The present work is focused on ferrous powder metallurgy and presents some results of a development of a suitable masteralloy for use as an additive to iron powder for the production of sintered steels. The masteralloy was produced by melting a powder mixture containing approximately Fe + 20% Ni + 20% Mn + 20% Si + 1% C (wt%), in order to obtain a cast billet that was converted into fine powder by crushing and milling. It was observed presence of SiC in the masteralloy after melting that is undesirable in the alloy. Si element should be introduced by using ferrosilicon. Sintered alloys with distinct contents of alloying elements were prepared by mixing the masteralloy powder to plain iron powder. Samples were produced by die compaction of the powder mixtures and sintering at 1200 °C in a differential dilatometer in order to record their linear dimensional behaviour during heating up and isothermal sintering, aiming at studying the sinterability of the compacts. Microstructure development during sintering was studied by SEM, XRD and microprobe analyses.
In the development of dry self-lubricating composites, not only solid lubricant particle size and distribution are important, but also the correct selection of the solid lubricant characteristics, which should be stable, i.e. not reactive, during the whole processing. In this work, Fe+9 vol% h-BN composites were produced by uniaxial cold compaction and sintering, for which a reaction between h-BN and iron was detected after sintering at 1,150°C. The reaction phase was characterized by optical and scanning electron microscopy and identified by X-ray diffraction and energy-dispersive X-ray spectroscopy. The newly formed phase had high hardness when compared with the iron matrix. The resulting composites presented a high friction coefficient and high wear.
Sintered iron-based self-lubricant composites in which graphite reservoirs are generated by the dissociation of silicon carbide (SiC) particles feature low friction coefficients and scuffing resistance combined with high mechanical stress. This work evaluated the influence of the sintering temperature and the SiC polytype on the graphite reservoirs morphology, structure, and friction behaviour. The reservoirs were studied by field emission gun-scanning electron microscopy (FEG-SEM), micro-Raman spectroscopy, and transmission electron microscopy (TEM). The friction behaviour was evaluated by cylinder on plane tests (friction coefficient and scuffing resistance). The results showed that the SiC polytype and the sintering temperature modified the graphite structures. The SiC dissociation promoted the formation of different nano graphites, presenting different turbostratic 2D and 3D arrays. The results showed that the presence of the turbostratic graphite was beneficial to the friction behaviour of these composites, which offered better tribological performance than the composite with 3D graphite.
RESUMOO etileno acetato de vinila (EVA) é um polímero utilizado na confecção de materiais escolares, esportivos e no setor calçadista. Este gera resíduos, logo é necessário a sua reutilização. Visando isso, o trabalho tem como objetivo estudar placas produzidas a partir de EVA/cimento como isolante acústico e desta forma dar um destino a este material. Neste sentido a melhor mistura EVA/cimento foi estudada. Com a placa produzida foram investigadas suas características, para isto foram realizados os ensaios de absorção de água, acústica, e inlamabilidade e análise microscópica. Os resultados mostraram que a placa apresenta uma redução acústica mais eiciente nas frequências entre 800 e 1000Hz quando comparada a uma parede de concreto. Desta forma o material mostra-se viável para o isolamento acústico possibilitando assim um novo destino produtivo para o resíduo de EVA.
ABSTRACTEthylene vinyl acetate (EVA) is a polymer used in the manufacture of school supplies, sports and footwear. The production process generates substantial amounts of residues, which should be reused. The aim of this study was to examine if plates produced from a mixture of EVA and cement can be used for acoustic insulation, thus giving a proper destination to the residues. For that purpose, the best mixture of EVA and cement was examined. The characteristics of the manufactured plates were analyzed, and water absorption, acoustic, lammability, and microscopic tests were carried out. The results showed that the acoustic reduction of the plates was more eicient in the frequencies between 800 and 1000Hz as compared to concrete walls. This inding allows to conclude that EVA plates can be used for acoustic insulation, thus giving a proper destination to the residues.
Direitos para esta edição cedidos à Atena Editora pelos autores. Open access publication by Atena Editora Todo o conteúdo deste livro está licenciado sob uma Licença de Atribuição Creative Commons. Atribuição-Não-Comercial-NãoDerivativos 4.0 Internacional (CC BY-NC-ND 4.0).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.