Conversion of silicon to silicon carbide for the production of ceramic matrix composites

Abstract

Techniques and methods for producing silicon carbide and ceramic matrix composites from hydrocarbons are disclosed. In one aspect, the method includes preforming a shape using silicon carbide fibers disposed in a chamber, evacuating the chamber to draw a silicon and polymer slurry into the chamber, and pressurizing the chamber to infiltrate the silicon carbide fibers with the silicon and polymer slurry. The method includes heating the chamber to pyrolyze the polymer and hydrocarbons passed through the chamber into carbon and hydrogen gas. The carbon from the pyrolyzed polymer and hydrocarbon provides a carbon coating on the silicon and silicon in the polymer slurry. The method includes heating the chamber to an elevated temperature to melt the silicon and react with the carbon to form silicon carbide. The formed silicon carbide and silicon carbide fibers form a ceramic matrix composite.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This patent document claims the benefit of and priority to U.S. Patent Application No. 17 / 018,921, filed in the U.S. Patent and Trademark Office on September 11, 2020. The entire contents of the aforementioned patent application are incorporated by reference as part of the disclosure of this application.

[0002] This patent document relates to silicon carbide and ceramic matrix composites for a variety of applications. [Background technology]

[0003] Silicon carbide is used in a wide variety of applications, including automotive clutches, ceramic plates, bulletproof vests, light emitting diodes, semiconductor detectors, nuclear cladding, and many other applications. Summary of the Invention [Problem to be solved by the invention]

[0004] The various existing methods for producing silicon carbide tend to be slow processes, in some cases requiring over 1000 hours to produce a silicon carbide article. To make silicon carbide a more practical material for industrial, scientific, and military uses, new techniques are needed to more rapidly produce silicon carbide and ceramic matrix composites. [Means for solving the problem]

[0005] This patent document discloses techniques and methods for producing silicon carbide and ceramic matrix composites from hydrocarbons.

[0006] In one aspect, a method of manufacturing a ceramic matrix composite is provided, the method comprising the steps of placing a silicon carbide preform in a chamber; evacuating the chamber using a vacuum and introducing a slurry mixture of silicon particles and a polymer into the chamber to contact the silicon carbide preform; pressurizing the chamber to infiltrate the silicon particles and polymer slurry between the silicon carbide fibers of the silicon carbide preform; and heating the chamber to a first elevated temperature to pyrolyze the polymer into carbon and hydrogen gases and densify the silicon particles between the silicon carbide fibers of the silicon carbide preform. passing a hydrocarbon into a chamber, the heated chamber causing the hydrocarbon to pyrolyze into carbon and hydrogen gas, and causing the carbon from the pyrolyzed polymer and the carbon from the pyrolyzed hydrocarbon to coat onto the silicon particles between the silicon carbide fibers of the silicon carbide preform; stopping the passage of the hydrocarbon when a desired molar ratio of silicon:carbon is reached; and heating the chamber to a second, higher temperature to melt the silicon particles and react with the carbon to form silicon carbide, with the formed silicon carbide and silicon carbide fibers forming a SiC ceramic matrix composite.

[0007] In another aspect, a method for producing carbon-coated silicon particles for silicon carbide composites is disclosed, the method comprising the steps of passing a hydrocarbon through a chamber containing silicon powder, heating the chamber to a first temperature to pyrolyze the hydrocarbon into carbon and hydrogen gas, the carbon from the hydrocarbon providing a carbon coating on the silicon powder, and terminating the passage of the hydrocarbon when a silicon:carbon molar ratio of 1:1 is reached.

[0008] In another aspect, an apparatus for producing silicon carbide is disclosed. The apparatus includes a chamber configured to include a hollow interior, with silicon particles located within the hollow interior. The apparatus further includes a fluid supply system coupled to the chamber to controllably supply into the chamber a selected fluid, including a gas and / or liquid, including a first fluid that can be decomposed into hydrogen and carbon. The apparatus includes a heating system coupled to the chamber to controllably determine the temperature of the interior of the chamber. The apparatus further includes a control system coupled to the fluid supply system to control the supply of the selected fluid into the chamber, the control system controlling the fluid supply system to pass the first fluid through the chamber, thereby causing the first fluid to decompose into produced hydrogen gas and carbon, which deposits on the silicon particles to produce carbon-coated silicon particles.

[0009] These and other aspects and their implementations are described in more detail in the drawings, specification, and claims. [Brief explanation of the drawings]

[0010] [Figure 1A] FIG. 1 illustrates a method of converting silicon (Si) powder to silicon carbide (SiC) powder, according to some exemplary embodiments. [Figure 1B] 1 is a graph showing an example of X-ray diffraction measurements showing the presence of elemental Si and the absence of SiC after flowing methane (CH) at 1000°C for 1 hour, and the presence of SiC and the absence of elemental Si after heating at 1100°C for an additional 3 hours. [Figure 2A] FIG. 10 illustrates another method, according to some exemplary embodiments. [Figure 2B] FIG. 1 illustrates a method of manufacturing a SiC composite, according to some exemplary embodiments. [Figure 2C] FIG. 1 illustrates a method for pre-forming and densifying a Si / SiC composite, according to some example embodiments. [Figure 2D]FIG. 1 illustrates another method of preforming and densifying a Si / SiC composite, according to some example embodiments. [Figure 3] 1 is a graph showing an example plot of ion current from a residual gas analyzer as a function of various outlet gas temperatures. [Figure 4] FIG. 1 shows an example of an X-ray diffraction plot of a material showing silicon, carbon, and silicon carbide after 3 hours at 1100° C. [Figure 5] FIG. 1 illustrates a method of manufacturing a ceramic matrix composite, according to some exemplary embodiments. [Figure 6] FIG. 1 illustrates a method for producing carbon coated silicon particles, according to some exemplary embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0011] Techniques and methods for producing silicon carbide (SiC) are disclosed.

[0012] FIG. 1A illustrates an example method 100 for converting silicon (Si) powder particles 120 to SiC powder particles 140 according to some illustrative embodiments. In FIG. 1A, Si powder is exposed to methane (CH4) at high temperature, causing carbon from the decomposed methane to coat the Si powder particle surfaces at, for example, about 1000°C. The silicon powder can have a variety of particle sizes, including, for example, from less than 100 nanometers (nm) to several microns. A hydrocarbon material 110, for example, CH4, is directed to flow through a chamber or furnace containing Si powder particles 130 at high temperature, causing the hydrocarbon material 110 to decompose into carbon and hydrogen, thereby exposing the Si powder particles 130 to carbon and hydrogen. The high temperature in the chamber or furnace is set (e.g., 1000°C) to decompose the hydrocarbon material 110 and produce a carbon coating on the Si powder particles 130, but is not set high enough to cause significant conversion of the coated C and Si powder particles 130 to SiC. This process can be controlled to occur over a period of time long enough (e.g., about 1 hour) to allow the C to infiltrate the Si powder and coat the surfaces of the Si powder particles 130. Once sufficient carbon coating is achieved, the CH flow is terminated, an inert gas, e.g., argon (Ar), is introduced into the chamber or furnace, and the temperature of the chamber or furnace is raised to a second, higher temperature above 1000°C, e.g., 1100°C, to react the coated carbon with the Si of the Si powder particles 130. This conversion process can be set for a sufficiently long time, e.g., 3 hours, to convert the carbon-coated Si to β-SiC 140. At 150, a photograph of an example of Si powder before the above coating and conversion process is shown, and at 160, a photograph of an example of converted SiC powder is shown.

[0013] Figure 1B shows an example of an X-ray diffraction measurement at 170 showing that after flowing CH4 through Si powder at 1000°C for 1 hour, only elemental Si was present in the chamber, with no significant SiC detected. Figure 1B further shows at 180 that after heating in Ar gas at 1100°C for an additional 3 hours after termination of the CH4 flow, SiC was present in the chamber without significant elemental Si present in the chamber.

[0014] The above method can be implemented using a variety of SiC structures to produce SiC based on the method of Figure 1 A. Figures 2A-2D show some examples.

[0015] FIG. 2A illustrates an example of a method for converting Si to SiC using Si powder, according to some illustrative embodiments. In FIG. 2A, Si powder 210 is coated with C227 from the thermal decomposition (also known as decomposition) of methane (CH4) at 1000°C. Hydrogen gas (H2) 225 is also produced from the decomposition of CH4. The silicon powder 210 can have a particle size of less than 25 microns. In some implementations, the silicon particles may be less than 100 nanometers (nm) in size. In other implementations, the silicon particles in the silicon and polymer slurry can be configured to have a size between 20 nanometers (nm) and 25 microns. The C-coated Si215 is then heated to 1414°C, the melting point of Si, to melt the Si. The molten Si reacts with the C coating to form SiC, producing aggregates of SiC220 instead of separated SiC particles. The aforementioned SiC production can be expressed as follows: Si (l) +C (S) →SiC (s) Formula 1.

[0016] FIG. 2B illustrates an example of a method for manufacturing a SiC composite by using Si powder particles 210 packed into the interstices between an array, matrix, or bundle of SiC fibers 230, according to some exemplary embodiments, using the method of FIG. 2A. At 240, the Si powder 210 is packed into the spaces between the SiC fibers 230 to produce a preform. The SiC fibers 230 can be arranged in various configurations as a preform for the final SiC material or structure after conversion. For example, the SiC fibers 230 can be arranged as layers of SiC fibers 230, with Si powder packed between the layers and pressed into a mold or other structure that holds a predetermined shape so that the Si powder particles contact the SiC fibers in a furnace. At 250, a Si coating process is performed by flowing CH4 through the Si powder particles and SiC fibers while heating the furnace to approximately 1000°C, decomposing the CH4 into C and H2 and coating the surfaces of the Si powder particles with C215. The flow of CH4 is controlled to produce a desired ratio between Si and C, for example, a 1:1 Si:C ratio. At 1000°C, SiC is not significantly formed from the Si powder and C coating. At 260, the C-coated Si and SiC fibers are heated to a higher temperature, above 1000°C, to convert the Si and C to SiC, and the SiC particles are consolidated at, for example, 1414°C, the melting point of Si. The C coating reacts with the molten Si to produce SiC, as shown by Equation 1. This conversion process is maintained for a period long enough (e.g., several hours) to convert the C-coated Si powder particles between the SiC fibers to SiC, and the converted SiC fuses with the SiC fibers to form a SiC ceramic matrix composite (CMC).

[0017] FIG. 2C illustrates one exemplary method for preforming and densifying a Si / SiC composite according to some exemplary embodiments based on the method of FIG. 1A.

[0018] At 252, a preform of silicon carbide fibers 230 and silicon powder particles 210 is formed by connecting a vacuum 213 to chamber 212 through valve 271 and then evacuating chamber 212 by closing valve 271. Evacuation of chamber 212 draws the Si and polymer slurry 270 into chamber 212. Examples of polymers in the polymer slurry include: 1) QPAC40, i.e., poly(propylene carbonate), which can be decomposed into gas at high temperatures without producing residue. QPAC40 allows for easy control of the amount of carbon coating because the carbon comes from the pyrolysis of CH4 rather than the polymer. See, for example, QPAC40 (https: / / empowermaterials.com / wp-content / uploads / 2014 / 11 / QPAC-40-Technical-Data-Sheet.pdf, incorporated by reference herein). 2) PVA, or poly(vinyl alcohol), which decomposes at high temperatures to produce carbon that coats the silicon surface, requiring less carbon from CH4 and thus reducing processing time. Pressurized inert gas 211 is then introduced into chamber 212 to force the Si powder and slurry into the SiC fibers and dry the Si / SiC to produce a preform.

[0019] In 254, chamber 212 is heated to approximately 1000°C to cause pyrolysis of the polymer into gases and carbon. CH4275 or another hydrocarbon can be added by opening valve 273, which decomposes into C and H2 when heated to 1000°C. The pyrolysis of the polymer and decomposition of the hydrocarbon provides C, which coats the Si particles. The hydrocarbon flow can be stopped when the Si:C ratio reaches 1:1.

[0020] At 256, the Si / SiC is densified by heating the chamber 212 to a temperature of 1414° C. or higher. The preform may be further pressed together by mechanical means or by high pressure gas, such as in a preforming step. The Si in the C-coated Si 215 melts and reacts with the C to form SiC, which adheres to the SiC fibers 230 to form the CMC.

[0021] FIG. 2D illustrates another method of preforming and densifying a SiC composite, according to some example embodiments.

[0022] In 282, chamber 285 containing Si powder is heated to approximately 1000°C. CH4275 or another hydrocarbon is added by opening valve 273. For example, CH4275 may be added, which decomposes into C and H2 at a temperature of 1000°C. The decomposition of the hydrocarbon provides C, which coats the Si particles to produce C-coated Si particles 215. The flow of hydrocarbon may be stopped when the Si:C ratio reaches 1:1. Other methods of producing C-coated Si 215 may also be used.

[0023] At 286, the C-coated Si powder 215 produced at 282 is added to a polymer to create a slurry 290. The slurry 290 is preformed with silicon carbide fibers 230 by 1) connecting a vacuum 213 to the chamber 285 through valve 271 and then pulling a vacuum on the chamber 285 by closing valve 271, 2) evacuating the chamber 285 to draw the slurry 290 into the chamber 285, 3) connecting a pressurized inert gas 211 to the chamber 285 to force the Si powder and slurry into fibers, and 4) drying the Si / SiC composite to produce a preform.

[0024] At 288, the Si / SiC composite is densified by heating the chamber 285 to a temperature of 1414°C or higher. The preform may be further pressed together by mechanical means or by high pressure gas. The polymer in the slurry 290 decomposes into C and H. The Si in the C-coated Si 215 melts and reacts with the C from the coating and polymer decomposition to form SiC, which adheres to the SiC fibers 230 to form the CMC.

[0025] Figure 3 shows an example plot of ion current from a residual gas analyzer as a function of temperature for various outlet gases. Figure 3 shows that CH4 310 decomposes cleanly above 1000°C to form carbon and hydrogen 305, and that very little methane decomposes below 1000°C. Carbon preferentially coats silicon surfaces, keeping the system clean, including the sample surface, and keeping the chamber 212 / 285 clean. Methane flows through the sample, producing a uniform carbon coating of Si powder within the chamber. Also shown at 300 are other outlet gases, including low percentages of CH2 315, CH6 320, and CH6 325.

[0026] The disclosed technology and method can be used to fabricate parts and components thicker than the maximum thickness feasible using conventional chemical vapor infiltration (CVI) processing techniques. The disclosed technology, for example, uses a small hydrocarbon such as CH4, allowing CH4, and therefore C, to penetrate deep into the structure, facilitating the fabrication of thicker parts. CH4 penetrates small pores and does not stop the flow of CH4. Another advantage of CH4 is that C decomposes only on the desired Si surface and not elsewhere. When silicon has a thin carbon coating, the rate of C coating is slow. Rather than adding C to the already coated Si surface, CH4 decomposes, and thus C is deposited on other bare silicon surfaces.

[0027] CH4 decomposes into carbon and hydrogen. H2 is a smaller molecule than CH4, so it has higher mobility than CH4. Therefore, H2 quickly escapes from the silicon composite part, and the decomposition does not cause pressure buildup inside the part.

[0028] Currently, methods used to manufacture SiC CMCs include chemical vapor infiltration (CVI), silicon melt infiltration (MI), and polymer infiltration (PIP). Each of these methods has disadvantages compared to the disclosed technique. For example, CVI requires a processing time of up to 1,000 hours, while the disclosed technique requires only 10 hours or less. While CVI can only be used to manufacture parts approximately 1-2 mm thick, the disclosed technique can manufacture parts approximately 1 cm thick (or thicker). The disclosed technique has better uniformity in the density of manufactured parts than parts manufactured using CVI. Also, CVI generates HCl gas, whereas the disclosed technique does not. While conventional MI, in which molten silicon reacts with a carbon preform, tends to leave residual unreacted Si even at 1414°C, the disclosed technique allows for the reaction of all Si. PIP has low volumetric density and requires many thermal cycles and long high-temperature heat treatments to avoid amorphous SiC.

[0029] One of the challenges in manufacturing SiC composites is that shrinkage during conversion to SiC limits the density of the finished part, potentially resulting in a lower-than-desired density. SiC has a density of 3.1 g / cc, which is higher than Si, which has a density of 2.35 g / cc, and C, which has a density of 2.4 g / cc. The increased density of the SiC product causes its volume after formation to shrink to approximately 76% of the volume of the components Si and C. With a typical fiber volume of 33%, the overall composite volume density is approximately 84%.

[0030] The disclosed technology allows for denser composites with densities greater than 90%. Designing pressable parts, such as pressing with a plate, when silicon is melted results in a nearly 100% solid part. Mixing SiC powder with Si powder increases the initial SiC volume fraction, increasing the density of the finished part. The use of SiC fibers also increases the density of the finished part. Multiple cycles can be performed, with Si powder having smaller Si particle sizes in subsequent cycles. MTS CVI or polymer infiltration pyrolysis can also be used after the first cycle for further densification.

[0031] FIG. 4 shows an example of an X-ray diffraction plot of a material showing silicon, carbon, and silicon carbide after heating at 1100°C for 3 hours. In some exemplary embodiments, the Si powder may be pre-coated with C. At 1100°C, Si is quickly coated with C, and SiC does not form in the presence of hydrocarbons, such as CH. For example, coating occurs with a 2:1 C:Si mass ratio (or a 5:1 molar ratio) and a 3-hour coating time with CH. In some exemplary embodiments, a 1:1 Si:C ratio can be achieved after 30 minutes. The pre-coated Si can then be used in various ways and converted to SiC. For example, carbon-coated powder can be packed into a preform. Then, by heating to a temperature of 1414°C or higher, the Si melts and converts to SiC or CMC. No other gases are required. The above method is particularly well suited for pressable parts.

[0032] Because the disclosed techniques and methods do not produce corrosive gases, such as MTS gas and / or HCl, as by-products, the disclosed techniques can be used to produce other carbide composites using fibers, such as metal or ceramic fibers in a SiC matrix. This technique can also be used with other carbide matrix materials, provided the appropriate reaction conditions between the metal and carbon are met. For example, instead of using silicon particles, zirconium metal powder can be used to form a zirconium carbide matrix.

[0033] FIG. 5 illustrates a method for manufacturing a ceramic matrix composite, according to some exemplary embodiments. At 510, the method includes preforming a shape using silicon carbide fibers. For example, the shape may be a mechanical or structural part for a system or device. The preformed part is placed in a chamber. At 520, the method includes evacuating the chamber using a vacuum. Removing pressure from the chamber draws a slurry containing silicon and a polymer into the chamber. At 530, the method includes pressurizing the chamber to infiltrate the silicon and polymer slurry into the silicon carbide fibers. At 540, the method includes heating the chamber to a first temperature to pyrolyze the polymer into carbon and hydrogen gas. For example, the first temperature may be about 1000° C. At 550, the method includes passing a hydrocarbon into the chamber. The heated chamber pyrolyzes the hydrocarbon into carbon and hydrogen gas. The carbon from the pyrolyzed polymer and the carbon from the pyrolyzed hydrocarbon coat the silicon from the slurry with a layer of carbon. At 560, the method includes stopping the passage of the hydrocarbon when a 1:1 molar ratio of silicon to carbon is reached. At 570, the method includes heating the chamber to a second temperature to melt the silicon. For example, the second temperature may be about 1414°C, the melting point of silicon. The molten silicon reacts with the carbon to form silicon carbide, and the formed silicon carbide and silicon carbide fibers form a ceramic matrix composite.

[0034] 6 illustrates a method for producing carbon-coated silicon particles according to some exemplary embodiments. At 610, the method includes passing a hydrocarbon through a chamber containing silicon powder. At 620, the method includes heating the chamber to a first temperature to pyrolyze the hydrocarbon into carbon and hydrogen gas, with the carbon from the hydrocarbon providing a carbon coating on the silicon powder. At 630, the method includes stopping the passage of the hydrocarbon when a silicon:carbon molar ratio of 1:1 is reached. The present invention includes the following aspects. [Section 1] 1. A method for manufacturing a ceramic matrix composite, comprising: placing a silicon carbide preform in a chamber; evacuating the chamber using a vacuum and introducing a slurry mixture of silicon particles and a polymer into the chamber and into contact with the silicon carbide preform; pressurizing the chamber to cause the silicon particles and polymer slurry to infiltrate between the silicon carbide fibers of the silicon carbide preform; heating the chamber to a first elevated temperature to pyrolyze the polymer into carbon and hydrogen gases to densify the silicon particles between the silicon carbide fibers of the silicon carbide preform; passing a hydrocarbon through a chamber, the heated chamber causing the hydrocarbon to pyrolyze into carbon and hydrogen gas, and causing carbon from the pyrolyzed polymer and carbon from the pyrolyzed hydrocarbon to coat on silicon particles between the silicon carbide fibers of the silicon carbide preform; stopping the passage of hydrocarbons when a desired molar ratio of silicon:carbon is reached; heating the chamber to a second, higher temperature to melt the silicon particles and react with the carbon to form silicon carbide, the resulting silicon carbide and silicon carbide fibers forming a SiC ceramic matrix composite; A method comprising: [Section 2] Item 1. The method of item 1, wherein the first temperature is about 1000°C. [Section 3] Item 1, wherein the second temperature is about 1414°C. [Section 4] Using silicon particles having a particle size between 20 nanometers (nm) and 25 microns in a silicon and polymer slurry. The method according to item 1, comprising: [Section 5] When the chamber is heated to a second temperature, the molten silicon and carbon Si (l) +C (s) →SiC (s) The method according to item 1, wherein the reaction represented by the following formula is induced: [Section 6] passing argon gas into the chamber after stopping the passage of hydrocarbons. The method of claim 1, further comprising: [Section 7] The hydrocarbon is methane (CH 4 Item 1. The method according to item 1, comprising: [Section 8] Item 10. The method of claim 1, wherein the hydrocarbon comprises diesel, gasoline, JP8, kerosene, natural gas, propane, ethane, butane, or another hydrocarbon gas. [Section 9] 1. A method for producing carbon coated silicon particles for silicon carbide composites, comprising: passing a hydrocarbon into a chamber containing silicon powder; heating the chamber to a first temperature to pyrolyze the hydrocarbon into carbon and hydrogen gas, the carbon from the hydrocarbon providing a carbon coating on the silicon powder; stopping the passage of hydrocarbons when a desired molar ratio of silicon:carbon is reached; A method comprising: [Section 10] preparing a slurry comprising carbon coated silicon particles and a polymer; pressurizing the chamber to cause the slurry to penetrate the silicon carbide fibers in the chamber; Item 10. The method of item 9, further comprising: [Section 11] heating the chamber to a second temperature to melt the silicon particles, the molten silicon particles reacting with the carbon to form silicon carbide, and the resulting silicon carbide and silicon carbide fibers forming a ceramic matrix composite. Item 10. The method of item 9, further comprising: [Section 12] prior to pressing, disposing the silicon carbide fibers in a preformed shape, the shape being disposed within a chamber. Item 10. The method of item 9, further comprising: [Section 13] Item 10. The method of item 9, further comprising, after stopping, heating the chamber to 1100°C to convert the silicon powder and carbon to silicon carbide. [Section 14] The hydrocarbon is methane (CH 4 Item 10. The method according to item 9, comprising: [Section 15] 10. The method of paragraph 9, wherein the hydrocarbon is diesel, gasoline, JP8, kerosene, natural gas, propane, ethane, butane, or another hydrocarbon gas. [Section 16] 1. An apparatus for producing silicon carbide, comprising: a chamber configured to include a hollow interior, the silicon particles being located within the hollow interior; a fluid supply system coupled to the chamber to controllably supply selected fluids, including gases and / or liquids, into the chamber, including a first fluid that can be decomposed into hydrogen and carbon; and a heating system coupled to the chamber to controllably determine a temperature within the chamber; a control system coupled to the fluid supply system to control supply of a selected fluid into the chamber, the control system controlling the fluid supply system to pass a first fluid through the chamber, thereby causing the first fluid to decompose into produced hydrogen gas and carbon, which is deposited on the silicon particles to produce carbon-coated silicon particles; 1. An apparatus comprising: [Section 17] further comprising one or more temperature sensors for sensing a temperature inside the chamber; a fluid supply system comprising: a valve for controlling the flow of the first fluid; Item 17. The apparatus of item 16, wherein the control system includes a processor and memory including executable instructions, the executable instructions configured to control at least a fluid supply system including valves and a heating system to produce carbon-coated silicon particles. [Section 18] 17. The apparatus of paragraph 16, wherein the first fluid is methane and the heat from the chamber causes the methane to decompose into carbon and hydrogen gases. [Section 19] 17. The apparatus of paragraph 16, wherein the first fluid is diesel, gasoline, JP8, kerosene, natural gas, propane, ethane, butane, or another hydrocarbon gas.

[0035] While this patent document contains many details, these should not be construed as limitations on the scope of any invention or what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of a particular invention. Certain features that are described in this patent document in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, while features may be described above as acting in a particular combination and may even initially be claimed as such, one or more features from a claimed combination may, in some cases, be deleted from the combination, and the claimed combination may be directed to a subcombination or a variation of the subcombination.

[0036] Similarly, although actions are depicted in a particular order in the figures, this should not be understood as requiring such actions to be performed in the particular order shown, or sequentially, or that all of the actions shown be performed, to achieve desirable results. Furthermore, the separation of various components in the embodiments described in this patent document should not be understood to require such separation in all embodiments.

[0037] Only a few implementations and examples have been described, and other implementation improvements and modifications can be made based on what is described and illustrated in this patent document. [Explanation of symbols]

[0038] 110: Hydrocarbon material, 120: Silicon (Si) powder particles, 130: Si powder particles, 140: β-SiC, 150: Si powder before conversion method, 160: Converted SiC powder

Claims

1. A method for producing a silicon carbide (SiC) ceramic matrix composite, comprising: placing a silicon carbide preform in a chamber; evacuating the chamber using a vacuum and introducing a slurry mixture of silicon particles and a polymer into the chamber and into contact with the silicon carbide preform; pressurizing the chamber to cause the silicon particles and polymer slurry to infiltrate between the silicon carbide fibers of the silicon carbide preform; heating the chamber to a first temperature below the melting point of silicon to pyrolyze the polymer into carbon and hydrogen gas to densify the silicon particles between the silicon carbide fibers of the silicon carbide preform; passing a hydrocarbon through a chamber, the heated chamber causing the hydrocarbon to pyrolyze into carbon and hydrogen gas, and causing carbon from the pyrolyzed polymer and carbon from the pyrolyzed hydrocarbon to coat on silicon particles between the silicon carbide fibers of the silicon carbide preform; stopping the passage of hydrocarbons when a desired molar ratio of silicon to carbon is reached; heating the chamber to a second temperature to melt the silicon particles and react with the carbon to form silicon carbide, and causing the formed silicon carbide and silicon carbide fibers to form a SiC ceramic matrix composite; A method comprising:

2. 10. The method of claim 1, wherein the first temperature is about 1000°C.

3. 10. The method of claim 1, wherein the second temperature is about 1414°C.

4. Using silicon particles having a particle size between 20 nanometers (nm) and 25 microns in a silicon and polymer slurry.

2. The method of claim 1, comprising:

5. When the chamber is heated to a second temperature, the molten silicon and carbon You (l) +C (s) →SiC (s) The method of claim 1, wherein a reaction represented by the formula:

6. passing argon gas into the chamber after stopping the passage of hydrocarbons. The method of claim 1 further comprising:

7. A method for producing a silicon carbide (SiC) ceramic matrix composite, comprising: passing a hydrocarbon into a chamber containing silicon powder and silicon carbide fibers; heating the chamber to a first temperature below the melting point of silicon to pyrolyze the hydrocarbon into carbon and hydrogen gas, the carbon from the hydrocarbon providing a carbon coating on the silicon powder to produce carbon-coated silicon particles; stopping the passage of hydrocarbons when a desired molar ratio of silicon to carbon is reached; forming a silicon carbide preform by infiltrating silicon carbide fibers with carbon coated silicon particles; heating the silicon carbide preform to a second temperature to melt the silicon within the carbon-coated silicon particles, the molten silicon reacting with the carbon to form silicon carbide, and the resulting silicon carbide and silicon carbide fibers forming a SiC ceramic matrix composite; A method comprising:

8. The step of infiltrating the silicon carbide fibers with carbon-coated silicon particles comprises: preparing a slurry comprising carbon coated silicon particles and a polymer; pressurizing the chamber to cause the slurry to penetrate the silicon carbide fibers in the chamber; 8. The method of claim 7, comprising:

9. The method of claim 7, wherein the first temperature is about 1000°C.

10. prior to pressing, disposing the silicon carbide fibers in a preformed shape, the shape being disposed within a chamber.

9. The method of claim 8, further comprising:

11. The method of claim 7, wherein the second temperature is greater than or equal to about 1100°C.

12. The hydrocarbon is methane (CH 4 8. The method of claim 1 or claim 7, comprising:

13. 8. The method of claim 1 or claim 7, wherein the hydrocarbon is diesel, gasoline, JP8, kerosene, natural gas, propane, ethane, butane, or another hydrocarbon gas.

14. The method of claim 1 or claim 7, wherein the second temperature is higher than the first temperature.

15. The method of claim 1 or claim 7, wherein the desired molar ratio of silicon to carbon is about 1.

16. The method of claim 16, wherein the first temperature is maintained within the chamber to allow pyrolysis and densification of silicon particles between the silicon carbide fibers of the silicon carbide preform to proceed for about 1 hour.

8. The method of claim 1 or claim 7, further comprising:

17. The method of claim 16, wherein the formation of the SiC ceramic matrix composite proceeds by maintaining the second temperature in the chamber for about 3 hours.

8. The method of claim 1 or claim 7, further comprising:

18. The method of claim 1 or claim 7, wherein the SiC ceramic matrix (a) does not contain excess elemental silicon and carbon, or (b) contains trace amounts of silicon and carbon.

19. The method of claim 1 or claim 7, wherein the SiC ceramic matrix has a high uniform density of at least 90% or a thickness up to 1 centimeter.

20. An apparatus for producing a silicon carbide (SiC) ceramic matrix composite, comprising: a chamber configured to include a hollow interior, the chamber having silicon particles therein; a fluid supply system coupled to the chamber to controllably supply a first fluid; a heating system coupled to the chamber to controllably determine a temperature within the chamber; a control system coupled to the fluid supply system to control supply of the first fluid into the chamber; Including, a heating system configured to heat the interior of the chamber to a first temperature below the melting point of silicon to pyrolyze the first fluid into carbon and hydrogen gas, and to further heat the interior of the chamber to a second temperature above the first temperature to cause carbon from the pyrolysis of the first fluid to form a carbon coating on the silicon particles; The apparatus, wherein the control system is configured to control the fluid supply system to pass the first fluid through the chamber and to stop supplying the first fluid into the chamber when a desired molar ratio of silicon to carbon in the carbon-coated silicon particles is reached.

21. further comprising one or more temperature sensors for sensing a temperature inside the chamber; the fluid supply system includes a valve that controls the flow of the first fluid; 21. The apparatus of claim 20, wherein the control system includes a processor and memory including executable instructions, the executable instructions configured to control at least a fluid supply system including valves and a heating system to produce the carbon-coated silicon particles.

22. 21. The apparatus of claim 20, wherein the first fluid is methane and the heat from the chamber causes the methane to decompose into carbon and hydrogen gases.

23. 21. The apparatus of claim 20, wherein the first fluid is diesel, gasoline, JP8, kerosene, natural gas, propane, ethane, butane, or another hydrocarbon gas.

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