This thesis focuses on the study and development of new materials based on the binary silicon-oxygen (Si-O) system. The main objective is the production of materials with improved structural and morphological properties, using wet chemistry techniques. For the synthesis of these materials, precursor compounds such as tetraethyl orthosilicate (TEOS) were used as the silicon source, cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS) and polyethylene glycol 4000 (PEG4000) for morphology control. In addition, solutions of NaOH and 25% NH₄OH were used to adjust the pH and enhance the hydrolysis and condensation processes. The significance of this research lies in the ability to produce nanostructured materials with controlled characteristics, such as porous structure and crystallinity. Through the appropriate design of synthesis conditions, control over the structure and morphology of the produced materials at the nanoscale was achieved. This is crucial for understanding the mechanisms governing the formation of such materials, as it paves the way for the development of innovative materials with enhanced physicochemical properties. Advanced techniques were used for the characterization of the samples, including Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM). These techniques confirmed the formation of Si-O bonds, revealed the crystalline or amorphous nature of the materials, and provided details on their morphology at the micro- and nanoscale. The produced Si-O materials, due to their porous structure and chemical stability, have multiple applications. They can be used as catalytic supports, in gas sensors, in energy storage materials (such as batteries and supercapacitors), in filtration membranes, as well as in the biomedical field for applications such as controlled drug release. This thesis contributes to the deepening of knowledge regarding the synthesis and properties of these materials, creating the conditions for future research and industrial applications. In simple terms, this thesis focuses on the creation and study of silicon- oxygen materials with controlled properties, which can be used in a wide range of technological and scientific applications, contributing to the advancement of materials science.

Keywords: SiO2, TEOS, CTAB, SDS, PEG-4000, XRD, FTIR, SEM

This study focuses on the synthesis of zirconia (ZrO2)-based ceramics through liquid- phase chemistry methods, particularly utilizing the hydrothermal approach. ZrOCl₂·8H₂O was used as the precursor compound, and various organic surfactants with differing chemical affinity were incorporated into each synthetic approach. Specifically, a cationic surfactant (CTAB, with a positive charge), an anionic surfactant (SDS, with a negative charge), and a non-ionic surfactant (PEG-4000, a neutral polymer) were employed. The process included dissolving the initial materials in ultrapure water, mixing them with a magnetic stirrer, regulating the pH by incorporating sodium hydroxide (NaOH) or ammonia hydroxide (NH4OH), and then conducting a hydrothermal treatment in a Teflon-lined reactor at 100 oC for four days. The final product was passed through paper for filtration, dried at 100 °C, and thermally processed at 600 °C to achieve stabilization. The surfactants (CTAB, SDS, and PEG- 4000) were examined using Fourier-Transform Infrared spectroscopy (FT-IR) to identify the functional groups. All synthesized samples were characterized through X- ray diffraction (XRD) to ascertain the crystalline phases and structure. Furthermore, Scanning Electron Microscopy (SEM) along with EDS analysis was employed to examine the morphology and elemental composition of the isolated materials.

Keywords: zirconia, hydrothermal synthesis, Scherrer equation, XRD

This undergraduate thesis focuses on the synthesis of nanostructured materials based on aluminum oxide (Al₂O₃) via a hydrothermal method. This method is using different surfactants; namely, cetyltrimethylammonium bromide (CTAB – cationic surfactant), sodium dodecyl sulfate (SDS – anionic surfactant) and polyethylene glycol 4000 (PEG4000 – nonionic surfactant) as well as inorganic bases (NaOH, NH₄OH). The aim was to investigate how these parameters can influence the phase composition, morphology, and elemental purity of the isolated materials. The samples were characterized using techniques such as XRD, SEM, and EDS. The results revealed that the combinations involving CTAB or SDS with NaOH promoted the formation of crystalline phases, while those with only NH₄OH or PEG4000/NH4OH resulted in amorphous or nanocrystalline structures. These findings suggest that both pH and the type of surfactant play a crucial role in phase development of Al-O based materials. The study sets the foundation for future research towards optimizing synthesis conditions to obtain alumina or Al-O based new materials and exploring potential applications in adsorption and catalysis among others.

Keywords: Al₂O₃, nanomaterials, surfactants, hydrothermal method, pH.