Search Results (31)

The global energy transition and the implementation of carbon capture, utilization, and storage (CCUS) strategies require energy-efficient and scalable CO₂ separation technologies. Mixed-matrix membranes (MMMs), combining polymer matrices with functional inorganic or hybrid nanofillers, have emerged as advanced separation platforms capable of surpassing the conventional permeability–selectivity trade-off observed in neat polymer membranes. This review critically evaluates recent developments in modern hybrid membranes for CO₂ separation from synthetic and industrial gas mixtures, including CO₂/N₂ (flue gas), CO₂/CH₄ (natural gas and biogas upgrading), and syngas systems. Particular emphasis is placed on MMMs incorporating covalent organic frameworks (COFs), metal–organic frameworks (MOFs), graphene oxide (GO), MXenes, transition metal dichalcogenides (TMDs), carbon nanotubes (CNTs), g-C₃N₄, layered double hydroxides (LDH), zeolites, metal oxides, and magnetic nanoparticles. Reported performance ranges include CO₂ permeability (P_CO2) typically between 100 and 800 Barrer, CO₂/N₂ selectivity up to 319, and CO₂/CH₄ selectivity up to 249, depending on filler chemistry, loading, and interfacial compatibility. The mechanisms governing gas transport—molecular sieving, selective adsorption, facilitated transport, and diffusion-pathway engineering—are systematically discussed. Key challenges addressed include filler dispersion, polymer–filler interfacial defects, physical aging, moisture sensitivity, oxidation (particularly in MXenes), and scalability toward industrial membrane modules. Future perspectives focus on sub-nanometer pore engineering, surface functionalization to enhance CO₂ affinity, controlled alignment of 2D nanosheets to promote directional transport, multifunctional core–shell and hollow structures, and the integration of computational modeling and machine learning for accelerated material design. Modern hybrid MMMs are identified as strategically important materials enabling high-efficiency CO₂ separation processes aligned with decarbonization and energy transition objectives. Full article

Background: Flatfoot is a condition brought on by trauma, persistent foot stress, obesity, and poor biomechanics. These factors result in the development of a flat foot, collapse of the foot arch, and malfunction of the posterior tibial tendon. This study aimed to assess the immediate effects of Kinesio Tape on static plantar foot pressure and force in young females with flexible flatfoot. Methods: A pilot study (pre-experimental study design) with a convenience sample of 20 female subjects from a university with flexible flatfoot (age = 20.1 ± 1.3 years, weight = 91.8 ± 14.4 kg, height = 162.2 ± 6.3 cm, BMI = 34.9 ± 5, foot posture index (FPI) = 8.8 ± 2.1) was selected. The TekScan MatScan^® system was used to measure the static plantar forces and pressures, foot contact area, and the mediolateral displacement of COF over time while standing (Boston, MA, USA) before and immediately after the application of Kinesio Tape (KT). Results: While there were no statistically significant changes in the foot peak or total pressure, paired-sample t-tests showed a statistically significant reduction in foot contact area (p < 0.05) and a statistically significant increase in midfoot maximum force (p < 0.05) following the application of KT. Furthermore, after applying KT, there was a statistically significant decrease in the mediolateral COF velocity, indicating greater lateral displacement of COF (p < 0.05). Conclusions: The results of this study concluded that Kinesio Tape was a useful intervention method for immediately redistributing pressure and forces in young females with flexible flat feet. Full article

This study evaluates 10 bar water aging effects on reciprocating tribology of FDM-printed PLA and PLA with 10 and 15 wt.% glass fiber (GF). Water uptake was Fickian, and saturation mass rose from 0.0845 g (PLA) to 0.1625 g and 0.295 g (10 and 15 wt.% GF). Reciprocating tests at 40 N over 100 m at 0.5 and 1 Hz showed immersion time drives coefficient of friction (COF) and wear. At 0.5 Hz, neat PLA stabilized at COF 0.65 to 0.70 but increased to about 0.75 to 0.80 after 7-day; PLA + 10 wt.% GF reached about 0.80 to 0.82 after 14-day to 28-day. GF reduced unaged wear depth from about 125 µm to about 85 to 96 µm, yet 28-day aging increased depths to about 129 to 132 µm for both GF levels at 0.5 Hz. At 1 Hz, neat PLA peaked at about 235 to 240 µm depth after 7-day, whereas 15 wt.% GF reached about 160 µm after 28-day. Factorial analysis showed that wear scar width was primarily influenced by immersion time, accounting for 76.02% of the variation in the data, clearly evidencing strong dependence on the environment. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), glass transition temperature (Tg), and the melting temperature (Tm) support the occurrence of a transition from volume to interface-dominated damage with aging, while Tg and Tm remain unaffected. Full article

In the era of modern technology, tribo coupling components require efficient lubrication to ensure optimal performance, and to avoid significant material loss throughout the entire duty cycle. Solid lubricants, when reinforced with optimal contents, have shown the ability to improve the tribological performance and sustain the lubricious behavior over extended periods. The goal of this study is to improve the reliability and lifetime of tribo components used in a variety of industrial applications. The investigation explores the lubrication mechanisms, and optimizes the tribological behavior of the Ni-based alloy coating impregnated with molybdenum disulfide (MoS₂) and varying contents of silver (Ag). Specifically, four compositions containing 7 wt.% MoS₂ with different contents of Ag, i.e., 5, 10, 15, and 20 wt.%, were developed via the HVOF route and tested from room temperature (RT) to 800 °C. The optimal composition was determined using a parametric experimental optimization approach based on friction and wear minimization. In particular, the coating with 15 wt.% Ag showed the least friction and wear across all tested temperatures. The coating material having 15 wt.% Ag along with 7 wt.% MoS₂ attained a COF of 0.22 and wear rate of 5.3 × 10⁻⁶ mm³/Nm at 800 °C. The optimal content of Ag (15 wt.%) in the coating (NC15) decreased the wear rate by approximately 27% compared to the 20 wt.% Ag variant (NC20) at 800 °C. Overall friction and wear of the derived coatings decreased at 800 °C, with a minor increase at 400 °C. The apparent behavior demonstrated the complex interplay between coating ingredients and testing temperatures. The favorable tribo-chemical reactions and efficient boundary lubrication mechanisms worked together to reduce friction and wear. Full article

This study investigates the tribological response of basalt, carbon, and basalt–carbon hybrid laminates subjected to pressurized water-immersion aging and reciprocating sliding, with emphasis on the role of stacking sequence. Composite plates with B₈, C₈, B₂C₄B₂, and C₂B₄C₂ architectures were aged in deionized water at 10 bar for up to 30 days, then tested against a 100Cr6 steel ball at 30 N, 50 m track and 1 or 2 Hz. Water uptake ranged from approximately 4.3% for B8 to 1.2–2.7% for carbon-rich and hybrid laminates, and induced a depression and broadening of the epoxy glass-transition region that was most severe in basalt-skinned systems. At 1 Hz and 30-day aging, B8 exhibited the most severe damage, with wear-scar widths and depths approaching 3.0 mm and 0.50 mm, whereas C8 retained narrow shallow scars below 0.8 mm and 0.02 mm and COF values below 0.20. Increasing frequency to 2 Hz mitigated wear, reducing B8 depth to approximately 0.30 mm under similar conditions. Factorial analysis attributed more than 70% of the variance in wear width to laminate architecture. The combined pressurized immersion, multi-frequency reciprocating wear and DSC, profilometry, and SEM methodology provides an original framework to link hygrothermal plasticization to architecture-dependent tribological durability in hybrid basalt–carbon laminates. Full article

This study quantifies how pressurized water-immersion aging degrades the tribological response of cross-ply E-glass/polyester laminates by coupling dual-mode testing with surface metrology and factorial ANOVA. Eleven-ply [0/90]s plates were aged at 10 bar for 0, 7, 14, and 21 days, gaining 10% mass (72.2 to 79.4 g), then tested under 20 N in ball-on-disc (50–100 mm s⁻¹; 100–200 m) and reciprocating modes (1–2 Hz; 10–20 m). In ball-on-disc tests, steady-state COF rose from 0.40 to 0.47 (unaged) to 0.49 to 0.52 (14–21 days), and the low-friction run-in largely vanished with aging. Wear scar width and depth increased from 1.38 to 1.90 mm and 75 to 117 µm, respectively. Reciprocating tests showed a non-monotonic trend: moderate aging lowered COF to 0.50, whereas 21 days produced the harshest response (up to 0.78) and the widest/deepest scars (1.15 to 1.95 mm; 40 to 110 µm). ANOVA revealed that, in ball-on-disc tests, the COF was governed by sliding distance (28.70%) and speed (24.64%), with a strong Days × Speed interaction (31.66%); track-depth variance was dominated by distance (42.16%) and aging (32.16%). For the COF under reciprocating tests, aging was the leading main effect (21.21%), with large Days × Frequency (20.36%) and Days × Track (20.03%) interactions. Uniquely, this study isolates the effect of controlled hydrostatic aging (10 bar) and compares two sliding kinematics under identical loads, establishing quantitative thresholds (14 and 21 days) where interfacial debonding and third-body abrasion accelerate. Full article

This paper presents a holistic assessment framework for the impacts of water distribution pipe breaks to promote environmentally sustainable and socially resilient cities. This framework considers social, environmental, and economic vulnerabilities as well as probabilities associated with pipe failure. The integration of these features provides a comprehensive approach to understanding infrastructure risks. Taking the city of Vancouver as a case study, the social vulnerability index (SVI) is obtained following the application of a cross-correlation matrix and principal component analysis (PCA) to identify the most influential among 33 selected variables from the 2021 census of the Canadian population. The Environmental Vulnerability Index (EVI) is evaluated by considering the park and floodplain areas. The Economic Vulnerability Index (ECI) is derived from the replacement cost of pipes. These indices offer valuable insights into the spatial distribution of vulnerabilities (consequences) across urban areas. Subsequently, the Consequence of Failure (COF) is computed by aggregating the three vulnerabilities with equal weights. Pipe probability of failure (POF) is evaluated by a Weibull model calibrated on real break data as a function of pipe age. This approach enables a dynamic evaluation of pipe deterioration over time. Risk is finally assessed by combining COF and POF for prioritizing pipe replacement and rehabilitation, with the final objective of mitigating the adverse impacts of infrastructure failure. The findings show the significant impact of ethnicity, socioeconomic indices, and education on the social vulnerability index. Moreover, the areas close to English Bay and Fraser River are more environmentally vulnerable. The pipes with high economic vulnerability are primarily concrete pipes, due to their expensive replacement costs. Finally, the risk framework resulting from the vulnerabilities and pipe break probabilities is used to rank the Vancouver City water distribution network pipes. This ranking system highlights critical areas requiring different levels of attention for infrastructure improvements. All the pipes and corresponding risks are illustrated in Vancouver maps, highlighting that the pipes associated with a very high level of risk are mostly in the south and north of Vancouver. Full article

Al₂O₃ with SiC, silver, and graphene nanoplatelets (GNPs) powder mixture was produced by ball milling using ethanol as dispersion media. The GNP-reinforced Al₂O₃-SiC-Ag ceramic–metal composites were densified by spark plasma sintering technology (SPS). A homogeneous dispersion of GNPs in Al₂O₃-SiC-Ag was observed from the sintered samples, and the GNPs were embedded between the grains, which resulted in increasing the contact area. The trans-granular mechanism of crack propagation becomes increasingly dominant by adding GNPs. The hardness reaches 27 GPa, as tested by the Vickers microhardness method, which reflects an increase of 11% compared to Ag-GNPs-free Al₂O₃-SiC. On the other hand, by adding Ag-GNP content, the improvement in density is limited. Wear mechanisms, as determined through ball-on-flat testing, including adhesion, abrasion, and microcracks, are observed and discussed. The composite demonstrated remarkable self-lubricating properties, exhibiting a lower coefficient of friction (COF) and wear rate in an air environment compared to monolithic Al₂O₃-SiC. This improvement is attributed to the formation of a self-lubricating film, enabled by the uniform distribution of Ag and GNPs within the Al₂O₃-SiC matrix. The findings of this study propose a novel material design approach for developing self-lubricating ceramic composites with hybrid solid lubricants. Full article

In recent years, Golden Hard Anodizing (G.H.A.^®) has been developed as a variant of the traditional hard anodizing process with the addition of Ag⁺ ions in the nanoporous structure. The tribological properties of this innovative surface treatment are still not well understood. In this study, ball-on-disk tests were conducted in dry sliding conditions using 100Cr6 (AISI 52100) bearing steel balls as a counterbody and GHA^®-anodized EN AW-6082 aluminum alloy disks. The novelty of this work lies in the mapping of the wear properties of the tribocouple under different test conditions for a better comparison of the results. Three different normal loads (equal to 5, 10, and 15 N) and three different reciprocating frequencies (equal to 2, 3, and 4 Hz) were selected to investigate a spectrum of operating conditions for polished and unpolished G.H.A.^®-anodized EN AW-6082 aluminum alloy. Quantitative wear maps were built based on the resulting wear rate values to define the critical operating limits of the considered tribocouple. The results suggest that the coefficient of friction (COF) was independent of test conditions, while different wear maps were found for polished and non-polished surfaces. Polishing before anodizing permitted the acquisition of lower wear for the anodized disks and the steel balls. Full article

The increasing demand for high-performance aircraft engines has led to a greater emphasis being placed on advanced sealing coating technologies. Developing long-life, self-lubricating, and wear-resistant coatings is of significant research value. This study focuses on the fabrication of a novel self-lubricating and wear-resistant NiCoCrAlY-Cr₂O₃-AgMo composite coating. This coating was deposited onto a GH4169 substrate utilizing plasma spraying. Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) and X-ray diffraction (XRD) methods were employed to characterize the elemental composition and microstructure of the fabricated NiCoCrAlY-Cr₂O₃-AgMo composite coating. Microhardness measurements across the coating cross-section indicated a gradual increase in hardness from the GH4169 substrate to the NiCoCrAlY-Cr₂O₃-AgMo coating. The average hardness of the GH4169 substrate was 413.92 HV_0.2, while the CoNiCrAlY bonding layer region exhibited an average hardness of 467.60 HV_0.2. The NiCoCrAlY-Cr₂O₃-AgMo coating itself demonstrated an average microhardness of 643.22 HV_0.2. Room temperature friction tests indicated that the average coefficient of friction (COF) of the GH4169 substrate was 0.665. In contrast, the NiCoCrAlY-Cr₂O₃-AgMo coating exhibited a significantly lower average COF of 0.16, representing a 75.94% reduction compared to the uncoated GH4169 substrate. High-temperature friction tests were conducted at 400 °C, 500 °C, and 600 °C, indicating average COF values of 0.438, 0.410, and 0.268, respectively, for the NiCoCrAlY-Cr₂O₃-AgMo coating. Specifically, at 600 °C, the formation of a lubricious NiMoO₄ tribofilm on the coating surface was observed. This tribofilm effectively reduced the wear rate of the GH605 pin to 2.78 × 10⁻⁶ mm³/N·m, highlighting the potential of the NiCoCrAlY-Cr₂O₃-AgMo coating to reduce wear in high-temperature sliding contact applications. Full article

In this study, MoS₂ nanosheets have been prepared and treated ultrasonically with silver ammonia solutions. The MoS₂/Ag precursor was reduced using dopamine (DA) as reducing and linking agent at room temperature, and it was subjected to a hydrothermal treatment to produce MoS₂/Ag nanocomposites (denoted as MoAg). The MoAg samples were functionalized with N-oleoylethanolamine to improve dispersion in the base oil component of additives. Use of the functionalized MoAg (denoted as Fc-MoAg) as a lubricant additive for steel balls resulted in effective friction reduction and anti-wear. This work avoids ion exchange during exfoliation, and the Ag⁺ has been reduced to nano-silver particles by dopamine to enlarge the layer spaces of MoS₂. Taking the case of lubrication with base oil containing Fc-Mo_0.6Ag₁₅, the wear scar diameters and coefficients of friction of the steel balls were 0.428 and 0.098 mm, respectively, which were about three-fifths base oil. In addition, MoS₂/Cu and MoS₂/Ni nanocomposites were synthesized and the tribological properties associated with steel/steel balls assessed. The results demonstrate that all MoS₂/metal composites exhibit enhanced tribological behavior in the steel/steel pair tests. Both nanocomposite synergy and the tribofilm containing sulfide, oxide, carbide, and other compounds play important roles in achieving reduced friction and improved anti-wear. The friction and wear properties of base oil containing Fc-MoAg and commercial additives were evaluated using a four-ball wear tester with steel/steel, steel/zirconia and zirconia/zirconia pairs. The base oil containing Fc-MoAg delivered smaller coefficients of friction (COFs) and/or scarring groove depths than those observed with the use of pure base oil and base oil containing commercial additives. Full article

Nitrile Butadiene Rubber (NBR) is widely used as a sealing material due to its excellent mechanical properties and good oil resistance. However, when using NBR material, the seal structure is unable to avoid the negative effects of rubber aging. Hence, the influence of oil and thermal aging on the characteristics of NBR seals was studied by coupling the mechanical behavioral changes with the tribological behavioral changes of NBR in oil and the thermal environment. For this paper, aging testing and compression testing of NBR were carried out. Additionally, friction testing between friction pairs under different aging times was carried out. The surface morphology of the NBR working surface under different aging conditions was also observed. Finally, coefficients of different test conditions were introduced into the finite element model of NBR seals. It can be seen from the results that the elastic modulus increased with the increase in aging time in the thermal oxidative aging testing. The elastic modulus after 7 days of thermal oxidative aging increased by 135.45% compared to the unaged case, and the elastic modulus after 7 days of oil aging increased by 15.03% compared to the unaged case. The compression set rate of NBR increased significantly with the increase in aging time and temperature. The coefficient of friction (COF) between friction pairs increased first and then decreased with the increase in aging time. The maximum contact pressure decreased by 2.43% between the shaft and sealing ring and decreased by 4.01% between the O-ring and groove. The proportion of the effective sealing area decreased by 3.05% between the shaft and sealing ring and decreased by 6.11% between the O-ring and groove. Furthermore, the sealing characteristics between the O-ring and groove were better than those between the shaft and sealing ring. Full article

Untreated or inadequately treated silver−containing wastewater may pose adverse effects on hu−man health and the ecological environment. Currently, significant progress has been made in the treatment of Ag(I) in wastewater using adsorption methods, with adsorbents playing a pivotal role in this process. This paper provides a systematic review of various adsorbents for the recovery and treatment of Ag(I) in wastewater, including MOFs, COFs, transition metal sulfides, metal oxides, biomass materials, and other polymeric materials. The adsorption mechanisms of these materials for Ag(I) are elaborated upon, along with the challenges currently faced. Furthermore, insights into optimizing adsorbents and developing novel adsorbents are proposed in this study. Full article

In recent years, there has been significant attention on the application potential of medium and high-temperature self-lubricating composites as sliding parts in extreme environments. This study examines the effects of different Mo and Ag content on the composition and wear resistance of Ni60-cladded coatings at room temperature, 300 °C and 600 °C, while also analyzing their wear mechanism by studying the tribofilm. The results indicate that with an appropriate weight addition of Mo and Ag, one typical lubricant called Ag₂MoO₄ emerges. At room temperature, the cladding layer containing 5 wt.% Mo and 5 wt.% Ag exhibits a wear rate of 2.08 × 10⁻⁶ mm³/Nm, and an average coefficient of friction (COF) of 0.3410. These two are 85% and 11% lower than those of the Ni60 cladding layer, respectively. At 300 °C, MoO₃ and Cr₂MoO₆ act as solid lubricants. Furthermore, at 600 °C, a MoSi₂ and SiO₂ film forms on the worn surface to prevent further oxidation of MoSi₂ and enhance oxidation resistance. The main wear mechanism is adhesion wear. Under higher temperatures, the newly formed Ag₂MoO₄ in the composite cladding layer adopts a layered cubic spinel structure where low-energy Ag-O bonds preferentially break during friction processes, demonstrating excellent lubrication performance. Full article

In this study, nitrogen-doped carbon nanotube/Ag nanocomposites (denoted as N-C/Ag) have been synthesized in a urea solution using a hydrothermal method. The carbon nanotubes, AgNO₃ solution, urea and poly-dopamine (PDA) served as carbon, silver, nitrogen and carbon sources, respectively. The results show that the diameter of the carbon tubes was about 30 nm, and the Ag nanoparticles, with a diameter of ca. 10 nm, dispersed on the carbon tube surface. The Ag particle size decreased with a lower degree of crystallinity at a high temperature in the presence of urea. The friction and wear behavior of the oil acid (OA) modified N-C/Ag (OAN-C/Ag) as an additive in liquid paraffin (LP) were studied using a four-ball friction and wear tester. The results have shown that the coefficients of friction (COFs) and wear scar diameters (WSDs) of steel balls lubricated with LP-OAN-C/Ag decreased by 27.3% and 25.3%, respectively, relative to pure LP. Tribofilms containing Ag, carbon and nitride were formed on the worn steel ball surfaces. Details, the carbon, Fe₂O₃, azides and nitride, Ag and alloy and other compounds on the wear scars may improve tribological properties. The synergistic effect of carbon, Ag and urea plays a critical role during sliding. Full article