Increase In Surface Roughness Research Articles

Optimization of machining parameters while turning AISI316 stainless steel using response surface methodology

The chromium-nickel alloy known as AISI 316 Stainless Steel is extensively used in various industries, such as the chemical industry, nuclear power plants, and medical devices, due to its exceptional mechanical properties and corrosion resistance. Compared to other stainless steels, AISI 316 resists corrosion from air and other corrosive conditions better. Determining the optimal selection of machining parameters is still a challenge for many researchers. The Box Behnken technique (L12 array) is used in this work to design the experiment set. Response surface methodology (RSM) is used to examine how the cutting velocity (100, 150, and 200 m/min), feed (0.10, 0.15, and 0.20 mm/rev), and depth of cut (02, 0.4, and 0.6 mm) affect the cutting force (Fc), surface roughness (SR), power consumption (Pw), and tool life (T). The ANOVA investigation shows that cutting force and surface roughness increase linearly with an increase in feed. Similarly, power consumption and tool life also increase linearly with an increase in cutting velocity. The best combination for the lowest Fc, SR, and Pw and the maximum T is cutting velocity at 122.37 mm/min, feed at 0.13176 mm/rev, and cut depth at 0.213337 mm. For cutting force, surface roughness, power consumption, and tool life, the actual and predicted values are (124.31, 129.45), (0.55, 0.57), (1.131, 1.154), and (2112, 2225), respectively. For the lowest feasible values of Fc, SR, Pw, and maximum T, the optimal settings are a cutting speed of 122.37 mm/min, feed of 0.13176 mm/rev, and depth of cut of 0.213337 mm.

Preparation and Corrosion Resistance of Superhydrophobic Composite Coatings on Shot-Peened AA 7075-T6 Aluminum Alloy

In order to further improve the corrosion resistance of 7075-T6 aluminum alloy after shot peening, corrosion-resistant superhydrophobic coatings (EP-HDTMS@SiO2) containing epoxy resin (EP), cetyltrimethoxysilane (HDTMS), and nano-silica (SiO2) were prepared by a simple spraying method on the surface of shot-peened AA 7075-T6 aluminum alloy. The effects of different EP/SiO2 mass ratios on the micro-morphology, surface wettability, and corrosion resistance of the superhydrophobic composite coatings were analyzed. Due to the combination of microstructure and the modification of low surface energy organics, the contact angle of EP-HDTMS@SiO2 coatings reached the superhydrophobic level (152.6°). The electrochemical tests showed that the corrosion current densities (Icorr) of the EP-HDTMS@SiO2 composite coatings were both significantly lower than those of the EP-HDTMS coatings and matrix aluminum alloys. The addition of SiO2 nanoparticles could improve the hydrophobicity and corrosion resistance of epoxy-based composite coatings. Due to the increase in surface roughness and epoxy resin, the shot-peened AA 7075-T6 alloy coating had high adhesion after the peel test. The prepared coatings also showed excellent corrosion resistance in the neutral salt spray test. This study provides a simple method for preparing stable superhydrophobic coatings on metal surfaces, which is expected to expand the application of 7075 aluminum alloy in harsh environments.

Machining Performance of Ti6Al4V Nano Composites Processed at Al2O3 Nano Particles Mixed Minimum Quantity Lubrication Condition

Introduction: In this research work, an attempt was made to machine Ti6Al4V nano composites utilizing Al2O3 mixed nano fluid at minimum quantity lubrication condition, in which experiments were designed using the L16 orthogonal array, whereas Material Removal Rate, Surface Roughness, machining force and power were recorded as responses. Methods: The nano composites were fabricated using the stir casting technique and the nano particles were synthesized using the sol-gel technique. the microstructure revealed that the homogeneous dispersion of particles with dendric arms. Increased cutting speed and feed lead to more tool wear, which in turn causes a decrease in surface quality and an increase in surface roughness. Results: Larger areas of cut are often the consequence of higher feed rates, which increases the amount of friction between the work piece and the cutting edge. The machining force increases when the feed rate is increased. A higher feed rate produces a large volume of the cut material in a given length of time in addition to having a dynamic impact on the cutting forces. Conclusion: It also results in a corresponding increase in the typical contact stress at the tool chip interface and in the tool chip contact zone.

Surface modification of 3D-printed polycaprolactone- human decellularized bone matrix composite scaffold by plasma for bone tissue engineering

BackgroundBone tissue engineering is a revolutionary field focused on creating viable bone substitutes using advanced materials and techniques. Utilizing 3D printing, precise and customizable bone scaffolds can be produced. A notable composite material in this domain is a composite of polycaprolactone (PCL) and human decellularized bone matrix (hDBM), which combines synthetic and natural elements for enhanced functionality. To further improve cell attachment and growth, cold plasma surface modification is employed, optimizing scaffold surfaces. These innovations collectively hold great potential for improving bone repair and regeneration outcomes. MethodsScaffold architecture was designed through CAD software, and the composite of PCL and hDBM was printed using FDM technology. Surface modification was achieved by exposing the scaffolds to Argon-Oxygen (Ar-O₂) plasma radiation for 1 and 3 minutes. Both treated and untreated scaffolds were characterized, including measurements of surface roughness, hydrophilicity, and cellular activity. ResultsAlmost all groups showed non-toxic effect on cellular behavior during cell culture. Plasma-treated scaffolds showed a significant increase in surface roughness, with roughness values (Ra) increasing from 10.45 nm (untreated) to 62.75 nm after 3 minutes of plasma exposure. Contact angle measurements decreased from approximately 66.5° in untreated scaffolds to 31.4° in those treated for 3 minutes, indicating enhanced hydrophilicity. Plasma-treated scaffolds demonstrated excellent cytocompatibility, significantly enhancing cell proliferation, osteogenic differentiation, and mineralization compared to untreated scaffolds. After 7 days, scaffolds treated for 1 and 3 minutes showed 35% and 60% increases in cell proliferation, respectively, highlighting the role of plasma treatment in creating a bioactive surface conducive to cell adhesion, growth, and improved osteogenic properties, with longer exposure times further amplifying these effects. ConclusionsThe current study demonstrates the efficacy of Ar+O₂ plasma treatment in enhancing the surface properties of PCL-hDBM scaffolds, making them more conducive to osteogenesis. This study suggests that plasma-treated PCL-hDBM scaffolds are a promising option for bone tissue engineering applications.

Synthesis and characterization of new quaternized galactomannan derivatives with antibacterial activity.

The continuous increase in bacterial resistance requires the study and development of new biocompatible antibacterial materials. Galactomannan gum was extracted from endosperms of Dimorphandra gardneriana seeds, modified through quaternization reactions (with NaOH/CHPTAC), and evaluated for antimicrobial activity. Four quaternized derivatives were obtained (QG1-QG4). The derivatives were characterized by FTIR, NMR, and rheology, which confirmed the cationization. The galactomannan structure was theoretically studied, and Zeta potential exhibited positive increase in the charge of quaternized derivatives, changing from -3.2mV (unmodified galactomannan) to +59.35mV (QG4). Elemental analysis revealed an increase in degree of substitution (DS) between the derivatives, of which QG4 exhibited the highest DS (0.51). QG4 exhibited a bactericidal effect in the antimicrobial test for determination of minimal inhibitory and bactericidal concentrations, against Gram-positive bacteria. Atomic force microscopy showed an increase in bacterial cell surface roughness and decrease in cell height after treatment with QG4. QG3 and QG4 demonstrated antibiofilm potential, showing 50% and 40% of inhibition, respectively. After MTT assay, cell viability was maintained approximately 100% for all derivatives at concentrations of 20mg/mL on RAW 264.7 macrophages and 86% with 250μg/mL on L929 cells. Galactomannan was successfully modified, demonstrating strong antibacterial activity, concomitant to the increase in DS, Zeta potential and reduction of molar mass, with good biocompatibility. Therefore, this study presents a new material with potential for development of formulations for biomedical applications, from industrial waste, strengthening of the D. gardneriana production chain.

Lithium tantalate film prepared by RF magnetron sputtering and effect of thickness on performance of inorganic electrochromic devices

Lithium tantalate (LiTaO3) thin films of varying thicknesses were deposited using RF magnetron sputtering for applications in electrochromic devices. The microstructural, optical and electrical properties of the films were systematically investigated. Microstructural analysis revealed that with increasing LiTaO3 films thickness, more island particles appeared and distributed densely and uniformly. Micro-cracks formed owing to the increased internal stress and the surface roughness increased significantly. LiTaO3 films exhibited high transmittance in the visible spectral range but showed significant absorption at wavelengths below 300 nm. The increasing LiTaO3 films thickness resulted in higher resistance and lower leakage current. Inorganic all solid electrochromic devices were fabricated using LiTaO3 film as the ion conductor layer. The charge capacity (ΔQ) decreased with increasing LiTaO3 film thickness, primarily due to Li+ transfer at the interface. Adjusting the deposition sequence of the of WO3 and NiO layer effectively mitigated the loose fiber-like structures and cavities in WO3. The presence of island-like particles and increased surface roughness introduced higher interfacial impedance and charge transfer resistance, further hindering Li+ transport. These factors resulted in irreversible Li+ insertion/extraction processes, ultimately degrading the electrochromic performance.

Modeling the relative permeability of gas and water flow in rock fractures with surface morphology parameters

Rock fracture morphology influences two-phase fluid flow in rock fractures. However, the role of the surface morphology of rock fractures in two-phase flow remains to be fully quantified. In this study, an analytical model for gas and water relative permeability in rough rock fractures was developed, incorporating surface roughness factor, hydraulic tortuosity, and surface tortuosity to quantify fracture morphology. The performance of the proposed model was evaluated through a comparison with empirical permeability models and experimental data. The proposed model accurately characterized two-phase fluid flow in rough fractures and examined the impact of surface morphology and flow dynamics on the relative permeability of two-phase fluids in rock fractures, demonstrating that increased surface roughness shifts the equal-permeability point toward higher water saturation and lower relative permeability. To investigate the influence of the flow dynamics on relative permeability, the proposed model was extended to express the Reynolds number of two-phase fluids as a function of water saturation and relative permeability, enabling a detailed exploration of the evolution law of relative permeability with Reynolds number.

Bio-colonisation, durability, and microstructural analysis of concrete incorporating magnetite and oyster shell waste aggregates in marine environment

This study evaluates the impact of bio-colonisation and seawater attack on the durability, microstructure and mineralogy of two distinct concrete formulations. These formulations are designed to meet the specifications of marine infrastructure applications, particularly those intended as biomimetic solutions for infrastructures typically used for boat anchoring, which are commonly responsible for the displacement and destruction of marine habitats. The first formulation incorporates magnetite aggregates, resulting in a heavy concrete capable of stabilising the base structure of the biomimetic concrete mooring. In the second formulation, natural gravel is partially substituted by oyster shell waste, to reduce the carbon footprint of these marine infrastructures. Experimental tests were conducted to evaluate the bio-colonisation and durability of the two concrete formulations under marine exposure. After 24 months of immersion, the surface biomass on both formulations exhibited similar kinetic bio-receptivity, primarily attributed to the binder and surface roughness rather than the type of aggregates used. The porosity accessible to water decreases in marine conditions, suggesting that the biofilm contributes to this decrease. Durability results indicate that while both concrete types deteriorate under seawater exposure, the oyster shell aggregates demonstrated better resilience to natural seawater aggressiveness compared to magnetite aggregates over long-term exposure. Elemental mapping showed no obvious zonation of elements. However, a slight increase in surface roughness was observed, with no macroscopic damage detected. This research enhances our understanding of how magnetite and oyster shell waste aggregates respond to bio-colonisation and seawater attack, which are critical factors in the development of biomimetic marine infrastructure.

Surface characteristics evolution of 316L stainless steel induced by tension loading

316L stainless steel has been employed as a medical implant material owing to its advantageous biocompatibility and durability. The microstructure and surface characteristics of 316L play a crucial role in implant application. Diverse processing methods were utilized to modify the surface properties of 316L to customize the characteristics of medical devices. Mechanical deformation induces changes in the microstructure and causes changes in surface topography. In this study, we introduced deformation to 316L by applying uniaxial tension at strain values ranging from 2% to 25%. During sample preparation, electrochemical polishing was employed to eliminate the deformed layers generated by mechanical grinding. After the tensile test, a contact angle test was conducted. The surface relief of 316L was examined using three-dimensional (3D) laser scanning microscopy and atomic force microscopy. X-ray diffraction with CuK radiation in the Bragg–Brentano (θ–θ) mode was also employed to identify the phase transformation. It can be concluded that higher strain levels increased surface roughness and the number of slip lines. At higher strain levels, samples exhibited a martensitic transformation, affecting topography changes and the surface free energy. The contact angle measurement results and surface free energy determination showed improved wettability following plastic deformation. Determining the factors that affect surface wettability requires an understanding of the relationship between surface free energy, topography, and surface roughness. Deformation-induced martensite can significantly increase the surface free energy and wettability of 316L stainless steel (SS) by altering strain levels. It is important to consider surface characteristics to understand slip mechanisms at grain boundaries, particularly in cases where surfaces have been electropolished. Nevertheless, the surface also manifested deformation-induced martensitic (DIM) transformation, potentially posing a risk to the passive film and contributing to corrosion, consequently reducing the implant’s lifespan.

MOF incorporated Polyethersulfone/Polylactic Acid ultrafiltration membranes for the catalytic removal of dyes via persulfate activation

This study synthesized novel nanocellulose/zeolitic Imidazolate Framework nanocomposite blended Polyethersulfone/Polylactic Acid (PES/PLA-CNF@ZIF-8) membranes through a modified phase inversion process. This is the first time that a nanocellulose-MOF composite catalytic nanomaterial has been synthesized and used as an additive in polymeric membranes. The morphology and chemical structure of the membranes and nanoparticles were characterised by scanning electron microscopy (SEM), atomic force microscopy (AFM) and Fourier transform infrared (FTIR) respectively. Membrane wettability and crystalline structure were characterised by contact angle, and X-ray diffraction (XRD) analysis respectively. CNF@ZIF-8 modified membranes showed improved contact angle which decreased from 76° in the pristine membranes to 40° in 2 wt% membranes, bulk porosity increased from 74.3.3 % to 81.06 % while the pure water flux increased from 208.30 Lm-2h−1 to 348.73 Lm-2h−1. Further, the modified membranes showed an increase in surface roughness reaching 84.14 nm in 2 wt% membranes. The synthesized membranes have been used as catalysts in the activation of persulfate to degrade Rhodamine B dye. The modified membranes displayed a high catalytic effect (>90 %) in activating persulfate to degrade RhB dye when compared to pristine membranes which showed a degradation efficiency of < 35 %. The study found that the optimum parameters for pH, membrane (catalyst) dosage, oxidant and initial dye concentration were 5, 0.3 g, 0.4 mM and 10 ppm respectively. Quenching experiments showed that •SO4- and •OH radicals were responsible for the dye degradation, with •SO4- radicals playing a major role in the oxidative degradation of the RhB dye. The synthesized membranes showed good stability when tested within five cycles, with the membranes showing degradation efficiency ranging from 92.1 % in the 1st cycle to 91.9 % in the 3rd cycle, before decreasing to 75.3 % in the 5th cycle. This study has therefore shown that the synthesized PES/PLA-CNF@ZIF-8 membranes have potential for use as catalysts in the degradation of cationic dyes in wastewater treatment through persulfate activation.

Impact of Drill Bit Wear on Screw Withdrawal Resistance in Pinewood

Many factors affect screw withdrawal resistance (SWR), including screw size, embedment depth, the pre-drilled hole’s diameter, dimensional accuracy, and the furniture pieces’ material properties being joined. While prior research has extensively examined the influence of these factors, this study aimed to explore a neglected factor: how drill bit wear impacts pilot hole quality and subsequent SWR. The experimental setup included pinewood samples with pre-drilled 5 mm diameter blind pilot holes with a depth of 45 mm. The holes were equally divided into two groups: one drilled with a sharp bit, the other with a blunt bit. Euro-type coarse furniture screws (7 mm major diameter, 4 mm minor diameter, 3 mm pitch) were screwed into all holes. Subsequently, SWR was measured using a universal testing machine. Results show a statistically significant decrease in SWR when using the blunt drill bit. This phenomenon can be explained by excessive local material degradation, increased surface roughness, and disrupted hole dimensional accuracy, collectively hindering SWR. The study’s findings offer insights into how excessive drill bit wear impacts the screw withdrawal capacity of pinewood, informing best practices in furniture and construction.

Influence of thermal-cycling or staining medium on the surface properties and color stability of conventional, milled, and 3D-printed base materials

The study of denture base resin fabricated by digital technology with surface properties or color stability remains limited. In this study, thermal cycling and staining media (distilled water, artificial saliva, green tea, and Coca-Cola) immersion were used to simulate the intraoral environment to assess the surface properties and color stability of CAD/CAM (milled) and 3D-printed base resin materials, the conventionally polymerized base served as the control group. After thermal cycling, all groups showed increased surface roughness, contact angle (i.e. hydrophilicity) and color difference (∆E), the 3D-printed group had the most significant increase among the 3 groups (P<0.001). While there were no significant difference (or the difference is very small) between the conventional and milled groups. After 7 and 30 days of immersion in four staining media, the ∆E values remained highest in the 3D-printed group (∆E ≥ 3.34) (P<0.001), exceeding the clinically acceptable threshold (∆E = 2.7) at 30 days. Additionally, all groups showed significantly higher ∆E values after 30 days compared to 7 days (P<0.05). The 3D-printed group exhibited a rougher surface, poorer hydrophilicity, and reduced color stability compared to the conventional or milled groups, indicating that further improvements are needed before clinical application.

Электрофизические характеристики сегнетоэлектрических пленок оксида гафния и титаната бария стронция

Electrophysical properties of hafnium oxide (HfO2) and barium strontium titanate of the composition (BST) thin films of various thicknesses from 20 nm to 250 nm are studied. Capacitance-voltage characteristics of Ni/HfO2/Si and Ni/BST/Si structures have been measured. The hysteresis loops width values are obtained depending on the films thickness. It is shown, that as the films thickness increases, the surface roughness and grain size increase. Calculated the exponential growth index values were β = 1.4 for HfO2, and β = 0.5 for BST films. Based on the local hysteresis loops results obtained in the polarization switching spectroscopy mode, coercive field values for studied films of various thicknesses were calculated, and «scaling» effect was found. It has been found that BST films are more ferroelectric «soft» material compared to HfO2 films at the same thicknesses.

Improved Oxygen Reduction Reaction Activity of Graphene via Mechanochemical Activation and Halogen‐Doping

AbstractThere has been an increased effort to replace the expensive and rare platinum and platinum group metals to speed up the sluggish oxygen reduction reaction (ORR) kinetics, which limits the efficiency of fuel cells. One class of promising Pt‐alternative catalysts for ORR is metal‐free halogen‐doped carbon materials. Herein, bromine‐doped and iodine‐doped graphene were synthesized via mechanochemical activation. The synthesized samples exhibited sub‐rounded particles. Mechanical activation via ball milling increased the specific surface area of graphene by reducing particle size. Ball milling also enhanced dopant dispersibility and increased surface roughness, though it reduced surface area compared to ball‐milled graphene, likely due to the size difference between carbon and halogen atoms. Among the synthesized catalysts, iodine‐doped graphene exhibits the highest limiting current density of 1.806 mA cm−2 with the highest ORR onset potential of 0.74 V vs reversible hydrogen electrode (RHE). The iodine‐doped graphene also showed good stability after 1000 cycles of accelerated degradation test. The enhanced ORR performance of iodine‐doped graphene was reached using the optimized iodine‐to‐graphene mass ratio of 4 : 1 after 48 h ball milling time.

Methane seepage leads to a specific microplastic aging process in the simulated cold seep environment

Marine microplastics pose a significant threat to ecosystems, and deep-sea regions serve as critical sinks for these pollutants. Among these regions, cold seeps harbor relatively high concentrations of microplastics. However, research on the aging of microplastics under low-temperature, dark, methane-abundant, and high-pressure conditions remains limited. Seawater and sediment were collected from various Haima cold seepage sites to simulate seepage environments in 200-mL high-pressure reactors. Four types of microplastics at high concentrations (approximately 10 %) were cultured and monitored over two months to explore how they aged. The key findings are as follows: (1) Compared to areas of weak seepage, methane seepage accelerated microplastic aging, as evidenced by increased surface roughness, enhanced C-O and (CO)-O bond formation, increased microbial colonization, and reduced contact angles. (2) Microplastic aging is more pronounced in sediments than in seawater, with biodegradable polylactic acid (PLA) exhibiting the most significant aging characteristics and carbon contribution. (3) Aged microplastics induce greater disturbances in inorganic nutrient levels than in organic matter, impacting nitrogen cycle processes involving nitrate, nitrite, and ammonium. This study results reveal the fundamental aging characteristics of microplastics in extremely deep seas and highlight their potential ecological effects.

Construction and performance study of interface layer of carbon fiber/epoxy composites by electrostatic adsorption

AbstractElectrostatic adsorption was used to self‐assemble layers of polymers and nanoparticles with varying charges onto the carbon fiber (CF) surface. This process created two distinct ionic crosslinked network layers: (3‐aminopropyl) triethoxysilane‐phytic acid‐polyethyleneimine (APTES‐PA‐PEI) and (3‐aminopropyl) triethoxysilane‐phytic acid‐nano‐silica (APTES‐PA‐SiO2). Fourier transform infrared spectrophotometer (FTIR) and X‐ray photoelectron spectroscopy (XPS) were used to confirm the presence of ionic interactions. The modified carbon fibers (CFs) exhibited increased surface roughness, higher concentration of functional groups, and improved wettability. Compared to untreated CF composites, the interfacial shear strength (IFSS) and the transverse tensile strength test (TFBT) of CF‐APTES‐PA‐PEI/epoxy composites increased by 67.8% and 62%, respectively. In contrast, the IFSS and TFBT of CF‐APTES‐PA‐SiO2/epoxy composites increased by 63.3% and 52.8%, respectively. The observed strengthening is attributed to the combined effects of ionic crosslinked networks, covalent and hydrogen bonding interactions, enhanced wettability, and the relatively roughened fiber surface. The interfacial layer design approach proposed in this study is both straightforward and effective, demonstrating significant potential for functionalizing CFs. This method is expected to be adaptable for other high‐performance fibers.Highlights The ionic cross‐linked network interface layers were designed. IFSS and TFBT were significantly improved. The enhancement mechanism was elaborated.

Bond and tensile properties of flax textile reinforced recycled aggregate concrete: Strategies for interfacial enhancement and corresponding mechanisms

This study investigated the bond properties between flax fibre reinforced polymer (FFRP) mesh and various cementitious matrices, examining the impact of incorporating medium-sized recycled aggregates (2 – 8 mm). Enhancement strategies included modifying the FFRP surface with rice husk ash (RHA) and incorporating RHA into the cementitious matrix. Pull-out and uniaxial tensile tests were performed on FFRP reinforced mortar, FFRP reinforced recycled aggregate concrete (RAC), RAC reinforced with RHA-modified FFRP and RAC (containing RHA) reinforced with RHA-modified FFRP. The results showed that FFRP surface modification with RHA significantly improved bond strength, by 32 % compared to pulling normal FFRP from RAC. This was attributed to increased surface roughness of FFRP, enhanced chemical bonding due to pozzolanic reaction of RHA, and improved interfacial transition zone resulting from increased wettability and decreased water absorption ratio of the treated FFRP. Additionally, the inclusion of medium-sized recycled aggregates mitigated debonding by enhancing mechanical interlocking with the FFRP mesh. Compared to FFRP reinforced mortar, FFRP reinforced RAC and RHA-modified FFRP reinforced RAC exhibited increased strain capacity and refined crack propagation, indicating improved stress distribution. However, the enhanced anchoring reduced tensile strength by restricting the full utilisation of strain capacity in the post-cracking phase. These findings highlight the potential of surface modification of reinforcement with supplementary cementitious materials and the incorporation of medium recycled aggregates in the matrix to enhance bond performance and optimise the mechanical behaviour of cementitious composites.

The interplay between toothbrush stiffness and charcoal-containing dentifrice on the development of enamel topography changes

BackgroundThis study aimed to investigate the in vitro effect of a charcoal-containing dentifrice with different toothbrush stiffness on enamel.MethodsFour main groups were applied: distilled water, conventional fluoridated toothpaste (Colgate® Total® 12 Clean Mint Toothpaste), charcoal toothpaste (Colgate® Total® Charcoal Toothpaste) and whitening toothpaste (Colgate Total® Advanced Whitening Toothpaste). Three subgroups for each toothpaste were further included according to the toothbrush bristles’ stiffness (soft, medium, and hard). Enamel specimens were subjected to 1,250 and 2,500 cycles of brushing using toothbrushing simulation machine. The average surface roughness change (ΔRa) in nanometer (nm) was measured to estimate the changes following the brushing simulation model. Two-way ANOVA and Tukey tests analyzed the data.ResultsThe type of toothpaste and the bristles’ stiffness were determinant factors in increasing the ΔRa value (P = < 0.05). Generally, charcoal and whitening toothpastes with medium and hard bristles yielded higher ΔRa than fluoridated toothpaste and smooth bristles. Following 1,250 cycles of brushing simulation, charcoal toothpaste did not increase the enamel roughness compared to the controls. However, in prolonged brushing via 2,500 cycles of brushing simulation, using bristles with soft stiffness revealed that charcoal toothpaste was associated with increased surface roughness (55.86 ± 41.18 nm), which was statistically significant (P = 0.024) compared to the negative control. Using bristles with medium stiffness showed that the whitening (68.23 ± 48.58 nm) and charcoal (73.62 ± 34.66 nm) toothpastes significantly (P = < 0.05) increased the enamel roughness compared to the conventional toothpaste (36.53 ± 22.56 nm). There was no significant difference among the groups when brushes with hard bristles were used, as all the groups revealed increased enamel roughness.ConclusionThe use of charcoal and whitening toothpastes increased enamel roughness, particularly with long-term use. The effect of bristle stiffness on enamel roughness was found to vary depending on the type of toothpaste used.

Achieving enhanced electroless Ni-P plating on 6H-SiC substrate through optimization of plasma activation durations

This study explores the impact of plasma activation on the surface properties of 6H-SiC substrates and the subsequent characteristics of electroless nickel‑phosphorus (NiP) plating. The research investigates how varying plasma activation durations influence surface roughness, chemical composition, and plating adhesion. Plasma activation significantly increased surface roughness from 592 nm to 772 nm and the oxidation layer thickness from 5.76 nm to 32.2 nm. These changes were accompanied by corresponding decreases in water and NiP solution contact angles, indicating enhanced surface wettability. The electroless NiP plating demonstrated a progressive increase in surface roughness, and the Ra roughness reached 1319 nm. X-ray diffraction (XRD) analysis revealed a reduction in the crystallinity of the NiP layer, alongside the emergence of new phases such as Ni2P and Ni8P3, indicating alterations in the structural and chemical composition of the plating. The average thickness of the NiP plating decreased from 39.70 μm at 10 min of plasma activation to 36.12 μm at 30 min, suggesting a potential reduction in deposition efficiency with prolonged activation times. Additionally, the hardness of the NiP layer exhibited a decline from 525 HV to 502 HV, attributed to increased surface oxidation and defect formation. The adhesion quality of the plating also deteriorated with increased plasma activation time, as evidenced by significant peeling and cracking, as observed in the scratch test.

Effect of Autoclave on Surface Topography of Various Rotary Files

ABSTRACT Background: Rotary files are essential tools in endodontic procedures, designed to efficiently shape and clean the root canals. However, repeated sterilization, particularly via autoclaving, may affect their surface integrity, potentially compromising their performance and longevity. This study aims to evaluate the changes in surface topography of various rotary files after multiple autoclave cycles using Scanning Electron Microscopy (SEM). Materials and Methods: In this study, three types of rotary files—NiTi, stainless steel, and gold-treated files—were selected for analysis. Each type comprised 20 samples, totaling 60 files. The files underwent 10 cycles of autoclave sterilization at 121°C for 15 minutes. SEM analysis was conducted before and after sterilization to assess changes in surface characteristics. Parameters such as surface roughness, presence of micro-cracks, and debris retention were meticulously evaluated. Results: Post-autoclave SEM analysis revealed significant alterations in surface topography across all file types. NiTi files showed an increase in surface roughness by 35%, with evident micro-cracks in 40% of samples. Stainless steel files exhibited a 25% increase in surface roughness, while 30% showed minor deformities. Gold-treated files displayed the least surface alteration, with a 15% increase in roughness and micro-cracks observed in only 10% of samples. Debris retention was notably higher in NiTi files post-sterilization. Conclusion: Autoclave sterilization significantly impacts the surface topography of rotary files, with NiTi files showing the most pronounced changes. Gold-treated files exhibited greater resistance to topographical alterations, suggesting superior durability under repeated autoclave conditions. These findings underscore the importance of selecting appropriate file types based on sterilization frequency to ensure optimal endodontic performance and tool longevity.