Surface Treatment Research Articles

Optimization design of asphalt emulsion with rejuvenator towards a uniform distribution inside the damaged porous asphalt mixture for a better ravelling resistance

Porous asphalt (PA) pavements usually meet the ravelling disease after opening to traffic for several years. Spraying surface treatment (ST) emulsion to PA pavement is a feasible preventive maintenance technology to alleviate this problem. However, the void clogging, nonuniform distribution and low diffusion efficiency of ST residue might hinder its widespread application. Therefore, this study aims to optimize the ST emulsion formula to improve the ravelling resistance of damaged PA. Usages of adding rejuvenators into ST emulsions were discussed. The orthogonal design method was used to determine the appropriate parameter values for preparing rejuvenator emulsions. The viscosity, contact angle and water boiling tests were then conducted to determine the optimal dosage of rejuvenator emulsion within ST emulsion. Cantabro abrasion test was performed to verify the ravelling resistance of damaged PA mixtures treated with optimized ST. Results showed that a stable and homogeneous rejuvenator emulsion could be produced by precisely controlling the PH value, emulsified temperature and emulsifier dosage. Adding rejuvenator emulsions to ST emulsions significantly improved the wettability. The optimal dosages of aromatic oil and tall oil emulsions are 10% and 5% by mass of ST emulsions. Optimized ST containing rejuvenator emulsions showed better ravelling resistances than pure asphalt emulsion.

Experiments on the effect of wall distances for bubble collapse characteristics

At present, the energy released by bubble collapse can be used for the surface treatment of workpieces and can also be used to degrade pollutants. However, the mechanism of action between bubble collapse and a nearby wall has yet to be accurately explained. In order to grasp the relationship between the wall distance and collapse characteristics, the methods of spark discharge, high-speed photography, and pressure acquisition are used to study bubble shapes and the dynamic variation during pressure release with different wall distances in this paper. The results show that with the increasing of the distance L, the shape of a bubble changes from oblate to spherical and its collapse time shortens. The proportion of the total collapse time consumed by the slow collapse stage shows an increasing trend. In an experiment with two contractions, the time proportion of the slow collapse stage of the first contraction is much larger than that of the second contraction. The existence of the wall delays the collapse of the bubble. As the distance L increases, the bubble goes from undergoing one collapse to two collapses and then to one collapse again. The proportion of the duration of the slow collapse stage of the first contraction decreases rapidly, and the proportion of the slow collapse stage of the second contraction increases slowly, but the time proportion of second contraction decreases. When the distance L increases from 4.5 mm to 11 mm, the pressure received by the wall gradually decreases 28.19 MPa to 18.01 MPa. With an increase in the distance S from 0 to 8 mm, the maximum pressure received by the wall gradually decreases from 19.77 MPa to 9.37 MPa. The relationship found between the slow collapse stage (ta), the second contraction (tb), and the distance (L) can provide guidance for the effective application of the energy released by bubble collapse.

Pulsed N2 plasma surface treatment for AlGaN/GaN HEMTs prior to PECVD SiNx passivation to reduce plasma damage

In this work, a pulse-mode N2 plasma surface treatment process was proposed as a means of reducing plasma damage and improving the GaN/GaOx ratio on the surface before SiNx deposition, which further contributes to an enhanced density of 2DEG and a reduced sheet resistance. With the pulsed N2 plasma surface treatment combined with subsequent SiNx passivation, the fabricated GaN HEMTs exhibit negligible current collapse and suppressed leakage current. The improved behavior is attributed to the fact that the pulsed N2 plasma is capable of nitriding the surface and removing carbon contaminants as identified through x-ray photoelectron spectroscopy and energy dispersive x-ray spectroscopy. Compared to the traditional continuous-wave-mode N2 plasma, the pulsed N2 plasma pre-treatment effectively prevents continuous collisions of the plasma during acceleration, thereby significantly reducing plasma damage. This work offers valuable insights for surface treatment processes in micro- and nanofabrication.

Improving Solar Cell Efficiency of Silicon and Silicon Tandem Structure by Using Surface Modification

Silicon heterojunction (SHJ) solar cells face challenges in maximizing energy capture due to limitations in light collection and surface passivation. To address this, the use of SHJ tandem solar cells in a back‐to‐back configuration is explored, allowing illumination from both sides to enhance light absorption and energy generation. This study aims to improve the stability and efficiency of these cells through Al2O3 and Nafion surface treatments. Al2O3 is deposited to enhance bifacial light collection, while Nafion is applied for surface passivation to increase the fill factor (FF). The method involves adding 0.1–0.6 units of incident light to the rear of the cells to evaluate the effects of these treatments. The results show a 2.06% increase in efficiency with Al2O3 and a 1.72% improvement with Nafion under standard illumination conditions. The optimized tandem SHJ with Al2O3 and Nafion achieves a Jsc of 62.01 mA cm−2, Voc of 650.63 mV, FF of 76.49%, and an efficiency of 30.86%. These findings demonstrate the significant potential of these surface treatments to enhance the overall performance of bifacial back‐to‐back tandem SHJ solar cells.

Enhancing enset fiber‐reinforced polylactic acid composites through different surface treatments for emerging applications

AbstractEnvironmental concerns and the over‐exploitation of natural resources have driven the search for eco‐friendly materials. Agro/industrial waste, often discarded, can be repurposed as fillers in biocomposites. However, bio‐fibers present challenges such as poor compatibility, high moisture absorption, and variable mechanical properties. This study examines various fiber surface modification techniques, including NaOH, silane, alkali‐silane, and pectinase enzyme treatments on enset fiber (EF) to produce sustainable reinforced poly(lactic acid) (PLA) composites. Untreated EF/PLA composites were fabricated for comparison. Results showed that the applied EF surface treatments, especially using pectinase enzyme, significantly enhanced mechanical, thermal, and thermomechanical properties. Pectinase‐treated EF/PLA composites displayed increased tensile strength by 55.99%, elongation at the break by 39.49%, tensile modulus by 32.59%, impact strength by 51.50%, flexural strength by 51.85%, flexural modulus by 60.90%, and improved thermal stability as compared to untreated composite. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analyses verified better fiber‐matrix interaction with clarity due to reduced non‐cellulosic components. Pectinase enzyme treatment emerged as the most effective, eco‐friendly method, enhancing the enset fiber's potential in polymer biocomposites, suitable for automotive interiors and packaging industries, reducing synthetic plastic pollution, and utilizing agricultural waste.Highlights Enset fibers were modified by NaOH, silane, NaOH/silane, and pectinase enzyme The modified enset/PLA composites were prepared by compression molding Surface treatments enhanced the enset‐PLA matrix interaction Pectinase‐modified enset/PLA composite showed superior properties Improved properties of enset composites make it ideal for various applications

Preclinical Experimental Study on New Cervical Implant Design to Improve Peri-Implant Tissue Healing

Objectives: In this preclinical study, we used an experimental rabbit model to investigate the effects of a new implant design that involves specific changes to the cervical portion, using a conventional implant design in the control group. Materials and Methods: We used 10 rabbits and 40 dental implants with two different macrogeometries. Two groups were formed (n = 20 per group): the Collo group, wherein implants with the new cervical design were used, which present a concavity (reduction in diameter) in the first 3.5 mm, the portion without surface treatment; the Control group, wherein conical implants with the conventional design were used, with surface treatment throughout the body. All implants were 4 mm in diameter and 10 mm in length. The initial implant stability quotient (ISQ) was measured immediately after the implant insertion (T1) and sample removal (T2 and T3). The animals (n = five animals/time) were euthanized at 3 weeks (T1) and 4 weeks (T2). Histological sections were prepared and the bone–implant contact (BIC%) and tissue area fraction occupancy (TAFO%) percentages were analyzed in the predetermined cervical area; namely, the first 4 mm from the implant platform. Results: The ISQ values showed no statistical differences at T1 and T2 (p = 0.9458 and p = 0.1103, respectively) between the groups. However, at T3, higher values were found for the Collo group (p = 0.0475) than those found for the Control group. The Collo samples presented higher BIC% values than those of the Control group, with statistical differences of p = 0.0009 at 3 weeks and p = 0.0007 at 4 weeks. There were statistical differences in the TAFO% (new bone, medullary spaces, and the collagen matrix) between the groups at each evaluation time (p < 0.001). Conclusions: Considering the limitations of the present preclinical study, the results demonstrate that the new implant design (the Collo group) had higher implant stability (ISQ) values in the samples after 4 weeks of implantation. Furthermore, the histomorphometric BIC% and TAFO% analyses showed that the Collo group had higher values at both measurement times than the Control group did. These findings indicate that changes made to the cervical design of the Collo group implants may benefit the maintenance of peri-implant tissue health.

Advancements in Bamboo-Based Cushioning Material Manufacturing

The study focuses on producing cushioning packaging material from bamboo fibers. The effects of varying the surface treatment duration and the proportions of foaming agents, adhesives, plasticizers, cross-linking agents, and other components were analyzed in terms of foam density, foaming rate, elasticity, and bubble size. The optimal reagents and the ideal ratios for the different components were identified. The parameters for the foaming process were determined based on a high-efficiency, eco-friendly foaming mechanism. Impact testing was conducted to obtain curves for maximum acceleration versus static stress, dynamic stress versus strain, and dynamic buffering factor versus stress. The study examined the dynamic buffering performance as a function of drop height and compared it to other cushioning materials. The findings indicate that at a height of 450 mm, the bamboo pulp product exhibited a lower peak acceleration value than EPE and EPS in the stress range of 2.8-5.4 kPa, indicating superior cushioning performance under these conditions.

Provides Efficient Shear Bond Strength and Durability Between Lithium Disilicate Glass-ceramic and Resin Cement: A Potential Alternative to the Conventional Hydrofluoric Acid Protocal

Objectives: This study investigated the effects of two surface treatment protocols on the shear bond strength, bond durability, and failure mode at the interface between lithium disilicate glass-ceramic and resin cement. The protocols compared were a self-etching ceramic primer and the conventional hydrofluoric acid (HF) etching followed by silane. Methods: Fifty lithium disilicate specimens were randomly divided into five surface treatment groups (n=10 each). A control group received no treatment. The remaining 4groups included: 5% HF etch with Monobond Plus thermocycled and non-thermocycled, Monobond Etch & Prime (MEP), thermocycled and non-thermocycled. Microshear bond strength (microSBS) was assessed before and after thermocycling to evaluate bond durability. Failure modes (adhesive, mixed, cohesive in resin/ceramic) were recorded under a stereomicroscope. Results: Both surface treatment protocols exhibited comparable microSBS for both pre- and post-thermocycling results. Moreover, bone durability obtained from the two treatment protocols seemed to be comparable. Most groups displayed adhesive/mixed failures. Notably, the self-etching ceramic primer group showed cohesive failure in half of the specimens initially, persisting in 20% after thermal aging. Conclusions: Compared with the conventional HF protocol, the self-etching ceramic primer protocol provided similar microSBS and bond durability between lithium disilicate glass-ceramic and resin cement. The data suggest a self-etching ceramic primer is a viable option for the conventional HF protocol in bonding to glass-ceramic, minimizing the HF hazard and simplifying the clinical procedure.

Probing coherence properties of shallow implanted NV snsembles under different oxygen terminations

Abstract Nitrogen vacancy (NV) color centers in diamond have shown great potential for various applications in quantum technology due to their long coherence times, high sensitivity to magnetic fields and atomic scale resolution. However, one major challenge in utilizing near surface NV centers is the decoherence caused by spins and charges fluctuating on the surface, which affects the spin properties of the sensors. To reduce the induced noise, various oxygen surface treatments such as low power oxygen plasma treatment and annealing under oxygen atmosphere have been explored to terminate the diamond surface and reduce its impact on NV coherence. We showed that the NV center's coherence time can be enhanced up to a factor of 3 over a large spectral range of noise. Double electron electron resonance (DEER) measurements revealed an extra source of decoherence, scaling similarly as the P1 spin bath. The improvement in coherence times is accompanied with an increase in measured ketone/ether content and reduction of sp2 signal in X-ray photoelectron spectroscopy (XPS) measurements. Finally we compared the performance of different NV ensembles and surface treatments for sensing external proton spins. The oxygen annealing is an effective procedure of enhancing the spin coherence times and reducing broad band spin noise experienced by shallow implanted ensemble NV centers in diamond.

Structural modification of high carbon Co−Cr−Mo alloy via chemical etching to enhance hydroxyapatite coating performance

AbstractNumerous papers have been reported on surface treatment of metallic implant to facilitate positive interaction between the implant and hard tissue interface. In this paper, surface treatment such as chemical etching was done on the biomedical grade cobalt‐based alloy prior to hydroxyapatite coating deposition to enhance its biocompatibility. The objective is to investigate which temperature possesses the positive effect in adhesion strength of hydroxyapatite coating without detrimental the surface hardness. Observation showed that acid etched at the highest temperature (80 °C) has successfully roughen the substrate surface from 0.168 μm ±0.1 μm to 1.383 μm ±0.2 μm. Vickers hardness measurement on surface treated at 80 °C exhibit an increment of surface hardness which is about 39 % compared to surface treated at lower temperature. The highest thickness of hydroxyapatite coating layer (~57 μm) was evidently formed on the substrate etched at 80 °C with minimal cracks and no delamination. This phenomenon happened due to chemical reaction were rigorously attack on the substrate surface have provide more micro‐pits, pores and deeper craters that trap more efficiently of hydroxyapatite particles for thicker and dense coating formation. It is worth to note that too long acid soaking will also detrimental the material properties.

Wettability of saliva substitutes across various denture base fabrication techniques.

The present study evaluated the contact angles (CAs) of four denture base materials subjected to different surface treatments using deionized water and saliva substitutes. A total of 32 rectangular specimens were manufactured using four different denture base materials: heat-cured compression molded Lucitone 199 (C), milled Lucitone 199 (M), Formlabs Denture Base RP (P), and SR Ivocap High Impact (I). The CA of the surface of the unaltered, mechanically polished, and sandblasted surface specimens was evaluated after the application of five saliva substitutes: Biotene, VEGA, Spry, Moi-Stir, Dentilube, and ionized water. Ten droplet measurements were obtained for each group, with each droplet analyzed for advancing contact angle (ACA), receding contact angle (RCA), and the contact angle hysteresis (CAH) was calculated. The data of the experiment was analyzed using 2-way ANOVA, (α=0.05) with Tukey's test. CAH was demonstrated to have statistically significant differences among the denture bases (p<0.05), with unaltered 3D printed exhibiting the largest CAH, followed by unaltered milled. The unaltered denture bases exhibited higher CAH than the polished, and there were no significant differences in CAH among the polished denture bases (p>0.05). Sandblasting increased the ACA of the milled and conventional bases. The saliva substitutes exhibited differences in ACA, with Spry and VEGA having the highest ACA, and Biotene had the lowest CA of all the saliva substitutes evaluated. The manufacturing methods of denture bases influences the CAH, while the chemical composition of the denture base specimens does not appear to affect CAH. Sandblasting increases the ACA for the milled and conventional groups. Saliva substitutes do impact the ACA. Drawing from previous research, it is hypothesized that a 3D-printed denture base or sandblasting a milled denture base may offer greater resistance to dislodgement.

Assessment of the impact of intensification of heat exchange processes in heaters on power unit efficiency

In various spheres of modern industry, including power engineering, the issue of low efficiency of operation of heatexchange equipment, where condensation of vapour-gas media occurs, is a significant concern. It is known that one of the effective ways of solving this problem is intensification of heat exchange processes by transitioning from the traditional film condensation mode to the droplet condensation mode. A promising and technically straightforward way to achieve the droplet mode of condensation is a method based on the treatment of heat-exchange surfaces using a surfactant – octadecylamine (ODA). The analysis of studies, in which results of experimental research and industrial implementation are given, has shown that application of the specified method in conditions of condensation of water steam promotes formation of a stable droplet mode of condensation; as a result, the heat transfer coefficient on the steam side can more than double.Equally important and interesting is the question of how the efficiency of heat exchangers impacts the overall efficiency of complex systems, in which they operate. In this study, we examined the effect of the operational efficiency of network and regenerative heaters on the energy efficiency and economic performance of a power unit based on steam turbine unit T-110-12,8-3 operating in the heat recovery mode. To this end, we calculated the thermal scheme under various operating conditions of these heat exchangers and determined several key efficiency indicators, including the fuel heat utilisation factor (HUF) and electrical efficiency (EE). It is revealed that intensification of heat-exchange processes by a factor of 2 in horizontal delivery water heaters (HDWH) or in low-pressure heaters (LPH) significantly enhances the efficiency indicators of the power unit as a whole. At the same time, as the analysis of calculation results showed, the greatest benefits are realized when this measure is implemented in HDWH.

In Vitro Wear of Human Enamel Against Monolithic Zirconia After Staining, Glazing and Polishing Treatments.

To evaluate the effect of staining, glazing, and polishing of stabilized zirconia with 5 mol% of yttrium oxide (5Y-TZP) on the wear behavior of opposing tooth enamel. The plane specimens of 5Y-TZP were divided into 6 groups (n = 10), according to surface treatment: as sintered, staining, glazing, polishing, staining followed by glazing, and staining followed by polishing, and positioned against tooth enamel during the two-body wear test (20 N, 2 Hz, until completing 300,000 cycles). The wear rates of tooth enamel were evaluated using a profile projector and a digital pachymeter as a measure of vertical height loss. The data were analyzed by one-way ANOVA and a Tukey post hoc test (α = 0.05). Polishing reduced the vertical height loss (p < 0.001) while there was no difference among other groups. Polishing is recommended as a finishing procedure to reduce the wear rates of tooth enamel, and finishing procedures (glazing or polishing) performed after staining did not affect the vertical height loss of tooth enamel. Polishing is the recommended finishing procedure for preshaded 5Y-TZP to reduce the wear rates of opposing tooth enamel. Staining is applied to the occlusal surface to reproduce the pigmented groove appearance, and glazing or polishing performed after staining did not affect the wear rates of opposing tooth enamel.

Effect of Natural Weathering on the Mechanical Strength of Bamboo Bio-Concrete

The search for solutions that reduce the environmental impact of construction has driven the development of new materials. Bio-concrete represents a significant advance, presenting itself as an alternative to traditional concrete. Recent studies point to durability in outdoor conditions as one of the main challenges in its application. This paper presents natural durability studies performed on bamboo bio-concrete, produced with a bamboo particle volume of 50%. A surface treatment of applying resin externally was tested to reduce water ingress during weathering. The bio-concretes were exposed to natural and outdoor weather conditions for twelve months, and meteorological records were collected during the study period. The effect and influence of the external resin was investigated using visual surface analysis, uniaxial compression, modulus of elasticity and scanning electron microscopy. In terms of visual aspects, the resin was not effective in preventing loss of gloss, while in terms of microstructure, these samples showed better adhesion between the bamboo particles in the matrix. The compressive strength showed significant reductions of 60% (stress) and 73% (Young’s modulus) after twelve months of weathering. External resin could improve microstructures from surfaces to internal portions and more effectively preserve the mechanical strength of bio-concrete.

Digital Workflow Optimization for Endocrown Restorations on Root- Treated Teeth

Endocrown restorations have become a popular solution for endodontically treated teeth, offering both functional and esthetic benefits. These restorations are particularly effective for molars due to the larger surface area of the pulp chamber, which enhances retention and stability. This article presents a clinical case of a zirconia endocrown restoration for a highly damaged mandibular molar. Utilizing a fully digital workflow, the preparation, design, and fabrication of the restoration were performed with precision, ensuring minimal tooth structure removal. Zirconia was chosen for its superior mechanical properties, including fracture resistance and durability. The challenges associated with zirconia, such as bonding reliability, were addressed through surface treatments like air abrasion and the use of 10-MDP-based chemical promoters. The patient’s outcome was both esthetically pleasing and functionally successful. This case highlights the advantages of integrating digital workflows and advanced materials in modern prosthodontic practice, while also acknowledging the need for careful selection of materials and techniques based on the individual case.

Comparison of the effects of laser systems and cold atmospheric plasma on the surface roughness and shear bond strength of flexible hybrid ceramics.

The aim of this study was to compare the effects of laser systems and cold atmospheric plasma (CAP) on the surface roughness (Ra) and shear bond strength (SBS) of flexible hybrid ceramics (FHCs). Eighty FHC samples were divided into 5 groups to be subjected to surface treatments (hydrofluoric acid (HFA), HFA + 5W Er: YAG laser (HFA + 5WE), HFA + 3W Er: YAG laser (HFA + 3WE), HFA + ultrafast fiber laser (HFA + FL), and CAP). The Er: YAG laser (AT Fidelis Plus III, Fotona, Slovenia) was operated with a 0.9mm diameter tip, delivering 250mJ and 150mJ per pulse, with output powers of 5W and 3W, and fluences of 23,623J/cm² and 14,157J/cm², respectively, at a frequency of 20Hz and a pulse duration of 600 µs for 30s. The FL (FiberLAST Inc., Turkey) was applied with a 7mm spot size, 1mJ pulse energy, 20W output power, 100kHz repetition rate, ultrashort pulse length (100 ns), and the fluence of 1,820J/cm² for 7s. The CAP (PiezoBrush PZ3, Relyon Plasma, Germany) applied to the surfaces for 80s at a treatment speed of 5 cm2/s and 100% plasma power. After the Ra values were measured, each group was divided into 2 subgroups to be cemented with total-etch (TE) and self-adhesive (SA) resin cements. The SBS of all the samples was measured. One sample was randomly selected from each group, and the fractured surfaces were examined by SEM analysis. The significance level was at P < 0.05. HFA + FL had the highest Ra values, and there was no significant difference between HFA + FL and HFA + 5WE (P > 0.05). There was no difference in Ra between CAP and HFA (P > 0.05). The highest SBS values were observed for the samples cemented with TE after HFA + FL. The difference between the SBS values of the groups cemented with TE after CAP, HFA + 5WE, HFA + 3WE, and HFA + FL was not significant (P < 0.05). The use of FL may be a promising method to improve SBS without causing thermal damage when using TE or SA cements. CAP can be recommended as a practical and safe treatment with SA cement because it is suitable for chairside use with a handheld device and does not change the physical properties of the material.

IMPACT OF EDGE PREPARATION ON SURFACE FINISHING PROPERTIES

The properties of protective coatings made from organic coatings on metallic substrates strongly depend on the condition of the substrate surface. This refers to the condition of the edges, welds, and the surface in general. Edge treatment is one of the most important operations prior to the actual coating application. The coating's protective properties and its susceptibility to mechanical damage are directly affected by the edge treatment. The article deals with the problem of edge treatment of the base material and the effect of this treatment on the quality of surface finishing. The edges were modified in three ways on the prepared Kosmalt E 300 T samples. Subsequently, some samples were hot-dip galvanized. An organic coating was then applied as the final surface treatment to all samples. The evaluation of the quality of the surface finishing was carried out on the above-mentioned, differently treated edges. The results strongly indicate the importance of the condition of the substrate surface and its influence on the quality of the final surface finish.

Comparative Analysis of Modern 3D-Printed Hybrid Resin-Ceramic Materials for Indirect Restorations: An In Vitro Study

The study investigated the impact of aging on surface roughness, color stability, and biocompatibility of hybrid resin-ceramic materials. A total of 225 specimens were produced from three three-dimensional (3D)-printed (HarzLabs Dental Sand Pro (HL), BEGO VarseoSmile Crown plus (BV), Voco V-Print c&amp;b temp (VV)) and one milled material (Voco Grandio Blocs (VG)). Specimens were grouped into untreated, polished, and glazed surfaces. 5000 thermal cycles simulated aging. Surface roughness and color stability were analyzed, and surface topography was observed using scanning electron microscopy (SEM). Biocompatibility was evaluated with L929 cells. Surface roughness differed significantly between untreated and other groups, with no changes before and after artificial aging. Untreated milled samples were significantly smoother than 3D-printed ones. SEM analysis revealed roughest surfaces in untreated 3D-printed specimens. Polished and glazed specimens were smoother than untreated ones. Color values showed significant differences between untreated and treated/aged groups. No material showed cytotoxicity. In summary, untreated VG was smoother than 3D-printed materials, but polishing and glazing reduced roughness to levels comparable to VG. Surface treatments induced color changes, with glazing causing more changes than polishing. Aging affected color stability and biocompatibility but not surface roughness. All materials showed acceptable color changes and good biocompatibility.

Prediction of the Released Mechanical Energy of Loaded Lap Shear Joints by Acoustic Emission Measurements

In lightweight design, the usage of different optimised materials is widespread. The interfaces between two different materials are prone to damage and, therefore, the Structural Health Monitoring (SHM) of these areas is of interest. A new method for the damage evaluation of joints is developed and validated. The released mechanical energy (RME) during static loading of a metal–composite lap shear joint is considered as a damage assessment parameter and is set into relation to the detected Acoustic Emission (AE) energy. Eleven specimens with identical geometry but different surface treatments are used to form a statistical database for the method, i.e. to calculate the energy ratio and the fluctuation range, and the twelfth specimen is used for the validation of the method. The energy ratio varies significantly, but, considering the fluctuation analysis, the RME with a known range can be predicted on the basis of the AE signal. The whole process is repeated twelve times to validate the methodology. This method can be applied to different geometries and load cases without sophisticated modelling of the damage behaviour. However, load–displacement curves of the pristine joint need to be known, and the monitored joints need to be damage-tolerant and must show similar damage behaviour.

Antimicrobial Surfaces: Stainless Steel Functionalized with the Essential Oil Component Vanillin

Pathogenic microorganisms can adhere to solid surfaces, leading to the formation of biofilms, thus building a physical barrier hindering the penetration and diffusion of antimicrobial compounds. In this context, the use of natural antimicrobial compounds, such as essential oil components, as substitutes for common synthetic antimicrobials in the fight to prevent antimicrobial resistance is explored. As stainless steel is one of the most widely used surfaces in different industries, we have developed an innovative antimicrobial treatment for stainless steel surfaces based on a multi-step functionalization process, in which the stainless steel surface is coated with a silica layer to which a vanillin derivative is covalently attached. The surface was analyzed by microscopy studies, indicating the correct immobilization on the surfaces. Antimicrobial studies (viability and bacterial adhesion assays) were performed against the bacteria Staphylococcus epidermidis, which is one of the most frequent causes of nosocomial infections. The results of the microbiological studies showed that vanillin-functionalized stainless steel surfaces reduce the bacteria viability by 100% and the biofilm formation on the stainless steel surface by 75% compared with non-functionalized surfaces, highlighting the contact-killing and adhesion resistance properties of the developed surface. Additional cycles using the functionalized surfaces showed good maintenance of the antimicrobial coating efficacy. Moreover, the surfaces coated with an intermediate silica layer demonstrated much greater antimicrobial activity than surfaces in which the active molecule was directly functionalized on the stainless steel surface.