Banca de DEFESA: ARMANDO MONTE MENDES

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : ARMANDO MONTE MENDES
DATA : 02/05/2019
HORA: 14:00
LOCAL: Auditório do CCET
TÍTULO:

SOLVOTHERMAL SYNTHESIS OF BaTiO3: EFFECT OF PRESSURE ON THE MORPHOLOGY AND PARTICLE SIZE

PALAVRAS-CHAVES:

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

PÁGINAS: 100
GRANDE ÁREA: Engenharias
ÁREA: Engenharia de Materiais e Metalúrgica
RESUMO:

In the constant effort for the development of materials free from agglomeration and with controlled morphology, it is necessary to understand the influence of the process parameters on the characteristics of the obtained material for later proposal of new experimental procedures. This work present a new methodology for the solvothermal synthesis of barium titanate (BaTiO3), followed by the investigation of the effect of parameters such as temperature, time and especially pressure on the morphological characteristics of the 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 tetra-isopropoxide (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 potassium hydroxide (KOH) was used as mineralizer and pH adjustment agent. 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 20 bar to 80 bar. The synthesized materials presented the tetragonal phase stabilization and a more expressive amount of a metastable pseudo-cubic, free from contaminations such as BaCO3. The different combinations of process parameters allowed the observation of a morphological evolution of particles and also the nucleation and crystal growth mechanisms, as well as the Ostwald ripening phenomena. Under conditions of inherent pressure, particles showed from amorphous rough spheres, trough agglomerates of nanocubes (mesocrystals) and irregular particles with anisotropic growth. The high pressure synthesis produced dendritic and flower-like morphologies with high surface area even without any surfactant agent. All samples were free from agglomerations.

MEMBROS DA BANCA:
Presidente - 1298936 - ANTONIO EDUARDO MARTINELLI
Externo à Instituição - DANIEL ARAÚJO DE MACEDO - UFPB
Interna - 349770 - DULCE MARIA DE ARAUJO MELO
Externo à Instituição - MARCOS TADEU D'AZEREDO ORLANDO - UFES
Interna - 1308577 - SIBELE BERENICE CASTELLA PERGHER