Banca de DEFESA: MICHELLE QUEIROZ DA SILVA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : MICHELLE QUEIROZ DA SILVA
DATE: 30/09/2021
TIME: 08:45
LOCAL: Plataforma Google Meet
TITLE:

Coprecipitação; moagem de alta energia; ilmenita; titanohematita; vidros de spin.

KEY WORDS:

Co-precipitation; high-energy grinding; ilmenite; titanohematites, spin glass.

PAGES: 136
BIG AREA: Ciências Exatas e da Terra
AREA: Física
SUMMARY:

Iron oxides and titanium oxides are of great scientific importance due to their magnetic, electrical, morphological, and physical-chemical properties, all of which enable various applications such as catalytic processes, semiconductors, spintronics, among others. Among the mixed binary oxides, systems of the type Fe_2-yTiO₃, a series of solid solutions with compositions between hematite (α-Fe₂O₃) and Ilmenite (FeTiO₃), have attracted the interest of theoretical and experimental areas due to their magnetic characteristics (antiferromagnetic with weak ferromagnetism). In this work, we synthesized compounds of the type xTiO₂-(1-x) Fe₃O₄ by means of high-energy ball milling, with x = 0.2; 0.4; 0.6; 0.8, of which we selected the concentration x = 0.2 for a more detailed analysis. For the synthesis of the composites, we used the precursor powders TiO₂ (anatase) and Fe₃O₄ (synthesized here by means of co-precipitation), and both were stoichiometrically mixed and milled in a ball mill for 24 hours. Subsequently, we submitted  he resulting samples to heat treatment at temperatures of  700°C, 900°C and 1100°C for 3 h. After that, the composites were characterized through X-ray diffraction, vibrant sample magnetometry, and Mössbauer spectroscopy. We used the Physical Properties Measurements System – PPMS to obtain ZFC/FC curves, magnetic susceptibility, and magnetization by different treatment temperatures. For just milled samples, the X-ray diffraction analysis did not show the formation of new crystalline phases. For the milled sample submitted to heat treatment, the presence of ilmenite (FeTiO₃) and hematite (α-Fe₂O₃) was observed, with the former presenting phase concentration of 100% at the temperature of 1100°C. Magnetic analysis and Mössbauer spectroscopy revealed the presence of Fe²⁺ and Fe³⁺ ions. The combined system FeTiO₃ - α-Fe₂O₃ is characterized as titanohematites. The sample calcined at a temperature of 700°C also showed behavior compatible with the dynamics of spin glasses. The results found suggest to the obtainment of high-quality FeTiO₃-αFe₂O₃ and FeTiO₃ composites from syntheses and accessible thermal treatments with several applications in the field of Condensed Matter Physics.

BANKING MEMBERS:
Interno - 1060742 - EDIMILSON FÉLIX DA SILVA
Presidente - 1508681 - FELIPE BOHN
Externo à Instituição - JOÃO MARIA SOARES - UERN
Interno - 050.025.724-80 - RODOLFO BEZERRA DA SILVA - UERN
Externo à Instituição - SERGIO ANDRÉ FONTES AZEVEDO - UFPB
Interna - 060.699.624-94 - SUZANA ARAÚJO BARBOSA - UFRN
Interna - 1675199 - SUZANA NOBREGA DE MEDEIROS