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Surfaces
Number of Followers: 2  Open Access journalISSN (Online) 2571-9637 Published by MDPI  [258 journals]
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- Surfaces, Vol. 6, Pages 227-238: Nitrogen- and Fluorine-Doped Carbon
Nanohorns as Efficient Metal-Free Oxygen Reduction Catalyst: Role of the
Nitrogen Groups
Authors: Elisa Tosin, Teresa Gatti, Stefano Agnoli, Laura Calvillo, Enzo Menna
First page: 227
Abstract: The search of active, stable and low costs catalysts for the oxygen reduction reaction (ORR) is crucial for the extensive use of fuel cells and metal–air batteries. The development of metal-free catalysts, instead of platinum-based materials, can dramatically reduce the cost and increase the efficiency of these devices. In this work, carbon nanohorns (CNHs) have been covalently functionalized with N-containing heterocycles by the Tour reaction protocol and tested as metal-free ORR catalysts. The insertion of N-functionalities favored the complete reduction of oxygen to hydroxyl ions, while their absence favored the production of hydrogen peroxide. With the aim of determining the N-species responsible for the ORR activity of CNHs, photoemission and electrochemical measurements were combined. Results suggest that protonated N is the main species involved in the ORR process, facilitating the adsorption of oxygen, with their consequent reduction to neutral hydrogenated N species.
Citation: Surfaces
PubDate: 2023-07-08
DOI: 10.3390/surfaces6030015
Issue No: Vol. 6, No. 3 (2023)
- Surfaces, Vol. 6, Pages 239-248: Using Highly Flexible SbSn@NC Nanofibers
as Binderless Anodes for Sodium-Ion Batteries
Authors: Jiaojiao Liang, Gengkun Fang, Xinmiao Niu, Zhihao Zhang, Yufei Wang, Lingyuan Liao, Xiaoming Zheng, Di Huang, Yuehua Wei
First page: 239
Abstract: Flexible and binderless electrodes have become a promising candidate for the next generation of flexible power storage devices. However, developing high-performance electrode materials with high energy density and a long cycle life remains a serious challenge for sodium-ion batteries (SIBs). The main issue is the large volume change in electrode materials during the cycling processes, leading to rapid capacity decay for SIBs. In this study, flexible electrodes for a SnSb alloy–carbon nanofiber (SnSb@NC) membrane were successfully synthesized with the aid of hydrothermal, electrospinning and annealing processes. The as-prepared binderless SnSb@NC flexible anodes were investigated for the storage properties of SIBs at 500 °C, 600 °C and 700 °C (SnSb@NC-500, SnSb@NC-600 and SnSb@NC-700), respectively. And the flexible SnSb@NC-700 electrode displayed the preferable SIB performances, achieving 240 mAh/g after 100 cycles at 0.1 A g−1. In degree-dependent I-V curve measurements, the SnSb@NC-700 membrane exhibited almost the same current at different bending degrees of 0°, 45°, 90°, 120° and 175°, indicating the outstanding mechanical properties of the flexible binderless electrodes.
Citation: Surfaces
PubDate: 2023-07-16
DOI: 10.3390/surfaces6030016
Issue No: Vol. 6, No. 3 (2023)
- Surfaces, Vol. 6, Pages 249-256: Acetylation of Scaled-Down Chitin
Nanofiber Films to Improve Mechanical Properties
Authors: Jun-ichi Kadokawa, Chiharu Iiyama, Aoi Nakashima
First page: 249
Abstract: A flexible chitin nanofiber (ChNF) film with a thin fiber morphology, named, scaled-down (SD)-ChNF film, was previously found to be formed via successive partial deacetylation of the parent self-assembled ChNFs, cationization/dispersion via electrostatic repulsion in aqueous acetic acid, and suction filtration/drying. In this study, acetylation of a SD-ChNF film using acetic anhydride in pyridine was carried out to improve the mechanical properties. The FT-IR spectra of the acetylated SD-ChNF films suggested that acetylation progressed from the surface to the interior of the films with the increasing amounts of pyridine and elevating temperatures. The degrees of acetylation (DA) strongly affected the chitin crystallinity and surface morphology of the acetylated SD-ChNF films. Tensile testing of the acetylated SD-ChNF films indicated that the mechanical properties were improved by adjusting the DA values of the films. For example, the acetylated SD-ChNF film with an 1.84 DA value on surface showed values of 44.1 MPa and 24.9% for tensile strength and elongation at break, respectively.
Citation: Surfaces
PubDate: 2023-07-27
DOI: 10.3390/surfaces6030017
Issue No: Vol. 6, No. 3 (2023)
- Surfaces, Vol. 6, Pages 257-267: Spectra of Low Energy Electrons Emitted
in the Interaction of Slow Ne+ Ions with Mg Surfaces
Authors: Pierfrancesco Riccardi, Catherine A. Dukes
First page: 257
Abstract: We measured spectra of low energy electrons emitted in the interaction of singly charged Ne+ ions with the Mg surface at incident ion energies ranging from 50 eV to 4 keV. The study examines issues related to the excitation of both the surface and the bulk plasmons of the target. We will also focus on the dynamics of the production of the singlet Ne2p4(1D)3s2 and triplet Ne2p4(3P)3s2 autoionizing states of projectiles scattered in a vacuum. The threshold behavior of the autoionization lines show that double excitation occurs simultaneously in a single scattering. The predominant excitation of the triplet state indicates the importance of charge rearrangement and the electron correlation effects during the collisional excitation.
Citation: Surfaces
PubDate: 2023-08-03
DOI: 10.3390/surfaces6030018
Issue No: Vol. 6, No. 3 (2023)
- Surfaces, Vol. 6, Pages 268-280: Biodegradable
Zn−1wt.%Mg(−0.5wt.%Mn) Alloys: Influence of Solidification
Microstructure on Their Corrosion Behavior
Authors: Talita Vida, Clarissa Cruz, André Barros, Noé Cheung, Crystopher Brito, Amauri Garcia
First page: 268
Abstract: The development of biodegradable Zn-based alloys for implants that effectively mimic the functionality of native bone throughout the healing process is a multifaceted challenge; this is particularly evident in the task of achieving appropriate corrosion rates. This work explores the incorporation of 0.5wt.%Mn into a Zn−1wt.%Mg alloy, with focus on the relationship between corrosion behavior and microstructure. Electrochemical corrosion tests were carried out in a 0.06 M NaCl solution using as-solidified samples with two distinct microstructural length scales. Mn addition was found to induce significant electrochemical active behavior. Localized corrosion was predominant in interdendritic regions, with the ternary alloy exhibiting a higher susceptibility. For both alloys, the coarsening of the microstructure promoted a slight inclination to accelerate the corrosion rates in both biodegradable Zn alloys. The corrosion rate showed an increase of about nine-times with Mn addition for coarser eutectic spacings, while for finer ones, the increase was by about 22 times.
Citation: Surfaces
PubDate: 2023-08-11
DOI: 10.3390/surfaces6030019
Issue No: Vol. 6, No. 3 (2023)
- Surfaces, Vol. 6, Pages 281-290: Oxidative Damage during the Operation of
Si(211)-Based Triboelectric Nanogenerators
Authors: Carlos Hurtado, Simone Ciampi
First page: 281
Abstract: Triboelectric nanogenerators (TENGs) based on sliding metal–semiconductor junctions are an emerging technology that can efficiently convert mechanical into electrical energy. These miniature autonomous power sources can output large direct current (DC) densities, but often suffer from limited durability; hence, their practical scope remains uncertain. Herein, through a combination of conductive atomic force microscopy (C-AFM) and photocurrent decay (PCM) experiments, we explored the underlying cause of surface wear during the operation of DC-TENGs. Using monolayer-functionalized Si(211) surfaces as the model system, we demonstrate the extent to which surface damage develops during TENG operation. We reveal that the introduction of surface defects (oxide growth) during TENG operation is not caused by the passage of the rather large current densities (average output of ~2 × 106 A/m2); it is instead mainly caused by the large pressure (~GPa) required for the sliding Schottky diode to output a measurable zero-bias current. We also discovered that the drop in output during operation occurs with a delay in the friction/pressure event, which partially explains why such deterioration of DC-TENG performance is often underestimated or not reported.
Citation: Surfaces
PubDate: 2023-08-21
DOI: 10.3390/surfaces6030020
Issue No: Vol. 6, No. 3 (2023)
- Surfaces, Vol. 6, Pages 291-303: Vapor–Gas Deposition of Polymer
Coatings on Metals from Azeotropic Solutions of Organosilanes
Authors: Yu. B. Makarychev
First page: 291
Abstract: The mechanism of the vapor–gas deposition of vinyltrimethoxysilane (VS) and ethylene glycol (EG) from azeotropic solutions is investigated, which allows a reduction of the evaporation temperature of the components of working mixtures. The need for such studies is associated with the development of a new direction in the technology of vapor–gas deposition of polymer coatings. Methods have been developed for monitoring the chemical composition of working solutions in evaporators using optical spectroscopy, which makes it possible to calculate the partial pressures of vapor-phase components. Based on these studies, compositions of working solutions are proposed that allow the equalization of the partial pressures of the components of working mixtures with a large difference in the boiling point. With the aid of vapor–gas deposition, siloxane coatings on low-carbon steel were obtained, the protective properties of which exceeded the treatment with volatile inhibitors of the adsorption type by two to three orders of magnitude. A new method of vapor–gas deposition of non-volatile powder inhibitors on metals is proposed. Chemical compositions of siloxane coatings were determined using XPS, and mechanisms of interaction of VS with the polymerization promoters ethylene glycol and 1-hydroxy ethylidene-1,1-diphosphonic acid (HEDP) were proposed.
Citation: Surfaces
PubDate: 2023-09-01
DOI: 10.3390/surfaces6030021
Issue No: Vol. 6, No. 3 (2023)
- Surfaces, Vol. 6, Pages 304-315: The Antibacterial Performance of Implant
Coating Made of Vancomycin-Loaded Polymer Material: An In Vitro Study
Authors: Ali Alenezi
First page: 304
Abstract: Bacterial adhesion and biofilm formation on the surface of titanium implants are the main causes of implant-associated infection. An antibacterial coating on the implant surface can reduce the risk of biofilm formation. The aim of this study was to investigate the bactericidal effects of a van-comycin-loaded polymer coated on an implant surface. For this purpose, poly(N-isopropylacrylamide) (PNIPAAm) was first synthesized as a homopolymer or by co-polymerization with acrylamide (PNIPAAm-AAm) at a 5% weight ratio. Then, thin and uniform polymer coatings were prepared using the spin coating technique. The degree of surface hydro-philicity of the polymer coatings was evaluated by measuring the water contact angle (CA). For the antibacterial tests, the polymer-coated surfaces were loaded with vancomycin. The tests were performed in three conditions: on a glass surface (control), on a PNIPAAm-AAm-coated surface, and on a PNIPAAm-AAm-coated surface loaded with vancomycin. The death rates of the bacteria in contact with the coated surfaces were evaluated at different temperatures with fluorescence microscopy. A scanning electron microscopy (SEM) analysis of cross sections of the polymer coatings revealed a uniform thin film of approximately 200 nm in thickness. The water contact angle analysis performed at different temperatures revealed that the polymer-coated surfaces were more hydrophobic (CAs ranging between 53° and 63°) than the uncoated glass surface (CA ranging between 15° and 35°). The bacterial death rate, measured at 40 °C or while continuously switching the temperature between 37 °C and 40 °C, was higher in the presence of the surface coated with vancomycin-loaded PNIPAAm-AAm than when using the other surfaces (p-value ≤ 0.001). The vancomycin-loaded polymer coating evaluated in this study exhibited effective antibacterial properties when the polymer reached the phase transition temperature.
Citation: Surfaces
PubDate: 2023-09-13
DOI: 10.3390/surfaces6030022
Issue No: Vol. 6, No. 3 (2023)
- Surfaces, Vol. 6, Pages 316-340: Porous Carbon for CO2 Capture Technology:
Unveiling Fundamentals and Innovations
Authors: Gazi A. K. M. Rafiqul Bari, Jae-Ho Jeong
First page: 316
Abstract: Porous carbon is an emerging material for the capture of CO2 from point sources of emissions due to its high structural, mechanical, and chemical stability, along with reusability advantages. Currently, research efforts are mainly focused on high- or medium-pressure adsorption, rather than low-pressure or DAC (direct air capture) conditions. Highly porous and functionalized carbon, containing heteroatoms (N, O, etc.), is synthesized using different activation synthesis routes, such as hard template, soft template, and chemical activation, to achieve high CO2 capture efficiency at various temperatures and pressure ranges. Fundamental pore formation mechanisms with different activation routes have been evaluated and explored. Higher porosity alone can be ineffective without the presence of proper saturated diffusion pathways for CO2 transfer. Therefore, it is imperative to emphasize more rational multi-hierarchical macro-/meso-/micro-/super-/ultra-pore design strategies to achieve a higher utilization efficiency of these pores. Moreover, the present research primarily focuses on powder-based hierarchical porous carbon materials, which may reduce the efficiency of the capture performance when shaping the powder into pellets or fixed-bed shapes for applications considered. Therefore, it is imperative to develop a synthesis strategy for pelletized porous carbon and to explore its mechanistic synthesis route and potential for CO2 capture.
Citation: Surfaces
PubDate: 2023-09-18
DOI: 10.3390/surfaces6030023
Issue No: Vol. 6, No. 3 (2023)
- Surfaces, Vol. 6, Pages 114-132: Electrostatic Assembly of Anti-Listeria
Bacteriophages on a Self-Assembled Monolayer of Aminoundecanethiol: Film
Morphology, Charge Transfer Studies, and Infectivity Assays
Authors: Paula M. V. Fernandes, Cláudia Maciel, Paula Teixeira, Carlos M. Pereira, José M. Campiña
First page: 114
Abstract: The integration of bacteriophages, a particular class of viruses that specifically infect bacteria and archaea, in biosensors for the monitoring of pathogens in foods and beverages is highly desirable. To this end, an increasing focus has been set on the exploration of covalent and physical methods for the immobilization of phages on solid surfaces. This work investigates the electrostatic assembly of tailed phages, specifically anti-Listeria monocytogenes P100 phages, on an ultrathin self-assembled monolayer (SAM) of 11-amino-1-undecanethiol (AUT). The cationic properties of AUT may allow for the electrostatic capture of P100 in a capsid-down fashion, thereby exposing the specific receptor-binding proteins on their tails to the corresponding pathogens in the analytical samples. The morphology and charge transfer behavior of the assembled films were studied with atomic force microscopy, scanning electron microscopy and electrochemical techniques. These methods provided valuable insights into the orientation of the phages and the relevant role of the pH. Biological plaque assays revealed that the immobilized phages remain active towards the target bacterium. Overall, this research portrays SAMs of amino-akylthiols as a valid platform for the oriented immobilization of bacteriophages on surfaces for electroanalytical purposes.
Citation: Surfaces
PubDate: 2023-04-07
DOI: 10.3390/surfaces6020009
Issue No: Vol. 6, No. 2 (2023)
- Surfaces, Vol. 6, Pages 133-144: Charged Hybrid Microstructures in
Transparent Thin-Film ITO Traps: Localization and Optical Control
Authors: Dmitrii Shcherbinin, Vadim Rybin, Semyon Rudyi, Aliaksei Dubavik, Sergei Cherevkov, Yuri Rozhdestvensky, Andrei Ivanov
First page: 133
Abstract: In the present study, we propose a new transparent thin-film ITO surface radio-frequency (RF) trap. Charged hybrid microstructures were localized in the developed ITO trap. We show, analytically and experimentally, that the position of the localization zones in the trapped hybrid structure are stable. The transfer of charged particles between localization zones was studied under the action of gravity-compensating laser radiation. We highlight the advantages of transparent thin-film ITO traps to investigate and manipulate charged particles.
Citation: Surfaces
PubDate: 2023-04-19
DOI: 10.3390/surfaces6020010
Issue No: Vol. 6, No. 2 (2023)
- Surfaces, Vol. 6, Pages 145-163: Long-Range ACEO Phenomena in Microfluidic
Channel
Authors: Diganta Dutta, Keifer Smith, Xavier Palmer
First page: 145
Abstract: Microfluidic devices are increasingly utilized in numerous industries, including that of medicine, for their abilities to pump and mix fluid at a microscale. Within these devices, microchannels paired with microelectrodes enable the mixing and transportation of ionized fluid. The ionization process charges the microchannel and manipulates the fluid with an electric field. Although complex in operation at the microscale, microchannels within microfluidic devices are easy to produce and economical. This paper uses simulations to convey helpful insights into the analysis of electrokinetic microfluidic device phenomena. The simulations in this paper use the Navier–Stokes and Poisson Nernst–Planck equations solved using COMSOL to determine the maximum attainable fluid velocity with an electric potential applied to the microchannel and the most suitable frequency or voltage to use for transporting the fluid. Alternating current electroosmosis (ACEO) directs and provides velocity to the ionized fluid. ACEO can also mix the fluid at low frequencies for the purpose of dispersing particles. DC electroosmosis (DCEO) applies voltage along the microchannel to create an electric field that ionizes fluid within the microchannel, making it a cost-effective method for transporting fluid. This paper explores a method for an alternate efficient utilization of microfluidic devices for efficient mixing and transportation of ionized fluid and analyzes the electrokinetic phenomena through simulations using the Navier–Stokes and Poisson Nernst–Planck equations. The results provide insights into the parameters at play for transporting the fluid using alternating current electroosmosis (ACEO) and DC electroosmosis (DCEO).
Citation: Surfaces
PubDate: 2023-04-20
DOI: 10.3390/surfaces6020011
Issue No: Vol. 6, No. 2 (2023)
- Surfaces, Vol. 6, Pages 164-178: Fabrication of Electroplated Nickel
Composite Films Using Cellulose Nanofibers Introduced with Carboxy Groups
as Co-Deposited Materials
Authors: Makoto Iioka, Wataru Kawanabe, Tatsuya Kobayashi, Ikuo Shohji, Kota Sakamoto
First page: 164
Abstract: In this study, the fabrication of nickel (Ni)-cellulose nanofiber (CNF) composite electroplating films was attempted using sodium carboxymethyl cellulose (CMC) and 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)-oxidized CNF as CNF introduced with carboxy groups. As a result, co-deposition was confirmed for both CNFs, and the former showed 82% improvement in surface Vickers hardness compared to the plated film deposited from a conventional Watts bath without CNF. Although the latter showed slightly inferior 71% improvement, the surface roughness measurement showed a smoother surface than that of the plated copper material C1100. On the other hand, the film with CMC had a rough surface. The image analysis showed that the distance between co-deposited CNF on the surface of the plated film was 40% shorter on the specimen with TEMPO CNF than CMC, indicating that a fine dispersion was obtained. In addition, a co-deposition model was proposed in which Ni is deposited from the chelate complex formed between the carboxylate of CNF and Ni ions. CNF is fixed to the plated film surface by Ni deposition and the simultaneous bond of hydrogen ions to the carboxylate, resulting in a return to the carboxy group.
Citation: Surfaces
PubDate: 2023-05-19
DOI: 10.3390/surfaces6020012
Issue No: Vol. 6, No. 2 (2023)
- Surfaces, Vol. 6, Pages 179-213: Surface Treatment of
Biochar—Methods, Surface Analysis and Potential Applications: A
Comprehensive Review
Authors: Marlena Gęca, Ahmed M. Khalil, Mengqi Tang, Arvind K. Bhakta, Youssef Snoussi, Piotr Nowicki, Małgorzata Wiśniewska, Mohamed M. Chehimi
First page: 179
Abstract: In recent years, biochar has emerged as a remarkable biosourced material for addressing global environmental, agricultural, biomedical, and energy challenges. However, the performances of biochar rest in part on finely tuning its surface chemical properties, intended to obtain specific functionalities. In this review, we tackle the surface treatment of biochar with silane and other coupling agents such as diazonium salts, titanates, ionic/non-ionic surfactants, as well as nitrogen-containing (macro)molecules. We summarize the recent progress achieved mostly in the last five years and correlate the nature and extent of functionalization to eye-catchy end applications of the surface-engineered biochar.
Citation: Surfaces
PubDate: 2023-06-02
DOI: 10.3390/surfaces6020013
Issue No: Vol. 6, No. 2 (2023)
- Surfaces, Vol. 6, Pages 214-226: Thin Luminous Tracks of Particles
Released from Electrodes with A Small Radius of Curvature in Pulsed
Nanosecond Discharges in Air and Argon
Authors: Victor F. Tarasenko, Dmitry V. Beloplotov, Alexei N. Panchenko, Dmitry A. Sorokin
First page: 214
Abstract: Features of the nanosecond discharge development in a non-uniform electric field are studied experimentally. High spatial resolution imaging showed that thin luminous tracks of great length with a cross-section of a few microns are observed against the background of discharge glow in air and argon. It has been established that the detected tracks are adjacent to brightly luminous white spots on the electrodes or in the vicinity of these spots, and are associated with the flight of small particles. It is shown that the tracks have various shapes and change from pulse to pulse. The particle tracks may look like curvy or straight lines. In some photos, they can change their direction of movement to the opposite. It was found that the particle’s track abruptly breaks and a bright flash is visible at the break point. The color of the tracks differs from that of the spark leaders, while the bands of the second positive nitrogen system dominate in the plasma emission spectra during the existence of a diffuse discharge. Areas of blue light are visible near the electrodes as well. The development of glow and thin luminous tracks in the gap during its breakdown is revealed using an ICCD camera. Physical reasons for the observed phenomena are discussed.
Citation: Surfaces
PubDate: 2023-06-14
DOI: 10.3390/surfaces6020014
Issue No: Vol. 6, No. 2 (2023)
- Surfaces, Vol. 6, Pages 1: Acknowledgment to the Reviewers of Surfaces in
2022
Authors: Surfaces Editorial Office Surfaces Editorial Office
First page: 1
Abstract: High-quality academic publishing is built on rigorous peer review [...]
Citation: Surfaces
PubDate: 2023-01-18
DOI: 10.3390/surfaces6010001
Issue No: Vol. 6, No. 1 (2023)
- Surfaces, Vol. 6, Pages 2-28: Revisiting Current Trends in Electrode
Assembly and Characterization Methodologies for Biofilm Applications
Authors: Luis Alberto Estudillo-Wong, Claudia Guerrero-Barajas, Jorge Vázquez-Arenas, Nicolas Alonso-Vante
First page: 2
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 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.
Citation: Surfaces
PubDate: 2023-01-18
DOI: 10.3390/surfaces6010002
Issue No: Vol. 6, No. 1 (2023)
- Surfaces, Vol. 6, Pages 29-39: Study on High-Speed Machining of 2219
Aluminum Utilizing Nanoparticle-Enhanced Minimum Quantity Lubrication
(MQL) Technique
Authors: Sagil James, Mehrshad Mazaheri
First page: 29
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 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.
Citation: Surfaces
PubDate: 2023-01-22
DOI: 10.3390/surfaces6010003
Issue No: Vol. 6, No. 1 (2023)
- Surfaces, Vol. 6, Pages 40-52: Nano-and Microparticles of Carbon as a Tool
for Determining the Uniformity of a Diffuse Discharge Exposure
Authors: Mikhail Lomaev, Victor Tarasenko, Mikhail Shulepov, Dmitry Beloplotov, Dmitry Sorokin
First page: 40
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 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.
Citation: Surfaces
PubDate: 2023-02-07
DOI: 10.3390/surfaces6010004
Issue No: Vol. 6, No. 1 (2023)
- Surfaces, Vol. 6, Pages 53-63: In Situ Gas-Phase Polymerization of
Polypyrrole-Coated Lithium-Rich Nanotubes for High-Performance Lithium-Ion
Batteries
Authors: Yangwen Chen, Beibei Sun, Xinchang Wang, Junmin Xu, Liwei Zhang, Jipeng Cheng
First page: 53
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 (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.
Citation: Surfaces
PubDate: 2023-02-22
DOI: 10.3390/surfaces6010005
Issue No: Vol. 6, No. 1 (2023)
- Surfaces, Vol. 6, Pages 64-82: Electron Spectroscopy of Charge Exchange
Effects in Low Energy Ion Scattering at Surfaces: Case Studies of Heavy
Ions at Al Surface
Authors: Pierfrancesco Riccardi
First page: 64
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 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.
Citation: Surfaces
PubDate: 2023-03-02
DOI: 10.3390/surfaces6010006
Issue No: Vol. 6, No. 1 (2023)
- Surfaces, Vol. 6, Pages 83-96: Synthesis, Characterization of Some
Conductive Aromatic Polyamides/Fe3O4 NPs/ITO, and Their Utilization for
Methotrexate Sensing
Authors: Mona A. Abdel-Rahman, Waleed A. El-Said, Eman M. Sayed, Aboel-Magd A. Abdel-Wahab
First page: 83
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, 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.
Citation: Surfaces
PubDate: 2023-03-03
DOI: 10.3390/surfaces6010007
Issue No: Vol. 6, No. 1 (2023)
- Surfaces, Vol. 6, Pages 97-113: Pulsed Current Effect on the Hard
Anodizing of an AlSi10Mg Aluminum Alloy Obtained via Additive
Manufacturing
Authors: Elisa Dallari, Massimiliano Bononi, Annalisa Pola, Marialaura Tocci, Paolo Veronesi, Roberto Giovanardi
First page: 97
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 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.
Citation: Surfaces
PubDate: 2023-03-13
DOI: 10.3390/surfaces6010008
Issue No: Vol. 6, No. 1 (2023)
