Dispersion and densification of nano Si–(Al)–C powder with amorphous/nanocrystalline bimodal microstructure

Abstract

The dispersion behavior and densification of nano Si–(Al)–C powder with amorphous/nanocrystalline bimodal microstructure were investigated. The Si–C powders synthesized by a mechanical alloying (MA) process had a near‐spherical shape with an average particle size of 170 nm. A solid loading of 62 vol% was achieved using polyethyleneimine (PEI) as a dispersant. The optimum dispersant amount was 1 wt% based on zeta potential, sedimentation, and viscosity analysis data. The high zeta potential value (73 mV) compared with that of the commercially available SiC (65 mV) was caused by modified surface properties and consequent promotion of the cationic dispersant adsorption. A Si–Al–C slurry containing 6.5 wt% of sintering additives with a solid loading of 60 vol% was also prepared. The relative density of the dried Si–Al–C slurry was 63.3% without additional compaction, which could be densified at 1650°C at a pressure of 20 MPa using a spark plasma sintering furnace.

Highly concentrated aqueous SiC slurry containing fine SiC powder: A new approach for ultra‐dense green body

“…8 MA-SiC was also termed fine SiC. The MA-SiC powder was synthesized by milling silicon powder and carbon black using a planetary mill (Pulverisette 5/4; Fritsch, Idar-Oberstein) and SiC ball (φ5 mm; Nicato Co.) under 360 rpm for 72 hours.…”

“…Fine SiC powder was added into the dispersoid under stirring condition and ultra-sonication (VCX750, Sonics and Materials). 8 As a consequence, highly concentrated slurry could be prepared. After complete mixing of the powder with the dispersoid, the suspension was sonicated for 30 minutes and the viscosity value was measured using a viscometer (HB DV-II + pro, Brookfield Engineering Laboratories).…”

“…18 Polyelectrolytes such as polyacrylic acid (PAA), polymethylacrylic acid (PMAA) and their salts have been generally adopted for the dispersion of ceramic powders in water. 8,14,[25][26][27] Polyethylene glycol (PEG) has been also used as a dispersant to prepare slurry. 8,14,[25][26][27] Polyethylene glycol (PEG) has been also used as a dispersant to prepare slurry.…”

“…The MA-SiC powder was synthesized by milling silicon powder and carbon black using a planetary mill (Pulverisette 5/4; Fritsch, Idar-Oberstein) and SiC ball (φ5 mm; Nicato Co.) under 360 rpm for 72 hours. 8 MA-SiC was also termed fine SiC. Commercially available SiC powders with the average particle size of 3, 5, and 10 μm (Grand Co., hereafter termed coarse SiC) were used in order to improve the dispersion behavior of the MA-SiC (fine SiC) powder.…”

“…5,6 Table 1 summarizes the reported dispersion data of SiC slurries. 4,[7][8][9][10][11][12][13][14][15] Zhang et al could prepare 57 vol% aqueous slurry using PEI and citric acid as dispersants. 9 Wei et al reported the preparation of 70 vol% slurry by mixing 52 wt% coarse powder and 48 wt% PAAM-coated SiC powder.…”