Journal of Sol-Gel Science and Technology最新文献

We report the synthesis of iron oxide nanoparticles using solution combustion synthesis, focusing on the controlled manipulation of material characteristics, such as particle size, phase composition, and magnetic properties, by applying external inert gas pressure. It was shown that variation of nitrogen gas pressure in the reactor in the range 0.1 to 1.1 MPa changed the time-temperature history of the process and resulted in the gradual change of phase composition of the fabricated materials along the FeO → FeO∙Fe₂O₃ → Fe₂O₃ route. The particle size varied in the 50–400 nm range, with a maximum for powder synthesized at a pressure of 0.25 MPa. For magnetic fluid hyperthermia, the critical parameter is specific loss power. It was demonstrated that this parameter can be optimized by gas pressure variation. The maximum specific loss power measured under conditions suitable for magnetic hyperthermia (magnetic field 33.5 mT and frequency 259.6 kHz) appears to be 174 W/g. The proposed innovative approach is an effective tool for controlling the synthesis of various nanoparticles with desired properties.

The design and synthesis of porous carbons with unique structures and diverse functionalities as CO₂ adsorbents constitute a challenging and intriguing research topic. In this study, the synthesis of hollow micro-mesoporous nitrogen-doped carbon nanoparticles (NPCS) and its adsorption of CO₂ were investigated. Highly porous nitrogen-doped carbon nanoparticles were successfully synthesized by using economically available resorcinol and formaldehyde as carbon precursors, with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (KH-792) as a soft template and silica sol as a hard template. The hollow nitrogen-doped carbon nanoparticles exhibit an evident microporous-mesoporous structure and have two different scales of mesopores with 9 nm and 12 nm, respectively. The effects of various synthetic parameters on the formation of hollow nitrogen-doped carbon nanoparticles were analyzed. The hollow nitrogen-doped carbon nanoparticles exhibited specific surface area of 1090 to 1716 m²/g and nitrogen content of 2.83 to 5.28%. At 273 K and 1 bar, the experimental results demonstrated the positive effects of the enriched pore structure and nitrogen doping on CO₂ adsorption. The optimum adsorption capacity of activated NPCS (ANPCS) was 5.11 mmol/g with excellent CO₂/N₂ selectivity value of 20.44 at 273 K and 1 bar. The initial heat of adsorption value for ANPCS was 30.90 KJ/mol. Additionally, the hollow nitrogen-doped carbon nanoparticles retained 99.2% of the initial adsorbed amount after 5 cycles of adsorption. The excellent adsorption performance of the material can be ascribed not only to its extensive specific surface area and enriched nitrogen but also to its mesoporous and hollow structure, which facilitates rapid CO₂ transport.

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SrTiO₃ based lead-free ceramics has enormous potential for dielectric capacitors. This work focuses on the fabrication of small size Sr_1-xCa_xTiO₃ (SCT) ceramic capacitors. Initially, the ceramics with a high doping concentration of 0.36 ≤ x ≤ 0.40 were prepared using the sol-gel method and characterized for their structural, morphological (grain), and dielectric properties. An increase in calcium doping concentration revealed a notable decline in the dielectric dissipation factor. Further, small size ceramic capacitors with ≈ 1mm² dimensions were micro-machined in order to replicate the size of high-frequency commercial capacitors and to emphasize the real potential of this class of ceramics for dielectric capacitors. The dielectric properties, measured from 100 Hz to 1 GHz, such as permittivity (ε′), loss tangent (tgδ), and quality coefficient (Q) revealed that these materials could have a great interest in the development of monolithic ceramic capacitors dedicated to a very large frequency range from 100 Hz to 1 GHz applications.

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