Banca de QUALIFICAÇÃO: ARMANDO MONTE MENDES

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE : ARMANDO MONTE MENDES
DATA : 03/04/2019
HORA: 08:30
LOCAL: Auditório do Laboratório de Cimentos
TÍTULO:

High-pressure solvothermal synthesis of BaTiO3

PALAVRAS-CHAVES:

solvothermal synthesis, autoclave, high pressure, perovskite, BaTiO3.

PÁGINAS: 80
GRANDE ÁREA: Engenharias
ÁREA: Engenharia de Materiais e Metalúrgica
RESUMO:

In the constant effort for the development of new materials or even in the proposal of a novel chemical route of synthesis, it is necessary to understand the influence of the process parameters on the characteristics of the obtained material for later adaptation of a new experimental procedure. This work present a new methodology for the preparation of a precursor solution, followed by the preliminary investigation of the influence of the usual parameters of the solvothermal synthesis on crystalline and morphological aspects of barium titanate (BaTiO3) nanoparticles and evaluate the influence of changing the pressure on the characteristics of this material. At first, a 316L stainless steel autoclave was built with a configuration that allows not only the temperature and time control, but also the control of pressure by ultra-pure gas injection. The precursor solutions were formed by titanium tetraisopropoxide (C12H28O4Ti) and barium nitrate (Ba(NO3)2) as sources of metallic cations, a mixture of deionized water and ethanol was used as solvent and a KOH aqueous solution was used for pH adjustment. The syntheses were then performed at temperatures ranging from 80°C to 180°C, times between 15 minutes and 24 hours, and both inherent and induced pressures of 20bar to 80bar. The synthesized materials presented the tetragonal phase stabilization and a more expressive amount of a metastable pseudo-cubic phase at room temperature. Different combinations of temperature and time effects directly on particle size and especially in the morphology, promoting the formation of small spheres and self-assembling structures of spherical and cubic structures. The samples synthesized at high pressure showed a diffraction displacement from the ones with inherent pressures and sort of dendritic shape.

MEMBROS DA BANCA:
Presidente - 1298936 - ANTONIO EDUARDO MARTINELLI
Interno - 1300987 - CARLOS ALBERTO PASKOCIMAS
Interna - 349770 - DULCE MARIA DE ARAUJO MELO