CA2356191C - Composite foam, articles, and methods of formation - Google Patents
Composite foam, articles, and methods of formation Download PDFInfo
- Publication number
- CA2356191C CA2356191C CA002356191A CA2356191A CA2356191C CA 2356191 C CA2356191 C CA 2356191C CA 002356191 A CA002356191 A CA 002356191A CA 2356191 A CA2356191 A CA 2356191A CA 2356191 C CA2356191 C CA 2356191C
- Authority
- CA
- Canada
- Prior art keywords
- carbon
- foam
- composite foam
- carbon composite
- coating
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 239000006260 foam Substances 0.000 title claims abstract description 160
- 239000002131 composite material Substances 0.000 title claims abstract description 98
- 238000000034 method Methods 0.000 title claims abstract description 69
- 230000015572 biosynthetic process Effects 0.000 title description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 55
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 42
- 238000000576 coating method Methods 0.000 claims abstract description 30
- 238000000151 deposition Methods 0.000 claims abstract description 14
- 239000002783 friction material Substances 0.000 claims abstract description 9
- 239000012705 liquid precursor Substances 0.000 claims description 47
- 239000007787 solid Substances 0.000 claims description 28
- 239000011248 coating agent Substances 0.000 claims description 27
- 229920001247 Reticulated foam Polymers 0.000 claims description 22
- 239000011148 porous material Substances 0.000 claims description 22
- 239000002296 pyrolytic carbon Substances 0.000 claims description 18
- 210000003041 ligament Anatomy 0.000 claims description 16
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 claims description 12
- 230000006698 induction Effects 0.000 claims description 12
- 238000010438 heat treatment Methods 0.000 claims description 10
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 claims description 8
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims description 7
- 229910010271 silicon carbide Inorganic materials 0.000 claims description 7
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 6
- 238000005229 chemical vapour deposition Methods 0.000 claims description 6
- 239000012530 fluid Substances 0.000 claims description 6
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 6
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 claims description 5
- 239000004642 Polyimide Substances 0.000 claims description 5
- 229920001721 polyimide Polymers 0.000 claims description 5
- 229920002635 polyurethane Polymers 0.000 claims description 5
- 239000004814 polyurethane Substances 0.000 claims description 5
- 229910000077 silane Inorganic materials 0.000 claims description 5
- 229910003481 amorphous carbon Inorganic materials 0.000 claims description 4
- KTQYJQFGNYHXMB-UHFFFAOYSA-N dichloro(methyl)silicon Chemical compound C[Si](Cl)Cl KTQYJQFGNYHXMB-UHFFFAOYSA-N 0.000 claims description 4
- LIKFHECYJZWXFJ-UHFFFAOYSA-N dimethyldichlorosilane Chemical compound C[Si](C)(Cl)Cl LIKFHECYJZWXFJ-UHFFFAOYSA-N 0.000 claims description 4
- 239000005055 methyl trichlorosilane Substances 0.000 claims description 4
- 239000005048 methyldichlorosilane Substances 0.000 claims description 4
- JLUFWMXJHAVVNN-UHFFFAOYSA-N methyltrichlorosilane Chemical compound C[Si](Cl)(Cl)Cl JLUFWMXJHAVVNN-UHFFFAOYSA-N 0.000 claims description 4
- 230000002093 peripheral effect Effects 0.000 claims description 3
- 238000000197 pyrolysis Methods 0.000 claims description 3
- CREMABGTGYGIQB-UHFFFAOYSA-N carbon carbon Chemical compound C.C CREMABGTGYGIQB-UHFFFAOYSA-N 0.000 claims 66
- 239000011203 carbon fibre reinforced carbon Substances 0.000 claims 66
- 238000005979 thermal decomposition reaction Methods 0.000 claims 6
- 238000005524 ceramic coating Methods 0.000 claims 4
- 235000013824 polyphenols Nutrition 0.000 claims 4
- 229920001187 thermosetting polymer Polymers 0.000 claims 4
- 239000004634 thermosetting polymer Substances 0.000 claims 4
- 238000000280 densification Methods 0.000 abstract description 21
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 17
- 229920000049 Carbon (fiber) Polymers 0.000 description 9
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 8
- 239000004917 carbon fiber Substances 0.000 description 8
- 230000008021 deposition Effects 0.000 description 8
- 239000000835 fiber Substances 0.000 description 8
- 239000000463 material Substances 0.000 description 7
- 229920000642 polymer Polymers 0.000 description 7
- 239000002243 precursor Substances 0.000 description 7
- 238000000354 decomposition reaction Methods 0.000 description 6
- 239000000919 ceramic Substances 0.000 description 5
- 238000011084 recovery Methods 0.000 description 5
- 239000004744 fabric Substances 0.000 description 4
- 239000011159 matrix material Substances 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 239000007788 liquid Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- 150000001721 carbon Chemical class 0.000 description 2
- 239000004020 conductor Substances 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 229910001873 dinitrogen Inorganic materials 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 230000001965 increasing effect Effects 0.000 description 2
- 239000011261 inert gas Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 150000001282 organosilanes Chemical class 0.000 description 2
- 229920002239 polyacrylonitrile Polymers 0.000 description 2
- 238000010926 purge Methods 0.000 description 2
- 230000002787 reinforcement Effects 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- 229920002379 silicone rubber Polymers 0.000 description 2
- 239000004945 silicone rubber Substances 0.000 description 2
- 229910052582 BN Inorganic materials 0.000 description 1
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000004873 anchoring Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000003610 charcoal Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 229920001973 fluoroelastomer Polymers 0.000 description 1
- 238000005187 foaming Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 238000005087 graphitization Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 238000001764 infiltration Methods 0.000 description 1
- 230000008595 infiltration Effects 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 239000000696 magnetic material Substances 0.000 description 1
- 239000011302 mesophase pitch Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000004745 nonwoven fabric Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000010422 painting Methods 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N phenol group Chemical group C1(=CC=CC=C1)O ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- -1 silane compound Chemical class 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 238000012421 spiking Methods 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
- 238000011282 treatment Methods 0.000 description 1
- 238000009834 vaporization Methods 0.000 description 1
- 230000008016 vaporization Effects 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- 239000002759 woven fabric Substances 0.000 description 1
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- F16D69/00—Friction linings; Attachment thereof; Selection of coacting friction substances or surfaces
- F16D69/02—Composition of linings ; Methods of manufacturing
- F16D69/023—Composite materials containing carbon and carbon fibres or fibres made of carbonizable material
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/71—Ceramic products containing macroscopic reinforcing agents
- C04B35/78—Ceramic products containing macroscopic reinforcing agents containing non-metallic materials
- C04B35/80—Fibres, filaments, whiskers, platelets, or the like
- C04B35/83—Carbon fibres in a carbon matrix
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Composite Materials (AREA)
- Materials Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Braking Arrangements (AREA)
- Carbon And Carbon Compounds (AREA)
- Manufacture Of Macromolecular Shaped Articles (AREA)
- Mechanical Operated Clutches (AREA)
Abstract
A composite structure is formed by depositing one or more coatings on an ope n- cell foam skeleton to form a higher-density composite foam. In accordance with one aspect of the invention, the composite foam can be a carbon/carbon composite formed by a rapid densification process. The composite structure is suitable for use, for example, as a friction material employed in clutch and brake devices.
Description
COMPOSITE FOAM, ARTICLES, AND METHODS OF FORMATION
BACKGROUND OF THE INVENTION
Relatively-dense carbon/carbon composites have been found to be highly useful in a variety of structural applications. Because of certain characteristics, such as high strength, high stiffness, light weight, high temperature resistance, and advantageous frictional properties, these composites are desirably suited for use, for example. in the aerospace and automotive brake pad industries. They are favored for use in high-end automotive transmissions but high costs have prevented widespread utilization.
Dense carbonlcarbon composite structures typically include a carbon fiber matrix, wherein the interstices in the fiber matrix are at least partially filled with deposited carbon. The carbon fibers are high in strength, and are typically in the form of a woven or nonwoven fabric or mat. In either case, the carbon fibers provide the composite with structural reinforcement.
To fill the carbon fabric with additional carbon, the fibers are typically placed in a chamber, where they are heated and exposed to a carbon-based vapor.
Carbon from the vapor is thereby deposited on the heated fabric via chemical vapor deposition.
In an alternative method for depositing carbon, the fiber fabric is placed in a chamber filled with liquid precursor (cyclohexane, for example), and the fibers are heated to pyrolize the liquid precursor at the surface of the fabric. The pyrolysis the precursor produces a vapor that deposits carbon on the fibers within the fabric.
This process is referred to as "rapid densification" and is described in greater detail in U.S. Patent 5,389,152, issued to Thurston et al.
Though the above-described methods are known to produce high-quality composite structures, the comrnercial application of these structures is limited by the high cost of carbon fibers, processing and energy consumption. Accordingly, the application of these methods to mass-production industries such as automobile manufacturing has thus far been greatly limited due to economic feasibility.
Further, due to the axially-elongated structure of the fibers, the composite properties are generally non-isotropic and highly dependent on fiber orientation.
SUMMARY OF THE INVENTION
The invention is generally directed to a method of forming a composite foam, the composite foam, and articles, such as clutch and brake components, formed of the composite foam.
In methods of this invention, a composite foam is formed by depositing one or several layers of a coating on an open-cell foam reticulated skeleton. The coatings may be metallic, ceramic, carbonaceous etc.
In accordance with one aspect of a method of the invention, the reticulated foam skeleton is contacted with a liquid precursor. The reticulated foam skeleton is heated to pyrolize the liquid precursor and cause a product of the pyrolized liquid precursor to deposit on the reticulated foam skeleton, thereby forming a composite foam of a higher density than the starting material. The sequence of material types that constitute the various layers may be varied.
In accordance with another aspect of a method of the invention, a reticulated carbon skeleton is formed by pyrolizing a polymeric foam. Carbon then is deposited on the carbon skeleton to form a carbon/carbon composite foam with a solid density of greater than 30%.
A carbon foam of this invention, which can be formed by the above-described methods, includes an open lattice of carbon ligaments that form a network of three-dimensionally interconnected cells and a pyrolytic carbon coating on the open lattice. The solid density of the carbon foam is greater than 30%.
BACKGROUND OF THE INVENTION
Relatively-dense carbon/carbon composites have been found to be highly useful in a variety of structural applications. Because of certain characteristics, such as high strength, high stiffness, light weight, high temperature resistance, and advantageous frictional properties, these composites are desirably suited for use, for example. in the aerospace and automotive brake pad industries. They are favored for use in high-end automotive transmissions but high costs have prevented widespread utilization.
Dense carbonlcarbon composite structures typically include a carbon fiber matrix, wherein the interstices in the fiber matrix are at least partially filled with deposited carbon. The carbon fibers are high in strength, and are typically in the form of a woven or nonwoven fabric or mat. In either case, the carbon fibers provide the composite with structural reinforcement.
To fill the carbon fabric with additional carbon, the fibers are typically placed in a chamber, where they are heated and exposed to a carbon-based vapor.
Carbon from the vapor is thereby deposited on the heated fabric via chemical vapor deposition.
In an alternative method for depositing carbon, the fiber fabric is placed in a chamber filled with liquid precursor (cyclohexane, for example), and the fibers are heated to pyrolize the liquid precursor at the surface of the fabric. The pyrolysis the precursor produces a vapor that deposits carbon on the fibers within the fabric.
This process is referred to as "rapid densification" and is described in greater detail in U.S. Patent 5,389,152, issued to Thurston et al.
Though the above-described methods are known to produce high-quality composite structures, the comrnercial application of these structures is limited by the high cost of carbon fibers, processing and energy consumption. Accordingly, the application of these methods to mass-production industries such as automobile manufacturing has thus far been greatly limited due to economic feasibility.
Further, due to the axially-elongated structure of the fibers, the composite properties are generally non-isotropic and highly dependent on fiber orientation.
SUMMARY OF THE INVENTION
The invention is generally directed to a method of forming a composite foam, the composite foam, and articles, such as clutch and brake components, formed of the composite foam.
In methods of this invention, a composite foam is formed by depositing one or several layers of a coating on an open-cell foam reticulated skeleton. The coatings may be metallic, ceramic, carbonaceous etc.
In accordance with one aspect of a method of the invention, the reticulated foam skeleton is contacted with a liquid precursor. The reticulated foam skeleton is heated to pyrolize the liquid precursor and cause a product of the pyrolized liquid precursor to deposit on the reticulated foam skeleton, thereby forming a composite foam of a higher density than the starting material. The sequence of material types that constitute the various layers may be varied.
In accordance with another aspect of a method of the invention, a reticulated carbon skeleton is formed by pyrolizing a polymeric foam. Carbon then is deposited on the carbon skeleton to form a carbon/carbon composite foam with a solid density of greater than 30%.
A carbon foam of this invention, which can be formed by the above-described methods, includes an open lattice of carbon ligaments that form a network of three-dimensionally interconnected cells and a pyrolytic carbon coating on the open lattice. The solid density of the carbon foam is greater than 30%.
Articles formed of the carbon foam include a clutch or brake device with a pair of members mounted for relative rotation and engagement. The carbon foam serves as a friction material that is rotatable with the members and includes confronting surfaces.
The methods and apparatus of this invention provide numerous advantages.
For example, the cost of carbon foam is generally lower than that of carbon fibers.
Therefore, methods of this invention can significantly reduce the cost of forming substantially-dense carbon/carbon composite foams. Accordingly, a broader range of applications can now be economically justified for use of carbon/carbon composites. Further, the resulting foams can have a substantially isotropic and openly-porous structure relative to that of many materials that employ fibers.
Because the composite is substantially isotropic, performance of a frictional surface comprising a foam of this invention is likely to be more uniform and consistent as the friction surface wears. The ceramic composite foams also have a relatively high permeability, thereby facilitating hydraulic flow in many wet-friction applications.
Moreover, distortion from machining is reduced due to the isotropic structure, thereby promoting flatness and parallelism in machined friction surfaces. The methods of this invention also can be used to produce exceptionally dense structures with over 50% solid density, while retaining open porosity.
Though a carbon skeleton generally has low strength relative to carbon fibers, the matrix that is deposited imparts sufficient structural integrity where the open porosity and isotropy of the carbon skeleton offer an excellent structure for wet frictional applications. The distribution of pores there through is substantially uniform and provide an interlaced network of conduits through which hydraulic fluid can flow. Further, the nature of this structure also enables extremely high densification levels (e.g., up to 90%), while retaining interconnected pores throughout the structure. The lack of strength in the carbon skeleton is made up for by the pyrolytic carbon or other deposit which provides the foam with the structural reinforcement that is needed for applications such as wet friction.
The methods and apparatus of this invention provide numerous advantages.
For example, the cost of carbon foam is generally lower than that of carbon fibers.
Therefore, methods of this invention can significantly reduce the cost of forming substantially-dense carbon/carbon composite foams. Accordingly, a broader range of applications can now be economically justified for use of carbon/carbon composites. Further, the resulting foams can have a substantially isotropic and openly-porous structure relative to that of many materials that employ fibers.
Because the composite is substantially isotropic, performance of a frictional surface comprising a foam of this invention is likely to be more uniform and consistent as the friction surface wears. The ceramic composite foams also have a relatively high permeability, thereby facilitating hydraulic flow in many wet-friction applications.
Moreover, distortion from machining is reduced due to the isotropic structure, thereby promoting flatness and parallelism in machined friction surfaces. The methods of this invention also can be used to produce exceptionally dense structures with over 50% solid density, while retaining open porosity.
Though a carbon skeleton generally has low strength relative to carbon fibers, the matrix that is deposited imparts sufficient structural integrity where the open porosity and isotropy of the carbon skeleton offer an excellent structure for wet frictional applications. The distribution of pores there through is substantially uniform and provide an interlaced network of conduits through which hydraulic fluid can flow. Further, the nature of this structure also enables extremely high densification levels (e.g., up to 90%), while retaining interconnected pores throughout the structure. The lack of strength in the carbon skeleton is made up for by the pyrolytic carbon or other deposit which provides the foam with the structural reinforcement that is needed for applications such as wet friction.
BRIEF DESCRIPTION OF THE DRAWING
The Figure is a partially-schematic cut-away drawing of a reactor suitable for densifying a ceramic foam by the method of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The features and other details of the method of the invention will now be more particularly described with reference to the accompanying drawing and pointed out in the claims. It will be understood that the particular embodiments of the invention are shown by way of illustration and not as limitations of the invention.
The principal features of this invention can be employed in various embodiments without departing from the scope of the invention.
In a method of this invention, a densified composite foam is formed by depositing a coating on an open-cell reticulated foam skeleton.
In one embodiment of the method, the foam skeleton comprises carbon in the form of an open lattice of ligaments, wherein the interconnected pores defined by the lattice have diameters of about 0.5 to about 1.0 mm. The lattice has a micrographic porosity of about 100 pores per inch, a bulk density of about 0.04 g/cm3, and a surface area of about 1.6 m2/g. In an alternate embodiment, the lattice has a micrographic porosity of about 60 pores per inch. The foam skeleton is formed by pyrolizing a polymeric foam. The polymeric foam is formed from a therrrmosetting polymer foam preform of for example, a polyurethane, phenolic or polyimide.
The polymer foam is in the form of an open lattice of ligaments forming a network of three-dimensionally interconnected cells. In comparison to carbon fibers, the polymer foam is relatively easy to shape into the desired form.
The polymer foam is liquid infiltrated with a carbon-bearing resin and pyrolized at approximately 600 to 1200 C in a vacuum or in an inert or reducing atmosphere to form an all-carbon reticulated foam skeleton. The carbon foam skeleton has an essentially amorphous structure in the form of the polymer foam preform. As an alternative to pyrolizing a polymer foam to form the carbon foam skeleton, the carbon foam skeleton can be purchased commercially from Ultramet (Pacoima, California, USA) or from Vitre-Cell, Inc. (Essexville, Michigan, USA).
The Figure is a partially-schematic cut-away drawing of a reactor suitable for densifying a ceramic foam by the method of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The features and other details of the method of the invention will now be more particularly described with reference to the accompanying drawing and pointed out in the claims. It will be understood that the particular embodiments of the invention are shown by way of illustration and not as limitations of the invention.
The principal features of this invention can be employed in various embodiments without departing from the scope of the invention.
In a method of this invention, a densified composite foam is formed by depositing a coating on an open-cell reticulated foam skeleton.
In one embodiment of the method, the foam skeleton comprises carbon in the form of an open lattice of ligaments, wherein the interconnected pores defined by the lattice have diameters of about 0.5 to about 1.0 mm. The lattice has a micrographic porosity of about 100 pores per inch, a bulk density of about 0.04 g/cm3, and a surface area of about 1.6 m2/g. In an alternate embodiment, the lattice has a micrographic porosity of about 60 pores per inch. The foam skeleton is formed by pyrolizing a polymeric foam. The polymeric foam is formed from a therrrmosetting polymer foam preform of for example, a polyurethane, phenolic or polyimide.
The polymer foam is in the form of an open lattice of ligaments forming a network of three-dimensionally interconnected cells. In comparison to carbon fibers, the polymer foam is relatively easy to shape into the desired form.
The polymer foam is liquid infiltrated with a carbon-bearing resin and pyrolized at approximately 600 to 1200 C in a vacuum or in an inert or reducing atmosphere to form an all-carbon reticulated foam skeleton. The carbon foam skeleton has an essentially amorphous structure in the form of the polymer foam preform. As an alternative to pyrolizing a polymer foam to form the carbon foam skeleton, the carbon foam skeleton can be purchased commercially from Ultramet (Pacoima, California, USA) or from Vitre-Cell, Inc. (Essexville, Michigan, USA).
As an alternative to the amorphous carbon skeletons, described above, a crystalline foam skeleton can also be used. For example, a microcellular graphitic foam is formed by pyrolysis and graphitization of thermoplastic carbon-fiber precursor materials such as polyacrylonitrile (PAN) or mesophase pitch. The foaming process aligns the graphitic planes along each ligament axis, resulting in higher strength and stiffness. These foams may be available from, for example, Wright Materials Research Co. (Dayton, Ohio, USA).
The carbon skeleton is then coated, in this embodiment, with pyrolytic carbon or graphite to increase the density of the foam and to increase its strength to thereby make it suitable for use, for example, in wet friction applications. In one specific method, the carbon skeleton is coated with pyrolytic carbon via a process known as "rapid densification." In this example, the carbon skeleton is immersed in a liquid precursor and heated. The heat of the carbon skeleton pyrolizes the liquid precursor, thereby generating gaseous products which deposit carbon on the skeleton upon contact to form a coating. The specifics of the rapid densification process and the equipment used to perform it will now be described in greater detail and with reference to the Figure, below.
An example of apparatus suitable for practicing the method of the invention is shown in the Figure. General descriptions of operation of the apparatus are set forth in U.S. Patent 5,389,152, issued to Thurston et al. on February 14,1995 and in U.S.
Patent 4,472,454, issued to Houdayer et al. on September 18,1984. Reactor 100 is described in U.S. Patent 5,397,595, issued to Carroll et al. on March 14,1995 and in U. S. Patent 5,547,717, issued to Scaringella et al. on August 20,1996. When an induction coil 104 is used to heat the skeleton, reactor 100 is preferably made from non-magnetic materials, such as aluminum, quartz, glass, stainless steel, ceramic or combinations thereof.
As shown in the Figure, reactor 100 defines cavity 102 in which one or more carbon foam skeletons (not shown) are densified to form composite foams in accordance with the methods of this invention. In operation, cavity 102 is filled with a liquid precursor sufficient to at least cover the skeleton. The liquid precursor is a liquid which vaporizes and decomposes within the skeleton to deposit a decomposition product of the precursor at a temperature to which the skeleton can be heated. Depending upon the composition of the liquid precursor, the decomposition product can be carbon, silicon carbide, silicon nitride, or another material. The liquid precursor should also be a dielectric. Preferably, the dielectric constant of the liquid precursor should be above 0.5, more preferably above one, and most preferably above 1.5. To deposit carbon within the foam, a hydrocarbon with an appropriate boiling point, such as cyclohexane, n-hexane or benzene is used.
Alternatively, methyltrichlorosilane, dimethyldichlorosilane, methyldichlorosilane or other organosilane or organosilane mixtures are used to deposit silicon carbide.
Also, the liquid precursor can be chosen to co-deposit materials. For example, a mixture of silicon carbide and silicon nitride can be deposited using tris-n-methyl amino silane or other silane compound.
One or more induction coils 104 are positioned within cavity 102, and the carbon foam skeleton is submerged in the liquid precursor in close proximity to induction coil 104. In a specific embodiment, the foam skeleton is placed in a support fixture to firmly hold the skeleton at a fixed position in relation to reactor 100 and coil 104. The exact shape of the fixture is adapted to the shape of the skeleton. Such a fixture can be supported in any convenient way, such as on lip 132. Further, the size and shape of coil 104 preferably conform to the size and shape of the carbon skeleton. Induction coil 104 can be formed from copper or other highly conductive material which does not react with the liquid precursor even if heated. In one embodiment, induction coil 104 is a Litzwire coil. In contrast to a standard single-strand coil, a Litzwire coil has an appearance similar to a telephone cable; i.e., a Litzwire coil comprises a bundle of insulated wires wound together to provide more efficient inductive coupling.
Induction coil 104 is connected to busses 106 at connector 134. Connector 134 provides a link in an electrical circuit defined, in part, by busses 106.
It also provides a link in the water flow circuit formed by channels 105. In particular embodiments, connector 134 is a block of metal allowing anchoring points for screws (not shown) to hold the base of induction coil 104 to busses 106. The joints in the water flow circuit can be sealed by flexible "0" rings or in some other convenient fashion. The material should be resistant to degradation in both water and the liquid precursor. Viton` fluoroelastomer from E.I. DuPont de Nemours &
Co. or silicone rubber can be used for this purpose. Other attachment arrangements, such as slots and grooves or clips, can also be used.
Busses 106 supply electrical energy to induction coil 104 and are made of a highly conductive material, such as copper. Currents on the order of hundreds of amperes to thousands of amperes are preferably used to provide sufficient power to heat the foam. Because of the large amount of current, busses 106 should have sufficient cross sections to avoid excess heating. Busses 106 can contain water passages 105 to carry cooling water through busses 106 and through induction coil 104.
In an alternative embodiment, busses 106 are connected to a heated mandrel, rather than to induction coil 104. The mandrel is then inserted through a foam tube which is to be the subject of rapid densification. The mandrel is formed principally of carbon and may include a release agent, such as boron nitride on its surface. In one embodiment, the mandrel is used as a susceptor and is inductively heated to generate heat which is conducted into the carbon foam. Alternatively, the mandrel is physically coupled with a voltage source and is subject to resistive heating to generate heat to be transferred to the carbon foam. Indeed, the substrate can be heated directly by resistance heating provided that the geometry is conducive to uniform heating.
Busses 106 enter the chamber through a silicone rubber seal 107. Busses 106 are connected to an AC power supply (not shown). The voltage, current, frequency and shape of induction coil 104 are determined by the shape, geometry and the electrical properties of the foam using known techniques.
As will be explained more fully, below, the rapid densification process, described herein, heats the foam to higher temperatures at its center than at its periphery. Typically, the initial power provided by the AC power supply is at a level that inductively heats the foam to generate a temperature at the center of the foam that is high enough to pyrolize the precursor and deposit a decomposition product, without heating more peripheral regions beyond relatively-low temperatures at which deposition is limited. In contrast, if the power, and the consequent rate of deposition, is too high, the interior of the foam can be sealed off by the deposition and build-up of decomposition product in peripheral areas, thereby resulting in non-uniform densification. Accordingly, the current level, in specific embodiments of this method, is on the order of thousands of amperes, though the precise level will depend on the foam's cross-sectional area. At the densification center, which is not necessarily, but is typically, at the center of the foam, the temperature is typically in the range of between about 850 and about 2,000 C.
The preferred temperature is in the range of between about 850 and about 1,000 C.
The dynamics of deposition by way of the above-described method differs significantly from that of CVD. Whereas CVD deposits a decomposition product throughout the preform during densification, the above-described method results in a densification profile that typically begins at the center of the preform and progresses to the surfaces. It is believed that this profile exists because the liquid precursor, and the boiling thereof, acts to cool the exterior of the foam, thereby creating a temperature gradient through the foam's thickness. Accordingly, the temperature gradient is such that the densification center of the foam is hotter than the surface.
Because the rate of deposition increases with increasing temperature, densification proceeds from the center to the surface as the temperature of the foam is increased.
Further, as deposition of the decomposition product proceeds, the conductivity of the foam increases, improving the coupling with the electric field.
Consequently, less current is needed to heat the foam, and the foam can be processed using a modified heating cycle in which the final power is decreased by about twenty-five percent from the power required to densify out to the edges of the foam.
Returning to the Figure, the liquid precursor that is to be pyrolized and deposited within the foam is supplied to reactor 100 through precursor input 108 via valve 110. Initially, chamber 102 is filled with a liquid precursor of sufficient quantity to cover the foam. In operation, the liquid precursor can be consumed in the deposition reaction or can escape from reactor 100 as vapor. Accordingly, precursor input 108 can be utilized during operation of reactor 100 to replace liquid precursor which is dissipated.
The carbon skeleton is then coated, in this embodiment, with pyrolytic carbon or graphite to increase the density of the foam and to increase its strength to thereby make it suitable for use, for example, in wet friction applications. In one specific method, the carbon skeleton is coated with pyrolytic carbon via a process known as "rapid densification." In this example, the carbon skeleton is immersed in a liquid precursor and heated. The heat of the carbon skeleton pyrolizes the liquid precursor, thereby generating gaseous products which deposit carbon on the skeleton upon contact to form a coating. The specifics of the rapid densification process and the equipment used to perform it will now be described in greater detail and with reference to the Figure, below.
An example of apparatus suitable for practicing the method of the invention is shown in the Figure. General descriptions of operation of the apparatus are set forth in U.S. Patent 5,389,152, issued to Thurston et al. on February 14,1995 and in U.S.
Patent 4,472,454, issued to Houdayer et al. on September 18,1984. Reactor 100 is described in U.S. Patent 5,397,595, issued to Carroll et al. on March 14,1995 and in U. S. Patent 5,547,717, issued to Scaringella et al. on August 20,1996. When an induction coil 104 is used to heat the skeleton, reactor 100 is preferably made from non-magnetic materials, such as aluminum, quartz, glass, stainless steel, ceramic or combinations thereof.
As shown in the Figure, reactor 100 defines cavity 102 in which one or more carbon foam skeletons (not shown) are densified to form composite foams in accordance with the methods of this invention. In operation, cavity 102 is filled with a liquid precursor sufficient to at least cover the skeleton. The liquid precursor is a liquid which vaporizes and decomposes within the skeleton to deposit a decomposition product of the precursor at a temperature to which the skeleton can be heated. Depending upon the composition of the liquid precursor, the decomposition product can be carbon, silicon carbide, silicon nitride, or another material. The liquid precursor should also be a dielectric. Preferably, the dielectric constant of the liquid precursor should be above 0.5, more preferably above one, and most preferably above 1.5. To deposit carbon within the foam, a hydrocarbon with an appropriate boiling point, such as cyclohexane, n-hexane or benzene is used.
Alternatively, methyltrichlorosilane, dimethyldichlorosilane, methyldichlorosilane or other organosilane or organosilane mixtures are used to deposit silicon carbide.
Also, the liquid precursor can be chosen to co-deposit materials. For example, a mixture of silicon carbide and silicon nitride can be deposited using tris-n-methyl amino silane or other silane compound.
One or more induction coils 104 are positioned within cavity 102, and the carbon foam skeleton is submerged in the liquid precursor in close proximity to induction coil 104. In a specific embodiment, the foam skeleton is placed in a support fixture to firmly hold the skeleton at a fixed position in relation to reactor 100 and coil 104. The exact shape of the fixture is adapted to the shape of the skeleton. Such a fixture can be supported in any convenient way, such as on lip 132. Further, the size and shape of coil 104 preferably conform to the size and shape of the carbon skeleton. Induction coil 104 can be formed from copper or other highly conductive material which does not react with the liquid precursor even if heated. In one embodiment, induction coil 104 is a Litzwire coil. In contrast to a standard single-strand coil, a Litzwire coil has an appearance similar to a telephone cable; i.e., a Litzwire coil comprises a bundle of insulated wires wound together to provide more efficient inductive coupling.
Induction coil 104 is connected to busses 106 at connector 134. Connector 134 provides a link in an electrical circuit defined, in part, by busses 106.
It also provides a link in the water flow circuit formed by channels 105. In particular embodiments, connector 134 is a block of metal allowing anchoring points for screws (not shown) to hold the base of induction coil 104 to busses 106. The joints in the water flow circuit can be sealed by flexible "0" rings or in some other convenient fashion. The material should be resistant to degradation in both water and the liquid precursor. Viton` fluoroelastomer from E.I. DuPont de Nemours &
Co. or silicone rubber can be used for this purpose. Other attachment arrangements, such as slots and grooves or clips, can also be used.
Busses 106 supply electrical energy to induction coil 104 and are made of a highly conductive material, such as copper. Currents on the order of hundreds of amperes to thousands of amperes are preferably used to provide sufficient power to heat the foam. Because of the large amount of current, busses 106 should have sufficient cross sections to avoid excess heating. Busses 106 can contain water passages 105 to carry cooling water through busses 106 and through induction coil 104.
In an alternative embodiment, busses 106 are connected to a heated mandrel, rather than to induction coil 104. The mandrel is then inserted through a foam tube which is to be the subject of rapid densification. The mandrel is formed principally of carbon and may include a release agent, such as boron nitride on its surface. In one embodiment, the mandrel is used as a susceptor and is inductively heated to generate heat which is conducted into the carbon foam. Alternatively, the mandrel is physically coupled with a voltage source and is subject to resistive heating to generate heat to be transferred to the carbon foam. Indeed, the substrate can be heated directly by resistance heating provided that the geometry is conducive to uniform heating.
Busses 106 enter the chamber through a silicone rubber seal 107. Busses 106 are connected to an AC power supply (not shown). The voltage, current, frequency and shape of induction coil 104 are determined by the shape, geometry and the electrical properties of the foam using known techniques.
As will be explained more fully, below, the rapid densification process, described herein, heats the foam to higher temperatures at its center than at its periphery. Typically, the initial power provided by the AC power supply is at a level that inductively heats the foam to generate a temperature at the center of the foam that is high enough to pyrolize the precursor and deposit a decomposition product, without heating more peripheral regions beyond relatively-low temperatures at which deposition is limited. In contrast, if the power, and the consequent rate of deposition, is too high, the interior of the foam can be sealed off by the deposition and build-up of decomposition product in peripheral areas, thereby resulting in non-uniform densification. Accordingly, the current level, in specific embodiments of this method, is on the order of thousands of amperes, though the precise level will depend on the foam's cross-sectional area. At the densification center, which is not necessarily, but is typically, at the center of the foam, the temperature is typically in the range of between about 850 and about 2,000 C.
The preferred temperature is in the range of between about 850 and about 1,000 C.
The dynamics of deposition by way of the above-described method differs significantly from that of CVD. Whereas CVD deposits a decomposition product throughout the preform during densification, the above-described method results in a densification profile that typically begins at the center of the preform and progresses to the surfaces. It is believed that this profile exists because the liquid precursor, and the boiling thereof, acts to cool the exterior of the foam, thereby creating a temperature gradient through the foam's thickness. Accordingly, the temperature gradient is such that the densification center of the foam is hotter than the surface.
Because the rate of deposition increases with increasing temperature, densification proceeds from the center to the surface as the temperature of the foam is increased.
Further, as deposition of the decomposition product proceeds, the conductivity of the foam increases, improving the coupling with the electric field.
Consequently, less current is needed to heat the foam, and the foam can be processed using a modified heating cycle in which the final power is decreased by about twenty-five percent from the power required to densify out to the edges of the foam.
Returning to the Figure, the liquid precursor that is to be pyrolized and deposited within the foam is supplied to reactor 100 through precursor input 108 via valve 110. Initially, chamber 102 is filled with a liquid precursor of sufficient quantity to cover the foam. In operation, the liquid precursor can be consumed in the deposition reaction or can escape from reactor 100 as vapor. Accordingly, precursor input 108 can be utilized during operation of reactor 100 to replace liquid precursor which is dissipated.
During densification, the liquid precursor can become clouded. In that case, valve 114 is opened to allow liquid precursor to flow through reactor 100 and return 112 to filter 116 where it is filtered and pumped back into reactor 100.
Filter 116 can be any suitable filter, such as a porous ceramic screen or, more preferably, charcoal. Alternatively, the liquid precursor is removed from reactor 100 and is then distilled after one or more densification cycles once the liquid precursor becomes clouded.
The liquid precursors, as used herein, are potentially flammable.
Accordingly, the densification operation is preferably performed in an inert atmosphere. For example, nitrogen gas can be used. To purge chamber 102 of air, valve 120 is opened to allow an inert gas, such as nitrogen, to flow through input 118. Valve 124 can be opened to more rapidly and effectively purge vapor recovery system 130. Once the atmosphere in chamber 102 is replaced by an inert gas, such as nitrogen gas, valve 128 can be opened to provide nitrogen directly into vent stack 136. This flow of nitrogen prevents air from reaching chamber 102 and valves and 124 can be closed. Closing valves 120 and 124 reduces the flow of gas through vapor recovery system 130. Vapor recovery system 130 can therefore operate more efficiently.
Vapor recovery system 130 is a system of the type known in the art for recovering vaporized liquids. Such a system reduces the amount of waste generated in the process and the amount of precursor used. Further, vapor recovery system 130 prevents the loss of a significant volume of the liquid precursor due to vaporization.
Specific embodiments of the method of this invention include the additional step of performing CVD prior to rapid densification to preliminarily increase the density of the foam and to increase the initial rate of densification during the rapid densification process.
In another optional step, CVD can be performed after a composite foam has been densified by the above-described methods. In some circumstances, the above-described methods can produce a foam that has a greater density at its interior than at its periphery. In these situations, CVD can then be used to complete densification and to provide the foam with a more uniform density by preferentially building the deposited coating near the surface of the foam.
In regard to the product of this invention, a carbon foam of this invention includes an open lattice of carbon ligaments forming a network of three-dimensional interconnected cells. The open lattice is coated with a crystallized carbon coating to produce a foam with a solid density greater than 30%.
In specific embodiments, the carbon/carbon foam composite of this invention is formed by the above-disclosed methods. Its structure is essentially isotropic, at least on a macroscopic scale. When designed for wet friction applications, the composite structure preferably has a solid density of at least about 40%.
Further, for some applications, the composite structure is subjected to rapid densification until a solid density of at least about 50% is obtained. Further still, with extended densification, openly-porous foam structures of 67%, 76% and 82% density have been obtained. The porosity can be controlled by varying the pore size and/or distribution of the polymer foam preform or by varying the deposition conditions.
In specific embodiments, the composite foam defines a structure of interconnecting pores that allow hydraulic fluid to flow through the foam.
Accordingly, the foam can be cast in an appropriate shape and sufficiently densified to form a composite for use as a wet-friction material in a clutch or brake, e.g., in an automobile, where the composites are mounted opposite one another for relative rotation and frictional engagement.
Moreover, fully or nearly-fully dense structures can be formed for use in structural applications such as aircraft brakes, automobile pistons, missile nose cones, susceptor/crucible cradles for crystal pulling, and low-coefficient-of-thermal-expansion space structures.
In additional embodiments, the composite foam is subjected to post-densification treatments, including surface coatings for improved oxidation resistance, resin infiltration, or localized hardening by filling (e.g., by painting or wicking) pores with various matrix materials. The surfaces of partially-densified foam can also be sealed over by spiking the temperatures at the end of RD
processing to yield stiff, lightweight, porous structures having solid surfaces.
Filter 116 can be any suitable filter, such as a porous ceramic screen or, more preferably, charcoal. Alternatively, the liquid precursor is removed from reactor 100 and is then distilled after one or more densification cycles once the liquid precursor becomes clouded.
The liquid precursors, as used herein, are potentially flammable.
Accordingly, the densification operation is preferably performed in an inert atmosphere. For example, nitrogen gas can be used. To purge chamber 102 of air, valve 120 is opened to allow an inert gas, such as nitrogen, to flow through input 118. Valve 124 can be opened to more rapidly and effectively purge vapor recovery system 130. Once the atmosphere in chamber 102 is replaced by an inert gas, such as nitrogen gas, valve 128 can be opened to provide nitrogen directly into vent stack 136. This flow of nitrogen prevents air from reaching chamber 102 and valves and 124 can be closed. Closing valves 120 and 124 reduces the flow of gas through vapor recovery system 130. Vapor recovery system 130 can therefore operate more efficiently.
Vapor recovery system 130 is a system of the type known in the art for recovering vaporized liquids. Such a system reduces the amount of waste generated in the process and the amount of precursor used. Further, vapor recovery system 130 prevents the loss of a significant volume of the liquid precursor due to vaporization.
Specific embodiments of the method of this invention include the additional step of performing CVD prior to rapid densification to preliminarily increase the density of the foam and to increase the initial rate of densification during the rapid densification process.
In another optional step, CVD can be performed after a composite foam has been densified by the above-described methods. In some circumstances, the above-described methods can produce a foam that has a greater density at its interior than at its periphery. In these situations, CVD can then be used to complete densification and to provide the foam with a more uniform density by preferentially building the deposited coating near the surface of the foam.
In regard to the product of this invention, a carbon foam of this invention includes an open lattice of carbon ligaments forming a network of three-dimensional interconnected cells. The open lattice is coated with a crystallized carbon coating to produce a foam with a solid density greater than 30%.
In specific embodiments, the carbon/carbon foam composite of this invention is formed by the above-disclosed methods. Its structure is essentially isotropic, at least on a macroscopic scale. When designed for wet friction applications, the composite structure preferably has a solid density of at least about 40%.
Further, for some applications, the composite structure is subjected to rapid densification until a solid density of at least about 50% is obtained. Further still, with extended densification, openly-porous foam structures of 67%, 76% and 82% density have been obtained. The porosity can be controlled by varying the pore size and/or distribution of the polymer foam preform or by varying the deposition conditions.
In specific embodiments, the composite foam defines a structure of interconnecting pores that allow hydraulic fluid to flow through the foam.
Accordingly, the foam can be cast in an appropriate shape and sufficiently densified to form a composite for use as a wet-friction material in a clutch or brake, e.g., in an automobile, where the composites are mounted opposite one another for relative rotation and frictional engagement.
Moreover, fully or nearly-fully dense structures can be formed for use in structural applications such as aircraft brakes, automobile pistons, missile nose cones, susceptor/crucible cradles for crystal pulling, and low-coefficient-of-thermal-expansion space structures.
In additional embodiments, the composite foam is subjected to post-densification treatments, including surface coatings for improved oxidation resistance, resin infiltration, or localized hardening by filling (e.g., by painting or wicking) pores with various matrix materials. The surfaces of partially-densified foam can also be sealed over by spiking the temperatures at the end of RD
processing to yield stiff, lightweight, porous structures having solid surfaces.
EQUIVALENTS
While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (78)
1. A method for forming a densified composite foam, comprising the steps of:
a) immersing a reticulated foam skeleton in a liquid precursor; and b) heating the immersed reticulated foam skeleton to pyrolize the liquid precursor and cause a product of the pyrolized liquid precursor to deposit on the reticulated foam skeleton thereby forming the densified composite foam.
a) immersing a reticulated foam skeleton in a liquid precursor; and b) heating the immersed reticulated foam skeleton to pyrolize the liquid precursor and cause a product of the pyrolized liquid precursor to deposit on the reticulated foam skeleton thereby forming the densified composite foam.
2. The method of claim 1, wherein the reticulated foam skeleton includes carbon.
3. The method of claim 2, further comprising the step of pyrolizing a polymeric foam to form the reticulated foam skeleton.
4. The method of claim 3, wherein the polymeric foam includes a thermosetting polymer selected from the group consisting of polyurethanes, phenolics, and polyimides.
5. The method of claim 3, further comprising the step of using chemical vapor deposition to deposit a coating on the reticulated foam skeleton before the reticulated foam skeleton is immersed in the liquid precursor.
6. The method of claim 5, wherein the deposited coating includes carbon.
7. The method of claim 3, further comprising the step of using chemical vapor deposition to deposit a coating on the densified composite foam after the liquid precursor is pyrolized and deposited on the reticulated foam skeleton.
8. The method of claim 1, wherein the product of the pyrolyzed liquid precursor is any one of carbon, silicon carbide, and silicon nitride.
9. The method of claim 1, wherein the liquid precursor is a dielectric.
10. The method of claim 9, wherein the dielectric constant of the liquid precursor is at least 0.5.
11. The method of claim 1, wherein the liquid precursor is any one of cyclohexane, n-hexane, benzene, methyltrichlorosilane, dimethyldichlorosilane, methyldichlorosilane, and tris-n-methyl amino silane.
12. The method of claim 1, wherein heating the immersed reticulated foam skeleton comprises heating the immersed reticulated foam skeleton using an induction coil immersed in the liquid precursor.
13. The method of claim 1, wherein the reticulated foam skeleton is carbon and the product of the pyrolyzed liquid precursor is carbon, the resulting carbon-carbon composite foam having greater than 30% solid density.
14. The method of claim 13, wherein the carbon-carbon composite foam has a solid density of at least 40%.
15. The method of claim 13, wherein the carbon-carbon composite foam has a solid density of at least 50%.
16. The method of claim 13, wherein the carbon-carbon composite foam has an essentially isotropic structure.
17. The method of claim 1, wherein pores in the foam being about 500 to about 1000 microns in diameter.
18. The method of claim 1, wherein micrographic porosity of about 60 to about 100 pores/inch.
19. The method of claim 1, wherein bulk density of about 0.04 g/cm3.
20. The method of claim 1, wherein surface area of about 1.6 m2/g.
21. A method for forming a carbon-carbon composite foam, comprising the steps of:
a) pyrolizing a polymeric foam to form a reticulated carbon skeleton; and b) depositing pyrolytic carbon on the reticulated carbon skeleton to form a carbon-carbon composite foam with greater than 30% solid density.
a) pyrolizing a polymeric foam to form a reticulated carbon skeleton; and b) depositing pyrolytic carbon on the reticulated carbon skeleton to form a carbon-carbon composite foam with greater than 30% solid density.
22. The method of claim 21, wherein the polymeric foam includes a thermosetting polymer selected from the group consisting of polyurethanes, phenolics, and polyimides.
23. The method of claim 21, wherein the carbon-carbon composite foam is densified to a solid density of at least about 40%.
24. The method of claim 21, wherein the carbon-carbon composite foam is densified to a solid density of at least about 50%.
25. The method of claim 21, wherein pores in the foam being about 500 to about 1000 microns in diameter.
26. The method of claim 21, wherein micrographic porosity of about 60 to about 100 pores/inch.
27. The method of claim 21, wherein bulk density of about 0.04 g/cm3.
28. The method of claim 21, wherein surface area of about 1.6 m2/g.
29. A method for forming a densified composite foam, comprising the steps of:
a) pyrolizing a polymeric foam to form a reticulated foam skeleton;
b) depositing a coating on the reticulated foam skeleton by chemical vapor deposition to form a coated reticulated foam skeleton;
c) immersing the coated reticulated foam skeleton in a liquid precursor; and d) heating the immersed reticulated foam skeleton to pyrolize the liquid precursor and cause a product of the pyrolized liquid precursor to deposit on the reticulated foam skeleton thereby forming the densified composite foam.
a) pyrolizing a polymeric foam to form a reticulated foam skeleton;
b) depositing a coating on the reticulated foam skeleton by chemical vapor deposition to form a coated reticulated foam skeleton;
c) immersing the coated reticulated foam skeleton in a liquid precursor; and d) heating the immersed reticulated foam skeleton to pyrolize the liquid precursor and cause a product of the pyrolized liquid precursor to deposit on the reticulated foam skeleton thereby forming the densified composite foam.
30. The method of claim 29, wherein pores in the foam being about 500 to about 1000 microns in diameter.
31. The method of claim 29, wherein micrographic porosity of about 60 to about 100 pores/inch.
32. The method of claim 29, wherein bulk density of about 0.04 g/cm3.
33. The method of claim 29, wherein surface area of about 1.6 m2/g.
34. A carbon-carbon composite foam, having a structure of interconnecting pores that allow fluid to flow through the carbon-carbon composite foam, the carbon-carbon composite foam comprising:
a) an open lattice of carbon ligaments forming a network of three-dimensionally interconnected cells; and b) a pyrolytic carbon coating formed on the open lattice of carbon ligaments, wherein the carbon-carbon composite foam has a solid density of greater than 30%.
a) an open lattice of carbon ligaments forming a network of three-dimensionally interconnected cells; and b) a pyrolytic carbon coating formed on the open lattice of carbon ligaments, wherein the carbon-carbon composite foam has a solid density of greater than 30%.
35. The carbon-carbon composite foam of claim 34, wherein the carbon-carbon composite foam has an essentially isotropic structure.
36. The carbon-carbon composite foam of claim 34, wherein the open lattice of carbon ligaments comprises one of amorphous carbon or crystalline carbon.
37. The carbon-carbon composite foam of claim 34, wherein the carbon-carbon composite foam has a solid density of at least about 40%.
38. The carbon-carbon composite foam of claim 34, wherein the carbon-carbon composite foam has a solid density of at least about 50%.
39. The carbon-carbon composite foam of claim 34, wherein the foam is a pyrolysis product of a thermosetting polymer selected from the group consisting of polyurethanes, phenolics, and polyimides.
40. The carbon-carbon composite foam of claim 34, wherein the pyrolytic carbon coating is deposited by the thermal decomposition of a liquid precursor.
41. The carbon-carbon composite foam of claim 34, comprising a ceramic coating comprising at least one of silicon carbide and silicon nitride.
42. The carbon-carbon composite foam of claim 41, wherein the ceramic coating is deposited by the thermal decomposition of a liquid precursor selected from the group consisting essentially of methyltrichlorosilane, dimethyldichlorosilane, methyldichlorosilane, and ti-is-n-methyl amino silane.
43. The carbon-carbon composite foam of claim 34, wherein the pyrolytic carbon coating is a dielectric.
44. The carbon-carbon composite foam of claim 43, wherein the pyrolytic carbon coating has a dielectric constant of at least 0.5.
45. The carbon-carbon composite of claim 34, further including a chemical vapor deposition coating deposited on the pyrolytic carbon coating.
46. The carbon-carbon foam of claim 34, wherein said foam includes pores being in the range of between about 500 and about 1,000 microns in diameter.
47. The carbon-carbon foam of claim 34, wherein said foam includes micrographic porosity in the range of between about 60 and about 100 pores/inch.
48. The carbon-carbon foam of claim 34, wherein said foam includes a bulk density of about 0.04 g/cm3.
49. The carbon-carbon foam of claim 34, wherein said foam includes a surface area density of about 1.6 m2/g.
50. The carbon-carbon composite foam of claim 34, wherein the carbon-carbon composite foam has a solid density of at least about 67%.
51. The carbon-carbon composite foam of claim 34, wherein the carbon-carbon composite foam has a solid density of at least about 76%.
52. The carbon-carbon composite foam of claim 34, wherein the carbon-carbon composite foam has a solid density of at least about 82%.
53. The carbon-carbon composite foam of claim 34, wherein the pyrolytic carbon coating is deposited by the thermal decomposition of a liquid precursor selected from a group consisting of cyclohexane, n-hexane, and benzene.
54. A carbon-carbon composite foam, comprising:
a) an open lattice of carbon ligaments forming a network of three-dimensionally interconnected cells; and b) a pyrolytic carbon coating on the open lattice of carbon ligaments, wherein an interior portion of the carbon-carbon composite foam has a solid density that is greater than the solid density of a peripheral portion of the composite foam.
a) an open lattice of carbon ligaments forming a network of three-dimensionally interconnected cells; and b) a pyrolytic carbon coating on the open lattice of carbon ligaments, wherein an interior portion of the carbon-carbon composite foam has a solid density that is greater than the solid density of a peripheral portion of the composite foam.
55. The carbon-carbon composite foam of claim 54, wherein the carbon-carbon composite foam defines a structure of interconnecting pores that allow hydraulic fluid to flow through the carbon-carbon composite foam.
56. The carbon-carbon composite foam of claim 54, wherein the open lattice of carbon ligaments comprises one of amorphous carbon or crystalline carbon.
57. The carbon-carbon composite foam of claim 54, wherein the carbon-carbon composite foam has a solid density of at least about 40%.
58. The carbon-carbon composite foam of claim 54, wherein the carbon-carbon composite foam has a solid density of at least about 50%.
59. The carbon-carbon composite foam of claim 54, wherein the foam is a pyrolytic product of a thermosetting polymer selected from the group consisting of polyurethanes, phenolics, and polyimides.
60. The carbon-carbon composite foam of claim 54, wherein the pyrolytic carbon coating is deposited by the thermal decomposition of a liquid precursor.
61. The carbon-carbon composite foam of claim 54, comprising a ceramic coating comprising at least one of silicon carbide and silicon nitride.
62. The carbon-carbon composite foam of claim 61, wherein the ceramic coating is deposited by the thermal decomposition of a liquid precursor selected from the group consisting essentially of methyltrichlorosilane, dimethyldichlorosilane, methyldichlorosilane, and tris-n-methyl amino silane.
63. The carbon-carbon composite foam of claim 54, wherein the pyrolytic carbon coating is a dielectric.
64. The carbon-carbon composite foam of claim 63, wherein the pyrolytic carbon coating has a dielectric constant of at least 0.5.
65. The carbon-carbon composite of claim 54, further including a chemical vapor deposition coating deposited on the pyrolytic carbon coating.
66. The carbon-carbon foam of claim 54, wherein said foam includes pores being in the range of between about 500 and about 1,000 microns in diameter.
67. The carbon-carbon foam of claim 54, wherein said foam includes micrographic porosity in the range of between about 60 and about 100 pores/inch.
68. The carbon-carbon foam of claim 54, wherein said foam includes a bulk density of about 0.04 g/cm3.
69. The carbon-carbon foam of claim 54, wherein said foam includes a surface area density of about 1.6 m2/g.
70. The carbon-carbon composite foam of claim 54, wherein the carbon-carbon composite foam has a solid density of at least about 67%.
71. The carbon-carbon composite foam of claim 54, wherein the carbon-carbon composite foam has a solid density of at least about 76%.
72. The carbon-carbon composite foam of claim 54, wherein the carbon-carbon composite foam has a solid density of at least about 82%.
73. The carbon-carbon composite foam of claim 54, wherein the pyrolytic carbon coating is deposited by the thermal decomposition of a liquid precursor selected from a group consisting of cyclohexane, n-hexane, and benzene.
74. A composite foam having a structure of interconnecting pores that allow fluid to flow through the composite foam, the composite foam comprising:
a) an open lattice of carbon ligaments forming a network of three-dimensionally interconnected cells; and b) a pyrolytic coating formed on the open lattice of carbon ligaments, wherein the carbon-carbon composite foam has a solid density of greater than 30%, and wherein the pyrolytic coating comprises at least one of silicon carbide and silicon nitride.
a) an open lattice of carbon ligaments forming a network of three-dimensionally interconnected cells; and b) a pyrolytic coating formed on the open lattice of carbon ligaments, wherein the carbon-carbon composite foam has a solid density of greater than 30%, and wherein the pyrolytic coating comprises at least one of silicon carbide and silicon nitride.
75. An improved clutch or brake device in which at least two members are mounted for relative rotation and engagement, the members having friction material rotatable therewith, and the friction material of the members having surfaces confronting each other, characterized in that the friction material has a solid density of greater than 30% and includes:
a) an open lattice of carbon ligaments forming a network of three dimensionally interconnected cells; and b) a pyrolytic carbon coating on the open lattice of carbon ligaments.
a) an open lattice of carbon ligaments forming a network of three dimensionally interconnected cells; and b) a pyrolytic carbon coating on the open lattice of carbon ligaments.
76. The improved clutch or brake device of claim 75, wherein the friction material defines a structure of interconnecting pores that allow hydraulic fluid to flow through the friction material.
77. The improved clutch or brake device of claim 76, wherein the friction material has an essentially isotropic structure.
78. The improved clutch or brake device of claim 75, wherein the open lattice of carbon ligaments consists essentially of amorphous carbon.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US11270498P | 1998-12-18 | 1998-12-18 | |
US60/112,704 | 1998-12-18 | ||
PCT/US1999/030140 WO2000035828A1 (en) | 1998-12-18 | 1999-12-17 | Composite foam, articles, and methods of formation |
Publications (2)
Publication Number | Publication Date |
---|---|
CA2356191A1 CA2356191A1 (en) | 2000-06-22 |
CA2356191C true CA2356191C (en) | 2009-05-19 |
Family
ID=22345422
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA002356191A Expired - Fee Related CA2356191C (en) | 1998-12-18 | 1999-12-17 | Composite foam, articles, and methods of formation |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP1144335A1 (en) |
JP (1) | JP2002532372A (en) |
AU (1) | AU2194000A (en) |
CA (1) | CA2356191C (en) |
WO (1) | WO2000035828A1 (en) |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2516914B1 (en) * | 1981-11-26 | 1986-03-14 | Commissariat Energie Atomique | METHOD FOR DENSIFICATION OF A POROUS STRUCTURE |
JP3182212B2 (en) * | 1991-05-21 | 2001-07-03 | アブコウ・コーポレイション | Method for producing a densified porous billet and method for densifying a porous preform |
EP0581696B1 (en) * | 1992-07-23 | 1998-06-24 | Le Carbone Lorraine | Carbon/carbon composite friction material with divided porosity |
US5389152A (en) * | 1992-10-09 | 1995-02-14 | Avco Corporation | Apparatus for densification of porous billets |
US6077464A (en) * | 1996-12-19 | 2000-06-20 | Alliedsignal Inc. | Process of making carbon-carbon composite material made from densified carbon foam |
-
1999
- 1999-12-17 CA CA002356191A patent/CA2356191C/en not_active Expired - Fee Related
- 1999-12-17 AU AU21940/00A patent/AU2194000A/en not_active Abandoned
- 1999-12-17 JP JP2000588093A patent/JP2002532372A/en active Pending
- 1999-12-17 EP EP99966391A patent/EP1144335A1/en not_active Withdrawn
- 1999-12-17 WO PCT/US1999/030140 patent/WO2000035828A1/en active Application Filing
Also Published As
Publication number | Publication date |
---|---|
JP2002532372A (en) | 2002-10-02 |
CA2356191A1 (en) | 2000-06-22 |
AU2194000A (en) | 2000-07-03 |
EP1144335A1 (en) | 2001-10-17 |
WO2000035828A1 (en) | 2000-06-22 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US6726962B1 (en) | Method for forming composite articles | |
US5389152A (en) | Apparatus for densification of porous billets | |
EP1911990A2 (en) | Carbon-carbon friction material with improved wear life | |
CN108516852A (en) | A kind of carbon-silicon carbide double base matrix carbon fibre composite, preparation method and application | |
US5411763A (en) | Method of making a modified ceramic-ceramic composite | |
JPH01249659A (en) | Production of carbon/carbon composite material having oxidation resistance | |
CN114645449A (en) | Preparation method of polyimide resin carbon modified C/C-SiC friction material | |
CA2356191C (en) | Composite foam, articles, and methods of formation | |
CN109095929B (en) | Preparation method of carbon-ceramic brake disc | |
US10323339B2 (en) | Aircraft brake disc materials and methods | |
AU2003262110B2 (en) | Composite foam, articles, and methods of formation | |
JPH06183838A (en) | Silicon carbide composite material having fiber reinforcement covered with metal carbide | |
CA2320258C (en) | Partially densified carbon preform | |
JP2607409B2 (en) | Oxidation-resistant treatment of carbon fiber reinforced carbon composites. | |
JP3548597B2 (en) | Oxidation-resistant treatment method of carbon fiber reinforced carbon composite | |
JPH10209061A (en) | Constitution member for semiconductor diffusion furnace | |
JP2579563B2 (en) | Oxidation-resistant treatment of carbon fiber reinforced carbon composites. | |
JP2024032606A (en) | Method of producing silicon carbide based composite | |
Golecki | Industrial carbon chemical vapor infiltration (CVI) processes | |
AU714371B2 (en) | Method for densification of porous billets | |
JP2002145675A (en) | Production process of carbon-fiber-reinforced carbon material | |
JPH1029881A (en) | Production of oxidation resistant c/c composite material | |
JP2000219584A (en) | Carbon fiber reinforced carbon composite material coated with silicon carbide and its production | |
JPH08198691A (en) | Carbon-boron carbide composite material and its production | |
JPH06247782A (en) | Production of oxidation resistant c/c composite material |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
EEER | Examination request | ||
MKLA | Lapsed |