Banca de QUALIFICAÇÃO: ONÉCIMA BIATRIZ DE MEDEIROS RAMALHO

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : ONÉCIMA BIATRIZ DE MEDEIROS RAMALHO
DATE: 13/05/2022
TIME: 09:00
LOCAL: Sala virtual (videoconferência)
TITLE:

Study of CdMo1-xWxO4 solid solution obtained by Microwave-assisted hydrothermal synthesis

KEY WORDS:

cadmium molybdate, cadmium tungstate, solid solutions, photoluminescence, photocatalysis

PAGES: 100
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Materiais Não-Metálicos
SPECIALTY: Cerâmicos
SUMMARY:

Materials from molybdates and tungstates families, with an ABO4-type structure, have been studied due to their photoluminescent and photocatalyst properties, among them cadmium molybdate (CdMoO4) and cadmium tungstate (CdWO4). CdMo1-xWxO4 solid solutions were synthesized using the microwave-assisted hydro/solvothermal method for x = 0; 0.5; 0.6; 0.7; 0.8; 0.9; 1.0 used deionized water as solvent and for x = 0; 0.25; 0.5; 0.75; 1, used PEG-400 as solvent. Samples’ structures were characterized by x-ray diffraction (XRD), the morphology analyzed by field emission scanning electron microscopy (SEM-FEG). The optical properties were evaluated through UV-Vis analysis, Raman spectroscopy and photoluminescence (FL) and the photocatalytic activity was evaluated through the degradation of different dyes. XRD patterns showed that samples with x = 0 and x = 1 for the hydrothermal method have scheelite and wolframite structure, respectively, and the intermediate compositions are a mixture of the two phases. For the samples obtained by the solvothermal method, there is a formation of continuous solid solution with scheelite structure until the composition x = 0.75. Raman spectroscopy showed local order-disorder changes when tungsten was added to the structure in both methods. SEM-FEG analysis showed that the hydrothermal method samples morphology is spherical and in rods and for the solvothermal method samples the morphology is irregular. The band gap energy varied between 3.19 and 3.74 eV, and this value decreased as tungsten atoms were inserted into the CdMoO4 structure, in both methods. The photoluminescent spectra of the samples have a broadband behavior, and most of the powders have emission in the orange-red region, reducing their intensity as W is inserted into the lattice and suggesting an improvement in the photocatalysis property. The photocatalytic activity evaluated against methylene blue showed that the samples have a good photocatalytic activity, above 90% for the hydrothermal method, highlighting the sample with x = 0.8, which degraded 98% of the dye, indicating a good alternative for application in photocatalysis.
Keywords: cadmium molybdate, cadmium tungstate, solid solutions, photoluminescence, photocatalysis

BANKING MEMBERS:
Presidente - 1802888 - FABIANA VILLELA DA MOTTA
Interno - 1883170 - MAURICIO ROBERTO BOMIO DELMONTE
Externo à Instituição - LUÍS PRESLEY SEREJO DOS SANTOS - UNIFESP
Externa à Instituição - RENATA CRISTINA DE LIMA - UFU