Method for producing carbonized or graphitized shaped parts

Abstract

The invention relates to a method for producing carbonized or graphitized shaped parts. The object of the invention is to provide a method for producing carbonized or graphitized shaped parts, which is particularly easy to implement and also allows the production of complex shaped parts without mechanical post-processing. This object is achieved by preparing a pourable liquid polymer mixture as homogenized as possible, which consists of carbon particles, pitch, carbon black or graphite powder and polyacrylonitrile dissolved in a solvent, filling the liquid polymer mixture into a casting mold and immersing the filled casting mold into water for a predetermined period of time until the polymer mixture is sufficiently solidified and dimensionally stable, and subsequently detaching from the casting mold and stabilizing the preformed solidified shaped part by uniform heating in an oven in air at a predetermined temperature for stabilization and outgassing of volatile components, and high-temperature treatment in a furnace under a protective gas for carbonization or graphitization of the shaped part.

Description

Technical Field

[0001] This invention relates to a method for producing carbonized or graphitized molded parts.

[0002] These carbonized or graphitized molded parts are also suitable for high-temperature applications and can be any desired three-dimensional component, such as furnace linings, structural parts, or any desired hollow body, container, or crucible. Background Technology

[0003] Since it is not possible to produce molded parts by simply molding carbon black or graphite and then sintering them, it is usually necessary to produce suitable carbon-containing and moldable compounds. For this purpose, carbon black, coke, or graphite in granular form is typically mixed with a suitable binder (e.g., a thermoplastic binder). Useful binders also include pitch based on coal tar or petroleum pitch, or other synthetic resins.

[0004] These mixtures are then molded into green bodies by pressing and carbonizing in a furnace at approximately 3000°C, where the binder decomposes into volatile components. Carbon and binder coke remain as binder residues in a porous structure.

[0005] Alternatively, the green molded part can be arranged as a resistive element in a furnace between electrodes and heated by an electric current. Summary of the Invention

[0006] The purpose of this invention is to provide a method for producing carbonized or graphitized molded parts, which is particularly easy to implement and can also produce complex molded parts without mechanical post-processing.

[0007] This is achieved by: preparing a liquid polymer mixture, which is homogenized as much as possible and consists of carbon particles, pitch, carbon black or graphite powder, and fibrous materials, cellulose, starch, and polyacrylonitrile dissolved in an organic solvent; pouring the pourable polymer mixture into a casting mold; immersing the filled casting mold in water for a defined period of time until the polymer mixture has solidified to form a molded part and is dimensionally stable; subsequently removing the casting mold and stabilizing the pre-formed hardened molded part by heating it in an air atmosphere to a defined temperature in a furnace to stabilize and degas volatile components in the molded part; and subjecting the molded part to high-temperature treatment in a furnace under a protective gas or reduced pressure to carbonize or graphitize the molded part.

[0008] In order to influence the strength or porosity of the carbonized or graphitized molded parts to be produced, the polymer mixture can be mixed with natural fibers as fibrous materials, such as bamboo fibers or graphite fibers.

[0009] The polymer mixture is homogenized at room temperature, at approximately 160°C, and if the mixture contains high-temperature asphalt with a melting point of 120°C, until it melts.

[0010] In a continuation of the invention, a casting mold filled with a polymer mixture is immersed in water for several hours or days to solidify and form a molded part. After the molded part has solidified, it can be removed from the mold.

[0011] Subsequently, the pre-cured molded part is stabilized and homogenized in air at a stable temperature of 140°C to a maximum of 450°C, preferably at 250°C.

[0012] Pre-formed hardened molded parts can be stabilized and homogenized during the process of heating the furnace to a stable temperature.

[0013] In a further process, the pre-formed parts are carbonized at a constant temperature of approximately 1000°C until pure carbon with different crystal structures is formed.

[0014] In another continuation of the invention, the preformed part is graphitized at a constant temperature of 2000°C.

[0015] Finally, the pre-formed parts can be fully graphitized at temperatures above 2500°C.

[0016] Clearly, carbonization, graphitization, and complete graphitization each proceed under a protective gas. Suitable protective gases are argon or helium.

[0017] Preferably, graphitization is carried out at a heating slope of 1°C / min until the target temperature is reached, followed by tempering for about 30 minutes, or tempering for several hours.

[0018] In principle, polymer mixtures can also be mixed with metal powders or silicon powders to form metal carbides or silicon carbides during high-temperature treatment of pre-molded parts at >1000°C under a protective gas atmosphere.

[0019] Due to the relatively low health hazards, dimethyl sulfoxide is preferred as a solvent for polyacrylonitrile. In principle, dimethylformamide or N-methyl-2-pyrrolidone are also suitable as solvents. Detailed Implementation

[0020] The present invention will now be explained in more detail based on exemplary embodiments.

[0021] The basic concept of this invention is to first produce a pourable liquid that is easy to handle and can be easily poured into a casting mold.

[0022] To this end, a polymer mixture consisting of polyacrylonitrile dissolved in a solvent (e.g., dimethyl sulfoxide) is prepared, and then mixed with pitch and / or carbon black and / or graphite powder and fibrous materials, cellulose, etc., until the mixture has a pourable consistency.

[0023] The mixture is then homogenized at room temperature, or at approximately 160°C if the mixture contains bitumen to melt the bitumen.

[0024] The homogenized mixture is then poured into a casting mold, which is then completely immersed in water until the mixture has fully solidified and reached dimensional stability. This process may take several hours or days, depending on the mixing ratio.

[0025] Subsequently, the molded part is removed from the casting mold and stabilized as a precast, hardened part.

[0026] This is carried out in air at a stable temperature of 140°C to a maximum of 450°C (preferably at 250°C), or possibly by stabilizing the preformed part while heating the furnace to a stable temperature.

[0027] The preformed parts in this way are then carbonized at a constant temperature of about 1000°C until pure carbon with different crystal structures is formed.

[0028] The preformed part can then be graphitized at a constant temperature of 2000°C, or fully graphitized at a temperature above 2500°C.

[0029] To avoid thermal stress, graphitization is preferably carried out at a heating rate of 1°C / min until the target temperature is reached, followed by tempering for about 30 minutes.

[0030] It can be said that the method according to the present invention yields three products: a molded part made of carbon, graphite with different structures, and pure graphite.

[0031] Alternatively, the polymer mixture can be mixed with metal powder or silicon powder to form metal carbides or silicon carbides during high-temperature treatment of preformed parts at temperatures >1000°C, thereby enabling the production of more products.

[0032] The advantage of the method according to the invention is that it is easy to process and can also produce complex molded parts without mechanical post-processing.

Claims

1. A method for producing carbonized or graphitized molded parts, characterized in that, Prepare pourable, homogenized polymer mixtures. The polymer mixture consists of polyacrylonitrile dissolved in an organic solvent, which is mixed with fibrous materials, cellulose, starch, and one or more of the following: pitch, carbon black, or graphite powder, until the polymer mixture has a pourable consistency. The polymer mixture is homogenized at room temperature, or if the polymer mixture contains bitumen, the mixture is homogenized at 160°C. Pour the pourable, homogenized polymer mixture into a casting mold. The casting mold filled with the polymer mixture is completely immersed in water for a defined period of several hours to several days, until the polymer mixture in the casting mold has solidified to form a molded part and is dimensionally stable. The defined period of complete immersion in water depends on the mixing ratio of the polymer mixture. The molded part is then removed from the casting mold and stabilized by heating in an air-atmosphere furnace to temperatures between 140°C and 450°C. This process stabilizes the part and degassing volatile components. High-temperature treatment is carried out in a furnace under protective gas or reduced pressure to carbonize the molded parts at a constant temperature of 1000°C or graphitize them at a constant temperature of 2000°C.

2. The method of claim 1, wherein, The polymer mixture is mixed with natural fibers as fibrous materials, wherein the natural fibers are bamboo fibers or graphite fibers.

3. The method according to claim 1 or 2, characterized in that, The pre-formed hardened molded parts are stabilized and homogenized at a temperature of 250°C.

4. The method of claim 3, wherein, During the process of heating the furnace to a stable temperature, the pre-formed hardened molded parts are stabilized and homogenized.

5. The method according to claim 1 or 2, characterized in that, The pre-formed parts are carbonized at a constant temperature of 1000℃ until pure carbon with different crystal structures is formed.

6. The method of claim 1 or 2, wherein, The pre-formed parts are graphitized at a constant temperature of 2000℃.

7. The method of claim 1 or 2, wherein, The pre-formed parts are fully graphitized at temperatures above 2500°C.

8. The method of claim 6, wherein, Graphitization was carried out at a heating slope of 1℃ / min until the target temperature was reached, and then tempered for more than 30 minutes.

9. The method of claim 1, wherein, The solvent used is dimethyl sulfoxide, dimethylformamide, or N-methyl-2-pyrrolidone.