Search Results (3,934)

Methods of single-point diamond turning and chemical mechanical polishing can achieve an ultra-flat substrate. However, these methods which rely on mechanical interactions to achieve material removal can easily lead to defects such as abrasive embedding and scratches on the surface. In addition, for low-rigidity and thin-plate workpieces, clamping deformation and force deformation are critical factors affecting the machining accuracy. This paper proposes a two-step polishing chain that uses controllable electrochemical and chemical etching to correct the shape error of the workpiece. With the optimized parameters, the jet electrochemical machining (Jet-ECM), which uses the electrochemical etching mechanism, is applied to the computer-controlled optical surfacing (CCOS) to achieve the rapid convergence of the shape accuracy. In addition, electrogenerated chemical polishing (EGCP) is implemented as a follow-up process which uses the mechanism of diffusion-controlled chemical etching to reduce the mid-spatial-frequency (MSF) error caused by the computer-controlled optical surfacing. Based on this two-step polishing chain and the self-developed devices, the peak-to-valley (PV) value of the φ 50 mm workpiece (valid dimensions = 90% of the central region) is reduced from 2.678 μm to 0.384 μm. This study has great implications for further understanding the mechanism of Jet-ECM and EGCP, which expands the applications of stress-free polishing to solve the processing problems of the low-rigidity workpiece. Full article

During the high-temperature deposition of tungsten thin films on alumina ceramic substrates, the inherent mismatch in thermal expansion coefficients frequently triggers interfacial delamination, where uncontrollable factors in stochastic surface topographies can exacerbate localized stress concentrations. To resolve these interfacial failures, the enhancement of interfacial adhesion through a deterministic surface microgroove design is identified as the general objective of the present research. Within this framework, the establishment of a robust quantitative mapping between the transverse scratching offset distances and the resultant periodic microgeometry is first pursued as a specific experimental objective. This methodological approach effectively transforms the stochastic nature of the substrate into deterministic geometric configurations. Second, a specific numerical objective is fulfilled by evaluating the interfacial stress redistribution and damage evolution utilizing refined thermomechanical coupled simulations based on the cohesive zone model. The integrated findings demonstrate that optimizing the microgroove spacing effectively governs the morphological transition and broadens stress diffusion pathways to mitigate thermal mismatch effects. Specifically, the structural optimization at a spacing of 28.8 μm facilitates an approximately 31.8% reduction in the maximum interfacial stress and a 10% decrease in the average film stress compared to the 13.6 μm spacing. Finally, this research clarifies the underlying mechanisms of stress buffering and provides a rigorous engineering methodology for the structural design of reliable high-performance ceramic–metal interfaces in extreme environments. Full article

Boronizing treatment has gained significant attention for its effectiveness in enhancing the wear resistance of IN718 alloy. However, conventional boronizing temperatures for IN718 are higher than its aging temperature, which can disrupt the aged microstructure and lead to degradation of mechanical properties. In this study, pack boriding was performed on solution-treated IN718 alloy in the aged condition (760 °C for 10 h followed by 650 °C for 8 h). The microstructure, mechanical properties, and tribological behavior of the boride layer formed on IN718 were systematically investigated. The boride layer, with a thickness of approximately 15 μm, was found to be primarily composed of CrB, Cr₂B, Ni₂B, and Fe₃Ni₂₀B₆ phases. Following boronizing treatment, the surface hardness of IN718 was enhanced from 278 HV_0.2 to 1938 HV_0.2, with a concurrent significant increase in the yield strength of the bulk specimen. When sliding against a 440C steel counterface, the specific wear rate of the boronized sample was reduced by a factor of 49, and the friction coefficient decreased to 70% of that of the substrate. The dominant wear mechanism shifted from adhesive, abrasive, and oxidative wear for the untreated IN718 to abrasive and oxidative wear for the boronized specimen. Full article

The dense passivation film (DPF) formed on the surface of martensitic stainless steel effectively improves corrosion resistance, but it also hinders the adsorption and diffusion of active nitrogen atoms during gas nitriding. In this work, the influence of the DPF of 1Cr11Ni2W2MoV stainless steel on gas nitriding was overcome by controlling the cooling rate during stainless steel solution treatment, thereby enabling the successful formation of a nitrided layer. The effects of nitrogen potential on the microstructure, phase constitution, and tribological performance of the nitrided layer were systematically investigated. A dense passivation film formed at a solid-solution cooling rate of 110 ± 5 °C/s effectively inhibited nitrogen diffusion, resulting in the absence of a nitrided layer. However, when the cooling rate during solid solution was reduced to 80 ± 5 °C/s, the precipitation of chromium carbide along the grain boundaries damaged the density and integrity of the DPF, thereby enabling the formation of a nitrided layer during gas nitriding. A high nitrogen potential enhanced nitrogen diffusion and increased the nitrided layer thickness. However, an excessively high nitrogen potential led to nitrogen enrichment along grain boundaries, resulting in microcracking and reduced mechanical integrity of the compound layer. When the nitrogen potential was 1.0, a uniform and crack-free nitrided layer with a surface hardness exceeding 1000 HV_0.1 was obtained. Tribological tests combined with SEM observations of the worn surfaces showed that gas nitriding significantly reduced the friction coefficient and wear rate compared with the matrix sample. Among the nitrided samples, H-10 exhibited the lowest friction coefficient and wear rate, whereas H-23 showed relatively inferior wear resistance due to microcrack-related brittleness. The dominant wear mechanism changed from severe abrasive–adhesive wear in the matrix sample to mild abrasive wear in the nitrided samples. These results indicate that regulating passivation film integrity through heat treatment, together with optimizing nitrogen potential, is an effective strategy for achieving high-quality gas nitriding and improved tribological performance in martensitic stainless steel. Full article

Fine migration is widely recognized as a primary cause of production decline in unconsolidated sandstone reservoirs. Migrated fines may accumulate within pore throats and obstruct flow channels, or they may be transported into the wellbore with the produced fluids, leading to operational issues such as wellbore plugging, pump sticking, and equipment abrasion. Despite extensive studies on fine migration, the role of particle wettability has received limited attention. In this study, the mineralogical composition of formation particles was first characterized using X-ray diffraction (XRD) and quantitative clay analysis. Surface modification experiments were then conducted to investigate the effect of hexadecylamine (HDA) on particle wettability and to determine the optimal reaction conditions. Surface characterization techniques were employed to elucidate the modification mechanism. Subsequently, sand-packed tube displacement experiments were performed to evaluate the influence of wettability alteration on fine migration behavior. The underlying mechanisms were further interpreted through interfacial thermodynamic analysis. Two potential field application schemes are proposed to facilitate practical implementation in oilfield operations. The results indicate that the water contact angle of formation particles increased from 0° to 150° when treated with 0.8 wt% HDA for 24 h. Surface characterization confirms that HDA molecules were physically adsorbed onto the particle surfaces. Displacement experiments demonstrate that the permeability reduction rate decreases significantly with increasing particle hydrophobicity. Thermodynamic analysis suggests that the work of adhesion on the modified particle surface was reduced by 93.3%, thereby weakening fluid–particle interfacial coupling and suppressing fine mobilization. This study provides a wettability-based approach for mitigating permeability damage caused by fine migration in unconsolidated sandstone reservoirs. Full article

The tribocorrosion behavior of AZ31 and WE43 was investigated during sliding wear tests in Hank’s balanced salt solution (HBSS) and pure water. While wear volume increased monotonically with load in air and water, HBSS exhibited a distinct non-monotonic trend; the maximum material loss occurred at the minimum load (0.98 N) and decreased at 2.94 N before rising again. This indicates that at low loads, degradation is primarily driven by accelerated chemical dissolution (tribocorrosion) rather than by purely mechanical abrasion. The magnitude of wear followed the order [HBSS] > [air] > [water] in the low-load range (0.98–1.96 N), whereas it shifted to [air] > [HBSS] > [water] in the high-load range (2.94–5.88 N). A comparison of the wear rate of the alloys shows that the wear rate in HBSS differs from that in water, depending on the hardness of the substrate, similar to conditions in air. Notably, the specific wear rate decreased as test duration increased under low loads, further suggesting that corrosion-induced volume loss significantly outweighs mechanical wear in this regime. The static corrosion test revealed that volume loss during tribocorrosion was higher than that under static corrosion conditions. While the deposition of corrosion products affected net volume loss, chemical dissolution remained the primary driver of the observed wear trends at low loads. Electrochemical data from anodic polarization curves confirmed that the specimen tested under a 0.98 N load exhibited lower corrosion resistance. Mechanistically, it was suggested that Cl⁻ ions contributed to the overall increase in wear, while NaHCO₃ specifically contributed to the increase in wear in the low-load range. Full article

Background and Clinical Significance: Retroperitoneal urinomas are uncommon complications that can arise following trauma, particularly in the context of congenital anomalies such as pyeloureteral duplication. These conditions pose significant diagnostic and therapeutic challenges, requiring a comprehensive and multidisciplinary approach to ensure optimal patient outcomes. Case Presentation: Here, we report the case of a 22-year-old male who presented to the emergency department with right lumbar and flank pain, nausea, and abrasions following a fall from a height. Initial imaging revealed a right-sided retroperitoneal urinoma and a rare congenital anomaly: complete pyeloureteral duplication with the upper pole draining into the right seminal vesicle. The patient underwent two surgical interventions, including the insertion of a ureteral stent and reimplantation of the ureter using a latero-terminal U trans U technique. Conclusions: This case highlights the complexity of managing traumatic retroperitoneal urinomas associated with congenital anomalies such as complete pyeloureteral duplication. It emphasizes the importance of timely surgical intervention to prevent complications and improve patient outcomes. Full article

Diamond bead wire saw cutting technology for coal seams is an effective approach for relieving pressure and enhancing permeability by forming internal slits within a coal seam. However, the current lack of solid theoretical guidance for cutting force models in loaded coal bodies makes it difficult to accurately predict cutting forces under underground conditions. This study established a three-dimensional cutting force model for wire saw cutting of loaded coal bodies. At the same time, comparative experiments were conducted using a self-developed experimental apparatus for cutting loaded coal with a wire saw. The research findings indicate that, during wire saw cutting of loaded coal bodies, increasing the cutting depth of the cutting force of a single abrasive grain by changing the load on both sides of the coal body changes the removal patterns of abrasive particles at different orientations on a single bead. This leads to a shift from plastic deformation to brittle deformation while widening the cutting contact area on both sides of the wire saw. The interaction of these aspects changes the cutting force exerted by the wire saw on loaded coal bodies. The experimental results revealed that under high-load conditions, the cutting force on the coal further increased during wire saw cutting. This suggests that the expansion of the cutting range plays a more significant role in increasing the cutting force than does the decrease resulting from changes in removal mode. These findings offer valuable theoretical insights for the process design of wire saw coal cutting technology. Full article

Starved lubrication poses a critical challenge to hybrid ceramic bearings operating under severe conditions. This study investigates the tribological behavior of carburized 20CrMo steel sliding against Al₂O₃ ceramic balls and GCr15 steel balls under dry sliding, with oil-lubricated tests as a reference. Under oil lubrication, the 20CrMo/Al₂O₃ pair exhibits superior wear resistance, attributed to the high hardness of the ceramic counterpart. Under dry sliding, however, this pair shows a slightly lower friction coefficient but a wear rate approximately three times that of the 20CrMo/GCr15 pair. This counterintuitive behavior stems from two mechanisms: lower contact stress and friction-induced work hardening in the GCr15 pair, which together suppress wear. Further analysis reveals that secondary carbides in the carburized layer detach under repeated high shear stress, acting as hard third-body abrasives and accelerating surface damage. These findings highlight that hybrid ceramic bearings are more susceptible to lubrication failure than all-steel bearings. Under heavy loads and poor lubrication, residual compressive stress plays a key role in governing the tribological behavior of carbides on carburized surfaces. Full article

Understanding how geometry governs interfacial contact and material removal is central to designing efficient bioinspired surface systems. Gastropod radular teeth form natural arrays of microscale cutting elements optimized for repeated interaction with compliant and semi-rigid substrates, yet experimentally validated shape–performance relationships remain limited. Here, we isolate geometric effects on interfacial mechanics using stereolithography-printed biomimetic tooth arrays inspired by the taenioglossan radula of the hard-substrate grazer Spekia zonata. Two morphologically distinct tooth types (central and marginal) were systematically varied in cusp and stylus geometry (four variants each), while array configuration, material, and boundary conditions were kept constant. Tooth stiffness was quantified in bending tests as load-induced height reduction. Interfacial performance was assessed using a controlled pull-through assay in agarose substrates of two stiffness levels (0.4% and 0.8%), with continuous force recording and measurement of removed mass. Marginal-tooth geometries were stiffer and consistently removed more substrate than central variants. Although work increased substantially in stiffer gels, removal did not scale proportionally and declined for central teeth, revealing a decoupling between mechanical input and yield. Performance correlated with active engagement rather than work alone, indicating geometry-limited contact regimes. These findings establish geometry-controlled stiffness and engagement as key parameters for efficient abrasive interfaces. Full article

Photothermal superhydrophobic surfaces represent a promising solution for passive anti-icing; however, the persistent high solar absorption of static black coatings often leads to undesirable overheating under non-icing conditions. To address this limitation, we developed a smart superhydrophobic polydimethylsiloxane (PDMS) surface embedded with thermochromic capsules (TC) (S-PDMS/TC) featuring reversible thermochromic capability via a facile combination of spin-coating and femtosecond laser ablation. The resulting hierarchical micro-grid structure acts as a sacrificial layer, shielding fragile nanostructures against mechanical abrasion, while endowing the surface with robust superhydrophobicity (contact angle > 155°). Uniquely, S-PDMS/TC exhibits an adaptive color transition from pale yellow to deep black when the temperature drops below 5 °C. This response enables on-demand photothermal enhancement, significantly boosting solar absorption in freezing environments while minimizing heat absorption at room temperature. Consequently, S-PDMS/TC demonstrates superior anti-icing performance, extending the freezing time to 310 s and reducing ice adhesion strength to 40.4 kPa. Notably, during photothermal de-icing, the meltwater exhibits spontaneous dewetting behavior driven by the replenishment of the air cushion, effectively preventing secondary icing. This work presents a mechanically durable and intelligent strategy for ice protection, successfully balancing efficient de-icing with thermal management. Full article

Ethylene–propylene–diene monomer rubber (EPDM) is commonly used as a gas-tight sealing material in electrical equipment. Factors such as media exposure, thermal oxidative stress, and abrasion frequently cause deterioration of EPDM’s mechanical properties, significantly compromising the reliability of electrical equipment. Traditional activator ZnO provides limited enhancement to the properties of EPDM. The reaction between Zn²⁺ on the surface of zinc oxide interacts with the accelerator during curing of rubber, forming zinc chelates, which interact with sulfur to form zinc polysulfide complexes. But the release of zinc complexes has adverse effects on humans and ecosystems. To reduce ZnO usage and further improve the performance of EPDM in terms of mechanical properties and aging resistance, zeolitic imidazolate framework-8 (ZIF-8) is developed as a multifunctional additive in this work. Mechanical testing demonstrates that the incorporation of ZIF-8 enhances the mechanical performance and resistance to thermal oxidative aging of EPDM. Crosslink density testing, FTIR, and XPS show that ZIF-8 promotes the crosslinking reaction during rubber curing, resulting in improved mechanical performance for EPDM. Analysis of crosslinking density testing and SEM images shows that EPDM-ZIF-8 composite exhibits a slower increase in crosslinking density during thermal oxidative aging. TGA results indicate that ZIF-8 enhances the thermal stability of EPDM, which leads to improved aging resistance properties. This study provides new insights for the design and development of rubber composite materials, offering a reliable solution to the challenge of seal failure in electrical equipment. Full article

Single-crystal 4H-SiC, as a wide-bandgap semiconductor material, has become a key substrate for high-power electronics and radio frequency devices due to its outstanding characteristics such as high-voltage tolerance, high-temperature stability, high-frequency efficiency and low loss. However, its inherent properties of high hardness and low fracture toughness also pose severe challenges to the ultra-precision processing of wafer substrates. In this study, through molecular dynamics methods, the influence of diamond abrasive grains with different sharpness on the processing of 4H-SiC at different grinding speeds was simulated, with a focus on analyzing its surface morphology, material removal behavior and subsurface damage characteristics. The structural evolution of 4H-SiC workpieces and diamond abrasive grains was identified through the radial distribution function, and the dynamic changes in temperature and stress during processing were further investigated to clarify the mechanism of abrasive wear and graphitization phenomena. The results show that regular octahedral abrasive grains with higher sharpness have better material removal efficiency, but they also cause more significant subsurface damage. Increasing the grinding speed helps to reduce the depth of subsurface damage. In addition, high temperature and high stress are the key factors leading to the transformation of diamond into graphite. Even under low-speed grinding conditions, the edges of the abrasive grains may still undergo graphitization due to stress concentration. The above findings have theoretical significance for an in-depth understanding of the material removal mechanism of 4H-SiC nano-grinding, and can also provide an important reference for the development of high-performance grinding wheels for SiC grinding. Full article

The surface characteristics of zirconia may influence both soft tissue response and bacterial colonization. This study evaluated the surface roughness and water contact angle of zirconia fabricated by additive manufacturing (material jetting, NPJ) and subtractive manufacturing (milling), and investigated human gingival fibroblast (HGF-1) viability and Streptococcus mutans (S. mutans) (ATCC 25175) adherence on these surfaces, as well as the possible correlation between roughness and bacterial adhesion. Sixty-four zirconia specimens (1 × 1 × 0.1 cm) were fabricated (n = 32 per group), sintered, and standardized by abrasive polishing. Surface roughness and contact angle were measured. Cell viability was assessed using an MTT assay at 24, 48, and 72 h. Bacterial adhesion was quantified after 24 and 48 h of incubation. Data were analyzed using two-way ANOVA, independent t-tests, and Pearson correlation (α = 0.05). No significant differences in HGF-1 viability were observed at 24 and 48 h; however, at 72 h, subtractively manufactured zirconia demonstrated higher cell viability than additively manufactured specimens (p < 0.001). S. mutans adhesion was significantly greater on additively manufactured zirconia at 24 h (p = 0.002), with no significant difference at 48 h. Manufacturing technique influenced surface properties and early bacterial adhesion. Both materials exhibited acceptable biocompatibility within the tested conditions. Full article

Numerous chemical and physical surface decontamination methods are used in clinical practice for implant surface decontamination, which constitutes the most critical step in the management of peri-implantitis. The aim of this study was to compare, in vitro, the efficacy of the electrolytic cleaning device GalvoSurge (GalvoSurge, GalvoSurge Dental AG, Widnau, Switzerland) with that of an air-abrasive AIRFLOW unit (AIRFLOW, Master PiezonVR, EMS Electro Medical Systems, Herrliberg, Switzerland). Thirty-two SLA-surfaced dental implants were allocated to two groups (n = 16) and contaminated with permanent ink, after which they were placed into jaw models representing two different defect configurations. After treatment, implants were photographed and, using ImageJ, the residual stain area/percentage within a 4 mm region apical to the implant neck was calculated. Surface topography was further evaluated by SEM and EDS. In the two-way analysis of variance, the effect of the decontamination method was statistically significant. The GalvoSurge group exhibited a lower residual stain percentage than AIRFLOW (overall 28.47 ± 10.13 vs. 37.14 ± 9.60; p = 0.019). This difference was independent of defect type (p > 0.05). These findings indicate that electrochemical cleaning via galvanic current may be more effective, under in vitro conditions, for stain removal and surface decontamination; however, they also demonstrate that residual contamination could not be completely eliminated irrespective of the method. Full article