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Surfaces, Volume 6, Issue 1 (March 2023) – 8 articles

Cover Story (view full-size image): Layered lithium-rich manganese cathodes have attracted increasing attention due to their high reversible capacity and high operating voltage. Nevertheless, the development of layered lithium-rich manganese cathodes for commercial batteries is hampered by considerable capacity and voltage attenuation, poor rate performance, and significant reversible capacity loss during the first charge and discharge stages. Effective strategies have been adopted to address these drawbacks, such as ion doping, surface modification and nanostructure morphology. In this work, Li1.2Mn0.54Ni0.13Co0.13O2 nanotubes with conductive polymer PPy coating were investigated. The electrochemical measurements demonstrate that Li1.2Mn0.54Ni0.13Co0.13O2 nanotubes coated with PPy can significantly improve electrochemical performance. View this paper
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17 pages, 2894 KiB  
Article
Pulsed Current Effect on the Hard Anodizing of an AlSi10Mg Aluminum Alloy Obtained via Additive Manufacturing
by Elisa Dallari, Massimiliano Bononi, Annalisa Pola, Marialaura Tocci, Paolo Veronesi and Roberto Giovanardi
Surfaces 2023, 6(1), 97-113; https://doi.org/10.3390/surfaces6010008 - 13 Mar 2023
Cited by 1 | Viewed by 2605
Abstract
The hard anodizing treatments of cast Al-Si alloys are notoriously difficult. Indeed, their microstructural features hinder the growth of a uniform, compact, and defect-free anodic oxide. In this paper, AlSi10Mg samples, produced via Gravity Casting (GC) and Additive Manufacturing, i.e., Laser Powder Bed [...] Read more.
The hard anodizing treatments of cast Al-Si alloys are notoriously difficult. Indeed, their microstructural features hinder the growth of a uniform, compact, and defect-free anodic oxide. In this paper, AlSi10Mg samples, produced via Gravity Casting (GC) and Additive Manufacturing, i.e., Laser Powder Bed Fusion (L-PBF), were hard anodized in a sulfuric acid bath, in order to verify how the particular microstructure obtained via L-PBF affects the thickness, hardness, compactness, and defectiveness of the anodic oxide. Moreover, for the first time, Pulsed Direct Current (PDC) procedures were used to perform the hard anodizing treatments on additively manufactured AlSi10Mg alloy. Several combinations of temperature and electrical parameters, i.e., current density, frequency, and Duty Cycle, were tested. The anodized samples were characterized through optical microscopy analysis, Scanning Electron Microscopy (SEM) analysis, and accelerated corrosion tests, i.e., Potentiodynamic Polarization (POL) and Electrochemical Impedance Spectroscopy (EIS) measurements. The PDC procedures allowed improvement of the compromise between evenness, compactness, and defectiveness. Among the attempted PDC procedures, a specific combination of electrical parameters and temperature allowed the best results to be obtained, i.e., the highest hardness and the lowest volumetric expansion values without compromising the oxide quality rating and the corrosion resistance behavior. However, none of the attempted PCD strategies allowed the hardness values obtained on samples produced via GC to be reached. Full article
(This article belongs to the Collection Featured Articles for Surfaces)
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14 pages, 4419 KiB  
Article
Synthesis, Characterization of Some Conductive Aromatic Polyamides/Fe3O4 NPs/ITO, and Their Utilization for Methotrexate Sensing
by Mona A. Abdel-Rahman, Waleed A. El-Said, Eman M. Sayed and Aboel-Magd A. Abdel-Wahab
Surfaces 2023, 6(1), 83-96; https://doi.org/10.3390/surfaces6010007 - 03 Mar 2023
Viewed by 1679
Abstract
Here, we have synthesized four series of polyamide-conductive polymers and used them to modify Fe3O4 NPs/ITO electrodes. The ability of the modified electrodes to detect methotrexate (MTX) anticancer drug electrochemically was investigated. Synthesis of the target-conducting polyamides, P1a–d, P2a–d, P3a, [...] Read more.
Here, we have synthesized four series of polyamide-conductive polymers and used them to modify Fe3O4 NPs/ITO electrodes. The ability of the modified electrodes to detect methotrexate (MTX) anticancer drug electrochemically was investigated. Synthesis of the target-conducting polyamides, P1a–d, P2a–d, P3a, P3b, P3d, and P4c-d, based on different aromatic moieties, such as ethyl 4-(2-(4H-pyrazol-4-ylidene)hydrazinyl)benzoate, diphenyl sulfone, diphenyl ether or phenyl, has been achieved. They were successfully prepared in good yield via solution–polycondensation reaction of the diamino monomers with different dicarboxylic acid chlorides in the presence of N-methyl-2-pyrrolidone (NMP) as a solvent and anhydrous LiCl as a catalyst. A model compound 4 was synthesized from one mole of ethyl-4-(2-(3, 5-diamino-4H-pyrazol-4-ylidene)hydrazinyl) benzoate (diamino monomer) (3) with two moles benzoyl chloride. The structure of the synthesized monomers and polymers was confirmed by elemental and spectral analyses. In addition, thermogravimetric analysis evaluated the thermal stabilities of these polyamides. Furthermore, the morphological properties of selected polyamides were examined using an scanning electron microscope. Polyamide/Fe3O4/ITO electrodes were prepared, and the electrochemical measurements were performed to measure the new polyamides’ conductivity and to detect the MTX anticancer drug in phosphate buffer saline using cyclic voltammetry. The polyamides (P3b and P4b)/Fe3O4/ITO electrodes showed the highest sensitivity and reversibility towards MTX. Full article
(This article belongs to the Collection Featured Articles for Surfaces)
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19 pages, 4390 KiB  
Review
Electron Spectroscopy of Charge Exchange Effects in Low Energy Ion Scattering at Surfaces: Case Studies of Heavy Ions at Al Surface
by Pierfrancesco Riccardi
Surfaces 2023, 6(1), 64-82; https://doi.org/10.3390/surfaces6010006 - 02 Mar 2023
Cited by 1 | Viewed by 1570
Abstract
This work discusses studies of electron emissions during the interaction of low energy (in the keV energy range and below) singly charged ions with Aluminum surfaces. Analysis of the spectra provides insight into the electronic excitation processes and the dynamics of the interaction [...] Read more.
This work discusses studies of electron emissions during the interaction of low energy (in the keV energy range and below) singly charged ions with Aluminum surfaces. Analysis of the spectra provides insight into the electronic excitation processes and the dynamics of the interaction of the projectiles with the surface excitation. The work is primarily focused on the clarification of the role of electron promotion in charge exchange processes that occur during the cascade of atomic collisions. The work highlights the importance of the solid environment and of electron correlation in the understanding of charge exchange and energy deposition in ion-solids interactions. Full article
(This article belongs to the Collection Featured Articles for Surfaces)
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11 pages, 3111 KiB  
Article
In Situ Gas-Phase Polymerization of Polypyrrole-Coated Lithium-Rich Nanotubes for High-Performance Lithium-Ion Batteries
by Yangwen Chen, Beibei Sun, Xinchang Wang, Junmin Xu, Liwei Zhang and Jipeng Cheng
Surfaces 2023, 6(1), 53-63; https://doi.org/10.3390/surfaces6010005 - 22 Feb 2023
Cited by 1 | Viewed by 1483
Abstract
Conductive polymer polypyrrole (PPy)-coated lithium-rich manganese-based Li1.2Mn0.54Ni0.13Co0.13O2 (LMNCO) nanotube cathode materials were synthesized by electrospinning and subsequently subjected to low-temperature vapor-phase polymerization. X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy [...] Read more.
Conductive polymer polypyrrole (PPy)-coated lithium-rich manganese-based Li1.2Mn0.54Ni0.13Co0.13O2 (LMNCO) nanotube cathode materials were synthesized by electrospinning and subsequently subjected to low-temperature vapor-phase polymerization. X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) results confirm that the successful coating of the PPy layer (~2 nm) on the surface of LMNCO nanotubes did not destroy their morphologies or structures. Electrochemical tests indicate that the electrochemical performance of PPy-coated LMNCO nanotubes has been significantly enhanced. At a rate of 1 C, the discharge capacity of the PPy-coated LMNCO cell is 200.1 mAh g−1, and the capacity retention is 99% after 120 cycles. This excellent stability is attributed to the inhibition of side reactions and the protective function of the tubular structure due to the PPy coating layer. Additionally, the rate capability is also improved at a high current density due to the higher electronic and ionic conductivity. Full article
(This article belongs to the Collection Featured Articles for Surfaces)
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13 pages, 3245 KiB  
Article
Nano-and Microparticles of Carbon as a Tool for Determining the Uniformity of a Diffuse Discharge Exposure
by Mikhail Lomaev, Victor Tarasenko, Mikhail Shulepov, Dmitry Beloplotov and Dmitry Sorokin
Surfaces 2023, 6(1), 40-52; https://doi.org/10.3390/surfaces6010004 - 07 Feb 2023
Cited by 2 | Viewed by 1580
Abstract
At present, a diffuse discharge plasma of air and other gases at atmospheric pressure is widely used for the surface treatment of various materials. However, in many papers it is stated that erosion damages occur on flat anodes (targets) as a result of [...] Read more.
At present, a diffuse discharge plasma of air and other gases at atmospheric pressure is widely used for the surface treatment of various materials. However, in many papers it is stated that erosion damages occur on flat anodes (targets) as a result of the discharge plasma action. The shape of these damages depends on the discharge mode. In this study, the exposure uniformity was investigated by using nano- and micro-sized carbon particles deposited on a flat copper anode (a carbon layer). The diffuse discharge was formed in a ‘point-plane’ gap with a non-uniform electric field strength distribution by applying voltage pulses with an amplitude of 18 kV. It has been established that at a gap width of 8–10 mm, an imprint of the discharge plasma on the carbon layer deposited on a copper anode has no traces of local erosion. In order for erosion to occur on the surface of the anode in the form of uniformly distributed microcraters, it is necessary to increase the current density at the anode, for example, by decreasing the gap width. When decreasing the gap width to 6 mm and less, spark channels occur. They damage both the carbon layer and the copper anode in its central part. It has been shown that there are three characteristic zones: a color-changing peripheral part of the carbon layer, a decarbonized central part of the anode, and an annular zone located between the central and peripheral parts and containing individual microcraters. Full article
(This article belongs to the Special Issue Surface Engineering and Phase Transformations in Metals and Alloys)
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11 pages, 4049 KiB  
Article
Study on High-Speed Machining of 2219 Aluminum Utilizing Nanoparticle-Enhanced Minimum Quantity Lubrication (MQL) Technique
by Sagil James and Mehrshad Mazaheri
Surfaces 2023, 6(1), 29-39; https://doi.org/10.3390/surfaces6010003 - 22 Jan 2023
Cited by 1 | Viewed by 1564
Abstract
High-speed machining processes are significantly affected by the accumulation of heat generated by friction in the cutting zone, leading to reduced tool life and poor quality of the machined product. The use of cutting fluids helps to draw the heat out of the [...] Read more.
High-speed machining processes are significantly affected by the accumulation of heat generated by friction in the cutting zone, leading to reduced tool life and poor quality of the machined product. The use of cutting fluids helps to draw the heat out of the area, owing to their cooling and lubricating properties. However, conventional cutting fluid usage leads to considerable damage to human health and the environment, in addition to increasing overall manufacturing costs. In recent years, minimum quantity lubrication (MQL) has been used as an alternative lubricating strategy, as it significantly reduces cutting fluid consumption and eliminates coolant treatment/disposal needs, thereby reducing operational costs. In this study, we investigated microstructural surface finishing and heat generation during the high-speed cutting process of 2219 aluminum alloy using an MQL nanofluid. 2219 aluminum alloy offers an enhanced strength-to-weight ratio and high fracture toughness and is commonly used in a wide range of aerospace and other high-temperature applications. However, there is no relevant literature on MQL-based high-speed machining of these materials. In this study, we examined flood coolant and five different MQL nanofluids made by synthesizing 0.2% to 2% concentrations of Al2O3 nanoparticles into ultra-food-grade mineral oil. The study results reveal the chemistry between the MQL of choice and the corresponding surface finishing, showing that the MQL nanofluid with a 0.5% concentration of nanoparticles achieved the most optimal machining result. Furthermore, increasing the nanoparticle concentration does result in any further improvement in the machining result. We also found that adding a 0.5% concentration of nanoparticles to the coolant helped to reduce the temperature at the workpiece–tool interface, obtaining a good surface finish. Full article
(This article belongs to the Collection Featured Articles for Surfaces)
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27 pages, 5391 KiB  
Review
Revisiting Current Trends in Electrode Assembly and Characterization Methodologies for Biofilm Applications
by Luis Alberto Estudillo-Wong, Claudia Guerrero-Barajas, Jorge Vázquez-Arenas and Nicolas Alonso-Vante
Surfaces 2023, 6(1), 2-28; https://doi.org/10.3390/surfaces6010002 - 18 Jan 2023
Cited by 1 | Viewed by 2576
Abstract
Microbial fuel cell (MFC) is a sustainable technology resulting from the synergism between biotechnology and electrochemistry, exploiting diverse fundamental aspects for the development of numerous applications, including wastewater treatment and energy production. Nevertheless, these devices currently present several limitations and operational restrictions associated [...] Read more.
Microbial fuel cell (MFC) is a sustainable technology resulting from the synergism between biotechnology and electrochemistry, exploiting diverse fundamental aspects for the development of numerous applications, including wastewater treatment and energy production. Nevertheless, these devices currently present several limitations and operational restrictions associated with their performance, efficiency, durability, cost, and competitiveness against other technologies. Accordingly, the synthesis of nD nanomaterials (n = 0, 1, 2, and 3) of particular interest in MFCs, methods of assembling a biofilm-based electrode material, in situ and ex situ physicochemical characterizations, electrochemistry of materials, and phenomena controlling electron transfer mechanisms are critically revisited in order to identify the steps that determine the rate of electron transfer, while exploiting novel materials that enhance the interaction that arises between microorganisms and electrodes. This is expected to pave the way for the consolidation of this technology on a large scale to access untapped markets. Full article
(This article belongs to the Collection Featured Articles for Surfaces)
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1 pages, 146 KiB  
Editorial
Acknowledgment to the Reviewers of Surfaces in 2022
by Surfaces Editorial Office
Surfaces 2023, 6(1), 1; https://doi.org/10.3390/surfaces6010001 - 18 Jan 2023
Viewed by 799
Abstract
High-quality academic publishing is built on rigorous peer review [...] Full article
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