Papers by Keyword: Aluminium Titanate

Abstract: Mullite-aluminium titanate-corundum composite was prepared at 1300°C with refractory clay, aluminium titanate and high alumina grog as raw material, molded at pressure of 50MPa. Effect of raw material ratio on sintering and themal shock resistance of the mullite-aluminium titanate-corundum composite was researched by measurements of apparent porosity, bending strength and residual strength after water-cool, and analyses of XRD and SEM. The results showed that as refractory clay content, apparent porosity of samples decrease, bulk density and bending strength increase. When the weight ratio of refractory clay, aluminium titanate and high alumina grog is 60/10/30, themal shock resistance of sample is excellent, The XRD and SEM analysis results indicated that the mechanical and thermal proprieties are relative to the microstructure and crystal phases of the composite materials.

Abstract: Australia is fortunate in that it has ~80,760 kt (Ti equivalent) representing 15% of the world’s titanium resources in the form of ilmenite, rutile, anatase and leucoxene. Although of late the annual quantity of mined material has reduced due to the global financial situation, the average amount of material mined was of the order of 700 kt (Ti eq). To date the most common process used for beneficiating the ilmenite in Australia has been the Becher process to produce synthetic rutile of the order of 92-96% TiO2. Due to the nature of the mineralogy of the deposits, a very small amount of naturally occurring radioactive materials (mainly thorium) is present which for some applications is considered unacceptable. Consequently a number of years ago the Synthetic Rutile Enhancement Process (SREP) was developed which removes the thorium contamination through the use of a boron containing mineral additive [1,2,3], which complexes the radioactive material during the reduction process. Unfortunately the consequences of this reaction is the build up of a flux-like material on the walls of the rotary kilns leading to significantly reduced throughput and even significant refractory loss. The aim of this paper is therefore to describe the development of a novel refractory castable system utilising the in-situ formation of aluminium titanate which in combination with matrix chemistry control and thermo-mechanical property design, greatly inhibited the adhesion of process flux on the refractory walls. The development strategy and subsequent history from simulated laboratory testing and early small scale trials up to the performance of the novel refractory in a fully lined kiln operating over a number of years will be highlighted.

Abstract: Solid solutions formed within the Al2O3-TiO2-Fe2O3 (Fe2xAl2(1-x)TiO5) system upon heat treatment were investigated by adjusting the substituting Fe3+ content in the range of x=0.0 to 1.0. X-ray diffraction phase analyses and lattice parameter determinations confirmed that substitution of Fe3+ ions within the aluminium titanate lattice was complete. For this complete solid solution, however, the trends observed for changes in d-spacing values indicated that there were certain discrete compositions to identify with Fe3+ substitution. Within these, Fe0.4Al1.6TiO5 and Fe1.6Al0.4TiO5 crystalline phases were investigated in detail and their X-ray diffraction cards were constructed. Self-healing effect occurring in repeated heating-cooling cycles in Fe3+ doped AT ceramics were proved; it was demonstrated that Fe3+ doped AT ceramics do not decompose even if exposed to repeated thermal shock.

Abstract: Aluminium titanate was synthesized using waste aluminium sludge and chemical pure TiO2 powder as raw materials. Effect of different compositions on crystal structure and contents of target product was discussed. XRD results showed that four crystal phases, aluminium titanate, perovskite, rutile and aluminum oxide, are formed in the sintered samples. The content of aluminium titanate increases first and then decreases with the decrease of the content of waste aluminum sludge. When the content of the sludge is 65.52wt%, the content of aluminium titanate reaches the maximum of 86.1wt%.

Abstract: The purpose of this paper is to investigate the possibility of rod-like Al2TiO5 / α-Al2O3 composites in situ formation via a mechanical activation process. A QM-ISP-4 Planetary Mill was employed to activate mechanically the mixtures of anatase and corundum in air at room temperature for different times. The milled powder mixtures were pressed into platelets and then sintered in air at 1300°C for 3 h. The XRD results showed that only Al2TiO5 and α-Al2O3 phases could be detected in the sintered samples when the activated time reached 30 hours. The SEM observations illustrated the unusual microstructure of Al2TiO5 / α-Al2O3 ceramic composite materials. Abnormal grains with longitudinal length ~10 μm23 transversal length ~1 μm and equiaxed matrix grains of ~3 μm on an average were observed. EDXA proved that the rod-like grains and the fine equiaxed matrix grains were composed of Al2TiO5 and α-Al2O3, separately. The roles of anisotropic grain growth caused by mechanical activation are discussed for the in situ formation of rod-like Al2TiO5 / α-Al2O3 ceramic composite materials.

Abstract: A glass layer with high hardness and fatigue resistance is coated on the aluminum titanate (Al2TiO5) – mullite (3Al2O3⋅2SiO2) composites to improve wear and fatigue resistances. Mullite is added to aluminum titanate to constraint the decomposition of aluminum titanate and exhibit high mechanical strength as well as high elastic modulus. The aluminum titanate composites with various quasi-ductilities through controlling the contents of mullite in the substrate layers are prepared in this study. The results of the load-displacement curves and the resulting contact damages on the surface of glass coating layer by spherical indentation indicate that mullite addition and the glass coating is effective.

Abstract: The synthesis of aluminum titanate solid solution (Al2(1-x)MgxTi1+xO5, x=0, 0.1, 0.2) powders was realized by solid state reaction method using fine commercial α-Al2O3, TiO2 and MgO powders as raw materials. The effect of the introduced amount of MgO on the phase formation of aluminum titanate solid solution was investigated by XRD following the phase evolution. It was revealed that the introduction of MgO strongly affects the formation of Al2(1-x)MgxTi(1+x)O5 solid solution. The easily formed MgTi2O5 acts as the nucleus prompting the formation and lowering the synthesis temperature. The microstructure and properties of the solid solution ceramics were also studied by SEM and measuring the fracture strength and the thermal expansion coefficient.

Abstract: Aluminium titanate (Al2TiO5) is an excellent oxide ceramic material with a very low thermal expand coefficient. Aiming at improving the bending strength Al2TiO5, spodumene was used as additives for preparing Al2TiO5 and the effect of adding spodumene on the mechanical properties of Al2TiO5 was investigated in this paper. It was found that adding spodumene, instead of simple oxides, may significantly enhance the bending strength of Al2TiO5.

Abstract: The purpose of this paper is to investigate the possibility of rod-like Al2TiO5 formation via a mechanical activation process. A QM-ISP-4 Planetary Mill was employed to activate mechanically the mixtures of anatase and corundum in air at room temperature for different times. The milled powder mixtures were then sintered in air at 1300°C for 1 h. The XRD results showed that the milled powder mixtures were completely transformed into Al2TiO5 after sintering, except the mixtures milled for 5 and 10 hours. The SEM observations showed the typical morphology of rod-like Al2TiO5 vary in the range: widths from 0.6 to 1.2 μm, and lengths from 3.0 to 6.0 μm. The rod-like Al2TiO5 formation was attributed to the positive effects caused by the mechanical activation.