EFFECT OF CALCIUM HEXAALUMINATE (CaAl12O19) FORMATION ON THE TEXTURAL AND MECHANICAL PROPERTIES OF a/b-Al2O3 HOLLOW SPHERES

Abstract

The removal of contaminants from wastewater is a health and environmental priority that requires the development of accessible technologies. A fundamental requirement in the development of adsorbent materials is to maximize the adsorption surface area without compromising their ease of handling and recovery after treatment. Ceramic materials are attractive for adsorption processes due to their chemical stability and biocompatibility. They can be molded as desired and retain their shape when heat-treated. Furthermore, by using a sacrificial template, hollow monoliths with a larger surface area can be obtained through a simple and low-cost process. Alumina is a versatile ceramic with high hardness (>12 GPa) and low fracture toughness (4-6 MPa m½ ), making it a brittle material. Reinforcing phases with high aspect ratio structures, such as fibers or platelets, are often incorporated into ceramic materials to improve crack desertion and fracture resistance. In the present investigation, hollow alumina spheres reinforced with calcium hexaaluminate (CaAl12O19) were obtained. The introduction of different calcium concentrations on the chemical and structural evolution of the present phases was evaluated based on the textural and mechanical properties of the spheres. The formation of CaAl12O19 in the hollow spheres increased their surface area from 0.77 to 2.39 m2 /g and the compressive strength from 435 to 1627 KPa, due to the expansive process of hexaaluminate formation.