Effect of titania addition on the properties of freeze-cast alumina samples

Abstract

This work investigated the behavior of TiO 2 -containing α-Al 2 O 3 samples prepared by the freeze-casting technique. Camphene and liquid nitrogen were used as the solvent and cooling fluid, respectively. Camphene resulted in the formation of dendritic pores, in the direction of the freeze-casting cold front during sample preparation. The formation of β-Al 2 TiO 5 phase occurred at 1300 °C, and became more evident as the sintering temperatures reached 1500 °C. The TiO 2 loading did not affect the sample porosity at a given temperature, but it was detrimental in the case of mechanical properties under certain conditions. For instance, the flexural strength slightly improved with increasing the TiO 2 loading and sintering temperature from 1100 to 1300 °C. This effect was attributed to the occurrence of a more effective sintering of alumina.However, as the heat treatment temperature was raised from 1300 to 1500 °C, the flexural strength did not increase as a function of the TiO 2 loading, even though the densification occurred with loss of porosity. The loss of mechanical strength was found to be associated with the formation of microcracks which stemmed from the formation of β-Al 2 TiO 5 phase for TiO 2 loadings in excess of 4 wt% at these high sintering temperatures.

Freeze‐Casting of Surface‐Magnetized Iron(II,III) Oxide Particles in a Uniform Static Magnetic Field Generated by a Helmholtz Coil

“…These slurries were sealed in a 40 mL plastic bag and mixed by sonicating at 42 kHz for 12 min. Using sonication to mix the slurries is similar to methods that have proven effective in the past reports on freeze‐cast slurries . Immediately following mixing, the individual slurries were poured into a PVC freeze‐cast mold of diameter 20 mm and then directionally frozen from room temperature at a rate of 10°C min −1 within a custom Helmholtz‐coil‐based magnetic freeze‐caster, as illustrated in Figure .…”

Effect of talc and titania on the microstructure and mechanical properties of alumina ceramics

“…It has been reported that TiO 2 is a good mineralizer for promoting the crystallization of the MA and A 3 S 2 . In addition, TiO 2 was frequently employed to enhance the sintering of Al 2 O 3 ceramics through the formation of Al 2 O 3 ‐TiO 2 solid solution . Therefore, TiO 2 was added in this work to guarantee the formation of MA and A 3 S 2 in Al 2 O 3 ceramics.…”

“…[17][18][19][20] In addition, TiO 2 was frequently employed to enhance the sintering of Al 2 O 3 ceramics through the formation of Al 2 O 3 -TiO 2 solid solution. [21][22][23][24] Therefore, TiO 2 was added in this work to guarantee the formation of MA and A 3 S 2 in Al 2 O 3 ceramics. However, the simultaneous addition of TiO 2 and talc for sintering Al 2 O 3 ceramics has not been reported so far.…”

The influence of Fe2O3 doping on the pore structure and mechanical strength of TiO2-containing alumina obtained by freeze-casting

“…The freeze-cast samples were obtained following a method as published elsewhere [32]. Subsequently, the slurries were poured into a freeze casting rig containing a high thermal conductivity copper plate and a polytetrafluoroethylene (PTFE) mold.…”

“…For instance, it is well known that doping titania into alumina tends to form an aluminum titanate (Al 2 TiO 5 ) phase with superior mechanical strength than alumina [31]. Recently, it was reported that TiO 2 doping with loadings above 4 wt% reduced the mechanical strength in freezecast alumina which was associated with the formation of microcracks [32]. Hence, metal oxide doping must be controlled to a point where it is no longer beneficial.…”