Banca de QUALIFICAÇÃO: MARIA VERONILDA MACEDO SOUTO

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE : MARIA VERONILDA MACEDO SOUTO
DATA : 14/11/2017
HORA: 08:00
LOCAL: A definir
TÍTULO:

Study of doping methods to obtain niobium oxide and niobium carbide with copper and its application in sintered composites (Cu-NbC)

PALAVRAS-CHAVES:

Carbide of niobium, Doping, Post-composites, copper, Synthesis

PÁGINAS: 138
GRANDE ÁREA: Engenharias
ÁREA: Engenharia de Materiais e Metalúrgica
RESUMO:

In this work the doping method was carried out via humid and solid path to obtain niobium oxides and niobium carbides with copper (5% e 10% Cu mol/mol), from the hydrated ammonium trioxalate oxyniobate precursor, as well as an evaluation of the properties of copper-doped niobium (Cu-NbC) sintered carbide composite via SPS (Spark Plasma Sintering). Niobium oxide and copper (CuNb2O6) was obtained by solid-solid reaction at 660 ° C and duration of 120min. The niobium carbide was synthesized at low temperature (980ºC) and in short reaction time (60min) in a gas atmosphere of methane (CH4) and hydrogen (H2). For the sintering of the Cu-NbC composite, the following parameters were adopted: temperature 1200 ° C, compression pressure 30Mpa, reaction time 10min. The powders were characterized by X-ray diffraction, scanning electron microscopy, X-ray fluorescence (FRX), particle size analysis and nitrogen adsorption by the BET technique, as well as crystallite size measurements. The crystallite size was calculated by the Scherrer method using X-ray diffraction data. The reaction powders were obtained with nanometric particle sizes, ranging from ~ 20nm to 28nm, and in the desired proportions with the desired purity. The surface area ranged from ~ 38.0 m² / g to 48.0 m² / g. The moforlogy for both presents agglomerated particles of varied sizes and forms, prevailing the spherical format. The lowest composite deviations were obtained by the solid method, but by wet method the properties were improved, smaller sizes and particles and larger surface areas. The sintered composite was evaluated by XRD, Vickers hardness, density and crystallite size evaluation. Measurements of Vickers hardness, density by Archimedes, SEM and EDS with mapping were also performed, which identified good dispersion and homogenization of the phases. The best Cu-NbC results were obtained for the sintered samples via wet and 5% Cu, with Vickers hardness (84.1 HV) and density (79.3%).

MEMBROS DA BANCA:
Presidente - 349801 - CARLSON PEREIRA DE SOUZA
Interno - 345842 - UILAME UMBELINO GOMES
Externo ao Programa - 2929066 - ANDRE LUIS LOPES MORIYAMA
Externo à Instituição - ARIADNE DE SOUZA SILVA - UFRN
Externo à Instituição - CLEONILSON MAFRA BARBOSA - IFRN