Papers by Keyword: Surface Modification

Abstract: Titanium and its alloys are considered the gold standard for bone contact implants due to their suitable mechanical properties and biological performances. However, their long-term performance remains impaired, mainly due to insufficient integration with surrounding tissues and infections. To overcome these problems, several strategies, particularly coatings, are explored. However, certain drawbacks remain such as lack of adhesion or low mechanical resistance. Among these coatings, diamond-like carbon (DLC) has emerged as a promising material due to its superior mechanical and tribological properties, chemical inertness and stability. In addition, the microstructure of DLC allows the incorporation of other species such as antibacterial agents (Ag, ZnO, etc.), leading to multifunctional protective coating. However, due to the high intrinsic stresses of DLC compared to the native oxide layer, the adhesion of DLC to metallic surfaces remains rather low. Therefore, in order to overcome adhesion issues, this work investigates the impact of different pretreatments, namely etching, carburization or both, on the adhesion of DLC deposited by plasma-assisted chemical vapor deposition, on titanium substrates. The results showed that carburizing 10 min was the most promising pretreatment for improving the DLC adhesion on Ti surfaces. Furthermore, the DLC coating appeared stable even after 7 days of aging in pseudo-physiological conditions, making the process promising for improving Ti implants.

Abstract: This study investigates the chemical characteristics of Eco Processed Pozzolan (ePP) and its surface modification with N, N-dimethyl dodecyl amine (oePP) at varying temperatures of 30°C, 40°C, and 50°C. Comprehensive analysis, including Fourier-transform infrared (FTIR), Field Emission Scanning Electron Microscopy (SEM), and X-ray diffraction (XRD) were employed to examine the structural, compositional, and morphological changes in ePP and oePP samples. The FTIR results revealed significant alterations in the functional groups of the modified samples, particularly in regions corresponding to alkyl and silanol groups after surface modification of ePP. XRD patterns demonstrated variations in crystallinity index, with values of 14.89%, 28.23%, 11.75%, and 15.89% for oePP at 50°C, 40°C, 30°C, and ePP, respectively. Peak analysis showed distinct differences in the crystalline phases present in each sample. FESEM images revealed enhanced surface morphology and increased particle agglomeration in the modified samples, especially at 40°C. The findings demonstrate that oePP exhibits significant potential for various applications owing to its enhanced adsorption properties, surface morphology, and structural stability.

Abstract: Desalination plays a crucial role in addressing global water scarcity by providing a reliable source of freshwater from seawater and brackish water, supporting both human consumption and industrial needs. Feed spacers are an essential component of membrane systems, enhancing mixing and mass transfer. However, they also facilitate foulant deposition, with biofouling often initiating on the spacer surface before spreading to the membrane. Biofouling poses a significant challenge as it is difficult to remove once occurred. In response, extensive research has explored modifying feed spacer surfaces to mitigate fouling. Despite advancements, the use of hazardous chemical reagents in conventional spacer coatings raises serious environmental concerns, including contamination of the food chain and potential risks to human health. This review focuses on eco-friendly spacer coating strategies for biofouling resistance, emphasizing sustainable methods to address the environmental impacts of traditional approaches. Techniques such as plasma pretreatment, direct coating, oil-infused coatings, and candle-soot coatings have shown potential in reducing biofouling by modifying surface properties, including hydrophilicity, hydrophobicity, and biocidal characteristics. These methods have proven effective in mitigating membrane fouling, thereby improving the performance and lifespan of membrane systems. Finally, the paper outlines future research directions, including experimental and numerical approaches, to enhance spacer coatings for antifouling in membrane applications.

Abstract: Atmospheric pressure plasma modifies the surface properties of materials while preserving their bulk characteristics. Here, we show how an oxygen helium atmospheric pressure plasma can increase surface energy of 330 series stainless steel, a material used in biomedical and industrial applications. Plasma treatment was done with a commercial atmospheric pressure plasma reactor. Optical Emission Spectroscopy was performed to assess relative concentrations of plasma species present. In addition to demonstrating the effectiveness of this surface treatment approach, our results show that the increase in hydrophilicity is proportional to the concentration of reactive oxygen species present in the plasma suggesting that these species are important to the treatment process. Keywords: Surface modification; cold plasma; Reactive Oxygen Species

Abstract: Advanced phase-change materials (PCMs), as novel energy-storage technologies, offer a practical solution to addressing the global energy crisis by improving both energy efficiency and sustainability. In this study, silica (SiO₂)-shelled phase-change microcapsules functionalized with carboxylated carbon nanotubes (CNTs) were designed and prepared to enhance thermal conductivity, photothermal conversion, and operational durability. The silica shell, featuring a Janus structure with exterior amine groups, facilitates covalent bonding with CNTs, effectively increasing thermal transfer and maintaining structural integrity. The as-prepared PCMs are characterized by an encapsulation efficiency exceeding 66% and a phase-change enthalpy over 120 J/g, besides the enhanced thermal conductivity, solar thermal conversion, and profound resistance to leakage. Long-term stability tests reveal that the SiO₂-shelled phase-change microcapsules coated with CNTs (S0/CNTs) maintain thermal performance after 100 heating-cooling cycles, showing sustained reliability. These advantages highlight the potential of S0/CNTs in sustainable thermal energy storage applications, offering a versatile solution for enhancing the efficiency and durability of energy storage systems.

Abstract: This study investigates an enhancement of carbon-based materials, including multi-walled carbon nanotubes (MWCNTs) and graphite, through Ion Assisted Reaction (IAR) and metal nanoparticle deposition using Physical Vapor Deposition. The IAR process employed Ar⁺ ion beams in reactive gas environments, effectively introducing hydrophilic functional groups such as hydroxyl (-OH) and carboxyl (-COOH) on the MWCNT surfaces. This modification significantly improved dispersion behavior of the treated MWCNTs, particularly in non-polar solvents like N-Methyl-2-pyrrolidone (NMP). Results indicated that the treated MWCNTs demonstrated a slower sedimentation rate compared to untreated samples, with enhanced stability over 120 minutes in NMP. Graphite was modified with copper nanoparticles on its surface using magnetron sputtering in PVD system, leading to a uniform distribution of the modified graphite in matrix. SEM analysis revealed that this modification enhanced the surface roughness of the graphite, facilitating stronger interfacial adhesion with polymer epoxy resin. Composites incorporating these nanoparticle-coated graphite fillers (NPP graphite) exhibited superior thermal and mechanical properties. For instance, a 15% increment in thermal conductivity was observed in epoxy resin composites containing NPP graphite compared to those with untreated graphite. This improvement was attributed to the metallic Cu nanoparticles acting as thermal bridges, effectively transferring heat within the composite matrix. Mechanical properties were evaluated by blending modified fillers into polymer matrices, including polyvinyl chloride (PVC) and polyethylene (PE), with filler concentrations varying from 5 vol% to 15 vol%. Tensile testing and SEM analysis of the fractured surfaces indicated that NPP graphite composites achieved uniform dispersion, reduced agglomeration, and improved interfacial bonding. This study demonstrates that physical surface modification techniques such as IAR and PVD effectively overcome limitations associated with conventional chemical methods. This approach not only improves the dispersion and interfacial adhesion of carbon-based fillers but also enhances their thermal and mechanical performance.

Abstract: Polystyrene (PS) is widely used in industries like packaging and insulation, but its performance can be enhanced by incorporating calcium carbonate as a filler. To improve polymer-filler compatibility, calcium carbonate was surface-modified with oleic acid, and PS-calcium carbonate composites were synthesized using the melt blending method, followed by citric acid treatment. X-ray diffraction (XRD) and FTIR analyses revealed no chemical interaction between the phases, with a reduction in calcium carbonate content due to citric acid treatment, suggesting partial dissolution of the filler. Scanning electron microscopy (SEM) images showed the formation of cavities in the matrix, especially in TPS3. Hardness testing indicated a decrease in hardness with increasing oleic acid concentration, with TPS3 exhibiting the lowest hardness (63.4 Shore D). Photoluminescence measurements showed a blue shift at lower oleic acid concentrations, while higher concentrations caused a red shift and broader emission, which was stabilized by citric acid treatment. Solvent absorption tests indicated that citric acid-treated composites had an enhanced absorption capacity, with TPS3 showing 38.3 % absorption in vegetable oil, suggesting potential for adsorption applications. Overall, the oleic acid and citric acid treatments significantly modified the mechanical, morphological, and optical properties of PS-calcium carbonate composites, creating tunable materials with potential for sensing applications.

Abstract: Current research on biodegradable iron-based alloys mainly focuses at regulating the material degradation rate, as well as its biological behavior, especially from the point of view of the hemocompatibility and cytocompatibility. In fact, fine-tuning of the surface roughness, morphology and chemical composition can improve the functional response of the material. For that purpose, a surface modification strategy, namely plasma immersion ion implantation (PIII), is proposed to perform the selective modification of surface properties without affecting the bulk ones. In this work, the influence of treatment time (t_imp = 15, 60 and 120 min.) and implanted species (O, N or C) on the surface properties of a Fe-13Mn-1.2C resorbable alloy was investigated. The findings demonstrated that varying the process gas and the exposition time led to a variety of topographies, surface energies and chemical compositions. XPS analyses and depth profiles clearly showed the impact of the process parameters on the surface features and element distribution, due to implanted species penetration into the alloy. The implanted samples showed a delayed clotting time, thus a better hemocompatibility. In contrast, nitrogen-treated surfaces displayed a more pronounced hemolytic behavior, whereas oxygen and methane did not. PIII implantation appears to be a versatile solution for fine-tuning surface topography, composition and biological properties, making the process promising for the improvement of metallic biodegradable vascular implants.

Abstract: Considering its very good mechanical properties, especially the high strength and toughness, and also its well-known case-hardening ability, the AMS 6265 (9310 VAR) low alloy steel is widely used in the aeronautical industry for manufacturing heavy-duty products and parts, like pinions, shafts, gears, piston pins, and other critical aircraft components. In this study, a surface modification treatment via shot peening method was applied to an initially case-hardened (quenched and carburized) AMS 6265 aircraft steel. In shot peening, the mechanical properties of the surface layer are improved, by generating plastically deformed micro-areas when exposing the metal surface to a stream of steel, glass, or ceramic shots. The initial case-hardened AMS 6265 alloy steel and all surface treated samples were structurally investigated by means of OM (optical microscopy), SEM-BSE (scanning electron microscopy – backscattered electrons imaging), and XRD (X-Ray diffraction) analysis, being also mechanically tested in tensile and microhardness tests. The influence of different shot peening parameters (shot size, peening pressure, and exposure time) on mechanical properties evolution and microstructural features, for the analyzed AMS 6265 alloy steel, was established in this present research.

Abstract: The objective of the presented research is to improve the ballistic performance of para-aramid woven fabric by deposition of graphene coatings directly on woven textile substrates. The improvement of mechanical properties of the ballistic fabric is attributed to the formation of a highly ordered layered structure and the efficient load transfer between the fabric fibers and the graphene nanosheets. The results of deposition of layered graphene coatings on woven textiles are discussed here. The pristine graphite directly subjected to a solvent treatment in this work, which resulted in the production of exfoliated graphene sheets in the form of a dispersion that allow immediate utilization obtained dispersion for deposition on the para-aramid samples. In order to prepare the dispersion, graphite flakes were first dispersed into liquid media followed by graphite intercalation (division into microlayers) and nano-layers exfoliation. Dipolar aprotic organic solvent DMAc (N,N-Dimethylacetamide) and Cyrene (Dihydrolevoglucosenone) as a bio-based alternative for dipolar aprotic solvents were used as main components of liquid media. At the final stage, a stable dispersion of isolated flakes by using two types of liquid medium was obtained. To study the effects of dip coating and rolling parameters, six kinds of samples with different pull-out speeds and compression ratios were prepared, and their functional properties were measured and compared.