Search Results (287)

Alumina (Al₂O₃) ceramic sealing rings have attracted considerable attention in power battery packaging applications due to their excellent chemical stability, electrical insulation, and mechanical properties. In this study, 95% Al₂O₃ ceramics were fabricated using a CaO–SiO₂–TiO₂–ZrO₂ quaternary sintering aid system, and the effects of the TiO₂/ZrO₂ ratio on densification behavior, microstructural evolution, mechanical properties, and Mo–Mn metallization bonding performance were systematically investigated. As the TiO₂/ZrO₂ ratio decreases, the grain size first increases and then decreases, which is attributed to the pinning effect of the Al₂TiO₅ phase formed by excessive TiO₂ at grain boundaries that inhibits grain growth, whereas an appropriate TiO₂/ZrO₂ ratio promotes grain growth. After sintering at 1600 °C and 1625 °C, the density first increases and then decreases with decreasing TiO₂/ZrO₂ ratio; at 1650 °C, accelerated grain boundary migration engulfs residual pores into grain interiors, reversing the density trend. The flexural strength exhibits a rise–and–fall pattern with decreasing TiO₂/ZrO₂ ratio at all sintering temperatures, governed by the synergistic interplay among densification, grain size, and grain boundary characteristics. The metallization tensile strength first decreases and then increases with decreasing TiO₂/ZrO₂ ratio for ceramics sintered at 1600 °C and 1625 °C, but shows the opposite trend for those sintered at 1650 °C, governed by the glass–phase diffusion capability and surface roughness, respectively. The Al–2–2 sample (TiO₂/ZrO₂ = 1/1) sintered at 1650 °C exhibits the optimal overall performance, achieving a flexural strength of 351 ± 46 MPa and a metallization tensile strength of 153 ± 2 MPa. Full article

In helicopter rotor systems, effective suppression of lead–lag vibration requires dampers with reliable load transfer, appropriate stiffness matching, tunable damping, and efficient energy dissipation. However, conventional lead–lag dampers often suffer from limited stiffness–damping adjustability and sealing-related constraints. Here, we developed a magnetorheological fluid elastomeric (MRFE) damper by integrating magnetorheological fluid with a rubber elastomer. An elastomer system with a target shear modulus of 0.72 MPa was obtained through systematic design of the rubber formulation, rubber–metal bonding, and vulcanization process. Dynamic characterization showed that the dissipated energy increased markedly with amplitude but only slightly with frequency, whereas applied current exerted the strongest influence on the MRFE response. As the current increased from 0 to 1.5 A, the dissipated energy, effective stiffness, and equivalent damping coefficient increased by 1901.5%, 491.0%, and 961.1%, respectively. The zero-current effective stiffness of 0.443 kN/mm closely matched the required baseline stiffness of 0.44 kN/mm. For inverse current prediction, the improved Transformer model with hyperparameters optimized using PSO achieved a 72.04% lower RMSE than the differential evolution-assisted one-dimensional long short-term memory (DE-1DLSTM) model. These results suggest the potential of the MRFE for stiffness-matched support, controllable energy dissipation, and data-driven current prediction in rotor lead–lag vibration mitigation. Full article

Objectives: To compare, in vitro, the marginal and internal fit and marginal microleakage of preformed metal crowns (PMCs) placed with the conventional, Hall, and modified Hall techniques and cemented with three ion-releasing, resin- or glass-ionomer-matrix luting materials: a bioactive resin-matrix cement (ACTIVA^™ BioACTIVE-CEMENT), a bioceramic calcium aluminate cement (Calibra^® Bio), and a resin-modified glass ionomer cement (RMGIC; Riva Luting Plus). Methods: Forty-five extracted human primary molars were randomly allocated to three preparation groups (n = 15), each subdivided by cement (n = 5). After thermocycling (500 cycles, 5–55 °C, dwell time: 15 s, transfer time: 10 s), specimens were immersed in 1% methylene blue for 24 h, sectioned buccolingually, and examined by image analysis (ImageJ). Microleakage was quantified as the percentage of the crown–tooth interface showing dye penetration; marginal and internal fit were measured at thirteen points across marginal, axial, angular, and occlusal regions. Results: Marginal gap did not differ significantly among techniques or cements (p > 0.05). A significant region × technique interaction (p = 0.025) localised the technique effect to the angular region, where the Hall technique produced a larger gap than conventional preparation (p = 0.004). Microleakage was significantly greater for the Hall than the conventional technique (p = 0.045), with the modified Hall being intermediate. Cement had no significant effect, and fit and microleakage were uncorrelated. Conclusions: Preparation technique, rather than cement, was the principal determinant of seal and angular fit; ACTIVA^™ BioACTIVE-CEMENT and Calibra^® Bio performed comparably to RMGIC under the conditions tested. Clinical studies of a modified Hall technique incorporating a defined occluso-axial bevel are warranted to confirm these findings. Full article

The article presents a review of the current state of knowledge on the effect of surface characteristics on contact conditions and leakage in sealed joints with metal gaskets. The sealing mechanism is discussed, in which joint tightness is governed primarily by the deformation of microscale surface irregularities, the increase in the real contact area, and the disruption of the continuity of microgaps forming flow channels. Particular attention is given to the influence of contact geometry and surface topography on the leakage rate. The paper summarizes selected experimental studies on metal gaskets and discusses approaches to modeling the contact of rough surfaces and leakage at their interface. Taken together, the reviewed evidence indicates that reliable prediction of tightness requires simultaneous consideration of contact mechanics, material properties, loading conditions, and the surface geometric structure. The review identifies promising directions for the further development of contact and leakage models. The importance of modeling and the deliberate design of sealing and mating surfaces for improving joint tightness and reducing fluid losses and fugitive emissions is also highlighted. Full article

To analyze the performance stability of image intensifiers under humid and hot environments, this study systematically investigates the device performance degradation mechanism through a combination of natural exposure tests, humidity variation aging tests, disassembly analysis of failed samples, and a vacuum decay model. Experimental and simulated results reveal that moisture ingress in a humid and hot environment serves as the dominant factor governing the luminance gain stability of devices. Microscopic defects such as cracks, voids, and delamination phenomena existing at the sealing interface between ceramic rings and metal gaskets are the direct cause of moisture penetration. The attenuation of luminance gain accelerates significantly with increasing ambient humidity, demonstrating that water vapor is the primary driving factor for the environmental failure of devices. This study clarifies the attenuation mechanism of luminance gain for image intensifiers under humid and hot environments, providing a theoretical basis for the optimization of packaging processes and the improvement in environmental adaptability of image intensifiers. Full article

Microbiologically induced calcium carbonate precipitation (MICP) links microbial metabolism with carbonate biomineralization and offers a platform for environmental protection and a circular bioeconomy. This critical review synthesizes ureolytic and non-ureolytic pathways, including denitrification, sulfate reduction, photosynthesis, ammonification and carbonic-anhydrase-mediated routes, and evaluates their efficiency, scalability, environmental impacts and field applicability. MICP can immobilize heavy metals and metalloids, stabilize soils and mine wastes, reduce permeability, control erosion and dust, seal cracks in cementitious materials, and support brine or wastewater treatment. Representative studies report >90% Cd²⁺ removal in selected wastewater systems, 50–90% hydraulic-conductivity reduction at about 10–15% CaCO₃, 2.7 MPa compressive strength in urine-based bio-bricks, 31.87% calcium-source cost reduction using waste-limestone-derived calcium acetate, and geothermal-brine treatment removing 96% Ca, 88% Mn, and 91% Sr while retaining >96% Li. The review emphasizes that circular MICP requires more than waste input substitution; it must include nitrogen management, feedstock quality control, long-term contaminant stability, LCA/TEA, regulatory readiness, biosafety, field monitoring, and technology-readiness assessment. Future research should develop low-ammonia, waste-fed and data-guided MICP systems with standardized quantitative performance metrics. Full article

The first step in the analysis of the contact mechanics and leakage prediction of metallic seals applied to nuclear reactor pressure vessels is the proper characterization of the surface topography. At present, two approaches are used for this characterization. On the one hand, there are non-parametric techniques such as HPD and PSD, which retain all the characteristics of the surfaces that have been measured, but the results are high dimensional; hence, they cannot be analyzed analytically. The other type is parametric fractal methods, where the parameters used are fractal dimension D and characteristic scale G, where the analytical derivations can be made; however, this leads to systematic deviations in the mechanical response due to some idealized assumptions, like isotropy, Gaussian distribution, and infinite self-similarity. In this article, we propose an equivalent fractal parameter inversion model (EFPIM) that does not rely on geometric fitting; instead, it fits the mechanical contact behavior of a physical surface. This inversion procedure reduces three errors simultaneously. Thus, the EFPIM does not use D and G as the geometrical fitting variables but rather redefines them as mechanically equivalent ones, the purpose of which is to minimize the difference between the W-M fractal surface and the real measured surface. To address the problem of constrained inversion, we adopt a genetic algorithm with BFGS. To prove its effectiveness, we carried out experiments on C-ring seal surfaces and found that the deviation in the contact area was reduced by an order of magnitude in comparison to traditional structure-function extraction, and the deviation in the approach and the maximum pressure were less than 2%. Moreover, the equivalent parameters shift systematically away from their geometric counterparts in the direction that compensates for the dominant non-ideal deficit of the W-M surface; when both parameters are free, the equivalent fractal dimension decreases, while the equivalent characteristic scale increases, compensating for the absent non-Gaussian deep valleys of ideal W-M surfaces. Existing models of analytical contact and leakage may be directly implemented using equivalent parameters and with accuracy comparable to that of FFT-based simulations, with the modest cost of the offline computations. Full article

Methanol compression-ignition engines are vital for transport carbon neutrality, yet methanol’s low cetane number, corrosivity, low viscosity, and cavitation tendency compromised piezoelectric injector reliability. This study proposed systematic optimization strategies tailored to methanol’s fuel properties. A sealed thin-walled metal encapsulation, fabricated from precipitation-hardening martensitic stainless steel, was designed to isolate corrosive methanol media. The geometry of the tubular spring was optimized to meet the stiffness requirements for high-frequency injections. A monolithic nozzle without side pin holes, also upgraded to the same precipitation-hardening martensitic stainless steel, effectively suppressed stress corrosion cracking by leveraging the material’s combined high strength and excellent corrosion resistance. A dedicated return-line backpressure valve compensated for hydraulic leakage and improved fuel replenishment, and nozzle hole taper and inlet fillet radius were optimized to mitigate cavitation. Cold-motoring reliability tests showed the optimized injector maintained flow deviation within 3% after 100 million cycles, whereas the unoptimized prototype reached 8% deviation at 60 million cycles. The single-cycle injected fuel quantity coefficient of variation dropped from 4% to 1.3%. Spray characteristic comparison tests further confirmed that the optimized injector maintained stable flow consistency and atomization quality after prolonged cyclic operation. These optimizations effectively resolved corrosion, wear, and hydraulic instability caused by methanol, significantly enhancing flow consistency and durability over the service life. The results provided critical component-level technical support for advancing methanol compression-ignition engines from laboratory research to industrial application, addressing key reliability barriers that previously hindered engineering deployment of methanol-fueled powertrains. Full article

Long-term dry storage is a key stage in managing spent nuclear fuel (SNF) from sodium-cooled fast reactors, for which monitoring supports aging management and future fuel-cycle decisions. This study presents a monitoring-based condition assessment of BN-350 SNF stored in 60 UKKh-123 metal–concrete casks at the dedicated long-term container storage site of the «Baikal-1» research reactor complex. The casks were transported to and placed at this site in 2010, and their condition has been monitored annually. The assessment integrates dosimetric records, full-container campaigns from 2018 and 2023, and detailed inspection data for selected packages. The monitored indicators included external gamma dose equivalent rate, surface contamination, external surface temperature, visual condition, and leak-tightness of detachable sealing connections. For all 60 packages, the maximum gamma dose equivalent rates were 5.8–25.7 μSv/h in 2018 and 2.0–20.3 μSv/h in 2023, far below the nominal 500 μSv/h value specified for normal operation by the technical operating conditions. Surface contamination remained within applicable limits, and external surface temperatures were below the nominal 84 °C operating limit. A detailed inspection confirmed low gamma dose rates and satisfactory leak-tightness. The results support continued controlled storage with periodic monitoring and safety reassessment. Full article

To improve the bending resistance and support the domestic development of deepwater subsea wellhead equipment, a three-dimensional finite element model (FEM) of the SXW-15 subsea wellhead system was established in ANSYS Workbench considering contact nonlinearity and rigid-locking mechanisms. Based on representative deepwater drilling and completion conditions, the effects of the friction coefficient, locking preload, blowout preventer (BOP)/lower marine riser package (LMRP) top load, casing hanger internal pressure, and tubing load on the ultimate bending capacity of the system were systematically investigated. The results show that the bending capacity increases with increasing friction coefficient and locking preload, whereas it decreases with increasing top load and tubing weight. The internal pressure of the casing hanger exhibits a pronounced nonlinear influence on the bending resistance, and the maximum bending capacity occurs at an internal pressure of approximately 4000 psi. Based on the mechanical analysis, several innovative designs were proposed, including a layered load-bearing structure, a gravity-set metal sealing assembly, a self-supporting rigid-locking mechanism, and an integrated multifunctional tool system, aiming to improve load-transfer efficiency, connection stiffness, and high-pressure sealing stability. Land-based testing and offshore field applications were subsequently conducted to verify the engineering applicability of the system. The subsea wellhead system with innovative designs maintained satisfactory structural integrity and sealing reliability under conditions of 15,000 psi internal pressure and 12.7 million lb axial load. Good agreement was obtained between finite element predictions and field test results. The present study provides theoretical support and guidance for the structural designs and engineering applications of deepwater subsea wellhead systems. Full article

Lead and zinc mineralization have been documented in low-temperature Mississippi Valley type (MVT), Volcanogenic Massive Sulfide (VMS), and high-temperature porphyry and skarn ore deposits. These deposits are characterized by the precipitation of galena (PbS) and sphalerite (ZnS) from a saline hydrothermal fluid. The direct relationship between metal concentration and the total chloride of the fluid has been documented previously; however, the role of acidity has not been studied extensively. Experiments were conducted in René 41 cold-seal pressure vessels at temperatures of 200, 300, and 500 °C and a pressure of 100 MPa to provide better constraints on the formation of galena and sphalerite in hydrothermal systems spanning a range of fluid acidities (pH). The concentrations of Pb and Zn in the synthetic hydrothermal fluids were determined at galena and sphalerite saturation as a function of HCl and at a total chloride of 15 wt.% NaCl_eq.. Zn concentrations ranged from 1.7 (±0.3) × 10² µg/g at 200 °C and an HCl concentration of 2.28 × 10³ µg/g to 2.55 (±0.5) × 10³ µg/g at 500 °C and an HCl concentration of 3.40 × 10⁴ µg/g. Pb concentrations were 1.8 (±0.4) µg/g at 200 °C and a HCl of 2.28 × 10³ µg/g and increased to 7.93 (±1.5) × 10³ µg/g at 500 °C and a HCl concentration of 3.40 × 10⁴ µg/g. Zn/Pb mass ratios in the fluids at sphalerite and galena saturation decreased with increasing temperature. The experimental data demonstrate that the concentration of Pb and Zn in the fluid increase with both temperature and HCl concentration and, consequently, decrease with increasing pH. These results demonstrate that acidic fluids can transport substantially greater concentrations of Pb and Zn than neutral or basic fluids. Experimentally determined slopes of Pb and Zn concentrations as a function of HCl in the fluid provide empirical measurements of the apparent dependence of metal solubility on HCl at a constant total salinity. These results are consistent with Pb and Zn being transported predominantly as chloride-complexes under acidic, although the experiments do not directly determine aqueous metal speciation. Consequently, the experimentally determined HCl dependencies should be interpreted as empirical measures of apparent metal solubility rather than direct measurements of speciation or ligand coordination. The observed dependence of dissolved metal concentrations on HCl likely reflects the combined effects of chloride complexation, increasing HCl association with increasing temperature, non-ideal solution behavior, and changes in the distribution of dissolved chloride- and possibly sulfur-based complexes. Therefore, the neutralization of an acidic Pb- and Zn-bearing, chloride-rich hydrothermal fluid could produce substantial galena and sphalerite mineralization if sufficient reduced sulfur is available. In hydrothermal fluids depleted in reduced sulfur, H₂S must be supplied through sulfate reduction or by mixing with an H₂S-rich fluid to promote galena and sphalerite precipitation. Full article

Titanium remains the gold standard in dental implantology; however, its clinical drawbacks, such as hypersensitivity reactions, metallic particle release, and aesthetically compromising discoloration, have driven interest in metal-free alternatives. Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) has emerged as a promising bioceramic candidate, offering favorable aesthetics, mechanical strength, and reduced bacterial plaque affinity. Its pristine surface is nonetheless bioinert, prompting extensive research into surface modification strategies, including sandblasting, acid-etching, femtosecond laser texturing, and bioactive coatings, to enhance osteoconductivity. This comprehensive narrative review synthesizes in vitro evidence on the behavior of key host cell populations—macrophages, mesenchymal stem cells, osteoblasts, fibroblasts, and epithelial cells in response to Y-TZP surface and its modifications, relevant to osseointegration and soft-tissue sealing. A literature search was conducted across PubMed, Scopus, Web of Science, and the Cochrane Library, supplemented by Google Scholar, concluding in March 2026. By integrating findings across multiple cell lineages, this review aims to clarify how engineered zirconia topographies modulate cell-specific pathways, thereby informing the development of next-generation implants optimized for biological integration. Full article

To characterize the cross-scale coupling between macroscopic deformation and microscopic rough-surface contact in metal O-rings, this study proposes a macro–micro contact analysis and leakage flow regime identification method for metal O-ring sealing interfaces. Finite element analysis was employed at the macroscopic scale to obtain the sealing contact width and pressure distribution, while microscopic rough-surface morphology was characterized using fractal theory. Based on asperity contact analysis, the equivalent leakage channel height was determined, and the Knudsen number (Kn) was introduced to identify the fluid flow regime within micro-gaps. The results show that the O-ring cross-section flattens into an elliptical shape under compression, while the contact pressure exhibits a saddle-shaped distribution, and micro-gap leakage channels remain present. As the compression ratio increased from 5% to 25%, the sealing contact width and contact pressure increased, whereas the leakage gap height decreased significantly, resulting in an increase in the Kn values from 0.00176 to 0.045, 0.07, 0.155, and 2.78. Consequently, the flow regime evolved from continuum flow through the transition regime to molecular flow. The findings reveal the cross-scale coupling mechanism between macro–micro contact behavior and leakage flow regime evolution, providing practical guidance for determining the preload level and selecting appropriate leakage models in the engineering design of metal O-ring seals. Full article

Deep metal mines face increasing risks of water and sand inrush under complex fracture network conditions, where the unclear mechanism of slurry diffusion limits the reliability of horizontal curtain grouting. Taking the Cuihongshan iron–polymetallic mine as a case study, this paper establishes a stochastic three-dimensional discrete fracture network model and adopts an orthogonal experimental design to systematically investigate the effects of key engineering parameters on grout diffusion behavior. The results reveal that grouting pressure acts as the dominant controlling factor, significantly expanding the diffusion range and promoting the formation of continuous high-fill zones within the fracture network. Conversely, slurry viscosity exhibits a negative correlation with diffusion performance, leading to reduced inter-borehole connectivity as viscosity increases. Compared with conventional macro-indicators, the inter-borehole overlap rate provides a more precise quantitative measure of curtain continuity. The study demonstrates that achieving a sufficiently high overlap rate is critical for transitioning from discontinuous filling to a reliable impermeable curtain. These findings offer a theoretical basis for optimizing grouting parameters and evaluating sealing effectiveness in deep mine construction. Full article

The accumulation of non-recyclable construction, renovation, and demolition (CRD) wood waste necessitates sustainable management strategies, for which thermochemical valorization is a promising option. Slow pyrolysis is particularly suitable due to its high biochar yields and potential to partially replace fossil coal in energy, metallurgical, construction, and environmental applications. In this study, end-of-life CRD wood was converted into biochar using a pilot-scale vertical retort–kiln system at furnace set-point temperatures of 600 °C and 800 °C for 4 h. The biochar produced at 800 °C, which exhibited superior characteristics, was subsequently subjected to post-heat treatment at 600 °C for 30–90 min in the presence of nitrogen within a tightly sealed rotary retort-kiln assembly. Self-heating behavior was evaluated using adiabatic oven tests at 120–140 °C. Biochar properties were characterized by proximate and elemental analysis, TGA/DTG, R50, FTIR, and SEM–EDX. Increasing the pyrolysis temperature to 800 °C increased carbon content from 49.88% in the raw feedstock to 85.11% in biochar, while oxygen and hydrogen contents decreased to 5.91% and 1.52%, respectively. Van Krevelen ratios (H/C = 0.21; O/C = 0.05) indicated enhanced carbon stability, with the higher heating value reaching 30.81 MJ/kg. The thermostable fraction reached 75.18%, R50 recalcitrance index 0.57, fixed carbon 70.59%, volatile carbon 23.31%, pH 8.9, and surface area 188.33 m²/g. Post-heat treatment further enhanced aromaticity (H/C = 0.18; O/C = 0.02) of this higher pyrolysis temperature biochar, increasing its fixed carbon and stability, and reducing volatile content. Extending treatment time from 30 min to 90 min raised fixed carbon to 77–78% and thermostability to 84–85%, while volatile carbon decreased to 13–15%. Microporosity peaked at 350–380 m²/g by 75 min before declining due to pore widening. SEM and EDX analyses confirmed this structural evolution, increased carbon content, reduced oxygen, suppressed alkali metals, and enrichment of alkaline earth metals. Yield loss was highest at 90 min (20–21%), highlighting the need to balance treatment severity and biochar product yield. Both the 800 °C biochar and its post-heat-treated forms passed self-heating tests, confirming improved oxidative stability for energy and environmental applications. Full article