Synthesis of β-Alumina-Type Compounds and their Transformation Via the TCON Process

Abstract

Fireline TCON, Inc., a ceramics company in Youngstown, Ohio, has developed a unique method for producing co-continuous ceramic/metallic composite materials. These TCON composite materials are usually produced from a reaction of silica with molten aluminum via a process known as reactive metal penetration, producing an interpenetrating phase composite of aluminum oxide and aluminum metal, where silicon is alloyed with aluminum in the metal phase. These composite materials have a variety of interesting properties, such as extremely high tolerance of heat, resistance to corrosion, and high strength. Theoretically, the TCON process can be altered in order to utilize a wide variety of metal oxides other than silica as sacrificial oxides. A class of compounds known as β-aluminas are of particular interest, as these compounds contain open channels within their crystal structure, which may facilitate the TCON reaction or produce a TCON composite with different morphology and properties than have previously been reported. Specifically, the possibility of producing a nano-scale composite is being investigated, due to the nano-scale features of the β-alumina crystalline structure itself. Several different β-alumina compounds have been prepared and transformed via the TCON process. Phases present in the product were analyzed via PXRD, and the morphology of the composite was analyzed via SEM. Several related spinel phases were prepared and transformed for comparison to results for transformed β-alumina. In addition, attempts have been made to produce novel β-alumina structures that would be beneficial as sacrificial oxides in the TCON process. Novel compounds such as SrTi₅Mg₆O₁₇ that would transform under TCON conditions would result in a number of beneficial properties in the produced composite. These benefits include the presence of aluminum-titanium alloys, which have excellent strength-to-weight ratios.