesion promoter of [...] Read more.

The adhesion between aluminum (Al) foil and cast polypropylene (CPP) film laminated with mixtures of amorphous- and crystalline-maleic anhydride-grafted ethylene-propylene-diene monomer (MAH-g-EPDM) rubbers and highly reactive polybutene (HRPB) as the adhesives was investigated. Specifically, the HRPB was used as an adhesion promoter of the MAH-g-EPDM rubbers and CPP as well as a compatibilizer of two kinds of MAH-g-EPDM rubbers having limited miscibility. To introduce strong chemical bonds between the MAH-g-EPDM rubbers and Al foil, the surface of Al foil was treated with 3-aminopropyl triethoxysilane (APTES). The weak adhesion between Al foil and MAH-g-EPDM rubbers was improved by imidization between the amine groups (–NH₂) of APTES and the maleic anhydride groups (MAH) of MAH-g-EPDM rubbers. The effects of the composition of adhesives, tempering time and adhesive thickness were also studied to optimize the adhesion of the CPP/Al foil laminates. We concluded that MAH-g-EPDM rubber based adhesives containing HRPB can be applied for the lamination of Al foil and CPP films to satisfy the requirements of high-performance packaging materials for various purposes. Full article

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Graphical abstract

24 pages, 6985 KiB

Open AccessArticle

Properties of Nitrogen/Silicon Doped Vertically Oriented Graphene Produced by ICP CVD Roll-to-Roll Technology

by Petr Rozel, Darya Radziuk, Lubov Mikhnavets, Evgenij Khokhlov, Vladimir Shiripov, Iva Matolínová, Vladimír Matolín, Alexander Basaev, Nikolay Kargin and Vladimir Labunov

Coatings 2019, 9(1), 60; https://doi.org/10.3390/coatings9010060 - 19 Jan 2019

Cited by 10 | Viewed by 5558

Abstract

Simultaneous mass production of high quality vertically oriented graphene nanostructures and doping them by using an inductively coupled plasma chemical vapor deposition (ICP CVD) is a technological problem because little is understood about their growth mechanism over enlarged surfaces. We introduce a new [...] Read more.

Simultaneous mass production of high quality vertically oriented graphene nanostructures and doping them by using an inductively coupled plasma chemical vapor deposition (ICP CVD) is a technological problem because little is understood about their growth mechanism over enlarged surfaces. We introduce a new method that combines the ICP CVD with roll-to-roll technology to enable the in-situ preparation of vertically oriented graphene by using propane as a precursor gas and nitrogen or silicon as dopants. This new technology enables preparation of vertically oriented graphene with distinct morphology and composition on a moving copper foil substrate at a lower cost. The technological parameters such as deposition time (1–30 min), gas partial pressure, composition of the gas mixture (propane, argon, nitrogen or silane), heating treatment (1–60 min) and temperature (350–500 °C) were varied to reveal the nanostructure growth, the evolution of its morphology and heteroatom’s intercalation by nitrogen or silicon. Unique nanostructures were examined by FE-SEM microscopy, Raman spectroscopy and energy dispersive X-Ray scattering techniques. The undoped and nitrogen- or silicon-doped nanostructures can be prepared with the full area coverage of the copper substrate on industrially manufactured surface defects. Longer deposition time (30 min, 450 °C) causes carbon amorphization and an increased fraction of sp³-hybridized carbon, leading to enlargement of vertically oriented carbonaceous nanostructures and growth of pillars. Full article

(This article belongs to the Special Issue Graphene-Based Composite Films)

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12 pages, 7180 KiB

Open AccessArticle

Effect of TiO₂ Sol and PTFE Emulsion on Properties of Cu–Sn Antiwear and Friction Reduction Coatings

by Lixia Ying, Zhen Fu, Ke Wu, Chunxi Wu, Tengfei Zhu, Yue Xie and Guixiang Wang

Coatings 2019, 9(1), 59; https://doi.org/10.3390/coatings9010059 - 19 Jan 2019

Cited by 12 | Viewed by 4404

Abstract

The aim of this paper is to obtain Cu–Sn composite coatings incorporated with PTFE and TiO₂ particles, which have superior antiwear and friction reduction properties. Electrodeposition was carried out in a pyrophosphate electrolyte, and the electrochemical behavior of the plating solutions was [...] Read more.

The aim of this paper is to obtain Cu–Sn composite coatings incorporated with PTFE and TiO₂ particles, which have superior antiwear and friction reduction properties. Electrodeposition was carried out in a pyrophosphate electrolyte, and the electrochemical behavior of the plating solutions was estimated. PTFE emulsion and TiO₂ sol were prepared and used, of which the average particle sizes were less than 283 and 158 nm, respectively. Then, four different types of coatings, Cu–Sn, Cu–Sn–TiO₂, Cu–Sn–PTFE and Cu–Sn–PTFE–TiO_2, were electroplated with a pulsed power supply. Their microstructure, composition, microhardness, corrosion resistance and tribological properties were then analyzed and compared in detail. The results show that both PTFE and TiO₂ are able to improve coating structure and corrosion resistance, while they have different effects on hardness and tribological properties. However, the presence of both PTFE and TiO₂ in the deposited coating leads to a lower friction coefficient of 0.1 and higher wear and corrosion resistance. Full article

(This article belongs to the Special Issue Tribology and Surface Engineering)

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16 pages, 474 KiB

Open AccessEditorial

Acknowledgement to Reviewers of Coatings in 2018

by Coatings Editorial Office

Coatings 2019, 9(1), 58; https://doi.org/10.3390/coatings9010058 - 18 Jan 2019

Viewed by 3516

Abstract

Rigorous peer-review is the cornerstone of high-quality academic publishing [...] Full article

21 pages, 6492 KiB

Open AccessArticle

Experimental Analysis of the Influence of Factors Acting on the Layer Thickness Formed by Anodic Oxidation of Aluminium

by Miroslav Gombár, Alena Vagaská, Marta Harničárová, Jan Valíček, Milena Kušnerová, Andrej Czán and Ján Kmec

Coatings 2019, 9(1), 57; https://doi.org/10.3390/coatings9010057 - 18 Jan 2019

Cited by 12 | Viewed by 4071

Abstract

The current practice in the field of anodic oxidation of aluminium and its alloys is based mainly on a set of partial empirical experiences of technologists obtained during surface treatment. The aim of the presented paper is deeper and more complex identification of [...] Read more.

The current practice in the field of anodic oxidation of aluminium and its alloys is based mainly on a set of partial empirical experiences of technologists obtained during surface treatment. The aim of the presented paper is deeper and more complex identification of the influence of chemical and technological factors acting during the anodic oxidation process especially on the thickness of the formed surface layer by the electrolysis method in a sulfuric acid solution. The current density was selected as the basic criterion for verification evaluation and analysis of experimentally obtained data, in accordance with Faraday’s laws. For current densities of 1 to 5 A·dm⁻², the synergy of significant influence factors was identified, and mathematical and statistical models were then developed to predict the thickness of the surface layer with a relative accuracy of up to 10%. The presented paper does not only focus on the observation of the thickness of the surface layer desired by the customer, but also on the monitoring of this thickness in relation to the overall layer thickness of the coating. Full article

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12 pages, 14272 KiB

Open AccessArticle

Rapid Electrodeposition of Fe–Ni Alloy Foils from Chloride Baths Containing Trivalent Iron Ions

by Changwei Su, Linfu Zhao, Liang Tian, Bixia Wen, Mingwu Xiang, Wei Bai and Junming Guo

Coatings 2019, 9(1), 56; https://doi.org/10.3390/coatings9010056 - 17 Jan 2019

Cited by 7 | Viewed by 3763

Abstract

This work presents the rapid electrodeposition of Fe–Ni alloy foils from chloride baths containing trivalent iron ions at a low pH (<0.0). The effect of the concentration of Ni²⁺ ions on the content, surface morphology, crystal structure, and tensile property of Fe–Ni [...] Read more.

This work presents the rapid electrodeposition of Fe–Ni alloy foils from chloride baths containing trivalent iron ions at a low pH (<0.0). The effect of the concentration of Ni²⁺ ions on the content, surface morphology, crystal structure, and tensile property of Fe–Ni alloys is studied in detail. The results show that the co-deposition of Fe and Ni is controlled by the adsorption of divalent nickel species at low current density and the ionic diffusion at high current density. The current density of preparing smooth and flexible Fe–Ni alloy foils is increased by increasing the concentration of Ni²⁺ ions, consequently the deposition rate of Fe–Ni alloy foils is increased. For example, at 0.6 M Ni²⁺ ions, the current density can be applied at 50 A·dm⁻², along with a high deposition rate of ~288 μm·h⁻¹. Full article

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18 pages, 8793 KiB

Open AccessArticle

Corrosion Behavior Evaluation of Coated Steel Using Fiber Bragg Grating Sensors

by Fodan Deng, Ying Huang and Fardad Azarmi

Coatings 2019, 9(1), 55; https://doi.org/10.3390/coatings9010055 - 17 Jan 2019

Cited by 14 | Viewed by 4783

Abstract

Coatings, either soft or hard, are commonly used to protect steel against corrosion for longer service life. With coatings, assessing the corrosion behavior and status of the substrate is challenging without destructive analysis. In this paper, fiber Bragg (FBG) grating sensors were proposed [...] Read more.

Coatings, either soft or hard, are commonly used to protect steel against corrosion for longer service life. With coatings, assessing the corrosion behavior and status of the substrate is challenging without destructive analysis. In this paper, fiber Bragg (FBG) grating sensors were proposed to nondestructively evaluate the corrosion behavior of steel coated with two popular coatings, including the polymeric and wire arc sprayed Al-Zn coating. Laboratory accelerated corrosion tests demonstrated that the embedded FBG sensors inside both the soft and hard coatings can effectively quantify the corrosion rate, monitor the corrosion progress, and detect the coating damages and crack propagation of coated steel in real time. The laboratory electrochemical corrosion test on the wire arc sprayed Al-Zn coating validated the proposed embedded FBG sensor method with a good agreement in comparison. The proposed sensing platform provides an alternative nondestructive real-time corrosion assessment approach for coated steel in the field. Full article

(This article belongs to the Special Issue Advanced Coatings for Corrosion Protection in Extreme Environments)

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22 pages, 7180 KiB

Open AccessEditor’s ChoiceArticle

Pulsed Laser Deposited Biocompatible Lithium-Doped Hydroxyapatite Coatings with Antimicrobial Activity

by Liviu Duta, Mariana Carmen Chifiriuc, Gianina Popescu-Pelin, Coralia Bleotu, Gratiela (Pircalabioru) Gradisteanu, Mihai Anastasescu, Alexandru Achim and Andrei Popescu

Coatings 2019, 9(1), 54; https://doi.org/10.3390/coatings9010054 - 17 Jan 2019

Cited by 16 | Viewed by 4686

Abstract

Simple and lithium-doped biological-origin hydroxyapatite layers were synthesized by Pulsed Laser Deposition technique on medical grade Ti substrates. Cytotoxic effects of lithium addition and the biocompatibility of obtained coatings were assessed using three cell lines of human origin (new initiated dermal fibroblasts, immortalized [...] Read more.

Simple and lithium-doped biological-origin hydroxyapatite layers were synthesized by Pulsed Laser Deposition technique on medical grade Ti substrates. Cytotoxic effects of lithium addition and the biocompatibility of obtained coatings were assessed using three cell lines of human origin (new initiated dermal fibroblasts, immortalized keratinocytes HaCaT, and MG-63 osteosarcoma). Antimicrobial properties of obtained coatings were assessed on two strains (i.e., Staphylococcus aureus and Candida albicans), belonging to species representative for the etiology of medical devices biofilm-associated infections. Our findings suggest that synthesized lithium-doped coatings exhibited low cytotoxicity on human osteosarcoma and skin cells and therefore, an excellent biocompatibility, correlated with a long-lasting anti-staphylococcal and -fungal biofilm activity. Along with low fabrication costs generated by sustainable resources, these biological-derived materials demonstrate their promising potential for future prospective solutions—viable alternatives to commercially available biomimetic HA implants—for the fabrication of a new generation of implant coatings. Full article

(This article belongs to the Special Issue Ion-Substituted Calcium Phosphates Coatings)

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6 pages, 2227 KiB

Open AccessArticle

Structure, Mechanical and Optical Properties of Silicon-Rich Al–Si–N Films Prepared by High Power Impulse Magnetron Sputtering

by Sergei Zenkin, Fedor Konusov, Aleksandr Lauk, Denis Zelentsov and Stanislav Demchenko

Coatings 2019, 9(1), 53; https://doi.org/10.3390/coatings9010053 - 17 Jan 2019

Cited by 5 | Viewed by 3205

Abstract

This article reports on the influence of the sputtering parameters (discharge voltage, average target power density) of a high power impulse magnetron discharge (HiPIMS) on the structure, mechanical and optical properties of silicon-rich Al–Si–N films. We show that with the change of a [...] Read more.

This article reports on the influence of the sputtering parameters (discharge voltage, average target power density) of a high power impulse magnetron discharge (HiPIMS) on the structure, mechanical and optical properties of silicon-rich Al–Si–N films. We show that with the change of a discharge target power density in the range of 30–120 W/cm², the hardness of the sputtered Al–Si–N films nonlinearly changes in the range of 22–29 GPa, while the concentration of the absorption centers changes in the range of 10¹⁸–10²⁰/cm³. The optical spectra of the HiPIMS sputtered films are completely different from the Al–Si–N films prepared by a direct current magnetron sputtering, with an absence of “monoenergetic” optical absorption centers, which are attributed to point defects. Full article

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15 pages, 11496 KiB

Open AccessArticle

Investigation of Using Sol-Gel Technology for Corrosion Protection Coating Systems Incorporating Colours and Inhibitors

by Wenjin Yan, Wee Kit Ong, Linda Yongling Wu and Sudesh L. Wijesinghe

Coatings 2019, 9(1), 52; https://doi.org/10.3390/coatings9010052 - 16 Jan 2019

Cited by 6 | Viewed by 4714

Abstract

Corrosion protection coatings need frequent developments to cater to different challenges arising from users. In addition to a long lasting corrosion protection, aesthetic requirements and multi-functional properties by the same coating system are prominent demands to be considered. Productivity is another vital factor [...] Read more.

Corrosion protection coatings need frequent developments to cater to different challenges arising from users. In addition to a long lasting corrosion protection, aesthetic requirements and multi-functional properties by the same coating system are prominent demands to be considered. Productivity is another vital factor to be considered, as there is a thriving demand from users to have more productive coating systems, such as a smaller number of layers in a system. Thus, attention to using different coating technologies is an essential step to fulfil these demands. This work investigates the use of sol-gel technology as a topcoat on a zinc rich primer to form a two-coat system. A colored sol-gel topcoat on a zinc primer was developed as a two-coat system to replace the current three or multi-coat systems to improve productivity while maintaining the sacrificial protective capability. The overall corrosion protection performance together with the color retaining capability was evaluated in this development. As another step forward, the development of sol-gel technology as a topcoat with additional inhibitive corrosion protection was investigated. Two corrosion inhibitors, namely molybdate and cerium(III), were loaded onto suitable inorganic oxide carriers and then incorporated into sol-gel coatings to provide an inhibitive protection other than the barrier protection. The corrosion performance of the coatings was evaluated using electrochemical impedance spectroscopy (EIS). Sol-gel coating with a cerium(III) system attained the highest impedance and proved to be the best candidate. The mechanical and physical properties of the coating systems are tested using international standard methods. Full article

(This article belongs to the Special Issue Recent Achievements in Corrosion Protection of Metals by Polymeric Coatings, Surface Pretreatments and Inhibitors)

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17 pages, 2391 KiB

Open AccessArticle

Thermal Analysis of a Functionally Graded Coating/Substrate System Using the Approximated Transfer Approach

by Hui Wang and Qinghua Qin

Coatings 2019, 9(1), 51; https://doi.org/10.3390/coatings9010051 - 16 Jan 2019

Cited by 4 | Viewed by 3164

Abstract

As a heterogeneous material, functionally graded material (FGM) behaves as continuously changed material properties in certain directions from one composition to another, and hence it has received much more attention for biomedical applications and thermal protections to achieve innovative functions that conventional homogeneous [...] Read more.

As a heterogeneous material, functionally graded material (FGM) behaves as continuously changed material properties in certain directions from one composition to another, and hence it has received much more attention for biomedical applications and thermal protections to achieve innovative functions that conventional homogeneous material cannot accomplish. However, due to the particularly small thickness ratio of coating to substrate in practice, the conventional mesh discretization of the coating region is inefficient. To simplify the meshing procedure and increase the efficiency of analysis, the approximated transfer algorithm based on the concept of finite difference is developed for transferring boundary conditions applied on the coating surface to the interface of coating and substrate. As a result, only the substrate with transferred convection boundary conditions needs to be solved numerically, i.e., by the fundamental-solution based hybrid finite element method (HFS-FEM) with high accuracy and feasible polygonal element construction, in which only integrals along the element boundary are evaluated because of the application of fundamental solutions of the problem as kernel functions of interior approximated fields. Finally, numerical experiments including the single-layered, multi-layered and functionally graded coatings are carried out to verify the accuracy and applicability of the present method. Full article

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14 pages, 39601 KiB

Open AccessArticle

Fabrication of Ni–Co–BN (h) Nanocomposite Coatings with Jet Electrodeposition in Different Pulse Parameters

by Hengzheng Li, Min Kang, Yin Zhang, Yuntong Liu, Meifu Jin, Nyambura Samuel Mbugua, Guang Zhu and Conghu Liu

Coatings 2019, 9(1), 50; https://doi.org/10.3390/coatings9010050 - 16 Jan 2019

Cited by 21 | Viewed by 4111

Abstract

In order to study the effects of pulse parameters on jet electrodeposition, Ni–Co–BN (h) nanocomposite coatings were prepared on the surface of steel C1045. The samples were analyzed and characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), laser [...] Read more.

In order to study the effects of pulse parameters on jet electrodeposition, Ni–Co–BN (h) nanocomposite coatings were prepared on the surface of steel C1045. The samples were analyzed and characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), laser scanning confocal microscopy (LSCM), microhardness tester, and electrochemical workstation. The experimental results showed that the contents of Co and BN (h) nanoparticles in the coatings changed with the variation of pulse parameters. When the pulse frequency was 4 kHz and the duty cycle was 0.7, their contents reached maxima of 27.34 wt % and 3.82 wt %, respectively. The XRD patterns of the coatings showed that the deposits had a face-centered cube (fcc) structure, and there was an obvious preferred orientation in (111) plane. With the increase in pulse parameters, the surface roughness of the coatings first decreased and then increased, with the minimum value obtained being 0.664 µm. The microhardness of the coatings first increased and then decreased with increase in pulse parameters. The maximum value of the microhardness reached 719.2 HV_0.05 when the pulse frequency was 4 kHz and the duty cycle was 0.7. In the electrochemical test, the potentiodynamic polarization curves of the coatings after immersion in 3.5 wt % NaCl solution showed the pulse parameters had an obvious effect on the corrosion resistance of the Ni–Co–BN (h) nanocamposite coatings. The corrosion current density and polarization resistance indicated that the coatings had better corrosion resistance when the pulse frequency was 4 kHz and duty cycle was 0.7. Full article

(This article belongs to the Special Issue Nanocomposite Coatings)

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8 pages, 2337 KiB

Open AccessEditor’s ChoiceArticle

Long-Term Reliability Evaluation of Silica-Based Coating with Antireflection Effect for Photovoltaic Modules

by Kensuke Nishioka, So Pyay Moe and Yasuyuki Ota

Coatings 2019, 9(1), 49; https://doi.org/10.3390/coatings9010049 - 15 Jan 2019

Cited by 7 | Viewed by 3890

Abstract

Not all sunlight irradiated on the surface of a photovoltaic (PV) module can reach the cells in the PV module. This loss reduces the conversion efficiency of the PV module. The main factors of this loss are the reflection and soiling on the [...] Read more.

Not all sunlight irradiated on the surface of a photovoltaic (PV) module can reach the cells in the PV module. This loss reduces the conversion efficiency of the PV module. The main factors of this loss are the reflection and soiling on the surface of the PV module. With this, it is effective to have both antireflection and antisoiling effects on the surface of PV modules. In this study, the antireflection and antisoiling effects along with the long-term reliability of the silica-based layer easily coated on PV modules were assessed. A silica-based layer with a controlled thickness and refractive index was coated on the surface of a Cu(In,Ga)Se₂ PV array. The array was exposed outdoors to assess its effects and reliability. As a result of the coating, the output of the PV array increased by 3.9%. The environment of the test site was relatively clean and the increase was considered to be a result of the antireflection effect. Moreover, it was observed that the effect of the coating was maintained without deterioration after 3.5 years. The coating was also applied to a silicon PV module and an effect similar to that of the CIGS PV module was observed in the silicon PV module. Full article

(This article belongs to the Special Issue Thin Film Solar Cells: Fabrication, Characterization and Applications)

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9 pages, 1210 KiB

Open AccessArticle

Strong and Reversible Adhesion of Interlocked 3D-Microarchitectures

by Minho Seong, Hyun-Ha Park, Insol Hwang and Hoon Eui Jeong

Coatings 2019, 9(1), 48; https://doi.org/10.3390/coatings9010048 - 15 Jan 2019

Cited by 9 | Viewed by 5073

Abstract

Diverse physical interlocking devices have recently been developed based on one-dimensional (1D), high-aspect-ratio inorganic and organic nanomaterials. Although these 1D nanomaterial-based interlocking devices can provide reliable and repeatable shear adhesion, their adhesion in the normal direction is typically very weak. In addition, the [...] Read more.

Diverse physical interlocking devices have recently been developed based on one-dimensional (1D), high-aspect-ratio inorganic and organic nanomaterials. Although these 1D nanomaterial-based interlocking devices can provide reliable and repeatable shear adhesion, their adhesion in the normal direction is typically very weak. In addition, the high-aspect-ratio, slender structures are mechanically less durable. In this study, we demonstrate a highly flexible and robust interlocking system that exhibits strong and reversible adhesion based on physical interlocking between three-dimensional (3D) microscale architectures. The 3D microstructures have protruding tips on their cylindrical stems, which enable tight mechanical binding between the microstructures. Based on the unique 3D architectures, the interlocking adhesives exhibit remarkable adhesion strengths in both the normal and shear directions. In addition, their adhesion is highly reversible due to the robust mechanical and structural stability of the microstructures. An analytical model is proposed to explain the measured adhesion behavior, which is in good agreement with the experimental results. Full article

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15 pages, 3495 KiB

Open AccessArticle

Formation Process of an LDHs Coating on Magnesium Alloy by a CO₂ Pressurization Method

by Xiaochen Zhang, Jiaoxiang Wang, Chunyan Zhang, Bin Liu, Peng Jiang, Yang Zhao, Bateer Buhe, Tao Zhang, Guozhe Meng and Fuhui Wang

Coatings 2019, 9(1), 47; https://doi.org/10.3390/coatings9010047 - 15 Jan 2019

Cited by 9 | Viewed by 3331

Abstract

The formation process of LDHs (layered double hydroxides) coating on magnesium alloy by the CO₂ pressurization method was studied. The micro-structure was observed by OM, SEM and GAXRD. The weighted gain curve, apparent activation energy, and CO₂ solubility curve were all [...] Read more.

The formation process of LDHs (layered double hydroxides) coating on magnesium alloy by the CO₂ pressurization method was studied. The micro-structure was observed by OM, SEM and GAXRD. The weighted gain curve, apparent activation energy, and CO₂ solubility curve were all calculated by equations. The potentiodynamic polarization curve, hydrogen evolution data, and immersion were analyzed by an electrochemical method. The results show that the LDHs coating was formed layer-by-layer. The formation positions were initially on the α-Mg phase, and then on the β-Mg₁₇Al₁₂ phase. It was found to be the most compact after 30 min. The LDHs coating began to appear to have severe cracks and holes over time. The formation process of the LDHs coating can be divided into three stages: a rapid growth stage (0–10 min), slow growth stage (10–20 min), and periodic growth stage (30 min, 1 h). The apparent activation energies in each of the three stages are 21.78, 31.86 and 34.92 kJ mol⁻¹, respectively. The LDHs coating has a compact micro-structure and better anti-corrosion at a pressure of 3 MPa, a temperature of 50 °C and a time of 30 min. The CO₂ pressurization promotes a formation reaction rate and achieves a high formation efficiency and good formation stability under the condition of zero pollution. Full article

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15 pages, 11489 KiB

Open AccessArticle

Preparation and Corrosion Resistance of ETEO Modified Graphene Oxide/Epoxy Resin Coating

by Chunling Zhang, Xueyan Dai, Yingnan Wang, Guoen Sun, Peihong Li, Lijie Qu, Yanlong Sui and Yanli Dou

Coatings 2019, 9(1), 46; https://doi.org/10.3390/coatings9010046 - 15 Jan 2019

Cited by 28 | Viewed by 6048

Abstract

Improving the corrosion resistance of epoxy resin coatings has become the focus of current research. This study focuses on synthesizing a functionalized silane coupling agent (2-(3,4-epoxycyclohexyl)ethyl triethoxysilane) to modify the surface of graphene oxide to address nanomaterial agglomeration and enhance the coating resistance [...] Read more.

Improving the corrosion resistance of epoxy resin coatings has become the focus of current research. This study focuses on synthesizing a functionalized silane coupling agent (2-(3,4-epoxycyclohexyl)ethyl triethoxysilane) to modify the surface of graphene oxide to address nanomaterial agglomeration and enhance the coating resistance of the epoxy resin coating to corrosion by filling the coating with functionalized graphene oxide. Functionalized graphene oxide and coatings filled with functionalized graphene oxide were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The corrosion performance of each coating was studied by electrochemical impedance spectroscopy and a salt spray test. Results showed that the incorporation of functionalized graphene oxide enhances the corrosion protection performance of the epoxy composite coating, and the composite coating exhibited the best anticorrosion performance when the amount of functionalized graphene oxide was 0.7 wt %. Full article

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

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12 pages, 6143 KiB

Open AccessArticle

Effect of Incorporating MoS₂ in Organic Coatings on the Corrosion Resistance of 316L Stainless Steel in a 3.5% NaCl Solution

by Min-Sung Hong, Yunjeong Park, Jung Gu Kim and Kyunghoon Kim

Coatings 2019, 9(1), 45; https://doi.org/10.3390/coatings9010045 - 15 Jan 2019

Cited by 29 | Viewed by 6774

Abstract

This study discusses a new coating method to protect 316L stainless steel (SS) from pitting corrosion in high chloride environments. The SS surface was coated using a simple, eco-friendly method, and sunflower oil (SunFO) was used as a base coating and binder for [...] Read more.

This study discusses a new coating method to protect 316L stainless steel (SS) from pitting corrosion in high chloride environments. The SS surface was coated using a simple, eco-friendly method, and sunflower oil (SunFO) was used as a base coating and binder for molybdenum disulfide (MoS₂). The coated surface was observed using scanning electron microscopy (SEM) with an energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). Corrosion behavior was examined by open-circuit potential (OCP) measurement and electrochemical impedance spectroscopy (EIS) in an 3.5% NaCl solution. The SunFO coating with MoS₂ showed the highest corrosion resistance and coating durability during the immersion time relative to the SunFO coating and bare 316L SS. The increased corrosion resistance is thought to be because of the interactions with the aggregations of the SunFO lamellar structure and MoS₂ in the coating film, which acted as a high order layer barrier providing protection from the metals to electrolytes. Full article

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8 pages, 2615 KiB

Open AccessArticle

Effects of Yttrium Doping on a-IGZO Thin Films for Use as a Channel Layer in Thin-Film Transistors

by Sanghyun Cho, Seohan Kim, Doyeong Kim, Moonsuk Yi, Junseok Byun and Pungkeun Song

Coatings 2019, 9(1), 44; https://doi.org/10.3390/coatings9010044 - 15 Jan 2019

Cited by 8 | Viewed by 4955

Abstract

Amorphous In−Ga−Zn−O (a-IGZO) has been studied as a channel layer in thin-film transistors (TFTs). To improve the bias-induced instability of a-IGZO TFTs, we introduced yttrium with high bond enthalpy by magnetron co-sputtering system. The Y-doped a-IGZO (a-IGZO:Y) films show relatively lower carrier concentration [...] Read more.

Amorphous In−Ga−Zn−O (a-IGZO) has been studied as a channel layer in thin-film transistors (TFTs). To improve the bias-induced instability of a-IGZO TFTs, we introduced yttrium with high bond enthalpy by magnetron co-sputtering system. The Y-doped a-IGZO (a-IGZO:Y) films show relatively lower carrier concentration and higher Hall mobility, which is due to the suppression of oxygen vacancies caused by Y doping. The a-IGZO:Y showed a relatively higher transmittance in the visible light region compared to non-doped IGZO, which could be due to the decrease of shallow defect levels caused by oxygen vacancy in the band gap. The a-IGZO without Y doping showed dramatic changes in electrical properties as times progressed (over 240 h); however, the a-IGZO:Y showed no significant changes. The a-IGZO:Y TFTs demonstrated a more stable driving mode as exhibited in the positive gate bias stress test even though the values of V_TH and SS were slightly degraded. Full article

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13 pages, 4930 KiB

Open AccessArticle

Influence of ALD Coating Layers on the Optical Properties of Nanoporous Alumina-Based Structures

by Ana L. Cuevas, María del Valle Martínez de Yuso, Víctor Vega, Ana Silvia González, Víctor M. Prida and Juana Benavente

Coatings 2019, 9(1), 43; https://doi.org/10.3390/coatings9010043 - 15 Jan 2019

Cited by 15 | Viewed by 5140

Abstract

Optical changes associated with the surface coating of different metal oxides and nanolayers by the ALD technique of a nanoporous alumina structure (NPAS) obtained by the two-step anodization method were analyzed. The NPASs were coated with: (i) a single layer (SiO₂ or [...] Read more.

Optical changes associated with the surface coating of different metal oxides and nanolayers by the ALD technique of a nanoporous alumina structure (NPAS) obtained by the two-step anodization method were analyzed. The NPASs were coated with: (i) a single layer (SiO₂ or TiO₂), and (ii) a double layer of SiO₂ plus Al₂O₃ or aluminum doped ZnO (AZO) to estimate the effect of surface layer coverage material, geometrical parameters (pore-size/porosity), and number of layers on light transmission/reflection. Chemical surface characterization of the different NPASs was carried out by analyzing XPS spectra, which allowed us to obtain an estimation of the coating layer homogeneity. Transmittance and spectroscopic ellipsometry measurements were analyzed in order to detect changes in characteristic optical parameters such as band gap, refractive index, and extinction coefficients associated with the material and the characteristics of the single or double coating layers. Full article

(This article belongs to the Collection Surface and Interface Science and Engineering for the Society of the Future)

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27 pages, 9601 KiB

Open AccessReview

A Review on Micropitting Studies of Steel Gears

by Huaiju Liu, Heli Liu, Caichao Zhu and Ye Zhou

Coatings 2019, 9(1), 42; https://doi.org/10.3390/coatings9010042 - 14 Jan 2019

Cited by 61 | Viewed by 13113

Abstract

With the mounting application of carburized or case-hardening gears and higher requirements of heavy-load, high-speed in mechanical systems such as wind turbines, helicopters, ships, etc., contact fatigue issues of gears are becoming more preponderant. Recently, significant improvements have been made on the gear [...] Read more.

With the mounting application of carburized or case-hardening gears and higher requirements of heavy-load, high-speed in mechanical systems such as wind turbines, helicopters, ships, etc., contact fatigue issues of gears are becoming more preponderant. Recently, significant improvements have been made on the gear manufacturing process to control subsurface-initiated failures, hence, gear surface-initiated damages, such as micropitting, should be given more attention. The diversity of the influence factors, including gear materials, surface topographies, lubrication properties, working conditions, etc., are necessary to be taken into account when analyzing gear micropitting behaviors. Although remarkable developments in micropitting studies have been achieved recently by many researchers and engineers on both theoretical and experimental fields, large amounts of investigations are yet to be further launched to thoroughly understand the micropitting mechanism. This work reviews recent relevant studies on the micropitting of steel gears, especially the competitive phenomenon that occurs among several contact fatigue failure modes when considering gear tooth surface wear evolution. Meanwhile, the corresponding recent research results about gear micropitting issues obtained by the authors are also displayed for more detailed explanations. Full article

(This article belongs to the Special Issue Tribology and Surface Engineering)

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14 pages, 6656 KiB

Open AccessArticle

Influence of the Obtaining Method on the Properties of Amorphous Aluminum Compounds

by Aliya N. Mukhamed'yarova, Oksana V. Nesterova, Kirill S. Boretsky, Juliya D. Skibina, Avgustina V. Boretskaya, Svetlana R. Egorova and Alexander A. Lamberov

Coatings 2019, 9(1), 41; https://doi.org/10.3390/coatings9010041 - 14 Jan 2019

Cited by 10 | Viewed by 4696

Abstract

Amorphous aluminum compounds are formed during the synthesis of the γ-Al₂O₃ catalyst precursor. Amorphous compounds influence on the alumina catalyst variously due to different physicochemical properties, which depend on the method of their preparation. In this research, the comparative analysis [...] Read more.

Amorphous aluminum compounds are formed during the synthesis of the γ-Al₂O₃ catalyst precursor. Amorphous compounds influence on the alumina catalyst variously due to different physicochemical properties, which depend on the method of their preparation. In this research, the comparative analysis of physicochemical properties of amorphous aluminum compounds that were obtained by the precipitation method, the thermal decomposition of aluminum nitrate, and alcoxide hydrolysis product were studied. It is the first time that a new method for calculating of quantitative phase composition of amorphous aluminum compounds using the X-ray powder diffraction, thermogravimetric and differential scanning calorimetry analysis, mass-spectrometry, and CHN-analysis was described. Properties of obtaining samples were studied using scanning electron microscopy, low-temperature nitrogen adsorption, and temperature programmed desorption of ammonium analyses. The methods of precipitation and thermal decomposition of aluminum nitrate allows for obtaining non-porous samples consisting of a mixture of amorphous phases (hydroxide and basic salt) that contain the metals impurities and have low acidity of the oxides obtained from them. The highly porous amorphous alumina formed by the thermal decomposition of the alcoxide hydrolysis product with the least amount of impurities and a high acidity of the surface was observed. Full article

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10 pages, 1819 KiB

Open AccessArticle

Silver Nanoparticle-Based Paper Packaging to Combat Black Anther Disease in Orchid Flowers

by Bang-on Nokkrut, Sawitree Pisuttipiched, Somwang Khantayanuwong and Buapan Puangsin

Coatings 2019, 9(1), 40; https://doi.org/10.3390/coatings9010040 - 14 Jan 2019

Cited by 9 | Viewed by 4423

Abstract

Metal nanoparticles have been reported to have a high antimicrobial activity against fungi, bacteria, and yeasts. In this study, we aimed to synthesize silver nanoparticles (AgNPs) using a chemical reduction method at 90 °C. The obtained AgNPs were used as an antifungal coating [...] Read more.

Metal nanoparticles have been reported to have a high antimicrobial activity against fungi, bacteria, and yeasts. In this study, we aimed to synthesize silver nanoparticles (AgNPs) using a chemical reduction method at 90 °C. The obtained AgNPs were used as an antifungal coating on packaging paper, to control the growth of Colletotrichum gloeosporioides in cut orchid flowers during the shipping process. The AgNPs were characterized by a UV-Vis spectroscopy and atomic force microscope (AFM). The results indicated that their shape was spherical and homogenous, with an average size of 47 nm. An AgNPs concentration of 20 and 50 particles per million (ppm), mixed with starch, was prepared as the coating solution. The paper coated with a concentration of 50 ppm exhibited a significant antifungal activity against C. gloeosporioides compared to 20 ppm. The coated paper had a higher water resistance and better mechanical properties compared to the uncoated paper. Additionally, we observed a significant reduction in the number of orchid inflorescence anthers, infected by C. gloeosporioides, when stored in the coated boxes. The current study demonstrates that paper boxes, coated with AgNPs, can be used in controlling the C. gloeosporioides infection during storage of cut orchid flowers. Full article

(This article belongs to the Special Issue Advances in Antimicrobial Coatings)

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16 pages, 3277 KiB

Open AccessArticle

Durability of Selected Transparent and Semi-Transparent Coatings on Siberian and European Larch during Artificial Weathering

by Kristýna Šimůnková, Eliška Oberhofnerová, Ladislav Reinprecht, Miloš Pánek, Milan Podlena and Irena Štěrbová

Coatings 2019, 9(1), 39; https://doi.org/10.3390/coatings9010039 - 14 Jan 2019

Cited by 6 | Viewed by 3658

Abstract

This paper compares the resistance of 20 commercial transparent and semi-transparent coatings applied to European and Siberian larch during artificial weathering in Xenotest. The change in gloss, colour, contact angle of wetting, resistance to Aspergillus niger and Penicillium brevicompactum moulds was evaluated, and [...] Read more.

This paper compares the resistance of 20 commercial transparent and semi-transparent coatings applied to European and Siberian larch during artificial weathering in Xenotest. The change in gloss, colour, contact angle of wetting, resistance to Aspergillus niger and Penicillium brevicompactum moulds was evaluated, and visual changes at the top surface of treated wood species were measured. Overall, the durability of coatings on European larch was higher than that on Siberian larch. The most durable of the tested coatings was a thin-film, i.e., semi-transparent oil-based film containing TiO₂ pigment and propiconazole fungicide. Of the transparent coatings, the most stable was a thick acrylic coating. Conversely, penetrating transparent oil systems had low colour stability and overall lifespan. Artificial weathering of all of the coatings resulted in a marked decrease in their resistance to moulds. Full article

(This article belongs to the Special Issue Additives and Pre-treatments to Enhance the Performance of Coatings on Wood)

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1 pages, 144 KiB

Open AccessErratum

Erratum: Lindner, M. and Schmid, M. Thickness Measurement Methods for Physical Vapor Deposited Aluminum Coatings in Packaging Applications: A Review. Coatings 2017, 7, 9

by Martina Lindner and Markus Schmid

Coatings 2019, 9(1), 38; https://doi.org/10.3390/coatings9010038 - 12 Jan 2019

Viewed by 2784

Abstract

The authors wish to make the following change to their published paper [...] Full article

(This article belongs to the Special Issue Advances in Coatings Characterization)

10 pages, 2537 KiB

Open AccessArticle

An Ambient Curable Coating Material Based on the Michael Addition Reaction of Acetoacetylated Castor Oil and Multifunctional Acrylate

by Tong Wang, Jianli Wang, Xianfeng He, Zhiyuan Cao, Dongdong Xu, Fei Gao, Jiang Zhong and Liang Shen

Coatings 2019, 9(1), 37; https://doi.org/10.3390/coatings9010037 - 12 Jan 2019

Cited by 19 | Viewed by 6049

Abstract

In this work a novel ambient curable coating was synthesized based on the Michael addition reaction of acetoacetylated castor oil and a multifunctional acrylate. In the research, we used hexamethylene diacrylate as crosslinker to optimize the reaction conditions and found that a ratio [...] Read more.

In this work a novel ambient curable coating was synthesized based on the Michael addition reaction of acetoacetylated castor oil and a multifunctional acrylate. In the research, we used hexamethylene diacrylate as crosslinker to optimize the reaction conditions and found that a ratio of acetoacetylated castor oil to acrylate groups of 1:1.5 and a catalyst (DBU) loading of 2 wt % provided an appropriate curing time. The acetoacetylated castor oil was characterized by ¹H NMR and ¹³C NMR spectroscopy and the obtained coating characterized by FTIR to confirm the functionalization reaction. The tensile strength, cross linking density, and thermal properties of the resulting thermosets were investigated by dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Results demonstrated that the glass transition temperatures, tensile strength, and thermal degradation were significantly improved with higher cross-linking density. Moreover, we prepared films with different multifunctional acrylate cross-linkers and found that with the increase of cross-linking density, the swelling of the film rate decreased. Overall, thermosets made from Michael crosslinking technology provided a highly bio-based coating system. Full article

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7 pages, 3437 KiB

Open AccessCommunication

Control of Polydimethylsiloxane Surface Hydrophobicity by Plasma Polymerized Hexamethyldisilazane Deposition

by Virginija Jankauskaitė, Pranas Narmontas and Algirdas Lazauskas

Coatings 2019, 9(1), 36; https://doi.org/10.3390/coatings9010036 - 11 Jan 2019

Cited by 30 | Viewed by 5464

Abstract

The properties of a polydimethylsiloxane (PDMS) surface were modified by a one-step deposition of plasma polymerized hexamethyldisilazane (pp-HMDS) by the arc discharge method. Scanning electron microscopy, atomic force microscopy, and Fourier-transform infrared spectroscopy analytical techniques were employed for morphological, structural, and chemical characterization [...] Read more.

The properties of a polydimethylsiloxane (PDMS) surface were modified by a one-step deposition of plasma polymerized hexamethyldisilazane (pp-HMDS) by the arc discharge method. Scanning electron microscopy, atomic force microscopy, and Fourier-transform infrared spectroscopy analytical techniques were employed for morphological, structural, and chemical characterization of the pp-HMDS modified PDMS surface. The changes in PDMS substrate wetting properties were evaluated by means of contact angle measurements. The unmodified PDMS surface is hydrophobic with a contact angle of 122°, while, after pp-HMDS film deposition, a dual-scale roughness PDMS surface with contact angle values as high as 170° was obtained. It was found that the value of the contact angle depends on the plasma processing time. Chemically, the pp-HMDS presents methyl moieties, rendering it hydrophobic and making it an attractive material for creating a superhydrophobic surface, and eliminating the need for complex chemical routes. The presented approach may open up new avenues in design and fabrication of superhydrophobic and flexible organosilicon materials with a self-cleaning function. Full article

(This article belongs to the Special Issue Advances in Organic and Polymeric Coatings )

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15 pages, 4074 KiB

Open AccessArticle

Relationship Processing–Composition–Structure–Resistivity of LaNiO₃ Thin Films Grown by Chemical Vapor Deposition Methods

by Sabina Kuprenaite, Vincent Astié, Samuel Margueron, Cyril Millon, Jean-Manuel Decams, Zita Saltyte, Pascal Boulet, Valentina Plausinaitiene, Adulfas Abrutis and Ausrine Bartasyte

Coatings 2019, 9(1), 35; https://doi.org/10.3390/coatings9010035 - 10 Jan 2019

Cited by 6 | Viewed by 4967

Abstract

Precision control of resistivity/conductivity of LaNiO₃ (LNO) films is essential for their integration as electrodes in the functional heterostructures. This becomes possible if the relationship between processing parameters–composition–structure–resistivity is determined. LaNiO₃ films were deposited by three different chemical vapor deposition methods [...] Read more.

Precision control of resistivity/conductivity of LaNiO₃ (LNO) films is essential for their integration as electrodes in the functional heterostructures. This becomes possible if the relationship between processing parameters–composition–structure–resistivity is determined. LaNiO₃ films were deposited by three different chemical vapor deposition methods using different precursor supply systems: direct liquid delivery, pulsed liquid injection, and aerosol generation. The possibilities to ameliorate the efficiency of precursor evaporation and of film growth were studied. The relationship between deposition conditions and composition was determined. Detailed analysis of the epitaxial growth of LNO films on cubic and trigonal substrates and the influence of the rhombohedral distortion on the microstructural quality was done. The resistivity of LaNiO₃ films, grown by chemical vapor deposition, was mainly defined by microstructural defects and La/Ni composition. The high epitaxial quality LaNiO₃/LaAlO₃ films with nearly stoichiometric La/Ni ratio presented low resistivity, which was very close to that of bulk LaNiO₃. Their annealing in oxygen atmosphere had little effect on the resistivity, which suggests a minor presence of oxygen vacancies in the as-grown films. Full article

(This article belongs to the Special Issue Chemical Vapor Deposition 2018)

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17 pages, 5662 KiB

Open AccessArticle

Finding the Additives Incorporation Moment in Hybrid Natural Pigments Synthesis to Improve Bioresin Properties

by Bàrbara Micó-Vicent, Jorge Jordán, Esther Perales, Francisco Miguel Martínez-Verdú and Francisco Cases

Coatings 2019, 9(1), 34; https://doi.org/10.3390/coatings9010034 - 9 Jan 2019

Cited by 16 | Viewed by 3967

Abstract

Interest in applications of natural dye applications has increased because of their antibacterial properties and the possibility of extracting them from nature and residues. Using nanoclays as hosts to reinforce natural dye properties has been successfully demonstrated. However, no one has attempted to [...] Read more.

Interest in applications of natural dye applications has increased because of their antibacterial properties and the possibility of extracting them from nature and residues. Using nanoclays as hosts to reinforce natural dye properties has been successfully demonstrated. However, no one has attempted to optimize the polymer matrix and hybrid pigment properties at the same time to ensure the best final properties for bio-composite applications. Using a statistical design for experiments, we propose the best combination of modifiers with the best nanoclay as the host of three natural dyes: chlorophyll, β-carotene, and betanine. Using the L9 Taguchi designs, we learned both the influence of the nanoclay structure, and the addition moment of surfactant, mordant salt, and silane modifiers. FTIR, XRD, DTG, integration sphere spectrophotometer, and UV-aging tests were used to characterize the hybrid pigments and epoxy bioresin composites. The degradation temperatures of the three natural dyes rose and the reinforcement of the stability of three natural dyes to UV–Vis radiation exposure was demonstrated, which avoided the migration of these dyes from bioresin to wet ribbing. Optimal results were obtained with hydrotalcite clay (calcined or not) by using surfactant and mordant before the natural dye, and before or after silane. Full article

(This article belongs to the Special Issue Binders, Pigments, Dyes and Additives)

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18 pages, 4946 KiB

Open AccessArticle

Hygroexpansion and Surface Roughness Cause Defects and Increase the Electrical Resistivity of Physical Vapor Deposited Aluminum Coatings on Paper

by Martina Lindner, Julia Heider, Matthias Reinelt and Horst-Christian Langowski

Coatings 2019, 9(1), 33; https://doi.org/10.3390/coatings9010033 - 8 Jan 2019

Cited by 3 | Viewed by 5082

Abstract

Aluminum coatings, which are applied by physical vapor deposition (PVD), have to be virtually defect-free in barrier applications for the packaging industry. When aluminum is applied to paper, hygroexpansion and substrate roughness can impair the aluminum coating. Neither effect is easy to detect [...] Read more.

Aluminum coatings, which are applied by physical vapor deposition (PVD), have to be virtually defect-free in barrier applications for the packaging industry. When aluminum is applied to paper, hygroexpansion and substrate roughness can impair the aluminum coating. Neither effect is easy to detect by microscopy, but both can manifest as an increase in electrical resistance. Here, we quantified the effect of substrate paper hygroexpansion and surface roughness on the effective resistivity ρ_EFF of aluminum coatings. The sheet resistance of aluminum coated onto four different rough paper surfaces was measured via eddy currents at different relative humidity (0%–95%). The mass of aluminum per unit area was determined by inductively-coupled plasma mass spectrometry (ICP–MS). We calculated ρ_EFF based on the measured resistance and aluminum mass per unit area, combined with a value for aluminum density from the literature. The substrate roughness was proportional to ρ_EFF. Relative humidity correlated with the moisture content of the paper substrate according to the Guggenheim, Anderson, and De Boer (GAB) equation, whereas the moisture content showed a linear correlation with hygroexpansion. At relative humidity of up to 50%, hygroexpansion was linearly correlated with the increase in ρ_EFF, which is related to the mechanical straining and deformation of aluminum. At higher humidity, aluminum started to crack first on rough substrates and later on smooth substrates. The increase in ρ_EFF was larger on rough substrates. The findings highlight the need for information about substrate roughness, humidity, and hygroexpansion when eddy current measurement results are compared, and will help to ensure that aluminum coatings, applied by PVD, are defect-free. Full article

(This article belongs to the Special Issue Advances in Flexible Films and Coatings)

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