Method for producing ceramic fibers of a composition in the sic range and for producing sic fibers

Abstract

A method for producing ceramic fibers of a composition in the SiC range, starts from a spinning material that contains a polysilane-polycarbosilane copolymer solution. The spinning material is extruded through spinnerets in a dry spinning method and spun through a spinning duct into green fibers, and the green fibers are subsequently pyrolyzed. Accordingly, the polysilane-polycarbosilane solution contains between 75 wt. % and 95 wt. %, in particular between 80 and 90 wt. %, of an indifferent solvent, and the spinnerets have a capillary diameter between 20 and 70 μm, in particular between 30 and 60 μm, in particular between 40 and 50 μm.

1 . A method for producing ceramic fibers with a composition in an SiC range formed from a spin dope containing a polysilane-polycarbosilane copolymer solution, which comprises the steps of:
 providing the spin dope containing the polysilane-polycarbosilane copolymer solution in a range 75% by weight to 95% by weight of an inert solvent;   extruding the spin dope through spin nozzles in a dry spinning process and spun through a spinning duct resulting in green fibers, the spin nozzles having a capillary diameter in a range 20 to 70 μm; and   pyrolyzing the green fibers resulting in pyrolyzed fibers.   
     
     
         2 . The method according to  claim 1 , which further comprises carrying out the dry spinning process at a draw rate in a of range 50 m/min to 1,000 m/min. 
     
     
         3 . The method according to  claim 1 , which further comprises setting a viscosity of the spin dope in a range of 0.1 to 6 Pas. 
     
     
         4 . The method according to  claim 1 , which further comprises carrying out the dry spinning process with 50 to 50,000 spin nozzles. 
     
     
         5 . The method according to  claim 1 , which further comprises carrying out the dry spinning process at shear rates in a range of 10,000 s −1  to 60,000 s −1 . 
     
     
         6 . The method according to  claim 1 , wherein the spin dope contains a spinning aid selected from the group consisting of polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyacrylonitrile and poly(4-vinyl pyridine). 
     
     
         7 . The method according to  claim 6 , which further comprises supplying a spinning aid fraction having a 0.5% to 10% by weight. 
     
     
         8 . The method according to  claim 1 , which further comprises setting a spinning duct temperature to be in a range of 40° C. to 160° C. 
     
     
         9 . The method according to  claim 8 , which further comprises flushing the spinning duct with an inert flushing gas that is free of solvent. 
     
     
         10 . The method according to  claim 9 , which further comprises moving the inert flushing gas in a same direction as the ceramic fibers. 
     
     
         11 . The method according to  claim 1 , which further comprises selecting the inert solvent from a saturated hydrocarbon selected from the group consisting of n-pentane, n-hexane, cyclohexane, n-heptane, n-octane, and an aromatic hydrocarbon selected from the group consisting of benzene, toluene, o-xylene, syn-mesitylene, a chlorinated hydrocarbon selected from the group consisting of methylene chloride, chloroform, carbon tetrachloride, 1,1,1-trichloroethane, chlorobenzene and an ether selected from the group consisting of diethyl ether, diisopropyl ether, tetrahydrofuran, 1,4-dioxane and a mixture of at least two these inert solvents. 
     
     
         12 . The method according to  claim 1 , which further comprises carrying out the pyrolyzing step in one of an inert atmosphere or in a reducing atmosphere at temperatures in the range 700° C. to 1,700° C. 
     
     
         13 . The method according to  claim 1 , which further comprises sintering the pyrolyzed fibers at temperatures in a range of 1,000° C. to 1,500° C. 
     
     
         14 . The method according to  claim 1 , which further comprises:
 providing the polysilane-polycarbosilane copolymer solution in a range 80% by weight to 90% by weight of the inert solvent; and   providing the spin nozzles to have the capillary diameter in a range 40 to 50 μm.   
     
     
         15 . The method according to  claim 1 , which further comprises carrying out the dry spinning process at a draw rate in a range of 100 to 750 m/min. 
     
     
         16 . The method according to  claim 1 , which further comprises carrying out the dry spinning process at a draw rate in a range of 200 to 500 m/min. 
     
     
         17 . The method according to  claim 1 , which further comprises setting a viscosity of the spin dope in a range of 0.5 to 4 Pas. 
     
     
         18 . The method according to  claim 1 , which further comprises carrying out the dry spinning process with 100 to 30,000 spin nozzles. 
     
     
         19 . The method according to  claim 1 , which further comprises carrying out the dry spinning process with 200 to 2,000 spin nozzles. 
     
     
         20 . The method according to  claim 1 , which further comprises carrying out the dry spinning process at shear rates in a range of 20,000 to 40,000 s −1 . 
     
     
         21 . The method according to  claim 6 , further comprising supplying a spinning aid fraction having a 1% to 5% by weight. 
     
     
         22 . The method according to  claim 6 , further comprising supplying a spinning aid fraction having a 2.5% to 4% by weight. 
     
     
         23 . The method according to  claim 1 , which further comprises setting a spinning duct temperature to be in a range of 50° C. to 100° C. 
     
     
         24 . The method according to  claim 12 , which further comprises:
 selecting the inert atmosphere from the group consisting of nitrogen and argon;   selecting the reducing atmosphere from the group consisting of a gas mixture consisting of argon, hydrogen, nitrogen, carbon monoxide, at least one carrier gas and at least one reducing gas; and   setting the temperatures in the range of 900° C. to 1,300° C.   
     
     
         25 . SiC fibers produced according to the method of  claim 1 , wherein the SiC fibers have a Y modulus being more than 130 GPa, a tensile strength being more than 1.5 GPa, and a diameter in a range of 5 to 50 μm. 
     
     
         26 . The SiC fibers according to  claim 25 , wherein the SiC fibers have an oxygen content of less than 1% by weight. 
     
     
         27 . The SiC fibers according to  claim 25 , wherein the Y modulus is more than 150 GPa and the tensile strength is more than 2 GPa. 
     
     
         28 . The SiC fibers according to  claim 25 , wherein the Y modulus is more than 200 GPa and the tensile strength is more than 3.1 GPa. 
     
     
         29 . The SiC fibers according to  claim 14 , wherein the SiC fibers have an oxygen content in a range 0.2% to 0.8% by weight. 
     
     
         30 . A fiber bundle, comprising:
 SiC fibers produced according to the method of  claim 1  and having a Y modulus being more than 130 GPa, a tensile strength being more than 1.5 GPa, and a diameter in a range of 5 to 50 μm, the fiber bundle containing 10 to 50,000 of the SiC fibers.   
     
     
         31 . The fiber bundle according to  claim 30 , wherein the fiber bundle contains 100 to 30,000 of the SiC fibers having a high regularity. 
     
     
         32 . The fiber bundle according to  claim 30 , wherein the fiber bundle contains 200 to 2,000 of the SiC fibers.