Banca de DEFESA: MARIA JOSÉ SANTOS LIMA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : MARIA JOSÉ SANTOS LIMA
DATA : 18/07/2017
HORA: 13:30
LOCAL: Sala de aulas do PPGCEM
TÍTULO:

Synthesis of Nanostructured composite powders (WC-Ni) by APT Carborreduction with Ni(NO3)2.6H2O and its Sintering in Vacuum Oven and by SPS.

PALAVRAS-CHAVES:

Tungsten Carbide, Hard Metal, Composite Powders, Nickel, Synthesis and Carborreduction.

PÁGINAS: 180
GRANDE ÁREA: Engenharias
ÁREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Materiais Não-Metálicos
ESPECIALIDADE: Cerâmicos
RESUMO:

In this work WC-Ni composite powders were synthesized by carborreduction of the hydrated ammonium paratungstate (APT) mixture with the nickel nitrate in proportions (5% p.Ni, 10% p.Ni and 15% p.Ni) a low temperature (800 ° C to 950 ° C) and small reaction time (90min to 150min) in a single synthesis process. The powders were characterized mainly by X-ray diffraction, Scanning Electron Microscopy (SEM), Dispersive Energy Spectroscopy (EDS), X-ray Fluorescence (FRX), Particle Size Analysis and (BET) and measures of magnetization, coercivity and remanence. The study of crystallite size was obtained from the X-ray diffractograms of post-composites, using the Scherrer equation. A factorial experimental design 23 with three central points was carried out to evaluate the influence of the synthesis conditions on the response variables (crystallite size). The synthesis parameters evaluated in this work were: reaction time (90min, 120min and 150min), synthesis temperature (800 ° C, 850 ° C and 900 ° C) and concentration of nickel by weight (5% p.Ni, 10 % P.Ni and 15% p.Ni). It was possible to produce nanometric WC-Ni composite powders in the desired proportions with the desired purity, with a mean crystallite size varying from 24.2 nm to 38 nm, with a surface area ranging from 24.6m²/g to 46.7 m²/g. The powders presented morphology with particles of varied sizes and shapes, quite agglomerated and also presented a good dispersion and homogenization of the phases. The specific characteristics of these nanometric materials provide their use for both the hard metal in catalytic reactions.Therefore, the composite powders obtained in this work were applied in the production of WC-Ni hard metal by solid and liquid phase sintering using conventional sintering and Spark Plasma Sintering techniques for comparison purposes. In the sintered samples the measurements of Vickers hardness and density by pycnometry were performed. We also performed XRD, SEM and EDS analyzes with mapping. The best results for the sintered WC-Ni were obtained for the sintered samples via SPS at 1350ºC, showing Vickers hardness (2322 HV) and density (97.67%) higher than the samples sintered by conventional sintering at higher temperatures.

MEMBROS DA BANCA:
Presidente - 345842 - UILAME UMBELINO GOMES
Interno - 349801 - CARLSON PEREIRA DE SOUZA
Externo ao Programa - 3432383 - FILIPE MARTEL DE MAGALHAES BORGES
Externo à Instituição - MARCELLO FILGUEIRA - UENF
Externo à Instituição - OSCAR OLIMPIO DE ARAÚJO FILHO - UFPE