A dynamic analysis of the aluminum titanate (Al2TiO5) reaction-sintering from alumina and titania, properties and effect of alumina particle size

Abstract

Aluminum titanate Al 2 TiO 5 materials were successfully processed from different fine commercial powders and characterized. Particularly, two calcined aluminas were compared through a multitechnique approach including differential thermal analysis and dilatometry together with structural, microestructural, and mechanical characterization. This allowed the description of all the thermochemical processes during thermal treatment. Developed phases were established. Relatively dense ceramics were obtained, and complex microstructures were described with interlocked grains and an interconnected microcrack matrix that do not jeopardize the material integrity. Multistep sintering and reaction sintering processes were observed in both samples. The first stage consists of the sintering of the starting powders (alumina and titania). A second sintering stage of the starting powders was observed for both samples as well. Once advanced, the second one is overlapped with Al 2 TiO 5 formation that starts at 1380 °C and finishes at 1440 °C. They affect crack development and, in consequence, the thermal behavior. The lower alumina particle size enhances the sintering and reaction advance processes. In the technological temperature range (room temperature-1000 °C), low or even negative thermal expansion behaviors were observed in the developed materials. This, together with the mechanical behavior, encourages structural applications with high thermomechanical solicitations of Al 2 TiO 5 based materials.

Effect of Al2TiO5 Content and Sintering Temperature on the Microstructure and Residual Stress of Al2O3–Al2TiO5 Ceramic Composites

“…The AT grains in the A-40AT composites exhibited a distinct irregular shape and heterogeneity in size distribution, as indicated by the arrows in Figure 3e,g. Some AT grains clustered together as a submatrix (4-6 µm), where alumina grains were separated and surrounded by AT grains; a similar phenomenon was also reported in another study [38]. The Al 2 O 3 grain size evidently decreased as the AT content increased owing to the inhibiting effect of second-phase AT particles on the Al 2 O 3 matrix grain growth.…”

“…A previous study [37] investigated the dynamic phase formation in the temperature range of 20-1400 • C for the fabrication of A-AT samples by means of neutron diffraction and differential thermal analysis. The results showed that the formation of AT in A-AT samples occurred at temperatures exceeding 1310 • C by the reaction sintering of the Al 2 O 3 and TiO 2 mixture; TiO 2 disappeared at 1370 • C. Violini et al [38] reported that in the two-step reaction sintering of initial powders (alumina and titania), the formation of AT started at 1380 and ended at 1440 • C. In our work, the sintering temperature 1450 • C ensured the complete formation of AT. However, in the XRD profiles of the A-10AT(1550) and A-40AT(1550) composites, in addition to the main peaks of the Al 2 O 3 and AT phases, a small peak of TiO 2 (rutile) phase was detected at around 2θ = 7.6 • (hkl = 110).…”

“…The results showed that the formation of AT in A-AT samples occurred at temperatures exceeding 1310 °C by the reaction sintering of the Al2O3 and TiO2 mixture; TiO2 disappeared at 1370 °C. Violini et al [38] reported that by limiting its grain growth [40,41]. The heat treatment temperature plays an important role in the grain growth progress.…”

“…Owing to the crystallographic anisotropy of thermal expansion in the orthorhombic structure, the grain growth of AT particulates became more abnormal. Microcracks form once the grain size of AT reaches the critical size (approximately 2 µm) necessary for microcracking [38,43]. Compared with the A-40AT(1450) The effect of sintering temperature was observed as follows.…”

Electrospun fibers as drying additive in cement‐bonded alumina castables

“…The curve of the LC-TiO 𝑥 -3 presented a clear decrease in slope at about 1300 • C, which was not observed for the other batches, indicating a possible phase transformation within the material, for example, the formation of aluminum titanate. 20,34 A similar trend was not observed for the LC-TiO 𝑥 batch, Finally, the thermal expansion coefficients 𝛼 were calculated from the dilatometry results in two distinct temperature ranges (see Table 5). Overall, the castables showed almost the same behavior, except at temperatures close to T dL max .…”