Method for preparing silicon-carbon composite material by chemical vapor infiltration reactor

Abstract

The invention provides a method for enabling a reactor to reach set reaction conditions, wherein the set reaction conditions at least comprise that a reaction cavity is at a set temperature and the temperature is kept stable; when the porous carbon support material is input into the reactor, mixing carrier gas with a silicon-containing precursor to form reaction gas, and inputting the reaction gas into the reaction cavity through an input interface at the bottom; and maintaining the reaction until the reaction is finished. When the vertical CVI reactor is adopted to execute the chemical vapor infiltration reaction, the reaction temperature distribution in the reactor, the temperature of the microporous porous carbon support particles and the temperature of precursor reaction gas / carrier gas are very uniform and stable; more importantly, the chemical vapor infiltration reaction is very difficult to obtain, and the uniformity of the reaction temperature and the uniformity and completeness of the chemical vapor infiltration reaction in particles can be ensured without the assistance of any additional external force when the vertical CVI reactor is adopted to execute the chemical vapor infiltration reaction; particularly, chemical vapor infiltration and carbon coating work of porous carbon support particles with the size of 2-10 microns can be completed.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical vapor infiltration, and in particular relates to a method for preparing a silicon-carbon composite material by a chemical vapor infiltration reactor. Background Art

[0002] Although the use of chemical vapor infiltration to prepare porous scaffold composite materials is a feasible production method, the current feasible practical processes in the industry all use a horizontal reaction chamber. The granular porous carbon scaffold is against the flow rate of the reaction gas precursor gas in the reaction chamber, and the horizontal axial movement path of the reaction chamber is easily affected by the earth's gravity field. The particles are easily stuck at the bottom of the reaction chamber and cannot move forward evenly in a free laminar flow. Therefore, it is not easy to maintain a stable and uniform chemical vapor infiltration (CVI) reaction on its surface and micropores to generate nano-scale amorphous and / or microcrystalline silicon. Therefore, it is necessary to use a vibration external force transverse to the direction of particle movement to assist, so that the porous carbon particles can move along the axial direction of the reaction chamber toward the discharge port in a manner similar to a free laminar flow against the flow rate of the precursor gas, and produce an elutriation effect between individual particles along the direction of the external vibration force, giving the reaction gas precursor gas flow space and the opportunity to contact with each granular porous carbon scaffold surface to complete the CVI porous carbon composite material preparation process and particle transportation. Such equipment and processes can be found in the authorized patents US11611073, US11661517, JS20220055905A1, CN08475779A, CN05190948A, etc. and the published and under-examination patent applications.

[0003] PCT / US2021 / 045417, CN116323481A, CN116978701A, EP4261931A, etc.

[0004] In this horizontal particle movement process, the particles are not able to move forward evenly and stably, and the particle surface cannot be continuously and stably exposed and contacted with the reaction precursor gas, so that the CVI reaction cannot proceed smoothly, evenly and stably. Especially for irregularly shaped particles and feeding with a wide distribution of particle sizes, particles are more likely to be accidentally jammed during movement. The heating of the granular porous carbon support is also relatively uneven and unstable, which can have a bad effect on the CVI reaction effect and material production yield. At the same time, the stacked particles are prone to mutual scraping and wear on the inner wall of the reaction chamber tube. Summary of the invention

[0005] In view of the above technical problems, the present application proposes a method for preparing silicon-carbon composite materials by chemical vapor infiltration reactor. The specific technical scheme is as follows:

[0006] A method for preparing a silicon-carbon composite material by a chemical vapor infiltration reactor, wherein a vertical reactor is provided, and the method comprises:

[0007] Allowing the reactor to reach a set reaction condition, wherein the set reaction condition at least includes the reaction chamber being at a set temperature and maintaining the temperature stable;

[0008] When the porous carbon support material has been introduced into the reactor, the carrier gas is mixed with the silicon-containing precursor to form a reaction gas which is introduced into the reaction chamber through the input interface at the bottom;

[0009] The reaction was maintained until completion.

[0010] In a specific embodiment, the reactor is in a continuous production state, and the reactor is under reaction set conditions;

[0011] Or the reactor is in a non-production state, the heating zone is started to heat the reaction chamber to the reaction set conditions.

[0012] In a specific embodiment, when the reactor is in a continuous production state, the porous carbon support material is directly introduced into the reactor, and then the carrier gas is mixed with the silicon-containing precursor and introduced into the reaction chamber;

[0013] Or when the reactor is in a non-production state, the granular multi-porous porous carbon support material is fed into the reaction chamber from the feed port, and then the carrier gas is fed into the reaction chamber from the input interface at the bottom of the shell, and the purge is continued for a period of time, and then the heating zone is started to heat the reaction chamber to the reaction set conditions.

[0014] In a specific embodiment, before or after the carrier gas is mixed with the silicon-containing precursor to form the reaction gas and input into the reaction chamber through the input interface at the bottom, the carrier gas is introduced into the reactor from the bottom in a slanting manner to form the cyclone gas.

[0015] In a specific embodiment, the carrier gas is preheated before being introduced into the reaction chamber.

[0016] In a specific embodiment, the temperature range for preheating the carrier gas is 300°C to 450°C.

[0017] In a specific embodiment, the gas flow rates of the cyclone gas and the reaction gas are gradually increased while the reaction is being maintained.

[0018] In a specific implementation scheme, the preset temperatures of a plurality of heating devices with independently set heating temperatures increase from bottom to top.

[0019] In a specific implementation manner, the preset temperature of a plurality of heating devices that set the heating temperature synchronously is not lower than the highest preset temperature of a plurality of heating devices that set the heating temperature independently.

[0020] In a specific implementation scheme, the preset temperature of the plurality of heating devices that simultaneously set the heating temperature is 500°C to 610°C.

[0021] In a specific embodiment, during the reaction, the carrier gas is mixed with the silicon-containing precursor and input into the reaction chamber from the input interface at the bottom, and the silicon-containing precursor is added to the reaction chamber above the bottom of the shell.

[0022] In a specific embodiment, during the reaction, the silicon-containing precursor is intermittently or continuously added to the reaction chamber at multiple locations in the middle of the reaction chamber or from the bottom to the top.

[0023] In a specific embodiment, during the reaction, the silicon-containing precursor is replenished quantitatively or non-quantitatively or at a decreasing flow rate depending on the distance from the bottom.

[0024] In a specific embodiment, the carrier gas is nitrogen and / or an inert gas and / or hydrogen.

[0025] In a specific embodiment, the silicon-containing precursor includes one or more of silane, higher-order silane, and chlorosilane.

[0026] In a specific embodiment, the porous carbon scaffold material is replaced by an inorganic or organic porous scaffold material, or a porous scaffold material of a single phase and / or multiple single substances and / or a heterogeneous combination.

[0027] In a specific embodiment, the granular microporous porous carbon scaffold material is replaced with a granular silicon-carbon composite material, and the silicon-containing precursor is replaced with a carbon-containing precursor to prepare a carbon-coated silicon-carbon composite material.

[0028] In a specific embodiment, when the carbon-containing precursor enters the reaction chamber, the pressure change at the bottom of the reaction chamber is made to be less than 0.7 standard atmospheric pressure.

[0029] In a specific embodiment, when the carbon-containing precursor enters the reaction chamber, the pressure change at the bottom of the reaction chamber is made to be less than 0.5 standard atmospheric pressure.

[0030] In a specific embodiment, when the carbon-containing precursor enters the reaction chamber, the pressure change at the bottom of the reaction chamber is made to be less than 0.2 standard atmospheric pressure.

[0031] In a specific implementation scheme, the preset temperature of the plurality of heating devices that simultaneously set the heating temperature is 540°C to 600°C.

[0032] In a specific embodiment, the carbon-containing precursor includes one or more of methane, propane, ethylene, and acetylene.

[0033] In a specific embodiment, after the reaction is completed, the heating of the carrier gas is stopped, and the carrier gas is kept delivered to the reaction chamber.

[0034] The beneficial effects of the present invention are as follows: when the present application adopts an upright CVI reactor to perform a chemical vapor infiltration reaction, the reaction temperature distribution in the reactor, the temperature of the microporous porous carbon scaffold particles, and the temperature of the precursor reaction gas / carrier gas are all very uniform and stable; more importantly, and also very rare, the present application adopts an upright CVI reactor to perform a chemical vapor infiltration reaction without any additional external force assistance, which can ensure the uniformity of the reaction temperature and the uniformity and completeness of the chemical vapor infiltration reaction in the particles, especially the chemical vapor infiltration and carbon coating of porous carbon scaffold particles of 5 to 10 μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Shown is a schematic diagram of the structure of a chemical vapor infiltration reactor;

[0036] Figure 2 What is shown is a schematic diagram of the position status of input interface 1 and input interface 2;

[0037] Figure 3 Shown is a schematic diagram of a typical distribution curve of silane concentration from the air inlet to the air outlet;

[0038] Figure 4 Shown is a schematic diagram of the distribution curve of the initial silane concentration and the supplementary silane concentration;

[0039] Figure 5 Shown is a schematic diagram of the stable particle fluidization motion pathway;

[0040] Figure 6 Shown are TEM images of the prepared silicon-porous carbon composite material particles at different magnifications. DETAILED DESCRIPTION

[0041] In the following description, certain specific details are set forth in order to provide a thorough understanding of various embodiments. However, it will be appreciated by those skilled in the art that the present invention may be practiced without these details. In other cases, well-known structures are not shown or described in detail to avoid unnecessarily obscuring the description of the embodiments. Unless the context otherwise requires, throughout the specification and the appended claims, the word "comprising" shall be interpreted in an open, inclusive sense, i.e., as "including but not limited to".

[0042] "One embodiment" or "embodiment" mentioned throughout this specification means that in at least one embodiment, specific features, structures or characteristics related to the embodiment are included. Therefore, the phrases "in one embodiment" or "in an embodiment" appearing in various places throughout this specification do not necessarily all refer to the same embodiment. In addition, specific features, structures or characteristics can be combined in any suitable manner in one or more embodiments. In addition, as used in this specification and the appended claims, the singular forms "one / kind" and "the" include plural indicators unless the context clearly dictates otherwise. It should also be noted that the term "or" is generally used in its meaning that includes "and / or" unless the context clearly dictates otherwise.

[0043] Porous scaffold materials

[0044] For the purpose of embodiments of the present invention, chemical vapor silicon can be used to infiltrate and deposit on the inner and outer surfaces of the granular porous support. In this article, the porous support can include various materials. In some embodiments, the porous support material mainly includes carbon, such as hard carbon. In other embodiments, other allotropes of carbon are also envisioned, such as graphite, amorphous carbon, diamond, C60, carbon nanotubes (e.g., single-walled and / or multi-walled), graphene and / or carbon fiber.

[0045] Porous scaffold material also comprises polymeric material, including but not limited to inorganic polymer, organic polymer and addition polymer.The example of inorganic polymer in this article includes but not limited to the homopolymer of silicon-silicon, such as polysilane, silicon carbide, polygermane and polystannane.Other examples of inorganic polymer include but not limited to heteropolymer, such as, polyborane (polyborazylene), polysiloxane (such as polydimethylsiloxane (PDMS), polymethylhydrogensiloxane (PMHS) and polydiphenylsiloxane), polysilazane (such as perhydropolysilazane (PHPS)), polyphosphazene and poly (dichlorophosphazene), polyphosphoric acid (salt), polysulfur nitride (polythiazy1) and polysulfide.

[0046] In certain embodiments, the porous support polymer material includes a coordination polymer. The coordination polymer herein includes but is not limited to a metal organic framework (MOF). The technology for producing MOF and exemplary materials of MOF are known in the art and described ("The Chemistry and Applications of Metal-Organic Frameworks, Hiroyasu Furukawa et al., Science 341, (2013); DOI: 10.1126 / science.1230444). Examples of MOF herein include but are not limited to Basolite materials and zeolite imidazolate frameworks (ZIF).

[0047] In certain embodiments, the porous scaffold material comprises a porous ceramic material. In certain embodiments, the porous scaffold material comprises a porous ceramic foam.

[0048] In certain embodiments, porous material includes porous metal. In this regard, suitable metals include but are not limited to porous aluminum, porous steel, porous nickel, porous Inconel (Inconcel), porous Hastelloy (Hasteloy), porous titanium, porous copper, porous brass, porous gold, porous silver, porous germanium and other metals capable of forming porous structures, as known in the art. In certain embodiments, porous support material includes porous metal foam. The type of metal and its manufacture method are known in the art. Such methods include but are not limited to casting (including foaming, infiltration and low foam casting), deposition (chemical and physical), gas eutectic formation and powder metallurgy technology (for example, powder sintering, compaction and fiber metallurgy technology in the presence of foaming agent).

[0049] Porous carbon scaffold

[0050] The porous carbon scaffold can be in the form of particles, and the particle size and particle size distribution can be measured by various techniques known in the art. The particle size of the porous carbon scaffold particles can be 1-110 μm, for example, 1-5 μm, for example, 2-5 μm, for example, 3-5 μm, for example, 5-10 μm, for example, 10-15 μm, for example, 15-20 μm, for example, 20-25 μm, for example, 25-30 μm, for example, 30-35 μm, for example, 35-40 μm, for example, 40-45 μm, for example, 45-50 μm, for example, 50-55 μm, for example, 55-65 μm, for example, 65-7 0μm, for example, 70-75μm, for example, 75-80μm, for example, 80-85μm, for example, 85-90μm, for example, 90-95μm, for example, 95-100μm, for example, 100-105μm, for example, 105-110μm, for example, 1-20μm, for example, 10-40μm, for example, 20-60μm, for example, 30-80μm, for example, 50-100μm, for example, 60-110μm, for example, 20-80μm.

[0051] The pores of the porous carbon scaffold particles may be mesopores of 2-50 nm, nanoscale micropores of less than 2 nm, or macropores of greater than 50 nm.

[0052] Chemical Vapor Infiltration (CVI)

[0053] One conventional method of making composite materials is to subject a substrate material to an elevated temperature in the presence of a pyrolysis gas. A method wherein the substrate provides a porous scaffold comprising a first component of the composite, and the gas pyrolyzes into the pores of the porous scaffold material to provide a second component of the composite. For example, this CVI method can be used to produce Si-C composites.

[0054] In an embodiment, the porous carbon particles are subjected to a silicon-containing precursor gas at an elevated temperature and in the presence of a silicon-containing precursor gas to decompose the silicon-containing precursor gas into silicon, thereby generating silicon in the pores of the porous carbon support. The silicon-containing precursor gas may be mixed with other inert gases such as nitrogen. The temperature and time of the process may vary, for example, the temperature may be 200 to 900°C, for example, 200 to 250°C, for example, 250 to 300°C, for example, 300 to 350°C, for example, 300 to 400°C, for example, 350 to 450°C, for example, 350 to 400°C, for example, 400 to 500°C, for example, 500 to 600°C, for example, 600 to 700°C, for example, 700 to 800°C, for example, 800 to 900°C, for example, 600 to 1100°C.

[0055] In an embodiment, the silicon-containing precursor includes one or more of silane, higher order silane (eg, disilane, trisilane, etc.), chlorosilane (eg, monochlorosilane, dichlorosilane, etc.).

[0056] In some embodiments, the flow of the silicon-containing precursor gas is co-current, i.e., in the same direction as the porous carbon particles passing through the heating zone. In some preferred embodiments, the flow of the silicon-containing precursor gas is countercurrent, i.e., in the opposite direction of the porous carbon particles passing through the heating zone.

[0057] Preparation of Silicon-Carbon Composite Materials by CVI

[0058] The CVI process can be as follows: the granular multi-microporous porous carbon support material is introduced into the upright CVI reactor, and then the carrier gas is introduced into the CVI reactor from the bottom of the CVI reactor for continuous purge, and then the CVI reactor is heated and controlled until the temperature is stable, and then the reaction gas is introduced into the CVI reactor from the bottom of the CVI reactor.

[0059] In the implementation scheme, the granular microporous porous carbon support material is introduced into the upright CVI reactor by mixing the porous carbon support material with a carrier gas and then transporting it into the CVI reactor. The rising airflow in the CVI reactor allows the porous carbon support particles of different weights to be freely suspended at appropriate heights in the CVI reactor according to their weights. The continuous rising airflow in the CVI reactor causes the particles to collide with each other and vibrate, rotate, and move. If the particles are too light or too small, they will be transported to the upper area of ​​the CVI reactor by the carrier gas and / or the reaction gas, or leave the CVI reactor through the exhaust port of the CVI reactor and be collected and reintroduced into the CVI reactor. This process is also called "elution", which can pre-adjust the particle size distribution range of the starting material.

[0060] In an embodiment, the porous carbon support material can be introduced into the CVI reactor from any part of the CVI reactor by means of a carrier gas. In some embodiments, the porous carbon support material is introduced into the CVI reactor from the bottom of the CVI reactor by means of a carrier gas; in some embodiments, the porous carbon support material is introduced into the CVI reactor from the middle of the CVI reactor by means of a carrier gas; in some embodiments, the porous carbon support material is introduced into the CVI reactor from the top of the CVI reactor by means of a carrier gas.

[0061] The preferred solution is that the porous carbon support material is introduced into the CVI reactor from the top of the CVI reactor by means of the carrier gas, the purpose of which is to utilize the gravity of the porous carbon material to achieve a good separation of the carrier gas and the porous carbon particles; under the action of gravity, the porous carbon particles move downward, and the carrier gas moves upward into the exhaust filter and is discharged from the reactor cavity.

[0062] After the porous carbon support material is introduced, the carrier gas is introduced into the CVI reactor from the bottom of the CVI reactor for continuous purging, including the carrier gas being introduced into the CVI reactor from the center of the bottom of the CVI reactor along the axial direction, and the carrier gas being introduced into the CVI reactor from the bottom obliquely to form a cyclone starting from the bottom. The cyclone is used to remove residual air in the CVI reactor and between the porous carbon support material particles, and to allow the particles to suspend and move in the CVI reactor through the cyclone gas flow to achieve stability, and then start the carrier gas preheating.

[0063] In the implementation scheme, the introduction of the porous carbon support material is not limited to being carried out sequentially with the carrier gas, but can also be carried out simultaneously, but the simultaneous introduction will face greater requirements for condition control. For example, if the porous carbon support material is introduced from the top and the carrier gas is introduced at the same time, the porous carbon support particles are not easy to be retained in the CVI reactor in the early stage; for example, if the porous carbon support material is introduced from the bottom and the carrier gas is introduced at the same time, the porous carbon support particles are more difficult to be introduced into the CVI reactor in the middle and late stages.

[0064] Therefore, the preferred solution is that after the porous carbon support material introduction work is completed, the carrier gas is introduced into the CVI reactor from the bottom of the CVI reactor. The main reason is that the porous carbon support particles need to be blown into the CVI reactor with a large amount of carrier gas, such as introducing a fluidized carrier gas at the bottom of the reactor at the same time. In this way, on the one hand, more gas will be introduced into the reactor to form a larger updraft, blowing the porous carbon support particle powder to the surface of the gas-solid separation filter set on the top of the CVI reactor, increasing the porous carbon layer adsorbed on the surface of the gas-solid separation filter, increasing the air resistance of the filter, causing the exhaust to be blocked, and on the other hand, more gas will be introduced into the reactor, causing the exhaust to be blocked, so that the internal pressure of the reactor increases, thereby partially offsetting the pressure difference between the carrier gas introduced by the porous carbon support particles and the CVI reactor cavity, causing the efficiency of the porous carbon support particles to be reduced, or even unable to be blown in.

[0065] In an embodiment, the carrier gas is introduced into the CVI reactor from the bottom of the CVI reactor for continuous purge for 5 to 10 minutes, for example, for 5 minutes, for example, for 6 minutes, for example, for 7 minutes, for example, for 8 minutes, for example, for 9 minutes, for example, for 10 minutes.

[0066] In the implementation scheme, after the carrier gas is introduced into the CVI reactor from the bottom of the CVI reactor and continuously purged, the CVI reactor is heated and controlled until the temperature is stable, and then the reaction gas is introduced into the CVI reactor from the bottom of the CVI reactor. On the one hand, the cyclone gas formed by the carrier gas being introduced into the CVI reactor obliquely from the bottom is also kept in the introduced state, and on the other hand, the carrier gas is mixed with the silicon-containing precursor to form a reaction gas which is introduced into the CVI reactor from the center of the bottom of the CVI reactor along the axial direction.

[0067] In the implementation scheme, the purpose of mixing the carrier gas with the silicon-containing precursor to form a reaction gas and introducing it into the CVI reactor from the center of the bottom of the CVI reactor along the axial direction is to form a strong upward airflow to carry the porous carbon particles upward, so that the porous carbon support material particles in the CVI reactor can rise along the center and the axis under the action of the main airflow, increase their weight after infiltration, and fall back to the outside of the main airflow to a suspended state in equilibrium with the airflow, thereby forming a stable suspended reaction movement path.

[0068] The reaction gas enters the pores of the porous carbon support material particles, and a CVD reaction occurs on the inner surface of the pores of the porous carbon support material particles, depositing silicon on the inner surface of the pores of the porous carbon support material particles; when this rising gas and porous carbon mixed flow rises to the highest position of the fluidized body, it no longer rises, and is pushed by the continuously rising mixed flow below, moving from the center of the reactor toward the reactor wall, leaving the lifting range of the central rising airflow, and thus sinking down along the inner wall of the reactor to the bottom of the reactor, re-entering the lifting range of the rising airflow, and moving upward again, forming a temperature convection circulation path.

[0069] In the implementation scheme, the carrier gas is mixed with the silicon-containing precursor to form a reaction gas, which is introduced into the CVI reactor from the center of the bottom of the CVI reactor along the axial direction, and the gas is blown from bottom to top. The porous carbon support material particles are still easily blocked, and the gas is not easy to be evenly distributed to the surface of each particle. The carrier gas is introduced into the CVI reactor from the bottom to form a cyclone, which helps to break up and disrupt the porous carbon support material particles, and at the same time evenly distributes the gas to the surface of each particle to maintain smooth and stable airway; the cyclone forms an auxiliary airflow to prevent the porous carbon support material particles from depositing and adsorbing on the bottom or side wall, so that the porous carbon support material particles are suspended, and at the same time, a gas barrier is formed near the inner wall of the CVI reactor to prevent the porous carbon support material particles from contacting the inner wall of the CVI reactor to cause adsorption and affect the penetration effect.

[0070] In embodiments, the carrier gas is a single gas or a mixed gas that does not participate in the reaction. In some embodiments, the carrier gas is nitrogen and / or other inert gases, such as helium, such as neon, such as argon, such as krypton, such as xenon, such as nitrogen and argon, such as a mixture of nitrogen, neon, argon, helium, krypton, and xenon, such as a mixture of helium and neon, such as a mixture of neon, argon, and helium, such as a mixture of helium, neon, argon, and xenon. In some embodiments, the carrier gas is hydrogen. In some embodiments, the carrier gas is a mixture of an inert gas and hydrogen, such as a mixture of helium and hydrogen, such as a mixture of hydrogen, helium, and neon, such as a mixture of hydrogen, neon, argon, and helium.

[0071] In an embodiment, the initial flow rate of the carrier gas introduced into the CVI reactor to form a cyclone gas is 120 to 160 SLM. In some embodiments, the initial flow rate of the cyclone gas is 120 to 130 SLM, for example 120 SLM, for example 125 SLM, for example 130 SLM. In some embodiments, the initial flow rate of the cyclone gas is 130 to 150 SLM, for example 130 SLM, for example 140 SLM, for example 150 SLM. In some embodiments, the initial flow rate of the cyclone gas is 150 to 160 SLM, for example 150 SLM, for example 155 SLM, for example 160 SLM. In some embodiments, the initial flow rate of the cyclone gas is preferably 140 to 160 SLM.

[0072] In the implementation scheme, while starting the preheating of the carrier gas, the heating of the reaction zone in the CVI reactor will also be started. To achieve the purpose of the invention, the present application provides a heating zone in the axial direction of the CVI reactor based on the upright CVI reactor. The number of heating zones can be one, two or more.

[0073] In some embodiments, a heating zone is set in the axial direction of the CVI reactor based on the vertical CVI reactor. The heating zone should at least surround the core reaction part of the CVI reactor. The heating zone is controlled by the same or different temperature monitoring thermocouples. These temperature monitoring thermocouples need to set predetermined temperature targets.

[0074] In some embodiments, two connected heating zones are arranged in the axial direction of the CVI reactor based on the vertical CVI reactor, including a lower heating zone and an upper heating zone. The lower heating zone and the upper heating zone are respectively controlled by different temperature monitoring thermocouples, and they need to set predetermined temperature targets respectively.

[0075] In some embodiments, the temperature for starting the preheating of the carrier gas is set to 300° C. to 450° C., for example 300° C., for example 320° C., for example 340° C., for example 360° C., for example 380° C., for example 400° C., for example 420° C., for example 440° C., for example 450° C. In some embodiments, the temperature for starting the preheating of the carrier gas is set to 300° C. to 350° C., for example 300° C., for example 305° C., for example 310° C., for example 315° C., for example 325° C., for example 330° C., for example 350° C. In some embodiments, the temperature for starting the preheating of the carrier gas is set to 350° C. to 400° C., for example 350° C., for example 355° C., for example 370° C., for example 375° C., for example 390° C., for example 395° C., for example 400° C. In some embodiments, the temperature for starting carrier gas preheating is set to 400°C to 450°C, for example 400°C, for example 405°C, for example 410°C, for example 415°C, for example 430°C, for example 435°C, for example 450°C.

[0076] In the embodiment of setting two connected heating zones, the lower heating zone will be provided with multiple groups of independently heated heating resistance wires, and each group of heating resistance wires is controlled by a corresponding temperature monitoring thermocouple, and each group of heating resistance wires needs to set a predetermined temperature target. In some embodiments, the number of heating resistance wires is three groups, and the temperatures of the three groups of heating resistance wires increase from bottom to top.

[0077] The predetermined temperature target of the temperature monitoring thermocouple at the bottom of the three groups of heating resistance wires is set between 400°C and 510°C, for example, 400°C, for example, 410°C, for example, 420°C, for example, 430°C, for example, 440°C, for example, 450°C, for example, 460°C, for example, 470°C, for example, 480°C, for example, 490°C, for example, 510°C; the predetermined temperature target of the temperature monitoring thermocouple at the second bottom of the three groups of heating resistance wires is set between 480°C and 550°C, for example, 480°C, for example, 490°C, For example, 500°C, for example, 510°C, for example, 520°C, for example, 530°C, for example, 540°C, for example, 550°C; the predetermined temperature target of the temperature monitoring thermocouple at the top of the three groups of heating resistance wires is set between 500°C and 610°C, for example, 500°C, for example, 510°C, for example, 520°C, for example, 530°C, for example, 540°C, for example, 550°C, for example, 560°C, for example, 570°C, for example, 580°C, for example, 590°C, for example, 600°C, for example, 610°C.

[0078] In the implementation scheme, a plurality of groups of heating resistance wires are arranged in the upper heating zone, and each group of heating resistance wires is uniformly controlled by a temperature monitoring thermocouple. The plurality of groups of heating resistance wires can be arranged in parallel or in series. In some implementation schemes, the number of heating resistance wires is three, and the predetermined temperature target of the temperature monitoring thermocouples of the three groups of heating resistance wires is set between 500°C and 610°C, for example, 500°C, for example, 510°C, for example, 520°C, for example, 530°C, for example, 540°C, for example, 550°C, for example, 560°C, for example, 570°C, for example, 580°C, for example, 590°C, for example, 600°C, for example, 610°C; in some implementation schemes, the number of heating resistance wires is four, and the predetermined temperature target of the temperature monitoring thermocouples of the four groups of heating resistance wires is set between 500°C and 610°C, for example, 500°C, for example, 510°C, for example, 520℃, for example 530℃, for example 540℃, for example 550℃, for example 560℃, for example 570℃, for example 580℃, for example 590℃, for example 600℃, for example 610℃; in some embodiments, the number of heating resistance wires is five groups, and the predetermined temperature target of the temperature monitoring thermocouple of the five groups of heating resistance wires is set between 500℃ and 610℃, for example 500℃, for example 510℃, for example 520℃, for example 530℃, for example 540℃, for example 550℃, for example 560℃, for example 570℃, for example 580℃, for example 590℃, for example 600℃, for example 610℃.

[0079] In the implementation scheme, three temperature-monitoring thermocouple sensors are arranged from bottom to top along the central axis of the CVI reactor. The three temperature-monitoring thermocouple sensors provide temperature measurement and feedback of the real-time in-situ temperature distribution of the material in the CVI reactor bin. The thermocouple sensor at the bottom corresponds to the heating zone at the bottom in the horizontal direction, the thermocouple sensor at the second bottom corresponds to the junction of the heating zone at the bottom and the heating zone at the top in the horizontal direction, and the thermocouple sensor at the top corresponds to the heating zone at the top in the horizontal direction. When the temperature data readings of the internal central axis of the CVI reactor are all stabilized and are within the predetermined temperature range and gradient, the reaction gas is introduced into the CVI reactor from the bottom of the CVI reactor.

[0080] In the implementation scheme, before introducing the reaction gas into the CVI reactor, the lower temperature of the CVI reactor is obtained by the lowest thermocouple sensor, and the reaction gas is introduced into the CVI reactor when the monitored temperature is stabilized within a range.

[0081] In the embodiment, when the temperature data readings of the internal center axis of the CVI reactor are all stabilized and are in a predetermined temperature range and gradient, a reaction gas is introduced into the CVI reactor from the bottom of the CVI reactor, and the reaction gas is a mixture of a silicon-containing precursor and a carrier gas. In some embodiments, the silicon-containing precursor is a silane, such as a silane, such as a chlorosilane, such as a dichlorosilane, such as an epoxysilane, such as an aminosilane, such as a fluorosilane. In some embodiments, the silicon-containing precursor is a high-order silane, such as a disilane, such as a methyldisilane, such as a dimethyldisilane, such as a trimethyldisilane, such as a phenyldisilane, such as a vinyldisilane, such as an aminodisilane, such as an epoxydisilane, such as a chlorodisilane, such as a fluorodisilane. In some embodiments, the silicon-containing precursor uses a higher-order silane, such as a trisilane, such as a methyltrisilane, such as a dimethyltrisilane, such as a trimethyltrisilane, such as a phenyltrisilane, such as a vinyltrisilane, such as an aminotrisilane, such as an epoxytrisilane, such as a chlorotrisilane, such as a fluorotrisilane.

[0082] In the embodiment, the reaction gas is introduced into the CVI reactor from the bottom of the CVI reactor, and the reaction gas is a mixture of a silicon-containing precursor and a carrier gas. The silicon-containing precursor and the carrier gas are set at different starting flow rates according to design requirements. In some embodiments, the starting input flow rate of the silicon-containing precursor is between 60SLM and 95SLM, for example, 60SLM, for example, 70SLM, for example, 80SLM, for example, 95SLM. In some embodiments, the starting input flow rate of the silicon-containing precursor is between 60SLM and 80SLM, for example, 60SLM, for example, 62SLM, for example, 64SLM, for example, 66SLM, for example, 68SLM, for example, 80SLM. In some embodiments, the starting input flow rate of the silicon-containing precursor is between 70SLM and 85SLM, for example, 70SLM, for example, 75SLM, for example, 78SLM, for example, 80SLM, for example, 83SLM, for example, 85SLM. In some embodiments, the initial input flow rate of the silicon-containing precursor is between 80 SLM and 90 SLM, for example 80 SLM, for example 82 SLM, for example 84 SLM, for example 86 SLM, for example 88 SLM, for example 90 SLM.

[0083] In some embodiments, the initial flow rate of the carrier gas is between 70 SLM and 120 SLM, for example, 70 SLM, for example, 80 SLM, for example, 90 SLM, for example, 100 SLM, for example, 110 SLM, for example, 120 SLM. In some embodiments, the initial flow rate of the carrier gas is between 70 SLM and 95 SLM, for example, 70 SLM, for example, 75 SLM, for example, 85 SLM, for example, 95 SLM. In some embodiments, the initial flow rate of the carrier gas is between 95 SLM and 120 SLM, for example, 95 SLM, for example, 105 SLM, for example, 115 SLM, for example, 120 SLM. In some embodiments, the initial flow rate of the carrier gas is between 80 SLM and 110 SLM, for example, 80 SLM, for example, 88 SLM, for example, 98 SLM, for example, 108 SLM.

[0084] In the implementation scheme, the CVI reactor should be provided with a pressure sensor. The positions of the pressure sensors include the top and bottom of the CVI reactor, and any side wall position between the top and the bottom. The number of pressure sensors is not limited to one, and multiple pressure sensors at different positions can be provided. The pressure sensor is used to obtain the pressure in the CVI reactor in real time and feed it back to the control platform. As the silicon-containing precursor begins to be input into the CVI reactor for reaction, the temperature and pressure in the reaction chamber will begin to rise slowly and gradually reach a pressure balance point. In the event of an emergency situation where the pressure increases sharply, emergency discharge is required to relieve the pressure.

[0085] The reaction gas introduced into the CVI reactor from the bottom is quickly decomposed and consumed under the driving force of temperature and heat. Generally, the consumption rate of silicon-containing precursors decreases rapidly from bottom to top like a parabola. Figure 3 As shown in , the reaction at different heights in the vertical long reaction chamber is uneven, which seriously affects the control of product preparation quality. The suspended state of the granular porous carbon support in the vertical long reaction chamber changes along the height direction of the reactor as the reaction proceeds and the airflow is adjusted. In order to prevent the silicon-containing precursor from being insufficiently supplied in the CVI reactor, resulting in insufficient and uneven chemical vapor infiltration reactions between particles, an input port is added in the middle of the CVI reactor (not limited to the middle, but also can be above the middle or below the middle) to introduce the silicon-containing precursor as the second air intake, so as to supplement and increase the concentration of the silicon-containing precursor, thereby homogenizing the supply of the silicon-containing precursor gas source in the CVI reactor, as shown in FIG. Figure 4 The flow rate of the second intake air can be appropriately increased or decreased according to actual needs.

[0086] In some embodiments, the flow rate of the second air intake is between 20SLM and 50SLM, for example, 20SLM, for example, 30SLM, for example, 40SLM, for example, 50SLM. In some embodiments, the flow rate of the second air intake is between 20SLM and 30SLM, for example, 20SLM, for example, 23SLM, for example, 25SLM, for example, 28SLM, for example, 30SLM. In some embodiments, the flow rate of the second air intake is between 30SLM and 40SLM, for example, 30SLM, for example, 33SLM, for example, 35SLM, for example, 38SLM, for example, 40SLM. In some embodiments, the flow rate of the second air intake is between 40SLM and 50SLM, for example, 40SLM, for example, 43SLM, for example, 45SLM, for example, 48SLM, for example, 50SLM.

[0087] When the reaction gas of chemical vapor infiltration begins to be input into the CVI reactor through the bottom of the CVI reactor, the silicon-containing precursor in the reaction gas flows upward from the bottom of the CVI reactor along the central axis of the CVI reactor in a straight line, pushing and transmitting heat to the porous carbon support particles in the suspended semi-stacked state along the way, and exchanging and balancing the temperature with the heat conducted and radiated from the inner wall of the CVI reactor. These heats not only increase and / or continue to maintain the temperature of the reaction gas and the porous carbon support particles containing micropores, stabilize the internal temperature of the CVI reactor, but also help the silicon-containing precursor to obtain sufficient heat energy for thermal decomposition to continuously generate and supply free silicon sources until the silane precursor gas is exhausted. With the help of heat energy and airflow, these free silicon sources also quickly move to the surface of the porous carbon support and enter the micropores in the porous carbon particles to find suitable adsorption points for deposition, and then begin to deposit nano-silicon on the inner surface of the micropores and the outer surface of the porous carbon support particles to form nano-silicon particles, gradually covering the surface of the porous carbon support particles and the inner surface of the micropores. During this deposition process, the silicon-containing precursor molecules are decomposed, absorbed and consumed in large quantities from the bottom of the reactor. The porous carbon scaffold particles containing micropores will become heavier due to the continuous adsorption of silicon atoms. At the same time, the particles suspended at the bottom of the CVI reactor will grow faster than the particles at the top of the reactor. This process shows that Figure 5The rising airflow will be decelerated at the interface of the inner wall of the reaction chamber due to the interface resistance, the buoyancy will be reduced, and the particles will fall slowly. Some large particles at the bottom of the particle fluidized body may slide to the bottom of the inverted cone and be suspended at the bottom of the reactor, or fall back to the bottom of the CVI reactor because the buoyancy of the airflow exceeds the tolerance, causing blockage, thereby causing unexpected equipment failure and shutdown. Therefore, the flow rate of the cyclone formed by the carrier gas being introduced into the CVI reactor from the bottom in an oblique direction will gradually increase with the reaction time, and the flow rate of the reaction gas mixed with the silicon-containing precursor and introduced into the CVI reactor from the center of the bottom of the CVI reactor along the axial direction will also gradually increase with the reaction time to resolve this potential problem.

[0088] In the implementation scheme, the flow rate of the cyclone gas is gradually increased from an initial 120-160 SLM to 160-200 SLM, for example, the initial flow rate of the cyclone gas is 120 SLM, which is gradually increased to 160 SLM, for example, the initial flow rate of the cyclone gas is 130 SLM, which is gradually increased to 170 SLM, for example, the initial flow rate of the cyclone gas is 140 SLM, which is gradually increased to 180 SLM, for example, the initial flow rate of the cyclone gas is 150 SLM, which is gradually increased to 190 SLM, for example, the initial flow rate of the cyclone gas is 155 SLM, which is gradually increased to 195 SLM, for example, the initial flow rate of the cyclone gas is 160 SLM, which is gradually increased to 200 SLM.

[0089] In the implementation scheme, a carrier gas is mixed with a silicon-containing precursor to form a reaction gas, and the flow rate of the carrier gas introduced into the CVI reactor from the center of the bottom of the CVI reactor along the axial direction gradually increases with the reaction time. The flow rate of the carrier gas is gradually increased from an initial 100-120 SLM to 120-150 SLM. For example, the initial flow rate of the carrier gas is 100 SLM, which is gradually increased to 120 SLM. For example, the initial flow rate of the carrier gas is 100 SLM, which is gradually increased to 110 SLM. For example, the initial flow rate of the carrier gas is 105 SLM, which is gradually increased to 120 SLM. For example, the initial flow rate of the carrier gas is 105 SLM, which is gradually increased to 150 SLM.

[0090] In the implementation scheme, three temperature-monitoring thermocouple sensors are arranged along the central axis of the CVI reactor from bottom to top, and the real-time temperature inside the CVI reactor is measured and monitored throughout the entire chemical vapor infiltration reaction process from the beginning to the end. The temperature measurement points of the three temperature-monitoring thermocouple sensors are all set to the central axis position area of ​​the reactor, and the temperature difference between the implemented temperatures obtained by the three temperature-monitoring thermocouple sensors may not exceed 2°C, that is, the temperature difference in the reaction area in the CVI reactor may not exceed 2°C.

[0091] Preparation of Carbon-coated Silicon-Carbon Composite Materials by CVI

[0092] The CVI process can be as follows: after completing the chemical vapor infiltration of nanosilicon in the granular porous carbon support, the flow of the silicon-containing precursor is closed, the temperature and flow of the carrier gas in the CVI reactor are maintained to maintain the free suspension and fluidization state of the porous carbon support particles containing nanosilicon deposition in the CVI reactor, the temperature of the top heating zone is increased, and after a period of time, the temperature of the CVI reactor is stabilized through the upper, middle and lower three thermocouple sensors in the CVI reactor, and the carbon-containing precursor is started to be input from the bottom of the CVI reactor.

[0093] In an embodiment, the temperature of the uppermost heating zone is increased to 540-600°C, such as 540°C, such as 550°C, such as 560°C, such as 570°C, such as 580°C, such as 590°C, such as 600°C.

[0094] In the implementation scheme, after 30 to 90 minutes, the temperature of the CVI reactor is stabilized at 440-575° C. through the upper, middle and lower thermocouple sensors in the CVI reactor.

[0095] When the carbon-containing precursor is input from the bottom of the CVI reactor, the carbon-containing precursor is mixed with the carrier gas and transported upward along the central axis from the center of the bottom of the CVI reactor. The heat is pushed and transmitted to the porous carbon support particles in the suspended semi-stacked fluidized state along the way, and the heat is exchanged with the heat conducted and radiated from the inner wall of the CVI reactor. These heats not only increase and / or continue to maintain the temperature of the carbon-containing precursor, the carrier gas and the porous carbon support particles containing micropores, stabilize the internal temperature of the CVI reactor, but also help the carbon-containing precursor gas molecules to obtain sufficient heat energy for thermal decomposition to continuously generate and supply free carbon sources. With the help of heat energy and airflow, these carbon sources also quickly move to the surface of the porous carbon support and enter the micropores in the porous carbon particles to find suitable adsorption points for deposition, so that nanocarbon begins to be deposited on the nanosilicon surface in the micropores or the exposed carbon surface and the nanosilicon surface on the surface of the porous carbon support particles and the carbon surface of the exposed porous carbon to form nanocarbon islands or layers, and continue to grow to cover all surfaces of the above-mentioned porous carbon support particles (including the nanosilicon inside and outside the micropores and the surface of the exposed carbon). The thickness of this nano-carbon layer is determined by factors such as the flow rate of the carbon-containing precursor gas, the input time, the chemical vapor infiltration temperature environment, and the completeness of the suspension washing of the porous carbon scaffold in the particle state.

[0096] In an embodiment, the carbon-containing precursor includes one or more of acetylene, methane, propane, and ethylene, but is not limited to the above descriptions.

[0097] In the implementation scheme, the carbon-containing precursor is mixed into the carrier gas and transported straight upward along the central axis from the center of the bottom of the CVI reactor. The flow rate of the carbon-containing precursor is 15SLM to 25SLM, for example 15SLM, for example 18SLM, for example 20SLM, for example 22SLM, for example 25SLM.

[0098] In some embodiments, the carbon-containing precursor mixed into the carrier gas is acetylene; in some embodiments, the carbon-containing precursor mixed into the carrier gas is methane; in some embodiments, the carbon-containing precursor mixed into the carrier gas is propylene; in some embodiments, the carbon-containing precursor mixed into the carrier gas is propane; in some embodiments, the carbon-containing precursor mixed into the carrier gas is ethylene; in some embodiments, the carbon-containing precursor mixed into the carrier gas is benzene; in some embodiments, the carbon-containing precursor mixed into the carrier gas is methanol; in some embodiments, the carbon-containing precursor mixed into the carrier gas is ethanol.

[0099] As the carbon-containing precursor begins to be fed into the CVI reactor for reaction, the temperature and pressure in the CVI reactor will gradually and slowly rise. At this time, the real-time readings of the temperature monitoring thermocouple sensor and pressure sensor set on the CVI reactor can be fed back to the control platform, which monitors and regulates the temperature and gas flow of the carbon-containing precursor to maintain the stable reaction.

[0100] In the embodiment, after the required reaction amount is reached, the input of the carbon-containing precursor can be completely stopped to stop the carbon coating process. However, the input of the carrier gas is not stopped directly, but the heating of the carrier gas is stopped, and the carrier gas is continued to be blown into the CVI reactor to purge the unreacted residual carbon-containing precursor out of the CVI reactor.

[0101] In some embodiments, when the heating of the carrier gas is stopped, the heating of the upper and lower heating zones is also stopped; in some embodiments, when the heating of the carrier gas is stopped, a cooling program is set to gradually lower the upper and lower heating zones. The unheated carrier gas can gradually displace the heat of the wall of the CVI reactor and the suspended porous carbon support particles coated with carbon, thereby achieving the purpose of cooling and allowing the thermal reaction to be stopped and stably and rapidly cooled to room temperature under controlled environmental conditions.

[0102] Chemical Vapor Infiltration Reactor

[0103] The chemical vapor infiltration reactor provides a reaction space and reaction conditions corresponding to the chemical vapor infiltration reaction, so that the granular porous carbon support in the reaction space is blown up by the upward buoyancy generated by the gas flow rate, and forms a particle liquefaction flow and elutriation effect, which helps the silicon source or carbon source generated by the reaction precursor in the pyrolysis to freely contact the surface of the porous carbon particles and the inner surface of the micropores, and adsorb on the surface of the porous carbon particles and the inner surface of the micropores to form amorphous and / or microcrystalline nano-atomic clusters or islands. In this deposition process, it is also pushed upward by the heat flow of the reaction gas and gradually pushed to the inner wall of the reaction chamber, and then because the upward gas flow rate on the inner wall and the vicinity decreases, and the volume and weight increased by the deposited silicon, it slides down again along the inner wall of the reaction chamber and the vicinity. This cycle repeats until the total amount of precursor gas required for deposition is reached, and then the input of the reaction precursor can be stopped.

[0104] In the implementation scheme, a vertical columnar housing is required to provide a contact reaction space for the porous carbon support, the carrier gas and the reaction precursor.

[0105] In the implementation scheme, at least two input interfaces with independent control of opening and closing and flow rate should be provided at the bottom of the shell, one of which is used to input a mixture of carrier gas and reaction precursor into the shell, and the other is used to input carrier gas into the shell.

[0106] In the implementation scheme, a discharge port should also be provided at the bottom of the shell, and the opening and closing of the discharge port can be controlled as needed.

[0107] In some embodiments, an input interface for inputting a mixture of carrier gas and reaction precursor into the shell is arranged on the central axis straight line of the shell, and the mixture of carrier gas and reaction precursor is input along the central axis straight line of the shell; an input interface for inputting carrier gas into the shell is arranged on the side, and the input interface is arranged in an oblique manner, so that the input direction of the carrier gas forms an angle with the central axis straight line of the shell, so that the input carrier gas will preferentially blow toward the inner wall of the shell and be blocked to form a vortex.

[0108] In an implementation scheme, a raw material inlet, an exhaust port and a pressure sensor are arranged on the top of the shell.

[0109] In the implementation scheme, two heating zones are arranged outside the shell, and the two heating zones are respectively arranged in an upper and lower superposition in the shell axis direction, including a heating zone located at the top and a heating zone located at the bottom, and both heating zones provide the shell with a temperature environment that meets the gas phase permeation requirements. The upper heating zone has a plurality of electric heating wires connected in series or in parallel, and the plurality of electric heating wires are also arranged in a staggered manner in the shell axis direction, and the plurality of electric heating wires connected in series or in parallel are controlled by a temperature monitoring thermocouple. The lower heating zone has a plurality of independently controlled electric heating wires, and the plurality of electric heating wires are also arranged in a staggered manner in the shell axis direction, and each independently controlled electric heating wire is controlled by its corresponding temperature monitoring thermocouple.

[0110] In some embodiments, a heat insulating layer is arranged outside the electric heating wire of each heating zone.

[0111] In the embodiment, a thermocouple sensor is arranged inside the shell to obtain the temperature of the CVI reactor, and the working point of the thermocouple sensor is arranged in the axial direction of the shell. The number of thermocouple sensors should be at least three, and in actual operation, it should be ensured that the real-time temperature difference obtained by any two thermocouple sensors is within 2°C (including 2°C).

[0112] In some embodiments, the number of thermocouple sensors is set to three, one is arranged at the bottom of the shell, corresponding to the lower heating zone, one is arranged in the middle of the shell, corresponding to the junction of the two heating zones, and one is arranged at the top of the shell, corresponding to the upper heating zone. In some embodiments, the number of thermocouple sensors is set to four, in addition to the thermocouple sensors arranged at the upper, middle and lower positions of the shell, one is arranged between the upper and middle thermocouple sensors. In some embodiments, the number of thermocouple sensors is set to four, in addition to the thermocouple sensors arranged at the upper, middle and lower positions of the shell, one is arranged between the middle and lower thermocouple sensors. In some embodiments, the number of thermocouple sensors is set to five, in addition to the thermocouple sensors arranged at the upper, middle and lower positions of the shell, one is arranged between the middle and lower thermocouple sensors, and one is arranged between the upper and middle thermocouple sensors.

[0113] In the implementation scheme, an input interface is separately provided in the middle of the shell for replenishing the reaction precursor to the shell.

[0114] In the implementation scheme, the lower end of the shell is also connected to a cone, which is in the shape of a trumpet with a large top and a small bottom when the reactor is in an upright state, and is connected to a straight section of the same diameter at one end of the small opening, and the input interface is set at the lower opening of the straight section. Since the porous carbon bracket is lifted by the buoyancy of the airflow, it mainly participates in the circulation and permeation reaction in the upright shell, so there is a situation where the porous carbon bracket contacts the inner wall of the shell under the action of the airflow, and the particle size of these porous carbon brackets is micron-level. After contacting the inner wall of the shell, they will adhere to the inner wall of the shell or fall to the bottom of the shell due to insufficient buoyancy.

[0115] The purpose of setting the cone is to narrow the neck. On the one hand, a higher flow rate airflow is formed in the straight section below, and on the other hand, the porous carbon particles are allowed to fall along the wall of the cone back to the bottom center and enter the central airflow range of the reactor. The porous carbon particles are further blown up by the cyclone with the higher flow rate airflow and rejoin the upward movement state.

[0116] At the same time, in conjunction with the input interface arranged in an oblique manner at the bottom, a cyclone is formed starting from the bottom. The cyclone can have a sweeping effect on the cone and maintain the cone and the inner wall of the shell. At the same time, the cyclone will also form an air barrier outside the central airflow that fits the inner wall of the shell to prevent the porous carbon support material particles from contacting the inner wall of the CVI reactor.

[0117] In other embodiments, the input interface for inputting the carrier gas into the housing may not be arranged in an oblique manner.

[0118] In the implementation scheme, the included angle between the generatrix forming the cone and the central axis of the shell is set to 15-18°, for example, 15°, for example, 16°, for example, 17°, for example, 18°.

[0119] Example 1

[0120] See also Figure 1 The chemical vapor infiltration reactor includes a shell 100, the top of the shell 100 has a raw material inlet 101, an exhaust port 102 and a pressure sensor 103, and the bottom of the shell 100 has an input interface 104 and an input interface 2 105, wherein the input interface 104 is arranged on the central axis straight line of the shell, the input interface 2 105 is arranged on the outside of the input interface 104, and the input interface 2 105 is arranged in an oblique insertion state, the state is as follows Figure 2 As shown, an input interface 3 106 is provided in the middle of the housing 100 , and three thermocouple sensors 107 are arranged inside the housing 100 .

[0121] A heating zone 1 210 and a heating zone 2 220 are arranged outside the shell 100. The heating zone 1 210 is located at the top. Three groups of parallel electric heating wires 1 211 are arranged in the heating zone 1 210. Three independent groups of electric heating wires 2 221, electric heating wires 3 222 and electric heating wires 4 223 are arranged in the heating zone 2 220.

[0122] The shell 100 is made of high temperature resistant and corrosion resistant stainless steel material, with an inner diameter of about 43 cm and a length of 368 cm. The manufactured reactor can be loaded with 30 kg to 150 kg of granular porous carbon supports, which is much higher than the single batch processing capacity of 20 kg of the current horizontal CVI reactor in the industry.

[0123] The outside of the electric heating wire 1 211, the electric heating wire 221, the electric heating wire 3 222 and the electric heating wire 4 223 are all provided with insulation materials to form an insulation layer to ensure that heat loss is reduced, the furnace heating efficiency is increased, and the furnace temperature and the temperature inside the reaction chamber and the temperature gradient are kept stable.

[0124] The bottom thermocouple sensor 107 and the temperature monitoring thermocouple of the electric heating wire 223 can be shared to simplify the complexity of the equipment component installation.

[0125] A cone 108 is also provided at the bottom of the shell 100 , and the included angle between the generatrix of the cone 108 and the central axis of the shell 100 is set to 15° to prevent material from piling up at the bottom of the shell 100 .

[0126] Example 2

[0127] According to the temperature conditions recorded in Table 1, the reactor of Example 1 was used to prepare silicon-carbon composite materials, wherein temperature reading position ④ in Table 1 corresponds to the preset temperature of the temperature monitoring thermocouple of electric heating wire four 223, temperature reading position ⑤ corresponds to the preset temperature of the temperature monitoring thermocouple of electric heating wire three 222, temperature reading position ⑥ corresponds to the preset temperature of the temperature monitoring thermocouple of electric heating wire two 221, and temperature reading position ⑦ corresponds to the preset temperature of the temperature monitoring thermocouple of electric heating wire one 211.

[0128]

[0129] Table 1

[0130] The bulk density of the porous carbon scaffold granular material used in this example is 0.26 g / cm 3 The particle size range is 5 to 10 μm, and the bulk density of the prepared silicon-porous carbon composite particles is 0.42 g / cm 3 Because silicon infiltrates and deposits into the pores and on the surface of the porous carbon scaffold particles, their bulk density increases by about 60%.

[0131] It should be emphasized here that the horizontal reaction chamber of the prior art has difficulty in completing the penetration of porous carbon scaffolds with a particle size range of 5 to 10 μm. The lower limit particle size for the horizontal reaction chamber of the prior art to complete the penetration of porous carbon scaffolds is 25 μm. Porous carbon scaffolds smaller than 25 μm will have the problem of difficulty in fluidization. Under low gas velocity conditions, channel flow will be formed near the reactor wall, the gas will be bypassed, and the material cannot be fluidized; a slightly higher gas velocity will blow the material out of the reaction zone, making it difficult to form a good and stable fluidization state.

[0132] In fact, the existing technology is not limited to the horizontal reaction chamber, which is difficult to complete the penetration of porous carbon supports in the particle size range of 5 to 10 μm. Even the vertical reaction furnace can only continuously produce and operate the minimum particle size of about 25 microns. Smaller particle sizes cannot be continuously operated in large quantities. This is mainly restricted by the operation mode of the airflow in the reaction chamber. The smaller the particle, the more difficult it is to operate.

[0133] Figure 6 Shown are TEM images of the silicon-porous carbon composite material particles prepared in this example at different magnifications.

[0134] During the process of implementing the chemical vapor infiltration of nano-silicon into the micropores of the porous carbon support particles, the tail gas discharged from the CVI reactor after the reaction contains a considerable amount of hydrogen and carbon-containing gas. When it comes into contact with the air, there is no abnormal reaction or odor, and no dust is generated, which means that this is a very clean and complete reaction.

[0135] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them.

Claims

1. A method for preparing a silicon-carbon composite material using a chemical vapor infiltration reactor, characterized in that: A vertical reactor is provided, wherein the method comprises: Inputting a porous carbon support material into the reactor, introducing a central gas and a carrier gas, and starting a heating furnace to heat the reaction chamber so that the reactor reaches a reaction setting condition, wherein the reaction setting condition at least includes the reaction chamber being at a set temperature and maintaining a stable temperature; A silicon-containing precursor gas is introduced and mixed with the central gas to form a reaction gas which is then input into the reaction chamber through the input interface at the bottom; The reaction was maintained until completion.

2. The method for preparing a silicon-carbon composite material by a chemical vapor infiltration reactor according to claim 1, characterized in that: The reactor is in batch production state and the reactor is under reaction setting conditions.

3. The method for preparing a silicon-carbon composite material by a chemical vapor infiltration reactor according to claim 1, characterized in that: Before or after the central gas is mixed with the silicon-containing precursor to form the reaction gas and input into the reaction chamber through the input interface at the bottom, the carrier gas is introduced into the reactor from the bottom in a single oblique insertion manner to form the cyclone gas.

4. The method for preparing a silicon-carbon composite material by a chemical vapor infiltration reactor according to claim 1, characterized in that: The carrier gas is preheated before being input into the reaction chamber.

5. The method for preparing a silicon-carbon composite material by a chemical vapor infiltration reactor according to claim 3, characterized in that: In the process of maintaining the reaction, the gas flow rates of the cyclone gas and the reaction gas are gradually increased.

6. The method for preparing a silicon-carbon composite material by a chemical vapor infiltration reactor according to claim 1, characterized in that: The initial input flow rate of the silicon-containing precursor in the reaction gas is 60 SLM to 150 SLM; and / or the initial input flow rate of the carrier gas in the reaction gas is 70 SLM to 150 SLM.

7. The method for preparing a silicon-carbon composite material by a chemical vapor infiltration reactor according to claim 1, characterized in that: The preset temperatures of a plurality of heating devices for independently setting heating temperatures increase from bottom to top.

8. The method for preparing a silicon-carbon composite material by a chemical vapor infiltration reactor according to claim 7, characterized in that: The preset temperature of the plurality of heating devices that set the heating temperature synchronously is 500°C to 650°C.

9. The method for preparing a silicon-carbon composite material by a chemical vapor infiltration reactor according to claim 1, characterized in that: During the reaction, the carrier gas is mixed with the silicon-containing precursor and input into the reaction chamber from the input interface at the bottom, and the silicon-containing precursor is added into the reaction chamber at the middle of the reaction chamber or at multiple locations from the bottom to the top.

10. The method for preparing a silicon-carbon composite material by a chemical vapor infiltration reactor according to claim 9, characterized in that: During the reaction, the silicon-containing precursor is added in a quantitative or non-quantitative manner or at a decreasing flow rate according to the distance from the bottom.

11. The method for preparing a silicon-carbon composite material by a chemical vapor infiltration reactor according to claim 1, characterized in that: The central gas and the carrier gas are nitrogen and / or an inert gas and / or hydrogen.

12. The method for preparing a silicon-carbon composite material by a chemical vapor infiltration reactor according to claim 1, characterized in that: The silicon-containing precursor includes one or more of silane, higher-order silane, and chlorosilane.

13. The method for preparing a silicon-carbon composite material by a chemical vapor infiltration reactor according to claim 1, characterized in that: The granular multi-microporous porous carbon support material is replaced by a granular silicon-carbon composite material, and the silicon-containing precursor is replaced by a carbon-containing precursor to prepare a carbon-coated silicon-carbon composite material.

14. The method for preparing a silicon-carbon composite material by a chemical vapor infiltration reactor according to claim 13, characterized in that: The preset temperature of the plurality of heating devices that set the heating temperature synchronously is 500°C to 700°C.

15. The method for preparing silicon-carbon composite material by chemical vapor infiltration reactor according to claim 13, characterized in that: The carbon-containing precursor includes one or more of methane, propane, ethylene, and acetylene.

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