2014 年 122 巻 1428 号 p. 586-590
The influence of phenylalanine as a dispersant on the viscoelastic properties of alumina suspensions at pH 7.0 was examined in the temperature range from –100°C to +100°C. Only a small amount of phenylalanine, with both NH3+ and COO– groups present in each molecule, was adsorbed onto the positively charged alumina surfaces at room temperature. The peaks of the storage modulus and loss tangent, which were associated with the colloidal phase transition from a dispersed state to a flocculated state, were observed in 10 vol % suspensions in 39–62°C temperature range. The addition of a small amount phenylalanine enhanced the dispersibility of alumina particles and suppressed the colloidal phase transition. In the concentrated 20–30 vol % alumina suspensions containing phenylalanine, no phase transition was evident in the storage modulus or loss tangent measurements of the suspension upon heating. The addition of phenylalanine to the concentrated suspensions drastically reduced the apparent viscosity at room temperature.
