Papers by Keyword: Nanometric Powders

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Authors: Elíria Maria Jesus Agnolon Pallone, V. Trombini, Walter José Botta Filho, Roberto Tomasi
Authors: V. Trombini, Elíria Maria Jesus Agnolon Pallone, F.C. Mello, Walter José Botta Filho, Roberto Tomasi
Authors: K.L. Silva, L.O. Bernardi, Makoto Yokoyama, Vania Trombini, Carlos Alberto Alves Cairo, Elíria Maria Jesus Agnolon Pallone
Abstract: The addition of nanometric particles of a second phase into ceramics matrix is one of the most recent alternatives in the development of materials with high mechanical properties and wear resistance. These nanostructured materials can be defined as systems that have at least one microstructural characteristic of nanometric dimensions (less 100nm). In this work aluminadiamond nanocomposites were produced using diamond nanometric powders obtained by high energy milling. Diamond powder was produced in the SPEX shaker/mill during 6h, with a ball-tomass ratio of 4:1. The crystallite size was 30nm. After the elimination of the Fe deriving of the contamination during the milling, and desaglomeration, this nanometric powder was added in the alumina matrix in the ratio of 5wt%. The powder densification was performed by hot pressing sintering. The obtained nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and microhardness, and they have promising characteristics regarding abrasion and wear resistance.
Authors: F.R. Passador, S.C. Maestrelli, Elíria Maria Jesus Agnolon Pallone, R.F. Esposto, Roberto Tomasi
Abstract: One possible route for the production of nanometric powders is the reactive high-energy milling. For a variety of systems of highly exothermic reactions, the milling can lead to self-sustaining reactions, with the reaction being observed after an induction or ignition time, which produces a temperature increase in the reactants. In this work, WC powder was obtained by reactive high energy-milling, performed in a SPEX 8000 shaker/mill. During milling the highly exothermic displacement reaction of reduction of the WO3 by Mg was performed in presence of carbon to produce WC and MgO. The material to ball mass ratio was fixed in 4:1 and the ignition time of the reaction was determined. In order to characterize the transformations from reactant powders to reaction products, the milling was stopped at given times before, immediately after and after the reaction; the powders obtained were characterized by X-ray diffraction, scanning electron microscopy and specific surface area. Depending on the amount of carbon, W and the W2C were also observed as reaction products. The complete formation of WC was achieved with addition of an excess of carbon.
Authors: Wenming Zeng, Adriano A. Rabelo, Roberto Tomasi
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