Surface Properties Of Materials Research Articles

Theoretical and Experimental Study on Normal Contact Stiffness of Plane Joint Surfaces With Surface Texturing

Effects of surface texturing on normal contact stiffness have been investigated by experiments in previous research studies; however, there are relatively few theoretical models in this regard. This article aims to investigate the influence of surface texturing on the normal contact stiffness in theory and experiment. In the present research, a rough surface with surface texturing is divided into two parts, the textured zone and the remaining zone, and their theoretical models of normal contact stiffness are established respectively, considering surface morphology and material properties. For the textured zone, microtextures are modeled theoretically based on the three-dimensional topographic data obtained via a laser profilometer. For the remaining zone, the surface topography is characterized based on fractal theory, and a calculation model is established considering the elastoplastic deformation of surface asperities. In the experiment, the normal contact stiffness of specimens is obtained through the self-developed experimental platform. The proposed theoretical model is appropriate through the comparison of test results and theoretical predictions. The research results show that the effect of surface texture on the contact stiffness is related to the surface roughness, Sa. For the joint surfaces with Sa > 2.69 μm, the normal contact stiffness can be effectively increased through proper surface texturing.

Main approaches of biofilm formation in composite resins: a concise systematic review

Introduction: Composite resins are widely used in clinical dental practice to restore the structure lost by caries and dental defects, achieving aesthetic and functional results. Failures in the photoactivation process can cause problems in the mechanical resistance to wear in regions of direct occlusal contact on the restorative material. This occurs due to the reduction in the degree of conversion of monomers into polymers, compromising the clinical performance of the composite resin. Polymerization shrinkage leads to microleakage of the restoration, leading to staining and the development of bacterial biofilms. Objective: It was to carry out a systematic review of the main scientific evidence of biofilm formation on composite resin veneers, identifying potential predictors, as well as proposals to mitigate this problem. Methods: The systematic review rules of the PRISMA Platform were followed. The search was carried out from December 2022 to March 2023 in the Scopus, PubMed, Science Direct, Scielo, and Google Scholar databases, using articles from 2015 to 2022. The quality of the studies was based on the GRADE instrument and the risk of bias was analyzed accordingly, according to the Cochrane instrument. Results and Conclusion: A total of 125 articles were found, 25 articles were evaluated and 20 were included and developed in this systematic review study. Considering the Cochrane tool for risk of bias, the overall assessment resulted in 10 studies with a high risk of bias and 70 studies that did not meet GRADE. It was concluded that the surface properties of resin-based composite materials, as well as surface treatments, can strongly affect bacterial adhesion and biofilm formation. In addition, scientific evidence highlights that cariogenic biofilm formation can alter the surface properties of materials, thus stimulating bacterial adhesion and biofilm formation. Photoactivation allows the curing and crosslinking of polymer chains, essential for the clinical longevity of the composite resin. Insufficient photoactivation culminates in marginal microleakage in restorations and biofilm accumulation on surfaces exposed to the oral environment.

Reversible Tuning of Surface Properties of Graphene-like Material via Covalently Functionalized Hydrophobic Layer

Nanoscale tuning of the surface properties of graphene-like materials is essential to optimize their application in electronic devices and protective technologies. The covalent modification method has recently been established as the most effective approach for tailoring the interface structure and properties, which are key aspects for fine-tuning the processability and performance of graphene-like materials. In this work, we demonstrate systematic exploration of the reversible covalent functionalization of a highly oriented pyrolytic graphite (HOPG) surface, a model system of multi-layered graphene, at the molecular scale. This is achieved using 3,5-trifluoromethyl benzenediazonum (3,5-TFD) and experimental investigations via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning tunneling microscopy (STM), and Raman spectroscopy. The degree of functionalization could be tuned by varying the concentration of 3,5-TFD dissolved in the grafting electrolyte. The covalently functionalized layer of 3,5-TFD was either locally degrafted by the STM tip or globally detracted upon thermal treatment, leaving the defect-free graphitic surfaces behind. Our findings open a new pathway for reversibly and robustly functionalizing graphene and other 2D materials for multiple uses in high-end applications.

Beyond hydrophobisation: Deciphering the surprising reactivity of trimethylsilyl reagents towards graphene oxide

Trimethylsilylation of metal oxide surfaces (silica, titania…) is a common way to empower the handled supports with outstanding stability. This hydrophobisation prevailed in vital domains including chromatographic column, adsorption-based membranes and heterogeneous catalysis, where hydrolytic stability constituted a challenging issue. In spite of its benefits, trimethylsilylation of graphene oxide has been only sporadically investigated and this underlooked chemistry needs to be accurately addressed for further tailoring the surface properties of graphene materials. With this aim, we herein screened a set of commercially available trimethylsilyl reagents for end-cuping the surface of graphene oxide. Surprisingly, meticulous investigations show that these reagents behave primarily as nucleophiles and induce oxirane opening, with a diverging pattern depending on the functional group linked to trimethylsilyl fragments. Specifically: i) trimethylsilylchloride and trimethylsilyltriflate are not suitable because of the substantial side products formed under acidic conditions; ii) trimethylsilylimidazolium reacts rather through its imidazolium group with the simultaneous elimination of trimethylsilyl groups; iii) bis-silylated reagents like hexamethyldisilazane and N,O-bis-trimethylsilyl-trifluoroacetamide enable anchoring at least one functional arm while liberating the second trimethylsilyl moity. The introduced functionalities enhance the dispersion of the newly prepared graphenes in liquid medium, thereby broadening the library of solvents suitable for their handling and offering more possibilities for the ink processability. Regardless of the starting reagent, the resulting functionalisation do not compromise the anchoring ability of the graphene surface as illustrated by supporting InP/ZnS semiconductor nanocrystals. In the whole, these serendipitous findings challenge the conventional wisdom about the reactivity of trimethylsilyl reagents that was primarly associated to surface hydrophobisation, opening indeed new possibilities for graphene functionalisation and further use in materials science.

Implementation of endurable superhydrophobic surfaces through dilution rate control of the PDMS coating on micro-nano surface structures

Modifying the wettability of engineering surfaces has been widely practiced for several years because changing the surface properties of materials can induce useful functional properties. Superhydrophobic surfaces with maximized hydrophobicity prevent contamination, freezing, and corrosion, and are usually categorized based on the coating solution used. Among the various coating solutions, polydimethylsiloxane (PDMS) has attracted wide attention because it yields fluorine-free superhydrophobic coatings. Herein, fluorine-free superhydrophobic coatings were fabricated by varying the ratio of PDMS and toluene with respect to their viscosity. The roughness, wettability, and durability of the coatings were measured and described in detail. A simple chemical etching and oxidizing process was used to fabricate micro-nanostructures on the hydrophilic surface before hydrophobic coating. The variance in the morphological structure and surface roughness of the yielded micro-nanostructures in accordance with the viscosity control was analyzed using SEM images and surface roughness values, respectively. To measure the contact angle of the water droplet, coating conditions were derived to realize a superhydrophobic surface with a contact angle of over 150°. Furthermore, these superhydrophobic specimens were tested for durability in saline, acidic, and alkaline solutions. The superhydrophobic specimens showed no sign of degradation in brine for 72 h, and some surfaces showed degradation in HCl and NaOH aqueous solutions.

Antibacterial properties of TiO2 nano coating on food packaging surfaces against Escherichia coli and Salmonella typhimurium

ABSTRACT This work aimed to enhance the surface properties of common food packaging materials (PVC, PS, PET, PVDC) by applying a TiO2 nano thin film coating. Physical and chemical analyses confirmed a well-defined anatase phase film. PET showed the highest antibacterial activity, followed by PVDC, PS, and PVC. After 60 min of UV-A irradiation, E. coli elimination rates were 99.85% (PET), 97.14% (PVDC), 96.5% (PS), and 85.91% (PVC). Similarly, for S. Typhimurium, the respective rates were 97.8% (PET), 83.71% (PVDC), 74.79% (PS), and 68.94% (PVC). Complete eradication of both strains occurred within 120 min (E. coli) and 180 min (S. Typhimurium). Durability testing revealed PET's mass loss of 97 mg/kg after 15 cycles, while PVC had the lowest value of 7 mg/kg. These findings demonstrate that TiO2 thin film-coated substrates effectively inhibit bacteria growth, extending food product shelf life.

Structure control of high-quality TiAlN Monolithic and TiAlN/TiAl multilayer coatings based on filtered cathodic vacuum arc technique

Coating techniques are used to improve the surface properties of materials. The filtered cathodic vacuum arc (FCVA) technology is an effective method to obtain high-quality dense coatings. Through FCVA technology, the contradiction between large thickness (over 10 μm) and compactness of TiAlN ceramic coatings was resolved. In this study, a monolayer TiAlN coating with a thickness of 17.13 μm, which possess a hardness of 34.31 GPa was obtained by the FCVA technology. The toughness of the coating was improved by the multilayer structure design which consists of TiAlN/TiAl. The best H/E and H3/E2 value of multilayer coating reached 2.38 times and 4.83 times higher than that of monolayer coating, and the hardness was only decreased by 15.46% at the same time. The highest critical load of adhesion strength for multilayer coatings reached 89.56 N, which is 1.98 times higher than the monolayer coating (44.24 N). For multilayer coating, the mass loss rate in anti-sand erosion test at high angle with the speed of 90 m/s is as low as 0.537 × 10−4 g/g. The erosion resistance per unit thickness of the multilayer coating reaches 1.9 times higher than that of the monolayer coating. At the same time, the multilayer coating has super wear resistance under oil lubrication environment. There is no obvious wear loss in the harsh reciprocal tribological test for 300 min with a normal load of 20 N and a reciprocating friction frequency of 4 Hz. The TiAlN/TiAl multilayer coating with large thickness and high density has excellent crack resistance and has application prospects in high load environments.

Optimization of Parylene C and Parylene N thin films for use in cellular co-culture and tissue barrier models

Parylene has been used widely used as a coating on medical devices. It has also been used to fabricate thin films and porous membranes upon which to grow cells. Porous membranes are integral components of in vitro tissue barrier and co-culture models, and their interaction with cells and tissues affects the performance and physiological relevance of these model systems. Parylene C and Parylene N are two biocompatible Parylene variants with potential for use in these models, but their effect on cellular behavior is not as well understood as more commonly used cell culture substrates, such as tissue culture treated polystyrene and glass. Here, we use a simple approach for benchtop oxygen plasma treatment and investigate the changes in cell spreading and extracellular matrix deposition as well as the physical and chemical changes in material surface properties. Our results support and build on previous findings of positive effects of plasma treatment on Parylene biocompatibility while showing a more pronounced improvement for Parylene C compared to Parylene N. We measured relatively minor changes in surface roughness following plasma treatments, but significant changes in oxygen concentration at the surface persisted for 7 days and was likely the dominant factor in improving cellular behavior. Overall, this study offers facile and relatively low-cost plasma treatment protocols that provide persistent improvements in cell-substrate interactions on Parylene that match and exceed tissue culture polystyrene.

Characterization of structural and mechanical properties of DLC films deposited on the surface of minute-scale 3D objects: Comparison of PECVD and FCVA deposition technique

Diamond-like carbon (DLC) films have received considerable attention owing to its excellent properties such as high hardness, low friction coefficient, high wear resistance, and chemical inertness. Because DLC film is considered an effective coating to improve the surface properties of materials, these films are used in various applications such as parts for automobile engines, hard disk surfaces, cutting tools and dies, and so on. The structure of the DLC film consists of a mixture of sp2- and sp3-bonded carbon atoms. Among them, the tetrahedral amorphous carbon (ta-C) film is known to be the hardest film owing to its diamond-like structure composed mainly of sp3-bonded carbon atoms. The most common deposition method for synthesizing ta-C is the filtered cathodic vacuum arc (FCVA) method. This method can remove the droplets that are non-ionic neutral species, and a high-quality film can be synthesized. However, the mechanical parts that require ta-C coating have a three-dimensional (3-D) shape, and it is difficult to coat the ta-C film on their entire surface conformity by the FCVA process. In this study, we deposited ta-C on three-dimensional parts by the FCVA method and evaluated the microstructure and surface morphology of the film in comparison with the plasma enhanced chemical vapor deposition (PECVD) method. Films were successfully coated over the entire surface of both millimeter- and nanometer-sized trench patterns. The film properties were investigated by Raman spectroscopy, SEM, nanoindentation tester and transmission electron microscopy.

Crack Surface Analysis of Elastomers Using Transfer Learning.

Cracks that form during fatigue offer critical information regarding the fracture process of the associated material, such as the crack speed, energy dissipation, and material stiffness. Characterization of the surfaces formed after these cracks have propagated through the material can provide important information complementary to other in-depth analyses. However, because of the complex nature of these cracks, their characterization is difficult, and most of the established characterization techniques are inadequate. Recently, Machine Learning techniques are being applied to image-based material science problems in predicting structure-property relations. Convolutional neural networks (CNNs) have proven their capacity on modeling complex and diverse images. The downside of CNNs for supervised learning is that that they require large amounts of training data. One work-around is using a pre-trained model, i.e., transfer learning (TL). However, TL models cannot be used directly without modification. In this paper, to use TL for crack surface feature-property mapping, we propose to prune the pre-trained model to retain the weights of the first several convolutional layers. Those layers are then used to extract relevant underlying features from the microstructural images. Next, principal component analysis (PCA) is used to further reduce the feature dimension. Finally, the extracted crack features together with the temperature effect are correlated with the properties of interest using regression models. The proposed approach is first tested on artificial microstructures created by spectral density function reconstruction. It is then applied to experimental data of silicone rubbers. With the experimental data, two analyses are performed: (i) analysis of the correlation of the crack surface feature and material property and (ii) predictive model for property estimation, whereby the experiments can be potentially replaced altogether.

Strain gradient plasticity phenomenon in surface treated plain carbon steel

Surface engineering is essential for materials being used for functional and structural applications. There have been various approaches and mechanisms used for improving, mechanical, tribological and surface properties of materials over the years. One phenomenon that require much attention is indentation size effect (ISE). Mechanistic and phenomenological theories have been developed to explain the observed size dependence of mechanical properties in materials. However, the dislocations microstructure evolution, deformation mechanisms and the contributions of length scale parameters are not fully understood. This paper explores the effects of surface carbo-nitriding on material length scale and dislocation microstructure mechanisms of 1045 steel. The material was carbo-nitrided at 500 °C and 900 °C, to induce nitrogen and carbon diffusion respectively, prior to, microstructural and mechanical (micro/nano-indentation) characterization. The statistically stored and geometrically necessary dislocation densities increased with increasing carbo-nitriding temperature. A bi-linear relationship was also established based on the indentation depth and hardness measurements. Three regimes of dislocation behaviour (dislocations source–limited/starvation, discrete dislocations, and continuum dislocations) are observed. The observed trends are explained using dislocation densities that were estimated using dislocation theories. The implications of the results are also discussed for the carbonitrided steels.

Effect of Laser Shock Peening on the Stress Corrosion Cracking of 304L Stainless Steel

Storage canisters used in nuclear power plants operating in seaside areas—where the salt content in the atmosphere is high—may be susceptible to chloride-induced stress corrosion cracking (CISCC). Chloride-induced stress corrosion cracking is one of the ways in which dry storage canisters made of stainless steel can degrade. Stress corrosion cracking depends on the microstructure and residual stress, and it is therefore very important to improve the surface properties of materials. Laser shock peening both greatly deforms the material surface and refines grains, and it generates compressive residual stress in the deep part from the surface of the material. This study focused on the effect of laser shock peening on the stress corrosion cracking of 304L stainless steel. The laser shock peening was found to induce compressive residual stress from the surface to a 1 mm depth, and the SCC properties were evaluated by a U-bend test. The results showed that the SCC resistance of laser-peened 304L stainless steel in a chloride environment was enhanced, and that it was closely related to grain size, the pitting potential of the cross section, and residual stress.

Behind the Complex Interplay of Phonation: Investigating Elasticity of Vocal Folds With Pipette Aspiration Technique During Ex Vivo Phonation Experiments

Objectives: The vibration of the vocal folds produces the primary sound for the human speech. The vibration depends mainly on the pressure, airflow of the lungs, and the material properties of the vocal folds. In order to change them, muscles in the larynx stretch the vocal folds. This interplay is rarely investigated, but can give insight in the complex process of speech production. Most material properties studies are damaging the tissue; therefore, a nondestructive one is desired. Methods: An ex vivo phonation experiment combined with the dynamic Pipette Aspiration Technique is used to investigate 10 porcine larynges, under manipulations of different adduction and elongation levels. For each manipulation, the near surface material properties of the vocal folds are measured as well as different phonation parameters like the subglottal pressure, glottal resistance, frequency, and stiffness. Thereby, a high-speed camera was used to record the vocal fold movement. Results: On most of the measured parameters, the manipulations do show an effect. Both manipulations lead to a higher phonation frequency and an increase of the stiffness of the tissue. Comparing both manipulations, the elongation results in higher elasticity values than the adduction. Different measurement parameters have been compared with each other and correlations could be found. Where the strongest correlation are found among the elasticity values of different frequencies. But it can also be seen that the elasticity values correlate with phonation parameters. Conclusion: It was possible to produce a data set of 560 measurements in total. To our knowledge, this is the first time Pipette Aspiration Technique was combined with ex vivo phonation measurements for combined measurements. The amount of measurement data made it possible to carry out statistic investigations. The effect of the manipulations on material properties as well as on phonation parameters could be measured and different correlations could be found. The results lead to the hypothesis that the stretch does not have a huge effect on the material properties of the lamina propria, but more on the underlying muscle.

Plasmon-enhanced Raman scattering of 2D materials via embedded silver nanoparticles in glass

Localized surface plasmon resonance from metallic nanoparticles (NPs) under optical excitation brings out intriguing applications in photonics. We realize plasmon-enhanced Raman scattering of two-dimensional (2D) materials (up to 19 times of magnitude for SnSe2 and 12 times for MoS2) via embedded silver nanoparticles in fused silica glass (hereby Ag NPs:glass), suggesting that the fabricated ion-modified multifunctional substrate shows a good compatibility that couple with 2D nanosheets. Moreover, the existence of insulating layers of SiO2 blocks the direct electron transfer and protects the intrinsic properties of surface materials, the Ag NPs:glass substrate exhibits excellent environmental stability and reusability, maintaining higher enhancement ability after a number of repeated uses. Our work opens up a novel route to develop reusable functional substrates for practical applications toward the weak-signal detection and label-free enhanced Raman scattering.

Insight into the adsorptive removal of ibuprofen using porous carbonaceous materials: A review

Over the last decade, the removal of pharmaceuticals from aquatic bodies has garnered substantial attention from the scientific community. Ibuprofen (IBP), a non-steroidal anti-inflammatory drug, is released into the environment in pharmaceutical waste as well as medical, hospital, and household effluents. Adsorption technology is a highly efficient approach to reduce the IBP in the aquatic environment, particularly at low IBP concentrations. Due to the exceptional surface properties of carbonaceous materials, they are considered ideal adsorbents for the IBP removal of, with high binding capacity. Given the importance of the topic, the adsorptive removal of IBP from effluent using various carbonaceous adsorbents, including activated carbon, biochar, graphene-based materials, and carbon nanostructures, has been compiled and critically reviewed. Furthermore, the adsorption behavior, binding mechanisms, the most effective parameters, thermodynamics, and regeneration methods as well as the cost analysis were comprehensively reviewed for modified and unmodified carbonaceous adsorbents. The compiled studies on the IBP adsorption shows that the IBP uptake of some carbon-based adsorbents is significantly than that of commercial activated carbons. In the future, much attention is needed for practical utilization and upscaling of the research findings to aid the management and sustainability of water resource.

Effects of Smokeless Tobacco on Color Stability and Surface Roughness of 3D-Printed, CAD/CAM-Milled, and Conventional Denture Base Materials: An In Vitro Study

Tobacco consumption in its different forms can affect the optical and surface properties of dental materials that are used in the oral cavity. Thus, the present study was conducted to evaluate the effects of two commercially available smokeless tobacco products on the color stability and surface roughness of denture base resins that were fabricated using three different techniques (CAD/CAM milling, 3D printing, and conventional heat polymerization). A total of 126 denture base resin specimens were fabricated using the three different manufacturing techniques (n = 42 each). Specimens from each group were further subdivided into three subgroups (n = 14 each) and immersed in three different immersion media (a khaini suspension, a tabbaq suspension, and artificial saliva). The differences in color and surface roughness were assessed according to data that were collected and statistically analyzed using SPSS version 24.0. The tabbaq smokeless tobacco was found to cause greatest changes in color and surface roughness; the effect was observed to be highest in the 3D-printed specimens followed by the conventional heat-polymerized and CAD/CAM milled specimens. The mean changes in color and surface roughness were the highest for the tabbaq smokeless tobacco followed by the khaini smokeless tobacco and the artificial saliva. Statistically significant (p-value < 0.05) differences were observed among all techniques and suspensions. We concluded that the mean changes in color and surface roughness were significantly higher for the 3D-printed dentures compared to the conventional heat-polymerized and CAD/CAM-milled dentures. Thus, the results of the present study strengthened the concept that tobacco in any form can lead to changes in the color and surface roughness of denture base materials.

How Effective Is Graphitization of Biomasses for the Carbon Stability of Pt/C ORR Catalysts?

Catalysts for the oxygen reduction reaction (ORR) in PEM fuel cells are commonly constituted of Pt-based nanoparticles and a carbon support originating from fossil resources. In order to employ a more sustainable carbon support, activated sawdust was chosen in this study. This was firstly steam-activated at 750 °C and then thermally treated at elevated temperatures up to 2800 °C and reducing conditions at 1100 °C. Various physical characterization methods were applied to systematically relate treatment parameters to surface and structural properties of the carbon material. Deposition of small Pt nanoparticles on the biochar-based supports yielded in ORR active catalysts which were analyzed by thin-film rotating disc electrode measurements. The activity and stability towards the ORR of these novel catalysts was compared to a commercial raw oil-based Pt/C and the influence of support modification on the ORR performance was discussed.

A Review on Aluminum Matrix Composites Synthesized by FSP

AbstractSurface modification has been emerged out as a novel value addition process to increase the mechanical as well as tribological execution of the engineering materials in the previous decade. Friction stir processing (FSP) has been one of the best and most recent technologies for improving the surface properties of work material. The current study explores a critical review of the fabrication of aluminum matrix composite by incorporating the abrasive type particles through FSP and analyzing the improved mechanical, thermal, and tribological characteristics of the fabricated composite materials. The study will pave the way for opportunities related to surface modification by FSP.

A Review on Fabrication and Application of Tunable Hybrid Micro–Nano Array Surfaces

AbstractThe wettability and adhesion of biological surfaces often depend on their periodically arranged hybrid micro–nano array structures. Various fabrication processes are designed to mimic biomimetic micro–nano array surfaces. This review summarizes the types of micro–nano array structures and analyzes fabrication methods based on top‐down and bottom‐up construction, including templating, etching, self‐assembly, and electrospinning/electrospraying. This review focuses on the shape reconfiguration of surface micro–nano array structures under physical stimuli, as well as the changes in material surface properties during the reconfiguration process. In addition, the applications of biomimetic micro–nano array composite surfaces in the fields of droplet transport, adhesion properties, sensors, and soft robotics are also discussed, and the current challenges and prospects in this field are identified.

Plasma Surface Engineering of Natural and Sustainable Polymeric Derivatives and Their Potential Applications.

Recently, natural as well as synthetic polymers have been receiving significant attention as candidates to replace non-renewable materials. With the exponential developments in the world each day, the collateral damage to the environment is incessant. Increased demands for reducing pollution and energy consumption are the driving force behind the research related to surface-modified natural fibers (NFs), polymers, and various derivatives of them such as natural-fiber-reinforced polymer composites. Natural fibers have received special attention for industrial applications due to their favorable characteristics, such as low cost, abundance, light weight, and biodegradable nature. Even though NFs offer many potential applications, they still face some challenges in terms of durability, strength, and processing. Many of these have been addressed by various surface modification methodologies and compositing with polymers. Among different surface treatment strategies, low-temperature plasma (LTP) surface treatment has recently received special attention for tailoring surface properties of different materials, including NFs and synthetic polymers, without affecting any of the bulk properties of these materials. Hence, it is very important to get an overview of the latest developments in this field. The present article attempts to give an overview of different materials such as NFs, synthetic polymers, and composites. Special attention was placed on the low-temperature plasma-based surface engineering of these materials for diverse applications, which include but are not limited to environmental remediation, packaging, biomedical devices, and sensor development.