# US 5,707,567 A · Process for producing a self-sintered silicon carbide/carbon graphite composite material having interconnected pores which maybe impregnated > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,707,567 A - Document ID: US5707567A - Status: Granted - Kind: A - Application number: 08/459,270 - Filed: 1995-06-02 - Granted: 1998-01-13 - Earliest claimed: 1993-02-10 - Assignees: The Morgan Crucible Company plc - Inventors: Mark E. Pfaff - Web page: https://patentgrep.com/patent/US5707567A ## CPC - C04B 41/009: {characterised by the material treated} - C04B 35/532: containing a carbonisable binder - C04B 35/565: based on silicon carbide - C04B 38/06: by burning-out added substances {by burning natural expanding materials or by sublimating or melting out added substances} - C04B 38/0635: {Compounding ingredients (C04B38/0615 takes precedence)} - C04B 41/5001: {with carbon or carbonisable materials} - F27D 1/0006: {Linings or walls formed from bricks or layers with a particular composition or specific characteristics} - C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE - F27D: DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE ## Abstract A self-sintered silicon carbide/carbon-graphite composite material having interconnected pores which may be impregnated, and a raw batch and process for producing the composite material, is provided. The composite material comprises a densified, self-sintered matrix of silicon carbide, carbon-graphite inclusions and small amounts of any residual sintering aids, such as boron and free carbon, and has interconnected pores which may be impregnated with resin, carbon, TEFLON, (polyetrafluoroethylene) metal or other compounds or materials selected for their particular properties to achieve desired tribological characteristics for a specific application. The composite material is produced from a raw batch which includes silicon carbide, sintering aids, a temporary filler and coated graphite particles. The raw batch is then molded/shaped into a green body and heated to carbonize any carbonizable materials and to decompose and volatilize the organic filler to form a matrix of interconnected pores. The green body is pressureless sintered to densify the matrix. The interconnected pores may then be impregnated with a resin, carbon, metal, TEFLON, (polytetrafluoroethylene) compound or other material selected for desired tribological characteristics. ## Claims ### Claim 1 A process for producing a self-sintered silicon carbide composite material, comprising the steps of: (a) mixing in an inert solvent a raw batch, comprising: (i) about 50 to about 90% by weight silicon carbide; (ii) about 5.0 to about 50% graphite particles coated with a carbon precursor; (iii) about 2 to about 20% sintering aids; and (iv) about 0.75 to about 15.0% by weight temporary filler; (b) drying the raw batch to evaporate the inert solvent; (c) shaping the raw batch into a shaped body; (d) heating the shaped body at a temperature sufficient to carbonize the carbon precursor and volatilize the temporary filler to form a matrix having interconnected pores; and (e) sintering the shaped body to densify the matrix. ### Claim 2 (depends on 1) The process of claim 1, wherein the silicon carbide comprises alpha silicon carbide or beta silicon carbide, or a mixture thereof. ### Claim 3 (depends on 1) The process of claim 1, wherein the carbon precursor comprises phenolic resin, furfuryl alcohol, polyester, petroleum pitch or coal tar pitch, or fixtures thereof. ### Claim 4 (depends on 1) The process of claim 1, wherein the sintering aids comprise aluminum, beryllium oxide, a boron source or a carbon source, or mixtures thereof. ### Claim 5 (depends on 4) The process of claim 4, wherein the boron source comprises elemental boron or boron carbide, or a mixture thereof. ### Claim 6 (depends on 4) The process of claim 4, wherein the carbon source comprises elemental carbon or a carbonizable organic material, or a mixture thereof. ### Claim 7 (depends on 6) The process of claim 6, wherein the carbonizable organic material comprises phenolic resin, petroleum pitch, coal tar pitch, furfuryl alcohol or a sugar, or mixtures thereof. ### Claim 8 (depends on 1) The process of claim 1, wherein the temporary filler comprises an organic material. ### Claim 9 (depends on 8) The process of claim 8, wherein the organic material comprises, ground nutshells, wax particles or polypropylene beads, or mixtures thereof. ### Claim 10 (depends on 1) The process of claim 1, wherein the temporary filler comprises an inorganic material. ### Claim 11 (depends on 10) The process of claim 10, wherein the inorganic material comprises ceramic beads. ### Claim 12 (depends on 1) The process of claim 1, wherein the raw batch further includes about 0.3 to about 1.0% by weight of a suspension agent. ### Claim 13 (depends on 12) The process of claim 12, wherein the suspension agent includes xanthan gum. ### Claim 14 (depends on 1) The process of claim 1, wherein the raw batch further includes 2.0 to about 8.0% by weight of a temporary binder. ### Claim 15 (depends on 14) The process of claim 14, wherein the temporary binder comprises phenolic resin, polyethylene glycol or oleic acid, or a mixture thereof. ### Claim 16 (depends on 1) The process of claim 1, wherein the shaping step includes pressing the raw batch at pressures of about 3 to about 9 tons/in.sup.2 to obtain a green density of about 1.60 to about 1.90 gm/cc. ### Claim 17 (depends on 1) The process of claim 1, wherein the heating step includes heating the shaped body at a temperature above 800.degree. F. ### Claim 18 (depends on 1) The process of claim 1, wherein the sintering step includes heating the shaped body at a temperature of about 1900.degree. to about 2500.degree. C. in a substantially inert atmosphere at or below atmospheric pressure. ### Claim 19 (depends on 1) The process of claim 1, including the further step of impregnating the pores of the matrix with an additional material. ### Claim 20 (depends on 19) The process of claim 19, wherein the additional material comprises carbon, resin, metal or polytetrafluoroethylene, or mixtures thereof. ### Claim 21 (depends on 19) The process of claim 19, wherein the impregnation step comprises the steps of: (a) impregnating the pores of the matrix with a carbonaceous resin; and (b) carbonizing the carbonaceous resin. ### Claim 22 (depends on 21) The process of claim 21, wherein the carbonaceous resin comprises phenolic resin, petroleum pitch or coal tar pitch, or mixtures thereof. ### Claim 23 (depends on 20) The process of claim 20, wherein the metal comprises nickel, silver or antimony, or mixtures thereof. ### Claim 24 (depends on 1) The process of claim 1, wherein the raw batch comprises: (i) about 60 to about 80% by weight silicon carbide; (ii) about 10 to about 20% by weight graphite particles coated with a carbon precursor; (iii) about 5.0 to about 15.0% by weight temporary filler; (iv) about 2.0 to about 8.0% by weight temporary binder; (v) about 1.0 to about 5.0% by weight carbonizable organic material; and (vi) about 0.3 to about 1.5% by weight of a boron source. ### Claim 25 (depends on 24) The process of claim 24, wherein the silicon carbide is alpha silicon carbide or beta silicon carbide, or a mixture thereof. ### Claim 26 (depends on 24) The process of claim 24, wherein the carbon precursor comprises phenolic resin, furfuryl alcohol, polyester, petroleum pitch or coal tar pitch, or mixtures thereof. ### Claim 27 (depends on 24) The process of claim 24, wherein the temporary filler comprises, ground nutshells, wax particles or polypropylene beads, or mixtures thereof. ### Claim 28 (depends on 24) The process of claim 24, wherein the temporary binder comprises phenolic resin, polyethylene glycol or oleic acid, or a mixture thereof. ### Claim 29 (depends on 24) The process of claim 24, wherein the carbonizable organic material is phenolic resin, petroleum pitch, coal tar pitch, furfuryl alcohol or a sugar, or mixtures thereof. ### Claim 30 (depends on 24) The process of claim 24, wherein the boron source comprises elemental boron or boron carbide, or a mixture thereof. ### Claim 31 (depends on 24) The process of claim 24, wherein the raw batch further includes about 0.3 to about 1.0% by weight of a suspension agent. ### Claim 32 (depends on 31) The process of claim 31, wherein the suspension agent includes xanthan gum. ### Claim 33 (depends on 24) The process of claim 24, wherein the shaping step includes pressing the raw batch a green density of about 1.60 to about 1.90 gm/cc. ### Claim 34 (depends on 24) The process of claim 24, wherein the heating step includes heating the shaped body at a temperature above 800.degree. F. ### Claim 35 (depends on 24) The process of claim 24, wherein the sintering step includes heating the shaped body at a temperature ranging from about 1900.degree. to 2500.degree. C. in a substantially inert atmosphere at or below atmospheric pressure. ### Claim 36 (depends on 24) The process of claim 24, including the further step of impregnating the pores of the matrix with an additional material. ### Claim 37 (depends on 36) The process of claim 36, wherein the additional material comprises carbon, resin, metal or polytetrafluoroethylene, or mixtures thereof. ### Claim 38 (depends on 36) The process of claim 36, wherein the impregnation step comprises the steps of: (a) impregnating the pores of the matrix with a carbonaceous resin; and (b) carbonizing the carbonaceous resin. ### Claim 39 (depends on 38) The process of claim 38, wherein the carbonaceous resin comprises phenolic resin, petroleum pitch or coal tar pitch, or mixtures thereof. ### Claim 40 (depends on 37) The process of claim 37, wherein the metal comprises nickel, silver or antimony, or mixtures thereof. ### Claim 41 (depends on 1) The process of claim 1, comprising the steps: (a) mixing in an inert solvent a raw batch, comprising: (i) about 60 to about 80% by weight silicon carbide; (ii) about 10 to about 20% by weight graphite particles coated with phenolic resin; (iii) about 5.0 to about 15.0% by weight polypropylene beads; (iv) about 2.0 to about 8.0% by weight polyethylene glycol; (v) about 1.0 to about 5.0% by weight additional phenolic resin; and (vi) about 0.3 to about 1.5% by weight boron carbide; (vii) about 0.3 to about 1.0%, by weight xanthan gum; and (b) drying the raw batch to evaporate the inert solvent; (c) pressing the raw batch to a green density of about 1.60 to about 1.90 gm/cc; (d) heating the shaped body at a temperature above 800.degree. F. to carbonize the carbon precursor and volatilize the temporary filler to form a matrix having interconnected pores; and (e) sintering the shaped body at a temperature of about 1900.degree. to about 2500.degree. C. in a substantially inert atmosphere at or below atmospheric pressure to densify the matrix to a density of about 2.10 to about 2.60 gm/cc. ### Claim 42 (depends on 41) The process of claim 41, wherein the silicon carbide comprises alpha silicon carbide or beta silicon carbide, or a mixture thereof. ### Claim 43 (depends on 41) The process of claim 41, including the further step of impregnating the pores of the matrix with phenolic resin and carbonizing the impregnated resin.