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Open AccessArticle

Self-Lubricating Ni-Based Composite Coating with Core-Shell Structured Mo@Ag@Ni Addition: Tribological Behaviors and Interface Evolution over Multi-Thermal Cycles

by Nairu He, Yuanhai Zhai, Ziwen Fang, Jie Yang and Wei Chen

Lubricants 2025, 13(9), 387; https://doi.org/10.3390/lubricants13090387 - 29 Aug 2025

Cited by 1 | Viewed by 911

Abstract

The rapid dissipation of soft metal lubricants would deteriorate the self-lubricating properties of the coatings at elevated temperatures. In this study, the core-shell structured Mo@Ag@Ni particles were prepared via electroless plating to suppress the rapid dissipation of Ag and facilitate tribochemical reactions at [...] Read more.

The rapid dissipation of soft metal lubricants would deteriorate the self-lubricating properties of the coatings at elevated temperatures. In this study, the core-shell structured Mo@Ag@Ni particles were prepared via electroless plating to suppress the rapid dissipation of Ag and facilitate tribochemical reactions at high temperatures. The NiCrAlY-Mo@Ag@Ni composite coating was sprayed on the substrate of Inconel 718 alloy using atmospheric plasma spraying technology. The results of this study show that the structural design of Mo@Ag@Ni can enhance the bonding strength of the particle interface, resulting in a high microhardness of approximately 332.2 HV. During high-temperature friction tests, Mo@Ag@Ni can provide excellent tribological properties by promoting the silver molybdate formation on the worn surface. At 800 °C, the friction coefficient and wear rate are only about 0.32 and 1.58 × 10⁻⁵ mm³N⁻¹m⁻¹, respectively. Moreover, the Ni shell layer can inhibit the rapid diffusion of Ag and provide sufficient Ag₂O to maintain the continuity of Ag₂MoO₄ lubricating film, which endows the coating with a longer lubrication life. Over multi-thermal cycles, the friction coefficient and wear rate constantly maintain at about 0.3 and 2.5 × 10⁻⁵ mm³N⁻¹m⁻¹, respectively. Full article

(This article belongs to the Special Issue Tribological Properties of Sprayed Coatings)

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13 pages, 2095 KB

Open AccessEditor’s ChoiceArticle

Two-Dimensional Silver Bismuth Oxide/Bismuth Molybdate Z-Scheme Heterojunctions with Rich Oxygen Vacancies for Improved Pollutant Degradation and Bacterial Inactivation

by Yanhong Wang, Huijie Zhu, Pengli He, Mingyu Li, Yinhuan Cao, Yanqiang Du, Yun Wen, Yixiang Zhao, Xiaowen Liu and Yonglong Song

Crystals 2025, 15(4), 318; https://doi.org/10.3390/cryst15040318 - 27 Mar 2025

Cited by 2 | Viewed by 784

Abstract

The effective removal of organic pollutants and bacteria are of great significance considering the hazards to the environment and human health. The two-dimensional AgBiO₃/Bi₂MoO₆ heterojunction with rich oxygen vacancies was successfully fabricated via a hydrothermal method and systematically [...] Read more.

The effective removal of organic pollutants and bacteria are of great significance considering the hazards to the environment and human health. The two-dimensional AgBiO₃/Bi₂MoO₆ heterojunction with rich oxygen vacancies was successfully fabricated via a hydrothermal method and systematically characterized by various analytical techniques. The photocatalytic experimental results revealed that the addition of AgBiO₃ improved the photocatalytic performance of Bi₂MoO₆, and the AgBiO₃/Bi₂MoO₆-10 heterojunction possessed the best degradation effect toward RhB (72%) within 100 min, with 1.38 and 1.44 times higher activity than pure Bi₂MoO₆ and AgBiO₃, respectively. The bacteria were completely inactivated within 90 min by AgBiO₃/Bi₂MoO₆-10 heterojunction. The reason for the enhancement of photocatalytic activity was the synergistic effect between AgBiO₃ and Bi₂MoO₆. The constructed Z-scheme heterojunction with oxygen vacancies improved the separation efficiency of photo-induced electrons and holes and broadened the range of visible-light absorption. The trapping experiments and ESR indicated that superoxide radical and holes were the main reactive species. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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16 pages, 6843 KB

Open AccessArticle

Preparation of Silver Molybdate-Decorated Reduced Graphene Oxide Nanocomposite Using Ionic Liquids for High-Performance Energy Storage Application: A Greener Approach

by Catherin Meena Boominathan, Zouhaier Aloui, Manickam Selvaraj, Annasaheb V. Moholkar, Chelliah Koventhan, An-Ya Lo and Yi-Jen Huang

Processes 2025, 13(2), 327; https://doi.org/10.3390/pr13020327 - 24 Jan 2025

Cited by 6 | Viewed by 1998

Abstract

Achieving high energy density while maintaining high power density and long cycle life in supercapacitors, particularly in supercapatteries (SCs), through a thermally stable, greener ionic liquid approach remains a significant challenge for an advanced energy storage application. In this work, we prepared high [...] Read more.

Achieving high energy density while maintaining high power density and long cycle life in supercapacitors, particularly in supercapatteries (SCs), through a thermally stable, greener ionic liquid approach remains a significant challenge for an advanced energy storage application. In this work, we prepared high conductive and high charge storage capability bimetallic transition metal molybdate [Ag₂Mo₂O₇ (AgM)], synergistic with reduced graphene oxide (rGO) coated on nickel foam (AgM/rGO/NF). The physio-chemical characterization revealed a ball-like cluster morphology wrapped in rGO nanosheets and a spinel-type cubic structure using scanning electron microscopy (FE-SEM) displays and X-ray diffraction (XRD) analyses. Further, the electrochemical performance of AgM/rGO/NF electrode achieved a remarkable specific C_sp value of 573.63 F/g at a current density of 1.0 A/g in 3 M KOH electrolyte. An asymmetric SCs (ASCs) device was fabricated using AgM/rGO/NF as the positive and rGO as the negative electrodes, achieving a wide potential window of 1.3 V. The ASC demonstrated an energy density of 16.71 Wh/kg at a power density of 642.98 W/kg, highlighting AgM/rGO/NF’s potential as an advanced electrode material for energy storage applications. Full article

(This article belongs to the Special Issue Advances in Electrode Materials for Energy Storage Applications)

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18 pages, 6764 KB

Open AccessArticle

A Facile Synthesis of RGO-Ag₂MoO₄ Nanocomposites for Efficient Lead Removal from Aqueous Solution

by Mohd Shoeb, Fouzia Mashkoor, Mohmmad Naved Khan and Changyoon Jeong

Molecules 2024, 29(21), 5152; https://doi.org/10.3390/molecules29215152 - 31 Oct 2024

Cited by 8 | Viewed by 1488

Abstract

Efficiently treating wastewater, particularly the elimination of heavy metal ions from water systems, continues to be one of the most pressing and complex challenges in modern environmental management. In this work, reduced graphene oxide coupled silver molybdate binary nanocomposites (RGO-Ag₂MoO₄ [...] Read more.

Efficiently treating wastewater, particularly the elimination of heavy metal ions from water systems, continues to be one of the most pressing and complex challenges in modern environmental management. In this work, reduced graphene oxide coupled silver molybdate binary nanocomposites (RGO-Ag₂MoO₄ NCs) have been prepared via hydrothermal method. The crystalline nature and surface properties of the developed RGO-Ag₂MoO₄ NCs were proved by XRD, FTIR, SEM, and EDS techniques. Adsorption experiments demonstrated that the nanocomposites (NCs) effectively removed Pb(II) ions within 120 min, achieving a maximum removal efficiency ranging from 94.96% to 86.37% for Pb(II) concentrations between 20 and 100 mg/L at pH 6. Kinetic studies showed that the adsorption process followed a pseudo-second order model. Isotherm analysis presented that the Langmuir model provided the greatest fit for the equilibrium data, with a monolayer adsorption capacity of 128.94 mg/g. Thermodynamic analysis revealed that the adsorption process was spontaneous and endothermic. The results of this study highlight RGO-Ag₂MoO₄ NCs as a highly promising and eco-friendly material for the effective elimination of Pb(II) ions from wastewater. Their strong adsorption capacity, coupled with sustainable properties, makes them an efficient solution for addressing lead contamination, offering significant potential for practical applications in water treatment systems. Full article

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16 pages, 3936 KB

Open AccessFeature PaperArticle

Characterization and Formation Mechanism of Ag₂MoO₄ Crystals via Precipitation Method: Influence of Experimental Parameters and Crystal Morphology

by Sara Calistri, Alessandro Gessi, Giuseppe Marghella, Stefania Bruni and Alberto Ubaldini

Crystals 2024, 14(3), 254; https://doi.org/10.3390/cryst14030254 - 5 Mar 2024

Cited by 4 | Viewed by 2697

Abstract

Ag₂MoO₄ crystals were prepared by a precipitation method by mixing parent solutions of silver nitrate and sodium molybdate. The effects of experimental parameters such as temperature, concentration, and pH were studied. The samples were found to be crystalline, pure, and [...] Read more.

Ag₂MoO₄ crystals were prepared by a precipitation method by mixing parent solutions of silver nitrate and sodium molybdate. The effects of experimental parameters such as temperature, concentration, and pH were studied. The samples were found to be crystalline, pure, and monophasic in all cases, except in the case of very low pH. The precipitation leads to the formation of the cubic phase β and no secondary phase is present within the limits of detection of XRD and Raman spectroscopy. However, in some cases, at high temperature and high pH, silver oxide nanoparticles form on the surfaces of the crystals, which create a fluorescence background in the Raman spectra, which is otherwise absent. Analyses with the electron microscope have highlighted that the most common crystalline shape is octahedral, which is the most prevalent at low temperatures and pH around 7, but others are also possible, in particular at high temperatures. No growth occurs after precipitation, so crystals with different appearances form at the same time. Full article

(This article belongs to the Special Issue Crystallization Process and Simulation Calculation, Second Edition)

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18 pages, 27252 KB

Open AccessArticle

High-Temperature Friction and Wear Behavior of Nickel-Alloy Matrix Composites with the Addition of Molybdate

by Jinming Zhen, Congcong Zhen, Yunxiang Han, Lin Yuan, Liwei Yang, Tianqi Yang and Shuo Guo

Lubricants 2023, 11(12), 516; https://doi.org/10.3390/lubricants11120516 - 7 Dec 2023

Cited by 8 | Viewed by 2634

Abstract

To improve the tribological characteristics of materials employed in spatial mechanisms, there is a significant requirement to develop solid lubricating composites with superior performance. This study investigates the tribological characteristics of composites consisting of a nickel matrix combined with silver molybdate and barium [...] Read more.

To improve the tribological characteristics of materials employed in spatial mechanisms, there is a significant requirement to develop solid lubricating composites with superior performance. This study investigates the tribological characteristics of composites consisting of a nickel matrix combined with silver molybdate and barium molybdate. The experimental analysis focuses on evaluating the tribological behaviors of these composites from 25 °C to 800 °C. The findings indicate that the combined application of silver molybdate and barium molybdate resulted in enhanced self-lubricating properties of the composites, particularly at temperatures over 400 °C. The inclusion of both silver molybdate and barium molybdate in the composite resulted in the achievement of a low friction coefficient (0.34–0.5), as well as a wear rate ranging from 0.47 to 1.25 × 10⁻⁴ mm³ N⁻¹m⁻¹, within the temperature range of 400 to 800 °C. Furthermore, an analysis was conducted to examine the wear processes of the composites at various sliding temperatures. This analysis was based on the evaluation of the chemical composition and morphologies of the sliding surfaces, which were verified by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Raman spectroscopy. Full article

(This article belongs to the Special Issue Recent Advances in High Temperature Tribology)

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14 pages, 3951 KB

Open AccessArticle

Effects of Ni/MoS₂, Ag and Cr₂O₃ on the Microstructure and Mechanical Performance of a CoCrFeNi High-Entropy Alloy over a Wide Temperature Range

by Chao Xu, Dandan Liu, Chuanwei Zhang, Siyu Meng and Bin Wang

Coatings 2023, 13(10), 1760; https://doi.org/10.3390/coatings13101760 - 12 Oct 2023

Cited by 9 | Viewed by 2165

Abstract

In the field of aerospace, core components require excellent wear resistance, lubrication and mechanical properties over a wide temperature range. In this study, three groups of CoCrFeNi high-entropy alloy (HEA)-based self-lubricating composites were designed with the addition of Ag, Ni/MoS₂ and Cr [...] Read more.

In the field of aerospace, core components require excellent wear resistance, lubrication and mechanical properties over a wide temperature range. In this study, three groups of CoCrFeNi high-entropy alloy (HEA)-based self-lubricating composites were designed with the addition of Ag, Ni/MoS₂ and Cr₂O₃ using discharge-plasma-sintering technology. Their microstructure, phase composition, mechanical properties, friction and wear properties were analyzed. The results showed that, with the addition of Ag, the hardness and yield stress of HEA-Ni/MoS₂-Ag were reduced by 36 HV and 24 MPa, respectively, while the plastic strain was increased by 2%. With the addition of Cr₂O₃, the hardness (382 HV) and yield stress (430 MPa) of HEA-Ni/MoS₂-Ag-Cr₂O₃ reached their highest values, but the plastic strain reached its lowest value. HEA-Ni/MoS₂-Ag-Cr₂O₃ had the smallest friction coefficient in which the friction coefficient at 800 °C was only 0.42. Additionally, it had a small wear rate of 3.2 × 10⁻⁶ mm³/Nm over a wide temperature range. At lower temperatures, Ni/MoS₂ and Ag were conducive to lubrication, and the wear resistance was improved by the presence of Cr₂O₃. At high temperatures, a nickel oxide phase and a variety of silver molybdate phases were formed via a tribochemical reaction, which was vital to the high-temperature tribological properties. Full article

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12 pages, 4808 KB

Open AccessFeature PaperArticle

Kinetic Highlights of the Reduction of Silver Tungstate by Mg + C Combined Reducer

by Marieta Zakaryan, Khachik Nazaretyan, Sofiya Aydinyan and Suren Kharatyan

Metals 2022, 12(6), 1000; https://doi.org/10.3390/met12061000 - 10 Jun 2022

Cited by 3 | Viewed by 2536

Abstract

The programmed reduction of tungstates and molybdates may yield the production of an intimate mixture of metals, pseudo-alloys or composite powders. As an extension of the study of obtaining powders of tungsten-copper, molybdenum-copper and tungsten-nickel from their respective salts, in the present study [...] Read more.

The programmed reduction of tungstates and molybdates may yield the production of an intimate mixture of metals, pseudo-alloys or composite powders. As an extension of the study of obtaining powders of tungsten-copper, molybdenum-copper and tungsten-nickel from their respective salts, in the present study the reduction of silver tungstate was performed. Considering the extreme conditions for the synthesis of W-Ag alloys in the combustion wave and the limited toolkit for the study of the associated reduction mechanism, the interaction in the Ag₂WO₄-Mg-C system was modeled at high heating rates closer to the heating rates of reagents in the combustion wave, namely by the high-speed temperature scanner (HSTS). For the effective study of the interaction mechanism and calculation of the kinetic parameters of the individual stages, the heating rate of the reagents was changed in a wide range (from 100 to 1200 °C min⁻¹). The interaction scheme and the sequence of the reactions along with their starting temperatures were deduced; the nature of intermediates formed during the reduction process and the microstructure evolution were monitored. Full article

(This article belongs to the Special Issue Synthesis, Characterization and Properties of Multifunctional Metallic Materials and Metal-Based Composites)

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15 pages, 5435 KB

Open AccessArticle

SERS Determination of Trace Phosphate in Aquaculture Water Based on a Rhodamine 6G Molecular Probe Association Reaction

by Ye Jiang, Xiaochan Wang, Guo Zhao, Yinyan Shi, Nguyen Thi Dieu Thuy and Haolin Yang

Biosensors 2022, 12(5), 319; https://doi.org/10.3390/bios12050319 - 10 May 2022

Cited by 15 | Viewed by 3661

Abstract

Although phosphate (Pi) is a necessary nutrient for the growth of aquatic organisms, the presence of excess Pi leads to water eutrophication; thus, it is necessary to accurately determine the content of Pi in water. A method for the determination of trace Pi [...] Read more.

Although phosphate (Pi) is a necessary nutrient for the growth of aquatic organisms, the presence of excess Pi leads to water eutrophication; thus, it is necessary to accurately determine the content of Pi in water. A method for the determination of trace Pi in aquaculture water was developed based on surface-enhanced Raman spectroscopy (SERS) combined with rhodamine 6G (R6G)-modified silver nanoparticles (AgNPs) as the active substrate. The adsorption of R6G on the AgNP surfaces led to a strong SERS signal. However, in the presence of Pi and ammonium molybdate, phosphomolybdic acid formed, which further associated with R6G to form a stable R6G-PMo₁₂O₄₀³⁻ association complex, thereby hindering the adsorption of R6G on the AgNPs, and reducing the SERS intensity; this sequence formed the basis of Pi detection. The decrease in the SERS intensity was linear with respect to the Pi concentration (0.2–20 μM), and the limit of detection was 29.3 nM. Upon the application of this method to the determination of Pi in aquaculture water, a recovery of 94.4–107.2% was obtained (RSD 1.77–6.18%). This study provides an accurate, rapid, and sensitive method for the trace determination of Pi in aquaculture water, which is suitable for on-site detection. Full article

(This article belongs to the Section Environmental, Agricultural, and Food Biosensors)

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21 pages, 9280 KB

Open AccessArticle

Formation of Solid Lubricants during High Temperature Tribology of Silver-Doped Molybdenum Nitride Coatings Deposited by dcMS and HIPIMS

by Martin Fenker, Martin Balzer, Sabine Kellner, Tomas Polcar, Andreas Richter, Frank Schmidl and Tomas Vitu

Coatings 2021, 11(11), 1415; https://doi.org/10.3390/coatings11111415 - 19 Nov 2021

Cited by 11 | Viewed by 3254

Abstract

The coating system MoN-Ag is an interesting candidate for industrial applications as a low friction coating at elevated temperatures, due to the formation of lubricous molybdenum oxides and silver molybdates. Film deposition was performed by high-power impulse magnetron sputtering and direct current magnetron [...] Read more.

The coating system MoN-Ag is an interesting candidate for industrial applications as a low friction coating at elevated temperatures, due to the formation of lubricous molybdenum oxides and silver molybdates. Film deposition was performed by high-power impulse magnetron sputtering and direct current magnetron sputtering. To facilitate a future transfer to industry Mo-Ag composite targets have been sputtered in Ar/N₂ atmosphere. The chemical composition of the deposited MoN-Ag films has been investigated by wavelength dispersive X-ray spectroscopy. Morphology and crystallographic phases of the films were studied by scanning electron microscopy and X-ray diffraction. To obtain film hardness in relation to Ag content and bias voltage, the instrumented indentation test was applied. Pin-on-disc tribological tests have been performed at room temperature and at high temperature (HT, 450 °C). Samples from HT tests have been analyzed by Raman measurements to identify possible molybdenum oxide and/or silver molybdate phases. At low Ag contents (≤7 at.%), coatings with a hardness of 18–31 GPa could be deposited. Friction coefficients at HT decreased with increasing Ag content. After these tests, Raman measurements revealed the MoO₃ phase on all samples and the Ag₂Mo₄O₁₃ phase for the highest Ag contents (~23–26 at.%). Full article

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

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12 pages, 10895 KB

Open AccessArticle

Friction and Wear Behavior of an Ag–Mo Co-Implanted GH4169 Alloy via Ion-Beam-Assisted Bombardment

by Jiajun Zhu, Meng Xu, Wulin Yang, Deyi Li, Lingping Zhou and Licai Fu

Coatings 2017, 7(11), 191; https://doi.org/10.3390/coatings7110191 - 6 Nov 2017

Cited by 8 | Viewed by 6498

Abstract

Ag, Mo, and Ag–Mo were respectively implanted into GH4169 alloy substrates without heating via ion-beam-assisted bombardment technology (IBAB). In addition, the wear performance under low sliding speed and applied load were researched at room temperature (RT). A small amount silver molybdate phase could [...] Read more.

Ag, Mo, and Ag–Mo were respectively implanted into GH4169 alloy substrates without heating via ion-beam-assisted bombardment technology (IBAB). In addition, the wear performance under low sliding speed and applied load were researched at room temperature (RT). A small amount silver molybdate phase could be detected on the surface of the co-implanted GH4169 alloy bombarded by a high-energy ion beam. The average friction coefficients under the steady wear state had almost no change at all. Compared with the un-implanted GH4169 alloys, the wear rate of the GH4169 alloys with co-implantation of Ag and Mo was reduced by 75%. A large amount of the silver molybdate phase could be generated due to the tribo-reaction on the worn surface during sliding. It benefits the formation of continuous oxide layers as lubrication and protected layers, leading to the change in the predominant wear mechanism from abrasion and adhesion wear to oxidation wear. Full article

(This article belongs to the Special Issue Coatings Tribology)

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10 pages, 4463 KB

Open AccessArticle

Fabrication of Luminescent Antireflective Coatings with CaMoO₄:Eu³⁺/Ag Composite Structure

by Kazuhiro Matsumoto, Manabu Hagiwara and Shinobu Fujihara

Coatings 2017, 7(6), 74; https://doi.org/10.3390/coatings7060074 - 2 Jun 2017

Cited by 4 | Viewed by 5513

Abstract

Highly transparent and luminescent CaMoO₄:Eu³⁺/Ag composite films were fabricated on glass substrates as multifunctional antireflective (AR) coatings. The films were deposited through a combination of a sol–gel dip-coating technique and a hot water treatment. With the addition of an [...] Read more.

Highly transparent and luminescent CaMoO₄:Eu³⁺/Ag composite films were fabricated on glass substrates as multifunctional antireflective (AR) coatings. The films were deposited through a combination of a sol–gel dip-coating technique and a hot water treatment. With the addition of an aluminum source in coating solutions, the sol–gel-derived films underwent a remarkable microstructural change during the hot water treatment due to the reaction between an amorphous alumina phase and water. This change brought both an antireflective effect (suppression of Fresnel reflection) and luminescence enhancement (suppression of total internal reflection) to the films. The introduction of Ag nanoparticles into the films further increased luminescence intensity without losing the antireflective effect. Full article

(This article belongs to the Special Issue Antireflective Coatings for Glass and Transparent Polymers)

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