Back to results
US 5,395,807 AGranted
Process for making silicon carbide with controlled porosity
AssigneeThe Carborundum Company
InventorsRamesh Divakar, Sai-Kwing Lau
Life of this patent
Estimating the term…
Abstract
Silicon carbide sintered bodies having controlled porosity in the range of about 2 to 12 vol %. in which the pores are generally spherical and about 50 to 500 microns in diameter, are prepared from raw batches containing a polymer fugitive. Sintered bodies in the form of mechanical seal members exhibit lower power consumption at low PV and, in addition, lower wear rates at high PV in comparison to commercially available silicon carbide seal members.
Claims32
A process for producing a porous silicon carbide sintered body having a porosity of from about 2 to about 12 vol % and pores which:
- are distributed uniformly throughout the silicon carbide substantially free of interconnection with adjacent pores;
- are closed and generally spherical in shape;
- and have a nominal diameter of from about 50 to about 500 microns, the process comprising:
- (a) preparing a mixture comprising (1) about 75 wt % to about 95 wt % silicon carbide;
- (2) about 0.3 wt % to about 3 wt % of a sintering element selected from the group consisting of boron, aluminum and mixtures thereof;
- (3) about 0.3 wt % to about 20 wt % carbon source;
- and (4) about 1.2 wt % to about 5 wt % binder, by blending the silicon carbide, the sintering element, the carbon source, and the binder;
- (b) preparing a dispersion comprising a polymer fugitive in the form of generally spherical beads having a nominal diameter of from about 50 to about 500 microns dispersed in an inert solvent;
- (c) stirring said mixture and adding said dispersion thereto producing a slurry, the dispersion being added in an amount sufficient to give from about 0.5 to about 7 wt % of the polymer fugitive based on the weight of silicon carbide, sintering element, carbon source, binder, and polymer fugitive therein;
- (d) drying said slurry, yielding a raw batch as a flowable powder, the polymer fugitive being dispersed in the raw batch such that the beads are substantially free of contact with adjacent beads;
- (e) compacting said raw batch into a green body;
- and
- (f) sintering said green body at a temperature between about 2060.degree. C. and about 2200.degree. C. under an inert atmosphere to obtain said porous silicon carbide sintered body.
10 more elements
A process for producing a porous silicon carbide sintered body having a porosity of from about 2 to about 12 vol % and pores which:
- are distributed uniformly throughout the silicon carbide substantially free of interconnection with adjacent pores;
- are closed and substantially spherical in shape;
- and have a nominal diameter of from about 50 to about 200 microns, the process comprising:
- (a) preparing a slurry by dispersing a raw batch mixture in an inert solvent, the raw batch mixture comprising:
- (1) about 75 wt % to about 95 wt % silicon carbide;
- (2) about 0.3 wt % to about 3 wt % boron;
- (3) about 0.3 wt % to about 20 wt % carbon source;
- (4) about 1.2 wt % to about 5 wt % binder;
- and (5) about 0.5 to about 7 wt % of a polymer fugitive in the form of substantially spherical beads having a nominal diameter of from about 50 to about 200 microns;
- (b) drying said slurry, yielding the raw batch as a substantially uniform mixture in the form of a flowable powder, the polymer fugitive being dispersed in the mixture such that the beads are substantially free of contact with adjacent beads;
- (c) compacting the raw batch powder into a green body;
- and
- (d) sintering said green body at a temperature between about 2060.degree. C. and about 2200.degree. C. under an inert atmosphere to obtain said porous silicon carbide sintered body.
10 more elements
A process for producing a porous silicon carbide sintered body having a porosity of from about 2 to less than about 9 vol % and pores which:
- are distributed uniformly throughout the silicon carbide substantially free of interconnection with adjacent pores;
- are closed and substantially spherical in shape;
- and have a nominal diameter of from about 50 to about 200 microns, the process comprising:
- (a) preparing a mixture comprising (1) about 75 wt % to about 95 wt % silicon carbide;
- (2) about 0.3 wt % to about 3 wt % boron;
- (3) about 0.3 wt % to about 20 wt % carbon source;
- and (4) about 1.2 wt % to about 5 wt % binder, by blending the silicon carbide, the boron, the carbon source, and the binder;
- (b) preparing a dispersion comprising a polymer fugitive in the form of substantially spherical beads having a nominal diameter of from about 50 to about 200 microns dispersed in an inert solvent;
- (c) stirring said mixture and adding said dispersion thereto producing a slurry, the dispersion being added in an amount sufficient to give from about 1 to about 4 wt % of the polymer fugitive based on the weight of silicon carbide, sintering element, carbon source, binder, and polymer fugitive therein;
- (d) drying said slurry, yielding the raw batch as a substantially uniform mixture in the form of a flowable powder, the polymer fugitive being dispersed in the mixture such that the beads are substantially free of contact with adjacent beads;
- (e) compacting the raw batch powder into a green body;
- and
- (f) sintering said green body at a temperature between about 2060.degree. C. and about 2200.degree. C. under an inert atmosphere to obtain said porous silicon carbide sintered body.
10 more elements
Dependencies are inferred from the claim text.