Uniformly coating porous composite materials

Abstract

A method for fabricating a composite material using chemical vapor infiltration, comprising: providing one or more fibrous preforms and a porous dummy preform; positioning the fibrous preforms proximate to the porous dummy preform and an area where a poisoning molecule is generated within a reaction chamber of a chemical vapor infiltration assembly; heating the reaction chamber to a chemical vapor infiltration temperature for matrix densification; introducing into the reaction chamber a matrix precursor gas; reacting the matrix precursor gas with the porous dummy preform to deposit a matrix material and generate a poisoning molecule; depositing uniformly one or more coating layers of the matrix material on and within the fibrous preforms; and fabricating one or more composite materials.

Description

RTX Ref. No. 180038US01MWZB Ref. No. RTXPW-0053-V01UNIFORMLY COATING POROUS COMPOSITE MATERIALSFIELD OF THE INVENTION

[0001] The subject matter disclosed herein relates to composite materials and, in particular, to methods for uniformly coating porous composite materials.BACKGROUND OF THE INVENTION

[0002] In the chemical vapor infiltration (CVI) of porous fibrous preforms, depositing a uniform coating within the interior of the preform proves difficult due to the kinetic-to-diffusion ratio of the reaction being too large, especially as the CVI temperature increases. A large kinetic-to- diffusion ratio leads to over depositing the reaction product onto the external surface of the preform with the potential rapid closure of the exposed pores whose internal paths lead to the interior. This result is also known as 'canning' the preform. In some CVI chemistries, a reaction product of the decomposition of the matrix precursor gas becomes adsorbed on the external surface(s) of the preform(s) and poisons the external surface thereby greatly reducing the kinetics. Concomitantly, the kinetic-to-diffusion ratio then is reduced and becomes more favorable to achieving a uniform deposition.

[0003] There exists a need to control the kinetics to diffusion ratio and ensure a uniform deposition of matrix material takes place.SUMMARY OF THE INVENTION

[0004] The present disclosure is directed, in a first aspect, to a method for fabricating a composite material using chemical vapor infiltration, comprising: providing one or more fibrous preforms and a porous dummy preform; positioning the fibrous preforms proximate to the porous dummy preform and an area where a poisoning molecule is generated within a reaction chamber of a chemical vapor infiltration assembly; heating the reaction chamber to a chemical vapor infiltration temperature for matrix densification; introducing into the reaction chamber aRTX Ref. No. 180038US01MWZB Ref. No. RTXPW-0053-V01 matrix precursor gas; reacting the matrix precursor gas with the porous dummy preform to deposit a matrix material and generate a poisoning molecule; depositing uniformly one or more coating layers of the matrix material on and within the fibrous preforms; and fabricating one or more composite materials.

[0005] In another embodiment, the present disclosure is directed to a method for fabricating a ceramic matrix composite using chemical vapor infiltration, comprising: providing one or more fibrous preforms and a porous dummy preform; positioning the fibrous preforms proximate to the porous dummy preform and an area where a poisoning molecule is generated within a reaction chamber of a chemical vapor infiltration assembly; heating the reaction chamber to a chemical vapor infiltration temperature for matrix densification; introducing into the reaction chamber a matrix precursor gas; reacting the matrix precursor gas with the porous dummy preform to deposit silicon carbide and generate a hydrochloric acid as a poisoning molecule; increasing a concentration of the hydrochloric acid within the reaction chamber; diffusing the hydrochloric acid throughout the fibrous preforms; depositing the matrix precursor gas throughout the fibrous preforms; depositing uniformly one or more coating layers of the silicon carbide on and within the fibrous preforms; and fabricating one or more silicon carbide ceramic matrix composites.

[0006] In yet another embodiment, the present disclosure is directed to chemical vapor infiltration assembly, comprising: a reactor comprising one or more gas inlets, gas outlets, and reaction chambers; one or more reactant gas sources fluidly connected to the gas inlet; a purge gas source fluidly connected to the gas inlet; one or more vacuum pumps fluidly connected to the gas outlet; the reaction chamber comprises: a mixing chamber; one or more levels defined by one or more gas distributor plates; one or more preheaters disposed proximate the gas distributor plate; one or more porous dummy preforms disposed proximate to and between the preheater and the gas distributor plate.RTX Ref. No. 180038US01MWZB Ref. No. RTXPW-0053-V01

[0007] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the method further comprises controlling a kinetic-to-diffusion ratio of the deposition rate of the matrix material.

[0008] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the method further comprises inhibiting the deposition of the matrix material throughout the fibrous preforms by the poisoning molecule.

[0009] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the matrix precursor gas comprises one or more of: methyltrichlorosilane, dimethylchlorosilane, or silicon tetrachloride and methane; the matrix material comprises silicon carbide; and, the poisoning molecule comprises a hydrochloric acid.

[0010] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the method further comprises reacting the matrix precursor gas with the porous dummy preform, increasing a concentration of the poisoning molecule within the reaction chamber, and diffusing the matrix material throughout the fibrous preforms.

[0011] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the deposition of silicon carbide in the fibrous preform is uniform throughout a thickness of the fibrous preform.

[0012] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the porous dummy preform comprises one or more of a reticulated vitreous carbon foam, a carbon preform, a carbon felt, a sacrificial fibrous preform, and combinations thereof.

[0013] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the sacrificial fibrous preform comprises any one or more of silicon carbide, carbon, silicon oxycarbide, silicon nitride, silicon carbonitride, hafnium carbide,RTX Ref. No. 180038US01MWZB Ref. No. RTXPW-0053-V01 tantalum carbide, silicon borocarbonitride, silicon aluminum carbon nitride, and combinations thereof.

[0014] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the fibrous preform comprises any one or more of silicon carbide, carbon, silicon oxycarbide, silicon nitride, silicon carbonitride, hafnium carbide, tantalum carbide, silicon borocarbonitride, silicon aluminum carbon nitride, and combinations thereof.

[0015] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the method further comprises replacing the porous dummy preform with a subsequent porous dummy preform.

[0016] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the method further comprises controlling a kinetic-to-diffusion ratio of the deposition rate of the silicon carbide.

[0017] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the method further comprises inhibiting the deposition of the silicon carbide throughout the fibrous preforms by the hydrochloric acid.

[0018] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the matrix precursor gas comprises one or more of: methyltrichlorosilane, dimethylchlorosilane, or silicon tetrachloride and methane.

[0019] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the deposition of silicon carbide in the fibrous preform is uniform throughout a thickness of the fibrous preform.

[0020] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the porous dummy preform comprises one or more of a carbon foam, a carbon preform, a carbon felt, a sacrificial fibrous preform, and combinations thereof.RTX Ref. No. 180038US01MWZB Ref. No. RTXPW-0053-V01

[0021] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the sacrificial fibrous preform comprises any one or more of silicon carbide, carbon, silicon oxycarbide, silicon nitride, silicon carbonitride, hafnium carbide, tantalum carbide, silicon borocarbonitride, silicon aluminum carbon nitride, and combinations thereof.

[0022] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the fibrous preform comprises any one or more of silicon carbide, carbon, silicon oxycarbide, silicon nitride, silicon carbonitride, hafnium carbide, tantalum carbide, silicon borocarbonitride, silicon aluminum carbon nitride, and combinations thereof.

[0023] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the method further comprises replacing the porous dummy preform with a subsequent porous dummy preform.

[0024] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the reactant gas sources comprise a matrix precursor gas source.

[0025] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the porous dummy preform comprises a carbon foam, a carbon preform, a carbon felt, a sacrificial fibrous preform, and combinations thereof.

[0026] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the fluid connection between the one or more reactant gas sources and the gas inlet further comprises one or more valves and one or more mass flow controllers.RTX Ref. No. 180038US01MWZB Ref. No. RTXPW-0053-V01

[0027] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the fluid connection between the purge gas source and the gas inlet further comprises one or more valves and one or more mass flow controllers.

[0028] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the fluid connection between the one or more vacuum pumps and the gas outlet further comprises one or more valves and a pressure monitor.

[0029] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the reactant gas sources further comprise an interface precursor gas.BRIEF DESCRIPTION OF FIGURES

[0030] The features of the disclosure believed to be novel and the elements characteristic of the invention are set forth with particularity in the appended claims. The figures are for illustration purposes only and are not drawn to scale. The disclosure itself, however, both as to organization and method of operation, can best be understood by reference to the description of the preferred embodiment(s) which follows, taken in conjunction with the accompanying drawings in which:

[0031] FIG. 1 is an illustration of an exemplary CVI assembly for use in performing an exemplary CVI method.

[0032] FIG. 2 is a flowchart illustrating the exemplary CVI method.

[0033] FIG. 3 is a continuation of the flowchart of FIG. 2.

[0034] FIG. 4 is a continuation of the flowchart of FIGS. 2 and 3.RTX Ref. No. 180038US01MWZB Ref. No. RTXPW-0053-V01DETAILED DESCRIPTION OF THE INVENTION

[0035] The embodiments of the present disclosure can comprise, consist of, and consist essentially of the features and / or steps described herein, as well as any of the additional or optional ingredients, components, steps, or limitations described herein or would otherwise be appreciated by one of skill in the art. It is to be understood that all concentrations disclosed herein are by weight percent (wt. %.) based on a total weight of the composition unless otherwise indicated.

[0036] The present disclosure is directed to an exemplary apparatus and related exemplary method for fabricating a composite material using chemical vapor infiltration. The exemplary apparatus incorporates a porous dummy preform whose presence, when carrying out the exemplary method, facilitates forming hydrochloric acid, thus increasing the concentration of hydrochloric acid within the reactor chamber and, in turn, controlling the kinetic-to-diffusion ratio. The kinetic-to-diffusion ratio may be expressed as the following equation: k / D as measured in m1, where k = deposition rate of a matrix material, e.g., silicon carbide (SiC), on a fiber surface as measured in m / s; and D = the diffusivity of a matrix precursor gas, e.g., methyltrichlorosilane, into the fibrous preform as measured in m2 / s. Hydrochloric acid, a by-product of the reaction of methyltrichlorosilane to form SiC, may act as a poisoning agent, inhibit the deposition of SiC throughout the fibrous preforms, and slow down "k", that is, the deposition rate of SiC. As a result, the k / D value is lowered and the deposition of SiC is more uniform throughout the porous fibrous preforms. That is, the deposition of silicon carbide throughout the fibrous preforms is uniform throughout a thickness of the porous fibrous preforms.

[0037] Referring now to FIG. 1, a schematic view of a CVI assembly 10 for the manufacture of CMC components. The CVI assembly 10 may be designed to densify fibrous preforms with a matrix material SiC matrix. Suitable matrix materials may include, but are not limited to SiC, B4C, SiB4C, combinations thereof, and the like. The CVI assembly 10 may include a reactor 12, having a gas inlet 14, a gas outlet 16, and a reaction chamber 18. The reaction chamber 18 may beRTX Ref. No. 180038US01MWZB Ref. No. RTXPW-0053-V01 subdivided into a mixing chamber 20 and a plurality of levels or sub-chambers 22, 24, 26, defined between gas distributor plates 28, 30, 32. The mixing chamber 20 may include one or more preheaters 34 to heat the reactant gas entering the reactor 12. In at least one embodiment, one or more porous dummy preforms 42 may be disposed between the preheater 34 and gas distributor plate 28. In at least one embodiment, one or more porous dummy preforms 42 may be disposed proximate to the fibrous preforms 36 such that the poisoning gas may be generated locally near the fibrous preforms 36. The porous dummy preform 42 may be a foam-like material capable of permitting the reactant gas to coat the exterior surface as well as enter the pores and coat the interior surface. Suitable foam-like material may include, but is not limited, a carbon foam, e.g., a reticulated vitreous carbon foam, a carbon preform, a carbon felt, a sacrificial fibrous preform, combinations thereof, and the like. The sacrificial fibrous preform may comprise the same materials as the fibrous preforms. The foam-like material may have a surface area sufficient to generate an amount of poisoning molecule that is sufficient to poison the reaction on the fibrous preforms 36. The CVI assembly 10 may further include one or more reactant gas sources 38, 40 a purge gas source 44, a plurality of gas lines 46, 48, 50 fluidly connected to the reactor 12 and operable via valves V1-V3, a vacuum pump 56 fluidly connected to outlet 16 via valve V4, and a heat source (not shown). In at least one embodiment, the CVI assembly 10 may include a controller (not shown), which may be communicatively coupled to the heat source, valves V1-V4, the vacuum pump 56, and other components of the CVI assembly 10, including a pressure monitor P, to facilitate operation of the CVI assembly 10.

[0038] The reactor 12 may be, e.g., an isobaric reactor, configured to house one or more fibrous preforms 36 and to facilitate chemical vapor infiltration of a plurality of reactant gases into and within the fibrous preforms 36. A plurality of gas distributor plates 28, 30, 32 may be used to provide support, e.g., shelves, for multiple fibrous preforms 36 within the reaction chamber 18 and to facilitate reactant gas redistribution among levels 22, 24, 26. The gas distributor plates 28, 30, 32 may be perforated or otherwise porous members that allow for diffusion or flow of reactant gas between chambers 22, 24, 26. In at least one embodiment, the number of levels asRTX Ref. No. 180038US01MWZB Ref. No. RTXPW-0053-V01 well as the height of each level may be increased or decreased depending on the application, number, and size of the fibrous preforms 36. The disclosed exemplary CVI assembly 10 and associated method may be used to uniformly densify one or more fibrous preforms 36. In at least one embodiment, the reactor 12 may have alternative constructions and is not limited to the embodiment depicted in FIG. 1.

[0039] Reactant gas can enter reactor 12 through the gas inlet 14. As illustrated in FIG. 1, CVI assembly 10 may include one or more reactant gas sources 38, 40, fluidly connected to the reactor 12 via one or more gas conduits 46, 48. The reactant gas may be delivered to the reaction chamber 18 in separate conduits, which may be delivered to the inlet 14, as illustrated in FIG. 1. The valves VI, V2 and the MFCs 52 may be opened and closed to control the supply of reactant gases to the reactor 12. The reactant gas source 38 may provide one or more precursors for a fiber interface coating material, including but not limited to, boron nitride precursors capable of forming a boron nitride coating on fibers of the fibrous preform 36. The reactant gas source 40 may provide one or more precursors of a matrix material. Once the matrix precursor gas, e.g., methyltrichlorosilane, decomposes, a matrix material, e.g., silicon carbide, and a poisoning molecule, including but not limited to, a halogen-based acid, e.g., hydrochloric acid, may be produced.

[0040] One or more gases may enter the reaction chamber 18 in the mixing chamber 20. At least one porous dummy preform 36 may be located within the mixing chamber 20 and disposed between the preheater 34 and gas distributor plate 28. The reactant gas may flow from the gas inlet 14 toward the gas outlet 16. Prior to exiting the reactor 12, one or more gases may enter completion bed 36 where unreacted gas may react, producing an exhaust gas. The exhaust gas may then be pulled from the reaction chamber 18 through the outlet 16 via the vacuum pump 56. Radiative or thermal energy may be applied to the reactor 12 to induce a chemical reaction therein. In at least one embodiment, one or more reactant gases may be heated by a preheater 34 prior to entering the reactor 12.RTX Ref. No. 180038US01MWZB Ref. No. RTXPW-0053-V01

[0041] A purge gas may be delivered to the reactor 12 to remove ambient air and unreacted gases from the reaction chamber 18 prior to and / or following the delivery of the reactant gases. The purge gas may be provided from the purge gas source 40 to the inlet 14 via the gas conduit 50. The valve V2 and the MFC 52 may be used to control the flow of the purge gas to the reactor 12.

[0042] Referring now to FIGS. 2-4, a flowchart 100 representing an exemplary method for fabricating CMC components using the exemplary system of FIG. 1 is illustrated. At the exemplary steps 110 and 120 of FIG. 2, one or more fibrous preforms 36 may be provided and selectively placed within the reactor 12 of the assembly 10 for densification. The fibrous preform 36 may comprise fibers or fiber tows, which may be woven, non-woven, or selectively placed. Suitable fiber materials may include SiC and carbon. Additional suitable fiber materials may include, but are not limited to silicon oxycarbide (SiOC), silicon nitride (SisN^, silicon carbonitride (SiCN), hafnium carbide (HfC), tantalum carbide (TaC), silicon borocarbonitride (SiBCN), and silicon aluminum carbon nitride (SiAICN). In at least one embodiment, an interface coating may be applied to the fibers of the fibrous preform 36 by infiltrating the fibrous preform 36 with the gas from the reactant gas source 38. The interface coating material may be applied to resist crack propagation and improve a bond between the fibers and matrix material. The interface coating material may include, but are not limited to, boron nitride, pyrocarbon, silicon nitride, silicon carbide, combinations thereof, and the like.

[0043] Once the CVI process temperature is achieved, the reactant gas comprising the interface coating precursor gas from the reactant gas source 38 may be introduced into the reactor 12. Valve VI may be opened to allow flow of interface coating precursor gas into the reaction chamber 18. The flow of the interface coating precursor gas may be controlled by the MFC 52 shown in FIG. 1 and may be varied to control the amount of interface coating precursor gas introduced into the reactor chamber 18. The interface coating precursor gas may infiltrate the fibrous preforms 36 and deposit one or more interface coating material layers on and within each fibrous preform 36.RTX Ref. No. 180038US01MWZB Ref. No. RTXPW-0053-V01

[0044] Once the fibers are coated with the interface coating material, the reactor 12 may be prepared for densifying the porous fibrous preforms. The reactor 12 may be purged by an inert gas by closing valve VI and opening valve V3 to introduce the purge gas to the reactor 12. At an exemplary step 130 of FIG. 2, the reactor 12 may be heated to a CVI process temperature for matrix densification of the fibrous preform 36.

[0045] Next, at an exemplary step 140 of FIG. 2, the fibrous preforms 36 may be densified by infiltrating the fibrous preform 36 with a matrix precursor gas from the reactant gas source 40 to form a SiC matrix. The matrix precursor gas may be introduced into the reactor 12 from the reactant gas source 40 by opening valve V2. The flow of the matrix precursor gas may be controlled by the MFC 52 shown in FIG. 1 and may be varied to control the amount of reactant gas introduced into the reactor chamber 18. Next, at an exemplary step 150 of FIG. 3, the matrix precursor gas may decompose into the matrix material and a poisoning molecule. In at least one embodiment, the matrix precursor gas may comprise methyltrichlorosilane, dimethylchlorosilane, silicon tetrachloride combined with methane, combinations thereof, and the like. Upon decomposition, methyltrichlorosilane forms one silicon carbide atom and three hydrochloric acid atoms. Silicon carbide may act as the matrix material, while hydrochloric acid may act as the poisoning molecule.

[0046] Next, at an exemplary step 160 of FIG. 3, the aforementioned kinetic-to-diffusion ratio may be controlled. Hydrochloric acid, a by-product of the reaction of methyltrichlorosilane to form SiC, may act as a poisoning molecule and inhibit the deposition of the SiC through the porous fibrous preforms at an exemplary step 170 (See FIG. 3). The methyltrichlorosilane may react with the porous dummy preform. This reaction increases a concentration of the hydrochloric acid within the reaction chamber. With the increased concentration, the hydrochloric acid diffuses throughout the fibrous preforms and poisons the deposition of SiC. As a result, the matrix material begins depositing uniformly throughout, within and on the porous fibrous preforms at an exemplary step 180 (See FIG. 4). The uniform deposition of the matrix material may be confirmed by the post-deposition weight of each fibrous preform. As a result ofRTX Ref. No. 180038US01MWZB Ref. No. RTXPW-0053-V01 carrying out the exemplary method, one or more silicon carbide composite materials may be fabricated at an exemplary step 190 of FIG. 4.

[0047] While the present disclosure has been particularly described, in conjunction with specific preferred embodiments, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. It is therefore contemplated that the appended claims will embrace any such alternatives, modifications and variations as falling within the true scope and spirit of the present disclosure.

Claims

RTX Ref. No. 180038US01MWZB Ref. No. RTXPW-0053-V01CLAIMSWhat is claimed is:

1. A method for fabricating a composite material using chemical vapor infiltration, comprising: providing one or more fibrous preforms and a porous dummy preform; positioning the fibrous preforms proximate to the porous dummy preform and an area where a poisoning molecule is generated within a reaction chamber of a chemical vapor infiltration assembly; heating the reaction chamber to a chemical vapor infiltration temperature for matrix densification; introducing into the reaction chamber a matrix precursor gas; reacting the matrix precursor gas with the porous dummy preform to deposit a matrix material and generate a poisoning molecule; depositing uniformly one or more coating layers of the matrix material on and within the fibrous preforms; and fabricating one or more composite materials.

2. The method of claim 1, further comprising controlling a kinetic-to-diffusion ratio of the deposition rate of the matrix material.

3. The method of claim 2, further comprising inhibiting the deposition of the matrix material throughout the fibrous preforms by the poisoning molecule.

4. The method of claim 1, wherein the matrix precursor gas comprises one or more of: methyltrichlorosilane, dimethylchlorosilane, or silicon tetrachloride and methane; the matrix material comprises silicon carbide; and, the poisoning molecule comprises a hydrochloric acid.RTX Ref. No. 180038US01MWZB Ref. No. RTXPW-0053-V015. The method of claim 1, further comprising reacting the matrix precursor gas with the porous dummy preform, increasing a concentration of the poisoning molecule within the reaction chamber, and diffusing the matrix material throughout the fibrous preforms.

6. The method of claim 1, wherein the deposition of silicon carbide in the fibrous preform is uniform throughout a thickness of the fibrous preform.

7. The method of claim 1, wherein the porous dummy preform comprises one or more of a reticulated vitreous carbon foam, a carbon preform, a carbon felt, a sacrificial fibrous preform, and combinations thereof.

8. The method of claim 7, wherein the sacrificial fibrous preform comprises any one or more of silicon carbide, carbon, silicon oxycarbide, silicon nitride, silicon carbonitride, hafnium carbide, tantalum carbide, silicon borocarbonitride, silicon aluminum carbon nitride, and combinations thereof.

9. The method of claim 1, wherein the fibrous preform comprises any one or more of silicon carbide, carbon, silicon oxycarbide, silicon nitride, silicon carbonitride, hafnium carbide, tantalum carbide, silicon borocarbonitride, silicon aluminum carbon nitride, and combinations thereof.

10. The method of claim 1, further comprising replacing the porous dummy preform with a subsequent porous dummy preform.

11. A method for fabricating a ceramic matrix composite using chemical vapor infiltration, comprising: providing one or more fibrous preforms and a porous dummy preform;RTX Ref. No. 180038US01MWZB Ref. No. RTXPW-0053-V01 positioning the fibrous preforms proximate to the porous dummy preform and an area where a poisoning molecule is generated within a reaction chamber of a chemical vapor infiltration assembly; heating the reaction chamber to a chemical vapor infiltration temperature for matrix densification; introducing into the reaction chamber a matrix precursor gas; reacting the matrix precursor gas with the porous dummy preform to deposit silicon carbide and generate a hydrochloric acid as a poisoning molecule; increasing a concentration of the hydrochloric acid within the reaction chamber; diffusing the hydrochloric acid throughout the fibrous preforms; depositing the matrix precursor gas throughout the fibrous preforms; depositing uniformly one or more coating layers of the silicon carbide on and within the fibrous preforms; and fabricating one or more silicon carbide ceramic matrix composites.

12. The method of claim 11, further comprising controlling a kinetic-to-diffusion ratio of the deposition rate of the silicon carbide.

13. The method of claim 12, further comprising inhibiting the deposition of the silicon carbide throughout the fibrous preforms by the hydrochloric acid.

14. The method of claim 11, wherein the matrix precursor gas comprises one or more of: methyltrichlorosilane, dimethylchlorosilane, or silicon tetrachloride and methane.

15. The method of claim 11, wherein the deposition of silicon carbide in the fibrous preform is uniform throughout a thickness of the fibrous preform.RTX Ref. No. 180038US01MWZB Ref. No. RTXPW-0053-V0116. The method of claim 11, wherein the porous dummy preform comprises one or more of a carbon foam, a carbon preform, a carbon felt, a sacrificial fibrous preform, and combinations thereof.

17. The method of claim 16, wherein the sacrificial fibrous preform comprises any one or more of silicon carbide, carbon, silicon oxycarbide, silicon nitride, silicon carbonitride, hafnium carbide, tantalum carbide, silicon borocarbonitride, silicon aluminum carbon nitride, and combinations thereof.

18. The method of claim 16, wherein the fibrous preform comprises any one or more of silicon carbide, carbon, silicon oxycarbide, silicon nitride, silicon carbonitride, hafnium carbide, tantalum carbide, silicon borocarbonitride, silicon aluminum carbon nitride, and combinations thereof.

19. The method of claim 11, further comprising replacing the porous dummy preform with a subsequent porous dummy preform.

20. A chemical vapor infiltration assembly, comprising: a reactor comprising one or more gas inlets, gas outlets, and reaction chambers; one or more reactant gas sources fluidly connected to the gas inlet; a purge gas source fluidly connected to the gas inlet; one or more vacuum pumps fluidly connected to the gas outlet; the reaction chamber comprises: a mixing chamber; one or more levels defined by one or more gas distributor plates; one or more preheaters disposed proximate the gas distributor plate; one or more porous dummy preforms disposed proximate to and between the preheater and the gas distributor plate.RTX Ref. No. 180038US01MWZB Ref. No. RTXPW-0053-V0121. The chemical vapor infiltration assembly of claim 19, wherein the reactant gas sources comprise a matrix precursor gas source.

22. The chemical vapor infiltration assembly of claim 19, wherein the porous dummy preform comprises a carbon foam, a carbon preform, a carbon felt, a sacrificial fibrous preform, and combinations thereof.

23. The chemical vapor infiltration assembly of claim 19, wherein the fluid connection between the one or more reactant gas sources and the gas inlet further comprises one or more valves and one or more mass flow controllers.

24. The chemical vapor infiltration assembly of claim 19, wherein the fluid connection between the purge gas source and the gas inlet further comprises one or more valves and one or more mass flow controllers.

25. The chemical vapor infiltration assembly of claim 19, wherein the fluid connection between the one or more vacuum pumps and the gas outlet further comprises one or more valves and a pressure monitor.

26. The chemical vapor infiltration assembly of claim 19, wherein the reactant gas sources further comprise an interface precursor gas.

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