Ultra high molecular weight polyethylene doped with iron through high energy mechanical alloying

Doping polymers with metallic materials can improve significantly its use. Ultra high molecular weight polyethylene is known for its high resistance to abrasion and impact, and also for its friction coefficient, which is significantly lower than that of commercial steel and most polymeric materials. Therefore, this material presents high industrial demand despite its processing difficulty due to its high viscosity. One kind of polymer processing which has been widely used recently is the high energy mechanical alloying. This method provokes significant changes in the material, such as crystalline structure transformation, amorphization, formation of metastable phases, and nanostructuring, among others. In order to investigate the influence of iron dopant in structural characteristics of polymeric matrix, ultra high molecular weight polyethylene were doped with low concentrations (between 0.1 at.% and 1 at.%) of iron using the method of high energy mechanical alloying. The samples composition was characterized by X-Ray Diffraction Mössbauer Spectroscopy. A theoretical molecular modeling was carried out to simulate the iron presence in polymeric cell, which is in good agreement with the experimental results. Therefore, there is evidence that part of the iron promotes a crossed bond between the polymeric chains. Keywords: Ultra high molecular weight polyethylene (UHMWPE), High energy mechanical alloying, Mössbauer Spectroscopy, structural properties

Caracterização de misturas de peuamm com resíduo de pneu obtidos através de moagem de alta energia / Characterization of blends of peuamm with tire residue obtained by high energy milling

Com o crescimento na frota de veículos a quantidade de pneus produzidos e descartados vem crescendo ano após ano e o descarte incorreto tem impactado o meio ambiente. Estudos vêm sendo realizados, apesar da dificuldade, afim de encontrar maneiras de reciclar e/ou reutilizar esse material, pois a estrutura molecular dos pneus possui ligações cruzadas que dificultam o seu reprocessamento. Existem algumas estratégias para a reciclagem de pneus, sendo uma das mais vantajosas o reaproveitamento dos pneus na forma de pó e, posteriormente, a incorporação deste em matrizes poliméricas. Este trabalho teve como objetivo a obtenção de um pó fino de pneu e a sua incorporação em uma matriz de polietileno de ultra alta massa molar (PEUAMM) através da moagem de alta energia. A moagem de alta energia criogênica se mostrou um método muito eficaz para a realização da quebra das partículas do pneu e obtenção destes pós finos e também para a obtenção das misturas. As amostras foram preparadas através de moagem criogênica e na temperatura ambiente e caracterizadas por microscopia eletrônica de varredura (MEV); calorimetria diferencial de varredura (DSC) e por ensaio de tração. A adição do resíduo de pneu afetou negativamente a propriedade mecânica das misturas devido a pobre dispersão observada das partículas. A moagem de alta energia criogênica provocou mudanças no formato das partículas do PEUAMM, de arredondadas para mais achatadas, melhorando a dispersão e promovendo o aumento da resistência mecânica e porcentagem de deformação, quando analisada tanto para o PEUAMM puro quanto para as misturas de PEUAMM com resíduo de pneu

Obtaining NiAl intermetallic compound using different milling devices

NiAl intermetallic compound was synthesized by mechanical alloying technique in planetary and attritor mills. The starting powders consisted of elemental mixtures of Ni and Al at Ni50Al50(at%) composition. In the planetary mill, compound formation occurred gradually during mechanical alloying, while the occurrence of a mechanically induced self-propagating reaction (MSR) can be suggested in the attritor mill. The NiAl obtained in both mill types was partially disordered with long-range order parameter not inferior to 0.66. Quantitative phase analysis using the Rietveld method was performed in as-milled samples, and this method was also employed to estimate changes in crystallite size and lattice strain of the NiAl produced during mechanical alloying. (C) 2011 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.State of Sao Paulo Research Foundation (FAPESP)State of Sao Paulo Research Foundation (FAPESP) [07/50954-0]Coordination for the Improvement of Higher Education Personnel (Capes) [123/07]Coordination for the Improvement of Higher Education Personnel (CAPES)CAPESCape

Study of Cryogenic Rolling of FCC Metals with Different Stacking Fault Energies

<div><p>Aluminum, copper and silver samples, all of them face-centered cubic (FCC) metals, were rolled at room and cryogenic temperatures until equivalent strains (ε) were between 3.23 and 4.13. The cryogenic temperature (CT) and room temperature (RT) rolled samples were evaluated by hardness tests and X-ray diffraction (XRD), which indicate influence of stacking fault energy (SFE) on process. Lower SFE metals tend to exhibit dislocation densities significantly increased and as consequence, hardness too. It was also noted that after sometime exposed to RT, the materials rolled at CT present hardness decrease.</p></div