Banca de DEFESA: RAIMISON BEZERRA DE ASSIS

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : RAIMISON BEZERRA DE ASSIS
DATA : 29/06/2017
HORA: 14:00
LOCAL: Sala de aulas do PPGCEM
TÍTULO:

SYNTHESIS OF SODIUM AND POTASSIUM NIOBATE (K1-xNaxNbO3) WITH PHOTOCATALYTIC AND PHOTOLUMINESCENT PROPERTIES

PALAVRAS-CHAVES:

Niobate KNN, Perovskita, Polymer precursors, Photocatalysis, Photoluminescence.

PÁGINAS: 164
GRANDE ÁREA: Engenharias
ÁREA: Engenharia de Materiais e Metalúrgica
RESUMO:

In recent years, photoluminescence and photocatalysis have proven to be a comprehensive field for the research and development of materials technology. The development of new materials has opened new perspectives for the production of devices with highly efficient photoluminescent and photocatalytic properties. Among the promising materials of technological interest are the semiconductors sodium and potassium niobates (KNN), which show good performance in optical and photocatalytic properties. In this work, perovskite structures of sodium and potassium niobate (K1-xNaxNbO3) for x = 0; 30; 50; 70; 100% (mol) were synthesized by the polymer precursor method and heat treated at 600°C, 700°C, 800°C and 900°C for the purpose of investigating their photocatalytic and photoluminescent properties. The samples were characterized by thermal analysis (TG/ DSC), X-ray diffraction (XRD), Raman spectroscopy, infrared absorption spectroscopy (FTIR), UV-vis optical absorption spectroscopy, scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), photoluminescence (PL) and photocatalytic tests on the degradation of methylene blue dye. The results of X-ray diffraction confirmed the formation of the orthorhombic phase of the perovskite KNN, K1-xNaxNbO3 showing long-range organization. The FTIR spectra confirmed the X - ray diffraction data by presenting a reduction of bands related to short vibrations related to the double bonds of Nb = O. SEM images revealed that the KNN niobate samples presented morphology in the form of cubes with different particle sizes, with the presence of agglomerates and partially sintered regions. The optical absorption spectra by UV-vis characterized the niobates as semiconductors, indicating an optical gap between 2.59 eV and 3.35 eV, in addition to showing that the increase of the heat treatment temperature and the sodium concentration promoted an increase of the gap band. Photoluminescence spectra indicated a decrease in FL emission intensity with increasing sodium concentration in the KNbO3 matrix, exhibiting emission at room temperature in the region of violet (433 nm) in red (642 nm). Samples of niobates KN, KNN30, KNN50, KNN70 and NN showed satisfactory degradation rates, presenting excellent results for NaNbO3 (NN) thermally treated at 600°C with 95.95% degradation of the dye. The increase of the sodium concentration improved the photocatalytic performance of the KNN system, being efficient for photocatalytic applications. The results indicate the potential of sodium and potassium niobates in photocatalysis and photoluminescence.

MEMBROS DA BANCA:
Interno - 1298936 - ANTONIO EDUARDO MARTINELLI
Presidente - 1802888 - FABIANA VILLELA DA MOTTA
Interno - 1883170 - MAURICIO ROBERTO BOMIO DELMONTE
Externo à Instituição - MAXYMME MENDES DE MELO - IFRN
Externo à Instituição - NEFTALÍ LENIN VILLARREAL CARREÑO - UFPel