Preparation and Cracterization of Alu1Inur Titanate Plabra Spray Powder
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PREPARATION AND CRACTERIZATION OF ALU1INUR PLABRA SPRAY POWDER
TITANATE
L. J. SHYU, V. T. BRICE, F. M. CAMBRIA, B. M. SU, C. TIRENDI, AND J. WANDASS Akzo Chemicals Inc., 1 Livingstone Ave., Dobbs Ferry, NY. 10522 ABSTRACT Aluminum titanate ceramic powder, used in plasma spray coating as a wear resistant material, was prepared from a gel The precursor followed by high temperature calcination. chemically derived gel was made from aluminum sulfate and titanium isopropoxide in an oxalic acid aqueous system. The 1 3 soluble complex was studied by C NMR spectroscopy which showed that the mole ratio of oxalic acid bound to Al and Ti was 2:1. A coprecipitation took place when ammonium hydroxide was added. The gel was examined by solid-state NMR spectroscopy which suggested that aluminum titanium hydroxyl oxalate was present with Al in a distorted octahedral environment. EDX mapping showed that Al and Ti were evenly distributed throughout the gel particles. Thermal analysis indicated that dehydration and combustion of organic groups took place between 0 100 and 400 C. Gel which was heat treated at 1500 0 C was identified as a pure AI 2 TiO5 crystalline phase by XRD. INTRODUCTION Aluminum titanate is recognized as a valuable ceramic material in refractory and metallurgy applications. It has a low thermal expansion coefficient, high melting point and high density that make it very attractive as a wear resistant material. Commercially, physically mixed A1 2 0 3 /TiO 2 powders with various compositions are available for p asma spray wear resistant coatings. However, chemical inhomogeneity, inconsistent powder size, uncontrolled morphology and impurities may adversely affect the performance of coatings made from these powders. A chemically derived Al TiO5 powder may offer advantages for wear resistant coating appfications. Aluminum titanate is thermally unstable and decomposes to A1203 and TiO2 at 1281 0 C [1]. Conventional methods of preparing A1 2 Ti0 involve solid-state reaction of A1 2 0 3 and TiO2 powders [2]. Kladnig and Mayer prepared AI 2 TiO5 by gas-phase hydrolysis [3]. Several papers described the synthesis of aluminum titanate from hydrolysis of aluminum and titanium alkoxides followed by a heat treatment [4,5,6]. In order to have a homogeneous co-hydrolysis, proper selection of alkoxides and the reaction temperature is very critical (5]. Mani et. al. synthesized aluminum titanate from a boehmite sol and titanium butoxide via thermal decomposition of transparent gels (7). In this study, a novel method developed to produce AlTiO5 plasma spray powder through an organometallic precursor is described. The precursor was synthesized, characterized, and thermally transformed into AI 2 TiO5 .
Mat. Res. Soc. Symp. Proc. Vol. 249. 01992 Materials Research Society
116
EXPERIMENTAL All chemicals used in this work were A.C.S. reagent grade. Oxalic acid was dissolved in distilled water in a round bottom flask equipped with a mechanical stirrer. Aluminum sulfate solution was added and stirred until the solid completely dissol
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