Search Results (261)

This study presents a computational analysis of degradation caused by cavitation and hydro-abrasive erosion in a low-head axial microturbine ($H=4\mathrm{m}$), incorporating strategic air injection as a passive mitigation technique. Using Computational Fluid Dynamics (CFD) within ANSYS CFX 2025 R2, the study investigates hydrodynamic performance and the spatial distribution of surface wear across the runner blades. The turbine geometry was developed from aerofoil profiles mapped onto cylindrical coordinates, using a structured three-dimensional mesh with localized refinement to ensure grid independence. Physical modeling employed the Shear Stress Transport (SST) turbulence model, with cavitation dynamics governed by the Rayleigh–Plesset equation and sediment transport modeled using a Lagrangian framework incorporating the Finnie erosion model. The numerical framework showed good agreement with reference characteristic curves, confirming its predictive accuracy. The results indicate that vapor cavities form predominantly on the suction side, whereas solid particle erosion highly concentrated on the pressure side of the blades, where the outer $20\%$ of the span accounts for over $91\%$ of the total erosion intensity. Parametric assessments of controlled air injection revealed a highly non-linear mitigation response, identifying IAVF 2 as the optimal air-injection case. This configuration reduced integrated erosion by $0.95\%$ and maximum localized erosion by $6.17\%$. In contrast, excessive air volumes accelerated material removal due to localized flow distortion. The findings indicate that carefully controlled air injection is a viable strategy for extending the operational lifespan of small-scale hydropower assets. Full article

Cementation of indirect restorations has undergone a profound change over the past century, evolving from a philosophy of purely mechanical cementation to sophisticated biomaterials science based on adhesion. The aim of this narrative review is to provide essential context for understanding contemporary clinical decision-making. A key aspect is the structural and compositional characteristics of enamel and dentin as bonding substrates, underlining why enamel remains the gold standard, while dentin continues to present significant challenges. The synthesis is based on evidence of adhesive strategies for the four main classes of contemporary restorative materials, such as glass-ceramics (lithium disilicate and leucite), polycrystalline zirconia, resin-matrix ceramics (hybrid ceramics), and indirect composites. Each material was detailed in terms of surface penetration (e.g., hydrofluoric acid etching and air abrasion), chemical coupling (e.g., silanization and MDP-based primers), and appropriate resin cement selection (light-cured, dual-cured, or self-adhesive). A step-by-step clinical protocol is synthesized based on current evidence, integrating critical techniques such as immediate dentin sealing and optimized polymerization. This review concludes that while adhesive resin cements provide predictable long-term results, significant challenges remain, guiding future clinical research and innovation. Full article

Cryogenic environments impose severe thermal and mechanical stresses on polymer components, yet the effects of long-term cryogenic cycling on their subsequent room-temperature performance remain insufficiently understood. This study investigated the influence of cryogenic cyclic aging on the mechanical and tribological behaviour of polyimide (PI)-based materials, including neat PI and composites reinforced with MoS₂, graphite, and/or PTFE. Repeated cryogenic cycling was followed by mechanical characterisation and tribological testing at 25 °C in air and vacuum. This work systematically compares neat and filled PI materials after cryogenic cyclic aging and correlates mechanical changes with transfer-film formation and wear behaviour. Cryogenic cyclic aging had only minor effects on weight and thermal stability but significantly altered the viscoelastic behaviour, increasing creep and residual strain, with variations depending on the polymer structure and filler content. Fracture toughness showed a statistically significant improvement only for PI2 (up to 93%). Changes in PI1, PI3, PI4, and PI5 fell within the experimental scatter and were interpreted as non-significant trends. In air, abrasive wear dominated in unreinforced PI, while graphite/PI composites exhibited adhesive wear and improved transfer film formation, reducing wear rates by up to 26%. In vacuum, the wear rate of aged graphite/PI increased by up to two orders of magnitude. Full article

This review explicitly focuses on agricultural attachments and executing components that interact directly with soil and crops, rather than the tractor vehicle itself. Operating within complex and variable farmland media environments, the key components of agricultural machinery have long been constrained by bottlenecks such as high-energy draught resistance, severe solid–liquid interfacial adhesion, and intense abrasive wear. Bionic functional surfaces, based on the coupling of micro-geometric morphology and surface-interface physical chemistry, provide a scientific approach to overcoming traditional tribological limitations by reconstructing the contact mechanics and fluid dynamics boundaries at the interface. This paper presents a comprehensive review of the latest research progress regarding bionic functional surfaces in the fields of friction reduction, wear resistance, and anti-adhesion in agricultural machinery. The article systematically categorises typical biological prototypes, such as soil-burrowing animals, aquatic organisms, and plant leaves, alongside their multidimensional feature extraction methods. It provides an in-depth analysis of core interaction mechanisms, ranging from static air cushion effects and dynamic wetting evolution to active electro-osmotic soil detachment, interfacial stress redistribution, and microscopic wear debris capture. Furthermore, it evaluates the efficacy of cross-scale coupled numerical simulation technologies in resolving interfacial interactions. At the engineering application level, this review extensively discusses the field performance of bionic structures in typical operational scenarios, including draught reduction in tillage and land preparation, blockage prevention in seed-metering channels, and low-damage harvesting in agricultural machinery. Finally, countermeasures are proposed to address the fatigue degradation of bionic surfaces under alternating field loads and the barriers to the large-scale fabrication of large-sized components. The paper further highlights the development trend towards the deep integration of bionic tribology with digital twins and intelligent wear-state perception technologies, aiming to provide systematic underlying theoretical and technical references for the research and development of the next generation of intelligent agricultural equipment characterised by low energy consumption and a prolonged service life. Full article

The anti-corrosion performance of epoxy coatings in saline solution environments is restricted by their surface hydrophilicity and microporous defects. Herein, we developed a modified epoxy (MEP)-based superhydrophobic anticorrosive coating by fluorinated resin matrix and incorporation of polyaniline@expanded graphite (FPANI@MEG) anticorrosive fillers. The FPANI@MEG fillers were fabricated via in situ polymerization of aniline on the surface of dopamine-modified expanded graphite to construct the micro-nano hierarchical structure required for superhydrophobicity, while providing barrier shielding and active passivation functions. The results showed that the final coating exhibited excellent superhydrophobicity with a water contact angle of 156.5 ± 1.8° and sliding angle of 3.0 ± 0.6°, along with excellent adhesion and adaptability to various complex environments. Meanwhile, the coating maintained superhydrophobicity after 400 cycles of Taber abrasion and 450 g of falling-sand impact, demonstrating hydrophobic robustness. Furthermore, the coating exhibited a low-frequency impedance modulus of 2.30 × 10⁷ Ω·cm² after immersion in NaCl solution for 15 days. The synergistic combination of air film shielding, physical barrier, and active passivation endowed the coating with good anticorrosion performance. This work may provide a theoretical reference for improving the corrosion protection of epoxy-based superhydrophobic coatings on carbon steel in aggressive saline solution environments. 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

Plaque-disclosing agents are widely used to enhance visualization of dental biofilm. However, their chromogenic components may adhere to enamel surfaces, resulting in transient extrinsic discoloration. This study evaluated the extent and short-term recovery of such discoloration and compared three removal modalities in terms of enamel color change (CIEDE2000, ΔE₀₀), surface roughness (Ra), and gloss (GU). Extracted human anterior teeth with intact buccal enamel were stained using an erythrosine-based disclosing agent and randomly allocated into three groups (n = 15): manual brushing with conventional toothpaste, rubber-cup polishing with a perlite-containing paste (1000 rpm, 5 s), or erythritol-based air-polishing (5 s; 50% power/100% water). ΔE₀₀ was measured at baseline, immediately after cleaning, and after 1 week of storage in artificial saliva. Ra and GU were recorded at baseline and post-cleaning. Data were analyzed using appropriate tests (p < 0.05). All modalities were associated with a reduction in visible discoloration without significantly affecting Ra or GU (p > 0.05). Immediate ΔE₀₀ values remained above commonly reported acceptability thresholds, indicating residual discoloration. Partial color recovery occurred after artificial saliva storage. Within the limitations of this study, the findings indicate no statistically significant differences among the tested procedures, without evidence of superiority of any single modality. Full article

Durability of clay-based mixes is often considered a limitation for their use in modern construction projects, especially in those involving additive manufacturing techniques. This study focuses on developing sustainable extrudable cob mixes and investigating the effect of sand particle grading, curing regime and mix composition on compressive strength, flexural strength, stress–strain response, capillary water absorption, wetting-drying cycles effect, and abrasion resistance. Results showed a significant positive impact of fine-sized sand addition into the mix on the mechanical strength and durability, due to better compaction and denser final cob mixes. Extending oven curing improves the compressive and flexural strength of all mixes due to the accelerated strength development from the higher temperature exposure. Lastly, the addition of high clay content allows for improving the compressive and flexural strength at prolonged curing aging under normal air-drying conditions. These mixes also exhibit low water absorption. Conversely, results revealed that the lime content plays a crucial role in reducing surface wear, with lime-rich mixes exhibiting lower erosion rates than the other mixes. Lime-stabilized cob mixes also demonstrate improved durability under cyclic wetting and drying. 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

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

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

Sustainable fertilizer technologies are essential to address nutrient losses, environmental pollution, and inefficiencies associated with conventional urea application. In this study, humic acid–functionalized starch (St–HA) gel coatings were developed and optimized via a Wurster fluidized-bed system to produce controlled-release urea granules, with an additional carnauba wax outer layer to further extend nutrient release duration. The coating formulation was synthesized through in situ crosslinking of tapioca starch with humic acid using N,N′-methylenebisacrylamide and potassium persulfate, yielding a cohesive film. A central composite rotatable design (CCRD) was employed to investigate the influence of atomizing air pressure, fluidizing air flow rate, fluidized-bed temperature, and spray rate on coating performance. Comprehensive characterization; including FTIR, XRD, rheological analysis, thermogravimetric studies, water retention, biodegradability, and surface abrasion, confirmed chemical crosslinking, structural stability, and mechanical robustness of the coatings. Nitrogen release analysis in both water and soil demonstrated a substantial extension of release longevity from less than 2 days (uncoated) to 18–20 days for St–HA-coated urea, and up to 28 days with the additional wax coating. Coated granules exhibited low abrasion (8–24%), high water-retention capacity, and 68% biodegradation in 60 days, ensuring environmental compatibility. The findings establish St–HA/wax hybrid coatings as a viable, eco-friendly strategy for controlled-release fertilizers, integrating renewable feedstocks with scalable industrial processing for precision nutrient management. Full article

The present study investigates the surface integrity and flank wear of uncoated cermet inserts during dry turning of AISI 304 stainless steel. Three-dimensional metrology techniques were employed to assess both surface roughness and cutting-tool flank wear. Cutting speed and feed rate were the process parameters varied in the experiments. Both parameters exhibited a significant influence on the final surface quality. Specifically, increasing the cutting speed resulted in a deterioration of the surface finish under the evaluated conditions. Considering an average flank wear (VBB) of 0.1 mm as the tool life criterion, tool lives of 15 min and 9 min were achieved at cutting speeds of 120 m/min (lowest level) and 150 m/min (highest level), respectively. At lower cutting speeds, abrasive wear and adhesion were the predominant wear mechanisms, whereas chipping and diffusion became more pronounced at the higher cutting speed. The dry turning of AISI 304 stainless steel with uncoated cermet inserts proved viable in terms of sustainability and surface integrity; however, effective chip evacuation remains a critical concern. The use of compressed air or minimum quantity lubrication (MQL) may help mitigate this issue. Full article

In computer-aided design/computer-aided manufacturing (CAD/CAM) restorations for severely damaged teeth, the cavity floor or proximal margins may be elevated with composite resin to improve adhesion. This in vitro study investigated how different surface pretreatment methods affect the shear bond strength (SBS) of hybrid CAD/CAM materials to dentin or composite surfaces, simulating clinical situations of composite elevation. Hybrid CAD/CAM samples were bonded to dentin or composite substrates following different surface pretreatment protocols and cemented using a dual-cure adhesive resin cement. The samples were thermocycled and subjected to shear bond strength testing, and failure modes were analyzed. The SBS in the sandblasting (SB)+Dentin group and hydrofluoric acid (HF)+Dentin was significantly higher than that in the SB+Composite and HF+Composite groups (p < 0.05). Untreated+composite and untreated+dentin groups showed significantly lower SBS (p < 0.05). Failure mode analysis revealed a predominance of cohesive failures in the SB+Dentin group, while adhesive failures were more frequently observed in most of the other groups. SB-treated and HF-etched hybrid CAD/CAM materials showed more favorable bonding behavior to dentin than to composite, highlighting that bonding to the elevated composite layer may be less effective than bonding directly to prepared dentin. Full article

Background/Objectives: Subcutaneous emphysema is a rare but potentially life-threatening complication of dental procedures caused by the penetration of pressurized air into submucosal tissues and its spread through cervicofacial and mediastinal spaces. This review aimed to summarize all reported cases of subcutaneous emphysema following periodontal interventions and to identify procedure and device-related etiologic factors associated with its occurrence. Methods: A comprehensive literature search was conducted, and case reports published between 1957 and 2025 were included without language restrictions. Cases related to trauma, maxillofacial surgery, endodontic, restorative, or prosthetic procedures were excluded. Results: A total of 34 publications reporting 36 clinical casesmet the inclusion criteria. The median patient age was 48 years (range: 8–76), and 66.7% of cases occurred in female patients. Air-powder abrasive devices were the most frequently implicated etiologic factor (66.7%), followed by dental lasers (11.1%) and air-water syringes (8.3%). Mediastinal spread was reported in 41.7% of cases. Most patients received prophylactic antibiotic therapy, and the median resolution time was 5 days (range: 3–14). Conclusions: Subcutaneous emphysema following periodontal interventions is most frequently reported in association with the use of pressurized air-driven devices, particularly air-powder abrasive systems. Although the clinical course described in the included cases was generally benign, the observed patterns highlight the relevance of procedural and device-related factors in the development and extent of this complication. Full article