Manufacture of Highly Porous Tubular Alumina Substrates with Anisotropic Pore Structure by Freeze-Casting

Daniel D. Athayde, Bruno M. Sousa, Ana Clara A. Dolabella, Jéssica de O. N. Ribeiro, Daniela C. L. Vasconcelos, João C. Diniz da Costa, Wander L. Vasconcelos

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


This work investigates the production of freeze-cast tubular alumina substrates with anisotropic pores. The freeze-casting method allows accurate control of the radial pore structure by adjusting the solid loading and sintering temperature. High porosities of 91% are attained, which decrease inversely proportional to the solid loading. Water is used as the pore forming agent by the freeze-cast process, producing lamellar pores with highly connected aligned structure. Substrates with solid loadings within 15–20% show maximum pore alignment and anisotropy, as higher solid loading creates more isotropic pores. The average pore size distribution decreases from 11 to 2 μm as a function of the solid loading. By increasing the sintering temperature from 1300 to 1500 °C, the crushing strength significantly increases for samples prepared with high solid loading, reaching values as high as 25.4 MPa. A plot of the mechanical stability versus porosity reveals that the substrates obtained in this study show a similar trend when compared with previously reported flat substrates. Water permeation reaches 510 L m−2 min−1, showing a strong influence of the pore size. Therefore, processing of freeze-cast tubular substrates from aqueous suspensions proves to be a versatile technique for manufacturing advanced engineering materials with anisotropic pore structure.

Original languageEnglish
Article number1901432
JournalAdvanced Engineering Materials
Issue number7
Publication statusPublished - 1 Jul 2020


  • alumina
  • anisotropy
  • freeze-casting
  • porous structure
  • tubular geometries


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