Obtaining fiber textures of carbon by carbonizing a cellulose precursor

1. A method of obtaining a fiber texture of carbon from a cellulose precursor, the method including the steps of:

spinning cellulose filaments from a viscose solution or a cellulose solution;

subjecting the cellulose filaments to washing in water;

subsequently impregnating the washed and non-dried cellulose filaments with an aqueous emulsion of at least one carbonization-enhancing organosilicon additive;

drying the impregnated cellulose filaments to obtain dried cellulose filaments provided with said carbonization-enhancing organosilicon additive;

making a fiber texture made up of said impregnated and dried cellulose filaments provided with said carbonization-enhancing organosilicon additive, the making of the fiber texture including a step of forming a yarn or unidirectional sheet from a plurality of said impregnated and dried cellulose filaments; and

carbonizing the fiber texture.

2. A method according to claim 1 , wherein the aqueous emulsion includes 5% to 50% by weight of organosilicon additive(s).

3. A method according to claim 1 , wherein, after being impregnated by the aqueous emulsion and prior to drying, the filaments are squeezed so as to obtain a water content lying in the range 10% to 50% by weight of the dry filaments.

4. A method according to claim 1 , wherein the organosilicon additive content lies in the range 1.5% to 15% by weight relative to the total weight of the filaments after drying.

5. A method according to claim 1 , wherein, after drying and prior to carbonization, a yarn is formed by twisting a plurality of impregnated and dried filaments.

6. A method according to claim 1 , wherein, after drying and prior to carbonization, a unidirectional fiber sheet is formed comprising a plurality of impregnated and dried filaments disposed substantially in parallel with one another.

7. A method according to claim 5 , wherein, prior to carbonization, a unidirectional sheet is formed comprising a plurality of yarns disposed substantially parallel to one another.

8. A method according to claim 6 , wherein the carbonization includes a stage of slow pyrolysis during which the temperature is raised progressively up to a value lying in the range 360° C. to 750° C.

9. A method according to claim 8 , wherein, during the slow pyrolysis stage, tension is applied to the yarn or the unidirectional sheet so that the variation in longitudinal dimension after pyrolysis lies in the range −30% to +40%.

10. A method according to claim 5 , wherein, prior to carbonization, a bidimensional or tridimensional fiber texture is formed by weaving, knitting or braiding yarns formed from impregnated and dried filaments.

11. A method according to claim 10 , wherein the carbonization includes a stage of slow pyrolysis during which the temperature is raised progressively up to a value lying in the range 360° C. to 750° C.

12. A method according to claim 8 , wherein, after the slow pyrolysis stage, a stage of final carbonization is performed by heat treatment at high temperature lying in the range 1200° C. to 2800° C.

13. A method according to claim 12 , wherein, during the high temperature final carbonization stage, tension is applied to the fiber texture in such a manner as to obtain elongation of not more than 200% in the longitudinal direction.

14. A method according to claim 12 , wherein, subsequently to a final carbonization stage at a temperature greater than 2500° C., the fiber texture is subjected to a further heat treatment at a temperature greater than 2500° C. and for a duration of at least 15 minutes to cause development of whiskers within the carbon fibers of the yarn or unidirectional sheet.

15. A method according to claim 8 , wherein, prior to slow pyrolysis, a relaxation stage is performed in air at a temperature lower than 200° C.

16. A method according to claim 15 , characterized in that the relaxation stage is performed at a temperature lying in the range 160° C. to 190° C.

17. A method according to claim 2 , wherein:

after being impregnated by the aqueous emulsion and prior to drying, the filaments are squeezed so as to obtain a water content lying in the range 10% to 50% by weight of the dry filaments;

the organosilicon additive content lies in the range 1.5% to 15% by weight relative to the total weight of the filaments after drying;

after drying and prior to carbonization, either a yarn is formed by twisting a plurality of impregnated and dried filaments, or a unidirectional fiber sheet is formed comprising a plurality of impregnated and dried filaments disposed substantially in parallel with one another;

the carbonization includes a stage of slow pyrolysis during which the temperature is raised progressively up to a value lying in the range 360° C. to 750° C.;

during the slow pyrolysis stage, tension is applied to the yarn or the unidirectional sheet so that the variation in longitudinal dimension after pyrolysis lies in the range −30% to +40%;

after the slow pyrolysis stage, a stage of final carbonization is performed by heat treatment at high temperature lying in the range 1200° C. to 2800° C.