masterThesis
Síntese e caracterização de molibdato de cério pelo método hidrotérmico assistido por micro-ondas: aplicação como sensor de gás ozônio
Fecha
2021-08-27Registro en:
OLIVEIRA, Fernanda Karine Fonseca de. Síntese e caracterização de molibdato de cério pelo método hidrotérmico assistido por micro-ondas: aplicação como sensor de gás ozônio. 2021. 71f. Dissertação (Mestrado em Ciência e Engenharia de Materiais) - Centro de Ciências Exatas e da Terra, Universidade Federal do Rio Grande do Norte, Natal, 2021.
Autor
Oliveira, Fernanda Karine Fonseca de
Resumen
Materials based on metallic molybdates have attracted many studies, due to their
properties leading to numerous technological applications in several areas, such as:
photoluminescence, photocatalysis and resistive gas sensors. In this work, we
performed the synthesis of cerium molybdate (Ce2(MoO4)3) nanocrystals via the coprecipitation method followed by the microwave-assisted hydrothermal (MAH)
treatment at 150 °C during different times (15, 30, and 60 min). This study showed that
the effect of the MAH treatment time influenced the microstructural, optical and ozone
gas-sensing properties. X-ray diffraction (XRD) and Raman spectroscopy
measurements revealed that the samples presented a single-crystalline phase with
scheelite-type tetragonal structure. Field emission gun scanning electron microscopy
(FEG-SEM) images showed that MAH conditions favored changes in the morphology
of the Ce2(MoO4)3 nanocrystals. In addition, transmission electron microscopy (MET)
revealed that the interplanar distances corresponding to the main peak found in the
XRD diffractogram, and the SAED confirmed that the samples are polycrystalline with
concentric rings. The photoluminescence (PL) measurements indicated a significant
increase in the PL emission with the time MAH, suggesting an increase in the intrinsic
defects formed during the synthesis. The gas-sensing performance of cerium
molybdate nanocrystals in relation to ozone sub-ppm levels was also investigated. The
experiments revealed complete recovery and good repeatability as well as a good
sensor response, which was improved in the sample synthesized in the longer time of
the HMO.