Banca de QUALIFICAÇÃO: FERNANDA MONTEIRO FREITAS

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
DISCENTE : FERNANDA MONTEIRO FREITAS
DATA : 21/01/2019
HORA: 14:00
LOCAL: Setor 4 sala F2
TÍTULO:

Study of niobium oxides consolidation by centrifugal casting method

PALAVRAS-CHAVES:

Consolidation, niobium pentoxide, ceramic, centrifugal casting

PÁGINAS: 90
GRANDE ÁREA: Engenharias
ÁREA: Engenharia Química
RESUMO:

Brazil holds more than 90% of the world's niobium reserves and is the largest producer and exporter of this material, such as ferro-niobium alloy, niobium oxide and other products. Nevertheless, there is a need to expand the use of niobium in the country in order to make better use of it economically. The Brazilian Ministry of Mines and Energy encourages the development of technological applications to add value to niobium and its derivatives through research. The remarkable chemical and physical properties of Nb₂O₅ make this material promising for application as adsorbent, gas sensor, solar cells and electrochromic components. Some recent research studies have verified the possibility of several catalytic applications of niobium oxides, either as active phase or as support. Considering the above arguments, a study of the consolidation of Nb₂O₅ suspensions by the centrifugal casting method was carried. The purpose of the present work was to investigate the efficiency of this simple and low-cost method in the preparation of ceramic supports. Initially, the slip casting method using gypsum molds was tried, but the methodology using centrifugal force proved to be much more effective. The slurries were prepared by mixing Nb₂O₅ or Nb₂O₅.xH₂O, PVA, agar, deionized water and boric acid dissolved in glycerin. Rotational speed was set at 10,000 rpm during various deposition times (5, 10, 20 and 30 min). Heat treatment was performed at various sintering temperatures varying from 1100 °C to 1400 °C. The dwell time was 4 h. Both green and sintered bodies were characterized by scanning electron microscopy with field emission (SEM-FEG), X-ray diffraction (XRD). The density of green and sintered bodies was determined by the Archimedes method. The results showed significant influence of the sintering temperature on the contraction of the pieces, resulting in an expressive increase of the sintered density with the increase of temperature. The centrifugation time of 20 min was considered more adequate as it resulted in a green density higher than that obtained with 30 min. The packing was also evaluated through the micrographs, which evidence internal and external surfaces with good qualities compared to other ceramics in the literature. Finally, it is concluded that the methodology studied has the potential to produce substrates in specific shapes, obtaining Nb₂O₅ ceramics that reached 90.9% of theoretical density after sintering at 1400 °C for 4 h.

MEMBROS DA BANCA:
Interno - 2929066 - ANDRE LUIS LOPES MORIYAMA
Interno - 349801 - CARLSON PEREIRA DE SOUZA
Externo à Instituição - YARA FELICIANO GOMES - UFRN