Surface Modification Approach Research Articles

Increasing the success rate of interfacial polymerization on hollow fibers by the single-step addition of an intermediate layer

In this paper, we introduce a single-step process that incorporates an intermediate layer on a hollow fiber to enhance the final membrane performance after interfacial polymerization (IP). This intermediate layer is applied during hollow-fiber spinning by complexation of two oppositely charged polyelectrolytes. Specifically, in this study, we consider the IP coating process an experimental success for a membrane sample with a NaCl rejection >85%. The IP success rate is defined as the percentage of the samples with a NaCl rejection of >85% within a studied group. The purpose of the intermediate layer is to increase the success rate of IP on the inner surface of the hollow fibers, typically a challenging task due to the cylindrical shape of the fibers. After the application of IP, the pure water permeance and NaCl rejection of the nascent membranes were tested to determine the success rate of IP. The IP success rate was 86–100% for the hollow fibers (HF) with intermediate layer, significantly higher than the 29% success rate achieved for IP on the support without intermediate layer. This surface modification approach is simple, time-efficient, and effective without any need for post-IP optimization that opens up new avenues for further developments for IP based dense hollow fiber membranes.

Development in Additive Methods in Aramid Fiber Surface Modification to Increase Fiber-Matrix Adhesion: A Review

This review article highlights and summarizes the recent developments in the field of surface modification methods for aramid fibers. Special focus is on methods that create a multifunctional fiber surface by incorporating nanostructures and enabling mechanical interlocking. To give a complete picture of adhesion promotion with aramids, the specific questions related to the challenges in aramid-matrix bonding are also shortly presented. The main discussion of the surface modification approaches is divided into sections according to how material is added to the fiber surface; (1) coating, (2) grafting and (3) growing. To provide a comprehensive view of the most recent developments in the field, other methods with similar outcomes, are also shortly reviewed. To conclude, future trends and insights are discussed.

A Facile and Controllable Approach for Surface Modification of Wool by Micro-dissolution

Most modifications of wool focused on its surface due to the existence of the cuticle scales. For instance, chlorination, oxidation and protease treatments were used to break down or remove the scales. However, these modifications usually severely damaged the internal structure of wool. In this paper, a novel approach based on surface micro-dissolution was employed to modify the surface of wool to minimize the internal damage of wool, and improve the surface-related properties of wool. The micro-dissolution system used NaHSO3/urea to dissolve the scale layer of wool. After being micro-dissolved with NaHSO3/urea system, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), fluorescence microscopy, Fourier transform infrared spectroscopy (FTIR), and the Allworden reaction were utilized to characterize the treated wool. Furthermore, felting shrinkage, strength loss and wettability of the treated wool were determined. The results showed that NaHSO3/urea system could dissolve the scale layer from outside to inside. The fluorescence microscopic images further indicated that low concentration of NaHSO3/urea system can dissolve the surface of wool without the serious damage of internal structure. Moreover, the micro-dissolution system can be controlled to dissolve the scale layer on the surface of wool slightly by adjusting the reaction conditions. The presented method is simple, easy to operate, and economical, thereby can open up new directions for the surface modification of wool.

Surface modification approaches for prevention of implant associated infections

In this highlight, we summarize the surface modification approaches for development of infection-resistant coatings for biomedical devices and implants. We discuss the relevant key and highly cited research that have been published over the last five years which report the generation of infection-resistant coatings. An important strategy utilized to prevent bacterial adhesion and biofilm formation on device/implant surface is anti-adhesive protein repellant polymeric coatings based on polymer brushes or highly hydrated hydrogel networks. Further, the attachment of antimicrobial agents that can efficiently kill bacteria on the surface while also prevent bacterial adhesion on the surface is also investigated. Other approaches include the incorporation of antimicrobial agents to the surface coating resulting in a depot of bactericides which can be released on-demand or with time to prevent bacterial colonization on the surface that kill the adhered bacteria on the surface to make surface infection resistant.

DFT Study on Atomic Layer Deposition of Cerium Dioxide on Hydroxylated Titanium Dioxide As Efficient Photocatalyst

Design of photocatalyst materials for hydrogen production is of great interest due to a lack of cost-effective candidates. Titanium dioxide (TiO2) is a well-known photocatalyst with good stability, reasonable photoactivity, and low cost. To improve the efficiency and selectivity, we apply a surface modification approaches using nanostructured Cerium dioxide (CeO2) deposited onto TiO2 by atomic layer deposition (ALD). The deposition of CeO2 onto TiO2 uses the precursor Tetrakis(2,2,6,6-tetramethyl-3,5-heptanedionato)cerium (IV) (Ce(TMHD)4) and co-reactant ozone.The atomic layer deposition (ALD) of CeO2 on TiO2 was carried out by experiments with an atmospheric pressure fluidized bed ALD reactor. The TiO2 substrate was pre-treated using a combination of ozone and humidified nitrogen flow pulses to investigate the effect of the increase of surface functional groups on CeO2 deposition. The physicochemical properties of the obtained CeO2/TiO2 photocatalysts were characterized using different methods and their photocatalytic activity was evaluated during photocatalytic hydrogen evolution reaction.We have also performed density functional theory (DFT) calculations to investigate the reaction mechanism of metal precursors Ce(TMHD)4 and tris(methylcyclopentadienyl)cerium (III) (Ce(MeCp)3) on hydroxylated rutile and anatase TiO2 surfaces. The hydroxyl saturation coverage on different TiO2 facets was first addressed. These facets include anatase a-TiO2(001) and a-TiO2(101) and rutile r-TiO2(100) and r-TiO2(110). Hydroxyl groups OH and H are initially binding to surface Ti and O atoms, respectively. On a-TiO2(001) hydroxyl recombination to form water results in a final coverage of 0.81ML, due to the shortest neighboring HO-H distance on all surfaces. The Gibbs energy is then calculated to elucidate the effect of pressure and temperature on the hydroxylated termination of TiO2 surfaces. The final hydroxyl coverage is as follows: 0.81ML on a-TiO2(001) surface, 1ML on a-TiO2(101) and r-TiO2(100) surfaces, and 0.75ML on r-TiO2(110) surface.Two precursors (Ce(TMHD)4 and Ce(MeCp)3) are adsorbed on hydroxylated TiO2 surfaces. After precursor adsorption and relaxation, the surface hydroxyl coverage changes with water formation. After Ce(THMD)4 adsorbed on r-TiO2(100) surface, the hydroxyl coverage is decreased from 1ML to 0.25ML with 12 H2O molecules formation. After Ce(MeCp)3 adsorbed on a-TiO2(101) surface, although the hydroxyl coverage is not changed, the hydroxyl orientation is modified, breaking the symmetry. For Ce(TMHD)4, direct ligand dissociation is applied to study the mechanism of eliminating the ligands. For Ce(MeCp)3, the ligand can be eliminated by hydrogen transfer. The barrier for hydrogen transfer is calculated using climbing image nudged elastic band (CI-NEB) method. The results show that for Ce(MeCp)3, the reaction is endothermic on a-TiO2(101) surface, but it is overall exothermic on the other three surfaces. The facets play an important role in the eliminating the ligand. We present DFT results on the activity of ceria-modified rutile TiO2 towards water dissociation and CO2 activation showing that this heterostructured catalyst can promote both reactions. This work will be important to reveal the mechanism and feasibility of atomic layer deposition of ceria on different TiO2 surface facets.

Substrate Independent Liquid Phase Epitaxy of HKUST‐1 as Anticoagulant and Antimicrobial Coating

AbstractThe effective deposition of metal–organic frameworks on kinds of biomaterials is still challenging and highly desirable. Using polydopamine as the effective nucleation center, HKUST‐1 is successfully prepared on three kinds of inert biomaterials, i.e., titanium oxide film (Ti–O), 316L stainless steel (316L SS), and poly(vinyl chloride) (PVC). Characterization of the surfaces by powder X‐ray diffraction confirm the oriented crystal growth of HKUST‐1 on the polydopamine coated substrates. There are no significant difference in catalytical NO generation and surface copper content of the three samples with HKUST‐1 deposition. All keep a NO release speed of ≈2.5 × 10−10 mol cm−2 min−1, thus platelet activation on the HKUST‐1 modified surfaces are inhibited compared to that of the unmodified ones. Ex vivo test shows thrombi formation is dramatically reduced. The HKUST‐1 coated surfaces elicit 95% reduction in the bacterial attachment of both Staphylococcus aureus and Escherichia coli. The endothelial cells and macrophages culture results support good biocompatibility of the modified surfaces. It provides a promising, facile, and effective approach for surface modification of blood contact biomaterials.

Multiscale Structure Construction by Layer-by-Layer Self-Assembly to Modify the Carbon Fiber Surface

Graphene oxide/silica (GO/SiO2) multilayers could be successfully deposited onto a carbon fiber (CF) surface via a convenient and efficient layer-by-layer (LbL) self-assembly approach. It is possible to assemble GO with negative charge and SiO2 with positive charge on the CF surface by virtue of electrostatic interactions, as well as to systematically characterize CF surface microstructures. Scanning electron microscopy (SEM) detects the compact and uniform adherence of GO/SiO2 multilayers to the surfaces of CFs. The coverage contributes to an obvious improvement on the surface energy and roughness of fibers; thus, the wettability exhibited by the CF surface is enhanced. In addition, following GO/SiO2 LbL assembly, the tensile strength exhibited by single fibers increases in the range 2.99–3.21 GPa. As discovered by our work, this kind of approach serves as a promising surface modification approach to optimize the wettability as well as the mechanical property owned by CFs.

Functionalized Polyelectrolytes for Bioengineered Interfaces and Biosensing Applications

The possibility of tuning the chemical moieties and their density plays a fundamental role in targeting surface-confined molecular structures and their functionalities at macro and nanoscale levels. Such interfacial control is crucial for engineered coating formation and biorecognition purposes, where the type and density of ligands/receptors at the surface affect the overall binding affinities and the device performance. Together with the well-established self-assembled monolayers, a surface modification approach based on polyelectrolytes (PEs) has gained importance to provide desired characteristics at the substrate interface. This review presents the innovations of functional PEs, modified in a preceding synthetic step, and their wide applicability in functional (a)biotic substrates. Examples of 2D and 3D architectures made by modified PEs are reviewed in relation with the reactive groups grafted to the PE backbones. The main focus lies on the strategy to use modified PEs to form bioengineered coatings for orthogonally anchoring biological entities, manufacturing biocidal/antifouling films, and their combinations in functional biosensing applications.

Recent Advances in the Synthesis, Surface Modifications and Applications of Core‐Shell Magnetic Mesoporous Silica Nanospheres

The hierarchically structured core-shell magnetic mesoporous silica nanospheres (Mag-MSNs) have attracted extensive attention, particularly in studies involving reliable preparations and diverse applications of the multifunctional nanomaterials in multi-disciplinary fields. Intriguingly, Mag-MSNs have been prepared with well-designed synthesis strategies and used as adsorbent materials, biomedicines, and in proteomics and catalysis due to their excellent magnetic responsiveness, enormous specific surface area and readiness for surface modifications. Through a carefully designed surface modification of Mag-MSNs, the performance and application prospects of the material are greatly improved. Typically, the introduction of various molecular matrices into the shell of Mag-MSNs facilitates the combination of surface modifications and magnetic separation technology. So far, as sustainable chemistry is concerned, it is important to recover the functionalized core-shell Mag-MSNs after the reaction and reuse them without losing activity. In this review, the design conceptions and the construction of core-shell Mag-MSNs are discussed. Furthermore, various surface modification approaches of core-shell Mag-MSNs are summarized, and recent applications of these functionalized nanomaterials in the fields of biomedicine, catalysis, proteomics and wastewater treatment are exemplified.

Activated Carbon Derived from Phoenix dactylifera (Palm Tree) and Decorated with MnO2 Nanoparticles for Enhanced Hybrid Capacitive Deionization Electrodes

AbstractIn this study, the electro‐sorption capacity and selectivity of activated carbon (AC) electrodes, produced from the leaf base of Phoenix dactylifera (palm tree) waste, are modified by enabling the reversible intercalation/conversion of sodium ions through the presence of nanoscale α‐MnO2 particles acting as redox mediators. The α‐MnO2 nanoparticles (NPs) are hydrothermally grown on the AC powder to obtain a functional composite material (α‐MnO2/f‐AC). The morphological, textural, and physicochemical surface properties of the pristine and modified AC materials are thoroughly examined and correlated with the electrochemical performance of the resulting electrodes that are implemented in an asymmetric capacitive deionization (CDI) cell configuration (i. e. capacitive vs Faradaic electrodes). The pristine biowaste‐derived AC presents a high specific surface area of 1224 m2 g−1, and high electrical capacitance of 259 F g−1 at 10 mV s−1. The α‐MnO2 surface modification approach of the pristine material retains its large accessible surface area, and additionally enables a 50% increase in its specific capacitance value. The incorporation of the α‐MnO2/f‐AC material in the anode and the pristine source in the cathode produces superior electrosorption capacity, as high as 17.8mgg−1 in batch‐mode CDI tests with 600mg L−1 NaCl feed. The enhanced electrical performance and pseudocapacitive behavior of the CDI cell can be explained by the α‐MnO2 nanoparticles playing a critical role in enabling a synergistic redox‐based charge‐discharge pathway under conditions compatible with the voltage operation requirements of the CDI process.

Design of Ultra-Thin PEO/PDMAEMA Polymer Coatings for Tunable Protein Adsorption.

Protein adsorption on solid surfaces provides either beneficial or adverse outcomes, depending on the application. Therefore, the desire to predict, control, and regulate protein adsorption on different surfaces is a major concern in the field of biomaterials. The most widely used surface modification approach to prevent or limit protein adsorption is based on the use of poly (ethylene oxide) (PEO). On the other hand, the amount of protein adsorbed on poly(2-(dimethylamine)ethyl methacrylate) (PDMAEMA) coatings can be regulated by the pH and ionic strength of the medium. In this work, ultra-thin PEO/PDMAEMA coatings were designed from solutions with different ratios of PEO to PDMAEMA, and different molar masses of PEO, to reversibly adsorb and desorb human serum albumin (HSA), human fibrinogen (Fb), lysozyme (Lys), and avidine (Av), four very different proteins in terms of size, shape, and isoelectric points. X-ray photoelectron spectroscopy (XPS), quartz crystal microbalance (QCM), and atomic force microscopy (AFM) were used to characterize the mixed polymer coatings, revealing the presence of both polymers in the layers, in variable proportions according to the chosen parameters. Protein adsorption at pH 7.4 and salt concentrations of 10−3 M was monitored by QCM. Lys and Av did not adsorb on the homo-coatings and the mixed coatings. The amount of HSA and Fb adsorbed decreased with increasing the PEO ratio or its molar mass in a grafting solution. It was demonstrated that HSA and Fb, which were adsorbed at pH 7.4 and at an ionic strength of 10−3 M, can be fully desorbed by rinsing with a sodium chloride solution at pH 9.0 and ionic strength 0.15 M from the mixed PEO5/PDMAEMA coatings with PEO/PDMAEMA mass ratios of 70/30, and 50/50, respectively. The results demonstrate that mixed PEO/PDMAEMA coatings allow protein adsorption to be finely tuned on solid surfaces.

Surface modification of poly(tetrafluoroethylene) and poly(ethylene terephthalate) films via environmental crazing

AbstractThis work addresses the phenomenon of the development of a patterned surface relief on polymer films via different modes of environmental crazing. Commercial films of semicrystalline poly(tetrafluoroethylene) (PTFE) and amorphous glassy poly(ethylene terephthalate) (PET) were subjected to tensile drawing in the presence of physically active liquid environments (carbon tetrachloride or aliphatic alcohols). The structure parameters and wettability of the modified films were studied by AFM, SEM, profilometer measurements and contact angle measurements. Environmental intercrystallite crazing of PTFE is accompanied by the development of an unstable structure with a high free surface, which experiences marked strain recovery upon unloading. As a result of the relief formation, PTFE hydrophobicity is enhanced (the water contact angle increases by 25°). Classical environmental crazing of PET films is accompanied by the formation of an anisotropic surface relief which is an assembly of crazes oriented perpendicular to the direction of tensile drawing, thus leading to the phenomenon of anisotropic wetting. The proposed approach for structural surface modification makes it possible to use the advantages of surface instability and spontaneous self‐organization of the polymer towards the development of a unique surface microrelief. © 2020 Society of Chemical Industry

A New Approach in Surface Modification and Surface Hardening of Aluminum Alloys Using Friction Stir Process: Cu-Reinforced AA5083.

In the current study, a new approach for surface modification and surface hardening of aluminum alloys is developed. The method is based on the logic of in-situ reinforcing FSP strategies. The novelty of the proposed process is the application of a bulk reinforcing metallic material instead of metallic powders. The FSP was carried out on aluminum alloy AA5083—thick plates. A thin sheet of pure copper (cross-section 4 × 0.8 mm2) was placed in a machined groove on the upper surface of the aluminum plate, and both materials were FSPed together. Samples with one, two and three FSP passes were manufactured respectively. Results indicate that the copper thin sheet was successfully integrated in the AA5083 stir zone. By increasing the FSP passes, almost all copper was integrated in the stir zone, mainly in the form of coper-based micron-sized intermetallic particles, and secondly, by copper diffusion in the AA5083 matrix. Due to the presence of complex intermetallic compounds created by the high heat input and intense plastic deformation, the hardness inside the stir-zone was found highly increased from 77 to 138 HV.

Regulating Surface and Grain-Boundary Structures of Ni-Rich Layered Cathodes for Ultrahigh Cycle Stability.

The wide applications of Ni-rich LiNi1- x-y Cox Mny O2 cathodes are severely limited by capacity fading and voltage fading during the cycling process resulting from the pulverization of particles, interfacial side reactions, and phase transformation. The canonical surface modification approach can improve the stability to a certain extent; however, it fails to resolve the key bottlenecks. The preparation of Li(Ni0.4 Co0.2 Mn0.4 )1- x Tix O2 on the surface of LiNi0.8 Co0.1 Mn0.1 O2 particles with a coprecipitation method is reported. After sintering, Ti diffuses into the interior and mainly distributes along surface and grain boundaries. A strong surface and grain boundary strengthening are simultaneously achieved. The pristine particles are fully pulverized into first particles due to mechanical instability and high strains, which results in serious capacity fading. In contrast, the strong surface and the grain boundary strengthening can maintain the structural integrity, and therefore significantly improve the cycle stability. A general and simple strategy for the design of high-performance Ni-rich LiNi1- x - y Cox Mny O2 cathode is provided and is applicable to surface modification and grain-boundary regulation of other advanced cathodes for batteries.

The use of low-temperature plasma in a combined technology for the formation of wear-resistant boron-containing coatings

Combined technologies based on the use of concentrated energy fluxes, including low-temperature plasma and a pulsed electron beam, is currently considered to be an effective approach for surface modification of metals and alloys, cermet and ceramic materials. The purpose of the paper is to identify and analyze the patterns of changes in the elemental and phase composition, the state of the defective substructure, and mechanical properties of industrial steel Gr1J03502 subjected to combined treatment that includes plasma deposition of a powder coating based on the Ni-Cr-B-Si system and irradiation with an intense pulsed electron beam. The results obtained by optimizing the mode of the substrate surface fusion and the mode of powder deposition onto the molten surface of the substrate using low-temperature plasma generators of the original design are presented. It has been found that the optimum melting mode of the substrate surface is implemented with the following parameters of the plant: the feed rate is Vп = 50 … 150 mm/min, the distance is h1 = 30…100 mm, the scanning frequency is ω = 50 min−1, β = 75 … 90°, the amplitude is 90 … 100 mm, the plasmatron voltage is 160 V, the current strength is Im = 100 … 120 А. The optimal spraying conditions of the powders are as follows: h1 = 30÷50 mm; h2 = 100÷120 mm; β = 75÷90°; α = 45÷50°; ω = 50 min−1; Um = 140÷160 В; IS = 350÷400A; Im = 80÷100 A; GH (sprayed powder consumption) 0.8÷1 g/s. The characteristics of a plasma jet generated by an electric arc plasmatron are presented. The parameters of the electron beam are as follows: the energy of accelerated electrons is 18 keV, the energy density of the electron beam is 20 J/cm2 and 40 J/cm2, the pulse duration of the electron beam is 200 μs, the pulse repetition rate is 0.3 s−1, and the number of pulses is 10. It has been shown that plasma spraying of a powder coating leads to formation of a high relief surface containing micro and macropores, microcracks, and particles of the sprayed powder. Subsequent treatment of the modified surface with an intense pulsed electron beam of a submillisecond duration in the melting mode of the surface layer is accompanied by smoothing of the coating surface, saturation of the crystalline lattice of the steel surface with Ni, Cr, B, and Si atoms, formation of submicron-sized dendritic crystallization cells, precipitation of nanosized particles of the second phase, and formation of a quenching (martensitic) steel structure. Together, these transformations of the structure and phase composition of the material have led to a multiple increase in the microhardness of the surface layer with a thickness of up to 1500 mm.

Suppressing Voltage Fading of Li‐Rich Oxide Cathode via Building a Well‐Protected and Partially‐Protonated Surface by Polyacrylic Acid Binder for Cycle‐Stable Li‐Ion Batteries

AbstractLi‐rich manganese based oxides (LRMOs) are considered an attractive high‐capacity cathode for advanced Li‐ion batteries; however, their poor cyclability and gradual voltage fading have hindered their practical applications. Herein, an efficient and facile strategy is proposed to stabilize the lattice structure of LRMOs by surface modification of polyacrylic acid (PAA). The PAA‐coated LRMO electrode exhibits only 104 mV of the voltage fading after 100 cycles and 88% capacity retention over 500 cycles. The structural stability is attributed to the carboxyl groups in PAA chains reacting with oxygen species on the surface of LRMO to form a uniform and tightly coated film, which significantly suppresses the dissolution of transition metal elements from the cathode materials into the electrolyte. Importantly, a H+/Li+ exchange reaction takes place between the LRMO and PAA, generating a proton‐doped surface layer. Density functional theory calculations and experimental evidence demonstrates that the H+ ions in the surface lattice efficiently inhibit the migration of transition metal ions, leading to a stabilized lattice structure. This surface modification approach may provide a new route to building a stable Li‐rich oxide cathode with high capacity retention and low voltage fading for practical Li‐ion battery applications.

Sol–gel-based coatings for oxidation protection of TiAl alloys

The low density, high specific strength, and good creep properties make TiAl alloys being promising high-temperature structural materials in aerospace and automotive industries. However, the insufficient oxidation resistance limits their extensive practical applications . It is the intention of this review to illustrate the mechanism and development of sol–gel-based coatings, a surface modification approach for oxidation protection of TiAl alloys, but not to present a general review on the oxidation protection of TiAl alloys. The oxidation behavior and mechanism of TiAl alloys were addressed briefly. The discussion focused mainly on the sol–gel coatings preparation method and generation mechanism. Finally, the development trend of sol–gel-based coatings for high-temperature oxidation of TiAl alloys was prospected.

Facile Oxidation Approach to Amend Surface Chemistry of Carbon Particles for Augmented Dispersion in Epoxy Matrix

Surface chemistry of carbon black (CB) plays a major role towards its dispersion in liquid media. In this study a simple approach of surface modification has been implemented on two different types of particles to increase their dispersion in polymer matrix. FTIR, XPS, DLS, and TGA analyses have been utilized to categorize as well as compare surface functionalities before and after treatment for both types of CBs. As a result of surface oxidative treatment enhanced dispersion of modified CB particles in epoxy monomer along with rise in conductivity has been observed.

Inhibition of bacterial growth on zirconia abutment with a helium cold atmospheric plasma jet treatment.

This study presents a surface modification method to treat the zirconia implant abutment materials using a helium cold atmospheric plasma (CAP) jet in order to evaluate its efficacy on oral bacteria adhesion and growth. Yttrium-Stabilized Zirconia disks were subjected to helium CAP treatment; after the treatment, zirconia surface was evaluated using scanning electron microscopy, a contact angle measuring device, X-ray photoelectron spectroscopy for surface characteristics. The response of Streptococcus mutans and Porphyromonas gingivalis on treated surface was evaluated by a scanning electron microscopy, MTT assay, and LIVE/DEAD staining. The biofilm formation was analyzed using a crystal violet assay. After the helium CAP jet treatment, the zirconia surface chemistry has been changed while the surface topography remains unchanged, the bacterial growth was inhibited, and the biofilm forming decreased. As the treatment time increases, the zirconia abutment showed a better bacterial inhibition efficacy. The helium CAP jet surface modification approach can eliminate bacterial growth on zirconia surface with surface chemistry change, while surface topography remained. Soft tissue seal around dental implant abutment plays a crucial role in maintaining long-term success. However, it is weaker than periodontal barriers and vulnerable to bacterial invasion. CAP has a potential prospect for improving soft tissue seal around the zirconia abutment, therefore providing better esthetics and most of all, prevent peri-implant lesions from happening.

Enhancement of Electrochemical Performance of Lithium and Manganese-Rich Cathode Materials via Thermal Treatment with SO2

In this study, we present a novel surface modification approach via SO2 gas treatment at 200 °C–400 °C to enhance the electrochemical performance of Li and Mn-rich cathode materials 0.35Li2MnO3·0.65LiNi0.35Mn0.45Co0.20O2 (HE-NCM) for advanced lithium-ion batteries. It was established by X-ray photoelectron spectroscopy that the SO2 treatment leads to the formation of surface sulfates and sulfites on the material, while the bulk remains unaffected, as confirmed by X-ray and electron diffraction studies. Based on the results obtained, we proposed possible mechanisms of the SO2 thermal treatment that include partial reduction of manganese (however, we could not find any substantial evidence for it in the XPS data) and oxidation of sulfur. The electrochemical performance was evaluated by testing the materials as cathodes in coin-type half-cells with metallic lithium anodes at 25 °C and 30 °C. The main findings are as follows: the SO2-treated materials demonstrate ∼10% higher capacity at all C-rates and lower the voltage hysteresis during prolonged cycling compared to the untreated samples. The proposed approach to modify the surface of HE-NCM materials by SO2 treatment is demonstrated to be a promising method to enhance the electrochemical performance of these cathodes.