Method for producing carbonized or graphitized molding parts

Abstract

A method for producing carbonized or graphitized molding parts is particularly simple to implement and also allows producing complex molding parts without mechanical post-processing. This is achieved by the production of a pourable liquid polymer mixture which is as homogenized as possible, consisting of a carbon granulate, pitch, soot or graphite powder and polyacrylnitrile dissolved in a solvent, filling the liquid polymer mixture into a casting mold and immersing the filled casting mold in water over a predetermined period of time until the polymer mixture is sufficiently cured and dimensionally stable, and subsequent breaking of the casting mold and stabilizing the prefabricated cured molding part by uniform heating up in a furnace in air at a predefined temperature for stabilizing and degassing volatile constituents, and performing a high-temperature treatment for carbonizing or graphitizing the molding part in a furnace under protective gas.

Claims

1.-11. (canceled)

12. A method for producing carbonized or graphitized moldings, comprising: producing a pourable homogenized polymeric mixture, consisting of polyacrylonitrile, dissolved in an organic solvent, which is admixed with carbon granules, pitch, carbon black, or graphite powder, and fibrous materials, cellulose, or starch until the mixture has a pourable consistency; homogenizing the mixture at room temperature, or at 160? C. if the mixture comprises pitch; pouring the pourable homogenized polymeric mixture into a casting mold; completely immersing the casting mold filled with the polymeric mixture in water for a defined period of time of several hours to days until the polymeric mixture in the casting mold has cured to form a prefabricated hardened molding and is dimensionally stable; subsequently breaking away the casting mold and stabilizing the prefabricated hardened molding by heating in a furnace in an air atmosphere to a stabilization temperature of 140? C. to 450? C. for stabilization and outgassing of volatile constituents from the molding; and carrying out a high-temperature treatment in order to carbonize at a constant temperature of 1000? C. or graphitize the molding at a constant temperature from 2000? C. in a furnace under protective gas or reduced pressure.

13. The method as claimed in claim 12, wherein the fibrous materials are bamboo fibers or graphite fibers.

14. The method as claimed in claim 12, wherein the polymeric mixture is homogenized at room temperature, the homogenization of the polymeric mixture being performed at 160? C. if pitch is admixed until the pitch has melted.

15. The method as claimed in claim 12, wherein the casting mold filled with the polymeric mixture is immersed in water for several hours or days in order to cure and form a molding.

16. The method as claimed in claim 12, wherein the prefabricated hardened molding is stabilized and homogenized at a temperature of 250? C.

17. The method as claimed in claim 16, wherein the prefabricated hardened molding is stabilized and homogenized during the heating of the furnace to the stabilization temperature.

18. The method as claimed in claim 12, wherein the prefabricated hardened molding is carbonized at a constant temperature of 1000? C. until pure carbon with a different crystal structure is formed.

19. The method as claimed in claim 12, wherein the prefabricated hardened molding is graphitized at a constant temperature from 2000? C.

20. The method as claimed in claim 12, wherein the prefabricated hardened molding is fully graphitized at a temperature of above 2500? C.

21. The method as claimed in claim 19, wherein the graphitization is effected with a heating ramp of 1? C./min until the constant temperature has been reached, followed by tempering for >30 min.

22. The method as claimed in claim 12, wherein the solvent used is dimethyl sulfoxide, dimethylformamide or N-methyl-2-pyrrolidone.

Description

DETAILED DESCRIPTION

[0021] The method is explained in more detail below on the basis of an exemplary embodiment.

[0022] The basic concept of the method is that of first producing a pourable liquid that is easy to handle and can easily be cast into a casting mold.

[0023] For this purpose, a polymeric mixture consisting of polyacrylonitrile dissolved in a solvent, such as dimethyl sulfoxide, is produced, with pitch and/or carbon black and/or graphite powder and fibrous materials, cellulose etc. subsequently being admixed until the mixture has a pourable consistency.

[0024] This mixture is then homogenized at room temperature, or at approx. 160? C. if the mixture comprises pitch in order to melt the pitch.

[0025] The homogenized mixture is subsequently poured into a casting mold which is then completely immersed in water until the mixture has sufficiently cured and is dimensionally stable. This procedure can last several hours or a few days, this depending on the mixing ratio of the mixture.

[0026] Following this, the casting mold can be broken away and the prefabricated hardened molding can be stabilized.

[0027] This is effected in air at a stabilization temperature of 140? C. to at most 450? C., preference being given to a temperature of 250? C., it also being possible for the prefabricated molding to be stabilized during the heating of the furnace to the stabilization temperature.

[0028] The molding prefabricated in this way is subsequently carbonized at a constant temperature of approx. 1000? C. until pure carbon with a different crystal structure is formed.

[0029] It is also possible to then graphitize the prefabricated molding at a constant temperature from 2000? C., or to fully graphitize it at a temperature of above 2500? C.

[0030] To avoid thermal stresses, the graphitization is preferably effected with a heating ramp of 1? C./min until the target temperature has been reached, followed by tempering for approx. 30 min.

[0031] The method results, so to speak, in three products, namely moldings made of carbon, graphite with a different structure and full graphite in a pure structure.

[0032] Alternatively, the polymeric mixture can also be admixed with a metal powder or silicon powder, so that metal carbides or silicon carbides are formed in a high-temperature treatment of the prefabricated molding at >1000? C., which enables further production of further products.

[0033] The advantage of the method lies in the ease of handling and in the possibility of also being able to produce complex moldings without machine finishing.