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8 pages, 1768 KiB

Open AccessArticle

Reconstructed NiCo Alloy Enables High-Rate Ni-Zn Microbattery with High Capacity

by Yixue Duan, Gongchuan You, Zhe Zhu, Linfeng Lv, Xiaoqiao Liao, Xin He, Kai Yang, Ruiqi Song, Peng Tian and Liang He

Coatings 2023, 13(3), 603; https://doi.org/10.3390/coatings13030603 - 12 Mar 2023

Viewed by 1746

Abstract

Miniaturized powering devices with both sufficient capacity as well as fast charging capability are anticipated to support microelectronics with multi-functions. However, most reported miniaturized energy storage devices only display limited performances around capacity or rate performance, and it remains challenging to develop high-rate [...] Read more.

Miniaturized powering devices with both sufficient capacity as well as fast charging capability are anticipated to support microelectronics with multi-functions. However, most reported miniaturized energy storage devices only display limited performances around capacity or rate performance, and it remains challenging to develop high-rate microdevices with large capacities. Herein, a reconstructed NiCo alloy is proposed as a promising microcathode for a Ni-Zn microbattery with a high-rate performance and large capacity. With the reconstructed layer compactly adhered on the metal substrate, the activated NiCo alloy demonstrates an excellent conductivity close to metals. Meanwhile, the abundant alloying defect contributes to a relatively higher reconstruction depth up to 20 nm. Both the superior electron transport and the higher reaction depth facilitate the simultaneous excellent performance in the reaction rate and capacity. As a consequence, the microcathode achieves a large capacity up to 1.51 mAh cm⁻², as well as an excellent rate performance with a capacity retention of 82.9% when the current density is expanded to 100 mA cm⁻². More surprisingly, such excellent performance can shift towards the full Ni-Zn microbattery, and the fast-charging capability based on large capacity can stably maintain 7000 cycles. This unique strategy of reconstructed NiCo alloy microcathode provides a new direction for the construction of high-performance output units. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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11 pages, 3938 KiB

Open AccessArticle

Study of the Corrosion Mechanism of Iron-Based Amorphous Composite Coating with Alumina in Sulfate-Reducing Bacteria Solution

by Zhenhua Chu, Haonan Shi, Fa Xu, Jingxiang Xu, Xingwei Zheng, Fang Wang, Zheng Zhang and Qingsong Hu

Coatings 2022, 12(11), 1763; https://doi.org/10.3390/coatings12111763 - 17 Nov 2022

Cited by 3 | Viewed by 1574

Abstract

In this work, a composite coating composed of iron-based amorphous material and alumina mixed with 13 wt.% titanium oxide (AT13) ceramic was successfully fabricated by High Velocity Air-fuel Flame Spray (HVAF). The corrosion process of the composite coating in Sulfate-Reducing Bacteria (SRB) solution [...] Read more.

In this work, a composite coating composed of iron-based amorphous material and alumina mixed with 13 wt.% titanium oxide (AT13) ceramic was successfully fabricated by High Velocity Air-fuel Flame Spray (HVAF). The corrosion process of the composite coating in Sulfate-Reducing Bacteria (SRB) solution for 31 d was investigated by Electrochemical Impedance Spectroscopy (EIS). The corrosion morphologies and corrosion products were tested by X-ray photoelectron spectroscopy. The corrosion mechanism can be divided into two stages: microbial adhesion and biofilm failure. The microbial adhesion on the surface of the composite coating improved the formation of biofilm, which improved the corrosion resistance. On the other hand, the SRB metabolic process in the biofilm accelerated the formation of corrosion products, which resulted in the failure of the biofilm and thus the composite coating was re-exposed in the corrosion solution. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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16 pages, 5219 KiB

Open AccessArticle

Increasing the Life Span of Tools Applied in Cheese Cutting Machines via Appropriate Micro-Blasting

by Georgios Skordaris, Konstantinos Vogiatzis, Leonidas Kakalis, Ioannis Mirisidis, Vasiliki Paralidou and Soultana Paralidou

Coatings 2022, 12(9), 1343; https://doi.org/10.3390/coatings12091343 - 15 Sep 2022

Viewed by 1704

Abstract

The potential to increase the life span of tools applied in cheese cutting machines is of great importance, considering their cost and the risk of fragmented metallic parts of the tool being inserted into the cheese. Such tools are commonly manufactured using stainless [...] Read more.

The potential to increase the life span of tools applied in cheese cutting machines is of great importance, considering their cost and the risk of fragmented metallic parts of the tool being inserted into the cheese. Such tools are commonly manufactured using stainless steel 405 and are subjected to dynamic loads during their operation, leading to fatigue failure. An efficient method to improve the fatigue properties of such tools is the application of micro-blasting. In this work, for the first time, an experimental–analytical methodology was developed for determining optimum micro-blasting conditions and ascertaining a preventive replacement of the tool before its extensive fracture. This methodology is based on the construction of a pneumatic system for the precise cutting of cheese and simultaneous force measurements. Additionally, the entire cheese-cutting process is simulated by appropriate FEA modeling. According to the attained results, micro-blasting on steel tools significantly improves the resistance against dynamic loads, whilst the number of impacts that a tool can withstand until fatigue fracture is more than three times larger. Via the developed methodology, a preventive replacement of the tool can be conducted, avoiding the risk of a sudden tool failure. The proposed methodology can be applied to different tool geometries and materials. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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12 pages, 4819 KiB

Open AccessArticle

Fabrication and Characterization of P-Type Semiconducting Copper Oxide-Based Thin-Film Photoelectrodes for Solar Water Splitting

by Chih-Jui Chang, Chih-Wei Lai, Wei-Cheng Jiang, Yi-Syuan Li, Changsik Choi, Hsin-Chieh Yu, Shean-Jen Chen and YongMan Choi

Coatings 2022, 12(8), 1206; https://doi.org/10.3390/coatings12081206 - 17 Aug 2022

Cited by 8 | Viewed by 3210

Abstract

Solar light-driven hydrogen by photocatalytic water splitting over a semiconductor photoelectrode has been considered a promising green energy carrier. P-type semiconducting copper oxides (Cu₂O and CuO) have attracted remarkable attention as an efficient photocathode for photoelectrochemical (PEC) water splitting because of [...] Read more.

Solar light-driven hydrogen by photocatalytic water splitting over a semiconductor photoelectrode has been considered a promising green energy carrier. P-type semiconducting copper oxides (Cu₂O and CuO) have attracted remarkable attention as an efficient photocathode for photoelectrochemical (PEC) water splitting because of their high solar absorptivity and optical band gaps. In this study, CuO thin films were prepared using the sol-gel spin coating method to investigate the effects of aging time and layer dependency. Electrodeposition was also applied to fabricate Cu₂O thin films. Cu₂O thin films annealed at 300 °C are a hetero-phase system composed of Cu₂O and CuO, while those at 400 °C are fully oxidized to CuO. Thin films are characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM), ultraviolet-visible spectroscopy (UV-VIS), Fourier transform infrared spectroscopy (FTIR), spectroscopic ellipsometry (SE), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman microscopy. The hetero-phase thin films increase the photoconversion efficiency compared to Cu₂O. Fully oxidized thin films annealed at 400 °C exhibit a higher efficiency than the hetero-phase thin film. We also verified that CuO thin films fabricated using electrodeposition show slightly higher efficiency than the spin coating method. The highest photocurrent of 1.1 mA/cm² at 0.10 V versus RHE was measured for the fully oxidized CuO thin film under one-sun AM1.5G illumination. This study demonstrates a practical method to fabricate durable thin films with efficient optical and photocatalytic properties. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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29 pages, 19088 KiB

Open AccessArticle

Contribution to the Research and Development of Innovative Building Components with Embedded Energy-Active Elements

by Daniel Kalús, Daniela Koudelková, Veronika Mučková, Martin Sokol and Mária Kurčová

Coatings 2022, 12(7), 1021; https://doi.org/10.3390/coatings12071021 - 19 Jul 2022

Cited by 5 | Viewed by 1970

Abstract

The research described in this study focuses on the innovation and optimization of building envelope panels with integrated energy-active elements in the thermal barrier function. It is closely related to developing and implementing the prototype prefabricated house IDA I with combined building-energy systems [...] Read more.

The research described in this study focuses on the innovation and optimization of building envelope panels with integrated energy-active elements in the thermal barrier function. It is closely related to developing and implementing the prototype prefabricated house IDA I with combined building-energy systems using renewable energy sources. We were inspired by the patented ^®ISOMAX panel and system, which we have been researching and innovating for a long time. The thermal barrier has the function of eliminating heat loss/gain through the building envelope. By controlling the heat/cold transfer in the thermal barrier, it is possible to eliminate the thickness of the thermal insulation of the building envelope and thus achieve an equivalent thermal resistance of the building structure that is equal to the standard required value. The technical solution of the ISOMAX panel also brings, besides the use of the thermal barrier function, the function of heat/cold accumulation in the load-bearing part of the building envelope. Our research aimed to design and develop a panel for which the construction would be optimal in terms of thermal barrier operation and heat/cold accumulation. As the production panels in the lost formwork of expanded polystyrene (according to the patented system) proved to be too complicated and time consuming, and often showed shortcomings from a structural point of view, the next goal was to design a new, statically reliable panel construction with integrated energy-active elements and a time-saving, cost-effective, unified production directly in the panel factory. In order to develop and design an innovative panel with integrated energy-active elements, we analyzed the composition of the original panel and designed the composition of the innovative panel. We created mathematical–physical models of both panels and analyzed their energy potential. By induction and an analog form of formation, we designed the innovative panel. Based on the synthesis of the knowledge obtained from the scientific analysis and the transformation of this data, most of the building components and all the panels with integrated energy-active elements were manufactured directly in the prefabrication plant. Subsequently, the prototype of the prefabricated house IDA I was realized. The novelty of our innovative building envelope panel solution lies in the panel’s design, which has a heat loss/gain that is 2.6 times lower compared to the ISOMAX panel. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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25 pages, 3593 KiB

Open AccessArticle

Low Fluorinated Oligoamides for Use as Wood Protective Coating

by Yuqing Zhang, Laura Vespignani, Maria Grazia Balzano, Leonardo Bellandi, Mara Camaiti, Nadège Lubin-Germain and Antonella Salvini

Coatings 2022, 12(7), 927; https://doi.org/10.3390/coatings12070927 - 30 Jun 2022

Cited by 2 | Viewed by 3260

Abstract

New highly hydrophobic fluorinated oligoamides were synthesized and studied as materials for the protection of non-varnishable wooden artifacts. The new oligoamides were designed to achieve the best performance (including high chemical affinity to the wood material) and the lowest environmental impact. In order [...] Read more.

New highly hydrophobic fluorinated oligoamides were synthesized and studied as materials for the protection of non-varnishable wooden artifacts. The new oligoamides were designed to achieve the best performance (including high chemical affinity to the wood material) and the lowest environmental impact. In order to minimize the risk of bioaccumulation, short perfluoroalkyl side chains were reacted with oligoethylene L-tartaramide (ET), oligoethylene adipamide-L-tartaramide (ETA), oligoethylene succinamide-L-tartaramide (EST), oligoethylene succinamide (ES), and oligodiethylenetriamino-L-tartaramide (DT). Favorable reaction conditions were also adopted to obtain low molecular weight compounds characterized by non-film-forming properties and solubility or dispersibility in environmentally friendly organic solvents. Their behavior in terms of modification of the wood surface characteristics, such as wettability, moisture absorption, and color, was analyzed using a specific diagnostic protocol to rapidly obtain preliminary, but reliable, results for optimizing a future synthesis of new and tailored protectives. The influence of different monomer units on the reactivity, solubility, and hydrophobic properties of different oligoamides was compared showing ESF (contact angle 138.2°) and DF (132.2°) as the most effective products. The study of stability to photochemical degradation confirms ESF as promising protective agents for artefacts of historical and artistic interest in place of long-chain perfluoroalkyl substances (PFAS), products currently subject to restrictions on use. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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12 pages, 2452 KiB

Open AccessFeature PaperArticle

PPy-Modified Prussian Blue Cathode Materials for Low-Cost and Cycling-Stable Aqueous Zinc-Based Hybrid Battery

by Yushan Ruan, Lineng Chen, Lianmeng Cui and Qinyou An

Coatings 2022, 12(6), 779; https://doi.org/10.3390/coatings12060779 - 5 Jun 2022

Cited by 16 | Viewed by 3295

Abstract

Prussian blue analogs are promising cathode materials in aqueous ion batteries that have attracted increasing attention, but their low specific capacity and limited cycling stability remain to be further improved. Effective strategies to optimize the electrochemical performance of Prussian blue cathode materials are [...] Read more.

Prussian blue analogs are promising cathode materials in aqueous ion batteries that have attracted increasing attention, but their low specific capacity and limited cycling stability remain to be further improved. Effective strategies to optimize the electrochemical performance of Prussian blue cathode materials are the aspects of electrolyte and structure modification. In this work, Na₂MnFe(CN)₆@PPy nanocubes were prepared by a simple co-precipitation method with PPy coating. Compared with the uncoated electrode material, the discharged capacity of the Na₂MnFe(CN)₆@PPy cathode material is raised from 25.2 to 55.0 mAh g⁻¹ after 10 cycles in the Na-Zn hybrid electrolyte, while the capacity retention is improved from 63.5% to 86.5% after 150 cycles, indicating higher capacity and better stability. This work also investigates the electrochemical performances of Na₂MnFe(CN)₆@PPy cathode material in hybrid electrolyte of Li-Zn and K-Zn adjusted via different mixed ion solutions. The relevant results provide an innovative way to optimize advanced aqueous hybrid batteries from the perspective of cycling stability. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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11 pages, 3344 KiB

Open AccessArticle

Effects of Additive and Roasting Processes on Nitrogen Removal from Aluminum Dross

by Shuai-Shuai Lv, Yu Zhang, Hong-Jun Ni, Xing-Xing Wang, Wei-Yang Wu and Chun-Yu Lu

Coatings 2022, 12(6), 730; https://doi.org/10.3390/coatings12060730 - 25 May 2022

Cited by 10 | Viewed by 1703

Abstract

Taking high nitrogen aluminum dross as the research object, the effects of the additives sodium carbonate and cryolite and the roasting process on the denitrification effect of aluminum dross were studied. The principle of additive denitrification was studied by XRD, SEM and TG-DSC. [...] Read more.

Taking high nitrogen aluminum dross as the research object, the effects of the additives sodium carbonate and cryolite and the roasting process on the denitrification effect of aluminum dross were studied. The principle of additive denitrification was studied by XRD, SEM and TG-DSC. The experimental results show that sodium carbonate and cryolite can quickly reduce the content of aluminum nitride in aluminum dross. The optimum denitrification process parameters were also obtained simultaneously. When the mass ratio of cryolite to aluminum dross was 0.4, the roasting temperature was 900 °C, and the roasting time was 3 h, the denitrification degree could reach 96.19%. When the mass ratio of sodium carbonate to aluminum dross was 0.8, the roasting temperature was 1000 °C, and the roasting time was 4 h, the denitrification degree could reach 91.32%. This study provides a reference for the non-harmful treatment of high nitrogen aluminum dross. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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12 pages, 3317 KiB

Open AccessArticle

PLLA/Graphene Nanocomposites Membranes with Improved Biocompatibility and Mechanical Properties

by Yaoting He, Jiafei Yan, Xuzhao He, Wenjian Weng and Kui Cheng

Coatings 2022, 12(6), 718; https://doi.org/10.3390/coatings12060718 - 24 May 2022

Cited by 3 | Viewed by 1922

Abstract

In this work, nanocomposite membranes based on graphene and polylactide were evaluated for mechanical properties and biocompatibility. Single-layer graphene (SLG), graphene nanosheets (GNS), and poly L-lactic acid (PLLA) were prepared through layer-by-layer deposition and homogeneous mixing. The results revealed that PLLA/SLG nanocomposites and [...] Read more.

In this work, nanocomposite membranes based on graphene and polylactide were evaluated for mechanical properties and biocompatibility. Single-layer graphene (SLG), graphene nanosheets (GNS), and poly L-lactic acid (PLLA) were prepared through layer-by-layer deposition and homogeneous mixing. The results revealed that PLLA/SLG nanocomposites and PLLA/GNS nanocomposites could show enhanced mechanical properties and biocompatibility. The addition of a tiny amount of SLG significantly improved Young’s modulus and tensile strength of the PLLA matrix by 15.9% and 32.8% respectively, while the addition of the same mass ratio of GNS boosted the elongation at break of the PLLA matrix by 79.7%. These results were ascribed to the crystallinity and interfacial interaction differences resulting from graphene incorporation. Also, improved biocompatibility was observed with graphene incorporation. Such nanocomposites membranes showed a lot of potential as environment-friendly and biomedical materials. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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10 pages, 2928 KiB

Open AccessArticle

Solid-Solution-Based Metal Coating Enables Highly Reversible, Dendrite-Free Aluminum Anode

by Bo Hu, Kang Han, Chunhua Han, Lishan Geng, Ming Li, Ping Hu and Xuanpeng Wang

Coatings 2022, 12(5), 661; https://doi.org/10.3390/coatings12050661 - 12 May 2022

Cited by 2 | Viewed by 2406

Abstract

Aluminum-ion batteries have attracted great interest in the grid-scale energy storage field due to their good safety, low cost and the high abundance of Al. However, Al anodes suffer from severe dendrite growth, especially at high deposition rates. Here, we report a simple [...] Read more.

Aluminum-ion batteries have attracted great interest in the grid-scale energy storage field due to their good safety, low cost and the high abundance of Al. However, Al anodes suffer from severe dendrite growth, especially at high deposition rates. Here, we report a simple strategy for constructing a highly reversible, dendrite-free, Al-based anode through directly introducing a solid-solution-based metal coating to a Zn foil substrate. Compared with Cu foil substrates and bare Al, a Zn foil substrate shows a lower nucleation barrier of Al deposition due to the intrinsic, definite solubility between Al and Zn. During Al deposition, a thin, solid-solution alloy phase is first formed on the surface of the Zn foil substrate and then guides the parallel growth of flake-like Al on Zn substrate. The well-designed, Zn-coated Al (Zn@Al) anode can effectively inhibit dendrite growth and alleviate the corrosion of the Al anode. The fabricated Zn@Al–graphite battery exhibits a high specific capacity of 80 mAh·g⁻¹ and an ultra-long lifespan over 10,000 cycles at a high current density of 20 A·g⁻¹ in low-cost molten salt electrolyte. This work opens a new avenue for the development of stable Al anodes and can provide insights for other metal anode protection. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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20 pages, 10512 KiB

Open AccessArticle

Effect of EDM and Femtosecond-Laser Groove-Texture Collision Frequency on Tribological Properties of 0Cr17Ni7Al Stainless Steel

by Liguang Yang, Wensuo Ma, Fei Gao and Shiping Xi

Coatings 2022, 12(5), 611; https://doi.org/10.3390/coatings12050611 - 30 Apr 2022

Cited by 8 | Viewed by 2108

Abstract

Electric spark and femtosecond-laser surface texture are very effective in antifriction systems, but there are few applications and studies in dry friction. In this study, a groove texture was prepared on the surface of 0Cr17Ni7Al stainless steel via electric spark and femtosecond laser, [...] Read more.

Electric spark and femtosecond-laser surface texture are very effective in antifriction systems, but there are few applications and studies in dry friction. In this study, a groove texture was prepared on the surface of 0Cr17Ni7Al stainless steel via electric spark and femtosecond laser, respectively. The tribological properties of the two groove textures under different collision frequencies with the groove were studied under the condition of dry friction. The results show that the friction coefficient of the groove texture prepared by EDM and femtosecond laser is lower than that of the untextured surface. However, this does not mean that every groove-texture design will reduce wear rate. In addition, the groove texture seems to produce different tribological properties under different preparation methods. It is found that in the friction process of the same load, time and linear velocity, different collision frequencies will affect the friction and wear properties of the surface. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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18 pages, 5482 KiB

Open AccessArticle

Self-Cleaning Coatings for the Protection of Cementitious Materials: The Effect of Carbon Dot Content on the Enhancement of Catalytic Activity of TiO₂

by Charis Gryparis, Themis Krasoudaki and Pagona-Noni Maravelaki

Coatings 2022, 12(5), 587; https://doi.org/10.3390/coatings12050587 - 25 Apr 2022

Cited by 9 | Viewed by 3002

Abstract

The urgent demand for pollution protection of monuments and buildings forced the interest towards specific preservation methods, such as the application of photocatalytic coatings with self-cleaning and protective activity. TiO₂ photocatalysts without and with a variety of carbon dots loading (TC0, TC25–75) [...] Read more.

The urgent demand for pollution protection of monuments and buildings forced the interest towards specific preservation methods, such as the application of photocatalytic coatings with self-cleaning and protective activity. TiO₂ photocatalysts without and with a variety of carbon dots loading (TC0, TC25–75) were synthesized via a green, simple, low cost and large-scale hydrothermal method using citric acid, hydroxylamine and titanium isopropoxide (TTIP) and resulted in uniform anatase phase structures. In photocatalysis experiments, TC25 and TC50 composites with 1:3 and 1:1 mass ratio of C-dots solution to TTIP, respectively, showed the best degradation efficiency for methyl orange (MO) under UV-A light, simulated solar light and sunlight compared to TiO₂, commercial Au/TiO₂ (TAu) and catalysts with higher C-dot loading (TC62.5 and TC75). Treatment of cement mortars with a mixture of photocatalyst and a consolidant (FX-C) provided self-cleaning activity under UV-A and visible light. This study produced a variety of new, durable, heavy metal-free C-dots/TiO₂ photocatalysts that operate well under outdoor weather conditions, evidencing the C-dot dosage-dependent performance. For the building protection against pollution, nanostructured photocatalytic films were proposed with consolidation and self-cleaning ability under solar irradiation, deriving from combined protective silica-based agents and TiO₂ photocatalysts free or with low C-dot content. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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13 pages, 2343 KiB

Open AccessArticle

Effects of Hydrolysis Parameters on AlN Content in Aluminum Dross and Multivariate Nonlinear Regression Analysis

by Shuaishuai Lv, Hongjun Ni, Xingxing Wang, Wei Ni and Weiyang Wu

Coatings 2022, 12(5), 552; https://doi.org/10.3390/coatings12050552 - 19 Apr 2022

Cited by 6 | Viewed by 2792

Abstract

Aluminum dross, as a hazardous waste product, causes harm to the environment and humans, since the AlN it contains chemically reacts with water to produce ammonia. In the present study, a formula for modifying the AlN content in aluminum dross is proposed for [...] Read more.

Aluminum dross, as a hazardous waste product, causes harm to the environment and humans, since the AlN it contains chemically reacts with water to produce ammonia. In the present study, a formula for modifying the AlN content in aluminum dross is proposed for the first time, by investigating the components of aluminum dross and changes in their respective contents during the hydrolysis process. Meanwhile, the effects of such hydrolysis parameters as time, temperature, and rotational speed on the hydrolysis rate of aluminum dross are explored. Furthermore, regression analysis is performed on the hydrolysis parameters and objective functions. The results show that as the reaction time increases, the variation in AlN content in aluminum dross decelerates gradually after modification. The hydrolysis rate is the fastest in the initial 4 h, which essentially stagnates after 20 h. The rise in temperature can significantly accelerate the AlN hydrolysis in aluminum dross, while the rotational speed has a non-obvious effect on the hydrolysis rate of AlN in aluminum dross. Regression analysis and secondary simplification are performed on the hydrolysis parameters and the modified AlN content, revealing that the relative error between the theoretical and experimental values is ≤ ±9.34%. The findings of this study have certain guiding significance for predicting and controlling modified AlN content in aluminum dross during hydrolysis. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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12 pages, 6909 KiB

Open AccessArticle

A Novel SERS Substrate Based on Discarded Oyster Shells for Rapid Detection of Organophosphorus Pesticide

by Chi-Yu Chu, Pei-Ying Lin, Jun-Sian Li, Rajendranath Kirankumar, Chen-Yu Tsai, Nan-Fu Chen, Zhi-Hong Wen and Shuchen Hsieh

Coatings 2022, 12(4), 506; https://doi.org/10.3390/coatings12040506 - 8 Apr 2022

Cited by 5 | Viewed by 2178

Abstract

Over the past few years, the concern for green chemistry and sustainable development has risen dramatically. Researchers make an effort to find solutions to difficult challenges using green chemical processes. In this study, we use oyster shells as a green chemical source to [...] Read more.

Over the past few years, the concern for green chemistry and sustainable development has risen dramatically. Researchers make an effort to find solutions to difficult challenges using green chemical processes. In this study, we use oyster shells as a green chemical source to prepare calcium oxide nanoparticles (CaO-NPs). Transmission electron microscopy (TEM) results showed the CaO-NPs morphology, which was spherical in shape, 40 ± 5 nm in diameter, with uniform dispersion. We further prepared silver/polydopamine/calcium-oxide (Ag/PDA/CaO) nanocomposites as the surface-enhanced Raman scattering (SERS) substrates and evaluated their enhancement effect using the methyl parathion pesticide. The effective SERS detection limit of this method is 0.9 nM methyl parathion, which is much lower than the safety limits set by the Collaborative International Pesticides Analytical Council for insecticide in fruits. This novel green material is an excellent SERS substrate for future applications and meets the goal of green chemistry and sustainable development. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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11 pages, 3908 KiB

Open AccessArticle

Polytetrafluoroethylene Modified Nafion Membranes by Magnetron Sputtering for Vanadium Redox Flow Batteries

by Jun Su, Jiaye Ye, Zhenyu Qin and Lidong Sun

Coatings 2022, 12(3), 378; https://doi.org/10.3390/coatings12030378 - 14 Mar 2022

Cited by 4 | Viewed by 2729

Abstract

Commercial Nafion membranes have been widely used for vanadium redox flow batteries (VRFB) but with relatively low ion selectivity. A chemical method is commonly employed to modify the organic membranes, whereas physical approaches are rarely reported in view of less compatibility with the [...] Read more.

Commercial Nafion membranes have been widely used for vanadium redox flow batteries (VRFB) but with relatively low ion selectivity. A chemical method is commonly employed to modify the organic membranes, whereas physical approaches are rarely reported in view of less compatibility with the organic species. In this study, an ultrathin polytetrafluoroethylene (PTFE) film of less than 30 nm is deposited onto the Nafion substrates by radio frequency magnetron sputtering to form PTFE@Nafion composite membranes. The PTFE layer of hydrophobic and inert feature enhances the dimensional stability and the ion selectivity of the Nafion membranes. The VRFB single cell with an optimized composite membrane exhibits a better self-discharge property than that of the Nafion 212 (i.e., 201.2 vs. 18.6 h), due to a higher ion selectivity (i.e., 21.191 × 10⁴ vs. 11.054 × 10⁴ S min cm^–3). The composite membranes also show better discharge capacity retention than the Nafion 212 over the entire 100 cycles. The results indicate that the magnetron sputtering is an alternative and feasible route to tailor the organic membranes via surface modification and functionalization. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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12 pages, 1906 KiB

Open AccessArticle

A Novel Method for Calcium Carbonate Deposition in Wood That Increases Carbon Dioxide Concentration and Fire Resistance

by Vicente Hernandez, Romina Romero, Sebastián Arias and David Contreras

Coatings 2022, 12(1), 72; https://doi.org/10.3390/coatings12010072 - 7 Jan 2022

Cited by 4 | Viewed by 3517

Abstract

In this study, a novel method for calcium carbonate deposition in wood that increases carbon dioxide concentration and fire resistance is proposed. The method promoted the mineralization of radiata pine wood microstructure with calcium carbonate by using a process consisting in the vacuum [...] Read more.

In this study, a novel method for calcium carbonate deposition in wood that increases carbon dioxide concentration and fire resistance is proposed. The method promoted the mineralization of radiata pine wood microstructure with calcium carbonate by using a process consisting in the vacuum impregnation of wood with a calcium chloride aqueous solution and the subsequent sequential diffusion of gaseous ammonium and carbon dioxide. In the most favorable conditions, the method yielded a weight gain of about 20 wt.% due to mineralization, which implied the accumulation of 0.467 mmol·g⁻¹ of carbon dioxide in the microstructure of wood. In addition, a weight gain of about 8% was sufficient to provide fire resistance to a level similar to that achieved by a commercially available fire-retardant treatment. The feasibility of retaining carbon dioxide directly inside the wood microstructure can be advantageous for developing wood products with enhanced environmental characteristics. This method can be a potential alternative for users seeking materials that could be effective at supporting a full sustainable development. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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10 pages, 2916 KiB

Open AccessArticle

Formulation of Non-Fired Bricks Made from Secondary Aluminum Ash

by Hongjun Ni, Weiyang Wu, Shuaishuai Lv, Xingxing Wang and Weijia Tang

Coatings 2022, 12(1), 2; https://doi.org/10.3390/coatings12010002 - 21 Dec 2021

Cited by 13 | Viewed by 3002

Abstract

The secondary aluminum ash is the black slag left after the primary aluminum ash is extracted from the metal aluminum. To address the environmental pollution and resource waste caused by the accumulation and landfill of aluminum ash, this study fabricated non-fired bricks by [...] Read more.

The secondary aluminum ash is the black slag left after the primary aluminum ash is extracted from the metal aluminum. To address the environmental pollution and resource waste caused by the accumulation and landfill of aluminum ash, this study fabricated non-fired bricks by using secondary aluminum ash as the principal raw material, which was supplemented by cement, slaked lime, gypsum and engineering sand. The effects of mix proportions of various admixtures on the mechanical properties of non-fired bricks were investigated, and on this basis, the hydration mechanism was analyzed. The results showed that the mix proportions were 68.3% aluminum ash, 11.4% cement, 6.4% slaked lime, 4.2% gypsum and 9.7% engineering sand. The compressive strength of the fabricated bricks reached 22.19 MPa, and their quality indicators were in line with the MU20 requirements for Non-fired Rubbish Gangue Bricks. Evident hydration reaction occurred inside the non-fired bricks, with main products being calcium silicate hydrate (CSH), calcium aluminate hydrate (CAH) and ettringite (AFt). Besides, a dense structure was formed, which enhanced the brick strength. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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26 pages, 3377 KiB

Open AccessArticle

Optical Characterization of H-Free a-Si Layers Grown by rf-Magnetron Sputtering by Inverse Synthesis Using Matlab: Tauc–Lorentz–Urbach Parameterization

by Emilio Márquez, Juan J. Ruíz-Pérez, Manuel Ballester, Almudena P. Márquez, Eduardo Blanco, Dorian Minkov, Susana M. Fernández Ruano and Elias Saugar

Coatings 2021, 11(11), 1324; https://doi.org/10.3390/coatings11111324 - 29 Oct 2021

Cited by 10 | Viewed by 2616

Abstract

Several, nearly-1-µ

m

-thick, pure, unhydrogenated amorphous-silicon (a-Si) thin layers were grown at high rates by non-equilibrium rf-magnetron Ar-plasma sputtering (RFMS) onto room-temperature low-cost glass substrates. A new approach is employed for the optical characterization of the thin-layer samples, which is [...] Read more.

Several, nearly-1-µ

m

-thick, pure, unhydrogenated amorphous-silicon (a-Si) thin layers were grown at high rates by non-equilibrium rf-magnetron Ar-plasma sputtering (RFMS) onto room-temperature low-cost glass substrates. A new approach is employed for the optical characterization of the thin-layer samples, which is based on some new formulae for the normal-incidence transmission of such a samples and on the adoption of the inverse-synthesis method, by using a devised Matlab GUI environment. The so-far existing limiting value of the thickness-non-uniformity parameter,

Δ d

, when optically characterizing wedge-shaped layers, has been suppressed with the introduction of the appropriate corrections in the expression of transmittance. The optical responses of the H-free RFMS-a-Si thin films investigated, were successfully parameterized using a single, Kramers–Krönig (KK)-consistent, Tauc–Lorentz oscillator model, with the inclusion in the model of the Urbach tail (TLUC), in the present case of non-hydrogenated a-Si films. We have also employed the Wemple–DiDomenico (WDD) single-oscillator model to calculate the two WDD dispersion parameters, dispersion energy,

E_{d}

, and oscillator energy,

E_{so}

. The amorphous-to-crystalline mass-density ratio in the expression for

E_{d}

suggested by Wemple and DiDomenico is the key factor in understanding the refractive index behavior of the a-Si layers under study. The value of the porosity for the specific rf-magnetron sputtering deposition conditions employed in this work, with an Ar-pressure of ~4.4 Pa, is found to be approximately 21%. Additionally, it must be concluded that the adopted TLUC parameterization is highly accurate for the evaluation of the UV/visible/NIR transmittance measurements, on the H-free a-Si investigated. Finally, the performed experiments are needed to have more confidence of quick and accurate optical-characterizations techniques, in order to find new applications of a-Si layers in optics and optoelectronics. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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15 pages, 44907 KiB

Open AccessArticle

Deposition of Super-Hydrophobic Silver Film on Copper Substrate and Evaluation of Its Corrosion Properties

by Fani Stergioudi, Aikaterini Baxevani, Azarias Mavropoulos and Georgios Skordaris

Coatings 2021, 11(11), 1299; https://doi.org/10.3390/coatings11111299 - 27 Oct 2021

Cited by 6 | Viewed by 3108

Abstract

A simple and versatile chemical solution deposition process is reported to manipulate the wettability properties of copper sheets. The whole process has the advantage of being time-saving low cost and environment-friendly. An adherent silver coating was achieved under optimal conditions. Scanning electron microscopy [...] Read more.

A simple and versatile chemical solution deposition process is reported to manipulate the wettability properties of copper sheets. The whole process has the advantage of being time-saving low cost and environment-friendly. An adherent silver coating was achieved under optimal conditions. Scanning electron microscopy and X-ray diffraction were used to examine the silver film structure. A confocal microscope was used to record the 3D topography and assess the film roughness of the surface. A dual morphology was revealed, consisting of broad regions with feather-like structured morphologies and some areas with spherical morphologies. Such silver-coated copper samples exhibited a sufficiently stable coating with superhydrophobicity, having a maximum water contact angle of 152°, along with an oleophilic nature. The corrosion behavior of the produced hydrophobic copper under optimal conditions was evaluated by means of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) using a 3.5% NaCl solution. The corrosion protection mechanism was elucidated by the proposed equivalent circuits, indicating that the superhydrophobic silver coating acted as an effective barrier, separating the Cu substrate from the corrosive solution. The superhydrophobic coating demonstrated enhanced anti-corrosion properties against NaCl aqueous solution in relation to the copper substrate as indicated from both EIS and potentiodynamic polarization experiments. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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Graphical abstract

13 pages, 3892 KiB

Open AccessArticle

Assessment of Stone Protective Coatings with a Novel Eco-Friendly Encapsulated Biocide

by Martina Zuena, Ludovica Ruggiero, Giulia Caneva, Flavia Bartoli, Giancarlo Della Ventura, Maria Antonietta Ricci and Armida Sodo

Coatings 2021, 11(9), 1109; https://doi.org/10.3390/coatings11091109 - 14 Sep 2021

Cited by 9 | Viewed by 2577

Abstract

The conservation of stone monuments is a constant concern due to their continuous weathering, in which biofouling plays a relevant role. To enhance the effectiveness of biocidal treatments and to avoid environmental issues related to their possible toxicity, this research aims at formulating [...] Read more.

The conservation of stone monuments is a constant concern due to their continuous weathering, in which biofouling plays a relevant role. To enhance the effectiveness of biocidal treatments and to avoid environmental issues related to their possible toxicity, this research aims at formulating and characterizing a coating charged with an eco-friendly biocide and showing hydrophobic properties. For this purpose, zosteric sodium salt—a natural biocide product—has been encapsulated into two silica nanocontainers and dispersed into a tetraethoxysilane-based (TEOS) coating also containing TiO₂ nanoparticles. The coatings were applied on four different types of stone: brick, mortar, travertine, and Carrara marble. The effectiveness of the coating formulations and their compatibility concerning the properties of coated stones were assessed. The results showed that all coatings conferred a hydrophobic character to the substrate, as demonstrated by the increase of the static contact angle and the reduction in the capillary water absorption coefficient. The transmission of water vapor of the natural stones was preserved as well as their natural aspect. Furthermore, the coatings were homogeneously distributed on the surface and crack-free. Therefore, the protective capability of the coatings was successfully demonstrated. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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14 pages, 3828 KiB

Open AccessArticle

Preparation of Sintered Brick with Aluminum Dross and Optimization of Process Parameters

by Yu Zhang, Hongjun Ni, Shuaishuai Lv, Xingxing Wang, Songyuan Li and Jiaqiao Zhang

Coatings 2021, 11(9), 1039; https://doi.org/10.3390/coatings11091039 - 29 Aug 2021

Cited by 12 | Viewed by 3142

Abstract

Aluminum dross is produced in the process of industrial production and regeneration of aluminum. Currently, the main way to deal with aluminum dross is stacking and landfilling, which aggravates environmental pollution and resource waste. In order to find a green and environmental protection [...] Read more.

Aluminum dross is produced in the process of industrial production and regeneration of aluminum. Currently, the main way to deal with aluminum dross is stacking and landfilling, which aggravates environmental pollution and resource waste. In order to find a green and environmental protection method for the comprehensive utilization, the aluminum dross was used as raw materials to prepare sintered brick. Firstly, the raw material ratio, molding pressure and sintering process were determined by single factor test and orthogonal test, and the mechanism of obvious change of mechanical strength of sintered brick was studied by XRD and SEM. The experimental results show that, the optimal formula of sintered brick is 50% aluminum dross, 37.50% engineering soil and 12.50% coal gangue. The optimum process parameters are molding pressure 10 MPa, heating rate 8 °C/ min, sintering temperature 800 °C, holding time 60 min. The samples prepared under the above formula and process parameters present outstanding performance, and the compressive strength, flexural strength and water absorption rate are 16.21 MPa, 3.42 MPa and 17.12% respectively. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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16 pages, 8556 KiB

Open AccessArticle

Preparation and Characterization of PU/PET Matrix Gradient Composites with Microwave-Absorbing Function

by Wenyan Gu, Rong Zhan, Rui Li, Jiaxin Liu and Jiaqiao Zhang

Coatings 2021, 11(8), 982; https://doi.org/10.3390/coatings11080982 - 18 Aug 2021

Cited by 12 | Viewed by 2580

Abstract

In the field of microwave-absorbing materials, functional powder has always been the focus of research. In order to fabricate lightweight and flexible garment materials with microwave-absorbing function, the current work was carried out. Firstly, the general properties of polyurethane (PU) matrix composites reinforced [...] Read more.

In the field of microwave-absorbing materials, functional powder has always been the focus of research. In order to fabricate lightweight and flexible garment materials with microwave-absorbing function, the current work was carried out. Firstly, the general properties of polyurethane (PU) matrix composites reinforced with various microwave-absorbing powders were studied, and the carbon nanotubes (CNTs)/Fe₃O₄/PU film was proven to have the best general properties. Secondly, the needle-punched polyester (PET) nonwoven fabrics in 1 mm-thickness were impregnated into PU resin with the same composition of raw material as Fe₃O₄/CNTs/PU film, thereby the microwave-absorbing nonwovens with gradient structure were prepared. Moreover, the absorbing properties of the CNTs/Fe₃O₄/PU/PET gradient composites were tested and analyzed. Finally, the relationship between the mass ratio of CNTs and Fe₃O₄, and the microwave-absorbing properties was studied. The results show that the mass ratio of CNTs/Fe₃O₄ has a significant effect on the microwave-absorbing property of CNTs/Fe₃O₄/PU/PET. When the mass ratio of CNTs/Fe₃O₄ is 1:1, the prepared CNTs/Fe₃O₄/PU/PET gradient composite can achieve effective reflection loss in the range of more than 2 GHz in Ku-band (12–18 GHz), and the minimum reflection loss reaches −17.19 dB. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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10 pages, 2605 KiB

Open AccessArticle

Experimental Study Regarding the Possibility of Blocking the Diffusion of Sulfur at Casting-Mold Interface in Ductile Iron Castings

by Denisa Anca, Iuliana Stan, Mihai Chisamera, Iulian Riposan and Stelian Stan

Coatings 2021, 11(6), 673; https://doi.org/10.3390/coatings11060673 - 1 Jun 2021

Cited by 2 | Viewed by 2486

Abstract

The main objective of this work is to investigate the mechanism of sulfur diffusion from the mold (sand resin P-toluol sulfonic acid mold, sulfur-containing acid) in liquid cast iron in order to limit the graphite degeneration in the surface layer of iron castings. [...] Read more.

The main objective of this work is to investigate the mechanism of sulfur diffusion from the mold (sand resin P-toluol sulfonic acid mold, sulfur-containing acid) in liquid cast iron in order to limit the graphite degeneration in the surface layer of iron castings. A pyramid trunk with square section samples was cast. On the opposite side of the feed canal of the samples, steel sheets with different thicknesses (0.5, 1, and 3 mm) were inserted with the intention of blocking the diffusion of sulfur from the mold into the cast sample during solidification. The structure evaluation (graphite and matrix) in the surface layer and the casting body was recorded. The experimental results revealed that by blocking the direct diffusion of sulfur at the mold-casting interface, a decrease of the demodified layer thickness (for 0.5 mm steel sheet thickness) is obtained until its disappearance (for steel sheet thicknesses of more than 1 mm). The paper contains data that may be useful in elucidating the mechanism of graphite degeneration in the superficial layer of ductile iron castings. Based on the obtained results, we recommend using such barriers on the metal-mold interface, which are able to limit sulfur diffusion from the mold/core materials into the iron castings, in order to limit or even cease graphite degeneration in the Mg-treated surface iron casting layer. The paper presents additional data related to the interaction of sulfur at the ductile iron casting-mold interface previously analyzed. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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Review

Jump to: Research

28 pages, 2814 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Nano- and Micro-Scale Impact Testing of Hard Coatings: A Review

by Ben D. Beake

Coatings 2022, 12(6), 793; https://doi.org/10.3390/coatings12060793 - 8 Jun 2022

Cited by 16 | Viewed by 3625

Abstract

In this review, the operating principles of the nano-impact test technique are described, compared and contrasted to micro- and macro-scale impact tests. Impact fatigue mechanisms are discussed, and the impact behaviour of three different industrially relevant coating systems has been investigated in detail. [...] Read more.

In this review, the operating principles of the nano-impact test technique are described, compared and contrasted to micro- and macro-scale impact tests. Impact fatigue mechanisms are discussed, and the impact behaviour of three different industrially relevant coating systems has been investigated in detail. The coating systems are (i) ultra-thin hard carbon films on silicon, (ii) DLC on hardened tool steel and (iii) nitrides on WC-Co. The influence of the mechanical properties of the substrate and the load-carrying capacity (H³/E²) of the coating, the use of the test to simulate erosion, studies modelling the nano- and micro-impact test and performing nano- and micro-impact tests at elevated temperature are also discussed. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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17 pages, 3671 KiB

Open AccessFeature PaperReview

MoS₂-Based Substrates for Surface-Enhanced Raman Scattering: Fundamentals, Progress and Perspective

by Yuan Yin, Chen Li, Yinuo Yan, Weiwei Xiong, Jingke Ren and Wen Luo

Coatings 2022, 12(3), 360; https://doi.org/10.3390/coatings12030360 - 8 Mar 2022

Cited by 13 | Viewed by 4607

Abstract

Surface-enhanced Raman scattering (SERS), as an important tool for interface research, occupies a place in the field of molecular detection and analysis due to its extremely high detection sensitivity and fingerprint characteristics. Substantial efforts have been put into the improvement of the enhancement [...] Read more.

Surface-enhanced Raman scattering (SERS), as an important tool for interface research, occupies a place in the field of molecular detection and analysis due to its extremely high detection sensitivity and fingerprint characteristics. Substantial efforts have been put into the improvement of the enhancement factor (EF) by way of modifying SERS substrates. Recently, MoS₂ has emerged as one of the most promising substrates for SERS, which is also exploited as a complementary platform on the conventional metal SERS substrates to optimize the properties. In this minireview, the fundamentals of MoS₂-related SERS are first explicated. Then, the synthesis, advances and applications of MoS₂-based substrates are illustrated with special emphasis on their practical applications in food safety, biomedical sensing and environmental monitoring, together with the corresponding challenges. This review is expected to arouse broad interest in nonplasmonic MoS₂-related materials along with their mechanisms, and to promote the development of SERS studies. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in "Surface Characterization, Deposition and Modification" Section)

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