Increase In Surface Roughness Research Articles

Microstructural and micromechanical evolution features of asphalt with aging: An atomic force microscopy study

This study explores the aging effects on matrix asphalt (MA) and styrene-butadiene-styrene modified asphalt (SBSMA) using atomic force microscopy (AFM). Aging was simulated with the rolling thin-film oven test (RTFOT) and the pressure aging vessel (PAV) test. Key changes in microtopography, surface roughness, adhesive forces, Young's modulus, and energy dissipation were analyzed. The findings reveal significant microstructural changes with aging, including an increase in the size and a decrease in the number of beelike structures, increased surface roughness, and Young's modulus, which indicate material hardening. The analysis shows a reduction in adhesive force and energy dissipation, suggesting increased brittleness and viscosity. Notably, SBSMA exhibits better aging resistance than MA, as demonstrated by its lower roughness, stronger adhesive forces, and less reduction in energy dissipation, highlighting the effectiveness of the SBS modifier in mitigating aging impacts. These results underscore the critical role of material composition in the aging behavior of asphalt binders.

In-Vitro Comparison of Titanium Disc Surface Roughness and Bacterial Colonization after Ultrasonic Instrumentation with Three Different Tips.

During implant maintenance, preserving a smooth surface on the machined trans-mucosa abutment is critical to reduce biofilm attachment and colonization. The present study compare the surface roughness and bacterial colonization of machined titanium surfaces after instrumentation with various materials. Forty-four machined Grade 23 titanium discs were instrumented with a round Polyether Ether Ketone (PEEK) tip, a plastic curette tip, or a pure titanium curette tip with piezoelectric devices. Before and after instrumentation, the surface roughness (Ra and Rz) values were analyzed with a profilometer and scanning electron microscopy (SEM). Streptococcus sanguinis was cultured and incubated for 24 hours on the instrumented discs, and colony-forming units (CFU)/mL were obtained for each group. Samples instrumented with the metal ultrasonic tip significantly increased surface roughness compared to the other groups. Thisresulted in greater colonization by S. sanguinis than surfaces instrumented with PEEK tips or the negative control. Samples instrumented with PEEK and plastic tips did not exhibit any statistically significant increase in surface roughness. SEM analysis revealed a significantly rougher surface of discs instrumented with metal compared to discs instrumented with plastic or PEEK tip, despite the possibility of debris from tip dissolution. Our results suggested that instrumentation with metal ultrasonic tips with piezoelectric devices significantly increase machined titanium's surface roughness and elicited higher biofilm formation in vitro. Meanwhile, instrumentation of machined titanium with PEEK or plastic ultrasonic tips did not affect the surface roughness or bacterial adhesion.

From surface to success: How implant surfaces shape osseointegration

The field of dental implantology has significantly advanced to address the multifaceted impacts of tooth loss, encompassing physical, functional, emotional, psychological, and social dimensions. Dental implants serve as reliable solutions, ensuring stability, minimal bone loss, and absence of pain or infection. Central to their success is the surface modification of implants, which profoundly influences osseointegration—the process crucial for establishing a functional bond between bone and implant. This review explores various physical modifications of dental implant surfaces, focusing on macro, micro, and nano-level alterations. Macro-level modifications optimize implant geometry and thread design to enhance initial stability and long-term fixation. Micro-level modifications, including grit blasting and acid etching, increase surface roughness to facilitate mechanical interlocking and cell adhesion. Nano-level modifications, such as hydrophilic coatings and bioceramic enhancements, enhance surface energy and promote osteoblastic differentiation, thereby accelerating osseointegration. These surface modifications represent a critical frontier in implant dentistry, promising improved clinical outcomes and patient satisfaction through enhanced integration and reduced healing times.

Enterobacter cloacae-mediated polymer biodegradation: in-silico analysis predicts broad spectrum degradation potential by Alkane monooxygenase.

Plastic pollution poses a significant environmental challenge. In this study, the strain Enterobacter cloacae O5-E, a bacterium displaying polyethylene-degrading capabilities was isolated. Over a span of 30days, analytical techniques including x-ray diffractometry, scanning electron microscopy, optical profilometry, hardness testing and mass spectrometric analysis were employed to examine alterations in the polymer. Results revealed an 11.48% reduction in crystallinity, a 50% decrease in hardness, and a substantial 25-fold increase in surface roughness resulting from the pits and cracks introduced in the polymer by the isolate. Additionally, the presence of degradational by-products revealed via gas chromatography ascertains the steady progression of degradation. Further, recognizing the pivotal role of alkane monooxygenase in plastic degradation, the study expanded to detect this enzyme in the isolate molecularly. Molecular docking studies were conducted to assess the enzyme's affinity with various polymers, demonstrating notable binding capability with most polymers, especially with polyurethane (-5.47kcal/mol). These findings highlight the biodegradation potential of Enterobacter cloacae O5-E and the crucial involvement of alkane monooxygenase in the initial steps of the degradation process, offering a promising avenue to address the global plastic pollution crisis.

Enhance PD/A biofilm formation via a novel biochar/tourmaline modified-biocarriers to treat low-strength contaminated surface water: Initial adhesion and high-substrate microenvironment

In this work, a novel polyurethane carrier modified with biochar and tourmaline/zeolite powder at ratio of 1:1 and 1:2 was developed to promote the formation of biofilms and the synergy of overall bacterial activity for Partial Denitrification/Anammox to treat low-nitrogen contaminated surface water. Based on the batch experiment, the modified biocarrier, BTP2 (biochar: tourmaline = 2: 1), exhibited the highest total nitrogen removal efficiency (83.63%) under influent total nitrogen of 15 mg/L and COD/NO3− of 3. The dense biofilm was formed in inner side of biocarrier owing to the increased surface roughness and various functional groups suggested by scanning electron microscopy and Fourier-transform infrared analysis. The EPS content increased from 200.15 to 220.26 mg/g VSS in BTP2 system. Besides, the rapid NH4+ capture and organics release of the modified carrier fueled the growth of anammox and denitrification bacteria, with the activity of 2.13 ± 0.52 mg N/gVSS/h and 6.70 ± 0.52 mg N/gVSS/h (BTP2). High-throughput sequencing unraveled the increased abundances of Candidatus_Competibacter (0.82%), Thauera (0.60%) and Candidatus_Brocadia (0.55%) which was responsible for the synergy of incomplete reduction of NO3− to NO2− and NH4+ oxidation. Overall, this study provided a valid and simple-control guide for biofilm formation towards rapid enrichment and great collaboration of Anammox and denitrification bacteria.

Effect of surface pretreatment on the polypyrrole coating of acrylonitrile butadiene styrene. Part A: Synthesis and characterization

This paper investigates the synergistic effects of a two-step surface modification approach on acrylonitrile butadiene styrene (ABS) plastics. The first step involves a mechanical grinding pretreatment followed by chemical etching in sulfuric acid and hydrogen peroxide, which increases surface roughness and enhances the wettability of the ABS surface. The second step focuses on the chemical synthesis of polypyrrole (PPy) on the pretreated ABS, demonstrating improvements in PPy surface roughness and adhesion after grinding and chemical etching. Adhesion tests reveal a significant increase from 0 % (PPy on untreated ABS) to 66 % (PPy on the grounded ABS) and ultimately to 100 % (PPy on the grounded ABS after chemical etching). This research is dedicated to a comprehensive exploration of the fundamental mechanisms, substantiated by a rigorous analysis involving X-ray photoelectron spectroscopy (XPS) examination, scanning electron microscopy (SEM) and contact angle measurements. Furthermore, the electric conductivity of PPy coatings is enhanced through electrochemical doping of PPy using dodecyl sulfate anions (DS/PPy/ABS) and the incorporation of silver particles (Ag/PPy/ABS). Raman spectroscopy demonstrates the Surface-Enhanced Raman Scattering (SERS) effect of silver particles on PPy coatings, showcasing their interaction. X-ray diffraction (XRD) confirms the enhanced crystallinity of DS/PPy/ABS, aligning with increased conductivity after electrochemical doping with DS anions.

Selective double-layer on black Ni-P enhances solar absorption and reduces corrosion

This work investigates a double-layer configuration for the black Ni-P layers used in solar adsorption technology, aiming to increase the absorption of a broader range of solar wavelengths. This multilayer configuration has a surface with increased roughness and absorption area. The valleys were porous materials, which were connected to an underlying metallic sub-layer that is susceptible to corrosion. In turn, this corrosion induced changes to the top layer. The Ni-P layer was deposited by the electroless technique using an acid nickel sulfate bath as a source of metal ions and a reducing agent of sodium hypophosphite. Etching initiated an oxidation process on the surface, forming a layer of amorphous black nickel oxide for absorption. The surface features of the black Ni-P double layer consist of an uneven surface that aids sunlight adsorption. Carbon steel (AISI 1018) with different surface finishes was used for depositing Ni-P and black Ni-P, aiming to establish correlations with solar adsorption. The sample with an increased surface roughness obtained a higher absorption percentage than a single layer. The corrosion rate was calculated as 7 mmpy for the black Ni-P layer by applying polarization curves. A 6 µm-thick Ni-P double layer was obtained, achieving 96% absorption within the 300–2,000 nm range.

Minimum cutting thickness prediction model for micro-milling machining and experimental Study of FeCoNiCrMn high-entropy alloy machining

FeCoNiCrMn high entropy alloy has excellent properties such as high hardness, high strength and high wear resistance, which has a broad application prospect in aerospace, military and other fields. As an emerging difficult-to-machine material, the minimum cutting thickness determines the highest machining accuracy of micro-milling. In order to improve the micro-milling quality of FeCoNiCrMn high-entropy alloy, a minimum cutting thickness prediction model based on the effective front angle of the tool is established according to the analysis of micro-milling force model. Through the FeCoNiCrMn high-entropy alloy micro-milling processing experiments, the milling force parameters are calculated by substituting them into the prediction model, and the minimum cutting thickness value of FeCoNiCrMn high-entropy alloy is 1.367 μm when the flank radius of the milling cutter is 5 μm.When the feed rate of each tooth is in the range of 1 μm–1.5 μm, the severe size effect and the ploughing effect lead to the specific cutting energy nonlinearly increase, and the cutting force and surface roughness increase sharply with large fluctuations. From this, the range of the minimum cutting thickness of the high-entropy alloy was judged to be between 1 μm and 1.5 μm, and the accuracy of this prediction model was verified.

The effects of plastisphere on the physicochemical properties of microplastics.

The plastisphere is the microbial communities that grow on the surface of plastic debris, often used interchangeably with plastic biofilm or biofouled plastics. It can affect the properties of the plastic debris in multiple ways. This review aims to present the effects of the plastisphere on the physicochemical properties of microplastics systematically. It highlights that the plastisphere modifies the buoyancy and movement of microplastics by increasing their density, causing them to sink and settle out. Smaller and film microplastics are likely to settle sooner because of larger surface areas and higher rates of biofouling. Biofouled microplastics may show an oscillating movement in waterbodies when settling due to diurnal and seasonal changes in the growth of the plastisphere until they come close to the bottom of the waterbodies and are entrapped by sediments. The plastisphere enhances the adsorption of microplastics for metals and organic pollutants and shifts the adsorption mechanism from intraparticle diffusion to film diffusion. The plastisphere also increases surface roughness, reduces the pore size, and alters the overall charge of microplastics. Charge alteration is primarily attributed to changes in the functional groups on microplastic surfaces. The plastisphere introduces carbonyl, amine, amide, hydroxyl, and phosphoryl groups to microplastics, causing an increase in their surface hydrophilicity, which could alter their adsorption behaviors for heavy metals. The plastisphere may act as a reactive barrier that enhances the leaching of polar additives. It may anchor bacteria that can break down plastic additives, resulting in decreased crystallinity of microplastics. This review contributes to a better understanding of how the plastisphere alters the fate, transport, and environmental impacts of microplastics. It points to the possibility of engineering the plastisphere to improve microplastic biodegradation.

Influence of discrete laser surface melting on hot cracking behavior and mechanical properties of Q235 steel

Modern industries demand higher mechanical properties from components. Traditional heat treatment methods often suffer from drawbacks such as high production costs, time-intensive processes, and labor-intensive procedures. The integration of bionic engineering with laser surface melting has given rise to Discrete Laser Surface Melting (DLSM) technology, effectively mitigating these shortcomings. Previous research has substantiated the capability of this technology to significantly enhance various metal properties. This study employed an Nd:YAG pulsed laser for the DLSM treatment of Q235 steel. The discrete laser surface melted (DLSMed) units were prepared on Q235 steel samples. Subsequent analysis utilized scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive spectroscopy (EDS) to examine the microstructure and chemical composition of the DLSMed samples. Surface profilometry, hardness testing, and X-ray stress testing were conducted to measure surface roughness, microhardness, and residual stress, respectively. Mechanical properties were evaluated using tensile and impact testing machines. Experimental findings revealed that the DLSMed sample's surface could be divided into three regions: the melting zone, the heat-affected zone (HAZ), and the substrate. The microstructure of the melting zone consisted of refined martensite. The depth and width of the DLSMed units exhibited a certain regularity with variations in the defocus distance. Increasing the defocus distance positively impacted grain refinement and hardness but also led to an increase in surface roughness. Residual stress increased within a specific defocusing range, but beyond this range, its variation lost regularity. Hot cracking behavior within the DLSMed unit encompassed four stages: crack nucleation, propagation, healing, and decomposition. Different defocusing distances and the distribution of DLSMed units significantly affected the tensile strength and impact toughness of the samples. As the defocusing distance increased, the tensile and yield strength of DLSMed samples with transverse units gradually decreased. In contrast, samples with longitudinal units showed a trend of first decreasing and then increasing in tensile and yield strength. The distribution of DLSMed units played a significant role in improving the tensile properties of Q235 steel. The contribution of three factors to the impact performance of DLSMed samples was ranked from high to low as hardness, grain size, and yield strength ratio. The soft phase (substrate) could absorb impact energy and convert it into strain energy stored in the DLSMed sample. Only when the distribution of DLSMed units (hard phases) aligned with the tensile direction could they effectively limit the plastic deformation and enhance the mechanical properties of Q235 steel. However, an increase in defocusing distance led to increased brittleness, deteriorating the mechanical properties of the DLSMed samples. Finally, this study unveiled the strengthening mechanisms of DLSMed samples, providing valuable insights for future applications in enhancing the mechanical properties of metals.

The effect of a textured surface in the form of triangular prisms on the occurrence and development of cavitation behind the cylinder in microchannels

Cavitation flow in a microchannel behind a cylinder with a smooth and textured surface is investigated using mathematical modeling methods. The textured cylinder has 72 triangular prisms on its surface. The height of the prism, normal to the surface of the bluff body, was 100 nm. Profiles of the flow velocity and volume fraction of vapor are constructed. The monitoring of the velocity and pressure at five points behind both the smooth and the textured cylinder was carried out, while the inlet pressure changed up to 30 bars. It is shown that there is no restructuring of the vortex street to a symmetrical form at quite high-pressure values at the inlet to the channel for a rough cylinder. Namely, roughness prevents the flow stabilization. A pressure jump in the microchannel is observed when a cavity appears with a uniform increase in the flow rate. Two pulsation frequencies are determined for each of the flow modes. The first pulsation frequency ranges from 480 to 2200 Hz and is associated with the formation of cavitation. The second pulsation frequency is associated with the hydrodynamic flow around the cylinder and its values range from 26 to 95 kHz. An increase in surface roughness leads to a growth of the cavitation pulsation frequency and intensifies cavitation. At that, the velocity pulsations in the flow before the onset of cavitation increase, and the frequency of hydrodynamic pulsations after its onset decrease. The paper provides an analysis of the drag coefficient of a hydraulic section with rough and smooth cylindrical bluff bodies. The effect of roughness on the change in the hydrodynamic characteristics of the flow is described.

Additive manufacturing of short fiber oxide ceramic matrix composite: Process analysis and material properties

AbstractThis work investigates the material extrusion‐based additive manufacturing (AM) process chain of a pure alumina‐based oxide ceramic matrix composite, starting from material selection, large‐scale compounding to pellets, the AM process itself, debinding and sintering as well as microstructural and mechanical characterization. The compounded pellets have a volume share of 50% binder (polyvinyl butyral [PVB], polyethylene glycol [PEG], and stearic acid) and 50% alumina (Al2O3, alumina powder, and Nextel 610 alumina fibers) with an aimed fiber volume share of 40% after sintering. The material is compounded on an industrial scale with approximately 10 kg/h and the material extrusion‐based AM process reaches speeds of up to 1000 mm/s. A variation of the feed rate leads to a significant increase in surface roughness and an increase in mass of 30%, in thickness of 12% and in width of 25%. The flexural behavior in the four‐point‐bending test can be described by a fast first peak and reaching higher flexural strength after the first crack subsequent with averages of 23.8 ± 3.6 MPa below .1% elongation. The fracture surfaces show the expected failure mechanisms like pull‐out and crack deflection. The resulting fiber length in the printed samples is 140 µm in average.

Evaluation of Surface Roughness and Microhardness of Bulk-fill and Nanohybrid Composite after Exposure to Different Beverages at Various Time Intervals - An In vitro Study.

The aim of the study was to compare the surface roughness and microhardness of bulk-fill composite and nanohybrid composite resin after exposure to three different beverages at different time intervals. In this study, 60 composite discs each for bulk fill and nanohybrid, of dimensions 10 mm × 2 mm were made. Both composites were randomly divided into four subgroups, i.e., 15 samples each for artificial saliva, tea, coffee, and soft drinks which were further subdivided into five samples for three time intervals. Composite resin discs were immersed in beverages for 4 min in 24 h for 7, 15, and 30 days. All samples were evaluated for surface roughness and microhardness before and after immersion. Both the composites showed a significant increase in surface roughness in all the beverages with maximum change in surface roughness observed in nanohybrid composite resin immersed in soft drinks. Furthermore, the microhardness of both the composites was decreased significantly in all beverages with maximum change in microhardness observed in nanohybrid composite resin immersed in soft drinks. Bulk-fill composite resin has better resistance to surface roughness and higher microhardness as compared to nanohybrid. Furthermore, acidic beverages highly affect the physical properties of both composite resins for longer periods.

The effect of a textured surface in the form of triangular prisms on the occurrence and development of cavitation behind the cylinder in microchannels

Cavitation flow in a microchannel behind a cylinder with a smooth and textured surface is investigated using mathematical modeling methods. The textured cylinder has 72 triangular prisms on its surface. The height of the prism, normal to the surface of the bluff body, was 100 nm. Profiles of the flow velocity and volume fraction of vapor are constructed. The monitoring of the velocity and pressure at five points behind both the smooth and the textured cylinder was carried out, while the inlet pressure changed up to 30 bars. It is shown that there is no restructuring of the vortex street to a symmetrical form at quite high-pressure values at the inlet to the channel for a rough cylinder. Namely, roughness prevents the flow stabilization. A pressure jump in the microchannel is observed when a cavity appears with a uniform increase in the flow rate. Two pulsation frequencies are determined for each of the flow modes. The first pulsation frequency ranges from 480 to 2200 Hz and is associated with the formation of cavitation. The second pulsation frequency is associated with the hydrodynamic flow around the cylinder and its values range from 26 to 95 kHz. An increase in surface roughness leads to a growth of the cavitation pulsation frequency and intensifies cavitation. At that, the velocity pulsations in the flow before the onset of cavitation increase, and the frequency of hydrodynamic pulsations after its onset decrease. The paper provides an analysis of the drag coefficient of a hydraulic section with rough and smooth cylindrical bluff bodies. The effect of roughness on the change in the hydrodynamic characteristics of the flow is described.

Tuning properties of CTAB-HSA-AuNR nanocomposite antibacterial thin films

Protein-based biomaterials such as thin films have an edge over synthetic and bio-based polymers, due to their biodegradability in addition to other interesting properties. Proteins can be utilized to create such materials with specific functional characteristics. We report the preparation of transparent human serum albumin thin films in presence of CTAB-capped gold nanorods with different compositions of protein as well as the plasticizer i.e., sorbitol. The mechanical properties, surface topology, morphology, molecular structure, moisture content, total soluble material, biodegradability, antibacterial activity and optical properties have been investigated. Gold nanorods act as crosslinkers and sorbitol as a plasticizer increases plasticity and hardness of the films. The films deposited are biodegradable, water soluble and flexible in nature. AFM images reveal a pattern on the surface with different average heights with an increase in surface roughness with the addition of sorbitol. NINT studies show increased hardness and elastic modulus with the same amount of sorbitol but higher amounts of protein. Fourier Transform Infrared spectroscopy studies indicate the change in molecular structure of the films, in terms of a change in the hydrogen bonding network that impacts the water content and hardness of the films. Most importantly the films show antibacterial property, modulated by the composition used. The interesting features and the enhanced mechanical properties pave the path for potential applications of the films. The study shows that the optimization of the composition is crucial to achieve the desired film material with required properties.

Arc-enhanced glow discharge ion etching of WC-Co cemented carbide for improved PVD thin film adhesion and asymmetric cutting edge preparation of micro milling tools

Wear-resistant thin films on cutting tools require effective ion etching to enhance adhesion and thus extended tool service life. Arc enhanced glow discharge (AEGD) ion etching, characterized by high ionization degrees and high etch rates, was applied to ultrafine-grained WC-Co cemented carbide, commonly used for micromilling cutters. The effect of AEGD ion etching on the surface integrity of WC-Co and the resulting adhesion behavior of a TiAlSiN thin film was investigated by varying the etching time in comparison with conventional glow discharge (GD) ion etching. In addition, the impact of intensive etching on the cutting edge geometry of micro end cutters and, in turn, on the cutting performance in micromilling of hardened and annealed high-speed steel was evaluated.AEGD achieves remarkable etch rates of 12 nm/min at extended etching times, which are 100 times greater than conventional glow discharge (GD) ion etching. Prolonged AEGD ion etching for ≥30 min removes entire near-surface WC grains and exposes carbides beneath, resulting in increased surface roughness. After the etching process, polished WC-Co substrates exhibit a slight reduction in residual compressive stresses, which steadily decrease with increasing AEGD ion etching time. Furthermore, a TiAlSiN thin film demonstrates high adhesion on AEGD-etched surfaces compared to GD ion etching. Even a brief 5 min AEGD ion etching ensures the highest adhesion class according to the Rockwell C indentation test. Moreover, the intensive material removal results in significant changes in cutting edge geometry of micro end cutters, yielding substantial cutting edge rounding and an asymmetrical shape with form-factors Κ ≥ 2. In cutting tests, the resulting cutting edge geometries effectively reduce the wear formation and the associated wear-related increase in process forces during micromilling hardened and tempered powder metallurgical high-speed steel. In summary, AEGD ion etching emerges as a highly effective method for both enhancing thin film adhesion and preparing adapted asymmetrical cutting edge geometries for micromilling tools.

The Effects of Air Abrasive Polishing on the Release of Iron Ions from Various Orthodontic Arch Wires (Stainless Steel and Nickel Titanium)

Orthodontic treatment with has been increasingly demanded. However, when using fixed appliances for orthodontic treatment, oral hygiene is compromised, and there is a higher chance of developing dental stains, plaque-related diseases, and corrosion-related problems. Air abrasive polishing had a superior effect over the conventional method in removing dental deposits, however, its effect on corrosion process was not investigated thoroughly in details. This study designed to assess the effects of air polishing onion release and surface micromorphology of stainless steel and Nickel titanium arch wires. A total of 288 ( stainless-steel , coated stainless steel , Nickel titanium and coated Nickel titanium rectangular arch wires ) of one brand ( The Ultimate Wire) ™ From IOS (International Orthodontic Services, Stafford, USA), (0.016 * 0.022 ) were subjected to varying air abrasion polishing periods (5, 10, and 20 seconds), after which they were immersed in artificial saliva with a pH of 6.75 and incubated at 37°C for 28 days. Ion release was measured using an atomic absorption spectrophotometer at 7 days, 14 days, and 28 days. The cumulative effect was then calculated. After polishing the chosen sample, corrosion and surface changes were evaluated using a scanning electron microscope (SEM). The significant difference between the analysed groups was found using an analysis of variance (ANOVA) and the LSD test, with a significance level of p 0.05. The results revealed that all types of arch wire showed a significant amount of release in the tested ions and the amounts of nickel and iron ions released was higher than chromium ion. Additionally, the longer the polishing time the higher the number of ions release that’s yields the level of significance, air abrasion polishing increased surface roughness and surface pits and crevices.It may be concluded that the air polishing method enhanced the amount of ion release to a subtoxic level and could be employed in adult patients with a lengthy time between visits.This study was performed to:1. Evaluate the effect of calcium carbonate airborne particles abrasion with different polishing times 5, 10 and 20 seconds on (Fe) ions release from orthodontic arch wires. 2. Assess the surface micromorphology of orthodontic arch wires after air polishing procedure.

Effect of Corrosion and Post-Weld Treatment on the Fatigue Behavior of Multipass Robot GMAW Welds of S700MC Steel

High-strength steel is a candidate material for offshore structures, which are currently being constructed with regular-strength steel. These structures are constantly exposed to harsh environmental conditions and experience cyclic loadings, which can lead to premature failure due to the synergistic effects of corrosion and fatigue. In this regard, the current study aims to investigate the effects of corrosion and High-Frequency Mechanical Impact (HFMI) treatment on the fatigue behavior of welded joints made of S700MC steel. Multipass butt-welded joints were fabricated via the Robot GMAW method at an optimally selected heat input of 0.7405 kJ/mm. The microstructure of the weldments was studied using light optical microscopy. Tensile and Vickers microhardness tests were performed to evaluate the mechanical properties of the welded joints. To simulate marine environment corrosion in the laboratory, the as-welded samples were exposed to salt fog spray for 720 h. Subsequently, specimens were subjected to cyclic loading to evaluate their fatigue strength, while SEM and stereomicroscopy were used to analyze the fractured surfaces, providing a comprehensive understanding of the fracture mode. The findings suggest that although corrosion led to increased surface roughness and the formation of corrosion pits, its influence on the fatigue behavior of the weldments might be less significant compared to other geometrical factors, at least for the exposure time employed in the study.

Effects of material type and surface roughness of settlement tiles on macroalgal colonisation and early coral recruitment success

AbstractSexual propagation of corals is a promising strategy for coral restoration, but one of the main challenges is the high mortality of coral spat due to competitive interactions with macroalgae during the early life history stages. Optimising the properties of settlement substrates such as material types and surface roughness has the potential to improve the survival of spat by limiting the recruitment and growth of macroalgae. In this study, we assessed the effects of modifying surface roughness across three different tile materials (alumina-based ceramic, calcium carbonate (CaCO3), and concrete) on the settlement success and post-settlement survivorship of Acropora kenti coral larvae in six mesocosm tanks, each with different established macroalgal communities. The macroalgal community compositions on the tiles were significantly different among material types, but not surface roughness, although the type and abundance of macroalgal species were heavily influenced by the established tank communities. Increasing surface roughness did not affect larval settlement success or spat survivorship. Substantially higher larval settlement density was found on concrete tiles (1.92 ± 0.10 larvae cm−2), but spat survival was the highest on CaCO3 tiles (73.4 ± 4.2% survived). Very strong competitive interactions were observed between spat and macroalgae, with overgrowth by the crustose coralline alga Crustaphytum sp. and the brown alga Lobophora sp. being the primary cause of spat mortality. Overall, when taking into account both settlement and survival rates, concrete was the best performing among the tile types tested here.

Effect of whitening dentifrices on dental enamel: an analysis of color, microhardness, and surface roughness in vitro.

This study aimed to evaluate the influence of different whitening toothpastes on color change and alteration in enamel surface roughness and microhardness compared to a conventional toothpaste. Fifty bovine incisors were selected, cleaned, and stored before being divided into five groups: a conventional toothpaste group (C) and three whitening toothpaste groups containing different abrasive agents: silica (S), hydrogen peroxide (PH), and activated charcoal (CA). Specimens underwent simulated brushing, staining with black tea solution, and subsequent analyses of color, surface roughness, and microhardness. Statistical analysis was performed using three-way ANOVA and Tukey post-hoc tests (P < .05). The results showed that the color analysis revealed similar whitening potential among all toothpastes. Otherwise, showed significant differences in surface roughness (P < .001) and microhardness (P < .001) after simulated brushing. While all toothpastes caused a decrease in microhardness, the charcoal-based toothpaste showed a significant increase in surface roughness compared to the initial condition. All toothpastes demonstrated whitening capability. Surface roughness changed after brushing with activated charcoal-based whitening toothpaste, but final roughness was similar across all groups. Whitening toothpastes led to a decrease in enamel microhardness, with similar final performance across all toothpastes analyzed.