Search Results (1,702)

Orthophthalic unsaturated polyester resins are widely used in engineering applications due to their favourable mechanical properties, low cost, and ease of processing; however, their long-term durability under environmental exposure remains a significant challenge. Therefore, this study investigates the effect of selected nanofillers on the mechanical, surface, and tribological properties of orthophthalic unsaturated polyester resin composites. Carbon nanotubes (CNTs), halloysite, Cloisite^® 30B, nanoclay, and zinc oxide (ZnO) were incorporated into the polyester matrix at concentrations of 0.1, 0.25, and 0.5 wt.%. The environmental stability of the developed composites was evaluated through incubation in buffer solutions with pH values of 4, 7, and 9. Changes in pH values, sample mass and surface morphology were assessed before and after exposure. In addition, accelerated ageing and soil burial tests were conducted to evaluate the stability of the materials under different environmental exposure conditions. Changes induced by environmental exposure were evaluated using mass measurements, surface roughness analysis, morphological observations, and mechanical characterisation, depending on the applied exposure procedure. The surface characteristics of the composites were investigated using contact angle measurements and scanning electron microscopy (SEM). Mechanical and functional performance was further evaluated through scratch resistance testing in accordance with PN-EN ISO 1518:2023 and pull-off adhesion measurements. Tribological behaviour was determined for selected ZnO- and nanoclay-modified composites by evaluating the coefficient of friction, linear wear, wear track morphology, and surface topography. Furthermore, the gross heat of combustion of selected materials was determined according to PN-EN ISO 1716:2018. The obtained results provide a comprehensive comparison of the effects of nanofiller type and concentration on the mechanical, surface, tribological, and environmental behaviorpolyester resin composites. The results demonstrate that the investigated nanofillers affect different aspects of composite performance and that their effectiveness depends on both nanofiller type and concentration, indicating that nanofiller selection should be tailored to the properties required for the intended application. Full article

TiO₂ nanotubes and ZnO thin films were investigated as oxide-based memristive systems for resistive switching and state-endurance applications under variable environmental conditions. TiO₂ nanotubes were synthesized by electrochemical anodization, while ZnO thin films were deposited on Ti substrates by DC magnetron sputtering. Structural, chemical, and morphological properties were examined by Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. TiO₂ exhibited a vertically aligned nanotubular morphology, whereas ZnO showed a granular thin-film surface. Electrical characterization was performed using Au top electrodes and Ti as the bottom electrode under atmospheric pressure and high-vacuum conditions, with temperature varied from 353 K down to 77 K. Both materials exhibited hysteretic current–voltage behavior associated with resistive switching, although their response was strongly influenced by morphology, defect distribution, and environmental conditions. TiO₂ nanotubes showed stable high- and low-resistance states, with an ON/OFF ratio of approximately 4.65, indicating robust state endurance. The observed behavior was attributed to oxygen-vacancy-mediated transport, filament stabilization, and interface effects. These results highlight the relevance of comparing TiO₂ and ZnO nanostructures for identifying oxide systems capable of maintaining resistive states under temperature and pressure variations, supporting their potential for low-power non-volatile memory applications. Full article

In recent years, carbon nano-onions (CNOs), together with their functionalized derivatives, nanocomposites, and nanohybrids, have attracted increasing attention as sensing materials for monitoring relative humidity (RH), gases, and temperature. Their concentric graphitic structure provides good electrical conductivity, chemical and thermal stability, accessible surface sites, tunable surface chemistry, and compatibility with polymer matrices and flexible substrates. This review highlights recent advances in the synthesis and functionalization of CNOs and examines their integration into chemiresistive, surface acoustic wave, flexible, and printed sensing platforms. Particular attention is devoted to pristine and oxidized CNOs, heteroatom-doped materials, and composites incorporating hydrophilic or conducting polymers, metal oxides, and other functional fillers. CNO-based sensing layers demonstrate room-temperature (RT) detection of RH, hydrogen, ammonia, acetone, ethanol, isopropanol, carbon dioxide, hydrogen sulfide, and other volatile organic compounds. In addition, CNOs and CNO–polymer films exhibit significant temperature-dependent resistance variations, supporting their potential use in flexible and wearable temperature sensors. Although several CNO-based devices show superior performance in sensitivity, response, recovery characteristics, mechanical flexibility, and low-power operation, the studies on CNOs available in the literature remain limited compared with those on carbon nanotubes, graphene derivatives, and other carbonaceous materials. Further progress on CNO-based structures requires reproducible, large-scale synthesis; improved film uniformity and selectivity; standardized testing; compensation for temperature–humidity cross-sensitivity; and long-term stability studies. This review concludes by highlighting research directions to bridge the gap between laboratory prototypes and commercially viable CNO-based sensing devices. Full article

Improving the thermal conductivity of polymer/carbonaceous nanocomposites is still an interesting topic and is affected by a number of factors, such as polymer/nanofiller interaction, dispersion quality and agglomerate formation. In the present work, several polymer/nanocomposite types based on two different linear low-density polyethylenes (LLDPEs), as well as polylactic acid (PLA), reinforced with carbon nanotubes (CNTs) or a combination of CNTs/carbon nanofibers (CNFs) with graphene oxide (GO) at various loadings were investigated. The thermal diffusivity results for monofiller and hybrid nanocomposites with varying nanofiller loadings were analyzed. Additionally, existing models were employed to simulate the thermal conductivity using experimental data of both monofiller and hybrid nanocomposites. The model parameter values were utilized to explore the mechanism of the thermal conductivity increase, the role of CNTs and the synergistic effects of hybrid nanocomposites. Full article

Though many food systems on Earth offer benefits to space travelers, their ability to meet the demands of spaceflight remains unestablished. This study examines the application of magnesium oxide-coated halloysite nanotubes (MgO-HNTs), synthesized via electrodeposition, to enhance seed germination and early plant development under Earth, lunar, and Martian soil conditions. Successful surface modification was confirmed by scanning electron microscopy. Growth experiments with Heirloom Cherry Tomato and Golden Tomato seeds were conducted under hydroponic and soil-based conditions and subsequently extended to lunar and Martian regolith simulants. A Response Surface Methodology approach, based on a Box-Behnken Design, evaluated the effects of temperature, MgO-HNT concentration, and light duration on multiple growth responses, identifying seedling length and the root length stress tolerance index (RLSI) as the most responsive indicators of treatment. Optimal conditions (25 °C, 12 h photoperiod, 100 mg/mL MgO-HNTs) produced the greatest increases in root and shoot length in Earth soil. In lunar regolith, optimal root development occurred at 100 mg/mL (root length: 17.7 mm, shoot length: 5.08 mm, RLSI: 141.1%, germination: 80%), whereas Martian regolith peaked at 10 mg/mL (root length: 12.3 mm, shoot length: 4.28 mm, RLSI: 167.9%, germination: 100%), which may be associated with differences in the physicochemical properties of the two substrates. These findings offer preliminary evidence that MgO-HNTs can enhance early plant development across terrestrial and extraterrestrial substrates. As this study was limited to a single crop species under short-term, controlled laboratory conditions without direct physiological or biochemical biomarker measurements, further validation will be required to support broader agricultural or in-situ resource utilization (ISRU) applications. Full article

Alkaline water electrolysis (AWE) is a promising technology for sustainable hydrogen production, although its performance is limited by electrode overpotential, interfacial charge-transfer resistance, and limited electrochemically accessible surface area. In this study, a monolayer ternary carbon nanomaterial (CNM) composite comprising reduced graphene oxide (rGO), carbon nanotubes (CNTs), and Vulcan XC-72 was fabricated on stainless steel (SS) using a hybrid polyvinyl alcohol–polytetrafluoroethylene (PVA–PTFE) binder. Thermal treatment generated a porous conductive network that enhanced electrolyte accessibility and electron transport. Electrochemical characterization in 0.12 M NaOH showed that the CNM-modified electrode exhibited substantially higher current response and CV-derived double-layer capacitance (C_dl) of 62.61–78.51 mF/cm², compared with 3.43–3.74 mF/cm² for bare SS. Electrochemical fitting further showed markedly higher exchange-current density (i₀) parameters for the modified electrode, along with a reduced solution resistance (Rs) of ~2.1–2.2 Ω·cm² and a lower Rct. The oxyhydrogen (HHO) production rate reached 0.304 mL/min at 3.8 V, compared with 0.262 mL/min for bare SS at 4.0 V. Repeated HHO measurements showed ~2% variation (n = 3), indicating good reproducibility of the gas-production response. These results demonstrate that the rGO/CNT/XC-72 composite provides an effective and reproducible surface-engineering approach for enhancing electrochemical performance and HHO production in alkaline electrolysis systems. Full article

Lithium–sulfur (Li–S) batteries are promising next-generation energy-storage systems but are severely hindered by polysulfide shuttling, sluggish sulfur redox kinetics, and unstable Li₂S nucleation/growth behavior. Herein, a multifunctional MXene/carbon nanotube/poly(ethylene oxide) (MX/CNT/PEO)-modified separator is developed to regulate polysulfide behavior and improve interfacial electrochemical stability. In this composite architecture, MXene provides polar sites for lithium polysulfide adsorption, while carbon nanotubes construct interconnected conductive networks and suppress MXene restacking. The incorporation of poly(ethylene oxide) improves interfacial continuity and introduces additional oxygen-containing functionalities within the composite framework. Benefiting from the integrated effects of polar adsorption, conductive pathways, and structural integration, the MX/CNT/PEO-modified separator effectively suppresses polysulfide diffusion, reduces charge-transfer resistance, and promotes more favorable Li₂S nucleation/growth behavior. Electrochemical analysis shows that the charge-transfer resistance decreases from 175.9 Ω for pristine PP to 15.7 Ω for the MX/CNT/PEO@PP separator, corresponding to a 91.1% reduction. Potentiostatic Li₂S deposition analysis further supports favorable Li₂S nucleation/growth behavior on the MX/CNT/PEO-modified interface, after background subtraction. As a result, the Li–S cell with the MX/CNT/PEO@PP separator delivers a high initial discharge capacity of 1613 mAh g⁻¹ at 0.1 C and maintains average capacities of 1331.1 and 803.1 mAh g⁻¹ at 0.1 and 2 C during rate testing, respectively. During long-term cycling at 2 C, the cell retains 319.3 mAh g⁻¹ after 1000 cycles, with an average capacity decay rate of 0.064% per cycle. This work provides a rational composite-interlayer design strategy for multifunctional separator materials in high-performance Li–S batteries. Full article

Nanofillers are widely used to enhance the performance of polymer composites; however, their effectiveness strongly depends on their physicochemical properties and dispersion behavior. In this study, five commercially available nanofillers, namely multi-walled carbon nanotubes (CNTs), nanoclay, halloysite, Cloisite^® 30B, and zinc oxide (ZnO), were comprehensively characterized as potential modifiers of unsaturated polyester resin. The results confirm the characteristic chemical composition and crystalline structure of all investigated nanomaterials. CNTs exhibited the highest specific surface area (213.7 m² g⁻¹) and pore volume, whereas ZnO showed the lowest median equivalent particle diameter determined by laser diffraction (D₅₀ = 2.09 μm). The clay-based fillers displayed comparable particle size distributions, with D₅₀ values ranging from 8.29 to 9.00 μm. SEM observations revealed substantial differences in morphology and agglomeration state, with CNTs forming compact entangled agglomerates, while ZnO exhibited the most homogeneous microstructure. Suspension stability analysis demonstrated that particle size alone could not explain the observed sedimentation behavior. ZnO exhibited the highest dispersion stability, whereas halloysite and Cloisite showed progressive sedimentation. Nanoclay displayed delayed destabilization associated with agglomeration processes, while CNT suspensions were governed by structural rearrangements rather than classical sedimentation. The obtained results indicate that the dispersion behavior of nanofillers in unsaturated polyester resin is associated with differences in particle size, morphology, and agglomeration tendency. The presented comparative characterization provides a basis for the rational selection of nanofillers for polyester resin-based nanocomposites. Full article

Aiming at the problem that the selectivity of heterogeneous catalysts is difficult to be controlled and the active components are easy to be lost in the acetylene double carbonylation reaction, this paper constructs a highly efficient Pd-based catalyst through the combination of carrier morphology engineering and surface basicity regulation. Using melamine/urea as a precursor, tubular carbon nitride (TCN) was constructed by hydrothermal calcination, and then Pd/TCN-series catalysts were prepared by ultrasonic-assisted impregnation loading 5 wt% Pd and heat treatment in a N₂ atmosphere. At the same time, bulk g-C₃N₄ (BCN) and activated carbon (AC), TiO₂, and ZSM-5 supported systems were used as controls. The characterization results show that compared to BCN, TCN-500 (calcined at 500 °C) has a higher specific surface area (40.19 m²/g vs. 12.47 m²/g) and pore volume (0.1850 cm³/g vs. 0.0792 cm³/g), which provides abundant anchoring sites and efficient mass-transfer channels for Pd nanoparticles. After the introduction of Pd, the total base amount of the catalyst increased significantly from 0.4866 to 1.7172 mmol/g, and the strong Lewis-base center was significantly enhanced. TEM/XRD confirmed that Pd was uniformly dispersed on TCN-500 and mainly exposed the (111) crystal plane. XPS further revealed that there was a stronger electron-coupling effect between Pd and the support. Under the reaction conditions of 70 °C and 5 h, the selectivity of Pd/TCN-500 to dimethyl butenedioate was up to 83.7% (acetylene conversion was 59.6%), which was significantly better than that of the contrast carrier system. The cycle test showed that the selectivity and conversion of the catalyst were reduced to 54.4% and 41.1%, respectively, on the third use. The performance degradation was mainly attributed to the oxidative damage of the TCN nanotube skeleton and the passivation of the surface active defect sites. In this study, the synergistic effect of tubular morphology and surface Lewis basicity effectively stabilized the Pd active center and regulated the product selectivity, which provided a new idea for the development of efficient heterogeneous catalysts for acetylene double carbonylation in non-petroleum routes. Full article

Titanium dioxide nanotubes (TiO₂ NTs) fabricated by electrochemical anodization have attracted attention because their morphology can be regulated by processing parameters. Although the anodic fabrication of TiO₂ NTs has been widely studied, the morphology evolution of nanotubes on Ti6Al4V during secondary anodization after ultrasonic removal of the first nanotube layer still requires further clarification. In this study, anodic nanotubular oxide structures were fabricated on Ti6Al4V substrates by primary anodization and secondary anodization. The effects of anodization voltage, fluoride ion concentration, oxidation time, and secondary anodization on nanotube morphology were investigated. The results show that increasing anodization voltage promotes nanotube formation and increases tube diameter, whereas excessive oxidation time and high fluoride concentration lead to nanograss formation, tube collapse, and surface damage. Compared with primary anodization, secondary anodization produced smaller nanotube diameters and distinct morphology evolution, which may be associated with changes in the initial surface state after ultrasonic removal of the first nanotube layer. Among the investigated conditions, primary anodization at 40 V in 0.5 wt.% NH₄F electrolyte followed by secondary anodization at 50 V produced relatively regular nanotubular regions, although nanograss was also present on the surface. This work provides a process-oriented understanding of TiO₂ nanotube morphology regulation on Ti6Al4V substrates during primary and secondary anodization. Full article

Transparent and stable complementary inverters that can simultaneously support analog amplification and digital oscillation under optical stimulation are highly demanded for future see-through optoelectronic systems such as smart windows, augmented-reality interfaces, and on-skin photonic sensors. In this work, we report fully transparent, low hysteresis complementary inverters composed of a p-channel single-walled carbon nanotube (SWNT) thin-film transistor (TFT) with a top-gate iCVD pC1D1 polymer dielectric and an n-channel indium–gallium–zinc oxide (IGZO) TFT with a bottom-gate Al₂O₃ dielectric, both fabricated on ITO-coated glass substrates. The two TFTs exhibit well-matched output characteristics in opposite carrier polarities, enabling a CMOS-like inverter operation that delivers rail-to-rail switching, high voltage gain and a small hysteresis of less than 200 mV between forward and reverse sweeps. Furthermore, the UV photoresponse of the IGZO channel allows for systematic modulation of the inverter switching voltage (V_M) and small-signal gain with the incident UV intensity. Cascading the proposed inverter into three-, five-, and seven-stage ring oscillators yields stable rail-to-rail oscillation in which the oscillation frequency (f_osc) and the power consumption (P = C_L · V_DD² · f_osc · N) are tunable in real time by the UV intensity, realizing transparent light-to-frequency conversion at the circuit level. These results establish a route to low-power, see-through optoelectronic logic platforms that combine carbon-nanotube and oxide-semiconductor technologies on a common transparent substrate. Full article

Traditional petroleum coke-based porous carbons suffer from low specific surface area, insufficient surface active sites, and inferior rate and cycling performance. Herein, a series of sulfur/fluorine-co-doped hierarchical porous carbon (S+F-PC) cathode materials were synthesized controllably from industrial solid-waste petroleum coke via KOH high-temperature activation and heteroatom doping strategies. Polyaniline/carbon nanotube (PANI/CNTs) core–shell composites were fabricated as anodes through in situ oxidative polymerization, and S+F-PC//PANI/CNT asymmetric aqueous supercapacitors were assembled. The structural and chemical modulation mechanisms of dual heteroatom doping, as well as the electrochemical energy storage kinetics of electrodes and devices, were systematically investigated using SEM, TEM, XRD, XPS, BET, CV, GCD, EIS, and long-cycle tests. The results verify the synergistic modification effect of sulfur and fluorine co-doping. S-induced lattice distortion creates abundant mesopores and pseudocapacitive active sites, while F atoms stabilize the carbon skeleton to avoid high-temperature structural collapse and enhance the graphitization degree. The optimized S+F-PC exhibits an interconnected micropore–mesopore–macropore hierarchical network and a specific surface area of 172.2 m²/g, delivering a high specific capacitance of 477 F/g at 1 A/g, outperforming pure PC, and single-S-doped and -F-doped counterparts. The PANI/CNTs core–shell structure effectively alleviates the volume expansion of PANI during cycling, and the one-dimensional CNTs form a continuous conductive network. The PANI/CNT anode achieves a specific capacitance of 417 F/g, with a capacity retention of 91.4%, after 10,000 cycles. The assembled asymmetric supercapacitor realizes a stable voltage window of 1.6 V. It presents a specific capacitance of 117 F/g at 1 A/g, a maximum energy density of 41 Wh/kg at a power density of 2000 W/kg, and 87.2% capacity retention after 10,000 cycles. This work provides a feasible strategy for the high-value recycling of industrial-waste petroleum coke and the design of high-performance heteroatom-doped carbon electrodes and matched asymmetric aqueous supercapacitors. Full article

Titanium alloys are widely used for implants, yet corrosion, bacterial colonization and incomplete osseointegration remain important causes of interfacial failure. This review critically analyzes major biomedical functional coating fabrication techniques employed to enhance the surface properties of titanium alloys, including micro-arc oxidation, anodic oxidation, magnetron sputtering, electrochemical deposition, electrophoretic deposition, plasma spraying, physical vapor deposition, plasma immersion ion implantation, laser surface treatment, and hybrid (composite) approaches. For each method, key operational principles, structural and functional characteristics, performance advantages and limitations, and representative application domains are critically analyzed. Across these routes, biological performance depends on coating continuity, pore or nanotube geometry, interfacial bonding, phase composition and ion release. Calcium- and phosphorus-rich oxides and hydroxyapatite deposits generally promote cell adhesion, proliferation, alkaline phosphatase activity, mineralization and osteogenic differentiation. Dense oxide, nitride, tantalum and carbon-based films strengthen corrosion barriers, whereas Mn, Zn, Cu and Ag containing surfaces can inhibit bacterial adhesion and biofilm formation. Excessive ion release, however, may compromise cytocompatibility. Reported outcomes also vary with test medium, exposure time, bacterial strain and cell model. Standardized quantitative endpoints and longer-term corrosion, biofilm and osseointegration studies are required to guide clinically reliable multifunctional coatings. Full article

Supercapacitors offer high power density, fast charging/discharging capability, and long cycle life, yet their relatively low energy density limits broader deployment in electric vehicles, portable electronics, and grid storage systems. MXenes, a family of two-dimensional transition metal carbides, nitrides, and carbonitrides, have emerged as promising electrode materials due to their high electrical conductivity, tunable surface chemistry, hydrophilicity and intrinsic pseudocapacitive behavior. However, restacking of MXene layers reduces accessible surface area and ion transport efficiency, constraining electrochemical performance. To address this limitation, MXene-based nanocomposites incorporating carbon nanomaterials, conducting polymers, and metal oxides have been extensively developed. This review systematically evaluates recent advances in MXene-based nanocomposites for high-energy-density supercapacitors, highlighting electrochemical performance. A quantitative benchmarking comparison with commonly used electrode materials, including graphene, carbon nanotubes, and activated carbon, is provided. Key challenges in synthesis, performance standardization, and stability are discussed, along with future prospects for developing safer and scalable production methods of MXene-based electrodes. Full article

Carbon nanotubes (CNTs) have become one of the most widely investigated nanomaterials for gas sensing because their nearly one-dimensional geometry, large surface-to-volume ratio, hollow structure, and tunable metallic or semiconducting character allow trace adsorption events to be transduced into measurable electrical signals at or near room temperature. This review summarizes CNT-based gas sensors from a system-oriented perspective, linking four interconnected topics: (i) CNT structure, synthesis, and film/device fabrication; (ii) sensing mechanisms, including charge transfer, Schottky-barrier modulation, carrier-lifetime effects, and field-enhanced ionization; (iii) functional interfaces based on noble metals, metal oxides, conducting polymers, and graphene derivatives; and (iv) gas-specific and flexible/wearable device performance. Particular attention is given to recent room-temperature and mechanically compliant CNT-film sensors fabricated on polymer, cellulose, paper, textile, and mask substrates. Rather than cataloguing only individual response values, this review compares representative devices in terms of target gas, operating condition, sensitivity, recovery strategy, selectivity, humidity tolerance, and wearable relevance. The review concludes by discussing remaining challenges in reproducibility, selectivity, humidity compensation, recovery, power consumption, and standardization, and by outlining future directions toward robust, scalable, and intelligent CNT-enabled sensing systems. Full article