Effect of TMAH on the rheological behavior of alumina slurries for gelcasting

Tetramethyl ammonium hydroxide (TMAH) has been demonstrated to increase solids loading effectively and to accelerate gelling rate of alumina slurries gelled by Isobam (a copolymer of isobutylene and maleic anhydride) system. With 0.5 vol% addition of TMAH, solids loading of alumina slurry was increased from 56 vol% to 58 vol%. Meanwhile, storage modulus (G') of the slurry with 56 vol% solids loading was increased from 964 Pa to 2850 Pa at a testing time of 30 min. The enhanced dispersing and gelling behavior was ascribed to the hydrolysis and hydrophobic modification of Isobam by TMAH. Flexural strength of the final alumina ceramics from 58 vol% solids loading was 543 ± 10 MPa, higher than that of the ceramics from 56 vol% solids loading (531 ± 13 MPa).