Sinterização reativa do óxido de alumínio processado por manufatura aditiva

Abstract

The additive manufacturing, especially the binder jetting principle, is capable of producing ceramic parts of complex geometries with low drawability, which is difficult to obtain through other forms of processing. The parts obtained by binder jetting requires post-processing steps, such as sintering, which can cause geometric and dimensional deviations in the parts due to the shrinkage. The reaction bonding method was specifically developed to reduce shrinkage in ceramic processing. Therefore, the objective of this work was to develop a powder, mainly composed of aluminum and alumina, capable of being processed by the binder jetting principle and post-processed by the reaction bonding technique. For this, an aluminum powder was produced and coated with 0.5% in mass (m.) stearic acid as well an alumina powder, coated with 1.5% m. dextrin which were mixed in percentages of 25%, 30%, 35%, 40% and 50% by volume of aluminum (Al) relative to alumina (Al2O3). A binder liquid composed of 23% isopropyl alcohol solubilized in deionized water was also produced. The specimens obtained were sintered at 1200 ºC in an oxidative atmosphere. The results obtained demonstrated that the joint use of the techniques is advantageous because the parts obtained were whole and totally ceramic for all formulations. The increase of the percentage of Al in relation to Al2O3 generates bending strength gain, around 20 % comparing the 25 Al and 50 Al formulations, however did not influence apparent porosity or bulk density which were on average 64% and 1.35 g/cm3 respectively. There were obtained results of shrinkage near zero, the formulation 30 Al presented the lowest shrinkage, of -0.31 ± 0.01% in volume. Besides that, a piece of complex geometry was generated with satisfactory results.