Papers by Keyword: Surface Roughness

Abstract: This study examines the significant potential of used tea powders (UTP) as a sustainable additive for recycling aluminium alloy 5083. By remelting and recasting aluminium chips with varying quantities of UTP (0 g, 2 g, 4 g, and 6 g), this research aims to provide insights into the microstructural, mechanical, and surface characteristics of the resulting materials. Notably, the recycled aluminium exhibited smoother surfaces in comparison to the bulk alloy, particularly with moderate UTP additions of 2 g to 4 g, which effectively reduced surface roughness. The highest hardness recorded was 57.66 HV for the recycled aluminium without any additives; however, the initial addition of UTP led to a decrease in hardness, which interestingly stabilised at higher concentrations. Microstructural analysis indicated refined grain structures and the formation of carbon- and oxygen-rich phases when optimal levels of UTP were employed. Conversely, higher quantities resulted in some degree of agglomeration and porosity. In conclusion, UTP demonstrates considerable promise as an environmentally friendly modifier that enhances microstructure and supports sustainable practices in aluminium recycling.

Abstract: Gated Hall measurements of lateral MOSFET devices can be used to directly measure the inversion layer free carrier density and carrier Hall mobility. From this measurement the total number of charged interface traps (N_IT) can be extracted. This provides useful insight into the degree of Coulomb scattering expected. By obtaining gated Hall data from 4° off-axis Si-face (0001) 4H-SiC MOSFETs with varied p-well doping levels, mobility limiting components can also be estimated. For these samples it is observed that interface trapped charge is almost half of the total inversion charge, and thus Coulomb scattering dominates at low Vgs or low transverse (or normal) effective field; while phonon scattering may dominate at moderate effective field, and surface roughness only limits mobility at gate fields higher than the rated usage, or at doping levels much higher than 2×10¹⁸ cm^-3.

Abstract: The long-term performance of dental implants relies on material stability and sustained osseointegration. This study analyzed titanium implant after six years of clinical function and compared it with unused implants to assess surface integrity. Field emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDX) were used to evaluate morphology and elemental composition, while surface roughness was measured to detect changes. SEM showed direct bone attachment, and EDX confirmed calcium, phosphorus, sodium, oxygen, and carbon associated with osseointegration. Roughness values increased slightly due to adherent bone tissue, but no evidence of surface wear or degradation was observed. These results demonstrate that titanium maintains chemical stability, biocompatibility, and reliability for long-term dental implant applications.

Abstract: 4H-SiC is a wide-bandgap semiconductor that has become essential for power electronics due to its large bandgap, high critical electric field, and excellent thermal stability. Within the {0001} basal orientation, the two polar surfaces – Si-face and C-face – exhibit distinct behaviours during chemical vapor deposition (CVD) homoepitaxy, with direct implications for device performance and manufacturing. In this work, n-type epitaxial layers were deposited on 150 mm, 4° off-axis Si-face and C-face substrates under identical conditions in a single-wafer hot-wall LP-CVD reactor (T > 1600 °C, P = 3.0 kPa, C/Si = 1.05, silane/propane/ethylene precursors, N₂ doping, HCl additive). Characterization analysis revealed pronounced polarity-dependent differences. AFM analysis showed that C-face epilayers exhibited smoother surfaces and reduced step bunching compared with Si-face layers. Optical and photoluminescence inspections show polarity-dependent defect propagation, with the C-face displaying reduced replication of extended defects under the explored conditions. However, nitrogen incorporation on the C-face orientation was more than 25× higher than Si-face orientation and displayed poor uniformity, highlighting the limited effectiveness of site-competition epitaxy on this orientation. In contrast, the Si-face provides tighter control of doping concentration and lateral uniformity, albeit with higher step bunching and rougher surfaces. These findings emphasize a fundamental trade-off in 4H-SiC homoepitaxy: the C-face offers morphological and structural advantages, while the Si-face ensures superior doping control and process stability. A deeper understanding of these polarity-dependent mechanisms is essential to optimize epitaxial growth strategies and to enable the design of high-performance SiC power devices.

Abstract: Although Laser engraving (LE) is increasingly adopted for precision surface texturing, the resulting surface is highly sensitive to the coupled thermal and hydrodynamic mechanisms governing laser–material interaction. In this experimental work, LE of Incoloy 800HT is systematically investigated using an L9 Taguchi design of experiments considering Laser Power (LP), Laser Scanning Speed (LSS), and Laser Pulse Frequency (LPF) as control parameters. Surface roughness is quantified using the arithmetical mean height (Ra), maximum profile height (Rz), skewness (Rsk), and the height at material ratio Rmc = 20%, enabling both amplitude-and function-oriented assessment of the engraved textures. The contribution of each parameter is evaluated through ANOVA and response ranking, and regression-based correlations are established to support predictive selection of processing conditions. The results show that LP is the dominant factor for Ra, Rz, and Rmc (20%), while LSS primarily governs Rsk, reflecting the role of scanning speed in controlling melt redistribution and peak–valley balance. High cumulative energy conditions promote thermal accumulation, melt ejection, spatter redeposition, and recast formation, leading to substantially rougher surfaces, as corroborated by topography and SEM observations.

Abstract: Laser surface texturing (LST) is an effective technique for tailoring the surface properties of Ti6Al4V alloy, widely employed in biomedical applications where surface topography plays a key role in osseointegration and functional performance. Nevertheless, the strong nonlinear relationship between laser process parameters and resulting surface roughness still limits predictive control of laser-textured surfaces. This work presents an experimental study aimed at investigating the influence of laser surface texturing parameters on the surface morphology of Ti6Al4V. Key process variables, including laser power, scanning speed, pulse frequency, pulse duration and overlap percentage are systematically varied using a fiber laser system. The textured surfaces are characterized through three-dimensional surface roughness parameters, namely Sa, Sz, Sku, Svk, and Ssk, providing a detailed quantitative description of surface topography relevant for biomedical applications. The resulting experimental dataset represents a fundamental basis for the subsequent development of artificial intelligence models, based on neural networks, for predicting surface roughness parameters as a function of laser processing conditions. The proposed approach supports data-driven optimization of laser surface texturing processes within intelligent and sustainable manufacturing frameworks.

Abstract: This study provides a comprehensive investigation into the effects of different scanning parameter combinations—specifically scanning speed and hatch distance—on the material properties of IN939 fabricated using the powder bed fusion-laser beam (PBF-LB) process under a constant volumetric energy density (VED). Despite the fixed VED, the fabricated samples experienced different thermal cycles, resulting in distinct microstructural features and corresponding variations in material performance. In-situ infrared monitoring indicated that the sample with the narrowest hatch distance and highest scanning speed (Sample 1) reached the highest normalized temperatures with intense heat accumulation, whereas wider hatch distances (Sample 3) promoted lower and more stable temperature distributions. The results revealed that the intermediate parameter set (Sample 2) achieved the highest relative density (99.29%) and the lowest surface roughness. In contrast, both the narrowest and widest hatch spacing combinations promoted increased porosity, primarily consisting of lack-of-fusion (LoF) and gas pores. Electron backscatter diffraction (EBSD) analysis showed that the area-weighted average grain size increased from 29.5 µm to 36.7 µm as the hatch distance increased. Texture analysis indicated generally weak crystallographic texture development, with only slight intensification of <001>//BD and <111>//BD components, attributed to the 67^o rotation strategy. Furthermore, the microhardness values demonstrated negligible variation across the samples, ranging from 356.7 ± 14.3 HV1 to 360.1 ± 10.5 HV1. This limited variation indicates that the strengthening behavior was predominantly governed by the combined influence of defect density and matrix–defect interactions, rather than being directly correlated with grain size.

Abstract: AZ31 magnesium alloy is a representative magnesium alloy with well-balanced mechanical properties and castability. However, AZ31 magnesium alloy also has the disadvantage of poor corrosion resistance due to its low aluminium content. In previous research, it is known that the corrosion mechanism is such that filamentous corrosion is generated and then changes to full-scale corrosion. However, the relationship between corrosion and bending properties has not been revealed. In this study, AZ31 magnesium alloy was immersed in salt water with a concentration of 5%, and three-point bending tests were conducted to confirm changes in bending stress and strain due to strength loss caused by corrosion. Then, investigated which parameters Ra and Rz, which are indicators of surface roughness, are related to the maximum bending stress of the fully corroded AZ31 magnesium alloy. As a result, when evaluating the relationship between maximum bending stress and corrosion, it was found that it is better to evaluate by Ra of the corroded surface rather than by Rz.

Abstract: This work investigates the effect of anodized aluminum oxide films on the surface characteristics and corrosion behavior of AlSi10Mg alloy fabricated via laser powder bed fusion (PBF-LB). A ∼10 μm thick oxide layer was formed using sulfuric acid anodizing, under both as-built and stress-relieved (300 °C, 2 h) conditions. Surface morphology, microstructure, and corrosion performance were characterized using scanning electron microscopy, EDS, and immersion testing in 3.5% NaCl solution. Anodizing significantly reduced surface roughness (Ra) from ~14 µm to ~6 µm, with further reduction in extreme topographical features observed in heat-treated samples. Cross-sectional analysis confirmed uniform oxide growth, while immersion tests revealed delayed corrosion onset relative to uncoated material. However, localized pitting was still observed, particularly in heat-treated samples, likely due to Si-network fragmentation. These findings demonstrate that anodizing enhances surface finish and corrosion resistance of AM AlSi10Mg, while microstructural features, such as silicon morphology, remain critical to oxide layer integrity.

Abstract: AbstractAlthough manufacturers recommend glazing and polishing for CAD/CAM milled restorations, the relative efficacy of either in achieving optimal surface roughness and wear remains ambiguous. This study has been carried out to investigate how polishing and glazing affect the surface characteristics and hardness of milled monolithic zirconia. Thirty cuboid-shaped milled zirconia samples (10 mm length× 10 mm width× 3mm thickness) were cut from a pre-sintered zirconia block (Aconia^®, Besmile Biotechnology Co., Ltd. Chengdu, China). Samples were sintered, cleaned, and divided into two groups according to surface treatment (n = 15). Group P: Polished only, Group PG: Polished and glazed. Each treatment was performed according to the manufacturer’s guidelines. One sample was examined from each group using a Scanning Electron microscope (SEM) to explore the surface morphology. Surface roughness was assessed using a profilometer. Vickers hardness (VHN) was evaluated using a Vickers diamond indenter. All data were calculated, and statistical analysis was performed. There was a significant difference between groups in surface roughness and hardness. The average surface roughness (Ra) value of polished zirconia samples (2.1611 µm) was higher than the Ra value of glazed zirconia samples (1.3273 µm), while the Vickers hardness (VHN) of polished zirconia samples (1.4721) was lower than the VHN of glazed zirconia samples (3.7843). SEM analysis images validated the findings on the surface roughness. The glazing after polishing of monolithic zirconia showed better surface smoothness and higher hardness.