Search Results (158)

This study evaluates the rapid tooling feasibility and structural significance of utilizing digital light processing (DLP)-printed alumina as a near-net-shape ceramic mold-insert preform route for replication of curved polymer optics. While conventional production tooling for precision optics demands immediate optical-grade tolerances, the fundamental mechanisms governing polymer replication close to additively manufactured ceramic interfaces remain insufficiently understood. To isolate these multi-factor processing signatures, alumina specimens incorporating concave and convex parabolic surfaces were synthesized via lithography-based ceramic manufacturing. Our design acts as a geometric control lens, ensuring that thermal shrinkage trends, slicing kinematics, and interfacial replication behaviors are clearly exposed and quantified under uniform boundary conditions. Following debinding and sintering, exploratory hot-pressing cycles were executed to evaluate gross profile transfer and surface inheritance on poly(methyl methacrylate) (PMMA) replicas. Quantitative laser scanning confocal microscopy confirmed successful gross curvature generation and revealed geometry-dependent post-sintering shrinkage trends. The convex inserts exhibited an average peak-to-valley (PV) error of 123.48 ± 3.30 µm and an RMS error of 29.76 ± 1.23 µm, whereas the concave alumina inserts showed an average PV error of 137.98 ± 5.80 µm and an RMS error of 34.68 ± 1.20 µm. The PMMA replicas also showed substantial form deviation, with an average PV error of 163.72 ± 15.64 µm and RMS error of 27.37 ± 2.03 µm. Our work presents a route for producing near-net-shape ceramic mold-insert preforms that transforms complex processing variations into a predictable, mathematically addressable roadmap. A geometry-specific CAD pre-compensation can then be performed while the remaining precision gap can be selectively closed via targeted post-polishing depending on the desired optical application tier. Full article

Background/Objectives: Police is an occupational group characterised by high and variable physical demands, shift work, and the need for sustained operational readiness. Despite the importance of maintaining good health in uniformed services, relatively little is known about dietary habits and nutritional status among police populations, particularly in Poland. Therefore, the aim of this study was to characterise dietary habits and nutritional status among Polish police officers participating in the National Health Programme. Methods: This cross-sectional study included 262 Polish police officers (216 men and 46 women) aged 19–64 years. A 61-item food frequency questionnaire (FFQ) was used to assess dietary behaviours and bioelectrical impedance analysis was used to assess body composition. Results: Suboptimal food consumption frequency patterns were observed for several food groups, including fruits, vegetables, whole grains, dairy products, nuts, and seeds. Female police officers reported more frequent consumption of fruits, vegetables, and grains, and less frequent consumption of processed meats, animal fats, sugar-sweetened beverages, energy drinks, beer, and spirits than male officers. Normal body weight according to BMI criteria was observed in 33% of participants, whereas only 16% of participants had normal fat mass index values. Excessive body weight was observed in 67% of participants, and excess fat in 82% of participants. Conclusions: The study provides a comprehensive characterisation of dietary habits and nutritional status among Polish police officers within the National Health Programme. These findings suggest the need for nutritional education, health promotion activities, and continued monitoring of dietary habits and nutritional status in this occupational group. Full article

Abrasive flow machining (AFM) is an effective finishing process for complex internal surfaces, particularly cavities, intersecting holes, and micro-channels that are difficult to access using conventional tools. However, when low-viscosity abrasive media is used (here defined, relative to conventional putty-like viscoelastic AFM carriers (with apparent viscosities of 10³–10⁵ mPa·s), as a water-based slurry with an apparent viscosity below 300 mPa·s over the operating shear-rate range), unfavorable flow conditions during the initial polishing stage can induce local over-polishing, erosion depressions, stepped patterns, and cavitation pits, resulting in non-uniform surface quality. The relationship between these flow behaviors and polishing defects remains insufficiently understood. To address this issue, this study investigates the AFM process applied to turbine blade film cooling holes through combined experimental and numerical approaches. The observed defects include erosion depressions, stepped surface patterns, and cavitation pits. The effects of abrasive injection pressure, flow velocity, hole geometry, abrasive viscosity, and particle size on defect formation are systematically examined. The results show that the initial abrasive filling level strongly affects defect distribution by altering the evolution of shear fields and void regions within the hole. Experimentally, at high Reynolds numbers (Re > 2 × 10⁴), intensified local shear and cavitation promote defect formation, while a moderate inclination angle (45–60°) and a higher aspect ratio (>8) are favorable for polishing uniformity. Complementary numerical simulations further indicate that smaller abrasive particles (<5 μm) and a moderate abrasive viscosity (~60 mPa·s) are predicted to improve polishing uniformity. This study clarifies the fluid-dynamic origin of polishing defects in film cooling holes and provides process guidance for suppressing local over-polishing, cavitation, and uneven material removal. Full article

ZERODUR glass-ceramic is widely used in ultra-precision optical components because of its extremely low thermal expansion and excellent dimensional stability. However, its two-phase microstructure, composed of crystalline and amorphous phases with different mechanical properties, may cause non-uniform material removal during magnetorheological polishing, thereby limiting further improvement of nanoscale surface quality. To address this issue, this study investigates the effect of oxide abrasives on the surface homogenization of ZERODUR. A single-particle abrasive–workpiece contact model based on modified Hertz contact theory and elastoplastic contact analysis was established to compare the indentation responses of CeO₂, SiO₂, and ZrO₂ abrasives in the two constituent phases. Magnetorheological polishing experiments were conducted under identical process parameters, and the polished surfaces were characterized by AFM over scan areas of 2 μm × 2 μm, 5 μm × 5 μm, and 10 μm × 10 μm. The results show that all three abrasives improved the surface quality of the ring-polished substrate, with ZrO₂ achieving the best surface homogenization performance. The lowest roughness, Ra = 0.104 nm, was obtained at a 2 μm field of view, and the ZrO₂-polished surface showed more stable roughness evolution across different scan sizes than the CeO₂- and SiO₂-polished surfaces. These results indicate that the elastic modulus, hardness, and mechanical compatibility of abrasives with ZERODUR play key roles in governing contact stress, indentation behavior, and final surface quality. This work addresses the lack of mechanistic understanding of abrasive-dependent surface homogenization in the magnetorheological polishing of two-phase ZERODUR glass-ceramic. The main innovation is the integration of contact-mechanics-based abrasive–workpiece modeling with multi-scale AFM characterization to clarify how abrasive mechanical compatibility affects nanoscale surface uniformity and to guide abrasive selection for ultra-smooth optical manufacturing. Full article

Aiming at non-uniformity in the vertical direction in the polishing effect on stainless steel after plasma electrolytic polishing (PEP), this paper took 304 L stainless steel as the research object. Under an ammonium sulfate electrolyte system with a mass fraction of 2.5 wt%, PEP was carried out utilizing different placement methods for the anode and electrolyte temperatures, and the causes of non-uniformity in the polishing process were explored. Experimental results demonstrate that the vertical polishing inhomogeneity originates from the upward movement of unruptured bubbles at the sample bottom. Under the combined effects of electrolyte internal pressure and bubble buoyancy, a vapor-gas envelope (VGE) featuring a thick upper part and thin lower part forms near the sample surface. This enhances plasma-related physicochemical reactions at the sample bottom and consequently raises the polishing rate. The vertical polishing unevenness can be alleviated by adjusting the electrolyte temperature. Non-uniformity could be improved by controlling the temperature of the electrolyte. Compared with the result at 95 °C, the maximum dimensional variation in each region on the sample at 75 °C was reduced by 36% because a VGE with more uniform thickness was formed, and a properly oxidized sparse layer helped protect the substrate from ablation and over-polishing. In addition, the removal rate of elements on the surface of stainless steel is affected by its activity due to the oxidation reaction. The high removal amount in the bottom region caused a trend of increasing Cr and decreasing Fe content percentages from the top to the bottom on the stainless-steel surface. However, the oxidation removal rate of elements is extremely fast due to the high temperature of the ionization center and strong electric field; therefore, the content percentage of each element on the surface is little changed after polishing. Full article

This study investigates the effects of post-processing on the surface roughness, wettability, and frictional behavior of selective laser-melted (SLM) cobalt–chromium–tungsten (CoCrW) alloys for orthodontic use. The SLM-CoCrW specimens were tested in as-manufactured, mechanically polished, and electropolished states. Surface characterization via stylus profilometry and atomic force microscopy (AFM) showed that both polishing methods reduced macro- and micro-scale roughness, with electropolishing producing the smoothest, most uniform topography. Static water contact angle (WCA) measurements revealed that mechanical polishing provided an optimal balance of roughness and hydrophilicity, resulting in the lowest friction, while ultrasmooth electropolished surfaces exhibited slightly higher friction due to increased hydrophobicity and a uniform Cr-rich oxide layer confirmed by X-ray photoelectron spectroscopy (XPS). XPS also indicated that electropolishing generated a homogenous chromium oxide passive film, whereas mechanical polishing left a chemically heterogeneous surface with exposed metallic sites. Importantly, performance is not governed solely by surface roughness; surface chemistry is equally critical, and both must be considered together—along with wettability and tribological behavior—to achieve optimal functional outcomes. From a clinical perspective, optimization of surface roughness and surface chemistry may result in decreased frictional resistance, improved sliding mechanics, and enhanced long-term performance of additively manufactured orthodontic components; however, the present study was restricted to in vitro characterization under simplified laboratory conditions, and further investigations involving artificial saliva, long-term aging, wear and clinical simulations are necessary to validate the translational relevance of these findings. Full article

This study systematically investigated the effects of air-cooled pre-hardening and oil-quenched quenching-and-tempering processes on the microstructure, mechanical properties, and polishing performance of P20 plastic mold steel. Increasing the austenitizing temperature from 820 °C to 940 °C resulted in a more uniform carbide distribution, a slight improvement in hardness, and enhanced polishing performance for both processes. However, grain coarsening at 940 °C reduced the impact toughness from 157.6 J to 111.7 J. After tempering at 650 °C, both processes yielded a tempered sorbite microstructure. However, in the air-cooled samples, the carbides were aligned along the bainite lath direction, whereas in the oil-quenched samples, they exhibited an equiaxed, non-directional distribution owing to the complete recovery of the matrix. Austenitizing at 940 °C followed by air cooling and tempering at 550 °C provides the optimal balance of hardness, toughness, and polishing performance. Mitigating elemental segregation and narrowing the segregation bands represent key strategies for further enhancing polishing performance. Full article

The surface quality of wafers processed by double-sided polishing (DSP) is significantly influenced by pad morphology. However, quantitative analysis remains challenging due to the complexity of dynamic contact conditions and the coupled effects of pressure and trajectory. To address material removal non-uniformity on wafer surfaces during DSP, this study focuses on the pressure–trajectory coupling mechanism and develops a material removal model incorporating pad topography effects. First, a kinematic model is established to derive the relative velocity of any point on the wafer. Secondly, a 3D elastic contact simulation model is constructed based on a linear elastic small-deformation model to obtain spatial pressure distribution under different pad morphologies. The full-cycle transient process is obtained by averaging typical steady-state conditions. A material removal calculation method is proposed by integrating time-dependent relative velocity and dynamic pressure within a modified Preston framework, and the model is validated against experimental results reported in the literature. Simulations and reported experiments demonstrate that pads with varying radial topographies generate differentiated pressure distribution. The results show that wafer radial within-wafer non-uniformity (WIWNU) can be effectively reduced to 1.002 by adjusting pad shape. This study extends the applicability of material removal rate models and provides a predictive framework for precision control in DSP wafer planarization. Full article

Surface defects in additively manufactured internal channels limit their practical applications. Conventional post-processing methods suffer from limited accessibility and a tendency toward over-polishing, whereas magnetic abrasive finishing (MAF) offers high adaptability and precise process controllability. This study systematically investigates the material removal mechanisms in magnetic abrasive polishing and clarifies the distinctions and transitions between two-body and three-body wear modes. Based on these findings, a rolling removal model grounded in rough surface contact theory and a sliding removal model incorporating correction factors are established. Experiments were conducted on AlSi10Mg internal channels fabricated via selective laser melting (SLM) using a composite magnetic field polishing apparatus. The results verify the accuracy of the proposed models and demonstrate that the process effectively reduces surface defects and surface roughness. Although some deviations arise from model idealization and non-uniform magnetic field distribution, this study establishes a systematic theoretical framework for material removal in additively manufactured complex internal channels. Full article

Transmission Electron Microscopy (TEM) requires electron-transparent samples with thickness below 100 nm, and conventional preparation methods involving mechanical polishing followed by electropolishing or ion milling are time-consuming and prone to preparation-induced defects. In this study, an electrothinning process was proposed as an alternative intermediate TEM sample preparation technique. Electrothinning was carried out on 1 mm thick equiatomic NiTi alloy using H₂SO₄ (20%) and methanol (80%) electrolyte at an operating voltage of 10–15 V for 20 min. The sample thickness was reduced from 1 mm to 55 μm through controlled anodic dissolution without mechanical deformation. Uniform thinning behaviour was observed under optimized conditions, while lower voltages resulted in insufficient dissolution and higher voltages caused localized pitting. TEM analysis confirmed the absence of noticeable mechanically induced defects or deformation features in the electrothinned samples. The proposed method is a cost-effective and efficient alternative for TEM sample preparation in research and industry. Full article

A combined pretreatment strategy involving alkaline chemical polishing and silane electrodeposition was proposed for regulating the surface state of aluminum foil and the formation of etched tunnels during DC tunnel etching. Electrochemical measurements and morphological characterization were used to evaluate the effects of this pretreatment on surface electrochemical activity and etched tunnel structure. The results showed that appropriate alkaline chemical polishing facilitated the removal of rolling-induced surface relief, improved the uniformity of surface electrochemical activity, and favored the uniform deposition of the silane film. In contrast, excessive polishing generated surface pits during the polishing process, and these preformed pits subsequently promoted tunnel merging during DC tunnel etching. Under the optimal processing conditions, the combined pretreatment significantly improved the distribution uniformity and dimensional consistency of etched tunnels and suppressed tunnel merging. Under the present testing conditions, the specific capacitance increased from 0.386 to 0.509 μF cm⁻², corresponding to an improvement of approximately 31.9%. This work provides an effective approach for optimizing etched tunnel structure and improving the capacitance-related performance of aluminum capacitor foil. Full article

Additive manufacturing (AM) enables the fabrication of complex three-dimensional components with embedded internal flow channels, but the as-built inner surfaces often exhibit high roughness and poor surface-quality uniformity, particularly at non-coplanar corner regions such as sharp bends and junctions. Conventional abrasive flow machining (AFM) can improve the overall surface finish of such channels; however, corner regions commonly remain weak-removal zones because of local flow stagnation and insufficient abrasive action. To address this limitation, this study proposes a six-degree-of-freedom (6-DOF) robotic-arm-assisted liquid metal-driven abrasive flow (LM-AF) polishing strategy in which robotic pose regulation is used to guide the liquid metal droplet to designated corner regions while preserving its responsiveness to the electric field. Numerical simulations and conventional AFM experiments on S-shaped and M-shaped spatial channels were first conducted to identify the corner regions as the primary sources of polishing non-uniformity. A robotic posture-control framework was then established through manipulator kinematics, point-cloud-based flow-direction identification, and Rodrigues-matrix-based pose transformation. On this basis, localized secondary polishing was experimentally performed on an S-shaped channel using an AC electric-field-driven liquid-metal abrasive system. The results show that corner-region roughness was significantly reduced and approached the straight-channel benchmark after secondary polishing, demonstrating a marked improvement in inner-surface uniformity. This study provides a practical route for targeted compensation polishing in complex three-dimensional internal channels and offers a new framework for robotic-assisted post-processing of AM-fabricated flow paths. Full article

Objectives: Achieving a smooth tooth surface following periodontal instrumentation is critical for maintaining periodontal health and minimizing plaque and calculus reaccumulation. This narrative review aimed to synthesize preclinical laboratory-based evidence regarding the effects of periodontal instrumentation techniques on enamel and cementum surface roughness and hard-tissue loss. Methods: A focused literature search was conducted using the PubMed database to identify relevant in vitro and in vitro/in vivo hybrid studies published within the last 15 years. This review focused on ultrasonic scaling, hand instrumentation, and air polishing of human teeth during periodontal treatment. Results: Periodontal instrumentation was associated with surface alterations of enamel and cementum, with the extent of these changes depending on instrumentation parameters. Manual instrumentation was generally associated with greater surface irregularities and increased cementum removal, whereas ultrasonic scaling tended to produce more uniform surface characteristics. However, outcomes varied depending on instrumentation parameters. Air-polishing systems were described as less abrasive, particularly in biofilm management. Conclusions: Within the limitations of predominantly in vitro evidence, periodontal instrumentation appears to alter dental hard tissues to varying degrees depending on the technique and application. The clinical relevance of these findings remains uncertain, as the evidence was primarily laboratory-based and may not fully reflect clinical conditions or predict long-term outcomes. Full article

Ti-6Al-4V parts fabricated via selective laser melting (SLM) often exhibit severe surface irregularities that limit their direct engineering application. This study proposes a top-hat beam laser polishing method to improve surface quality. The results show that surface roughness (Sa) is reduced to 0.48 μm, a 95.3% decrease from the as-built condition. The uniform energy distribution of the top-hat beam stabilizes melt pool behavior, enabling effective surface leveling through valley filling and lateral melt flow. In contrast, Gaussian beam polishing induces strong Marangoni convection and wake effects, resulting in higher residual roughness. Microstructural analysis indicates an increased fraction of equiaxed α grains and a β-phase content of ~6% after top-hat polishing. The heat-affected zone likely exhibits a subcritical heat-treatment-like effect, promoting fine secondary α precipitation. Additionally, localized stresses induced by steep thermal gradients during SLM are effectively relieved. Overall, top-hat laser polishing is a promising post-processing technique for enhancing the surface quality of Ti-6Al-4V components. Full article

Biofouling is an issue of global significance that impairs marine infrastructure, causes increased fuel consumption and greenhouse gas emissions, and threatens biodiversity. Since the year 2000, self-polishing copolymer (SPC) coatings and fouling release coatings (FRCs) dominate the fouling protection coatings market. SPC technology is based on the controlled release of biocides using a mixture of acrylic and natural binders as a delivery system. FRC technology is based on PDMS providing surface properties that resist attachment of fouling organisms. FRCs often contain surface modifying agents, such as free silicone oils, to tune the physicochemical properties of the surface. However, the long-term efficacy of these agents and their migration and distribution in PDMS-based coatings have not been well studied. In this study, we employed time-of-flight secondary ion mass spectrometry (ToF-SIMS) combined with multivariate analysis to examine the distribution of silicone oils as a function of exposure to artificial seawater (ASW). The results show that pure PDMS-based coatings allow uniform distribution of silicone oils with robust behavior upon ASW exposure. In contrast, epoxy–PDMS-based coatings displayed phase separation of the oils, which strongly altered their surface chemistry. Our findings suggest that the modification of mobile oils is critical to the performance of marine antifouling coatings. Furthermore, the presence of other ingredients of commercial coating formulations strongly affected the distribution of mobile oils. This study lays the foundation for future systematic research aimed at developing predictive models to optimize fouling protection coatings for the marine industry. Full article