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Effect of Solids Loading on Slip‐Casting Performance of Silicon Carbide Slurries
Author(s) -
Ferreira José M. F.,
Diz Henrique M. M.
Publication year - 1999
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1999.tb02031.x
Subject(s) - dispersant , materials science , slurry , slip (aerodynamics) , silicon carbide , sphere packing , particle size , microstructure , tape casting , rheology , green body , composite material , chemical engineering , particle size distribution , particle (ecology) , mineralogy , sintering , chemistry , oceanography , physics , geology , optics , thermodynamics , engineering , dispersion (optics)
The influence of solids loading and particle shape on the green microstructure of slip‐cast bodies was investigated. Three commercial silicon carbide (SiC) powders (two coarse varieties with the same particle‐size distribution (PSD) but different particle shapes and a finer powder) were used to prepare bimodal PSDs designed to maximize the packing density. Various surface‐active agents (anionic, cationic, and non‐ionic) were tested. Anionic dispersants were the most effective in dispersing aqueous SiC slurries. The effectiveness of dispersants was evaluated by sedimentation tests using very dilute slurries, by rheology, and by the packing density of slip‐cast bodies prepared from suspensions loaded with 62.5 wt% solids, stabilized with a fixed amount of dispersant (0.25 wt%, relative to the solids). Then, the best dispersant was selected to study the effects of dispersant and solids concentrations on the degree of packing of bimodal suspensions that contained the sharper‐edged coarse particles. It could be observed that the green density was dependent on both parameters, initially showing an increase to a maximum, followed by a decreasing trend. A high value of 74.5% of the theoretical density (TD) was obtained from suspensions that contained 70 wt% solids and 0.1 wt% dispersant. The substitution of the angular coarse particles by similarly sized but more spherical particles resulted in an additional increase in green density to >76 wt% TD. The results can be interpreted in terms of freedom of particles upon deposition on the cast layer, which enables particle rearrangement, and segregation phenomena.