Banca de DEFESA: LUIS MATHEUS FERNANDES DE MORAIS
Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.STUDENT : LUIS MATHEUS FERNANDES DE MORAIS
DATE: 12/04/2023
TIME: 07:00
LOCAL: https://meet.google.com/pqa-tugq-kac
TITLE:
Effect of the technique of preparation of ammonium heptamolybdate and copper nitrate powders on the densification and properties of Mo-Cu composites
KEY WORDS:
High energy milling, coprecipitation, hydrogen reduction, sintering, powder metallurgy.
PAGES: 69
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Metalurgia de Transformação
SPECIALTY: Metalurgia de Pó
SUMMARY:
Mo-Cu composite is used in electronic packaging devices, electrical contacts and heat skins. The union of the high electrical and termal conductivity properties of copper with the wear resistance of molbdenum, arouses strong interest in the electrical and electronics industry. The densification of these Mo-Cu composites via sintering is hampered due to the mutual insolubility of Mo and Cu and the low wettability of Cu to Mo. However, powder metallugy is a viable route to manufacture this composite. In this work, the influence of mechanical mixing (MM) and high energy milling (HEM) techniques, as well as the Chemical method of coprecipitation of heptamolybdate (AHM) and copper nitrate (CuN) powders on densification, microstructure and properties of Mo-20%wt.Cu and Mo-25%wt.Cu powder compacts were investigated. AHMA-CuN powders with 10.8 and 13.9 % by masso f CuN were prepared, respectively, by mechanical (MM and MAE) and chemical coprecipitation methods. The prepared powders were reduced in 750 °C in tubular furnace under H2 atmosphere and a flow of 316 mL/min. The composite Mo-Cu powders with 20 and 25 % by mass of Cu obtained were compacted at 250 MPa and the green compacts produced were sintered at 1.150 °C for 1 h under na atmosphere of H2. The sintered bodies of Mo-Cu powders prepared by coprecipitation and HEM reached a relative density of 96 ± 2.7%, while those prepared by MM reached Only 75 %. Said sintered compacts reached, respectively, a microhardness of 190.7 ± 15,4, 293.3 ± 13,4 and 183.2 ± 18,6 HV, as well as na electrical conductivity of respectively 34, 22 and 15 IACS. The greater homogenization and smaller size of the phases produced by the processes of preparation of Mo-Cu powders by coprecipitation and HEM are responsible for obtaining the highest values of the properties of density, microhardness and electrical conductivity of the sintered Mo-Cu compacts.
COMMITTEE MEMBERS:
Presidente - 2613355 - FRANCINE ALVES DA COSTA
Interno - 1938946 - NICOLAU APOENA CASTRO
Externo ao Programa - 345842 - UILAME UMBELINO GOMES - UFRNExterno à Instituição - OSCAR OLIMPIO DE ARAÚJO FILHO - UFPE