Ceramic materials for friction linings

Abstract

Ceramic friction linings comprising a material consisting essentially of metal oxides which are present in the form of a sintered ceramic or in the form of ceramic particles bound by carbon and/or carbides, processes for producing them and their use in combination with ceramic friction bodies, in particular for high-performance brakes

1 . A ceramic friction lining comprising a material consisting essentially of metal oxides which are present in the form of a sintered ceramic or in the form of ceramic particles bound by carbon and/or carbides, wherein the material has a mass fraction of at least 50% of metal oxides.  
     
     
         2 . A ceramic friction lining as claimed in  claim 1 , wherein the metal oxides are selected from among oxides of at least one of the metals of the group consisting of Ti, Zr, Al, B, Si, Ca and Mg.  
     
     
         3 . A ceramic friction lining as claimed in  claim 1 , wherein the crystal structure of the metal oxides is a layer lattice.  
     
     
         4 . A ceramic friction lining as claimed in  claim 1 , wherein the metal oxides are selected from among magnesium aluminosilicates, talc and magnesium oxide.  
     
     
         5 . A ceramic friction lining as claimed in  claim 1  which has a mass fraction of at least 50% of magnesium oxide.  
     
     
         6 . A ceramic friction lining as claimed in  claim 5 , wherein the magnesium oxide is bound by carbon or carbides.  
     
     
         7 . A ceramic friction lining as claimed in  claim 1  which comprises carbides of metals of the group consisting of Si, Ti, Fe, Ni and Cr either individually or in admixture with one another.  
     
     
         8 . A ceramic friction lining as claimed in  claim 7  in which silicon carbide is present.  
     
     
         9 . A ceramic friction lining as claimed in  claim 1  in which further additives selected from among inorganic binders, substances which modify the coefficient of friction, friction promoters and lubricants are present, with the sum of the mass fractions of the additives in the materials being below 50%.  
     
     
         10 . A ceramic friction lining as claimed in  claim 1 , wherein the materials comprise heat-resistant fibers or whiskers in a volume fraction of up to 35%.  
     
     
         11 . A ceramic friction lining as claimed in  claim 10 , wherein the fibers are selected from among aramid fibers, acrylic fibers, cellulose fibers, carbon fibers and metal fibers or steel, copper or its alloys.  
     
     
         12 . A ceramic friction lining as claimed in  claim 1 , wherein the materials have a mass fraction of from 10 to 30% of carbon fibers.  
     
     
         13 . A ceramic friction lining as claimed in  claim 9 , wherein the substances which modify the coefficient of friction are selected from among copper, tin, antimony, manganese(II) sulfide, antimony trioxide and tin(II) oxide.  
     
     
         14 . A ceramic friction lining as claimed in  claim 9 , wherein the friction promoters are selected from among aluminum oxide, zirconium dioxide, zircon (ZrSiO 4 ), silicon carbide and silicon dioxide.  
     
     
         15 . A ceramic friction lining as claimed in  claim 9 , wherein the lubricants are selected from among molybdenum disulfide, graphite and boron nitride.  
     
     
         16 . A ceramic friction lining as claimed in  claim 1  which contains additions of carbon, copper or tin.  
     
     
         17 . A friction system capable of withstanding high temperatures comprising friction linings as claimed in  claim 1  and friction bodies made of ceramic materials.  
     
     
         18 . A friction system as claimed in  claim 17 , wherein the friction bodies comprise C/SiC or C/C—SiC materials.  
     
     
         19 . A method of use of a friction system as claimed in  claim 17  as a brake system, comprising combining disks with a friction lining of  claim 1  with friction bodies made of ceramic materials.  
     
     
         20 . The method of use of  claim 19 , wherein the friction bodies comprise C/SiC or C/C—SiC materials.  
     
     
         21 . A method of use of a friction system as claimed in  claim 17  as a clutch system, comprising combining disks with a friction lining of  claim 1  with friction bodies made of ceramic materials.  
     
     
         22 . The method of use of  claim 21 , wherein the friction bodies comprise C/SiC or C/C—SiC materials.  
     
     
         23 . The method of use as claimed in  claim 19  in rail vehicles, aircraft or motor vehicles.  
     
     
         24 . The method of use as claimed in  claim 21  in motor vehicles.  
     
     
         25 . A process for producing a friction lining as claimed in  claim 1 , wherein 
 a shapable mixture of pulverulent metal oxides, additives and thermally curing organic binders is produced in a first step,    the mixture is brought into the desired shape by pressing in a second step and    the shaped mixture is cured with the aid of the thermally curing organic binders in a third step, and    the green body produced in this way is carbonized in a fourth step at temperatures above 650° C. and in the absence of atmospheric oxygen.    
     
     
         26 . The process as claimed in  claim 25 , wherein metals selected from the group consisting of Si, Ti, Fe, Ni and Cr are added to the shapable mixture and form carbides in the fourth step with the carbon produced in the carbonization.  
     
     
         27 . The process as claimed in  claim 25 , wherein the metals are used in such an amount that the sum of the mass fractions of carbon and carbides in the material forming the friction lining is in the range from 5 to 50%.  
     
     
         28 . A process for producing a friction lining as claimed in  claim 1 , wherein 
 a shapable mixture of pulverulent metal oxides, additives and, if desired, organic plasticizers is produced in a first step,    the mixture is brought into the desired shape by pressing in a second step and    the shaped mixture is sintered in a third step at temperatures of from about 1000° C. to about 1500° C.