Search Results (11,116)

The Weimei Formation, the most complete Upper Jurassic sedimentary sequence in the Tethyan Himalaya, is crucial for understanding the tectono-sedimentary evolution of the northern Indian margin. However, its depositional environment remains debated, with conflicting shallow- and deep-water interpretations. This study integrates sedimentary facies, petrography, zircon geochronology, and geochemical analyses to constrain the provenance, depositional environment, and tectonic setting of the Weimei Formation. The results reveal that the sedimentary system primarily consists of shoreface, delta, and shelf facies, with locally developed slope-incised valleys. Detrital zircon ages are concentrated at ~468 Ma and ~964 Ma, indicating a provenance mainly derived from the Indian continent. Geochemical characteristics, such as high SiO₂, low Na₂O–CaO–TiO₂ contents, right-leaning REE patterns, and significant negative Eu anomalies, suggest the derivation of sediments from felsic upper crustal recycling within a passive continental margin. Stratigraphic comparison between southern and northern Tethyan Himalayan sub-zones reveals a paleogeographic “uplift–depression” pattern, characterized by the coexistence of shoreface–shelf deposits and slope-incised valleys. This study provides key evidence for reconstructing the Late Jurassic paleogeography of the northern Indian margin and the tectonic evolution of the Neo-Tethys Ocean. Full article

Introduction: Hospital-acquired infections remain a significant healthcare concern due to the persistence of pathogens such as Staphylococcus aureus and Escherichia coli on frequently touched surfaces. Conventional TiO₂ coatings are limited to UV activation, which restricts their application under normal indoor light. Combining TiO₂ with ZnO and employing green synthesis methods may overcome these limitations. Methodology: Biogenic TiO₂ and ZnO nanoparticles were synthesized using Bacillus subtilis under mild aqueous conditions. The nanoparticles were characterized by SEM, XRD, UV-Vis, and FTIR, confirming nanoscale size, crystalline phases, and organic capping. A multilayer TiO₂/ZnO coating was fabricated on glass substrates through layer-by-layer deposition. Antibacterial activity was tested against S. aureus and E. coli using disk diffusion, direct contact assays, ROS quantification (FOX assay), and scavenger experiments. Statistical significance was evaluated using ANOVA. Results: The TiO₂/ZnO multilayer exhibited superior antibacterial activity under visible light, with inhibition zones of ~15 mm (S. aureus) and ~12 mm (E. coli), significantly outperforming single-component coatings. Direct contact assays confirmed strong bactericidal effects, while scavenger tests verified ROS-mediated mechanisms. FOX assays detected elevated H₂O₂ generation, correlating with antibacterial performance. Discussion: Synergistic effects of band-gap narrowing, Zn²⁺ release, and ROS generation enhanced visible-light photocatalysis. The multilayer structure improved light absorption and charge separation, providing higher antimicrobial efficacy than individual oxides. Conclusion: Biogenic TiO₂/ZnO multilayers represent a sustainable, visible-light-activated antimicrobial strategy with strong potential for reducing nosocomial infections on hospital surfaces and surgical instruments. Future studies should assess long-term durability and clinical safety. Full article

This work investigated the effect of cerium (Ce) addition on the wear behavior of commercially pure titanium (CP-Ti) by varying the Ce content to 0.8, 1.4, and 2.0 wt.%. Alloys were fabricated using plasma arc melting, and wear resistance was evaluated under loads of 1 N and 5 N dry sliding condition. Microstructural characterization confirmed the formation of CeO₂ precipitates, whose size and distribution varied with the Ce content. The Ti-0.8Ce alloy exhibited the highest hardness (203 HV), showing a 35% increase compared to CP-Ti, and the lowest wear rate reduced by approximately 47% and 22% under 1 N and 5 N loads, respectively. In contrast, Ti-1.4Ce and Ti-2.0Ce formed coarse CeO₂ precipitates, which acted as third-body abrasives. Although these alloys showed lower average friction coefficients than CP-Ti (up to 22% reduction), the enhanced abrasive interaction promoted material removal and increased wear rates. Notably, Ti-2.0Ce exhibited the most severe degradation in wear resistance, with wear rates increases of 21% and 27% under 1 N and 5 N loads, respectively. These findings demonstrate that while CeO₂ precipitates reduce friction by suppressing direct metal–metal contact, their abrasive nature adversely affects wear resistance when the particle size and volume fraction are excessive. Therefore, 0.8 wt.% Ce was identified as the optimal composition for improving the wear resistance, achieving the best combination of high hardness, low wear rate without excessive third-body abrasion. Full article

The long-term corrosion behavior of Al₂O₃-3%TiO₂ (AT3) coatings doped with1%, 5% and 8% CeO₂ prepared by plasma spraying was studied in 5% NaCl solution. The results showed that the protective performance of CeO₂-doped coatings was significantly higher than that of undoped coatings, primarily due to the reduction in coating porosity caused by the addition of rare-earth elements. Among the doped coatings, the 5% CeO₂-doped coating exhibited the best protective performance. The addition of rare-earth oxides CeO₂ reduced the content of γ-Al₂O₃ in the coating, but when the concentration of CeO₂ increased to 8%, the Ce element was rich in the gap of the coating. Excessive CeO₂ enriched in the gaps and coexisted more with Ti, and prevented the formation of the AlTi phase, which affected the performance of the coating. Electrochemical and XPS results revealed that an appropriate amount of Ce atoms or CeO₂ particles could fill the pores of the coating. During long-term immersion, Ce (IV) was converted to Ce (III), which demonstrated that Ce atoms have high chemical activity in coatings. The thermodynamic calculation results show that more CeO₂ particles improved the adsorption of corrosive ions. It indicated that the content of doped rare-earth oxides exceeding 5% would be utilized as an active material in the corrosive process. Full article

Aluminum and its alloys are widely used in aerospace and industrial sectors due to their high specific strength, low density, and abundance. However, their low hardness, high corrosion susceptibility, and poor wear resistance limit broader applications. Surface treatments such as electroplating, PVD/CVD, and anodizing have been used to enhance surface properties. Plasma electrolytic oxidation (PEO), also known as micro-arc oxidation (MAO), has emerged as a promising technique for producing durable ceramic coatings on light metals like Al, Mg, and Ti alloys. In this study, PEO was applied to AA6061 aluminum alloy using an AC power source in potentiostatic mode at 350 V and 400 V, 1000 Hz, and 80% duty cycle for 30 min in a silicate-based electrolyte (5 g/L Na₂SiO₃ + 5 g/L KOH) maintained at 25–40 °C. The effect of voltage on the coating morphology, thickness, and corrosion resistance was investigated. The coatings exhibited porous structures with pancake-like, crater, and nodular features, and thicknesses ranged from 0.053 to 83.64 µm. XRD analysis confirmed the presence of Al, α-Al₂O₃, Ƴ-Al₂O₃, and mullite. The 400 V-coated sample showed superior corrosion resistance ( $E_{corr}= -0.77 \mathrm{V}$; $i_{corr}=0.28 \mu \mathrm{A}/{\mathrm{c}\mathrm{m}}^2$) and improved hardness (up to 233 HV), compared to 89 HV for the bare AA6061. Full article

The increasing environmental presence of metal oxide nanoparticles (NMOPs) raises concerns regarding their influence on biological wastewater treatment. This study comparatively evaluates the structural and biological effects of zinc oxide (ZnO-NPs) and titanium dioxide (TiO₂-NPs) nanoparticles on activated sludge from a wastewater treatment plant. Experimental exposure covered nanoparticle concentrations of 0.05–0.3 g/L and contact times up to 180 min, with analysis of enzymatic activity (dehydrogenase activity, TTC-SA method), sludge settleability, and particle size distribution. Inhibition of microbial metabolic activity was observed in a clear dose- and time-dependent manner, with ZnO-NPs showing stronger toxicity than TiO₂-NPs. At the highest dose (0.3 g/L), enzymatic activity nearly disappeared after 90 min (0.04 µg TPF/mg MLSS). Both nanoparticles caused floc fragmentation, decreased sludge volume index (SVI), and increased the proportion of ultrafine particles (<0.3 µm). ZnO-NPs induced more severe destabilization, while TiO₂-NPs showed partial re-aggregation of suspended particles at higher concentrations. Additionally, particle size distribution in the supernatant was analyzed, revealing distinct aggregation and fragmentation patterns for ZnO- and TiO₂-NPs. These structural and functional alterations suggest potential risks for treatment efficiency, including reduced nutrient removal and impaired sludge settleability. The study provides a comparative contribution to understanding toxicity mechanisms of ZnO- and TiO₂-NPs and emphasizes the need to monitor NMOPs in wastewater and to develop mitigation strategies to ensure stable plant operation Full article

This study investigates the mechanism behind the heat-induced color change (brown to yellowish green) in Mn- and Fe-rich elbaite tourmaline under reducing atmosphere at 500 °C. A combination of analytical techniques including gemological characterization, electron microprobe analysis (EMPA), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and ultraviolet–visible (UV-Vis) spectroscopy was employed. Chemical analysis confirmed the samples as intermediate members of the elbaite–fluorelbaite series, with an average formula of ^X(Na₀.₆₆ □₀.₂₆ Ca₀.₀₈) _Σ1.₀₀^Y(Li₁.₂₉Al₁.₁₀Mn₀.₃₁ Fe²⁺₀.₁₅Ti₀.₀₁Zn₀.₀₁) _Σ2.₈₇ ^ZAl₆^T[Si₆O₁₈] (BO₃)₃^V(OH)₃.₀₀^W(OH₀.₅₁F₀.₄₉) _Σ1.₀₀, enriched in Mn (17,346–20,669 μg/g) and Fe (8396–10,750 μg/g). Heat treatment enhanced transparency and induced strong pleochroism (yellowish green parallel c-axis, brown perpendicular c-axis). UV-Vis spectroscopy identified the brown color origin in the parallel c-axis direction: absorption bands at 730 nm (Fe²⁺ d–d transition, ⁵T_2g → ⁵E_g), 540 nm (Fe²⁺→Fe³⁺ intervalence charge transfer, IVCT), and 415 nm (Fe²⁺→Ti⁴⁺ IVCT + possible Mn²⁺ contribution). Post-treatment, the 540 nm band vanished, creating a green transmission window and causing the color shift parallel the c-axis. The spectra perpendicular to the c-axis remained largely unchanged. The disappearance of the 540 nm band, attributed to the reduction of Fe³⁺ to Fe²⁺ eliminating the Fe²⁺–Fe³⁺ pair interaction required for IVCT, is the primary color change mechanism. The parallel c-axis section of the samples shows brown and yellow-green dichroism after heat treatment. A decrease in the IR intensity at 4170 cm⁻¹ indicates a reduced Fe³⁺ concentration. The weakening or disappearance of the 4721 cm⁻¹ absorption band of the infrared spectrum and the near-infrared 976 nm absorption band of the ultraviolet–visible spectrum provides diagnostic indicators for identifying heat treatment in similar brown elbaite–fluorelbaite. Full article

The efficient degradation of antibiotics in pharmaceutical wastewater remains a critical challenge against environmental contaminants. Conventional photocatalysts face potential limitations such as narrow visible-light absorption, rapid carrier recombination, and reliance on precious metal cocatalysts. This review investigates the coordination structure of MXene as a cocatalyst to synergistically enhance photocatalytic antibiotic degradation efficiency and the coordination structure modification mechanisms. MXene’s tunable bandgap (0.92–1.75 eV), exceptional conductivity (100–20,000 S/cm), and abundant surface terminations (-O, -OH, -F) enable the construction of Schottky or Z-scheme heterojunctions with semiconductors (Cu₂O, TiO₂, g-C₃N₄), achieving 50–70% efficiency improvement compared to pristine semiconductors. The “electron sponge” effect of MXene suppresses electron-hole recombination by 3–5 times, while its surface functional groups dynamically optimize pollutant adsorption. Notably, MXene’s localized surface plasmon resonance extends light harvesting from visible (400–800 nm) to near-infrared regions (800–2000 nm), tripling photon utilization efficiency. Theoretical simulations demonstrate that d-orbital electronic configurations and terminal groups cooperatively regulate catalytic active sites at atomic scales. The MXene composites demonstrate remarkable environmental stability, maintaining over 90% degradation efficiency of antibiotic under high salinity (2 M NaCl) and broad pH range (4–10). Future research should prioritize green synthesis protocols and mechanistic investigations of interfacial dynamics in multicomponent wastewater systems to facilitate engineering applications. This work provides fundamental insights into designing MXene-based photocatalysts for sustainable water purification. Full article

In this work, the photocatalytic reduction of CO₂ was innovatively tested with the simultaneous removal and mineralization of a textile contaminant, methylene blue (MB), which acts as a sacrificial agent. The process was carried out in a flow regime under atmospheric conditions, using a liquid-phase photoreactor under UVA illumination with a duration of 24 h per test. Two commercial TiO₂-based photocatalysts, P25 and P90 from Evonik, were used and surface modified through the photodeposition of metallic nanoparticles of Pt, Au, and Pd, as they did not show gas-phase products from CO₂ reduction on their own. The optimal pH was 5, the decreasing order of activity by metal was Pt > Au > Pd, and the optimal MB concentration was 20 ppm. The major products were CH₄ and H₂ in the gas phase. The presence of CH₄ was only detected in the presence of a CO₂ flow. In the liquid phase, carboxylic acids were also detected in small amounts, and in the test, 100 ppm of MB ethanol was additionally detected. A 100% degradation of MB and 72.5% mineralization was achieved under the conditions of highest CH₄ production (20 ppm MB at pH 5 with 4 g·L⁻¹ P25-0.70%Pt). Full article

Myanmar blue jadeite jade is a rare and highly prized gemstone, yet its coloration and formative mechanisms remain poorly understood. In this study, petrographic analysis, ultraviolet–visible (UV–Vis) spectroscopy, electron probe microanalysis (EPMA), and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) were performed on a sample of Myanmar blue jadeite with small white blocks to investigate its mineral composition, trace element distribution, and coloration mechanisms. Most of the sample was found to be blue, with surrounding white areas occurring in small ball-shaped blocks. The main mineral component in both the blue and white domains was jadeite. Although both areas underwent recrystallization, their textures differed significantly. The blue areas retained primary structural features within a medium- to fine-grained texture, reflecting relatively weaker recrystallization. The white areas, however, were recrystallized into a micro-grained texture, reflecting relatively stronger recrystallization, with the superimposed effects of external stress producing a fragmented appearance. The blue jadeite had relatively higher contents of Ti, Fe, Ca, and Mg, while the white jadeite contained compositions close to those of near-end-member jadeite. It was noted that, while white jadeite may have a high Ti content, its Fe content is low. UV–Vis spectra showed a broad absorption band at 610 nm associated with Fe²⁺-Ti⁴⁺ charge transfer and a gradually increasing absorption band starting at 480 nm related to V⁴⁺. Combining the chemical composition and the characteristics of the UV–Vis spectra, we infer that the blue coloration of jadeite is attributed to Fe²⁺-Ti⁴⁺ charge transfer; i.e., the presence of both Ti and Fe in blue jadeite plays a key role in its color formation. V⁴⁺ exhibited no significant linear correlation with the development of blue coloration. Prominent oscillatory zoning was observed in the jadeite, transitioning from NaAlSi₂O₆-dominant cores to Ca-Mg-Fe-Ti-enriched rims, reflecting the trend of fluid evolution during blue jadeite crystallization. Petrographic analysis indicated that the formation of the Myanmar blue jadeite occurred in two or three stages, with the blue regions forming earlier than the white regions. The blue jadeite also underwent significant recrystallization. Our findings contribute to the understanding of the formation of blue jadeite and the diversity of colors in jadeite jade. Full article

Titanium dioxide nanotubes (TiO₂ NTs) decorated with lead sulfide nanoparticles (PbS NPs) were synthesized using the Successive Ionic Layer Adsorption and Reaction (SILAR) method at different number (n) of cycles (where n = 3, 5, and 8) and evaluated for tetracycline (TC) photodegradation under UV light. PbS NPs/TiO₂ NTs heterojunctions prepared with 5 SILAR cycles showed optimal photocatalytic activity. Also, under optimized conditions, pure TiO₂ NTs achieved complete TC photodegradation (99%) within 5 h under UV irradiation, with a proposed degradation mechanism based on holes (h⁺) and hydroxyl radicals (•OH) as dominant reactive species. Full article

This study addresses critical bottlenecks in photocatalytic water treatment technologies, including difficulties in recovering traditional powdered catalysts, low mass transfer efficiency in immobilized reactors, and limited structural diversity. By integrating topology optimization with 3D printing technology, we designed and fabricated five types of triply periodic minimal surface photocatalytic reactors (TPMS-PCRs) with hierarchical porous structures—Fischer-Radin-Dunn (FRD), Neovius (N), Diamond (D), I-graph Wrapped Package (IWP) and Gyroid (G). Using fused deposition modeling (FDM), these TPMS configurations were manufactured from polylactic acid (PLA), 1.5 wt% TiO₂/PLA, and 2.5 wt% TiO₂/PLA. The catalytic degradation performance of these structurally distinct reactors for organic pollutants varied significantly. Notably, the FRD-type TPMS-PCR loaded with 2.5 wt% TiO₂ achieved a methylene blue (MB) degradation rate of 93.4% within 2.5 h under rotational flow conditions, compared to 87.5% under horizontal flow conditions. Full article

Filtration of submicron particles and nanoparticles is an important problem in nano-industry and in air conditioning and ventilation systems. The presence of submicron particles comprising fungal spores, bacteria, viruses, microplastic, and tobacco-smoke tar in ambient air is a severe problem in air conditioning systems. Many nanotechnology material processes used for catalyst, solar cells, gas sensors, energy storage devices, anti-corrosion and hydrophobic surface coating, optical glasses, ceramics, nanocomposite membranes, textiles, and cosmetics production also generate various types of nanoparticles, which can retain in a conveying gas released into the atmosphere. Particles in this size range are particularly difficult to remove from the air by conventional methods, e.g., electrostatic precipitators, conventional filters, or cyclones. For these reasons, nanofibrous filters produced by electrospinning were developed to remove fine particles from the post-processing gases. The physical basis of electrospinning used for nanofilters production is an employment of electrical forces to create a tangential stress on the surface of a viscous liquid jet, usually a polymer solution, flowing out from a capillary nozzle. The paper presents results for investigation of the filtration process of metal oxide nanoparticles: TiO₂, MgO, and Al₂O₃ by electrospun nanofibrous filter. The filter was produced from polyvinylidene fluoride (PVDF). The concentration of polymer dissolved in dimethylacetamide (DMAC) and acetone mixture was 15 wt.%. The flow rate of polymer solution was 1 mL/h. The nanoparticle aerosol was produced by the atomization of a suspension of these nanoparticles in a solvent (methanol) using an aerosol generator. The experimental results presented in this paper show that nanofilters made of PVDF with surface density of 13 g/m² have a high filtration efficiency for nano- and microparticles, larger than 90%. The gas flow rate through the channel was set to 960 and 670 l/min. The novelty of this paper was the investigation of air filtration from various types of nanoparticles produced by different nanotechnology processes by nanofibrous filters and studies of the morphology of nanoparticle deposited onto the nanofibers. Full article

Objective: Maxillofacial silicone elastomers represent a standard material in maxillofacial prosthetic applications due to their excellent biocompatibility and aesthetic properties. However, their long-term performance is limited by color degradation and susceptibility to fungal colonization. Incorporating nanoparticles into silicone matrices has emerged as a potential solution to enhance durability and hygiene. This study aimed to evaluate the effect of zinc oxide (ZnO) and titanium dioxide (TiO₂) nanoparticles used individually and in combination to evaluate the color stability and antifungal activity of pigmented maxillofacial silicone elastomers. Material and Methods: Fifty specimens were fabricated for each test and divided into five groups: Group (A) control (pigmented silicone only, no nanoparticles), Group (B) ZnO (1.5 wt%), Group (C) TiO₂ (2.5 wt%), and two combinations: Group(D1) (0.75 wt% ZnO + 1.25 wt% TiO₂) and Group (D2)(0.5 wt% ZnO + 0.83 wt% TiO₂) ratios. Color stability was assessed before and after 500 h of artificial aging using CIELAB-ΔE values and visual scoring. Antifungal activity was evaluated against Candida albicans using the disk diffusion method. Attenuated Total Reflectance with Fourier Transform Infrared Spectroscopy (ATR-FTIR), Scanning electron microscopy (SEM) along side with Energy-dispersive X-ray spectroscopy (EDS) were applied for Specimen characterization. Data were analyzed with one-way ANOVA and Tukey’s post hoc test (α = 0.05). Results: The dual-nanoparticle group with 0.75% ZnO and 1.25% TiO₂ demonstrated the best color stability (ΔE = 0.86 ± 0.50) and strongest antifungal activity (inhibition zone: 7.8 ± 3.8 mm) compared to the control (ΔE = 2.31 ± 0.62; no inhibition). Single-nanoparticle groups showed moderate improvements. A significant Association (r = 0.89, p < 0.01) was found between nanoparticle dispersion and material performance. Conclusions: Incorporating ZnO and TiO₂ nanoparticles into maxillofacial silicone elastomers significantly enhances color stability and antifungal efficacy. The combined formulation showed a synergistic effect, offering promising potential for improving the longevity and hygiene of maxillofacial prostheses. Full article

To solve the problem of purifying concentrates of rutile and zircon, a new method of electric separation after thermal activation roasting at 800 °C was proposed to strengthen the separation of Ti/Zr-bearing minerals. The results showed that the grade of TiO₂ in the conductor increased by 2.55~6.45% and the content of ZrO₂ decreased by 0.83~2.60% after thermal activation roasting and electronic separation, in contrast with electronic separation without roasting. To further explore the mechanism of activation roasting, the electrical conductivity, the phase evolution, and the microstructure of the gravity separation concentrate (GSC), pure rutile and pure zircon before and after roasting were investigated. The results of conductivity testing showed that the roasting pretreatment significantly improved the conductive difference between rutile and zircon, thus strengthening their separation performance. The XRD results revealed that the thermal activation roasting made the anatase in the GSC transform into rutile, thus enhancing the conductivity. Meanwhile, the crystallinity of both of the pure minerals was improved. The SEM results showed that the GSC particles formed loose and porous sinters, suggesting the reconstruction of the unstable anatase into rutile. Small amounts of cracks and protrusions occurred on the surface of both pure minerals, ascribed to the dehydration and deoxygenation at a high temperature. Full article