Banca de QUALIFICAÇÃO: SÉRGIO LIMA SILVA DO CARMO

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : SÉRGIO LIMA SILVA DO CARMO
DATE: 28/02/2023
TIME: 09:00
LOCAL: Auditório do Laboratório de Cimentos da UFRN
TITLE:

New hydrothermal synthesis route with pressure injection for TiO₂ nanotubes

KEY WORDS:

TiO₂, nanotubes, solvothermal synthesis, high-pressure.

PAGES: 60
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Materiais Não-Metálicos
SPECIALTY: Cerâmicos
SUMMARY:

The technological progress result in the incessant search for new materials or materials with improved characteristics compared to those already obtained. Therefore, to obtain these new materials, it is necessary to optimize the existing synthesis routes. Chemical syntheses stand out in this context with the possibility of developing more economical and efficient methods to synthesize new products, in addition to a wide margin of study. Among these syntheses, the hydrothermal synthesis can be highlighted, which is being widely explored because of the feasibility of modifying study parameters, due to its simplicity, low cost and good efficiency, in addition to being able to control the morphology and dimensions of the material produced, to create products with homogeneous chemical composition and with less agglomeration. However, this technique did not allow controling an important parameter in synthesis reactions, pressure, which is autogenous. But recent studies have shown that such an adjustment was possible with the gases injection in the production of oxide particulate materials, to allow more possibilities in controlling characteristics such as morphology and size of the resulting product. These researches with gas injection, being pioneering and recent, have not yet developed hydrothermal synthesis with the control of system pressure for the production of TiO₂ nanotubes. They are easily obtained by hydrothermal synthesis and have been widely studied for applications in electrodes for lithium-ion batteries due to their good photocatalytic properties. Thus, this work consists in the production of a new route of hydrothermal synthesis of TiO₂ nanoparticles through the injection of ultrapure argon in the reactor with the solution, starting from a spherical geometry commercial powder, aiming the synthesis of nanotubes, with the objective of use them in battery electrodes. TiO₂ nanotubes were synthesized through the hydrothermal treatment of precursor solutions containing commercial TiO₂ particles, sodium hydroxide (NaOH) and water. The solutions were heated to 150°C and maintained for different residence times (3-18h) and pressures (autogenous and 65 bar). The obtained powders were washed with aqueous HCl solution, dried and characterized by XRD, SEM and BET. XRD analyzes indicated that the rutile phase is the majority, with the presence of residual anatase phase. SEM images showed particle agglomeration probably resulting from the high surface area. Such agglomerates showed an internal porous structure formed by interconnected channels, which have walls made up of thin nanotubes and nanofibers, sometimes translucent, with length ranging from 100 to 200 nm to 500 to 700 nm, with growth proportional to time of residence in the reactor and the applied pressure. An outer layer was formed by nanotubes covering the porous structure.

COMMITTEE MEMBERS:
Presidente - 1298936 - ANTONIO EDUARDO MARTINELLI
Interna - 1308577 - SIBELE BERENICE CASTELLA PERGHER
Externo à Instituição - ARMANDO MONTE MENDES - UFRN