Comparison of feldspathic veneer surface treatments on colour stability after debonding of orthodontic brackets: An in vitro study.

Surface morphology strongly influences the performance and durability of concrete structures, yet the combined effects of mechanical preparation and measurement scale remain insufficiently quantified. This study analyzes three surface conditions, patched, ground, and shot-blasted, using 3D laser scanning measurements acquired at five spatial resolutions. Mechanical surface preparation was found to be the dominant factor shaping morphology: grinding reduced amplitude- and volume-related parameters by approximately 40–70%, while shot blasting increased them by 50–90%, producing highly textured surfaces with an expanded developed area. Measurement resolution additionally affected parameter magnitudes, with coarser sampling intervals reducing scale-sensitive descriptors such as Sdr and Sdq by more than 80–90%. In contrast, parameters including Ssk, Sku, Smr1, and Smr2 varied by less than 5% across scales, demonstrating strong robustness. Patched surfaces exhibited the largest variability (coefficients of variation often exceeding 20–30%) due to manual finishing, whereas mechanically treated surfaces showed more uniform profiles. These quantitative results highlight the coupled influence of preparation method and measurement scale and provide practical guidance for reproducible surface characterization in engineering and material research.

Electrochemical nucleation and growth (EN&G) are essential to optimize nanostructure electrodeposition methods, specifically these where a precise control of the size, composition and structure is paramount [1]. Despite extensive studies, a comprehensive mechanistic understanding remains elusive. This is due to the random nature of initiation events (nucleation), the heterogeneity of surfaces and (very) fast kinetics across several length scales. Consequently, establishing precise correlations between local surface properties, electrochemical driving force, and nucleation events remains challenging [2].This process is typically studied using electrochemical characterization combined with ex-situ (post-mortem) analysis of the resulting deposits. When performed on TEM-compatible substrates, this standard approach has provided valuable insights into non-classical growth pathways—key to controlling the size, shape, and composition of nanostructured materials [3]. However, it falls short in capturing the effects of surface heterogeneity, as well as the dynamic processes occurring before, during, and after nucleation.In recent years, our group has addressed these challenges by integrating high-throughput local electrochemistry via SECCM with ex-situ/in-situ electron microscopy and data-centric analysis to study metal nucleation on carbon surfaces [4–5]. This method allows the measurement of electrochemical data corresponding to the growth of a limited number of nanoparticles (NPs) and a direct 1-to-1 correlation with the properties of the deposit.In this contribution, we first show how both overpotential and surface state significantly influence the probability of nucleation. The dispersion in nucleation kinetics evolves with overpotential and surface preparation. Our derived analytical model successfully fits experimental current transients, revealing an excellent correlation between the number of active sites inferred from the model and the number of nanoparticles observed by FESEM. [6] This approach allows us to introduce a distribution-based framework to quantify the variability of nucleation and growth rates across the surface. The latter allows linking local activity with macroscopic responses, offering a pathway to integrate stochastic and deterministic aspects of EN&G.Second, we extend this approach by automatically electrodepositing arrays of alloy NPs onto TEM-compatible working electrodes. To extract the maximum information from these large datasets, automated data analysis is used based on (unsupervised) machine learning approaches [7]. This includes dimensionality reduction by principal component analysis, dynamical time warping or K-means clustering of electrochemical signals (e.g. cyclic voltammetry and chronoamperometry curves), particle detection, as well as correlation between the electrochemical and surface datasets. Furthermore, we demonstrate here that an automated and unbiased approach is a valuable tool to differentiate between intrinsic (potential, scan rate) and external/uncontrolled experimental factors influencing NPs nucleation and growth.

GaN power transistors have emerged as a promising solution for high-power (>1kV) and high-frequency (>100 kHz) applications due to GaN’s material properties, including wide bandgap (3.4eV), high critical electric field (3.3 MV/cm) and an electron saturation rate which is 2.8 times that of silicon [1]. Both vertical and lateral power transistor configurations require a MIS gate structure, which includes the deposition of a dielectric layer, most often Al2O3. However, the performance of these devices is significantly influenced by the quality of the dielectric/GaN interface and the choice of gate dielectric [2].For this reason, surface preparation is critical to minimize interface trap density by reducing defects and impurities prior to dielectric deposition, and thus enhancing electrical performance and stability. The search for an effective surface treatment method, whether wet or dry, has been the focus of several studies [3]. However, many factors were not taken into consideration, such as the re-oxidation of GaN prior to dielectric deposition, the dependence of interface quality on the nature of the dielectric and its thickness, hence the need for an in-situ approach that treats interface and dielectric quality in a non-separate way.In this study, we first focus on in-situ atomic layer cleaning of the GaN surface using different plasma atmospheres (NH3, Ar, H2, N2) to investigate their impact on the interface under the same conditions with a reference dielectric Al2O3. Secondly, we explore the integration of an ALD-ternary high-K dielectric, AlSiO, through two approaches, both conducted without an air break to preserve the benefits of plasma cleaning. The approaches are either multilayer mode (Al2O3/SiO2) or mixed mode.To assess interface quality and dielectric performance, MOS capacitors (MOSCAPs) are fabricated. Their characterization is conducted through capacitance-voltage (C-V) and current-voltage (I-V) measurements, complemented by hard X-ray photoelectron spectroscopy (HAXPES).Our goal is to achieve a lower hysteresis (ΔVFB) < 50 mV and a flat band voltage (VFB) shifting towards 0V for the Al2O3/GaN interface and positive values for the AlSiO/GaN interface. Our results demonstrate significant improvements in ΔVFB. Among the different plasma cleaning atmospheres tested, NH3/N2 plasma treatment at low power was selected as the optimal choice, offering a balance between minimizing ΔVFB and achieving a VFB close to 0V.This was followed by the deposition of AlSiO with a low-silicon matrix, the comparison between the effectiveness of both approaches (Mixed and multilayer) is still ongoing .These process conditions will be further used for 200mm vertical power transistors to investigate their impact on device performance.[1] Catherine Langpoklakpam et al., « Vertical GaN MOSFET Power Devices », Micromachines 14, no 10 (octobre 2023): 1937, https://doi.org/10.3390/mi14101937.[2] Anthony Calzolaro, Thomas Mikolajick, et Andre Wachowiak, « Status of Aluminum Oxide Gate Dielectric Technology for Insulated-Gate GaN-Based Devices », Materials 15, no 3 (janvier 2022): 791, https://doi.org/10.3390/ma15030791.[3] Yutao Cai et al., « Effect of Surface Treatment on Electrical Properties of GaN Metal–Insulator–Semiconductor Devices with Al2O3 Gate Dielectric », Japanese Journal of Applied Physics 59, no 4 (mars 2020): 041001, https://doi.org/10.35848/1347-4065/ab7863.

In recent years, the automotive industry has experienced increasing demand for advanced paint protection solutions aimed at improving vehicle durability, preserving aesthetic appeal, and promoting environmental sustainability. This paper critically examines the main categories of paint protection coatings on wax, ceramic, graphene, and hybrid formulations by focusing on their chemical composition, application methods, protective performance, and limitations. Wax coatings remain widely adopted due to their affordability and ease of use, though they offer limited longevity. Ceramic coatings, in contrast, provide superior hardness, hydrophobicity, and resistance to scratches, corrosion, and ultraviolet (UV) degradation, albeit with higher costs and complex application procedures. Emerging graphene-based coatings demonstrate exceptional hydrophobicity, thermal stability, and durability, positioning them as potential next-generation solutions, though their environmental and economic feasibility remains under exploration. Hybrid and self-healing coatings further highlight the trend toward multifunctional, intelligent protection systems. This work also emphasizes the critical role of surface preparation in determining coating performance. Future research directions are outlined, including the development of biodegradable, zero-VOC, and intelligent self-aligning coatings, which could significantly advance sustainable automotive surface protection. Overall, this work provides a comprehensive synthesis of current technologies and identifies pathways for innovation in automotive paint protection materials.

The deposition characteristics of coatings on a titanium alloy substrate were compared using two alternative surface preparation methods: Hollow Cathode Spaces (HCSs) and Ion Bombardment (IB). After deposition of ZrN coatings, the wear resistance of the samples increased by 50–70% compared to uncoated samples, while the HCS method provided 30% higher wear resistance than the IB method. Coated samples deposited using the HCS and IB methods demonstrated very similar friction coefficient values, with a slight (10–15%) decrease in this parameter for the HCS samples. Varying the bias voltage on the substrate (−900, −1200, and −1500 V) when using the HCS method significantly affected wear resistance. The calculated optimal value of the bias voltage when using the HCS method is −1126 V. During the pre-treatment of the substrate using the HCS and IB methods, a transition layer can be formed in the area of the coating–substrate interface; the thickness of this layer varies within the range of 15–400 nm, and the composition is a mixture of coating (zirconium) and substrate (titanium, aluminum, and vanadium) materials.

The present study aims at improving coatings to allow higher operating temperatures – up to 700 °C – while resisting hot corrosion in future heat transfer fluids and storage systems for CSP technology. An aluminide coating was produced onto a 347H austenitic alloy to resist Li-Na-K molten carbonate corrosion at 700 °C. Multiple surface preparations were investigated and, after optimization, a new diffusion heat treatment was selected. A homogeneous 3-layer coating was formed with Al content reaching up to 69 at.% at the top surface. Corrosion was significantly decreased by the coating compared to the uncoated material. After 500h-exposure, a 100 µm-thick multi-layered and non-adhesive alkali elements rich oxide formed at the surface of uncoated 347H alloy. On the contrary, the coated material preserved its morphology and a mix of α-LiAlO2 and γ-LiAlO2 formed on the top coating. From the mechanical perspective, local hardness measurements highlighted a broad variation along the different layers of the coating. 3-point bending tests showed that deformation in the plastic domain was required to cause crack formation. Cracks remained in the two outermost layers of the coating and did not reach the underneath substrate.

Purpose This paper aims to demonstrate an accessible and affordable technique for fabricating complementary split ring resonator (CSRR) frequency selective surfaces (FSS) using common desktop additive manufacturing technologies and commercially available conductive paint, overcoming the cost and time barriers often associated with conventional metamaterial fabrication. Design/methodology/approach CSRR structures targeting the 2.4 GHz band were designed, simulated using electromagnetic modeling software and fabricated via fused deposition modeling (FDM) with polylactic acid and stereolithography (SLA) with ClearV5 resin. Commercially available silver conductive paint was applied to the surfaces of the 3D printed parts to achieve electrical conductivity, leveraging the skin effect. The frequency responses (transmission S21, reflection S11) of the resulting FSS were experimentally characterized using a vector network analyzer from 1.8 to 3 GHz and compared with simulation results. Findings Both FDM and SLA fabricated CSRRs successfully exhibited the expected band-pass filtering behavior near the target frequency, validating the fabrication approach. SLA samples showed excellent agreement with simulated resonant frequency (2.39 GHz) and required minimal post-processing, but demonstrated lower peak transmittance (40.4%) due to higher material absorbance (58.8%). FDM samples required surface preparation (sanding/priming) for paint adhesion and exhibited a slight frequency shift (−30 MHz), yet achieved higher peak transmittance (46.0%). Discrepancies from ideal simulated performance are attributed to inherent material losses, printing inaccuracies and conductive coating quality. Originality/value This paper presents a validated low-cost and rapid methodology for producing functional microwave FSS using readily available desktop additive manufacturing equipment. It significantly contributes by demonstrating the direct fabrication of the resonant metamaterial structures themselves via additive manufacturing and conductive coating, rather than limiting additive manufacturing to nonconductive substrates or supports.

Wire Arc Additive Manufacturing (WAAM) is a versatile and sustainable manufacturing technique for producing titanium components, with promising applications in sectors such as jewelry and interior design. WAAM technology offers advantages such as high deposition rates and efficient material usage. However, it often leads to the formation of thermal oxide layers and an alpha case on the surface, which can adversely affect mechanical properties and hinder coating adhesion. This study explores the effectiveness of environmentally sustainable chemical machining treatments based on oxalic acid and oxalic-ascorbic acid solutions for the surface preparation of WAAM-fabricated Ti6Al4V components before gold Physical Vapor Deposition (PVD). Samples were fabricated without inert atmosphere protection to minimize environmental impact. Treatments were performed at 60 °C, 75 °C, and 90 °C, and their effects on surface characteristics were evaluated through thickness loss measurements, roughness analysis, and elemental composition assessment. Conventional hydrofluoric-nitric acid treatments achieved complete oxide and alpha case removal within one hour. In contrast, organic treatments required 24 h at 90 °C to achieve similar results, with the addition of ascorbic acid accelerating the process. Organic treatments resulted in distinct surface morphologies, characterized by increased roughness, beneficial for coating adhesion. The deposited gold layer had a thickness of 198 ± 5 nm, as determined through X-ray fluorescence analysis. The results of the tape test indicated that coatings applied to samples treated with organic acids exhibited excellent adhesion, while those deposited on samples subjected to conventional treatments experienced delamination exceeding 65%.

Unlike steel bars, there are currently no standards for surface preparation of Glass Fibre Reinforced Polymer (GFRP) bars. As a result, a variety of GFRP bars are commercially available, such as sand coated (SC), helically wrapped (HW), grooved, ribbed, and helically wrapped-sand coated (HW-SC) bars, among others. On the other hand, the load transfer mechanism is sensitive to the surface configuration employed. Therefore, in order to examine the impact of surface configurations on the bond performance of GFRP bar in geopolymer concrete (GPC), two different surface configuration types such as grooves and HW ribs were taken into account in the present investigation. At the same time, an examination was conducted to determine the optimum groove configuration. When comparing HW bond specimens, the pullout capacity of 16 mm grooved specimens was the same, while that of 12 mm grooved specimens was significantly reduced. As the depth of the groove increases, a tendency to increasing and decreasing bond strength was observed for the grooved specimens. Increased groove spacing resulted in a slight increase in bond strength and stiffness. The failure mode for 12 mm specimens remains unchanged even for deeper depths and larger groove spacing, but split failure was observed for 16 mm specimens even for the lowest groove depth and spacing. The post-peak measurements showed that the bond stress-slip response of grooved specimens exhibited ductility due to successive breaking of groove segments, which the HW specimens did not show. Additionally, there were slight improvements in bond strength and stiffness with an increase in concrete grade for HW and grooved specimens. Analytical models and results from experiments compared; the CMR model performed better than the mBPE model. The study recommends using a groove depth of 9% and groove spacing equal to the diameter of the bar since they produced better results.

Preparation of Superhydrophobic Corrosion-Resistant Surface by Etching Method

In this research work, a novel underwater laser surface texturing process has been introduced for improving the adhesive bonding strength of carbon fiber reinforced plastics (CFRP). Joining carbon fiber reinforced plastic (CFRP) sheets is a major challenge for many applications, including hydrogen tanks, aerospace systems, and automotives. Adhesive-based joining is not only simple but also has widespread applications. Surface preparation techniques play an important role in the adhesive joining of two components. In this research work, a nanosecond fiber laser was used to create three different types of textures (line, honeycomb, and grid) on 2.5 mm thick CFRP sheets before the application of adhesives. Textured samples were joined using epoxy-based adhesives, and joint strength was evaluated. The effect of the texturing environment (open air and static water) and texture design on joint strength was determined using lap shear strength tests. The fiber exposure, surface contact angle, roughness, and morphology of each sample were evaluated using a goniometer, confocal microscope, optical microscope, and scanning electron microscope. One-way ANOVA was performed using the Minitab software package to assess the statistical significance of laser surface texturing patterns and processing environments on key performance metrics. Fiber exposure in a sample was quantified and categorized into moderate, considerable, and complete exposure. Failed surfaces were examined to identify the type of failure. Finally, correlation based analysis of surface output parameters and adhesive bonding strength were performed. Surfaces prepared in water-assisted conditions had the highest strength in the case of grid texturing. In comparison, open-air processing produced the highest strength for honeycomb and line pattern designs. Overall, grid textures in water-assisted conditions resulted in the highest bonding strength.

The structural integrity of adhesively bonded composites is critically dependent on manufacturing process fidelity. While the MGS L418 epoxy system is widely used in aerospace applications, a quantitative hierarchy of its process variables is absent from the literature, leading to reliance on qualitative guidelines and inherent performance variability. This study closes this gap through a comprehensive sensitivity analysis. A 26-2 fractional factorial Design of Experiments (DOE) quantified the effects of six variables on single-lap shear strength. An Analysis of Variance (ANOVA) established a definitive hierarchy: induction time was the dominant factor, with a sub-optimal 15 min period causing a 74% strength reduction (p &lt; 0.000). Surface preparation was the second most significant factor, with mechanical abrasion increasing strength by 17% (p = 0.000). Ambient humidity was a marginal factor (p = 0.013), linked to amine blush formation. The interaction effects were statistically insignificant, simplifying the control strategy. This work provides a validated, quantitative model that defines a robust process window, prioritizing induction time and surface preparation to de-risk manufacturing and ensure the reliability of safety-critical bonded structures.

This paper presents the impact of the initial surface finish of commonly used AISI 304 stainless steel on its corrosion resistance before and after being treated with laser radiation. Three distinct surface preparations were examined: brushed, 2B cold-rolled, and polished. All samples were irradiated using a Yb3+:glass laser system of nanosecond pulse duration in an air environment. As a result of laser irradiation, thin oxide layers were formed on the steel surface. Our previous work showed that these layers may significantly increase the corrosion resistance of cold-rolled stainless steel compared to untreated samples. This work expands upon these findings by exploring the effect of laser irradiation on brushed and polished surfaces, keeping the steel’s chemical composition the same so we could focus mainly on how the surface finish influences corrosion. The results demonstrate that the corrosion behavior is correlated with surface roughness and yet modified by laser-induced oxidation. For brushed and cold-rolled samples, the corrosion current density reached a minimum at a laser fluence of 40 J/cm2, corresponding to the highest polarization resistance. Meanwhile, polished samples (which have the lowest initial roughness) did not show much improvement after irradiation. The conducted studies showed a significant influence of surface roughness on corrosion and a change in this resistance as a result of laser annealing of the surface.

Non-thermal plasma treatment to optimize surface preparation for SEM-EBSD investigations of graphite in ductile cast iron

In this prospective clinical study, the safety and performance of the Lupin Robotic System in tooth preparation for veneer procedures in adult patients have been investigated. A total of 12 patients (52 teeth treated from 2 teeth to 6 anterior teeth) were fully treated with Lupin Robotic System performing minimally invasive tooth preparation for laminate veneers. The tooth prep was scanned and compared with the ideal planned tooth prep. The teeth prepared in this current study were classified as Minimally invasive preparation (MIP) or Non-Minimally invasive preparation (NP) by the investigating dentist following criteria based on the state of the art of minimal preparation methods. The methodology is well described in the literature, but may be summarized as: Enamel surface preservation / dentine exposure; preparation margins clarity; tooth preparation which respects convexity; homogenous space between the prepared tooth and final design (i.e. appropriate thickness of the veneer); presence of butt margin at the incisal edge. Each criteria has to be met to define a tooth as MIP. Safety was assessed through the collection of number and frequency of occurrence of all Adverse Events, including the D evice Deficiencies (DDs) that might have led to a safety event and DDs that do not lead to a safety event. The Root Mean Square (RMS) errors between the planned and the actual tooth surface preparations demonstrated high reproducibility of the robotic system. The RMS errors centered around 0.15 mm, with a range from 0.04 mm to 0.26 mm. These findings suggest accurate adherence to the pre-defined milling plan. The maximum error (MaxError) observed across the dataset indicate consistent compliance with key clinical preparation standards. MaxError was centered around 0.68mm, with a range from 0.47mm to 0.9mm, demonstrating a high level of uniformity in preparation outcomes. This distribution reflects reliable preservation of enamel, clarity of margins, and anatomical contouring during the veneer preparation process, supporting the overall procedural reliability of the system. Overall, this dataset supports the conclusion that the analyzed preparation method achieves both precision and safety across a variety of clinical cases. The consistency across patients and tooth types highlights a controlled and reproducible process, providing strong indicators of quality in dental care delivery.

This study investigates concentrated model solutions, acid sulfate spent technological solutions (STSs) from surface preparation and coating operations by a number of enterprises, in order to devise unified technologies and to design relevant equipment. To substantiate the basic parameters for an electrolysis system within the framework of the system approach (Quality Function Deployment), it is shown that regardless of the concept and mechanism of electrochemical transformations, one of the main elements is redox reactions that occur both at the electrode-solution interface and in the solution volume. This paper reports experimental studies on electrochemical cathodic extraction of copper from acid sulfate concentrated technological solutions under conditions of non-stationary composition and changes in the properties of STSs. The basic technological parameters of the electrolysis process have been defined; a cathodic extraction installation of metal (copper) has been designed. To adapt the installation to changes in technological parameters and to avoid the formation of by-products together with the main product (copper), installation and dismantling of cathodes and diaphragms are implied. To eliminate secondary contamination of STS, it is proposed to abandon the use of reagents in local cycles at all stages of STS purification in favor of electrochemical technology. The kinetic data reported here (current density, current consumption/1 mol, deposition rate) make it possible to define the basic principles of control and regulation of the electrolysis process. The pH and Eh values make it possible to adjust the type of precipitate (foil, precipitate containing foreign substances), as well as determine the purpose of the technological process (regeneration, disposal). It is recommended to use diaphragm-free electrolysis in local regeneration cycles and diaphragm electrolysis in local disposal cycles

Diffusion bonding (DB) of aluminum alloys faces significant technical challenges, requiring thorough surface preparation and precise control of process parameters. To enhance the joint quality of 7B04 aluminum alloy sheets, pure aluminum (Al) and 7075 aluminum alloy powders were used as interlayers. In the DB experiments, nano-sized Al powder and micro-sized 7075 powders with different particle sizes served as interlayer materials. Compared to DB without an interlayer, using powder interlayers substantially reduced the bonding temperature while improving overall joint performance, with deformation kept below 6%. The lap shear strength (LSS) of the bonded 7B04 joints was significantly higher when 45 μm and 75 μm 7075 powders were used, compared to the 5 μm 7075 powder. The joint with a 50 nm Al powder interlayer achieved a maximum LSS of up to 220 MPa and exhibited considerably higher microhardness. Additionally, the mixed Al/7075 powder interlayer effectively decreased voids at the joint interface, contributing to increased LSS.

Abstract The performance of superconducting microwave circuits is strongly influenced by the material properties of the superconducting film and substrate. While progress has been made in understanding the importance of surface preparation and the effect of surface oxides, the complex effect of superconductor film structure on microwave losses is not yet fully understood. In this study, we investigate the microwave properties of niobium resonators with different crystalline properties and related surface topographies. We analyze a series of magnetron sputtered films in which the Nb crystal orientation and surface topography are changed by varying the substrate temperatures between room temperature and 975 K. The lowest-loss resonators that we measure have quality factors of over 10 6 at single-photon powers, among the best ever recorded using the Nb on sapphire platform. We observe the highest quality factors in films grown at an intermediate temperature regime of the growth series (550 K) where the films display both preferential ordering of the crystal domains and low surface roughness. Furthermore, we analyze the temperature-dependent behavior of our resonators to learn about how the quasiparticle density in the Nb film is affected by the niobium crystal structure and the presence of grain boundaries. Our results stress the connection between the crystal structure of superconducting films and the loss mechanisms suffered by the resonators and indicate that even a moderate change in temperature during thin film deposition can significantly affect the resulting quality factors.

Abstract Heteroepitaxial growth of Si-based semiconductor materials has become an efficient method for high-performance group-IV and III-V optoelectronic and electronic devices. As-manufactured epi-ready Si wafers frequently retain molecular residues even after high-temperature thermal deoxidation. Consequently, additional surface conditioning can be required to achieve the cleanliness and morphology necessary for high-quality epitaxial growth. This study evaluates the effectiveness of Ar plasma pre-treatment for surface preparation of Si substrates, which is used as a platform for heteroepitaxial growth of group-IV and III-V materials in molecular beam epitaxy systems. In this paper, a brief Ar plasma exposure (3 minutes at 30 SCCM) effectively removed native oxides and preserved atomically smooth surfaces, with root-mean-square roughness below 0.25 nm. Ge layers grown on plasma-treated offcut Si substrates exhibited a threading dislocation density of 6.9 × 107 cm-2, representing a ~55% reduction compared to non-treated substrates (1.3 × 108 cm-2). These findings demonstrate that Ar plasma pre-treatment provides a reliable and thermally efficient pathway for enhancing Si surface quality and supporting low-defect heteroepitaxial growth.