Methods and apparatus for forming a composite protection layer

Abstract

A method for reducing oxidation in ceramic composites is provided. The method includes depositing a first portion of a silicon carbide (SiC) matrix over at least a portion of an article using a first chemical vapor infiltration (CVI) process, depositing a silicon (Si)-doped boron nitride (BN) layer within at least a portion of the SiC matrix using a second CVI process, and depositing a second portion of the SiC matrix within at least a portion or continuation of the first portion of the SiC matrix using a third CVI process.

1 . A method to reduce oxidation in ceramic composites, said method comprising: 
 depositing a first portion of a silicon carbide (SiC) matrix over at least a portion of an article using a first chemical vapor infiltration (CVI) process;    depositing a silicon (Si)-doped boron nitride (BN) layer within at least a portion of the SiC matrix using a second CVI process; and    depositing a second portion of the SiC matrix within at least a portion or in continuation of the first portion of the SiC matrix using a third CVI process.    
   
   
       2 . A method to reduce oxidation in ceramic composites in accordance with  claim 1  wherein said depositing a first portion of a SiC matrix over at least a portion of an article using a first CVI process comprises: 
 depositing the SiC matrix at pre-determined carbon (C)-to-silicon (Si) ratios that may be homogeneous about the surface of the article or varied circumferentially and/or as a function of the contours of the article;    depositing the SiC matrix while maintaining isothermal conditions, or varying the temperature of the article wherein a pre-determined temperature gradient in the article is maintained; and    depositing the SiC matrix while the article is stationary or while the article is rotating about a pre-determined axis and at a pre-determined rate.    
   
   
       3 . A method to reduce oxidation in ceramic composites in accordance with  claim 2  wherein said depositing the SiC matrix at pre-determined C-to-Si ratios comprises controlling a plurality of first CVI process conditions which further comprises controlling a temperature of a plurality of gaseous reactants, a pressure, a rate of flow of the plurality of reactants, a plurality of concentrations of the plurality of reactants, and a rate of removal of a plurality of concentrations of a plurality of byproduct gases released by a plurality of reactions.  
   
   
       4 . A method to reduce oxidation in ceramic composites in accordance with  claim 1 , wherein said depositing a Si-doped BN layer within at least a portion of the SiC matrix using a second CVI process comprises: 
 interrupting said depositing a first portion of the SiC matrix;    depositing the Si-doped BN layer wherein substantially all of the carbon fiber bundles have a substantially uniform Si-doped BN layer coating;    controlling a plurality of second CVI process conditions which further comprises controlling a temperature of the preform, a temperature of a plurality of gaseous reactants, a pressure, a rate of flow of the plurality of reactants, a plurality of concentrations of the plurality of reactants, and a rate of removal of a plurality of concentrations of a plurality of byproduct gases released by a plurality of reactions wherein the second CVI process conditions may vary from the first CVI process conditions; and    depositing the Si-doped BN layer while the article is stationary or while the article is rotating about a pre-determined axis and at a pre-determined rate.    
   
   
       5 . A method to reduce oxidation in ceramic composites in accordance with  claim 1 , wherein said depositing a second portion of the SiC matrix within at least a portion or in continuation of the first portion of the SiC matrix using a third CVI process comprises: 
 depositing the SiC matrix at pre-determined C-to-Si ratios that may be homogeneous about the surface of the article or varied circumferentially and/or as a function of the contours of the article;    depositing the SiC matrix while maintaining isothermal conditions, or varying the temperature of the article wherein a pre-determined temperature gradient in the article is maintained; and    depositing the SiC matrix while the article is stationary or while the article is rotating about a pre-determined axis and at a pre-determined rate.    
   
   
       6 . A method to reduce oxidation in ceramic composites in accordance with  claim 5  wherein said depositing the SiC matrix at pre-determined C-to-Si ratios comprises controlling a plurality of third CVI process conditions which further comprises controlling a temperature of a plurality of gaseous reactants, a pressure, a rate of flow of the plurality of reactants, a plurality of concentrations of the plurality of reactants, and a rate of removal of a plurality of concentrations of a plurality of byproduct gases released by a plurality of reactions, wherein the third CVI process conditions may vary from the first and second CVI process conditions.  
   
   
       7 . A method for fabricating a ceramic composite article, said method comprising: 
 fabricating a carbon fiber preform article with a plurality of pre-determined dimensions;    depositing a layer of pyrolytic carbon over at least a portion of the carbon fiber preform article;    depositing a first portion of a silicon carbide (SiC) matrix on at least a portion of the reinforcing layer using a first chemical vapor infiltration (CVI) process;    depositing a silicon (Si)-doped boron nitride (BN) layer within at least a portion of the SiC matrix using a second CVI process; and    depositing a second portion of the SiC matrix within at least a portion or in continuation of the first portion of the SiC matrix using a third CVI process.    
   
   
       8 . A method for fabricating a ceramic composite article in accordance with  claim 7 , wherein said fabricating a carbon fiber preform article with a plurality of pre-determined dimensions comprises: 
 pre-shaping the article to a set of pre-determined contours and thicknesses substantially similar to the dimensions of a finished article; and    forming the article with a plurality of layers wherein the layers may have a plurality of pre-determined material densities that may be substantially homogeneous, or varied circumferentially and/or as a function of the contours of the article.    
   
   
       9 . A method for fabricating a ceramic composite article in accordance with  claim 7 , wherein said forming a reinforcing layer of carbon fiber bundles over at least a portion of the carbon fiber preform article comprises: 
 modifying at least a portion of one surface of the article thereby developing a more porous, fibrous, and permeable substrate;    forming the layer of carbon fibers with a density and thickness that may be uniform and homogenous, or a plurality of densities and thicknesses that may be varied circumferentially and/or as a function of the contours of the article;    forming the layer of carbon fibers with a plurality of substantially uniform dimensions, or with a plurality of varied dimensions; and    forming the layer of carbon fibers with an orientation that may be uniform and homogenous, or a plurality of orientations that may be varied circumferentially and/or as a function of the contours of the article.    
   
   
       10 . A method for fabricating a ceramic composite article in accordance with  claim 7 , wherein said depositing a first portion of a silicon carbide (SiC) matrix on at least a portion of the reinforcing layer using a first chemical vapor infiltration (CVI) process comprises: 
 depositing the SiC matrix at pre-determined carbon (C)-to-Si ratios that may be homogeneous about the surface of the article or varied circumferentially and/or as a function of the contours of the article;    depositing the SiC matrix while maintaining isothermal conditions, or varying the temperature of the preform wherein a pre-determined temperature gradient in the preform is maintained; and    depositing the SiC matrix while the article is stationary or while the article is rotating about a pre-determined axis and at a pre-determined rate.    
   
   
       11 . A method for fabricating a ceramic composite article in accordance with  claim 10  wherein said depositing the SiC matrix at pre-determined C-to-Si ratios comprises controlling a plurality of first CVI process conditions which further comprises controlling a temperature of a plurality of gaseous reactants, a pressure, a rate of flow of the plurality of reactants, a plurality of concentrations of the plurality of reactants, and a rate of removal of a plurality of concentrations of a plurality of byproduct gases released by a plurality of reactions.  
   
   
       12 . A method for fabricating a ceramic composite article in accordance with  claim 7 , wherein said depositing a Si-doped BN layer within at least a portion of the SiC matrix using a second CVI process comprises: 
 interrupting said depositing a first portion of the SiC matrix;    depositing the Si-doped BN layer wherein substantially all of the carbon fiber bundles have a substantially uniform Si-doped BN layer coating; and    controlling a plurality of second CVI process conditions which further comprises controlling a temperature of the preform, a temperature of a plurality of gaseous reactants, a pressure, a rate of flow of the plurality of reactants, a plurality of concentrations of the plurality of reactants, and a plurality of concentrations of a rate of removal of a plurality of byproduct gases released by a plurality of reactions wherein the second CVI process conditions may vary from the first CVI process conditions; and    depositing the Si-doped BN layer matrix while the article is stationary or while the article is rotating about a pre-determined axis and at a pre-determined rate.    
   
   
       13 . A method for fabricating a ceramic composite article in accordance with  claim 7 , wherein said depositing a second portion of the SiC matrix within at least a portion of the first portion or in continuation of the SiC matrix using a third CVI process comprises: 
 depositing the SiC matrix at pre-determined C-to-Si ratios that may be homogeneous about the surface of the article or varied circumferentially and/or as a function of the contours of the article;    depositing the SiC matrix while maintaining isothermal conditions, or varying the temperature of the preform wherein a pre-determined temperature gradient in the preform is maintained; and    depositing the SiC matrix while the article is stationary or while the article is rotating about a pre-determined axis and at a pre-determined rate.    
   
   
       14 . A method for fabricating a ceramic composite article in accordance with  claim 13  wherein said depositing the SiC matrix at pre-determined C-to-Si ratios comprises controlling a plurality of third CVI process conditions which further comprises controlling a temperature of a plurality of gaseous reactants, a pressure, a rate of flow of the plurality of reactants, a plurality of concentrations of the plurality of reactants, and a rate of removal of a plurality of concentrations of a plurality of byproduct gases released by a plurality of reactions, wherein the third CVI process conditions may vary from the first and second CVI process conditions.  
   
   
       15 . An article comprising a ceramic composite protective layer, said layer comprising: 
 a substrate comprised of a surface region; and    a region of fiber bundles extending over at least a portion of said substrate infiltrated with a matrix material impregnated with an oxidizing agent.    
   
   
       16 . An article comprising a ceramic composite protective layer in accordance with  claim 15  wherein said substrate further comprises a carbon fiber preform with pre-determined dimensions.  
   
   
       17 . An article comprising a ceramic composite protective layer in accordance with  claim 16  wherein said carbon fiber preform with pre-determined dimensions comprises: 
 an article pre-shaped to a set of pre-determined contours and thicknesses substantially similar to the dimensions of a finished article; and    a plurality of layers wherein said layers may have a plurality of pre-determined material densities that may be substantially homogeneous, or varied circumferentially and/or as a function of said contours of said article.    
   
   
       18 . An article comprising a ceramic composite protective layer in accordance with  claim 15  wherein said region of fiber bundles extending over at least a portion of said substrate infiltrated with a matrix material impregnated with an oxidizing agent comprises a layer of reinforcing carbon fiber bundles deposited over at least a portion of said preform.  
   
   
       19 . An article comprising a ceramic composite protective layer in accordance with  claim 15  wherein said region of fiber bundles extending over at least a portion of said substrate infiltrated with a matrix material impregnated with an oxidizing agent comprises a silicon carbide (SiC) matrix impregnated with a boron nitride (BN) oxidizing agent.  
   
   
       20 . An article comprising a ceramic composite protective layer in accordance with  claim 19  wherein said SiC matrix impregnated with a BN oxidizing agent may be deposited at pre-determined carbon (C)-to-silicon (Si) ratios that may be homogeneous about said surface region of the article or varied circumferentially and/or as a function of the contours of the article.