Mechanical alloying (MA) can be highlighted among the various methods and powder processing forms, which consists of producing homogeneous materials from elementary powders. This process is of paramount importance as it has the ability to reduce the particle size of the powders and can often promote bonding between elements which have low interaction and wettability. This method is usually used in the route of powder metallurgy, and generally improves the sinterability and mechanical properties of the materials. In this context, the objective of this work was to analyze the evolution of mixtures of Al2O3-5wt%-Ni and Al2O3-5wt%-Nb powders submitted to the mechanical alloying process in a planetary ball mill for up to 40h. The morphological evolution was observed through Scanning Electron Microscopy (Field Emission Gun, SEM-FEG), energy dispersive spectrometry (EDAX) phases and particle sizes by Particulometry. It was observed that a significant micro structural change occurred in both compositions, indicating the formation of composite powders. This behavior was more intensely observed with the increase in the grinding time, obtaining composite powders with a more homogeneous and uniform structure with the time of 40 hours of MA.

The effect of heat treatment on illite in air at temperatures ranging from 750 to 1150 °C was studied using the Mössbauer effect in 57Fe. The dependence of the Mössbauer parameters and relative percentage of the radiation absorption area was measured as a function of the firing temperature. The onset of thermal structural decomposition occurred at 800 °C. With rising temperature, the formation of hematite (Fe2O3) increased at the expense of the silicate mineral.

This paper presents a study of the inherent degradations of PVC tubes due to the thermal effect and ultraviolet solar radiation. The approach relates its causes and its effect of use of the PVC tubes as elements to absorption, forming a coil, in solar collectors for water heating. It is demonstrated that such degradations can be burst through the use of an outflow and an appropriate regimen of work, as well as of a protective layer for the tubes, in this case black ink used to magnify its absorption. The results of the properties of tubes that had been exposed to the degradation effect for up to five years are presented. The viability of use of this type of collector is demonstrated through comparative analysis of tubes exposed and not exposed to the sun, concluding for the low cost, easy assembly and maintenance of the system.

Este trabalho apresenta um estudo da preparação dos pós e da sinterização de misturas de diatomita-titânia . Foram realizadas medidas de difração de raios X, ATD, ATG, assim como análises químicas e microestrutural. O processo de sinterização foi investigado em função do tempo e da temperatura de sinterização, da variação de massa, da contração linear e da energia de ativação. Os resultados mostram que a sinterização da diatomita-titânia pode ser descrita pelo mecanismo do fluxo viscoso.

This work presents powder preparation and sintering experiments of a mixture diatomite-titania. X-ray diffraction, DTA, TGA as well as chemical and microstructural analyses were made. The sintering process was investigated as a function of sintering temperature and time, mass variation, linear shrinkage and activation energy. The results show that sintering of diatomite-titania could be described by a viscous flow mechanism.