Bibliographic Information

"Improved Consolidation of Silicon Carbide," M.R. Freedman and M.L. Millard, Ceramic Engineering and Science Proceedings, Vol. 7 [7], pp. 884-892 (1986), published by American Ceramic Society.

General Materials Processing Notes

"The dry-pressed specimens were prepared by combining 200 g of SiC powder and additives with 500 mL of ethanol in a one liter polyethylene bottle. Four hundred grams of 12 x 12 mm SiC cylinders were added as a mixing aid and the bottle was rotated at 80 rpm for 72 h. After mixing, the slurry was dried on a hot plate at 150 °C-200 °C. This procedure produced large, hard flakes which were then dry milled for several hours to reduce their size. The milled powder was sieved through a 100-mesh screen. Bars (approximately 3.8 cm x 0.8 cm x 0.45 cm) were dry pressed at 83 MPa in a double-acting WC-lined die. The bars were then sealed in latex tubing and hydrostatically pressed at 413 MPa. Two groups of slurry-pressed specimens were fabricated. The specimens of the first group were prepared by mixing 200 g of SiC powder plus additives with 225 mL ethanol (about 22% (volume fraction) solids) and 400 g of SiC media in a polyethylene bottle for 72 h. After mixing, the slurry was pressed into green pucks (approximately 5.0 cm diameter x 0.8 cm thick) using an applied pressure of 14 MPa. The pucks were kept in a vacuum dessicator over ethanol for 24 h followed by drying in ambient air for 24 h. After drying at 100 °C in air for 12 h, the pucks were vacuum sealed in a plastic bag and hydrostatically pressed at 413 MPa. These pucks and test specimens derived from them will hereafter be referred to as ethanolic slurry-pressed specimens. The second group of slurry-pressed specimens were prepared by mixing 200 g of SiC plus additives with 225 mL solution of water/ammonium hydroxide (pH 11.2) and 400 g of cylindrical SiC media in a polyethylene bottle. The pH of the slurry was adjusted to 11.0 with ammonium hydroxide. After mixing for 72 h, the pH was readjusted to 11.0. The slurry was pressed into green pucks, dried and hydrostatically pressed in a manner similar to the first group. These pucks and test specimens derived from them will hereafter be referred to as aqueous slurry-pressed specimens. Both the dry-pressed specimens were randomized, loaded in an induction furnace, sintered at 2150 °C for 1.75 h under an argon atmosphere. The heating rate was 50 °C/min. After sintering, the slurry-pressed pucks were machined into MOR test bars ((about) 3.0 cm x 0.6 cm x 0.3 cm). Both the dry-pressed and slurry-pressed bars were surface ground. The finish surface grinding step required ten passes in the longitudinal direction using 400-grit diamond. All edges of the bar were beveled."

Measurement Methods

"...density (was) determined by weighing and measuring..." No additional measurement details were noted.

"...four-point flexural strength (0.95 cm inner span, 1.90 cm outer span)..." was determined. No additional measurement details were noted.

Index of Materials and Properties