Journal of Sol-Gel Science and Technology最新文献

Semiconducting Cu₂O have excellent optical and electronic properties and are more promising candidates for advanced electronic applications. In the current study, pure and 3.125%, 6.25%, and 12.5% Zn doped Cu₂O compositions were studied using density functional theory in the framework of wien2k-code. Experimentally, uniform and smooth thin films of these compositions were successfully synthesized through the spin coating technique. The elemental composition and morphology were studied using energy-dispersive X-ray spectroscopy and field emission scanning electron microscopy, respectively. Crystallographic analysis of thin films shows a cubic phase structure having space-group 224 Pn-3m. The total density of states confirms the overlapping of states at the Fermi level for Zn-doped compositions. The significant variations in thermoelectric parameters observed with change of temperature for pure and Zn substituted Cu₂O compositions, especially the Seebeck-coefficient values vary from 2.5 × 10⁻⁴ to 5.5 × 10⁻⁵ VK⁻¹ for these cuprous oxide compositions. The optical-parameter such as absorption and extinction coefficient curves reached maxima at the highest photon energies. The enhancement in transmittance power and reduction in the band gap energy from 2.08 eV to 1.75 eV with the substitution of Zn material enhanced the availability of these compositions for advanced applications.

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Indium tin oxide (ITO), a critical n-type semiconductor material, has widely used in the field of photoelectric material due to its significant conductivity and transparency. In addition, it also has excellent gas sensitivity. In this paper, a unique ITO, hollow spherical ITO powders were prepared by hydrothermal method using PEG-4000 & DL-aspartic acid (DLAA) and PEG-400 & ethylene diamine tetra acetic acid (EDTA) as two composite templates. The preparation conditions of the hollow spherical ITO powders with 2.2 μm diameter were obtained: the precipitator is urea, the molar ratio of DLAA and In³⁺ is 3:1, the temperature of hydrothermal reaction is 120 °C, the time of hydrothermal reaction is 10 h, the molar ratio of PEG-4000 and In³⁺ is 5:1, the temperature and time of calcination is 450 °C and 3 h respectively. Ultimately, hollow spherical ITO powders were prepared and the resulting samples were analyzed for a range of properties. The properties showed as follow: the specific surface area was 64.107 g/m², the resistivity is 164.03 Ω.cm. The formation mechanism of the hollow spherical ITO powders was discussed systematically. Significantly, unique ITO powders with hollow spherical have been obtained by template method, which has application potential in the gas sensitivity of ITO powders.

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Cement-based composites comprise a binder matrix with or without aggregates. Hydration of cement is an exothermic reaction that releases considerable quantities of heat, causes drying shrinkage. Hydrogels can help mitigate such cracking as their hydrophilic characteristics and 3D crosslinked structure enables them to absorb and directly release water into the cement matrix over time. This study aims to synthesize and analyze the effect of adding hybrid nanocomposite hydrogels with different concentrations (0, 10, and 20% w/v) of Cloisite-Na⁺ nanoclay in their fresh and hardened cement mortar states. The hydrogels were synthesized via free radical polymerization, and four cementitious mortar samples (M, M0, M10, and M20). The results demonstrated that the density of all the mortars in the fresh state was ~2.16 ± 0.01 g.cm⁻³, but a decreasing trend was observed that could attributed to the increase of air incorporation into the mortar. At 28 days, the results indicated that the hydrogel with 20% Cloisite-Na⁺ was the most efficient, causing a reduction of ~4.4% in water absorption by the mortar. For all, three curing conditions considered, all mortars demonstrated considerable shrinkage over time. However, the controlled curing indicated that M20 mortars demonstrated 31% less shrinkage compared to the control sample. The scientific relevance of incorporating hydrogels into cement mortars lies in their ability to effectively address critical issues related to shrinkage-induced cracking and deterioration. Moreover, the use of hydrogels aligns with sustainable construction practices by reducing the need for additional water and minimizing the environmental impact associated with cement materials production.

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Porosity and thermal stability are the main constraints that determine the performance of zirconia (ZrO₂) for a wide range of applications, including adsorption, catalysis, filtration, etc. Here, we have proposed the rational design of electrospun ZrO₂ nanofibers (NFs) with high surface areas and good thermal stability. Water vapor pre-treatment was used to modify the surface structure of the NFs with the removal of soft templates at a lower temperature. In addition, amorphous B₂O₃ was introduced into the ZrO₂ NFs to improve the thermal stability of the porous structure. The as-prepared NFs had high surface area of 380 m²/g and even 300 m²/g after heat treatment at 450 °C. The catalytic activity of modified ZrO₂ NFs as support materials in bromination reaction of phenol red was tested. And a high specific bromination activity of 3.02 mmol h⁻¹ g⁻¹ was obtained. This work could provide promising strategies for preparing electrospun porous oxide NFs with high surface area and good thermal stability in order to optimize performance.

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The current research reports the influence of particle size and concentration of Al₂O₃ additive on protective performance of double-layer coating of silane /multi-walled carbon nanotube (MWCNT) deposited on AZ91 magnesium alloy through sol-gel dip coating. The main objective of Al₂O₃ incorporation to the base silica is to seal different types of defects in the coating and increase the surface hardness, anti-wear, and anticorrosion properties of the coatings which can be beneficial for real-world applications of AZ91 magnesium alloy in industries such as automotive, aircraft, and aerospace. For this purpose, several coatings with different Al₂O₃ contents of various sizes (50 nm, 100 nm, 300 nm, and 1 μm) were deposited on AZ91 magnesium alloy with thicknesses of about 5–10 µm. It was found that the optimal Al₂O₃ contents depend on their particle size; such that 1.5, 2, 3, and 5 wt% of Al₂O₃ were determined as the optimal values for particle sizes of 50, 100, 300, and 1000 nm, respectively. Results revealed that incorporation of an optimal amount of Al₂O₃ into double-layer coating improved the corrosion resistance where, the polarization resistance of the coatings containing the optimal contents of Al₂O₃ with particle sizes of 50 nm, 100 nm, 300 nm, and 1 μm were 360.1, 265.3, 240.8, and 157.2 kΩ.cm², respectively. Moreover, the coating comprising 1.5 wt% Al₂O₃ with a particle size of 50 nm exhibited denser, finer, and lower porosity.

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Nano-bioactive glass 60SiO₂-36CaO-4P₂O₅ (mol.%) was synthesized by using the sol-gel method without using acid catalysts. Two sol precursors, tetraethyl orthosilicate and triethyl phosphate, were tested for hydrolysis at different temperatures and times. Experimental observation shows that the precursors tetraethyl orthosilicate, triethyl phosphate, and calcium nitrate tetrahydrate were hydrolyzed in the solvent system H₂O/C₂H₅OH (weight ratio of 1/8) at 80 °C. In a hydrothermal reactor, the resulting sol was transformed into a gel, and then the dried gel was transformed into a glass material by heating treatment. Physical-chemical methods such as TG-DSC, XRD, FTIR, BET, and SEM-TEM were used to evaluate synthesized glass. Additionally, the glass material was assessed for its bioactivity in SBF solution (Simulated Body Fluid), and biocompatibility with fibroblast cells (L-929) following the ISO10993-5 standard. Research results show that the glass 60SiO₂-36CaO-4P₂O₅ (mol.%) synthesized in this study is an amorphous material with particle size at the nanoscale, forming a mesoporous structure. The synthesized glass can be bioactive by forming an apatite mineral layer when soaked in SBF solution, and it is biocompatible with L-929 cells.

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Silica aerogel is a unique nanomaterial with three-dimensional nano-porous networks. However, the microstructures of aerogels are easily damaged at high temperatures environment, weakening the thermal insulation performance. In this work, we prepared thermally stable SiOC nanospheres and then composited them with aerogel matrix. SiOC nanospheres and aerogel matrix have excellent compatibility. SiOC nanospheres can induce the aerogel matrix forming island microstructures after drying process. The presence of the island microstructure leads to a reduce of the inter-skeleton macropore size, which declines from 4.77 μm to 2 μm. The thermal conductivity decreases from 0.0813 to 0.0646 W/ (m K). The volume shrinkage and density also show a clear downward trend. In order to investigate the impact of high-temperature to thermal insulation performance, the aerogel composites are experienced different high-temperature treatment. The results demonstrate that the island microstructure of aerogel is transformed into a spherical shape after high-temperature treatment. The particle diameter increases from 5 μm to 5.7 μm when treated in 200 °C and 400 °C. Upon 400 °C, the diameter reduces from 5.7 μm to 4.4 μm at 800 °C. The variety in the size of the aerogel skeleton particles results in a reduction in the pore diameters of the interskeleton pores from 8 to 3.8 μm. The thermal conductivity decreases from 0.0667 to 0.0466 W/ (m K) treating below 400 °C and increases to 0.0712 W/ (m K), when heat treatment temperature is 800 °C. The enhancement of thermal insulation performance is attributed to the decline of macropores content between skeletons caused by swelling of aerogel particles. The diameters of macropores between skeletons reduce, which can effectively weaken the influence of gaseous heat transfer. This work provides a reference for the preparation of aerogel composites that can maintain excellent thermal insulation properties in high-temperature environment.

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