Assessing porosity limit in freeze‐cast sintered lithium titanate (Li4Ti5O12) materials

Abstract

AbstractThis study aims to assess the lower limit of porosity that can be achieved in freeze‐cast sintered lithium titanate (LTO) materials while maintaining the characteristic pore directionality. LTO materials were fabricated with solid loading varying in the range of 30–37 vol.%. Sucrose and cationic dispersant were used to vary viscosity and total solute concentration in the aqueous LTO suspensions. Two series of suspension compositions were selected for freeze‐casting. In one series, aqueous suspensions were prepared by mixing deionized (DI) water, sucrose, and LTO powder, while in the other series, aqueous suspensions were prepared by mixing DI water, sucrose, cationic dispersant (1‐hexadecyl)trimethylammonium bromide (CTAB), and LTO powder. With increasing solid loading from 30 to 37 vol.%, porosity in the sintered materials decreased from about 50 to 36 vol.%. LTO materials fabricated from suspensions containing sucrose exhibited well‐developed characteristic freeze‐cast microstructure. Unexpectedly, LTO materials fabricated from suspensions containing sucrose and dispersant exhibited cellular pore morphology irrespective of the solid loading. Sample height had an impact on microstructure evolution in the transition zone and zone length. With the increasing solid loading from 30 to 37 vol.%, the compressive strength of sintered LTO materials having the characteristic freeze‐cast microstructure increased from about 110 to 240 MPa.