Abstract:
A method of coating a fiber for forming a ceramic matrix composite material comprises the steps of moving a fiber through an energy application station, and applying energy to the fiber, and providing an outer coating on the fiber.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 61/977,160, filed Apr. 9, 2014. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This application relates to a method of preparing a ceramic fiber for a subsequent coating, wherein the fiber is treated from an energy source. 
         [0003]    Ceramic, carbon and glass fibers are utilized in the formation of ceramic matrix composites (“CMC”) materials. CMC materials are finding applications in any number of high temperature uses. As an example, gas turbine engines may incorporate a number of components formed of CMC materials. 
         [0004]    The CMC materials are formed from ceramic, carbon or glass fibers, such as silicon carbide (“SiC”) fibers. In the formation of CMC materials, the diameter of the fibers may be between 5 and 150 microns. In the process of making the CMC materials, it is often desirable to coat the SiC fibers with one or more coatings. These coatings could include boron nitride or other coatings, such as silicon nitride, silicon carbide, boron carbide, carbon, oxides or combinations thereof to improve the environmental durability of the underlying materials. 
         [0005]    It is known that application of a plasma treatment to ceramic fibers can increase their strength and some other properties. However, such a pretreatment has not been proposed to better improve the coatability of the fibers. 
       SUMMARY OF THE INVENTION 
       [0006]    In a featured embodiment, a method of coating a fiber for forming a ceramic matrix composite material comprises the steps of moving a fiber through an energy application station, and applying energy to the fiber, and providing an outer coating on the fiber. 
         [0007]    In another embodiment according to the previous embodiment, the energy application station includes a plasma treatment. 
         [0008]    In another embodiment according to any of the previous embodiments, the energy application station also includes a microwave application. 
         [0009]    In another embodiment according to any of the previous embodiments, the energy application station includes a microwave application. 
         [0010]    In another embodiment according to any of the previous embodiments, the fiber is a silicon-containing fiber. 
         [0011]    In another embodiment according to any of the previous embodiments, the fiber has a diameter greater than or equal to 5 micron and less than or equal to 150 micron. 
         [0012]    In another embodiment according to any of the previous embodiments, an outer coating on the fiber is provided after a fiber moves through an energy application station. 
         [0013]    In another embodiment according to any of the previous embodiments, an outer coating on the fiber is provided while a fiber moves through an energy application station. 
         [0014]    In another embodiment according to any of the previous embodiments, an outer coating on the fiber is provided before a fiber moves through an energy application station. 
         [0015]    In another embodiment according to any of the previous embodiments, the fiber having a diameter greater than or equal to 5 micron and less than or equal to 150 micron. 
         [0016]    In another embodiment according to any of the previous embodiments, an outer coating on the fiber is provided after a fiber moves through an energy application station. 
         [0017]    In another embodiment according to any of the previous embodiments, an outer coating on the fiber is provided while a fiber moves through an energy application station. 
         [0018]    In another embodiment according to any of the previous embodiments, an outer coating on the fiber is provided before a fiber moves through an energy application station. 
         [0019]    In another embodiment according to any of the previous embodiments, the coating includes at least one of boron nitride, silicon nitride, silicon carbide, boron carbide, carbon, Si 3 N 4 , SiC, AlN, oxide coatings or combinations thereof. 
         [0020]    In another embodiment according to any of the previous embodiments, an outer coating on the fiber is provided after a fiber moves through an energy application station. 
         [0021]    In another embodiment according to any of the previous embodiments, an outer coating on the fiber is provided while a fiber moves through an energy application station. 
         [0022]    In another embodiment according to any of the previous embodiments, an outer coating on the fiber is provided before a fiber moves through an energy application station. 
         [0023]    In another embodiment according to any of the previous embodiments, the fiber is made into an intermediate product, and then into a final CMC component. 
         [0024]    In another embodiment according to any of the previous embodiments, the final CMC component is for use in a gas turbine engine. 
         [0025]    In another embodiment according to any of the previous embodiments, the coating includes at least one of boron nitride, silicon nitride, silicon carbide, boron carbide, carbon, Si 3 N 4 , SiC, AlN, oxide coatings or combinations thereof. 
         [0026]    These and other features may be best understood from the following drawings and specification, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]      FIG. 1A  schematically shows one method of a treatment of a ceramic fiber. 
           [0028]      FIG. 1B  shows another embodiment. 
           [0029]      FIG. 2  shows an intermediate product. 
           [0030]      FIG. 3  schematically shows a final product. 
           [0031]      FIG. 4A  shows another method embodiment. 
           [0032]      FIG. 4B  shows yet another method embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    As shown in  FIG. 1A , a spool  80  may include a fiber  82 . The fiber may be a ceramic containing silicon, such as SiC, SiCO, SiCNO, SiBCN, Si 3 N 4 . Also, the fiber can be a ceramic without silicon, a carbon fiber, or an oxide fiber. Examples include boron carbide, carbon, aluminum oxide, mullite, zirconia, alumina-silicate glass and combinations thereof. The phase(s) of the fibers may be stoichiometric or non-stoichiometric. In addition, the fibers may be fully crystalline, fully amorphous or partially crystalline and partially amorphous. 
         [0034]    Examples of such SiC fibers are available under the trade names Hi-Nicalon™ and Hi-Nicalon type S™. Such fibers may be available from Nippon Carbon Co, Ltd. (“NCK”) of Japan. Examples of ceramic oxide fibers are available under the trade name Nextel™ and may be procured from 3M™. The fiber  82  may be utilized to form CMC materials, and the fibers may be greater than or equal to 5 and less than or equal to 150 microns in diameter. Multiple fibers and fibers having a distribution of fiber diameters between 5 and 150 microns are also contemplated to benefit from this disclosure. 
         [0035]    An energy application station or treatment  84  is shown applying energy to a pulled or drawn fiber. The fiber is then provided with a coating treatment  86 , such that a downstream fiber portion  88  is coated. The application of the energy treatment increases the coatability of the fiber. 
         [0036]    The coating treatment  86  is shown schematically as is the energy application station  84 . The coating may be provided by a deposition process, or other appropriate coating processes including, but not limited to chemical vapor deposition, physical vapor deposition, dip coating, atomic layer deposition methods, spray coating, vacuum deposition or combinations thereof. Exemplary, but non limiting coatings may include boron nitride, silicon nitride, silicon carbide, boron carbide, carbon, Si 3 N 4 , SiC, AlN, oxide coatings or combinations thereof. The coatings themselves are known, however, the application of the energy treatment  84  increases the adherence and coatability to the fiber  82 . 
         [0037]    As shown in  FIG. 1B , a fiber  90  is pulled through an energy application station  92  that includes two stations  94  and  96 . 
         [0038]    In various applications, the energy applied at station  84  (or stations  94  and  96 ) may include a plasma treatment or electromagnetic radiation, such as, but not limited to microwave, terahertz, radio, laser, ultraviolet, infrared or combinations thereof. The energy application will clean, functionalize, and create one or more reactive sites, such as unsaturated bonding, on the fiber surface that enhances the subsequent deposition of the coatings at station  86 . 
         [0039]    In various applications, the energy application will selectively and beneficially interact with the coating material prior to deposition, resulting in a more desirable coating phase or structure. In one non-limiting example, the coating material can be a precursor compound such as a volatile organometallic compound. When in the vapor state, an exemplary electromagnetic radiation source such as microwave energy can selectively interact with bonds in the organometallic compound, causing them to decompose, change or convert to another bond type. This resulting modified organometallic compound may be more desirable in producing the preferred coating composition or structure. In one example, the organometallic compound contains Si bonded to one or more non-metals (O, C, H, N, etc). After interaction with the microwave energy, the bond(s) can break, leaving behind a reactive silicon atom with incomplete bond saturation, which would selectively interact with the fiber surface. 
         [0040]    While it has been proposed to utilize plasma treatment on ceramic fibers, this has not been to prepare the fibers for coating. 
         [0041]    The  FIG. 1B  embodiment may be utilized with one of the stations  94  being microwave application and the other station  96  being plasma application. 
         [0042]    The plasma treatment itself may be as known. The same is true of the microwave or other energy applications. The parameters for each of the treatments may be determined experimentally once a particular application has been identified. 
         [0043]      FIG. 2  shows an intermediate product  100  which may be made from a fiber such as fiber  88 . The intermediate product  100  may be a one, two or three dimensional product such as a fiber tow, pre-preg tape, woven cloths, knitted or braided or otherwise constructed volumes, such that a subsequent and final CMC product  130  (see  FIG. 3 ) is formed. The intermediate product  100  may be subsequently utilized in a polymer infiltration and pyrolysis, a chemical vapor infiltration process and/or slurry cast melt information process to form the final CMC component  130 . The component  130  formed in this way may be for use in a gas turbine engine, in one example, and could be a turbine blade, vane, blade outer air seal, combustion liner, etc. 
         [0044]    The FIG.  1 A/ 1 B embodiment is not the only order of application of coating and energy within the scope of application. 
         [0045]    As shown in  FIG. 4A , in an embodiment  200 , the coating treatment  204  is embedded into the energy treatment application  206 . In this manner, the deposited coating on the fiber  202  can interact with the energy source to provide a set of benefits to the coating and the adhesion of the fiber. 
         [0046]      FIG. 4B  shows an embodiment  210  wherein the coating treatment  204  is applied to the fiber  212  before it enters the energy treatment station  216 . In both the  FIG. 4A and 4B  embodiments, the coating material can be a precursor that can be converted to a more desirable phase in the final coating by the application of the energy. 
         [0047]    Thus, if the energy application is considered a step (a) and the coating treatment considered a step (b), then the step (b) can occur after step (a), or the step (b) can occur during step (a), or the step (b) can occur before the step (a). 
         [0048]    It should also be understood that while a single application of energy and coating is disclosed in this application, the coating and energy could be provided in an iterative manner. That is, there could be several coating and/or energy treatment stations. 
         [0049]    Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.