Engenharia de Materiais
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/17
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2 resultados
Resultados da Pesquisa
- Surface reactivity and electrophoretic deposition of ZrO2-MgO mechanical mixture(2007-08-05) CASTRO, R. H. R.; MARCOS, P. J. B.; SAKAMOTO, E. K.; GOUVEA, D.Electrophoretic deposition (EPD) is a precision technique useful for obtaining high quality ceramic bodies with controlled dimensions and smooth coatings. The electrophoretic deposition rate is highly dependent on the surface chemistry of the powders, especially when dealing with multi-component systems. The objective of this work is to study the surface reactivity of both ZrO 2 and MgO in ethanol suspension to provide experimental benchmarks to control EPD of a ZrO2-3 wt% MgO mechanical mixture (Z3M) in ethanol. Infrared spectroscopy (FTIR) showed that ZrO2 surface spontaneously reacts with ethanol, generating negative electrophoretic mobility of the particles (-0.07 × 10-8 V-1 s-1) measured by Electroacoustic Sonic Amplitude (ESA). MgO surface also spontaneously reacted with ethanol, but a positive electrophoretic mobility was observed in this case (0.26 × 10-8 V-1 s-1). Scanning Electron Microscopy of Z3M dried from ethanol suspension showed that MgO particles were located around the ZrO2 particles, forming composite agglomerates, probably due to the electrostatic attraction between MgO and ZrO2 particles. Homogeneous deposits could be obtained from EPD of Z3M ethanol suspensions. Mercury intrusion porosimetry showed that the ZrO 2-MgO green deposited bodies using different voltages had similar pores diameters distributions, indicating that the ZrO2-MgO agglomerates are not affected by the increasing deposition rates. © Springer Science+Business Media, LLC 2007.
- Electrophoretic deposition of ZrO2-Y2O3: A bi-component study concerning self-assemblies(2009-01-05) CASTRO, R. H. R.; KODAMA, P. K.; GOUVEA, D.; MUCCILLO, R.There are many industrial advantages of using mechanical multi-oxides mixtures to obtain ceramic parts by electrophoretic deposition (EPD). This is mainly because one could avoid complex chemical synthesis routes to achieve a desirable composition. However, EPD of these suspensions is not an easy task as well since many different surfaces are present, leading to unexpected suspension behavior. The particles surface potentials and interactions can, however, be predicted by an extension of the DLVO theory. Using this theory, one can control the suspension properties and particles distribution. The objective of this work was to apply the colloidal chemistry theories to promote the formation of a heterocoagulation between ZrO2 and Y2O3 particles in ethanol suspension to achieve a suitable condition for EPD. After identifying a condition where those particles had opposite surface charges and adequate relative sizes, heterocoagulation was observed at operational pH 7.5, generating an organized agglomerate with ZrO2 particles surrounding Y2O3, with a net zeta potential of -16.6 mV. Since the agglomerates were stable, EPD could be carried out and homogeneous deposits were obtained. The deposited bodies were sintered at 1600 °C for 4 h and partially stabilized ZrO2 could be obtained without traces of Y 2O3 second phases. © 2009 Springer Science+Business Media, LLC.