A preliminary study of precipitation in Ti4+-doped polycrystalline alumina

Microstructures and Adhesion of the Oxide Scale Formed on Titanium Aluminum Carbide Substrates

“…Circular precipitates with 5-60 nm in diameter were observed within the Al 2 O 3 scale. [17][18][19][20][21] As far as Ti 3 AlC 2 and Ti 2 AlC are concerned, the detected precipitates were mainly TiO 2 . Fast Fourier transformation (FFT) analysis indicated that the subgrain is TiO 2 .…”

“…Fast Fourier transformation (FFT) analysis indicated that the subgrain is TiO 2 . 20,21 For example, Langensiepen et al 20 investigated the precipitation in Ti 41 -doped polycrystalline Al 2 O 3 and reported that rutile precipitated in the Al 2 O 3 ceramic. It is seen that the contrasting white regions were located either in the Al 2 O 3 grains or at grain boundaries (GB).…”

“…TiO 2 , Ti 2 O 3 , and Al 2 TiO 5 have been observed previously in Ti-containing Al 2 O 3 depending on the atmosphere and composition. [17][18][19][20][21] As far as Ti 3 AlC 2 and Ti 2 AlC are concerned, the detected precipitates were mainly TiO 2 . This precipitation can be attributed to the low solubility of TiO 2 in Al 2 O 3 , which may occur during cooling.…”

Effect of yttria doping on the microstructure and mechanical properties of Al2O3–FeAl2O4 nanocomposites developed via solid state precipitation

“…However, due to the limited solubility of most cations in Al 2 O 3 and the difficulty of nucleating second phase particles within the alumina grains, most previous reports which explore this possibility have not been able to develop a sufficient volume fraction of well dispersed nanoparticles to establish reproducible property improvements. 17,18 Recently, however, we have reported the production of viable nanocomposites by using Fe 2 O 3 solid solutions in Al 2 O 3 . 19,20 Fe 2 O 3 (haematite) has the same crystal structure as ␣-Al 2 O 3 (corundum) and possesses substantial solubility in Al 2 O 3 at moderately high temperatures in air (∼15 wt.% at ∼1410 • C).…”

Microstructure and mechanical properties of Al2O3 matrix nanocomposites produced by solid state precipitation

“…Submicron-sized TiO 2 needles within the matrix grains of polycrystalline Al 2 O 3 , along with coarser Al 2 TiO 5 precipitates at the triple point corners of the matrix grain boundaries, were also obtained during heating in an oxidizing atmosphere of (Al 1−x ,Ti x 3+ ) 2 O 3 solid solutions containing a maximum of only 0.6 cation% Ti. 15 In a more recent investigation, Wang et al 6 developed an Al 2 O 3 -based nanocomposite by precipitation of nanocrystalline magnesium aluminium spinel (MgAl 2 O 4 ) during aging in a reducing atmosphere of a supersaturated charge compensated solid solution of Mg 2+ and Ti 4+ ions in Al 2 O 3 . However, due to limited solubility in Al 2 O 3 , only a maximum of 2 mol% (MgO + TiO 2 ) can be incorporated during solution treatment which limits the volume fraction of the second phase particles that can be precipitated out during the aging treatment.…”