CONICET | Buscador de Institutos y Recursos Humanos

Aluminum borates (Al18B4O33 and Al4B2O9) formation from alumina and boron oxide occurs at high temperatures. These materials have refractory properties and corrosion resistance. The objective of this work is to develop materials from the Al2O3-B2O3 system; employing alumina and boric acid as starting powders, to study the critical processing variables and to describe the developed microstructure, and properties.Three formulations (13, 19.5, 26 wt. % B2O3) were studied. In order to confirm the formation of the borates the differential thermal analysis and the thermo gravimetric analysis were carried out. Afterwards uniaxially pressed disc shape specimens were fired at four temperatures above the formation temperature. Sinterability was evaluated by monitoring the textural properties by the Archimedes method, and then the degree of formation was confirmed by X-ray diffraction. Finally the developed microstructures were characterized by scanning electron microscopy, and the diametral compression behavior was evaluated. A series of materials porous (≈ 50 %) refractory materials from the Al2O3-B2O3 system were developed. The processing strategy resulted in materials with Al18B4O33 as principal crystalline phase, with needle grains with diameters between 0.2 and 1 µm and an aspect ratio over 20:1 were obtained. The developed materials gives enough information for designing porous aluminum borate ceramic materials with structural, insulating or filtering applications employing only alumina and boric acid as boron oxide source.

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