A method for weakly oxidizing low-temperature sintered silicon carbide honeycomb ceramic carriers

Abstract

The application discloses a method for weakly oxidizing and low-temperature sintering of a silicon carbide honeycomb ceramic carrier, which comprises the following steps: pushing a kiln car loaded with green bodies into a gas furnace; heating at a heating rate of 1-2 DEG C / min to 100 DEG C and keeping the temperature for 1.5 h; heating at a heating rate of 0.8-1.5 DEG C / min to 150 DEG C; heating at a heating rate of 0.4-1.0 DEG C / min to 450 DEG C; heating at a heating rate of 1-2 DEG C / min to 650 DEG C and keeping the temperature for 2 h; heating at a heating rate of 1-2 DEG C / min to 1200 DEG C and gradually reducing the oxygen content in the furnace during sintering; keeping the temperature for 4 h after the temperature reaches 1200 DEG C; stopping heating and naturally cooling the furnace to 800 DEG C; opening the combustion-supporting fan and the smoke exhaust fan; and continuously cooling to 150 DEG C and then discharging the furnace. The method realizes the integrated sintering of debinding and sintering, and the sintered silicon carbide honeycomb ceramic carrier has the characteristics of low thermal expansion coefficient and narrow pore size.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of honeycomb ceramics, in particular to a method for weak-oxidation low-temperature sintering of a silicon carbide honeycomb ceramic carrier. BACKGROUND

[0002] With the rapid development of the automobile industry, automobiles have become the main source of air pollution. According to the China Mobile Source Environmental Management Annual Report (2021), the particulate matter (PM) emissions of diesel vehicles on Chinese roads reached 58,000 tons, accounting for more than 90% of the total vehicle emissions, of which heavy-duty diesel vehicles accounted for the majority. The diesel particulate filter (DPF) is an internationally recognized effective diesel vehicle exhaust treatment technology and one of the most practical diesel engine exhaust particulate treatment technologies in the world.

[0003] Currently, there are mainly two types of particulate traps: cordierite and silicon carbide DPFs. Silicon carbide materials have rapidly developed as a new type of diesel vehicle exhaust particulate filter material due to their excellent heat resistance, corrosion resistance, low thermal expansion coefficient, and high thermal conductivity. Compared to cordierite DPFs, silicon carbide DPFs have better high-temperature resistance, mechanical strength, and thermal conductivity, as well as greater maximum carbon loading and ash holding capacity, making them suitable for use in small and medium-sized diesel engines with relatively low exhaust temperatures.

[0004] Currently, the synthesis of silicon carbide DPF carriers mainly uses the Re-SiC and Si-SiC methods, which have been widely used in diesel vehicle aftertreatment systems. However, both methods have the characteristic of high sintering temperature and require inert gas protection during sintering. Due to their complex production process, high sintering temperature, and complex control, they require very strict production equipment and consume a lot of energy, resulting in high product prices and limiting the use of carriers. SUMMARY

[0005] To address the technical difficulties of high sintering temperature, the need for atmosphere protection during sintering, the separation of degreasing and sintering, the complexity of the sintering process, and the high requirements for sintering furnaces, the present application provides a method for weak-oxidation low-temperature sintering of a silicon carbide honeycomb ceramic carrier. This method uses a traditional gas furnace to achieve the integration of degreasing and sintering of the silicon carbide honeycomb ceramic carrier, and the sintered silicon carbide honeycomb ceramic carrier has low thermal expansion coefficient and narrow pore size.

[0006] To achieve the above technical purposes and effects, the present application realizes the following technical solutions:

[0007] A method for weak-oxidation low-temperature sintering of a silicon carbide honeycomb ceramic carrier, comprising the following steps:

[0008] 1) The green honeycomb ceramic silicon carbide is regularly placed on the sintered boron plate, and after loading, the kiln car is pushed into the gas furnace;

[0009] 2) The temperature is raised to 100℃ at a rate of 1-2℃ / min, and the temperature is kept at 100℃ for 1.5h to remove the water in the green honeycomb ceramic silicon carbide;

[0010] 3) The temperature is raised to 150℃ at a rate of 0.8-1.5℃ / min, and the temperature is reduced to prevent the green body from exploding;

[0011] 4) The temperature is raised to 450℃ at a rate of 0.4-1.0℃ / min to remove the organic matter in the green honeycomb ceramic silicon carbide;

[0012] 5) The temperature is raised to 650℃ at a rate of 1-2℃ / min, and the temperature is kept for 2h to remove the activated carbon in the green honeycomb ceramic silicon carbide;

[0013] 6) The temperature is raised to 1200℃ at a rate of 1-2℃ / min, and this stage is the sintering stage, and the oxygen content in the furnace is gradually reduced during the sintering process;

[0014] 7) After the temperature reaches 1200℃, the temperature is kept for 4h to make the sintering process uniform, and the atmosphere in the furnace is controlled to be weakly oxidizing;

[0015] 8) Stop heating, naturally cool to 800℃, then turn on the combustion air fan and the exhaust fan to speed up the cooling in the furnace, and continue to cool to 150℃ to get out of the furnace, and get the honeycomb ceramic silicon carbide carrier.

[0016] Further, in step 1), the green honeycomb ceramic silicon carbide is placed in a two-branch stacked manner, the bottom of the green body is placed on the sintered boron plate, the green bodies are separated by porous clamps, the upper surface of the green body is sealed by a porous cover plate, and the two ends of the green body are sealed by a porous plug; The porous clamp, the porous cover plate and the porous plug are used for protection sintering, and the green honeycomb ceramic silicon carbide is not directly contacted with the open flame during sintering.

[0017] 150℃-450℃ is the debinding stage, in order to further prevent the explosion of organic matter during the debinding process from causing the green body to crack, the temperature rising rate is further controlled to be 0.4-0.8℃ / min.

[0018] In the debinding stage, the kiln pressure in the furnace is in a micro-negative pressure state to ensure that the smoke gas can be effectively removed, reduce the smoke concentration in the furnace, and reduce the risk of explosion in the furnace.

[0019] 650-1200℃ is the sintering stage, and the oxygen content in the furnace needs to be gradually reduced; the oxygen content in the furnace is controlled between 8-14% at 650-850℃, the oxygen content in the furnace is controlled between 4-8% at 850-1050℃, and the oxygen content in the furnace is controlled between 2-4% at 1050-1200℃; after the temperature reaches 1200℃, the oxygen content in the furnace is continuously maintained at 2-4%, and the temperature is kept for 4h, so as to achieve the effect of uniformization of the sintering process.

[0020] The beneficial effects of the present application are:

[0021] The sintering method of the silicon carbide honeycomb ceramic carrier provided by the present application has the advantages of low sintering temperature, low cost, simple process, etc., greatly reduces the requirements for sintering equipment, greatly saves energy, reduces consumption, and is beneficial to environmental protection.

[0022] The sintering method of the silicon carbide honeycomb ceramic carrier provided by the present application can realize the sintering of the silicon carbide honeycomb ceramic using a traditional natural gas furnace, breaking the technical barrier of using an electric furnace for atmosphere protection sintering of the silicon carbide honeycomb ceramic for a long time, and realizing continuous production of the silicon carbide honeycomb ceramic debinding and sintering using a gas furnace, and the sintering time can be controlled within 25h, the sintering time is short, the sintering cost of the silicon carbide honeycomb ceramic can be effectively reduced, and the present application has important significance for the silicon carbide honeycomb ceramic industry.

[0023] The sintered silicon carbide honeycomb ceramic carrier has the characteristics of low thermal expansion coefficient and narrow pore size, so that the trapping effect and regeneration effect of the silicon carbide particle trap can reach an ideal state in the use process, and has great economic benefits and application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The figure is a sintering curve of the embodiment of the present application;

[0025] Figure 2 The figure is a thermal expansion coefficient graph of the silicon carbide honeycomb ceramic carrier sintered by the method of the present application;

[0026] Figure 3 The figure is a narrow pore size distribution graph of the silicon carbide honeycomb ceramic carrier sintered by the method of the present application. DETAILED DESCRIPTION

[0027] The technical solutions in the present application will be described clearly and completely in combination with specific embodiments, obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0028] The application provides a method for weakly oxidizing and low-temperature sintering of a silicon carbide honeycomb ceramic carrier, comprising the following steps:

[0029] 1) Regularly placing the silicon carbide honeycomb ceramic green body on a sintered boron plate, and pushing the kiln car into the gas furnace after loading is completed;

[0030] In the step 1), the silicon carbide honeycomb ceramic green body is placed in a two-branch stacked manner, the green body is placed flat on the sintered boron plate, the green bodies are separated by porous clamps, the upper surface of the green body is sealed by a porous cover plate, and the two ends of the green body are sealed by porous plugs, so that the silicon carbide honeycomb ceramic green body is not directly contacted with the open flame during the sintering process;

[0031] 2) The temperature is raised to 100 DEG C at a temperature raising rate of 1-2 DEG C / min, and the temperature is kept at 100 DEG C for 1.5 h to remove the water in the silicon carbide green body;

[0032] 3) The temperature is raised to 150 DEG C at a temperature raising rate of 0.8-1.5 DEG C / min to reduce the temperature raising rate, so as to smoothly enter the defatting stage and prevent the green body from exploding;

[0033] 4) The temperature is raised to 450 DEG C at a temperature raising rate of 0.4-1.0 DEG C / min to remove the organic matter in the silicon carbide honeycomb ceramic green body; 150 DEG C-450 DEG C is the defatting stage, and the temperature raising rate is preferably controlled to be 0.4-0.8 DEG C / min, so as to further prevent the organic matter from exploding during the defatting process and causing the green body to crack; in the defatting stage, the kiln pressure in the furnace needs to be controlled to be a micro-negative pressure state, so as to ensure that the smoke during defatting can be effectively removed, reduce the smoke concentration in the furnace and reduce the risk of explosion in the furnace;

[0034] 5) The temperature is raised to 650 DEG C at a temperature raising rate of 1-2 DEG C / min, and the temperature is kept for 2 h to remove the activated carbon in the silicon carbide honeycomb ceramic green body;

[0035] 6) The temperature is raised to 1200 DEG C at a temperature raising rate of 1-2 DEG C / min, and this stage is the sintering stage, and the oxygen content in the furnace is gradually reduced during the sintering process;

[0036] 7) After the temperature reaches 1200 DEG C, the temperature is kept for 4 h to homogenize the sintering process, and the atmosphere in the furnace is controlled to be weakly oxidizing;

[0037] 650 DEG C-1200 DEG C is the sintering stage, and the oxygen content in the furnace needs to be gradually reduced; in the stage of 650 DEG C-850 DEG C, the oxygen content in the furnace is controlled to be 8-14%; in the stage of 850 DEG C-1050 DEG C, the oxygen content in the furnace is controlled to be 4-8%; in the stage of 1050 DEG C-1200 DEG C, the oxygen content in the furnace is controlled to be 2-4%; after the temperature reaches 1200 DEG C, the oxygen content in the furnace is continuously kept to be 2-4%;

[0038] 8) Stop heating and allow the furnace to cool naturally to 800°C. Then turn on the combustion fan and exhaust fan to accelerate the cooling inside the furnace. Continue cooling to 150°C to obtain the silicon carbide honeycomb ceramic carrier.

[0039] Related experiments were conducted on the silicon carbide porous honeycomb ceramic carrier obtained by sintering using the method provided in this invention. The experimental results show that:

[0040] (1) The silicon carbide honeycomb ceramic carrier sintered using the method of this invention was tested using a thermal expansion meter, and its coefficient of thermal expansion from 30℃ to 800℃ was 4.107 × 10⁻⁶. -6 ℃ -1 ,like Figure 2 As shown.

[0041] (2) The silicon carbide honeycomb ceramic carrier sintered using the method of this invention was tested for pore size distribution using a mercury porosimeter. The micropores were concentrated and exhibited a narrow pore size distribution, with pore size D10 of 4–7 μm, D50 of 10–13 μm, and D90 of 20–25 μm. Figure 3 As shown.

[0042] Example

[0043] First, according to the requirements, the silicon carbide honeycomb ceramic green bodies are placed regularly on the sintering boron plate. The silicon carbide honeycomb ceramic green bodies are placed in pairs, with the bottom of the green body flat on the sintering boron plate. The green bodies are separated from each other by porous clips. The upper surface of the green body is sealed with a porous cover plate, and the two ends of the green body are sealed with porous plugs. In short, porous clips, porous cover plates, and porous plugs are used to protect the sintering process. The silicon carbide honeycomb ceramic green bodies do not come into direct contact with open flame during the sintering process. After loading, the loaded kiln car is pushed into the gas furnace.

[0044] Check and turn on the combustion fan and exhaust fan of the gas furnace (kiln), and ignite for sintering.

[0045] according to Figure 1 The sintering curve diagram shows that the temperature was increased to 100℃ at a heating rate of 1.75℃ / min and held at 100℃ for 1.5h to remove moisture from the silicon carbide green blank, thereby reducing the impact of moisture on the degreasing stage.

[0046] Then, increase the temperature to 150℃ at a rate of 1℃ / min. The main purpose of this step is to reduce the heating rate so that the temperature can enter the degreasing stage evenly and stably, in order to prevent the billet from being ignited due to the heating rate being too fast, which would cause the temperature to run out of control during the degreasing process and the billet to crack.

[0047] The temperature is raised to 450°C at a rate of 0.625°C / min, and the organic substances in the silicon carbide honeycomb ceramic, such as low-temperature adhesive, pore-forming agent, pressure aid, etc., are fully oxidized and removed. The temperature rising rate and the uniformity of the temperature in the furnace need to be strictly controlled. If the temperature rising rate is too fast, the organic substances in the honeycomb ceramic body will be locally ignited, the local temperature in the furnace will be too high, the body will explode, and the carrier will be cracked by thermal shock.

[0048] After the debinding is completed, the temperature is raised to 650°C at a rate of 1.11°C / min. At this stage, the organic substances in the silicon carbide honeycomb ceramic carrier have been debound, and the body is supported by the accumulation effect of the particles. The temperature rising rate should not be too fast, otherwise the body will collapse due to the large temperature difference between the inside and outside of the body. After the temperature is raised to 650°C, the temperature is kept for 2 hours to fully remove the activated carbon in the body.

[0049] The temperature is then quickly raised to 1200°C at a rate of 1.83°C / min. This stage is the sintering stage, and the sintering phase in the silicon carbide honeycomb ceramic carrier formula begins to sinter, and the body gradually begins to appear strength. However, in order to reduce the oxidation of silicon carbide during the sintering process, the oxygen content in the furnace needs to be gradually reduced. The oxygen content in the furnace is controlled between 8-14% at 650-850°C, between 4-8% at 850-1050°C, and between 2-4% at 1050-1200°C.

[0050] When the temperature reaches 1200°C, the oxygen content in the furnace is continuously maintained at 2-4%, and the temperature is kept for 4 hours to allow the sintering phase to fully diffuse between the silicon carbide particles, thereby achieving the effect of uniformization of the sintering process.

[0051] After the 1200°C temperature holding is completed, the furnace is directly stopped, and the furnace is naturally cooled to 800°C. Then the combustion air fan and the exhaust fan are turned on, and the temperature is further reduced to 150°C, and the silicon carbide honeycomb ceramic carrier is obtained.

[0052] Comparative Example 1

[0053] The silicon carbide honeycomb ceramic green body is placed on the sintered boron plate in a regular manner. The silicon carbide honeycomb ceramic green body is placed in a two-branch stacked manner. The bottom of the body is placed on the sintered boron plate, and the bodies are separated by porous clamps. The upper surface of the body is sealed with a porous cover plate, and the two ends of the body are sealed with a porous plug. In summary, the porous clamp, porous cover plate, and porous plug are used to protect the sintering. The silicon carbide honeycomb ceramic green body does not directly contact the open flame during the sintering process. After loading, the loaded kiln car is pushed into the gas furnace.

[0054] Check and turn on the furnace combustion air fan, exhaust fan, and ignition for sintering.

[0055] Ramp up to 100℃ at 1.75℃ / min, keep 100℃ for 1.5h, remove the water in the green body of silicon carbide, to reduce the impact of water on the defatting stage.

[0056] Ramp up to 150℃ at 1℃ / min, this section is mainly to reduce the heating rate, while the temperature is uniform and stable into the defatting stage, to prevent the heating rate too fast, the green body was ignited, resulting in defatting process temperature out of control, the green body cracking;

[0057] Ramp up to 450℃ at 1.1℃ / min, to remove the organic matter in the green body.

[0058] After defatting, ramp up to 650℃ at 1.11℃ / min, to remove the activated carbon in the green body.

[0059] Ramp up to 1200℃ at 1.83℃ / min, this section is the sintering stage, the sintering phase in the formula begins to sinter, the green body gradually begins to appear strength, but in order to reduce the oxidation of silicon carbide during sintering, the oxygen content in the furnace needs to be gradually reduced, among them, 650℃-850℃ stage, the oxygen content in the furnace is controlled between 8-14%, 850℃-1050℃ stage, the oxygen content in the furnace is controlled between 4-8%, 1050℃-1200℃ stage, the oxygen content in the furnace is controlled between 2-4%.

[0060] When the temperature reaches 1200℃, continue to maintain the oxygen content in the furnace at 2-4%, while keeping for 4h, so that the sintering phase fully diffuses between the silicon carbide particles, to achieve the effect of sintering process homogenization.

[0061] After 1200℃ keeping, stop the fire directly, and naturally cool to 800℃ with the furnace, then open the combustion air fan and exhaust fan, continue to cool to 150℃, and then take out the furnace, to get the silicon carbide honeycomb ceramic carrier.

[0062] Comparative Example 2

[0063] First, according to the requirements, the green body of silicon carbide honeycomb ceramic is regularly placed on the sintered boron plate, the green body of silicon carbide honeycomb ceramic is placed in a two-branch stacked manner, the bottom of the green body is placed flat on the sintered boron plate, the green body is separated by porous clamps, the upper surface of the green body is sealed by a porous cover plate, and the two ends of the green body are sealed by a porous plug. In short, the porous clamp, the porous cover plate and the porous plug are used to protect sintering. The green body of silicon carbide honeycomb ceramic does not directly contact with open flame during sintering. After loading, the loaded kiln car is pushed into the gas furnace.

[0064] Check and open the combustion air fan and exhaust fan of the kiln, and ignite for sintering.

[0065] Ramp up to 100°C at 1.75°C / min, keep 100°C for 1.5h, remove the water in the green body of silicon carbide, to reduce the impact of water on the debinding stage.

[0066] Ramp up to 150°C at 1°C / min, this section is mainly to reduce the heating rate, while the temperature uniform, smooth into the debinding stage, to prevent the heating rate too fast, the green body was ignited, resulting in debinding process temperature out of control, the green body cracking;

[0067] Ramp up to 450°C at 0.625°C / min, the organic matter in the silicon carbide honeycomb ceramic, such as low temperature binder, pore forming agent, pressure agent, etc. are fully oxidized and removed. The temperature rate and the uniformity of the furnace temperature need to be strictly controlled in this stage. If the temperature rate is too fast, the organic matter in the honeycomb ceramic green body will be locally ignited, resulting in a local high temperature in the furnace, and the green body will explode, causing the carrier to crack due to thermal shock.

[0068] After debinding, ramp up to 650°C at 1.11°C / min. In this stage, the internal organic matter of the silicon carbide honeycomb ceramic carrier has been debound, and the green body is supported by the accumulation effect of the particles. The temperature rate should not be too fast, otherwise the green body will collapse due to the large temperature difference between the inside and outside of the green body. The temperature is kept at 650°C for 2h to fully remove the activated carbon inside the green body.

[0069] Ramp up to 1200°C at 1.83°C / min. This section is the sintering stage, and the oxygen content in the furnace is not controlled during the sintering process.

[0070] When the temperature reaches 1200°C, keep it for 4h to make the sintering phase fully diffuse between the silicon carbide particles, achieving the effect of uniformization in the sintering process.

[0071] After 1200°C, stop the fire directly, and naturally cool to 800°C with the furnace. Then turn on the combustion air fan and the exhaust fan, and continue to cool to 150°C to get out of the furnace, obtaining the silicon carbide honeycomb ceramic carrier.

[0072] Comparative Example 3

[0073] The silicon carbide honeycomb ceramic green body is placed regularly on the sintering boron plate according to the requirements. The silicon carbide honeycomb ceramic green body is placed in a two-branch stacked manner. The bottom of the green body is placed flat on the sintering boron plate. The green body is separated by porous clamps. The upper surface of the green body is sealed with a porous cover plate. The two ends of the green body are sealed with a porous plug. In short, the porous clamp, porous cover plate, and porous plug are used to protect the sintering. The silicon carbide honeycomb ceramic green body does not directly contact the open flame during sintering. After loading, the loaded kiln car is pushed into the gas furnace.

[0074] Check and start the kiln combustion air fan, exhaust fan, ignition sintering.

[0075] Rise to 100℃ at a rate of 1.75℃ / min, keep 100℃ for 1.5h, remove the moisture in the green body of silicon carbide to reduce the impact of moisture on the debinding stage.

[0076] Rise to 150℃ at a rate of 1℃ / min, this section is mainly to reduce the rate of temperature rise, while making the temperature uniform and stable into the debinding stage, to prevent the temperature rate too fast, the green body is ignited, resulting in debinding process temperature out of control, the green body cracking;

[0077] Rise to 450℃ at a rate of 0.625℃ / min, the organic matter in the silicon carbide honeycomb ceramic, such as low temperature binder, pore forming agent, pressure agent, etc. is fully oxidized and removed, this stage needs to strictly control the rate of temperature rise and the uniformity of the temperature in the furnace, the rate of temperature rise is too fast, which will cause the organic matter in the honeycomb ceramic green body to be locally ignited, resulting in the local temperature in the furnace being too high, the green body exploding, and the carrier cracking due to thermal shock.

[0078] After debinding, rise to 650℃ at a rate of 1.11℃ / min, at this stage, the organic matter in the silicon carbide honeycomb ceramic carrier has been debound, the green body is supported by the accumulation effect of the particles itself, the rate of temperature rise should not be too fast, otherwise the temperature difference between the inside and outside of the green body will be too large, resulting in collapse, rise to 650℃ and keep for 2h to fully remove the activated carbon in the green body.

[0079] Rise to 1100℃ at a rate of 1.83℃ / min, this section is the sintering stage, the sintering phase in the formula starts to sinter, and the green body gradually begins to appear strength, but in order to reduce the oxidation of silicon carbide during the sintering process, the oxygen content in the furnace needs to be gradually reduced, among which the oxygen content in the furnace is controlled between 8-14% at 650℃-850℃ stage, between 4-8% at 850℃-1050℃ stage, and between 2-4% at 1050℃-1100℃ stage.

[0080] When the temperature reaches 1100℃, the oxygen content in the furnace is continuously maintained at 2-4%, and the temperature is kept for 4h, so that the sintering phase can fully diffuse between the silicon carbide particles, to achieve the effect of uniformization in the sintering process.

[0081] After keeping 1100℃, the furnace is directly stopped, and the carrier is naturally cooled to 800℃ with the furnace, then the combustion air fan and the exhaust fan are opened, and the temperature is continuously reduced to 150℃, and the silicon carbide honeycomb ceramic carrier can be taken out of the furnace.

[0082] The sintering yield and key physical performance parameters of the silicon carbide honeycomb ceramic carriers of the examples and comparative examples are shown in Table 1.

[0083] Table 1

[0084]

[0085]

[0086] By combining the embodiments and comparative examples, we can obtain:

[0087] (1) As can be seen from the comprehensive examples and Comparative Example 1, the heating rate during the degreasing stage of 150℃~450℃ has a decisive effect on the sintering pass rate. If the heating rate during the degreasing stage is too high, the green body is prone to cracking and the yield is low.

[0088] (2) As can be seen from the comprehensive examples and Comparative Example 2, during the high-temperature sintering stage of 650℃~1200℃, it is necessary to gradually control the oxygen content in the furnace. If the oxygen content in the furnace is too high, especially during the 1050℃~1200℃ and 1200℃ heat preservation process, silicon carbide is easily oxidized to form silicon oxide under high temperature conditions for a long time. Too much silicon oxide phase will result in a high coefficient of thermal expansion, which will reduce the thermal shock resistance of the carrier.

[0089] (3) Combining Example 1 and Comparative Example 3, after the sintering temperature was reduced from 1200℃ to 1100℃, the mechanical strength of the sintered carrier decreased significantly, while the water absorption rate increased. The mechanical strength of the carrier could not meet the requirements for use. At the same time, due to the decrease in mechanical strength, the thermal shock resistance of the carrier also decreased significantly.

[0090] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0091] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for low-temperature sintering of weakly oxidized silicon carbide honeycomb ceramic carriers, characterized in that, Includes the following steps: 1) Push the kiln car loaded with silicon carbide honeycomb ceramic green bodies into the gas furnace; 2) Heat to 100℃ at a heating rate of 1~2℃ / min, and hold at 100℃ for 1.5h to remove moisture from the silicon carbide green blank; 3) Increase the temperature to 150℃ at a rate of 0.8~1.5℃ / min, then reduce the heating rate to smoothly enter the degreasing stage and prevent deflagration of the billet. 4) Heat to 450℃ at a heating rate of 0.4~1.0℃ / min to remove organic matter from the silicon carbide honeycomb ceramic green body; 5) Heat to 650℃ at a heating rate of 1~2℃ / min, hold for 2h to remove activated carbon from silicon carbide honeycomb ceramic green body; 6) Heat to 1200℃ at a heating rate of 1~2℃ / min. This stage is the sintering stage. During the sintering process, the oxygen content in the furnace is gradually reduced. 7) After the temperature reaches 1200℃, keep it at that temperature for 4 hours to homogenize the sintering process; 8) Stop heating and allow the furnace to cool naturally to 800°C. Then turn on the combustion fan and exhaust fan to accelerate the cooling inside the furnace. Continue cooling to 150°C to remove the furnace and obtain the silicon carbide honeycomb ceramic carrier. The sintering stage is from 650℃ to 1200℃, during which the oxygen content in the furnace needs to be gradually reduced. Specifically, from 650℃ to 850℃, the oxygen content in the furnace is controlled between 8% and 14%; from 850℃ to 1050℃, the oxygen content is controlled between 4% and 8%; from 1050℃ to 1200℃, the oxygen content is controlled between 2% and 4%; after the temperature reaches 1200℃, the oxygen content in the furnace is maintained at 2% to 4% to control the atmosphere in the furnace to a weakly oxidizing state.

2. The method for weakly oxidizing low-temperature sintering silicon carbide honeycomb ceramic carrier according to claim 1, characterized in that, In step 1), the silicon carbide honeycomb ceramic green bodies are arranged in a regular manner on the sintering boron plate. Specifically, the silicon carbide honeycomb ceramic green bodies are arranged in two stacked positions, with the bottom of the green body placed flat on the sintering boron plate. The green bodies are separated from each other by a porous clip, and the upper surface of the green body is sealed with a porous cover plate. The two ends of the green body are sealed with porous plugs to prevent the silicon carbide honeycomb ceramic green bodies from coming into direct contact with open flame during the sintering process.

3. The method for weakly oxidizing low-temperature sintering silicon carbide honeycomb ceramic carrier according to claim 1, characterized in that, The degreasing stage is from 150℃ to 450℃. To prevent the organic matter from exploding and causing the green body to crack during the degreasing process, the heating rate is controlled between 0.4℃ and 0.8℃ / min.

4. The method for weakly oxidizing low-temperature sintering silicon carbide honeycomb ceramic carrier according to claim 3, characterized in that, During the degreasing stage, the kiln pressure inside the furnace is under a slight negative pressure to ensure that the degreased flue gas can be effectively discharged, reduce the concentration of flue gas inside the furnace, and reduce the risk of deflagration inside the furnace.

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