Green tea and aloe extracts were used for the green synthesis of TiO 2 NPs. TiO 2 NPs were characterized by UV‒visible spectrophotometry, SEM, HR-XRD, FE-TEM, EDS and FT-IR. The anatase and rutile mixture was obtained at 700 °C, whereas only rutile was synthesized at 1000 °C. Mostly irregular spherical shapes with aggregation were observed in SEM images. The extract affected the anatase/rutile content and crystallite size. At 700 °C, green tea extract resulted in the highest anatase content (94%), whereas the aloe extract resulted in the lowest anatase content (67%). At 1000 °C, the largest rutile (87.00±9.53 nm) was synthesized from green tea extract, whereas the smallest rutile (50.07±6.04 nm) was produced from aloe extract. Green tea extract exhibited a markedly higher DPPH radical scavenging activity compared to aloe extract, implying that polyphenol content is a key contributor to the distinct characteristics of the newly synthesized TiO 2 NPs. This report highlights a novel and significant approach by comparing the LC-ESI-MS phytochemical profiles of the extracts and elucidating their distinct impacts on the physicochemical properties of TiO 2 NPs.
Developing high-capacitance, binder-free electrode architectures with optimized charge-transfer pathways is crucial for advancing next-generation energy storage systems. An amorphous Ni–Co–Sn ternary oxides matrix was directly grown on azide-derived N-rGO scaffolds (NCS@az-N-rGO) using nickel foam as the current collector. Synthesis involved a straightforward co-electrodeposition step, after which the precursor underwent calcination at 300 °C under a protective nitrogen flow. The low-temperature thermal treatment plays a pivotal dual role: it transforms metal hydro-complexes into an amorphous ternary oxides matrix featuring abundant defect sites and isotropic ion channels, while simultaneously triggering nitrene intermediate chemistry from azide groups ( R – N 3 ) to yield high-density covalent nitrogen doping ( 43.84 at . % ). Benefiting from this structural synergy and binder-free interface, the NCS @ az ‐ N ‐ rGO electrode delivers an extraordinary specific capacitance of 3182 F g − 1 (areal capacitance of 1.59 F cm − 2 ) at 1 A g − 1 , maintaining 1662 F g − 1 even at a high current density of 10 A g − 1 with a negligible IR drop of 0.026 V . When assembled into an asymmetric device (AC//NCS@az-N-rGO) operating within a 0–1.5 V potential window, the system achieves a peak specific energy of 23 Wh kg -1 at a power density of 375 W kg -1 (retaining 7.2 Wh kg -1 even at an elevated power density of 7500 W kg -1 ). Furthermore, long-term stability testing reveals a 73.4% capacity retention over 10,000 continuous galvanostatic cycles at 1 A g -1 . Overall, this study outlines a reliable methodology to integrate amorphized mixed-metal oxides with functionalized carbon scaffolds for high-performance aqueous energy storage applications.
Titanium dioxide (TiO 2 ) exhibits dielectric properties that vary significantly with its physical morphology and thermal history. This work evaluates the dielectric responses of calcined nanopowder, electrospun nanofibers before and after heat treatment. Utilizing TEM, SEM, EDX, FTIR, and XRD allows for a detailed assessment of the morphological, and structure differences across the TiO 2 samples. The uncalcined nanofibers exhibit an amorphous structure with significant polyvinylpyrrolidone (PVP) content. Calcination transforms these amorphous precursors into crystalline fibers with a mixed anatase and rutile phase. Dielectric measurements carried out over a frequency range of 1 Hz to 1 MHz demonstrated that the calcined nanofibers feature a dielectric constant (ε′) that is both reduced and mostly stable across the measured frequency range. At higher frequencies, the dielectric constant was found to approach free-space permittivity, with the material additionally exhibiting low dielectric loss (ε″, tan δ), and reduced low AC conductivity (σ). The calcined TiO 2 nanopowders, and uncalcined fibers by contrast revealed higher ε′ values and more substantial losses. The calcined TiO 2 nanofibers thus exhibit superior insulating characteristics, demonstrating that nanostructuring combined with controlled thermal treatment can be effectively employed to alter dielectric performance. These findings carry meaningful implications for designing dielectric materials, particularly in enabling the optimization of low and stable dielectric permittivity alongside low-loss properties across a broad frequency range for electronic circuits applications.
Waterproof dam concrete’s permeability stability in goaf waterlogged environments critically impacts coal mine safety and groundwater sustainability. Underwater immersion, weak infiltration pathways are formed at the joint interfaces of the composite structure (concrete-concrete), potentially triggering water damage incidents. Optimization research on interface anti-seepage performance is urgently required. This study focuses on the composite structure of waterproof concrete dams, analyzing permeability modification by nano SiO 2 /TiO 2 /Al 2 O 3 at varying percentages on bi-material specimens post-immersion. Gas permeability, Liquid-measured porosity test, Ultrasonic velocity, and SEM were performed to evaluate the permeability evolution and interface stability of nanomaterial-modified concrete after different days of water immersion. Results indicate that post 14-day immersion, the permeability of ordinary concrete monomer specimens (OC) and bi-material specimens (C-C) increased to 0.236×10 -5 μm 2 and 0.760×10 -3 μm 2 , respectively, corresponding to degradation levels of 220.5% and 88.5%. Moreover, the permeability of C-C remained two orders of magnitude higher than that of OC, and their degradation followed a three-stage pattern: rapid amplification, moderate development, and gradual stabilization. Nanomaterial incorporation suppressed permeability deterioration, particularly the 0.5% TiO 2 group, showing optimal performance. Post-immersion, the 0.5%TiO 2 group showed 0.236×10 -3 μm 2 permeability, representing a 69.0% improvement relative to the C-C. Other groups demonstrated modification effects of 55.9% for 0.5%Al 2 O 3 , 52.6% for 1.0%Al 2 O 3 , 42.1% for 1.0%TiO 2 , and 24.4% for 0.5%SiO 2 , while the addition of 1.0%SiO 2 exhibited no significant improvement. Liquid-measured and ultrasonic tests showed the 0.5% TiO 2 group had 16.4% lower porosity and 14.2% higher wave velocity post-immersion. SEM analysis demonstrated that nano-TiO 2 effectively suppressed the expansion of interface cracks, and image binarization processing revealed a 49.6% reduction in fracture surface porosity in the 0.5%TiO 2 group, resulting in a denser interface microstructure and enhanced permeability stability. This study establishes key technical foundations for optimizing composite structural materials for waterproof concrete dams, thereby enhancing permeability stability in underground storage facilities and related engineering structures.
Ultrafine nano-silica, with its smaller particle size compared to conventional nano-silica, is typically synthesized via gas-phase methods that require complex raw materials and processes. Here, we report optimized conditions for preparing ultrafine nano-silica via a precipitation reaction between fluosilicic acid waste and aluminum hydroxide. The optimal conditions determined were as follows: reverse feeding, surfactant addition at 3.0%, aluminum-to-silicon ratio of 2.00, reaction time of 30 min, reaction temperature of 90 °C, and stirring rate of 250 rpm. Under these conditions, ultrafine nano-silica with a uniform particle size of approximately 11 nm was successfully synthesized. Characterization of samples prepared by different feeding methods showed that the reverse feeding method yielded ultrafine nano-silica with superior performance indicators compared to the forward feeding method. Analysis of system changes during synthesis indicated that the feeding method influenced the acidic or alkaline environment of the substrate, affecting SiF 4 hydrolysis and the subsequent dehydration and condensation of Si-(OH) 4 monomers, leading to variations in silica particle agglomeration. Further, an analysis of the effects of alkyl chains in surfactants on the surfaces of silica particles, including -OH substitution or Si-O-Si bond cleavage, provided insights into the action mechanism of surface groups on ultrafine nano-silica particles.
