CN118871406A

CN118871406A - Articles comprising composite materials containing graphite

Info

Publication number: CN118871406A
Application number: CN202380026790.8A
Authority: CN
Inventors: 纳根德拉·纳格
Original assignee: Foseco International Ltd
Current assignee: Foseco International Ltd
Priority date: 2022-03-11
Filing date: 2023-03-11
Publication date: 2024-10-29

Abstract

Methods of forming articles comprising graphite-containing composite materials are disclosed. The article is suitable for containing or processing molten metal such as aluminum. The method includes forming at least one particulate mixture by mixing at least carbon black, flake graphite, needle coke, and at least one resin, wherein the at least one resin has a flow distance of 20mm to 150mm as measured by ISO 8619:2003. The method further includes forming the particulate mixture into a shaped body and firing the shaped body.

Description

Article comprising graphite-containing composite material

Background

The present disclosure relates to methods of forming articles comprising graphite-containing composites, and articles comprising graphite-containing composites.

Articles of manufacture used in molten metal processing (e.g., such as refining vessels, transfer vessels, etc.) are traditionally made of cast iron, which results in heavy articles that absorb heat. Ceramic fiber vacuum formed articles have been developed to overcome the problems associated with their cast iron counterparts. However, such ceramic fiber-formed articles have difficulty meeting basic performance requirements. Recently, reinforced fibrous materials have been developed as alternatives to both cast iron and ceramic fiber vacuum formed articles. However, articles made from reinforcing fiber materials have high costs associated with them or have low quality. Accordingly, there is a need to provide articles of manufacture that can be used in molten metal applications and other applications that overcome the problems associated with cast iron articles, ceramic fiber vacuum formed articles, and articles containing reinforcing fiber materials.

Disclosure of Invention

The present application provides a method of forming an article comprising a graphite-containing composite material, wherein the article is suitable for containing or processing molten metal such as aluminum. The method comprises the following steps:

(a) Forming at least one particulate mixture by mixing at least carbon black, graphite flakes, needle coke, and at least one resin, wherein the resin has a flow distance of 20mm to 150mm as measured by ISO 8619:2003;

(b) Forming the at least one particulate mixture into at least one shaped body; and

(C) Firing the at least one shaped body.

The present application provides a method of forming an article comprising a graphite-containing composite material, the article being suitable for containing or processing molten metal such as aluminum. Non-limiting examples of such articles are ladles, crucibles, filters, rotors and rotor sub-components, continuous fiber wovens, mesh screens, machined components, and the like. The method of the present application provides an article having a desired and controlled porosity and graphite registration. In the remainder of this document, the terms "porosity" and "fine porosity" have the same meaning and may be used interchangeably. The methods of the present disclosure also enable the formation of articles having high strength (e.g., composites having flexural strength of about 10MPa to 25MPa or alternatively higher) and non-wetting (i.e., non-tacky) surfaces. These and other aspects of the present disclosure will now be described in more detail.

Detailed Description

The present disclosure will now be described in more detail by reference to the following discussion and accompanying figures that accompany the present disclosure. In the following description, numerous specific details are set forth, such as specific structures, components, materials, dimensions, processing steps and techniques, in order to provide an understanding of various embodiments of the present disclosure. However, it will be understood by those skilled in the art that various embodiments of the present disclosure may be practiced without these specific details. As used throughout this disclosure, the term "about" generally indicates no more than ±10%, ±5%, ±2%, ±1% or ±0.5% of a certain value. When a range is expressed in this disclosure as from one value to another (e.g., 20 to 40), this disclosure contemplates any value within the range (i.e., 22, 24, 26, 28.5, 31, 33.5, 35, 37.7, 39, or 40) or any amount bounded by any one of the two values within the range (e.g., 28.5-35).

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates to the contrary. It will be further understood that the terms "comprises/comprising," "includes" and/or "including" when used in this disclosure, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

In the context of the present invention, the expression "at least one X" is intended to mean one or more than one X. Mixtures of X may also be used for the purposes of the present invention.

For the case where the particles are spherical or substantially spherical, the particle sizes given herein may refer to diameters. In the case of particles that are substantially different from spheres, the particle size is based on the equivalent diameter of the particles. As known in the art, the term "equivalent diameter" is used to denote the size of an irregularly shaped object by expressing the size of the irregularly shaped object in terms of the diameter of a sphere having the same volume as the irregularly shaped object. The particle size may also be denoted herein as D50 particle size, i.e. half of the particles are above the indicated value and the other half are below the indicated value.

According to the invention, the article is suitable for containing or processing molten metal. Non-limiting examples of such articles are rotors, ladles, filters, and crucibles or parts thereof. These articles are compatible with low and high pressure die casting where molten metal such as molten aluminum is used.

The method of the present invention comprises the steps of (a): at least one particulate mixture is formed by mixing at least carbon black, graphite flakes, needle coke, and at least one resin, wherein the resin has a flow distance of 20mm to 150mm as measured by ISO 8619:2003. The flow distance was measured at 125 ℃ unless otherwise indicated.

As used herein, the term "particulate mixture" refers to a blend mixture comprising at least carbon black, graphite flakes, and needle coke with at least one resin.

The inventors have surprisingly found that carbon black, graphite flakes, needle coke provide complementary shape profiles which provide a high degree of compaction when forming shaped bodies from particulate mixtures. When the powder (i.e., carbon black, flake graphite, and needle coke) is mixed with a resin exhibiting a flow distance as described above, a composite material containing graphite that is excellent in all of porosity, density, surface roughness, strength, and wettability is obtained.

The inventors have found, inter alia, that the method of the present invention provides a composite material having a pore profile with a pore volume and pore size distribution such that at least 95% of the total pore volume is contained in pores having a diameter or equivalent diameter of less than 1 μm; in further embodiments or in the same embodiment, at least 40% of the pore volume of pores having a diameter or equivalent diameter of less than 1 μm is contained in pores having a diameter or equivalent diameter of less than 0.1 μm. The pore profile formed in the fabricated composite material enables a significant reduction in the achievable surface roughness of the composite material in the article. In the context of the present invention, pore profile (pore diameter) is understood to be porosity and is measured according to ASTM C830-00 (2016). The pore profile was measured by mercury (Hg) intrusion analysis. The device employed for performing this analysis is an AutoPore V,Regarding the surface roughness R _a of the composite material obtained by the method of the invention, the method of the invention allows to obtain a composite material with a surface roughness R _a between 3.2 μm and 0.025 μm, wherein the surface roughness R _a is as provided in the ISO 1302:1992 standard. The reduction in surface roughness also affects the adhesion (adhesion energy) or spreading (surface energy) and wetting (contact angle) forces that occur between the molten metal and the article of manufacture. This has a significant impact on the performance of the article of manufacture as a rotating object (e.g., a rotor) or as a stationary part (e.g., a crucible).

When manufactured (e.g., an article of manufacture) by the method according to the present invention, a substantially final shaped (net-shaped) article having a non-wetted surface is obtained. By "substantially final shaped" is meant that the appearance (i.e., size and shape) of the article produced by the methods of the present disclosure approximates (is at least 90% or greater of) the desired appearance (size and shape) of the finished or article. By forming the article in a substantially final shape, the production costs and time associated with the manufacture of the final product are greatly reduced.

By "non-wetting surface" is meant that articles produced from the composite materials of the present disclosure are not penetrated by molten/liquid metal (such as copper or aluminum, for example) even at high pressure P ₀. In graphite articles (e.g., containers loaded with molten metal), infiltration of the molten metal may be achieved by applying a sufficiently high P ₀ to overcome the capillary pressure P _C, where P _C＝-(2σ_LV/r_eff) cos θ, where σ _LV is the surface energy of the liquid, r _eff is the effective pore radius of the composite, and θ is the contact angle of the pore walls. At the effective pore radius of the composite material of the present disclosure, the capillary pressure is too great to allow infiltration of molten metal. Advantageously, in embodiments of the present disclosure, little or no article is eroded by molten metal penetrating the aperture, even after prolonged exposure to molten metal or after repeated exposure to molten metal.

The mixing step, i.e. step (a) as detailed above, may be performed in different ways. For example, the particulate mixture of the present disclosure may be prepared by first adding carbon black, graphite flakes, needle coke, optionally one or more additives as defined below, and a resin. The addition of the various components/materials may be performed in any order. For example, and in one embodiment, carbon black, graphite flakes, needle coke, optionally one or more additives, are added prior to the addition of the resin. In other embodiments, the resin is added first, and then the carbon black, graphite flakes, needle coke are added. The mixing may be performed continuously during the addition of the various components/materials, or intermittently during the addition of the various components/materials. The amounts of the various components/materials used to provide the particulate mixture are specified below.

During mixing, the powder particles (i.e., carbon black, graphite flakes, and needle coke) may be bound together by the resin to form particles. In this embodiment, mixing may also be referred to as granulating. Preferably, the particles may have a size of about 25 μm to about 4mm, preferably a particle size of about 70 μm to about 700 μm.

In another embodiment, the process according to the invention may further comprise a granulation step after the mixing step.

In one example, mixing includes high shear mixing of the raw materials. In one example where high shear mixing equipment is used during mixing, the resin may aid in forming or coating the raw material agglomerates. The mixing parameters may be varied to increase or decrease the size and distribution of the particles as needed to optimize their use in subsequent processing steps. An example of a high shear mixer may be an Eirich mixer or the like. The mixing process forms the particulate mixture of the present disclosure.

In some embodiments, the particulate mixture has a bimodal particle size distribution wherein the first group of particles has a particle size diameter of about 50 μm to about 100 μm and the second group of particles has a particle size diameter of about 110 μm to about 1000 μm. The first set of particles may constitute from about 30 to about 60 volume percent of the total particulate mixture, while the second set of particles may constitute from about 20 to about 40 volume percent of the total particulate mixture (as noted elsewhere in this disclosure, the particle size expressed herein is D50 particle size, i.e., half of the particles are above the expressed value and half are below the expressed value).

The various components (i.e., raw materials) that may be used in the particulate mixture of the present disclosure will now be described in additional detail.

Carbon blacks that may be used in the particulate mixtures of the present disclosure contain at least 99 weight percent carbon and have ash content of 1 weight percent or less. Generally, the carbon content within the carbon blacks that may be used in the present disclosure is from about 99.5 weight percent to about 100 weight percent. The carbon blacks that can be used in the present application are spherical or substantially spherical in shape; there may be some shape irregularities that deviate from a perfect sphere. The carbon blacks useful in the present disclosure have particle sizes of about 10 μm to about 50 μm, preferably about 25 μm to about 40 μm.

Advantageously, the carbon black is present in the particulate mixture in an amount equal to or greater than 2 weight percent, preferably equal to or greater than 3 weight percent, more preferably equal to or greater than 5 weight percent, relative to the total weight of the particulate mixture.

Preferably, the upper limit of the amount of carbon black in the particulate mixture is less than or equal to 15 weight percent, preferably less than or equal to 10 weight percent, more preferably less than or equal to 8 weight percent, relative to the total weight of the particulate mixture.

According to at least one embodiment, the carbon black is present in the particulate mixture in an amount of about 5 weight percent to about 10 weight percent, preferably in an amount of about 5 weight percent to about 8 weight percent, relative to the total weight of the particulate mixture. In the scope of the present invention, the present disclosure contemplates using any number within the scope, or any amount bounded by either of the two values. For example, the content of carbon black in the particulate mixture may be 5 weight percent, 5.5 weight percent, 6 weight percent, 6.5 weight percent, 7 weight percent, 7.5 weight percent, 8 weight percent, 8.5 weight percent, 9 weight percent, 9.5 weight percent, 10 weight percent, or, for example, 5.5 weight percent to 8.5 weight percent.

Needle coke that may be used in the particulate mixture of the present disclosure contains at least 99 weight percent carbon and has a sulfur content of 1 weight percent or less. Generally, the carbon content of needle coke that may be used in the present disclosure is from about 99.5 weight percent to about 100 weight percent. Needle coke that may be used in the particulate mixture of the present disclosure is irregularly shaped needle coke. "irregularly shaped needle coke" means that it has evolved from (or has) a fibrous, cylindrical or needle structure. Needle coke that may be used in the present disclosure has a particle size of about 10 μm to about 50 μm, with a particle size of about 25 μm to about 40 μm being more typical.

The inventors have determined that needle coke exhibits similar toughness and increased thermal shock resistance compared to other types of carbon (such as, for example, chopped carbon fibers). The inventors have also confirmed that needle coke exhibits excellent oxidation resistance compared to carbon fibers, and further that the use of needle coke (compared to comparative carbon fibers) provides excellent surface smoothness in a composite material comprising graphite when firing a molded body to provide a composite material comprising graphite. Thus, the surface smoothness of the composite material is improved by using needle coke.

Advantageously, the needle coke is present in the particulate mixture in an amount equal to or greater than 0.5 weight percent, preferably equal to or greater than 1 weight percent, more preferably equal to or greater than 2 weight percent, relative to the total weight of the particulate mixture.

Preferably, the upper limit of the amount of needle coke in the particulate mixture is less than or equal to 7 weight percent, preferably less than or equal to 5 weight percent, more preferably less than or equal to 4 weight percent, relative to the total weight of the particulate mixture.

In a preferred embodiment of the present invention, the needle coke is present in the particulate mixture in an amount of from about 1 weight percent to about 5 weight percent, preferably in an amount of from about 2 weight percent to about 4 weight percent, relative to the total weight of the particulate mixture.

The graphite flakes that can be used in the particulate mixture of the present disclosure contain at least 95 weight percent carbon and have an ash content of 1 weight percent or less. Generally, the carbon content of the graphite flakes that may be used in the present disclosure is from about 95 weight percent to about 99 weight percent. The graphite flakes that can be used in the present disclosure have a particle size of about 10 μm to about 500 μm, with particle sizes of about 25 μm to about 40 μm being more typical. In one embodiment, the graphite flakes that may be used in the particulate mixture of the present disclosure are of the naturally occurring graphite type, which is typically in the form of discrete flakes; the discrete flakes may comprise hexagonal crystals; there may be some irregularities in the shape of the platelet graphite crystals that deviate from a perfect hexagon. In one embodiment, the graphite flakes that may be used in the particulate mixture of the present disclosure have a distinct platelet or plate morphology.

Advantageously, the graphite flakes are present in the particulate mixture in an amount equal to or greater than 50 weight percent, preferably equal to or greater than 65 weight percent, more preferably equal to or greater than 75 weight percent, relative to the total weight of the particulate mixture.

Preferably, the upper limit of the amount of graphite flakes in the particulate mixture is less than or equal to 90 weight percent, preferably less than or equal to 85 weight percent, more preferably less than or equal to 80 weight percent, relative to the total weight of the particulate mixture.

In a preferred embodiment of the present invention, the graphite flakes are present in the particulate mixture in an amount of about 65 to about 85 weight percent, preferably in an amount of about 75 to about 80 weight percent, relative to the total weight of the particulate mixture.

In at least one embodiment, the generally hexagonal crystal morphology of the flake graphite, the fibrous, cylindrical, needle or irregular shape of the needle coke, and the substantially spherical shape of the carbon black provide complementary shape contours that provide a high degree of compaction when forming a shaped body from the particulate mixture.

Preferably, at least a portion of the carbon black has a generally spherical shape. Preferably, at least a portion of the needle coke has a generally cylindrical, fibrous, or needle profile. Preferably, at least a portion of the graphite flakes have a generally hexagonal or triangular profile.

According to the present invention, the resin has a dome (button) flow distance of 20mm up to 150mm as measured by ISO 8619:2003. Those skilled in the art will be able to select an appropriate resin to achieve the desired flow distance of the present invention. The inventors have surprisingly found that the particulate mixture of the present disclosure comprising a resin having a dome flow distance of 20mm up to 150mm as measured by ISO 8619:2003 reduces the complexity and number of steps in the mixing step compared to prior art adhesive systems.

Advantageously, the resin has a dome flow distance as measured by ISO 8619:2003 of equal to or greater than 20mm, preferably equal to or greater than 40, more preferably equal to or greater than 70 mm.

Preferably, the upper limit of the flow distance of the resin as measured by ISO 8619:2003 is less than or equal to 150mm, preferably less than or equal to 70mm, more preferably less than or equal to 40mm.

In a preferred embodiment of the invention, the resin has a dome flow distance of from 70mm up to 150mm, preferably from 40mm to 70mm, more preferably from 20mm up to 40mm as measured by ISO 8619:2003.

In one embodiment of the method according to the invention, resins may be used having a dome flow distance of 70mm up to 150mm as measured by ISO 8619:2003. Resins having such a flow distance may be described herein as "low molecular weight resins". In another embodiment of the present disclosure, the resin that may be used in the present disclosure has a dome flow distance of 40mm to 70mm as measured by ISO 8619:2003. Resins having such a flow distance may be referred to herein as "medium molecular weight resins". In yet another embodiment of the present disclosure, the resin that may be used in the present disclosure has a dome flow distance of 20mm up to 70mm as measured by ISO 8619:2003. Resins having such a flow distance may be referred to herein as "high molecular weight resins". In still other embodiments of the present disclosure, any combination of low molecular weight resins, medium molecular weight resins, high molecular weight resins may be employed.

It should be noted that the type of resin (i.e., low, medium, and high molecular weight resins as defined above) may be selected to control the overall viscosity of the adhesive system. It should further be noted that the type of resin (i.e., low, medium and high molecular weight resins as defined above) affects the green strength. For example, a high molecular weight resin as defined herein provides the highest strength green body (flexural strength above 2 MPa), a medium molecular weight resin as defined herein provides the medium strength green body (flexural strength between 1MPa and 2 MPa), and a low molecular weight resin as defined herein provides the lowest strength green body (flexural strength below <1 MPa). The green body represents the particulate mixture after forming and before firing.

It should be noted that the resins of the present disclosure aid in the pelletization mixing step of forming the particulate mixture. The organic matter of the resin is typically removed during the firing process.

Preferably, a resin having a viscosity of about 9000cps to about 30,000,000cps is selected. More preferably, a resin having a viscosity of about 9000cps to about 150,000cps is selected. Unless otherwise indicated, viscosity is measured at 25 ℃.

Advantageously, the resin is present in the particulate mixture in an amount equal to or greater than 2 weight percent, preferably equal to or greater than 4 weight percent, more preferably equal to or greater than 6 weight percent, relative to the total weight of the particulate mixture.

Preferably, the upper limit of the amount of resin in the particulate mixture is less than or equal to 15 weight percent, preferably less than or equal to 10 weight percent, more preferably less than or equal to 8 weight percent, relative to the total weight of the particulate mixture.

In a preferred embodiment of the invention, the resin is present in the particulate mixture in an amount of from about 2 weight percent to about 10 weight percent, preferably in an amount of from about 6 weight percent to about 8 weight percent, relative to the total weight of the particulate mixture.

In the context of the present invention, the resin may be in various physical states, preferably the resin is in a liquid state.

Preferably, the resin is a thermosetting resin.

The choice of resin is advantageously determined by the high char formation rate after pyrolysis. Table 1 below sets forth typical char formation rates after pyrolysis of various carbon source materials. Preferably, the resin provides a high char formation after pyrolysis of equal to or greater than 40 weight percent, or equal to or greater than 50 weight percent, or equal to or greater than 60 weight percent.

TABLE 1

Carbon source	Typical char formation rate after pyrolysis wt%
		Coal tar pitch	45-55
Phenolic resin	40-70
		Furan resin	45-60
Polyacrylonitrile (PAN) cellulose	35-45
		Epoxy resin	25-35
Unsaturated polyester resin	15-25
		Polypropylene (PP)	<2
Polyethylene terephthalate (PET)	<0.5

As will be appreciated by those skilled in the art, amorphous carbon (i.e., amorphous carbon produced by resin conversion when the shaped body is fired to provide a composite material comprising graphite) may be further reformed into other forms of carbon, such as crystalline carbon in the form of carbon nanotubes, graphene, and similar other materials, for example.

Advantageously, the resin is selected from the group consisting of: phenolic resins, cellulose-based derivatives, silicone-modified resins, modified epoxy resins, polyimides, benzoxazines, or any combination thereof. Non-limiting examples of commercial polyimides are ZT1000[ polyimide ] and kenite company (Cornerstone) (18C 021). A non-limiting example of a commercial benzoxazine is Henscman (Huntsman) (18B 028). In some embodiments, the resin additionally comprises additives such as carbores. More preferably, the resin is a phenolic resin. One advantage of using phenolic resin is that, for example, up to 70wt% of the phenolic resin can be converted to carbon in the form of amorphous carbon when the shaped body is fired to provide a composite material comprising graphite.

In a preferred embodiment of the invention, the resin may be formed by condensing phenol or a phenol derivative with an aldehyde, especially formaldehyde, in the presence of a catalyst. In one embodiment of the present disclosure, phenolic resins that may be used in the present disclosure have a dome flow distance of 70mm up to 150mm as measured by ISO 8619:2003. Phenolic resins having such flow distances may be referred to herein as "low molecular weight phenolic resins". In another embodiment of the present disclosure, phenolic resins that may be used in the present disclosure have a dome flow distance of 40mm to 70mm as measured by ISO 8619:2003. Phenolic resins having such flow distances may be referred to herein as "medium molecular weight phenolic resins". In yet another embodiment of the present disclosure, phenolic resins that may be used in the present disclosure have a dome flow distance of 20mm up to 70mm as measured by ISO 8619:2003. Phenolic resins having such flow distances may be referred to herein as "high molecular weight phenolic resins". In one example, the phenolic resin that may be used in the present disclosure is a commercially available phenolic resin known as Sumitomo XF 3011P. In yet another embodiment of the present disclosure, the phenolic resin employed is a liquid phenolic resin. In still other embodiments of the present disclosure, any combination of low molecular weight phenolic resins, medium molecular weight phenolic resins, high molecular weight phenolic resins, or liquid phenolic resins may be employed.

According to at least one embodiment, at least one solvent may be added to the resin in order to further improve the flowability and/or viscosity of the resin. In this embodiment, the resin may also be referred to as an adhesive system, which consists of at least one resin and at least one solvent. It should be noted that the type of resin and the type of solvent may be selected to control the overall viscosity of the adhesive system. According to at least one embodiment, the solvent comprises a dibasic ester. In one embodiment, the solvent may be a dibasic ester that is an ester of a dicarboxylic acid having the formula CH ₃O₂C(CH₂)_nCO₂CH₃, wherein n is equal to 2,3, or 4. In some embodiments, the solvent used is an acetate. In further embodiments, the acetate is propylene glycol diacetate. Other solvents are possible and may be used in combination with the resin as the adhesive system of the present disclosure. According to embodiments of the present disclosure, the resin and solvent are present in the particulate mixture in a weight ratio of about 1:1 to about 6:1. According to another embodiment of the present disclosure, the resin and solvent are present in the particulate mixture in a weight ratio of about 2:1 to about 4:1.

When the resin further comprises a solvent, the solvent is present in the particulate mixture in an amount of about 1 to about 5 weight percent, preferably in an amount of about 3 to about 4 weight percent, relative to the total weight of the particulate mixture.

In some embodiments, the resin of the particulate mixture additionally comprises an optional binder plasticizer. Thus, in some embodiments, the resin may further comprise a binder plasticizer, such as, for example, dextrin, propylene carbonate, stearic acid, oleic acid, glycerol, and/or glycerol triacetate; in other embodiments, no adhesive plasticizer is used.

In some embodiments, the particulate mixture of the present disclosure is free of any intentionally added water. In still other embodiments, water may be included in the particulate mixture of the present disclosure. In some embodiments of the present disclosure, the particulate mixture has a moisture content of less than about 5.0 weight percent, preferably equal to or less than 4.0 weight percent, more preferably equal to or less than 3.0 weight percent, relative to the total weight of the particulate mixture. Advantageously, the particulate mixture has a moisture content equal to or greater than 0.5 weight percent, preferably equal to or greater than 1 weight percent, more preferably equal to or greater than 2.0 weight percent, relative to the total weight of the particulate mixture. In one example, the moisture content of the particulate mixture is about 1.0 weight percent to 4.0 weight percent relative to the total weight of the particulate mixture.

According to at least one embodiment, the carbon black, the graphite flakes, the needle coke, and the resin provide 100% of the total weight of the particulate mixture. In this example, the particulate mixture is entirely composed of carbon black, flake graphite, needle coke, and resin; no other components/additives are used in providing the particulate mixture. This embodiment can be advantageously used for manufacturing articles in which the presence of foreign substances other than carbon is not desired, such as for example crucibles used in the manufacture of synthetic graphite.

In one embodiment, the particulate mixture comprises about 6 weight percent, 6.2 weight percent, 6.4 weight percent, 6.6 weight percent, 6.8 weight percent, 7 weight percent, 7.2 weight percent, 7.5 weight percent, or carbon black in a range defined by any two of the foregoing values, about 1 weight percent, 1.2 weight percent, 1.4 weight percent, 1.6 weight percent, 1.8 weight percent, 2 weight percent, 2.2 weight percent, 2.5 weight percent, or needle coke in a range defined by any two of the foregoing values, about 78 weight percent, 78.2 weight percent, 78.4 weight percent, 78.6 weight percent, 78.8 weight percent, 79 weight percent, 79.2 weight percent, 79.5 weight percent, or graphite in a range defined by any two of the foregoing values, about 7.7 weight percent, 8.4 weight percent, 7.4 weight percent, or sheet coke in a range defined by any two of the foregoing values, about 7.8 weight percent, 8.4 weight percent, 7.5 weight percent, or sheet coke in a range defined by any two of the foregoing values. When the particulate mixture further contains a solvent, and about 3 weight percent, 3.2 weight percent, 3.4 weight percent, 3.6 weight percent, the particulate mixture further comprises about 3.8 weight percent, 4 weight percent, 4.2 weight percent, 4.5 weight percent, or a solvent within a range defined by any two of the foregoing values.

In other embodiments, the particulate mixture further comprises one or more of the following: an antioxidant additive, a toughening/strength enhancing additive, an abrasion/erosion resistant agent, a thermal insulation enhancing agent, and a transition metal selected from groups 4 to 12 of the periodic table of elements. These additives may take the form of powders or granules.

According to at least one embodiment, the particulate mixture further comprises about 5 to about 15 weight percent, preferably about 8 to about 12 weight percent, of an antioxidant additive relative to the total weight of the particulate mixture. According to at least one embodiment, the antioxidant additive comprises boron carbide, silicon carbide, aluminum zinc phosphate, or any combination thereof.

The antioxidant additive serves to reduce oxidation of the resulting composite while plugging the pores and increasing the apparent density of the resulting composite. Exemplary antioxidant additives that may be present in the particulate mixture of the present disclosure include, but are not limited to, boron carbide, silicon carbide, bentonite, aluminum zinc phosphate, or any combination thereof. In one embodiment, the antioxidant additive comprises a mixture of, relative to the total weight of the antioxidant additive: about 2 to about 7 weight percent boron carbide, about 1 to about 5 weight percent silicon carbide, about 0.25 to about 0.75 weight percent bentonite, and about 2 to about 5 weight percent aluminum zinc phosphate.

In some embodiments in which boron carbide is employed as the antioxidant additive, the boron carbide is provided in the form of fine particles having a particle size of less than about 50 μm, preferably in the range of about 25 μm to about 40 μm. In some embodiments in which silicon carbide is employed as the antioxidant additive, the silicon carbide is provided in the form of fine particles having a particle size of less than about 50 μm, preferably in the range of about 20 μm to about 40 μm. In some embodiments in which bentonite is employed as an antioxidant additive, the bentonite is provided in the form of fine particles having a particle size of less than about 10 μm, preferably in the range of about 1 μm to about 7 μm. In various embodiments, the boron carbide, silicon carbide, and bentonite may take the form of powders or granules.

In some embodiments, the addition of the antioxidant may be performed in two separate or distinct stages. In embodiments in which the antioxidant addition is performed in two stages, the first stage antioxidant additive is added to the particulate mixture during the first of the two stages. The granular mixture is then shaped into a shaped body consisting of the granular mixture. In a second of the two stages, a second stage antioxidant additive is applied to a portion or all of one or more exposed surfaces of the shaped body, followed by firing of the shaped body to provide a composite of graphite. In some embodiments, the first stage antioxidant additive added in the first stage is a different material than the second stage antioxidant additive added in the second stage. In some embodiments, the first stage antioxidant additive added in the first stage is the same material as the second stage antioxidant additive added in the second stage.

According to at least one embodiment, the particulate mixture further comprises from about 1 weight percent to about 5 weight percent, preferably from about 2.5 weight percent to about 4.5 weight percent, of a toughening/strength enhancing additive relative to the total weight of the particulate mixture. According to at least one embodiment, the toughening/strength enhancing additive comprises carbon fibers, chopped carbon fiber bundles, basalt bundles, aluminum silicate fibers, chopped steel fibers, or any combination thereof.

The toughening/strength enhancing additives serve to increase the toughness and/or strength of the resulting composite. Exemplary toughening/strength enhancing additives that may be present in the particulate mixtures of the present disclosure include, but are not limited to, carbon fibers, chopped carbon fiber bundles, basalt bundles, aluminum silicate fibers, chopped steel fibers, or any combination thereof. In some embodiments, the toughening/strength enhancing additive comprises carbon fibers, chopped carbon fiber bundles, or a combination thereof; such toughening/strength enhancing additives increase the toughness of the resulting fabricated articles made from the particulate mixtures of the present application. In some embodiments, the toughening/strength enhancing additive comprises basalt, aluminum silicate fibers, or a combination thereof; such toughening/strength enhancing additives improve the strength and reduce the thermal conductivity of the resulting fabricated article made from the particulate mixture of the present application. In some embodiments, the toughening/strength enhancing additive comprises chopped steel fibers; such toughening/strength enhancing additives increase the strength and toughness of the resulting fabricated articles made from the particulate mixtures of the present disclosure.

According to at least one embodiment, the particulate mixture further comprises from about 1 weight percent to about 10 weight percent, preferably from about 4.5 weight percent to about 8.5 weight percent, of an abrasive/erosion resistant agent relative to the total weight of the particulate mixture. According to at least one embodiment, the wear/erosion resistant agent comprises a metal oxide, a metal nitride, a metal boride, or any combination thereof.

The abrasion/erosion resistant agent serves to increase the abrasion of the resulting composite and/or reduce erosion of the composite. Illustrative examples of wear/erosion resistant agents that may be used in the present application include metal oxides (e.g., such as zirconia, or yttria), metal nitrides (e.g., such as boron nitride, aluminum nitride, or silicon nitride), metal borides (e.g., such as titanium diboride), or any combination thereof. In some embodiments, zirconia is used as the wear/erosion resistant agent. In such embodiments, the zirconia may form zirconium silicide or zirconium silicate in situ, which may result in strong bonding, high oxygen resistance, high wear/erosion resistance, and/or very fine pore profiles. In such embodiments, the zirconia may form zirconium boride with exceptionally high wear/erosion resistance. The wear/erosion resistant agents that may be used in the present disclosure are typically nano-micron sized powders having a particle size of less than about 40 μm, with particle sizes in the range of about 5 μm to about 25 μm being more common.

According to at least one embodiment, the particulate mixture further comprises from about 1 to about 5 weight percent, preferably from 2.5 to 4 weight percent, of a thermal insulation enhancer, relative to the total weight of the particulate mixture. These agents provide improved thermal insulation to the resulting composite. Illustrative examples of insulation enhancers that may be used in the present disclosure include, but are not limited to, colloidal silica pellets, fibers, or mixtures thereof. According to at least one embodiment, the thermal insulation enhancer comprises colloidal silica pellets, fibers, or mixtures thereof. According to at least one embodiment, the thermal insulation enhancer comprises a mixture of sodium aluminosilicate pellets and chopped silica fibers. According to at least one embodiment, optionally, the thermal insulation enhancer comprises colloidal silica pellets, preferably aluminum colloid silicate pellets; fibers, preferably a mixture of sodium and chopped silica fibers; or a mixture thereof. In such embodiments, the mixture may comprise about 5 to about 50 weight percent sodium aluminosilicate pellets and about 20 to about 70 weight percent chopped silica fibers relative to the total weight of the thermal insulation enhancer.

According to at least one embodiment, the particulate mixture further comprises from about 1 to about 5 weight percent, preferably from 2.5 to about 4 weight percent of a transition metal selected from groups 4 to 12 of the periodic table of elements, relative to the total weight of the particulate mixture. Transition metals may be used to add specific functions (e.g., catalytic functions) to the resulting composite. Illustrative examples of suitable transition metals that may be used in the present disclosure include, but are not limited to, iron, titanium, nickel, or any combination thereof.

In some embodiments, clay may also be present in the particulate mixture of the present disclosure; when present, the clay is preferably present in an amount of about 0.25 weight percent to about 0.75 weight percent relative to the total weight of the particulate mixture.

In embodiments in which the mixing step provides particles and the particulate mixture comprises a toughening/strength enhancing additive as defined above, an abrasion/erosion resistant agent as defined above, a thermal insulation enhancing agent as defined above, a transition metal as defined above, or any combination thereof, these additives may be located (dispersed) within the particles of the particulate mixture, or these additives may be located between the particles of the particulate mixture.

According to at least one embodiment, the particulate mixture as detailed previously consists essentially of particles, and wherein the toughening/strength enhancing additive, the wear/erosion resistant agent, the thermal insulation enhancing agent, the transition metal selected from groups 4 to 12 of the periodic table, or any combination thereof is located within these particles. According to at least one embodiment, the particulate mixture as detailed previously consists essentially of particles, and wherein the toughening/strength enhancing additive, the wear/erosion resistant agent, the thermal insulation enhancing agent, the transition metal selected from groups 4 to 12 of the periodic table, or any combination thereof, is located between the particles of the particulate mixture.

In some embodiments of the present disclosure, the particulate mixture comprises about 5 to about 10 weight percent carbon black, about 65 to about 85 weight percent graphite flakes, about 1to about 5 weight percent needle coke, about 2 to about 10 weight percent phenolic resin, and about 1to about 5 weight percent solvent. In still other embodiments, the particulate mixture comprises from about 5 to about 8 weight percent carbon black, from about 75 to about 80 weight percent graphite flakes, from about 2 to about 4 weight percent needle coke, from about 6 to about 8 weight percent phenolic resin, and from about 3 to about 4 weight percent solvent. In the ranges expressed above, the present disclosure contemplates using any value within the range, or any amount bounded by either of the two values. For example, the content of carbon black in the particulate mixture may be 5 weight percent, 5.5 weight percent, 6 weight percent, 6.5 weight percent, 7 weight percent, 7.5 weight percent, 8 weight percent, 8.5 weight percent, 9 weight percent, 9.5 weight percent, 10 weight percent, or, for example, 5.5 weight percent to 8.5 weight percent.

After forming the particulate mixture (i.e., step (a) as detailed above), shaping the particulate mixture into a shaped body (i.e., step (b)); the shaped body may be referred to as a green body. Shaping may include, but is not limited to, isostatic pressing (i.e., isostatic pressing), hydraulic pressing, extrusion, molding, or 3D printing. In some embodiments, the shaping may be determined by the amount of resin present in the particulate mixture. For example, 4wt.% to 8wt.% of the resin in the particulate mixture may be advantageous for isostatic or hydraulic pressing; 8wt.% to 12wt.% of a resin may be advantageous for extrusion; while 12wt.% to 17wt.% of resin may be advantageous for 3D printing. In some embodiments, shaping the particulate mixture into a shaped body comprises the steps of: machining or final shaping the particulate mixture to form a rotor component; forming the particulate mixture into a ladle; shaping the granular mixture to form a crucible, and extruding or 3D printing the granular mixture to form the crucible. In one example, the particulate mixture may be subjected to isostatic pressing using a molded polyurethane bag pressed against a metal mandrel. The shaped body may comprise any shape including, for example, the shape of the rotor or rotor component, ladle, crucible, and molten metal filter or filter component. In some embodiments, the shaped body may be formed on a prefabricated structure, such as, for example, a steel mesh, a filter or filter component, and a continuous carbon woven fabric, prior to firing.

The inventors have found that the process of the present invention provides a shaped body having a green strength of from about 1MPa to about 5MPa flexural strength, a green density of from about 1.5g/cm ³ to about 1.7g/cm ³, and a powder fill density of from about 0.5g/cm ³ to about 0.7g/cm ³. In the present disclosure, green strength may be measured by a 3-point bending test of a test piece (e.g., to measure flexural strength), green density may be measured by volume and weight measurements of the test piece, and powder fill density may be measured by measuring the weight of powder filling a container of known volume. As used herein, "green strength" may refer to the strength of a material when processed to form its final fracture strength. As used herein, "green density" is the density of the shaped body prior to any heat treatment.

Preferably, when the shaping is isostatic (i.e., isostatic pressing), during the mixing step (i.e., step (a) as detailed above), the powder particles (i.e., carbon black, graphite flakes, and needle coke) may be bonded together by the resin, thereby forming particles. In this embodiment, mixing may also be referred to as granulating.

In some embodiments, the shaped body may comprise a crucible shape, wherein the crucible shape is made up of a plurality of crucible rings that are stacked on top of each other uniformly to provide the crucible shape. The crucible ring is preferably obtained by the steps of: the granular mixture is finally shaped into a precise ring shape or the granular mixture is shaped into a large crucible shape, which is cut into crucible rings and machined. This shaping is particularly advantageous because it allows partial replacement of the crucible rather than having to replace the entire crucible, thereby increasing repair time, reducing costs and improving overall efficiency.

In some embodiments, the shaped body may be cured prior to firing. Curing the shaped body before firing causes crosslinking of the resin, which allows improved handling and handling of the shaped body before firing. Curing may be performed in air prior to firing. The curing may be performed at a single curing temperature, or various curing temperatures may be used. In one embodiment of the present disclosure, curing is performed at a temperature of about 200 ℃ to about 300 ℃ for a period of about 1 to about 5 hours. Other curing temperatures and/or times may be used in the present disclosure. Curing may be carried out in any curing device commonly used in the art.

In some embodiments of the present disclosure, the shaped body may undergo a coating process, a glazing process, an injection process, an infiltration process, or any combination thereof prior to firing. The coating process, glazing process, injection process, and/or infiltration process may be performed directly on the shaped body, or such process may be performed on the shaped body that has first undergone curing.

When the coating process is performed, at least a portion of the cured or uncured shaped body may be coated with any suitable coating material using any well known coating technique (e.g., such as spraying, dipping, brushing, etc.). In some embodiments, a silicon carbide (SiC), aluminum oxide, or aluminum titanate (aluminum-titanate) coating may be formed on at least a portion of the cured or uncured shaped body. In some embodiments, a boron nitride coating may be formed on at least a portion of the cured or uncured shaped body. The coating may alter the porosity and/or finish of the composite.

When the glazing process is performed, at least a portion of the cured or uncured shaped body may be glazed with any suitable glazing material using any well known glazing technique (e.g., such as spraying, dipping, brushing, etc.). In one example, glazing materials formulated from frit-based compositions may be used.

When the injection process is performed, the material may be injected into at least a portion of the cured or uncured and formed body using any well known injection process (such as, for example, roll injection, step injection, and immersion injection). In one example, the borax mixture may be injected into at least a portion of the cured and/or uncured shaped body prior to firing. In one embodiment, at least a portion of a shaped body composed of the particulate mixture is coated with an injection material (e.g., an antioxidant additive) and then the shaped body is fired, wherein the injection material (e.g., the antioxidant additive) is injected into a composite composed of graphite resulting from firing the shaped body.

When the infiltration process is performed, at least a portion of the cured or uncured shaped body may be infiltrated with any suitable material using any well known infiltration technique (e.g., such as injection, chemical vapor infiltration, etc.). Preferably, at least a portion of the cured or uncured shaped body is impregnated with a siloxane, a selected phosphate solution, or any combination thereof, either before or after the firing step. In one example, the siloxane precursor, the selected phosphate solution, or any combination thereof may be impregnated into at least a portion of the shaped body prior to firing. In some embodiments, at least a portion of the composite material is impregnated with a siloxane, a selected phosphate solution, or any combination thereof, either before or after the firing step. In one example, the siloxane precursor, the selected phosphate solution, or any combination thereof may be impregnated into at least a portion of the composite after firing. In one embodiment, at least a portion of a shaped body composed of the particulate mixture is impregnated with an impregnating material (e.g., an antioxidant additive) followed by firing the shaped body, wherein the impregnating material (e.g., the antioxidant additive) impregnates into a composite material comprising graphite resulting from firing the shaped body.

Next, the shaped body is fired to provide a composite material comprising graphite (i.e., step (c)). Firing the shaped body containing the particulate mixture of the present disclosure provides a composite material comprising graphite. The composite material may also be an article composed of the composite material. Alternatively, the composite may be further subjected to a manufacturing step to provide an article comprising the composite. The article may be composed of a plurality of composite materials that are stacked together to provide the article. For example, when the article is a crucible, the crucible may be made up of a plurality of crucible rings that are stacked on top of each other uniformly to provide the crucible. Alternatively or additionally, the composite material may undergo a coating process, a glazing process, an injection process, and/or an infiltration process to provide the article. Non-limiting examples of such articles include rotors, ladles, filters, and crucibles or components thereof.

The inventors have found that the method of the present invention provides a composite material comprising graphite with improved properties, such as about 10% to about 25% porosity. Moreover, the composite material obtained by the process of the present invention has an apparent density of from about 1.6g/cm ³ to about 1.92g/cm ³. Advantageously, the composite material has a certain total pore volume and pore size distribution, wherein at least 95% of the total pore volume is contained in pores having a diameter or equivalent diameter of less than 1 μm and at least 40% of the pore volume of pores having a diameter or equivalent diameter of less than 1 μm is contained in pores having a diameter or equivalent diameter of less than 0.1 μm. The fine pore profile formed in the composite material in the article of manufacture enables a significant reduction in the obtainable surface roughness of the composite material in the article of manufacture. With respect to the surface roughness R _a of the composite material resulting from firing the shaped body, ISO 1302:1992 provides a method of indicating the surface roughness. In fact, the average roughness (R _a) is often used in industry as a measure of surface smoothness. With the method of the invention it is possible to obtain a composite material with a surface roughness R _a between 3.2 μm and 0.025 μm, wherein the surface roughness R _a is as provided in the ISO 1302:1992 standard. The reduction in surface roughness also affects the adhesion (adhesion energy) or spreading (surface energy) and wetting (contact angle) forces that occur between the molten metal and the article of manufacture. This has a significant impact on the performance of the article of manufacture as a rotating object (e.g., a rotor) or as a stationary part (e.g., a crucible).

Furthermore, according to the present invention, it is possible to provide an article (e.g., an article of manufacture) that is a substantially final shaped article and has the non-wetting surface described previously.

Firing may be performed at a single firing temperature, or various firing temperatures may be used. In one embodiment, firing is performed at a temperature of about 800 ℃ to about 1500 ℃. In one embodiment, the firing temperature is between 800 ℃ and 1300 ℃. In one embodiment, the firing temperature is about 1250 ℃ to about 1300 ℃, preferably about 1000 ℃ to about 1250 ℃. In one embodiment, the firing temperature is about 1400 ℃ to about 1500 ℃. In one embodiment, the firing temperature is about 1250 ℃. In one embodiment, the firing temperature is about 1050 ℃.

The period of firing may vary depending on the temperature of the firing process and the exact composition of the shaped body. In one example, and within a temperature of about 1250 ℃ to about 1500 ℃, firing can be performed for a period of 5 hours to 50 hours, including a time to ramp up to peak temperature and a hold time. Firing can be performed under various environmental conditions, such as, for example, in a reducing environment or in a carbocyclic environment (such as, for example, carbon monoxide). The carbon environment may be mixed with an inert carrier gas (i.e., helium, argon, and/or nitrogen).

Various firing temperature profiles (firing profiles) may be used in the present disclosure. In one example, firing of the glazed shaped body can be carried out in a reducing atmosphere at a temperature of about 1250 ℃ to about 1300 ℃. In another example, and for glazed/coated shaped bodies, firing in air at a temperature of about 1000 ℃ to about 1250 ℃ may be employed. In further examples, the coated or uncoated shaped body may be fired in a reducing atmosphere at a temperature of about 1400 ℃ to about 1500 ℃.

In some embodiments, a firing stage antioxidant additive (which may alternatively be referred to herein as a second stage antioxidant additive) may be added to the shaped article during the firing process. Illustrative examples of firing stage antioxidant additives that may be used in the present disclosure include, but are not limited to, bentonite clay, zinc phosphate, aluminum zinc phosphate, or any combination thereof. The firing stage antioxidant additive may be added in an amount of about 1 to about 6 weight percent, with a range of about 2 to about 4 weight percent being more common. In some embodiments, the firing stage antioxidant additive is the only antioxidant additive present. In other embodiments, the firing stage antioxidant additive is used in combination with an antioxidant additive that is added to form a particulate mixture. In such embodiments, the oxidation resistant additive added to form the particulate mixture may be referred to as a first stage oxidation resistant additive group comprising boron carbide, silicon carbide, bentonite, aluminum zinc phosphate, or any combination thereof, as defined above, while the firing stage oxidation resistant additive may be referred to as a second stage oxidation resistant additive group that is different from the first oxidation resistant additive group and comprises bentonite, zinc phosphate, aluminum zinc phosphate, or any combination thereof.

In various embodiments, firing of the shaped body (containing the particulate mixture of the present disclosure) provides a graphite-containing composite material having a fine pore profile in which at least 95% of the total pore volume is contained in pores having a diameter of less than 1 μm and at least 40% of the pore volume of pores having a diameter of less than 1 μm is contained in pores having a diameter of less than 0.1 μm. This pore profile formed in the composite of the present disclosure results in excellent surface smoothness of the composite or articles formed from the composite. With respect to the surface roughness R _a of the composite material resulting from firing the shaped body, ISO 1302:1992 provides a method of indicating surface roughness. In fact, the average roughness (R _a) is often used in industry as a measure of surface smoothness.

In some embodiments of the present disclosure, the method of the present disclosure further comprises the step of coating, glazing, impregnating, or any combination thereof as described above, either before or after the firing step. Preferably, when the coating step is provided, at least a portion of the composite material is coated with the coating. In other words, at least a portion of the surface of the composite is coated with a coating. Advantageously, the coating is at least one coating selected from the group comprising: boron nitride, silicon carbide, aluminum oxide or aluminum titanate.

According to at least one embodiment, when an impregnating step is provided, at least a portion of the composite material is impregnated with a siloxane, a selected phosphate solution, or any combination thereof, either before or after the firing step.

In another aspect of the present disclosure, a composite material comprising graphite is provided. Furthermore, articles comprising the graphite-containing composite are provided. As described above, the composite material may also be an article composed of the composite material. Alternatively, the composite may be further subjected to a manufacturing step to provide an article comprising the composite. Non-limiting examples of such articles include rotors, ladles, filters, and crucibles or components thereof. In a preferred embodiment of the invention, the article is a crucible, which is made up of a plurality of crucible rings, which are stacked on top of each other uniformly to provide the crucible. Alternatively or additionally, the composite material may further undergo a coating process, a glazing process, an injection process, and/or an infiltration process to provide the article.

The composite has a total pore volume and a pore size distribution wherein at least 95% of the total pore volume is contained in pores having a diameter or equivalent diameter of less than 1 μm and at least 40% of the pore volume of pores having a diameter or equivalent diameter of less than 1 μm is contained in pores having a diameter or equivalent diameter of less than 0.1 μm. Preferably, the composite material has a certain total pore volume and pore size distribution, wherein at least 97% of the total pore volume is contained in pores with a diameter of less than 1 μm and at least 40% of the pore volume of pores with a diameter of less than 1 μm is contained in pores with a diameter of less than 0.1 μm.

This pore profile can be seen on the right side of fig. 1, titled 'pore size in fired graphite mixture'. The fine pore profile formed in the composite material in the article of manufacture enables a significant reduction in the obtainable surface roughness of the composite material in the article of manufacture. The reduction in surface roughness also affects the adhesion (adhesion energy) or spreading (surface energy) and wetting (contact angle) forces that occur between the molten metal and the article of manufacture. This has a significant impact on the performance of the article of manufacture as a rotating object (e.g., a rotor) or as a stationary part (e.g., a crucible).

It is further understood that all the definitions and preferences as described above apply equally to composites and articles comprising graphite.

Preferably, the composite has a porosity of about 10% to about 25%, more preferably about 15% to about 20%.

Preferably, the composite material has an apparent density of about 1.6g/cm ³ to about 1.92g/cm ³, more preferably about 1.7g/cm ³ to about 1.8g/cm ³.

In some embodiments, the composite of the present disclosure has a pore rate of about 15% to about 20%, a density of about 1.7g/cm ³ to about 1.8g/cm ³, and a total pore volume and pore size distribution in which at least 97% of the total pore volume is contained in pores less than 1 μm in diameter and at least 40% of the pore volume of pores less than 1 μm in diameter is contained in pores less than 0.1 μm in diameter.

Preferably, the composite of the invention comprises graphite in an amount of at least 65 weight percent, preferably at least 75 weight percent, more preferably at least 85 weight percent, relative to the total weight of the composite. In some embodiments, the composite of the present invention comprises graphite in an amount of about 65 weight percent to about 85 weight percent, preferably in an amount of about 75 weight percent to about 80 weight percent, relative to the total weight of the composite.

According to at least one embodiment, the composite material has a surface roughness R _a between 3.2 μm and 0.025 μm, wherein the surface roughness R _a is as provided in the ISO 1302:1992 standard.

Table 2 below provides equivalent values for Ra and N values as specified by the ISO 1302:1992 standard. Table 2 further provides Ra values in micro inches or μin under ANSI B46.1 standard optionally used in the united states.

TABLE 2

The following are some exemplary N-value descriptions provided according to ISO 1302:1992: n=10 (n10=12.5 μm) indicates rough turning with visible tool marks; n=8 (n8=3.2 μm) indicates a smooth machined surface; n=7 (n7=1.6 μm) indicates an interference fit surface (or datum); n=6 (n6=0.8 μm) indicates a bearing surface; and n=1 (n1=0.025 μm) indicates a very fine abrasive surface. In various embodiments, the surface roughness (Ra) value of the composite material of the present disclosure is a value between n=8 (n8=3.2 μm) and n=1 (n1=0.025 μm). In at least one embodiment, the "pressed" surface finish of the composite of the present disclosure varies between n=8 (3.2 μm) and n=1 (n1=0.025 μm); in other words, in at least one embodiment, the "pressed" surface finish of the composite material may vary between N1 (very fine abrasive surface) and N8 (smooth machined surface). In various embodiments, the composite may be capable of maintaining a polished mirror after proper finishing.

According to at least one embodiment, the composite material has a flexural strength of about 10MPa to 25MPa, with a flexural strength of 12MPa to 15MPa being even more preferred.

According to at least one embodiment, the graphite present in the composite material is registered graphite, wherein the graphite is registered in a predetermined direction. In some embodiments, registration of graphite in such articles is achieved by roll forming and similar other techniques. In one embodiment, the registration of the graphite is a result of the pattern or manner in which the 3D printhead moves when the article is 3D printed. In one embodiment, the registration of the graphite is a result of the manner in which the particulate mixture is extruded through the extrusion head. In one embodiment, the registration of the graphite is achieved by uniaxial pressing or isostatic pressing. In various embodiments, the presence of registered graphite may result in excellent resistance to metal attack and mechanical toughness. In some embodiments, the presence of registered graphite further provides a potential approach to improving the corrosion resistance of the article of manufacture to flux, slag, and metal attack. In various embodiments, by the method of forming registered graphite, a composite material comprising registered graphite may form an article exhibiting excellent corrosion resistance.

In various embodiments, the composite material further has a non-wetting surface.

According to at least one embodiment, the composite material is substantially final shaped.

In some embodiments, the carbon black, the graphite flakes, the needle coke, and the binder system provide 100% of the total weight of the particulate mixture. In such an embodiment, no other components (including the aforementioned "additives") are present in the particulate mixture of the present disclosure, other than carbon black, graphite flakes, needle coke, and binder system. In such an embodiment, when such a particulate mixture is formed into a shaped body composed of the particulate mixture, and the shaped body is fired to provide a composite material comprising graphite, the resulting composite material has a total carbon content of at least 99%.

According to at least one embodiment, the composite material has pores greater than 0.005 μm that are plugged with an antioxidant additive. According to at least one embodiment, the antioxidant additive in the article comprises a first antioxidant additive set comprising boron carbide, silicon carbide, aluminum zinc phosphate, or any combination thereof, and a second antioxidant additive set different from the first antioxidant additive set and comprising zinc phosphate, aluminum zinc phosphate, or any combination thereof.

Preferably, at least a portion of the composite material is further coated with a coating. In other words, at least a portion of the surface of the composite is coated with a coating. Advantageously, the coating is at least one selected from the group comprising: boron nitride, silicon carbide, aluminum oxide or aluminum titanate.

In some embodiments, the composite is impregnated with a siloxane, a selected phosphate solution, or any combination thereof.

In one embodiment, a composite material comprising graphite is obtained by the method of the present invention. According to at least one embodiment, the article is obtained from a composite material as detailed previously.

Drawings

Fig. 1 is a plot showing the particle size distribution of a particulate mixture according to the present disclosure prior to firing and the pore size distribution in a part after firing. In some embodiments, and as shown in fig. 1 (see leftmost side, e.g., labeled as particle size in 'graphite mixture'), the particulate mixture has a bimodal particle size distribution, wherein the first set of particles has a particle size diameter of about 50 μm to about 100 μm, and the second set of particles has a particle size diameter of about 110 μm to about 1000 μm. The first set of particles may constitute from about 30 to about 60 volume percent of the total particulate mixture, while the second set of particles may constitute from about 20 to about 40 volume percent of the total particulate mixture (as noted elsewhere in this disclosure, the particle size expressed herein is D50 particle size, i.e., half of the particles are above the expressed value and the other half of the particles are below the expressed value). Fig. 1 also shows the pore size distribution of an exemplary particulate mixture after firing.

Fig. 2A and 2B are SEM (scanning electron microscope) images of a composite structure of graphite, showing that the graphite in the composite structure is registered graphite, in accordance with an embodiment of the present disclosure. Fig. 2A and 2B are SEM images showing graphite composites comprising registered graphite prepared according to the present disclosure. The use of registration in graphite is well known in the manufacture of crucibles as containers for molten metal. In some embodiments, registration of graphite in such articles is achieved by roll forming and similar other techniques. In one embodiment, the registration of the graphite is a result of the pattern or manner in which the 3D printhead moves when the article is 3D printed. In one embodiment, the registration of the graphite is a result of the manner in which the particulate mixture is extruded through the extrusion head. In one embodiment, the registration of the graphite is achieved by uniaxial pressing or isostatic pressing. In various embodiments, the presence of registered graphite may result in excellent resistance to metal attack and mechanical toughness. In some embodiments, the presence of registered graphite further provides a potential approach to improving the corrosion resistance of the article of manufacture to flux, slag, and metal attack. In various embodiments, by the method of forming registered graphite, a composite material comprising registered graphite may result in a formed article exhibiting excellent corrosion resistance.

Fig. 3 is an SEM image of a composite material according to an embodiment of the present disclosure, wherein clay and aluminum zinc phosphate (Al) are located near needle coke. Fig. 3 is an SEM image of a composite material according to the present disclosure that includes zinc aluminum phosphate ((Al, zn) P) antioxidant additive located near needle coke (e.g., as a first stage antioxidant additive and/or as a second stage antioxidant additive). The SEM image shows that the addition of the antioxidant additive closes the pores of the composite structure, as shown in fig. 4. Notably, fig. 4 compares the pore size distribution of a base composite S1 according to the present disclosure with composite S2, S3, and S4 comprising various additives according to embodiments of the present disclosure. The base composite S1 is made of only a particulate mixture of carbon black, graphite flakes, needle coke and binder system, while the composite S2 is made of a particulate mixture of carbon black, graphite flakes, needle coke, binder system and (Al, zn) P, S3 is made of a particulate mixture of carbon black, graphite flakes, needle coke, binder system and (Al, zn) P, which is impregnated with silicone after firing, and the composite S4 is made of a particulate mixture of carbon black, graphite flakes, needle coke and binder system, which is impregnated with silicone after firing. Fig. 4 shows that the addition of (Al, zn) P to the particulate mixture of carbon black, graphite flakes, needle coke, and binder system closes the pores by forming a glass (compare S1 and S2) or similar other glazed or glaze-like layer, with a density varying from 1.64g/cm ³ for S1 to 1.67g/cm ³ for S2. Fig. 4 also shows that the impregnation of the siloxane into the particulate mixture of carbon black, graphite flakes, needle coke and binder system, with or without (Al, zn) P, closes all or most of the remaining pores (compare S3 and S2 and S1 and S4), with a change in density.

Fig. 4 is a plot comparing pore size distribution of a base composite according to the present disclosure and a composite comprising various additives according to embodiments of the present disclosure.

Fig. 5A and 5B are SEM images of a composite material including a toughening/strength enhancing additive according to embodiments of the present disclosure. Fig. 5A and 5B provide SEM images of a composite material including a toughening/strength enhancing additive (e.g., carbon fiber bundles) according to embodiments of the present disclosure. These SEM images show that the toughening/strength enhancing additive bonds well to the matrix graphite. Furthermore, the oxide cladding (oxidation package) ensures good bonding and silicone impregnation further enhances bonding. Carbon fiber bundles participate in the fracture process to provide long crack bridging or toughness reinforcement.

Fig. 6 is an SEM image of a composite material including an abrasion/erosion resistant agent according to an embodiment of the present disclosure. Fig. 6 is an SEM image of a composite material including an abrasion/erosion resistant agent (e.g., zirconia) according to an embodiment of the present disclosure. The addition of an abrasion/erosion resistant agent (e.g., zirconia) can react with the oxidation resistant additive to form erosion/oxidation resistant zircon (zirconium silicate, zrSiO ₄) and/or ZrSi glass.

Fig. 7 is a plot showing the pore size distribution of the composite material shown in fig. 6.

FIGS. 8A and 8B are SEM images of a composite material including a thermal insulation enhancer according to an embodiment of the disclosure; fig. 8A shows the thermal insulation enhancer dispersed in the particles of the particulate mixture for providing the composite material, while fig. 8B shows the thermal insulation enhancer located between the particles of the particulate mixture for providing the composite material. Fig. 8A shows the thermal insulation enhancer dispersed in the particles of the particulate mixture for providing composite material S5, while fig. 8B shows the thermal insulation enhancer located between the particles of the particulate mixture for providing composite material S6.

Fig. 9 is a plot showing the pore size distribution of the composite materials shown in fig. 8A (S5) and 8B (S6).

FIG. 10 is a bright phase image of a composite material including NiP according to an embodiment of the present disclosure.

FIG. 11 is a plot showing the pore size distribution of the composite of FIG. 10.

It should be noted that the pore diameters shown in fig. 1, 4, 7, 9 and 11 are based on mercury (Hg) intrusion analysis, as detailed previously.

Examples

Example 1:

In this example, the particulate mixture is composed entirely of 88.0 weight percent natural graphite flakes, 7.0 weight percent medium molecular weight phenolic resin powder, and 5.0 weight percent dibasic ester. The natural graphite flakes and phenolic resin are batched into a single hopper and then added to the mixer, at which point no dibasic ester is added. The dry ingredients were added to the blender and dry blended for approximately 2 minutes. After dry blending, the dibasic ester component is added and the mixer strength is increased. The mixing process continues for about 30-45 minutes until the particulate mixture is fully granulated. The bulk packing density of the granular mixture was measured to be about 0.51g/cm ³. After cooling to room temperature, the granular mixture was isostatically pressed at about 5,000 psi. The pressed shaped body had a green density of 1.6g/cm ³ and a very low green strength. The addition of phenolic resin and DBE results in a non-flowing powder that cannot be easily formed into a shaped body. Although the shaped body is cured at 200 ℃, this only leads to further weakening and eventually fracture of the shaped body.

Example 2:

In this example, the particulate mixture contains 76.0 weight percent natural graphite flakes, 7.5 weight percent carbon black, and a combination of 3.0 weight percent needle coke, 7.5 weight percent medium molecular weight phenolic resin powder, and 5.0 weight percent dibasic ester. The dry ingredients are batchwise placed into individual hoppers and then added to the mixer, where no dibasic ester is added. The dry ingredients were added to the blender and dry blended for approximately 2 minutes. After dry blending, the dibasic ester is added and the intensity of the mixer is increased. The mixing process is carried out for about 30-45 minutes until the particulate mixture is fully granulated. The bulk packing density of the mixture was measured to be about 0.65g/cm ³. After cooling to room temperature, the mixture was exposed to isostatic pressing at about 5,000 psi. The pressed shaped body had a green density of 1.7g/cm ³ and a green strength that was easy to handle. After pressing, the shaped body is cured at 200 ℃. The curing process results in cross-linking of the resin, which further increases the handling strength. The final firing cycle of exposing the cured shaped body to 1200 ℃ was continued for 4 hours. The resulting article includes an aperture profile as disclosed in the present disclosure. The surface roughness and profile were measured and as disclosed in the previous examples and figures, in particular fig. 2A and 2B.

Example 3:

This example was carried out according to the same process as example 2, except that the pressed shaped body was impregnated with a siloxane and/or phosphate solution after curing at 200 ℃ and fired once at 1200 ℃. The resulting composite (article) exhibits a pore size distribution as shown in fig. 4.

Example 4:

This example was performed according to the same process as example 2, except that the fired article was impregnated with a siloxane and/or phosphate solution. After drying, the impregnated article is subjected to a second firing at 1000 ℃ in a carbon-containing environment. The resulting composite (article) exhibits a pore size distribution as shown in fig. 4. Referring additionally to fig. 3, an SEM image of a composite according to this example is shown in which clay and aluminum zinc phosphate are located near needle coke.

The inventors noted that the impregnation treatment helps to prevent oxidation of the carbon fibers during field application and also results in many coarser pore closures and thus in articles with increased density.

Example 5:

In this example, the particulate mixture contains 76.0 weight percent natural graphite flakes, 7.5 weight percent carbon black, and a combination of 3.0 weight percent needle coke, 13.0 weight percent liquid medium molecular weight phenolic resin mixture. The liquid phenolic resin is prepared by premixing the phenolic resin with a dibasic ester in a ratio of 70:30 or with ethylene glycol in a ratio of 55:45. The dry ingredients were placed in batches into individual hoppers and then added to the mixer and dry blended in the mixer for approximately 2 minutes. After dry blending, the resin is added to the mixer and the strength of the mixer is increased. The mixing process is carried out for about 30-45 minutes until the particulate mixture is fully granulated. The bulk packing density of the granular mixture was measured to be about 0.65g/cm ³. After cooling to room temperature, the mixture was exposed to isostatic pressing at about 5,000 psi. The pressed shaped body had a green density of 1.7g/cm ³ and a green strength that was easy to handle. After pressing, the shaped bodies were transferred to a kiln and cured at 200 ℃. The curing process results in cross-linking of the resin, which further increases the handling strength. The final firing cycle of exposing the cured shaped body to 1200 ℃ was continued for 4 hours. The resulting article includes an aperture profile as disclosed in the present disclosure. The surface roughness and profile were measured and as disclosed in the previous examples and figures.

Example 6:

This example was carried out according to the same process as in example 5, except that the pressed shaped body was impregnated with a siloxane and/or phosphate solution after curing at 200 ℃ and fired once at 1200 ℃. The resulting article includes an aperture profile as disclosed in the present disclosure. The surface roughness and profile were measured and as disclosed in this patent application.

Example 7:

This example was performed according to the same process as example 5, except that the fired article was impregnated with a siloxane and/or phosphate solution. After drying, the impregnated article is subjected to a second firing at 1000 ℃ in a carbon-containing environment. The inventors noted that the impregnation treatment helps to prevent oxidation of the carbon fibers during field application and also results in many coarser pore closures and thus in articles with increased density.

Example 8:

In this example, the particulate mixture contains a combination of 70.0 weight percent natural graphite flakes, 6.0 weight percent carbon black, and 2.0 weight percent needle coke, 5.0 weight percent boron carbide, 3.3 weight percent silicon carbide, 7.0 weight percent medium molecular weight phenolic resin powder, and 5.0 weight percent dibasic ester. In this example, zirconia powder was added to the dry component in an amount of 1.7 weight percent. The dry ingredients are batchwise placed into individual hoppers and then added to the mixer, where no dibasic ester is added. The dry ingredients were added to the blender and dry blended for approximately 2 minutes. After dry blending, the dibasic ester was added to the mixer and the strength of the mixer was increased. The mixing process is carried out for about 30-45 minutes until the particulate mixture is fully granulated. The bulk packing density of the mixture was measured to be about 0.68g/cm ³. After cooling to room temperature, the granular mixture was isostatically pressed at about 5,000 psi. The pressed shaped body had a green density of 1.75g/cm ³ and a green strength that was easy to handle. After pressing, the shaped body is cured at 200 ℃. The curing process results in cross-linking of the resin, which further increases the handling strength. The final firing cycle of exposing the cured shaped body to 1200 ℃ was continued for 4 hours. Referring to fig. 6, this figure is an SEM image of a composite material comprising an abrasion/erosion resistant agent according to this example. The resulting article comprises the aperture profile as shown in fig. 7. The inventors found that zirconia powder provided the resulting article with greater wear resistance.

Example 9:

This example was carried out according to the same process as in example 8, except that the pressed shaped body was impregnated with a siloxane and/or phosphate solution after curing at 200 ℃ and fired once at 1200 ℃. The resulting article includes an aperture profile as disclosed in the present disclosure. The surface roughness and profile were measured and as disclosed in the previous examples and figures.

Example 10:

This example was performed according to the same process as example 8, and the fired article was impregnated with a siloxane and/or phosphate solution. After drying, the impregnated article is subjected to a second firing at 1000 ℃ in a carbon-containing environment.

Example 11:

In this example, the particulate mixture contains a combination of 70.0 weight percent natural graphite flakes, 6.0 weight percent carbon black, and 2.0 weight percent needle coke, 5.0 weight percent boron carbide, 3.3 weight percent silicon carbide, 7.0 weight percent medium molecular weight phenolic resin powder, and 5.0 weight percent dibasic ester. The dry ingredients are batchwise placed into individual hoppers and then added to the mixer, where no dibasic ester is added. The dry ingredients were added to the blender and dry blended for approximately 2 minutes. After dry blending, the dibasic ester was added to the mixer and the strength of the mixer was increased. The mixing process is carried out for about 30-45 minutes until the particulate mixture is fully granulated. An amount of 1.7wt.% of the insulation aluminum silicate fiber was added and mixing was continued for an additional 1 or 2 minutes. The bulk packing density of the granular mixture was measured to be about 0.63g/cm ³. After cooling to room temperature, the granular mixture was isostatically pressed at about 5,000 psi. The pressed shaped body had a green density of 1.72g/cm ³ and a green strength that was easy to handle. After pressing, the shaped body is cured at 200 ℃. The curing process results in phenolic resin crosslinking, which further increases the handling strength. The final firing cycle of exposing the cured shaped body to 1200 ℃ was continued for 4 hours. Referring to fig. 8A and 8B, SEM images of the composite obtained according to this example are shown; fig. 8A shows the thermal insulation enhancer dispersed in the particles of the particulate mixture for providing the composite material, while fig. 8B shows the thermal insulation enhancer located between the particles of the particulate mixture for providing the composite material. The pore size distribution of the composite is shown in fig. 9.

Example 12:

This example was carried out according to the same process as in example 11, except that the pressed shaped body was impregnated with a siloxane and/or phosphate solution after curing at 200 ℃ and fired once at 1200 ℃. The resulting article includes an aperture profile as disclosed in the present disclosure. The surface roughness and profile were measured and as disclosed in the previous examples and figures.

Example 13:

this example was performed according to the same process as example 11, except that the fired article was impregnated with a siloxane and/or phosphate solution. After drying, the impregnated article is subjected to a second firing at 1000 ℃ in a carbon-containing environment.

The inventors noted that the infiltration treatment caused a majority of the coarser pores to close and thus resulted in articles with increased density.

Example 14:

In this example, the particulate mixture contains a combination of 70.0 weight percent natural graphite flakes, 6.0 weight percent carbon black, and 2.0 weight percent needle coke, 5.0 weight percent boron carbide, 3.5 weight percent silicon carbide, 7.0 weight percent medium molecular weight phenolic resin powder, and 5.0 weight percent dibasic ester. The dry ingredients are batchwise placed into individual hoppers and then added to the mixer, where no dibasic ester is added. The dry ingredients were added to the blender and dry blended for approximately 2 minutes. After dry blending, the dibasic ester was added to the mixer and the strength of the mixer was increased. The mixing process is carried out for about 30-45 minutes until the particulate mixture is fully granulated. 1.5wt.% of chopped carbon fiber bundles 6mm in length and 3mm in width were added and mixing was continued for an additional 1 to 2 minutes. The bulk packing density of the granular mixture was measured to be about 0.63g/cm ³. After cooling to room temperature, the granular mixture was isostatically pressed at about 5,000 psi. The pressed shaped body had a green density of 1.72g/cm ³ and a green strength that was easy to handle. After pressing, the shaped body is cured at 200 ℃. The curing process results in phenolic resin crosslinking, which further increases the handling strength. The final firing cycle of exposing the cured shaped body to 1200 ℃ was continued for 4 hours. Referring to fig. 5A and 5B, SEM images of a composite material including a toughening/strength enhancing additive according to embodiments of the present disclosure are shown.

The inventors have observed that both the strength and toughness of the present article are increased compared to graphite articles that do not comprise carbon fibers. The carbon fiber bundles were found to bind tenaciously to the graphite and participate in the fracture mechanism. The surface roughness and profile were measured and as disclosed in the previous examples and figures.

Example 15:

This example was carried out according to the same process as in example 14, except that the pressed shaped body was impregnated with a siloxane and/or phosphate solution after curing at 200 ℃ and fired once at 1200 ℃.

Example 16:

This example was performed according to the same process as example 14, except that the fired article was impregnated with a siloxane and/or phosphate solution. After drying, the article is subjected to a second firing in a carbon-containing environment at 1000 ℃.

The inventors have noted that the impregnation treatment is very important to prevent oxidation of the carbon fibers during field application. As reported in the previous examples, the infiltration process also caused a majority of the coarser pores to close and thus resulted in articles with increased density.

While the present disclosure has been particularly shown and described with respect to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the present disclosure. It is therefore intended that the present disclosure not be limited to the exact forms and details described and illustrated, but fall within the scope of the appended claims.

Claims

1. A method of forming an article comprising a composite material containing graphite, wherein the article is suitable for containing or processing molten metal, the method comprising the steps of:

(a) forming at least one pelletized mixture by mixing at least carbon black, flake graphite, needle coke and at least one resin, wherein the at least one resin has a flow distance of 20 mm to 150 mm as measured by ISO 8619:2003;

(b) shaping the at least one particulate mixture into at least one shaped body; and

(c) firing the at least one shaped body.

2. The method of claim 1, wherein, relative to the total weight of the granular mixture:

The carbon black is present in the particulate mixture in an amount of about 5 weight percent to about 10 weight percent, preferably in an amount of about 5 weight percent to about 8 weight percent,

The flake graphite is present in the particulate mixture in an amount of about 65 weight percent to about 85 weight percent, preferably about 75 weight percent to about 80 weight percent,

The needle coke is present in the particulate mixture in an amount of about 1 weight percent to about 5 weight percent, preferably about 2 weight percent to about 4 weight percent, and

The resin is present in the granular mixture in an amount of about 2 weight percent to about 10 weight percent, preferably about 6 weight percent to about 8 weight percent.

3. The method of claim 1 or 2, wherein at least one solvent is added to the at least one resin to form at least one binder system consisting of the at least one resin and the at least one solvent.

4. The method of claim 3, wherein the at least one solvent is present in the granular mixture in an amount of about 1 weight percent to about 5 weight percent, preferably about 3 weight percent to about 4 weight percent, relative to the total weight of the granular mixture.

5. The method of any one of claims 1 to 4, wherein the at least carbon black, the flake graphite, the needle coke and the at least one resin provide 100% of the total weight of the particulate mixture.

6. The method of any one of claims 1 to 5, wherein the at least one granular mixture further comprises about 5 weight percent to about 15 weight percent of at least one antioxidant additive relative to the total weight of the granular mixture, wherein optionally, the at least one antioxidant additive comprises boron carbide, silicon carbide, aluminum zinc phosphate, or any combination thereof.

7. The method of any one of claims 1 to 6, wherein the at least one granular mixture further comprises from about 1 weight percent to about 5 weight percent of at least one toughening/strength enhancing additive relative to the total weight of the granular mixture, wherein optionally, the at least one toughening/strength enhancing additive comprises carbon fibers, chopped carbon fiber bundles, basalt bundles, aluminum silicate fibers, chopped steel fibers, or any combination thereof.

8. The method of any one of claims 1 to 7, wherein the granular mixture further comprises from about 1 weight percent to about 10 weight percent of at least one wear/erosion resistant agent relative to the total weight of the granular mixture, wherein optionally, the at least one wear/erosion resistant agent comprises a metal oxide, a metal nitride, a metal boride, or any combination thereof.

9. The method of any one of claims 1 to 8, wherein the at least one granular mixture further comprises from about 1 weight percent to about 5 weight percent of an insulation enhancer relative to the total weight of the granular mixture, and wherein optionally, the at least one insulation enhancer comprises colloidal silica pellets, preferably aluminum colloidal silicate pellets, a mixture of fibers, preferably sodium and chopped silica fibers, or a mixture thereof.

10. The method of any one of claims 1 to 9, wherein at least a portion of the composite material is infiltrated with siloxane, a selected phosphate solution, or any combination thereof, before or after the firing step.

11. The method of any one of claims 10 to 10, wherein the resin is a phenolic resin, wherein optionally the phenolic resin is a liquid phenolic resin.

12. An article comprising a composite material containing graphite, wherein the composite material has a total pore volume and a pore size distribution measured according to ASTM C830-00 (2016) standard, wherein at least 95% of the total pore volume is contained in pores with a diameter less than 1 μm, and at least 40% of the pore volume of pores with a diameter less than 1 μm is contained in pores with a diameter less than 0.1 μm.

13. The article of claim 12, wherein the composite material has a density of about 1.6 g/ ^cm3 to about 1.92 g/ ^cm3 .

14. The article of claim 12 or 13, wherein the composite material has a graphite content of 65% or more.

15. The article of any one of claims 12 to 14, wherein the composite material has a surface roughness _Ra between 3.2 μm and 0.025 μm, wherein the surface roughness _Ra is measured based on ISO 1302:1992 standard.

16. The article of any one of claims 12 to 15, wherein at least a portion of the composite material is further coated with a coating, wherein the coating is preferably at least one coating selected from the group consisting of boron nitride, silicon carbide, aluminum oxide or aluminum titanate.

17. The article of any one of claims 12 to 16, wherein the article is a crucible, the crucible being composed of a plurality of crucible rings uniformly stacked on top of each other to provide the crucible.

18. An article comprising a composite material comprising graphite obtained by the method according to any one of claims 1 to 11.

19. The article of claim 18, wherein the composite material has a total pore volume and pore size distribution measured according to ASTM C830-00 (2016) standard, wherein at least 95% of the total pore volume is contained in pores having a diameter less than 1 μm, and at least 40% of the pore volume of pores having a diameter less than 1 μm is contained in pores having a diameter less than 0.1 μm.

20. The article of claim 18 or claim 19, wherein at least a portion of the composite material is further coated with a coating, wherein the coating is preferably at least one coating selected from the group consisting of boron nitride, silicon carbide, aluminum oxide or aluminum titanate.

21. The article of any one of claims 18 to 20, wherein the article is a crucible, the crucible being composed of a plurality of crucible rings uniformly stacked on top of each other to provide the crucible.