研究目的
To evaluate the influence of aging in TEOS solution on the crystallization of hydrous zirconia gel and the structure and textural properties of ZrO2 aerogel modified by SiO2, comparing with pure ZrO2 aerogel, and to discuss the kinetics and stability mechanism.
研究成果
The SiO2 layer formed during aging retards the growth of ZrO2 gel particles, diffusion, nucleation, and growth of tetragonal ZrO2, leading to improved thermal stability with higher surface area and porosity after high-temperature calcination. This enhances the material's suitability for applications requiring thermal insulation and catalytic properties.
研究不足
The study focuses on specific synthesis conditions and characterization methods; potential limitations include the use of only certain calcination temperatures and the assumption of first-order kinetics in Kissinger's method, which may not capture all complexities. Optimization could involve varying aging times or temperatures.
1：Experimental Design and Method Selection:
The study used a sol-gel process with supercritical fluid drying to synthesize ZrO2 aerogel and ZSA, followed by calcination at various temperatures. Characterization methods included TG-DSC, N2 adsorption/desorption, SEM, TEM, and XRD to analyze thermal stability and crystallization kinetics.
2：Sample Selection and Data Sources:
Samples were prepared using ZrOCl2·8H2O as precursor, with specific mole ratios of chemicals. Aging was done in ethanol or TEOS solution, and calcination was performed at 400, 600, 800, and 1000°C.
3：List of Experimental Equipment and Materials:
Equipment included SEM (Hitachi TDCLS-4800), TEM (JEOL-200CX), surface area analyzer (Quantachrome NOVA 2200e), XRD (Rigaku D/Max-2500), and DSC (Netzsch Sta 449C). Materials included analytical pure reagents like ZrOCl2·8H2O, TEOS, PO, ethanol, acetic acid, PEG 600, and formamide.
4：Experimental Procedures and Operational Workflow:
Gels were synthesized, aged in ethanol or TEOS solution for 3 days at varying temperatures, exchanged with ethanol, dried via supercritical fluid drying (heating at 1°C/min to 260°C and 7.5 MPa, held for 0.5 h, decompressed at 30 kPa/min), and calcined at specified temperatures for 0.5 h. Characterization was performed post-calcination.
5：5 MPa, held for 5 h, decompressed at 30 kPa/min), and calcined at specified temperatures for 5 h. Characterization was performed post-calcination.
Data Analysis Methods:
5. Data Analysis Methods: Data from TG-DSC, BET, BJH, SEM, TEM, and XRD were analyzed. Kissinger's method was used for kinetic analysis of DSC data to calculate activation energies.
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