Banca de QUALIFICAÇÃO: GERMANO PEREIRA DOS SANTOS

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE: GERMANO PEREIRA DOS SANTOS
DATA: 31/01/2023
HORA: 14:00
LOCAL: Auditório do PPGQ - UFPI (virtual)
TÍTULO: Silver tungstate obtained via successive seed crystal growth: Structural, morphological, optical, and photocatalytic properties
PALAVRAS-CHAVES: silver tungstate, degradation, semiconductor, coprecipitation method
PÁGINAS: 23
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Físico-Química
ESPECIALIDADE: Cinética Química e Catálise
RESUMO:

Synthesis routes and parameters such as synthesis time, precursor molar ratio,
pH, and temperature are critical for generating oxides of various sizes and
morphological aspects. However, there is no information on how to prepare silver
tungstate (Ag 2 WO 4 ) crystals of different shapes and sizes under laboratory conditions
and without using sulfating agents. In this study, we attempted to fill this gap by
preparing α-Ag 2 WO 4 crystals of various sizes and morphologies using the
coprecipitation method in a 3 h interval at room temperature and without using sulfating
agents. The powder X-ray diffraction analysis results confirmed that all crystals had an
orthorhombic structure, whereas Fourier-transform infrared spectroscopy revealed the
degree of structural disorder in the bonds between the atoms in the materials. Scanning
electron microscopy revealed that the α-Ag 2 WO 4 crystals had different sizes
(5.37–26.83 μm) and morphologies (tetragonal prism, rod, and cypress leave-like rod),
whereas ultraviolet–visible diffuse reflectance spectroscopy analysis indicated the
optical band gap energy (2.92–3.05 eV), calculated using the method proposed by
Kubelka and Munk. Catalytic tests revealed the synthesized samples with the smallest
crystals (AW1) and a tetragonal prism morphology degraded dye more efficiently (k =
5.86 × 10 −3 min −1 ) than other samples.

MEMBROS DA BANCA:
Presidente - 756.483.183-91 - GERALDO EDUARDO DA LUZ JUNIOR - UESPI
Interno - 1998602 - EVERSON THIAGO SANTOS GERONCIO DA SILVA
Interno - 1714193 - JOSE MILTON ELIAS DE MATOS
Interno - 2406262 - ROBERTO ALVES DE SOUSA LUZ
Externo ao Programa - 840.043.633-49 - LAÉCIO SANTOS CAVALCANTE - UFPI