Search Results (529)

Fractured lost circulation remains a major drilling challenge due to low compatibility between conventional plugging materials and fractures. By utilizing thermosetting resin emulsification and high-temperature crosslinking coalescence, this study developed a temperature-activated nanomaterial enhanced liquid–solid phase transition plugging emulsion. The system adapts to varying fracture apertures, forming plugging particles with a broad size distribution and high strength upon thermal activation. The structural characteristics, mechanical properties, and fracture-plugging performance of the plugging particles were systematically investigated. Results demonstrate that the optimized system, comprising 8 wt.% emulsifier, 0.16 wt.% dispersant, 0.4 wt.% crosslinker, 0.4 wt.% viscosifier, 70 wt.% distilled water, and 2 wt.% nano-silica (all percentages relative to epoxy resin content), can produce particles with a size of 1–5 mm at formation temperatures of 80–120 °C. After 16 h of thermal aging at 180 °C, the particles exhibited excellent thermal stability and compressive strength, with D(90) degradation rates of 3.07–5.41%, and mass loss of 0.63–3.40% under 60 MPa. The system exhibits excellent injectability and drilling fluid compatibility, forming rough-surfaced particles for stable bridging. Microscopic analysis confirmed full curing in 140–180 min. Notably, it sealed 1–5 mm fractures with 10 MPa pressure, enabling adaptive plugging for unknown fracture apertures. Full article

The performance of dental composites is strongly dependent on the type and content of ceramic fillers incorporated into the resin matrix. In this study, the effect of nanosilica (NS) fillers on the curing kinetics, physicochemical, thermal, and mechanical properties of Bis-GMA/TEGDMA-based dental composites was systematically investigated. A series of nanocomposites containing various weight fractions of NS was prepared and evaluated. The photocuring behaviour was analysed using differential scanning calorimetry (DSC), enabling the determination of polymerisation rate coefficients (propagation k_p and bimolecular termination k_t^b) and double bond conversion. The presence of nanosilica was found to influence chain mobility, as evidenced by changes in glass transition temperature (T_g). Rheological measurements provided insight into viscosity changes induced by NS incorporation, while mechanical tests confirmed reinforcement effects. A moderate but statistically significant correlation was observed between the NS content and mechanical performance. The results obtained correlate the rheological, kinetic, thermal, and mechanical properties of multiple types of silica in a single resin system using a consistent methodology. In addition, the results highlight the role of nanosilica in the regulation of the curing dynamics and the increase in the mechanical integrity of methacrylate-based dental composites, representing a promising strategy for the development of next-generation restorative materials. Full article

This study introduces an IoT-enabled smart greenhouse system tailored for rice cultivation and designed as a controlled experimental platform to evaluate fertilizer application methods. Traditional greenhouse farming often struggles with unpredictable weather, pest infestations, and inefficient resource use. To overcome these challenges, the proposed system optimizes environmental conditions and enables precise monitoring and control through the Thingsboard IoT platform, which tracks temperature, humidity, and sunlight intensity in real time. The cultivation process involved Inceptisol soil preparation, slurrying, fertilization, seeding, transplantation, and continuous monitoring. The novelty lies in its dual-purpose design, enabling both cultivation and structured agronomic experimentation under identical environmental conditions. The system enables both rice cultivation and comparative testing of nano-silica fertilizer applied via root (soil) and foliar (leaf) methods. Automated temperature control (maintaining 20–36.5 °C) and humidity regulation (10–85% RH) with a mist blower response time under 5 s ensured consistent conditions. Sensor accuracy was validated with deviations of 0.4% (±0.11 °C) and 0.77% (±0.5% RH). Compared to conventional setups, this system achieved superior environmental stability and control precision, improving experimental reproducibility. Its integration potential with machine learning models opens new possibilities for forecasting plant responses based on historical data. Overall, the study demonstrates how advanced technology can enhance agricultural precision, sustainability, and research reliability. Full article

This article investigates the synergistic effect of metakaolin waste (MW) derived from the production of expanded glass granules and nano-silica (NS) on the hydration and other properties of ultra-high-performance concrete (UHPC) reinforced with steel fibres. The study focusses on cases where 5%, 10%, or 20% of cement is replaced with MW and 1% of NS is added. Various properties are evaluated, including the exothermic temperature, mineral composition (XRD), relative main compound quantities according to their decomposition (TG and DTG), shrinkage, density, and flexural and compressive strengths after 7 days, 28 days, and 2 years. In addition, changes in the concrete microstructure are analysed after 28 days and 2 years. The results demonstrate that the combined addition of MW and NS accelerates hydration by about 3 h compared to the control sample. The TG results confirmed a lower portlandite content due to the dilution effect of cement replacement. However, when both additives were used simultaneously, the portlandite content decreased further because of the intensified pozzolanic reaction, while the amount of C–S–H increased. Using MW and NS together significantly enhanced the long-term strength of concrete: after 2 years, the compressive strength of the mix with 5% of cement replaced by MW and 1% of NS was 182 MPa, compared to 146 MPa for the control sample. Full article

This study presents a systematic evaluation of frost resistance in concrete modified with nano-alumina (NA, 1 wt%), nano-silica (NS, 2 wt%), and polypropylene fiber (PP, 0.2 wt%) through accelerated freeze–thaw testing. The investigation employed a comparative experimental approach, subjecting specimens with optimal mechanical dosages to 300 freeze–thaw cycles. The degradation was quantitatively assessed by monitoring the evolution of mass loss, dynamic elastic modulus, and compressive strength. Results reveal that PP-modified concrete demonstrates optimal performance, retaining 70% of its dynamic elastic modulus (vs. 68% for NA and 64% for control, and failing at 58% for NS after 200 cycles) and exhibiting only 9.3% compressive strength loss (vs. 13.9% for NA and 27.3% for control, and 43.6% for NS). These findings establish PP as the most effective modifier, offering both superior frost resistance (300+ cycle durability) and practical advantages (simpler processing, lower cost). The results provide a scientific basis for designing high-performance concrete in cold regions, with particular relevance to infrastructure requiring long-term durability under cyclic freezing conditions. Full article

Cementitious materials are multiscale and multiphase composites whose frost resistance at the macroscale is closely governed by microstructural characteristics. However, the interfacial transition zone (ITZ) between clinker and hydrates, recognized as the weakest solid phase, plays a decisive role in the initiation and propagation of microcracks under freezing conditions. Understanding the frost damage mechanism of ITZ is therefore essential for improving the durability of concrete in cold regions. The motivation of this study lies in revealing how freezing affects the mechanical integrity and microstructure of ITZ in its early ages, which remains insufficiently understood in existing research. To address this, a nanoscratch technique was employed for its ability to quantify local fracture properties and interfacial adhesion at the submicronscale, providing a direct and high-resolution assessment of ITZ behavior under freeze–thaw action. The ITZ thickness and fracture properties were characterized in unfrozen cement paste and in cement paste frozen at 1 and 7 days of age to elucidate the microscale frost damage mechanism. Moreover, the enhancement effect of nano-silica modification on frozen ITZ was investigated through the combined use of nanoscratch and mercury intrusion porosimetry (MIP). The correlations among clinker particle size, ITZ thickness, and ITZ fracture properties were further established using nanoscratch coupled with scanning electron microscopy (SEM). This study provides a novel micromechanical insight into the frost deterioration of ITZ and demonstrates the innovative application of nanoscratch technology in characterizing freeze-induced damage in cementitious materials, offering theoretical guidance for designing durable concrete for cold environments. Full article

Hybrid hydrophobic coatings (HHCs), which combine organic and inorganic materials, have demonstrated superior weathering resistance compared to conventional organic coatings in conserving stone heritage structures. Among the inorganic components of HHCs, nanosilica is especially promising because of its ability to form durable, weathering-resistant and hydrophobic silane-based structures. This overview examined recent studies, advances, and emerging trends about nanosilica-based HHCs from 2020 to 2024 using the “Boolean strategy” and search terms “stone”, “heritage”, “hydrophobic”, and “coating”, capturing 5244 articles. After screening for titles containing “nanosilica” (470 items remained), excluding works related to “consolidants” and “cement” (171 items remained), and requiring quantitative data on formulations, methods, and performance of nanosilica-based HHCs in stone heritage structures, 16 relevant works were identified. China and Italy dominated research works on nanosilica-based HHC development, which was applied to stone heritage structures composed of carbonate materials (e.g., limestone, dolomite, and Palazzolo carbonates) and silica-rich materials (e.g., Qingshi stone, Hedishi stone, and red sandstone). Key evaluation metrics reported by multiple authors to evaluate HHC efficacy included water contact angle (WCA), total color difference (TCD), and solution pH. Moreover, ultraviolet light (UV) durability, thermomechanical stability, biocidal efficiency, and graffiti protection were achieved when nanosilica was combined with other nanomaterials. Integrating emerging technologies, such as artificial intelligence (AI), internet-of-things (IoT), and smartphones with colorimeter apps could improve accessibility, real-time monitoring and reliability of HHC testing, while adherence to standardized testing protocols would further enhance comparability and practical application across studies. Overall, this overview provides valuable insights into nanosilica-based HHCs for researchers and restorers/conservators of stone heritage structures. Full article

Polyethylene (PE) melt-blown nonwoven materials exhibit excellent infrared transmission properties, making them well-suited for applications in infrared physiotherapy and smart building technologies. However, their high flammability and tendency to generate melting droplets and smoke seriously limit their applications. Herein, phosphorus-silicon flame-retardant PE melt-blown blends were prepared by the melt blending of ammonium polyphosphate (APP) and nano-silica (SiO₂). Next, the thermal, rheological, and crystallization properties of the blends were investigated. Subsequently, flame-retardant PE melt-blown nonwoven materials were prepared and tested. It was found that APP and SiO₂ decreased the melt flowability of the material, while slightly decreasing the melting point, increasing crystallinity and enhancing the thermal stability by shifting the decomposition temperature by 51 °C. Moreover, the presence of flame retardants increased the roughness and diameter of fibers. The limiting oxygen index (LOI) of the PE melt-blown materials with 10% APP and 1% SiO₂ reached 28.6%, reaching the flame-retardant level without dripping during combustion. This highlights important guidelines for developing infrared-transmitting, flame-retardant PE nonwovens for safe and sustainable applications. Full article

Flexible and wearable thermoelectric devices can convert body waste heat into electricity, showing a new direction to solve the long-lasting issue of energy supply on portable devices. However, thermoelectric fibers are prone to short circuits and failure due to sweat stains and washing practices. Therefore, it is quite necessary to solve this problem to realize the practical thermoelectric device. PDMS, with its excellent insulation and flexibility, can effectively address short-circuit issues by encapsulating the surface of thermoelectric fibers. In this work, hydrophilic nano-silica (H-SiO₂)-modified PDMS that insulates materials was prepared and coated on the surfaces of polyethyleneimine (PEI)- and hydrochloric acid (HCl)-treated dual-surface-modified thermoelectric fibers. The encapsulated fibers were then woven into spacer fabric to prepare thermoelectric textiles (TETs). After 50 water washing cycles, the fibers retained 97% of their conductivity, and the textiles continued to function normally underwater, indicating that the thermoelectric fibers are effectively protected under PDMS encapsulation. Full article

In the preparation of rubber-recycled cement mortar (RRCM), recycled fine aggregates (RFA) were used to replace 95% of natural fine aggregates (NFA) by mass, with an additional 5% of NFA replaced by rubber particles (RP). Additionally, nano-silica (NS) was incorporated to replace ordinary Portland cement (OPC) by mass at a replacement of 0%, 1%, 2%, 3%, and 4%. The study aimed to investigate the effects of NS on the mechanical properties, freeze–thaw resistance, and microstructure of RRCM, using techniques such as X-ray diffraction (XRD), thermogravimetric analysis (TG-DTG), and scanning electron microscopy (SEM) to reveal the enhancement mechanisms. The results indicated that the compressive strength and flexural strength of RRCM at 28 days decreased by 10.3% and 10.1%, respectively, compared to NCM. After adding 1–3% NS, the mechanical properties of RRCM were improved, with the enhancements increasing as the NS content increased. Specifically, RRCM3 exhibited a 7.7% and 7.6% improvement in compressive and flexural strength, respectively, compared to RRCM0. After 30 freeze–thaw cycles, the strength loss rate of RCM was 27.51%, whereas the strength loss rate of RRCM3 was reduced to 20.13%, with better overall appearance integrity. Moreover, NS promoted the hydration of cement; reduced the contents of tricalcium silicate (C₃S), and dicalcium silicate (C₂S) and calcium hydroxide (CH); and facilitated the formation of additional hydration products that filled the interfacial transition zone (ITZ). The incorporation of 3% NS was found to provide the optimal improvement in RRCM. Full article

This study systematically investigates the effects of individual and combined incorporation of graphene oxide (GO) and nano-silica sol (NS) on the macroscopic properties and microstructure of cement-based grouting materials, with emphasis on their synergistic mechanisms. A series of macroscopic tests including setting time, fluidity, bleeding rate, and mechanical strength were conducted, complemented by multi-scale microstructural characterization techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), and Fourier-transform infrared spectroscopy (FTIR). The results demonstrate that both NS and GO effectively reduce setting time and bleeding rate while enhancing mechanical strength; however, NS exhibits a more pronounced adverse effect on fluidity compared to GO. The hybrid system displays a distinct transition from synergy to antagonism: under low-dosage co-incorporation (2 wt% NS + 0.01 wt% GO), the flexural and compressive strengths increased by 13.5% and 45.5%, respectively, relative to the reference group. Microscopic analysis revealed that the synergistic interaction between the pozzolanic effect of NS and the templating effect of GO under this condition optimizes hydrate morphology and pore structure, leading to enhanced performance. Conversely, excessive dosage of either component induces agglomeration, resulting in microstructural deterioration and performance degradation. This study establishes optimal dosage ranges and combination principles for NS and GO in cement-based materials, providing a theoretical foundation for designing high-workability and high-strength cementitious composites. Full article

The dehydration of fructose and glucose to 5-hydroxymethylfurfural (HMF) in water solution was carried out in the presence of functionalized heteropolyanion-based heterogeneous catalysts. Two catalysts were prepared by immobilizing the Keggin polyoxometalate H₃PW₁₂O₄₀ (PW₁₂) onto nanoSiO₂ by the use of imidazoline and -SO₃⁻ surface species through acid–base reactions. The catalysts were characterized by N₂ adsorption–desorption isotherms, XRD, TGA, FTIR, solid-state NMR, SEM, and acidity–basicity measurements. Catalytic reactions in batch conditions were performed at 165 °C in the presence of suspended catalysts, and the yield of furfural and 5-hydroxymethylfurfural (5-HMF) was determined. The catalytic activity of the materials was tested for sugars at 1M concentration in a water solution. The valorization of sugars (fructose and glucose) was found to be more effective in the case of fructose. Furthermore, the two catalysts in which the heteropolyacid was immobilized showed activity similar to that observed for naked PW₁₂ (reaction in homogeneous phase), despite the heterogeneous nature of the process, but with the advantage of easier separation at the end of the reaction by simple filtration. The material’s substantial stability was demonstrated through three consecutive catalytic test cycles, in which the same catalyst was recovered after each experiment and washed several times with hot water. Finally, tests devoted to the valorization of sugars contained in wastewater from the brewing industry provided a poor yield in 5-HMF, indicating that the catalysts prepared here were, unfortunately, not suitable for this transformation under the conditions tested. This was because the catalysts prepared in this work showed a low capacity to transform glucose (the most present sugar in the carbohydrate fraction of this biomass) into furans. Full article

The harsh conditions of the space environment necessitate advanced materials capable of withstanding extreme temperature fluctuations and ultraviolet (UV) radiation. While epoxy-based composites are widely utilized in aerospace due to their favorable strength-to-weight ratio, they are prone to degradation, especially under prolonged high-energy UV-C exposure. This study investigated the mechanical and chemical stability of epoxy composites reinforced with nanosilica at 0, 2, 5, and 10 wt% before and after UV-C irradiation. Dynamic mechanical analysis (DMA) revealed that increased nanosilica content enhanced the storage modulus below the glass transition temperature (Tg) but reduced both Tg and the damping factor. Following UV-C exposure, all samples showed a decrease in storage modulus and Tg; however, composites with higher nanosilica content maintained better property retention. Frequency sweeps corroborated these findings, indicating improved instantaneous modulus but accelerated relaxation with increased nanosilica. Fourier-transform infrared (FTIR) spectroscopy of UV-C-exposed samples demonstrated significant oxidation and carboxylic group formation in neat epoxy, contrasting with minimal spectral changes in nanosilica-modified composites, signifying improved chemical resistance. Overall, nanosilica incorporation substantially enhances the thermomechanical and oxidative stability of epoxy composites under simulated space conditions, highlighting their potential for more durable performance in low Earth orbit applications. Full article

Edible composite coatings represent an alternative approach to reducing postharvest losses and extending the shelf life of perishable fruits. This study developed a nano-biopolymer coating by integrating pullulan (PUL), nano-silica (Nano-SiO₂), and tea polyphenols (TP) to retard deterioration in cherry tomatoes (Solanum lycopersicum var. cerasiforme). Optimized through response surface methodology (0.06% Nano-SiO₂, 0.1% TP, 1.8% PUL, 0.77% glycerol), the resulting Nano-SiO₂/PUL/TP composite film showed improved barrier properties (water vapor permeability, WVP: 0.2063 g·mm·m⁻²·h⁻¹·kPa⁻¹) and increased mechanical strength (tensile strength, TS: 2.62 MPa; elongation at break, EB: 67.67%), which may be attributed to a homogeneous microstructure stabilized via intermolecular hydrogen bonding. The composite coating exhibited significant (p < 0.05) antioxidant activity (59.04% DPPH·scavenging) compared to the PUL film (1.17%) and showed efficacy against S. aureus. When applied to cherry tomatoes stored at 4 °C for 15 days, the coating contributed to improved postharvest quality by reducing weight loss (−27.6%) and decay incidence (−32.3%), delaying firmness loss (2.40 vs. 0.54 N in uncoated group, CK), suppressing respiration rate (−38.8%), and enhancing the retention of total acidity (+9.7%), vitamin C (+49.6%), and total soluble solids (+48.6%) compared to the CK (p < 0.05). Principal component analysis supported sensory evaluation results, indicating the coating helped maintain sensory quality (scores > 6.0) and commercial value while extending shelf life from 9 to 15 days. These results suggest that the Nano-SiO₂/TP/PUL composite coating may serve as a preservative for extending the shelf-life of cherry tomatoes by effectively reducing decay and mitigating quality degradation. Full article