Consolidation behavior of nanometer-sized SiC particles with phenylalanine through pressure filtration at 1 MPa

Abstract

The consolidation behavior of two kinds of colloidal SiC particles (30 and 330 nm diameters) with and without phenylalanine dispersant (C 6 H 5 CH 2 CHNH 3 + COO ¹ ) at pH 7 was examined using a developed pressure filtration apparatus at 1 MPa of applied pressure. The height of 5 vol %-30 nm SiC suspension with and without phenylalanine as a function of filtration time was well simulated by a filtration model developed for a flocculated suspension rather than a traditional filtration model for a dispersed suspension. The result with phenylalanine is related to the colloidal phase transition from well dispersed particles to flocculated particles under an applied pressure of 1 MPa. The consolidation time became longer as the amount of phenylalanine added exceeded 0.1 mg/m 2 -SiC. However, the packing density of 30 nm SiC particles after consolidation increased from 35% for no addition of phenylalanine to 3742% for 0.11 mg phenylalanine/m 2 -SiC. The consolidation behavior of 20 vol %-330 nm SiC suspension with and without phenylalanine was also well expressed by the filtration model for a flocculated suspension. A longer consolidation time was also measured for the addition of phenylalanine above 1 mg/m 2 -SiC. However, the packing density (49%) of 330 nm SiC particles increased scarcely to 52% by the addition of phenylalanine (2.68 © 10 ¹2 2.85 mg/m 2 -SiC).

Influence of phenylalanine dispersant on colloidal processing of alumina particles

“…In the pH range of 3-9, PHA contains both NH 3 þ and COO À groups but the total charge results in neutral. In the acidic suspensions, a small amount of AlO À sites is covered with neutral phenyl group through the adsorption of NH 3 þ groups of PHA, resulting in the increased total potential to positive value [9]. In the basic suspensions, COO À groups of PHA are adsorbed on AlOH 2 þ sites to have neutral groups toward the diffusion layers, leading to increase in the zeta potential to negative values.…”

“…Phenylalanine with the charged groups (-NH 3 þ , -COO À ) also promoted the packing density of 30 nm SiC particles and 150 nm Al 2 O 3 particles consolidated via pressure filtration [8][9][10]. The microstructures of consolidated SiC compacts became more uniform when phenylalanine was added.…”