Journal Information
EISSN: 20796412
Published by: MDPI
Total articles ≅ 7,008

Latest articles in this journal

Published: 9 February 2023
by MDPI
Journal: Coatings
Abstract:
For the first time, the effect of Cuprous Oxide (Cu2O) sputtering power variation on the radio frequency sputtered Copper Chromium Oxide (CuCrO2) thin films was studied. In this work, the sputtering power of Cr2O3 was held constant at 200 W while the sputtering power of the Cu2O target was varied from 10 to 100 W. The films were subsequently annealed at 650 °C in N2 ambiance. The effects of Cu2O sputtering power variation on the structural, optical, and electrical properties of the films have been reported in this work. X-ray diffractometer (XRD) study revealed that the single-phase delafossite structure of CuCrO2 was only obtained at Cu2O sputtering power of 50 W. X-ray photoelectron spectroscopy (XPS) analysis further established the results of XRD study where Cu in 1+ oxidation state was identified in thin films obtained at 50 W of Cu2O sputtering power. The optical studies were conducted in this work on all the post-deposition annealed films in the wavelength range of 200–800 nm. The energy dispersive x-ray spectroscopy (EDS) study revealed a near stoichiometric composition ratio of 1:1.06 of Cu:Cr at% obtained in the films sputtered with 50 W of Cu2O sputtering power. The highest optical transmission of ~81% and the highest optical bandgap of 3.21 eV were observed for single-phase CuCrO2 thin films. The optical transmission and the optical bandgap were found to decrease with an increase in the Cu2O sputtering power. The electrical study performed on all the post-deposition annealed films revealed that the lowest resistivity of 0.652 Ω-cm was identified for single-phase CuCrO2 thin films obtained at 50 W of Cu2O sputtering power.
Published: 8 February 2023
by MDPI
Journal: Coatings
Abstract:
Largish molecules on metal surfaces may act as not only the building blocks of 2D self-assemblies, but also as the template to reshape the metal surfaces. Here, we report the molecular adsorption-induced formation of the periodic nanostripe arrays of substrate atoms through long-range mass transport. When adsorbed on the close-packed Cd(0001) surface, the triphenyl bismuth (TPB) molecules form a 2D self-assembly with 4 × Ö13 reconstruction. Simultaneously, periodic nanostripe arrays of Cd atoms appear on the substrate terraces. High-resolution scanning tunneling microscopy (STM) images indicate that the Cd nanostrips are built from the parallel segments of Cd atomic chains with 2 × 2 reconstruction. In the mixed phase, the Cd atomic chains exhibit only high-order commensuration when situated between two molecular domains. The massive structural rearrangement of the Cd(0001) surface can be attributed to a strong molecule–substrate interaction.
Published: 8 February 2023
by MDPI
Journal: Coatings
Abstract:
Various physical vapor deposition (PVD) techniques, such as molecular beam epitaxy, electron beam physical vapor deposition, pulsed laser deposition (PLD), arc discharge, magnetron sputtering and/or ion beam sputtering, are currently used for coating or growing thin films on solid substrates
Published: 8 February 2023
by MDPI
Journal: Coatings
Abstract:
Zeolites are used to store sunlight energy in the form of latent heat of adsorption. The energy is stored by dehydration of the substance and released by its rehydration. The availability of an online monitoring technique for this hydration/dehydration process is an extremely useful potentiality for an optimal exploitation of such technology, since it allows establishment of the degree of activation and saturation of the material. Here, an electrical method has been developed and used for monitoring the hydration/dehydration process of a sample of natural clinoptilolite. Clinoptilolite has been selected as a model zeolitic material for testing this monitoring technique since it is a widely spread, very inexpensive, and highly mechanically stable zeolite type, that could be used for such a purpose. The study has been performed in the presence of pure water vapor and wet air (75RH) after having dehydrated the sample by exposition to sunlight for 12 h. The developed monitoring method has also allowed us to have information on the kinetics of the process (Lagergren pseudo-first order), to establish the specific rate of hydration (3.3 × 103 min1), and to have an idea of the involved adsorption mechanism. The sample of natural clinoptilolite was also chemically and structurally characterized by EDS, XRD, DSC, and TGA.
Published: 8 February 2023
by MDPI
Journal: Coatings
Abstract:
The aim of this study was to evaluate the effect of heat treatment on the phase composition, hardness, and abrasion wear resistance of hard-anodized layers (HAL) on 1011 aluminum alloy. X-ray diffraction analysis revealed the Al2O3·3H2O phase in the structure of HAL synthesized for 1 h. While in the heat-treated HAL, aluminum oxide phases of the α-Al2O3(amorphous) and γ-Al2O3(amorphous) types were found. Treatment at 400 °C for 1 h increased the HAL microhardness from 400 to 650 HV, and its abrasive wear resistance with fixed abrasive by up to 2.6 times. The ranking of various ways of hardening aluminum alloys relative to the D16 alloy showed that the abrasive wear resistance of heat-treated HAL is 20 times higher. Plasma electrolyte oxidation increased the abrasive wear resistance of the D16 alloy by 70–90 times, and its coating with high-speed oxygen fuel by 75–85 times. However, both methods are complex, energy-consuming, and require fine grinding of parts. Despite the lower wear resistance of HAL, their synthesis is cheaper and does not require the fine-tuning of parts. Moreover, despite the low hardness of HAL at present, hard anodizing is already commercially used to harden engine pistons, clamshell rotators, and pulleys.
Published: 8 February 2023
by MDPI
Journal: Coatings
Abstract:
The degradation process and the electrochemical behavior of two anti-corrosion and anti-fouling coating systems (FW-1 and FW-2) in a simulated diurnal cycling immersion environment (3.5% NaCl, 35 °C 12 h + 25 °C 12 h) were investigated by electrochemical impedance spectroscopy (EIS) technology. Combined with the coating gloss, color difference, adhesion strength and scanning electron microscopy (SEM) tests, the micro morphologies and the variations of the performance parameters were comparatively analyzed. The results showed that in the 160 days of immersion, with the hydrolysis of the FW-1 topcoat resin and some pigments dissolved and released, the surface micro-morphology of the coating changes from rough to smooth, thereby increasing the gloss. While, for the FW-2 topcoat, the occurrence of micro pores and tiny cracks results in an increase in the roughness and a decrease in the gloss. The release of the copper ion particles in the antifouling topcoat has an influence on the color, manifesting as obvious rise in the color difference of the coating. The low-frequency impedance (|Z|0.01 Hz) values of both coating samples decreases slowly and provides very good shielding to the carbon steel substrate. The self-polishing of the topcoat has no big effect on the electrochemical performance of the whole anti-corrosion and anti-fouling coating system; the protective performance of the coating system mainly depends on the integrity of the primer and the intermediate paint.
Published: 8 February 2023
by MDPI
Journal: Coatings
Abstract:
The internal pavement structure is a “black box”; an accurate strain response for the pavement interlayer structure under vehicle load is hard to obtain by conventional road surface detection methods. This is due to the true strain field of the pavement structure, which means that the service state of the pavement cannot be accurately evaluated. This paper proposes an innovative strain sensor based on a carbon nanotube and epoxy (CNT/EP) composite to solve the current strain monitoring problem in asphalt pavement health monitoring. The CNT/EP composite encapsulation method was proposed, and the I-shaped strain sensor for asphalt pavement structure was developed. The strain–resistance response characteristics of the self-developed sensor were further investigated using a universal testing machine. The encapsulated sensor was used to monitor the strain of the asphalt mixture by means of a laboratory asphalt concrete beam and a practical pavement field. The results showed that the encapsulation method proposed in the study is suitable for CNT/EP material, which could guarantee the survivability and monitoring effectiveness of the self-developed sensor under the harsh environment of high temperature and pressure of asphalt mixture paving. The resistance of encapsulated sensor presents a linear relationship with strain. The laboratory and practical paving verified the feasibility of the self-sensor for strain monitoring of asphalt pavement. Compared to other post-excavating buried sensors, the self-developed sensor can be embedded in the pavement interlayer as the asphalt mixtures paving process, which can obtain the real strain response of pavement structure and reduce the perturbation of the sensor to the dynamic response of the pavement.
Published: 8 February 2023
by MDPI
Journal: Coatings
Abstract:
Polyetheretherketone (PEEK) and its fiber-reinforced materials are thermoplastic polymer materials with broad application prospects. Depositing Ni-P alloy on them can improve their poor conductivity and electromagnetic shielding performance, and further expand their application field. The application effect of the plated parts is significantly impacted by the bonding strength between PEEK and coating. The bonding strength between non-metallic substrate and coating is largely influenced by the surface characteristics of the substrate. Therefore, it is significant to study how the surface roughness of PEEK materials and the modified fibers in materials affect the adhesion of the coating. In this study, Ni-P alloy was electroless deposited on PEEK, 30% carbon-fiber-reinforced PEEK (CF30/PEEK), and 30% glass-fiber-reinforced PEEK (GF30/PEEK) with varying surface roughness. The influence of surface roughness and modified fibers on the coating adhesion was studied. Additionally, the effect of the concentrations of nickel sulfate, sodium hypophosphite, pH, and temperature on the deposition rate of the coating was investigated for the three materials. Based on the highest deposition rate, the process parameters were then optimized. The results demonstrated that as surface roughness increased, adhesion between substrate and coating first increased and then decreased. The surface roughness Ra of 0.4 μm produced the highest coating adhesion. Additionally, fiber-reinforced PEEK adhered to coatings more effectively than PEEK did. The mechanism of the difference in bonding strength between different PEEK-modified materials and coatings was revealed. The optimal process parameters were: nickel sulfate: 25 g/L, sodium hypophosphite: 30 g/L, pH: 5.0, and temperature: 70 °C.
Published: 8 February 2023
by MDPI
Journal: Coatings
Abstract:
As semiconductor devices become miniaturized, the importance of the molecular-level understanding of the fabrication processes is growing. Titanium nitride (TiN) is an important material utilized in various architectural components of semiconductor devices requiring precise control over size and shape. A reported process for atomic layer etching (ALE) of TiN involves surface oxidation into titanium oxide (TiO2) and selective oxidized layer removal by hydrogen fluoride (HF). However, the chemical selectivity of these Ti-based materials in the etching process by HF remains unclear. In this study, computational chemistry methods utilizing density functional theory (DFT) calculations were applied to the fluorination reactions of TiN, TiO2, and SiO2 to identify and compare the surface chemical reactivity of these substrates toward etching processes. It is shown that the materials can be etched using HF, leaving TiF4 and SiF4 as the byproducts. However, while such a TiN reaction is thermodynamically hindered, the etching of TiO2 and SiO2 is suggested to be favorable. Our study provides theoretical insights into the fluorination reactivity of TiN, which has not been reported previously regardless of technological importance. Furthermore, we explore the etching selectivity between TiN, TiO2, and SiO2, which is a crucial factor in the ALE process conditions of TiN.
Published: 8 February 2023
by MDPI
Journal: Coatings
Abstract:
Antibiotics present common pollution in the environment, and they are often found in surface waters. Their presence or decomposition in water under natural sunlight can cause different unwanted consequences on the environment. In this paper, we report the application of 3D printed photocatalysts shaped as helix static mixers for tentative photocatalytic oxidation of antibiotic amoxicillin. The research was carried out in laboratory conditions in a semi-pilot-scale compound parabolic reactor (CPC) with static mixers made from PETG with TiO2 and MWCNT as fillers. The efficiency of 3D printed photocatalysts was evaluated in terms of amoxicillin decomposition kinetics using a pseudo-first-order kinetic model. The experimental results of amoxicillin decomposition and generated by-products were analyzed by using the Q-TOF LC/MS technique and presented using MassHunter Workstation.
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