Production of composite Ag-NbC through vacuum sintering activate by mechanical synthesis, in situ , from Ag, Nb, and graphite powders.

Reference	Presenter	Authors (Institution)	Abstract
12-036	Uílame Umbelino Gomes	MELLO JÚNIOR, M.M.(Universidade Federal do Rio Grande do Norte); Menezes, R.A.(Universidade Federal do Rio Grande do Norte); Silva, H.F.(Universidade Federal do Rio Grande do Norte); Gomes, U.U.(Universidade Federal do Rio Grande do Norte); karimi, M.M.(Universidade Federal do Rio Grande do Norte);	One of more important applications of silver matrix composites are in electronic and electrotechnical fields. Results from their properties like high electric conductivity, sparking resistance, high thermal conductivity, high wear resistance, strength, cracking resistance and chemical stability. Reinforcement by dispersive particles improve hardness, reduces the wear effect of corrosion at temperature increased, give more adhesive wear resistance, and decrease or eliminate sparking. The objective of this work is make possible the production of Ag-NbC composite using lower temperatures of sintering and greater amount of additive. The solution was sintering activated in high vacuum by mechanical synthesis, in situ, from powders of Ag, Nb and C (graphite). The NbC was used in similar works with Cu-40%wWC composition. Now, in these work, the Cu was substituted by Ag. At start was analyzed the purity by XRF and particle size by laser equipment of each powder. After, the milled powders submitted to four distinct time was analyzed by XRD and SEM-EDS for identification of fases. The samples was prepared and compressed to 500Mpa by 5mm cylindric matrix. The range of sintering temperatures was defined experimentally by previous measurement of transition of fase in the same conditions of mixing, time rate and vacuum. Defined between 450 and 650°C for the isotherms to verify the sintering process keeping the other parameters. Later, was carry on density measurements, metallographic process and SEM-EDS followed by XRD to microstructure analysis. Finally, was required mechanical and electrical characterization through microhardness and electrical conductivity measurements of sintered products. The results show match between the patterns of XRD for solid and powders samples, good densification, well defined phases, reduction of electric conductivity and increase of microhardness, both behaviors according to the calculated values.
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