Mesoporous materials are defined as porous materials containing pore channels with diameters between 2 nm and 50 nm. Mesoporous Al₂O₃ materials exhibit high chemical, mechanical, and thermal stability, making them useful in fields such as catalysis, adsorption, and sensing. By selecting a specific synthesis method and varying synthesis parameters, mesoporous materials with various properties can be prepared, including different compositions and morphological characteristics, such as particle size, orientation, pore diameter, and pore periodicity. In my master's thesis, I investigated the possibilities of preparing mesoporous Al₂O₃ particles with different pore diameters. I employed two different synthesis routes: the hydrothermal method and the solvent evaporation-induced self-assembly method with a solvothermal step (SA-EISA method). For the hydrothermal method, I varied synthesis parameters, such as the use of different bases–ethanolamines (monoethanolamine, diethanolamine, and triethanolamine) and the pH value to which the reaction mixture was adjusted (pH 6.5, 7.5, or 8.5). In the SA-EISA method, different amounts of pore size-controlling additives were used in the synthesis. For both methods, I thermally treated the selected materials at 500 °C, 700 °C, 900 °C, and 1300 °C and studied the effects of thermal treatment on the material properties. Characterization was carried out using nitrogen physisorption, X-ray powder diffraction, electron microscopy, thermal analysis, and Fourier-transform infrared spectroscopy. After synthesizing the materials using the hydrothermal method, I found that aluminum oxide hydroxide was present before thermal treatment. Additionally, materials prepared with triethanolamine contained triethanolamine hydrochloride. After thermal treatment at 500 °C, mesoporous γ-Al₂O₃ material was formed, consisting of crystals with pores between them. Materials synthesized with triethanolamine exhibited the narrowest pore size distribution, and their specific surface area was higher when the pH during synthesis was adjusted to a higher value. Up to 900 °C, γ-Al₂O₃ was present in all the materials, retaining the mesoporous structure, while at 1300 °C, they transformed into non-porous α-Al₂O₃. Using the SA-EISA method, I synthesized materials with varying amounts of cyclohexane as a pore-size-controlling agent. Before thermal treatment, crystalline aluminum chloride hydrate was present in the materials. At 500 °C, a mesoporous material with intra-particle pores was formed, where pore size increased with higher amounts of cyclohexane, leading to a decrease in the specific surface area. The material remained amorphous up to 900 °C, after which it transformed into γ-Al₂O₃, and at
1250 °C, it converted into non-porous α-Al₂O₃. As the thermal treatment temperature increased, the pore diameter decreased. I concluded that all selected synthesis parameters and the choice of synthesis method influence the pore diameter. Among these, the temperature of thermal treatment had the most significant effect on the pore diameter: for the hydrothermal method, the pores increased with rising thermal treatment temperature, while for the SA-EISA method, they decreased
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