Name: ALINE FRANCO BATISTA
Publication date: 07/04/2026
Examining board:
Name |
Role |
|---|---|
| CLEOCIR JOSE DALMASCHIO | Presidente |
| MARTA ALBUQUERQUE MACHADO | Examinador Interno |
| OLIVIA MARIA BERENGUE | Examinador Externo |
Summary: Recent advances in nanotechnology have driven the development of materials with enhanced properties and specific applications, with hollow nanostructures standing out due to their high surface area and low density. Among these materials, metal oxide nanoparticles—particularly hollow alumina (AlO) spheres—exhibit high thermal stability, chemical resistance, and superior functional performance, making them promising for advanced technological applications. In this context, this work investigated the synthesis of hollow alumina particles using carbon microspheres (MCs) as templates, obtained via a hydrothermal route capable of providing efficient control over particle morphology and size. The synthesized MCs (180 °C, 6 h) showed high uniformity, an average diameter of 483 nm, and surfaces rich in oxygenated groups, favoring the anchoring of Al³ ions. Controlled coating at pH 7.5 enabled the formation of homogeneous core–shell structures mainly composed of boehmite, which was subsequently converted into -AlO after calcination at 600 °C. Thermal analysis revealed that, under an oxidizing atmosphere, overlapping events occurred between 250 and 500 °C associated with dehydroxylation and combustion of the carbon core, resulting in a total mass loss of about 70%, whereas in an inert atmosphere the events occurred separately. Kinetic studies based on the isoconversional FWO, KAS, and Starink models indicated an average activation energy of approximately 130 kJ mol¹, and mechanistic modeling (z-Master Plot) showed that in the 35–50% conversion range the predominant mechanism varies with heating rate, evidencing that thermal kinetics and event overlap directly influence the final particle morphology. Functionalization of the hollow structures with polytetrahydrofuran (T650) was confirmed by FTIR, demonstrating effective surface modification. The incorporation of these particles as additives in epoxy paint matrices led to a significant improvement in thermal performance. Formulations containing 3% and 5% (w/w) MCs increased resistance to heat transfer, keeping the temperature of uncoated glass up to about 9 °C lower than systems without additives. Samples containing HALO-T650 exhibited even lower initial heating rates, showing a temperature difference of approximately 12 °C relative to the reference, indicating that functionalization enhances particle–matrix interaction and dispersion, allowing the particles to act as thermal micro-reservoirs capable of absorbing part of the incident energy.
