Silicon carbide ceramic containing a carbon phase and method for producing the same

Abstract

The application belongs to the field of ceramic preparation, and particularly relates to a silicon carbide ceramic containing a carbon phase and a preparation method thereof. The preparation method comprises the following steps: raw materials are composed of the following components with the following weight contents: 75-87 wt% micron-sized silicon carbide powder, 5-15 wt% carbon source (carbon phase), 2-4 wt% sintering aid, (2±0.1) wt% dispersant and (4±0.1) wt% binder; the raw materials are mixed with water and then ball milled; the obtained mixed slurry is spray dried to obtain granulated powder; and the obtained granulated powder is hot-pressed and sintered to obtain the silicon carbide ceramic containing the carbon phase. The silicon carbide ceramic of the application exhibits excellent comprehensive performance in high-temperature structural components, wear-resistant and corrosion-resistant assemblies and thermal management fields, and is suitable for industrial environments with synergistic requirements for mechanical strength and thermophysical performance.

Description

Technical Field

[0001] This invention belongs to the field of ceramic preparation, specifically relating to a carbon-phase silicon carbide ceramic and its preparation method. Background Technology

[0002] Carbon-containing silicon carbide ceramics are ceramic materials that combine carbon and silicon carbide phases. These materials cleverly combine the inherent high strength, high hardness, and excellent high-temperature stability of silicon carbide ceramics with the self-lubricating properties, excellent thermal conductivity, and superior thermal shock resistance of the carbon phase. Due to these comprehensive performance advantages, this material shows broad application prospects in high-temperature sintered load-bearing components (such as sintering plates and push plates), aerospace thermal protection systems, wear-resistant and corrosion-resistant parts, and electronic packaging. Its performance is particularly outstanding in structural components that require good wear resistance, a certain level of thermal conductivity and thermal shock resistance, and high mechanical strength.

[0003] Currently, the industrial preparation and application of carbon-phase silicon carbide ceramics mainly face the following technical challenges: When the carbon phase (such as carbon graphite) content reaches 5-15 wt%, the interfacial bonding force between the carbon phase and the silicon carbide matrix is ​​weak, and the carbon phase inhibits atomic diffusion at high temperatures. This significantly increases the difficulty of sintering and densifying the material. To obtain high-density products, higher sintering temperatures or greater external pressures are often required, which not only increases energy consumption and equipment burden but also easily induces abnormal growth of silicon carbide grains, leading to material performance degradation. Furthermore, in material design, strong… There is often a contradictory relationship between strength and toughness / thermal conductivity. Although the introduced carbon phase can improve the toughness of the material to a certain extent through crack deflection, bridging and other mechanisms, and enhance the thermal conductivity and thermal shock resistance, if its distribution is uneven or the proportion is inappropriate, the carbon phase itself will become a mechanical weak point in the material, resulting in a significant reduction in bending strength, making it difficult to meet the strict strength requirements of high load conditions. Thirdly, traditional pressureless sintering or reaction sintering processes often face problems of low density and insufficient performance stability when preparing silicon carbide ceramics with low to medium carbon content, affecting the phase composition and performance of the final material.

[0004] Hot pressing sintering technology, as an advanced ceramic preparation method, provides an effective way to overcome the aforementioned challenges in preparing graphite-composite silicon carbide ceramics. This technology involves applying unidirectional mechanical pressure to the green body along a specific direction during heating and sintering. This external pressure provides additional driving force for the sintering process. It significantly promotes densification and effectively improves material properties, helping to maximize the mechanical strength and toughness of the material while ensuring a certain carbon phase content, thus achieving a good balance between strength and functionality.

[0005] In recent years, several patents have been reported on the preparation of high-performance silicon carbide ceramics through composite reinforcement with silicon carbide ceramics and carbon phases. However, targeted optimization for composite systems with 5-15 wt% carbon phase is still insufficient, and existing technologies mainly have the following limitations:

[0006] Patent CN109592983A discloses a method for preparing high thermal conductivity silicon carbide ceramics using hot pressing sintering. It uses cerium oxide, yttrium oxide, and erbium oxide as sintering aids, and reports a thermal conductivity of up to 150 W / (m·K). However, this patented technology does not involve the introduction of a carbon phase and does not form a silicon carbide / graphite composite system, thus failing to solve the unique interfacial bonding and densification problems in graphite composites. Patent CN118047621A discloses a method for preparing fiber-reinforced silicon carbide composite materials. It mainly uses submicron silicon carbide powder as raw material and modified carbon fibers as additives, obtaining carbon fiber-reinforced silicon carbide ceramics through vacuum hot pressing sintering. This technology focuses on achieving extremely high mechanical strength, using carbon fibers as the reinforcing phase, but does not address the material's thermal conductivity, thermal shock resistance, and self-lubricating properties, making it difficult to meet the needs of applications requiring comprehensive performance. Patent CN116621584A discloses a micro-lamellar structure-reinforced silicon carbide ceramic composite material. It primarily uses micron-sized silicon carbide as the raw material, yttrium aluminum garnet as a sintering aid, and incorporates graphene and silicon carbide whiskers as reinforcing phases, ultimately obtaining a high-strength silicon carbide ceramic through hot pressing sintering. Although this technology introduces graphene as a carbon component, the total carbon phase content is typically low, only 2-8 wt%, and no systematic optimization is performed for composite systems with a medium carbon phase content of 5-15 wt%. Furthermore, this patent primarily focuses on the structural strength of the composite ceramic, without testing properties such as thermal conductivity and thermal shock resistance.

[0007] While the aforementioned existing technologies have achieved valuable results in certain aspects of hot pressing sintering or composite reinforcement, they have failed to organically combine hot pressing sintering process with medium carbon phase composite technology, and have failed to effectively solve the core problem of how to balance and optimize the material's strength, toughness, thermal conductivity, and thermal shock resistance under conditions of 5~15wt% carbon phase. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a silicon carbide ceramic containing a carbon phase and a method for preparing the same.

[0009] To address the aforementioned technical problems, this invention provides a method for preparing silicon carbide ceramics containing a carbon phase, comprising the following steps:

[0010] 1) Raw material mixing and ball milling:

[0011] The raw material consists of the following components by weight: 75~87 wt% micron-sized silicon carbide powder (micron-sized α-silicon carbide powder, particle size 5~20μm, purity ≥99.5%), 5~15 wt% carbon source (carbon phase), 2~4 wt% sintering aid (selected inorganic compound), (2 ±0.1) wt% dispersant and (4 ±0.1) wt% binder;

[0012] The raw materials are mixed with water (deionized water as the medium) and then ball-milled to obtain a mixed slurry;

[0013] 2) Spray granulation:

[0014] The mixture slurry obtained in step 1) is spray-dried to obtain granulated powder (spherical granulated powder with good flowability).

[0015] 3) Hot pressing and sintering:

[0016] The granulated powder obtained in step 2) is hot-pressed and sintered to obtain silicon carbide ceramics containing carbon phase.

[0017] As an improvement to the preparation method of the carbon-containing silicon carbide ceramic of the present invention, step 3) is as follows:

[0018] The granulated powder obtained in step 2) is filled into a graphite mold and placed in a hot press sintering furnace. The initial pressure is set to 5±0.5 MPa. Then, the furnace cavity is evacuated and heated to the discharge temperature according to the set heating program one and held at the temperature (pressure) for 1~2 hours. Then, the temperature is heated to the sintering temperature according to the set heating program two, and at the same time, the pressure is increased to the sintering pressure. Then, the temperature and pressure are held at the sintering temperature and sintering pressure for 30~90 min (preferably 60 min). Then, the furnace is cooled to obtain silicon carbide ceramic containing carbon phase.

[0019] The glue discharge temperature is 400±50℃;

[0020] The sintering temperature is 2000℃~2100℃, and the sintering pressure is 30±0.5 MPa.

[0021] Note: Silicon carbide ceramics containing carbon phase undergo conventional demolding, processing, and other post-treatments to obtain silicon carbide ceramics containing carbon phase as the product.

[0022] As a further improvement to the preparation method of the carbon-containing silicon carbide ceramic of the present invention:

[0023] The carbon source is a graphite composite phase composed of micron-sized graphite powder (particle size 20~40μm, purity ≥99%), nano-sized graphite powder (particle size 80~100nm, purity ≥99%), and graphite whiskers (diameter 6~10μm, aspect ratio approximately 60:1, purity ≥98%) in a mass ratio of 1~6:1~6:3.

[0024] The sintering aid is at least one of the following: boron carbide, alumina, or yttrium oxide;

[0025] The dispersant is polyethylene glycol;

[0026] The adhesive is polyvinyl alcohol.

[0027] As a further improvement to the preparation method of the carbon-containing silicon carbide ceramic of the present invention:

[0028] The weight ratio of raw materials to water is 1:1.4~1.6;

[0029] The ball milling time is 8~12 hours (to ensure uniform mixing of raw materials and fine particle size).

[0030] As a further improvement to the preparation method of the carbon-containing silicon carbide ceramic of the present invention:

[0031] In step 3), the heating rate of both heating program one and heating program two is 8~10 ℃ / min.

[0032] As a further improvement to the preparation method of the carbon-containing silicon carbide ceramic of the present invention:

[0033] In step 2) spray granulation, the slurry feed rate is 40~60 mL / min, the hot air inlet temperature is 280±5℃, the outlet temperature is 70~90℃, and the centrifugal atomizer frequency is 40~70 Hz.

[0034] As a further improvement to the preparation method of the carbon-containing silicon carbide ceramic of the present invention:

[0035] The raw material consists of the following components by weight: 81 wt% micron-sized α-silicon carbide powder, 10 wt% graphite composite phase, 3 wt% boron carbide, 2 wt% polyethylene glycol, and 4 wt% polyvinyl alcohol.

[0036] In the graphite composite phase, the mass ratio of micron-sized graphite powder, nano-sized graphite powder and graphite whiskers is 5:2:3.

[0037] The present invention also provides silicon carbide ceramics containing carbon phases prepared by any of the above methods.

[0038] The silicon carbide ceramic containing a carbon phase prepared by hot pressing sintering of the present invention has a carbon phase content of 5~15wt%, and as a preferred embodiment, a bulk density ≥3.05 g / cm³ and a flexural strength ≥280 MPa.

[0039] The method of this invention can solve the problems of how to achieve high strength and high density of silicon carbide ceramics containing 5-15 wt% carbon phase while maintaining good thermal and electrical conductivity, as well as the difficulty of balancing the mechanical properties and functional characteristics of materials in traditional sintering processes.

[0040] The preparation method of this invention was obtained by the inventors through systematic research and experimental optimization. This invention, through a cost-effective additive system and optimized process parameters, achieves high material densification while cleverly balancing its strength and functionality through the composite of various graphite additives. This represents a key direction for breaking through current technological bottlenecks and promoting the wider application of this type of high-performance material.

[0041] The technical advantage of this invention lies in achieving an optimal balance between material densification and performance under 5-15 wt% carbon phase conditions through an optimized hot-pressing sintering process. External pressure effectively promotes particle rearrangement and diffusion processes, achieving high densification at relatively low temperatures while ensuring a uniform distribution of the carbon phase. The carbon-containing silicon carbide ceramics prepared by this process possess excellent mechanical strength, superior thermal conductivity, and thermal shock resistance, making them particularly suitable for applications such as high-temperature structural components, electronic packaging carriers, wear-resistant parts, and thermal management components, demonstrating significant industrial application value.

[0042] In summary, the present invention relates to silicon carbide ceramics containing 5-15 wt% carbon phase and their hot-pressing sintering preparation method. This material uses silicon carbide as the main matrix, forming a composite structure by introducing an appropriate amount of carbon phase, and achieving material densification through a hot-pressing sintering process. In this invention, the introduction of the carbon phase effectively improves the material's fracture toughness, thermal conductivity, and thermal shock resistance, while the silicon carbide matrix ensures the material's strength, hardness, and high-temperature load-bearing capacity. This silicon carbide ceramic exhibits excellent comprehensive performance in high-temperature structural components, wear-resistant and corrosion-resistant components, and thermal management applications, and is suitable for industrial environments where synergistic requirements for mechanical strength and thermophysical properties are present. Attached Figure Description

[0043] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0044] Figure 1 A photograph of the carbon-containing silicon carbide ceramic prepared in Example 1 of this invention;

[0045] Figure 2 Metallographic photograph of the carbon-containing silicon carbide ceramic prepared in Example 1 of this invention;

[0046] Figure 3 This is an elemental distribution diagram of the carbon-containing silicon carbide ceramic prepared in Example 1 of this invention. Detailed Implementation

[0047] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0048] Micron-sized α-silicon carbide powder: particle size 5~20μm; purity ≥99.5%;

[0049] Micron-sized graphite powder: particle size 20~40μm, purity ≥99%;

[0050] Nanoscale graphite powder: particle size 80~100nm, purity ≥99%;

[0051] Graphite whiskers: diameter 6~10μm, aspect ratio approximately 60:1, purity ≥98%;

[0052] Polyethylene glycol (PEG): Average molecular weight (mw) 1000;

[0053] Polyvinyl alcohol (PVA): average molecular weight (mw) 20,500, degree of alcoholysis 88-89%.

[0054] Example 1: A method for preparing silicon carbide containing a carbon phase (using hot pressing sintering), comprising the following steps:

[0055] 1) Powder raw material composition: 81 wt% micron-sized α-silicon carbide powder, 10 wt% graphite composite phase, 3 wt% boron carbide sintering aid, 2 wt% polyethylene glycol dispersant, and 4 wt% polyvinyl alcohol binder are weighed according to the following mass fractions. Among them, the mass ratio of micron-sized graphite powder, nano-sized graphite powder and graphite whiskers in the graphite composite phase is 5:2:3.

[0056] The weighed powder raw material is added to a ball mill, and deionized water at a weight of 1.5 times that of the powder raw material is added. The mixture is stirred and ball milled for 8 hours to prepare a uniform water-based slurry (mixed slurry).

[0057] 2) The water-based slurry is spray-granulated to prepare spherical granulated powder. The parameters of the spray granulation tower are: hot air inlet temperature 280 ℃, outlet temperature 86 ℃, centrifugal atomizer frequency 48 Hz. After the temperature of the granulation tower reaches the set parameters, the feed pump is turned on and the water-based slurry obtained in step 1) is introduced into the granulation tower at a flow rate of 40 mL / min. Finally, ceramic granulated powder with uniform particle size and good flowability is obtained.

[0058] 3) Fill the ceramic granulation powder into the graphite mold of the hot pressing sintering furnace. First, apply a pressure of 5 MPa for pre-pressing. Then, evacuate the furnace cavity and start the heating process: heat up to 400 ℃ at a heating rate of 8 ℃ / min to remove the binder, and hold at 400 ℃ and 5 MPa for 60 min to remove the binder. Then, heat up to 2000 ℃ at a rate of 10 ℃ / min and increase the pressure to 30 MPa at a uniform rate during the heating process. Sinter at this temperature (2000 ℃) and pressure (30 MPa) for 60 min, and then cool with the furnace.

[0059] After the sintered silicon carbide ceramic block containing carbon phase is demolded, it is processed by conventional cutting and surface polishing to obtain silicon carbide ceramic products.

[0060] The performance of the obtained products is tested using standard testing methods in this industry, for example:

[0061] Density: The density was tested by Archimedes' displacement method. The sample size was 20×30×10 mm.

[0062] Bending strength: The bending strength was tested by the three-point bending method (GB-T 4740-2024 Test Method for Strength of Ceramic Materials), and the test sample size was 3×4×40 mm.

[0063] Electrical conductivity: tested using the four-probe method, with a sample size of 20×20×10 mm; refer to GB / T 1410-1989 Test methods for volume resistivity and surface resistivity of solid insulating materials.

[0064] Thermal conductivity: Tested by steady-state method (GB / T 39862-2021 Test of thermal conductivity of high thermal conductivity ceramics), test sample size: 4×4×25 mm.

[0065] The carbon-containing silicon carbide ceramic obtained in Example 1 exhibits good sintering density and mechanical properties. The carbon phase contributes to the excellent thermoelectric properties of the silicon carbide ceramic matrix, while the graphite whiskers also act as a reinforcing phase; the density reaches 3.063 g / cm³. 3 It has a flexural strength of 332.7 MPa, an electrical conductivity of 4.172 S / cm, and a thermal conductivity of 157.30 W / (m·K) at room temperature.

[0066] Example 2: The following changes are made compared to Example 1:

[0067] Step 3) The sintering temperature was changed from 2000 ℃ to 2100 ℃, and the sintering time was changed from 60 min to 90 min.

[0068] The rest is the same as in Example 1.

[0069] Compared to Example 1, the most significant changes in Example 2 were an increase in sintering temperature and a longer sintering time. With these changes in sintering process parameters, the sintering density of the sample slightly increased, but the thermal and electrical conductivity decreased to some extent. This may be due to the oxidation and evaporation of the carbon phase caused by excessively high sintering temperature, resulting in internal defects. The density was 3.092 g / cm³. 3 It has a flexural strength of 348.2 MPa, an electrical conductivity of 3.811 S / cm, and a thermal conductivity of 151.56 W / (m·K) at room temperature.

[0070] Example 3: The following changes are made compared to Example 1:

[0071] Step 3) The sintering temperature was changed from 2000 ℃ to 1950 ℃, and the sintering time was changed from 60 min to 30 min.

[0072] The rest is the same as in Example 1.

[0073] Compared to Example 1, the most significant changes in Example 3 were the reduction in sintering temperature and sintering time. With these changes in sintering process parameters, the sintering density of the sample decreased significantly, resulting in reduced thermodynamic properties; its density was 2.983 g / cm³. 3 It has a flexural strength of 295.6 MPa, an electrical conductivity of 0.1681 S / cm, and a thermal conductivity of 82.92 W / (m·K) at room temperature.

[0074] Example 4: The following changes are made compared to Example 1:

[0075] Step 1) The powder raw material composition was changed to: 75 wt% micron-sized α-silicon carbide powder, 15 wt% graphite composite phase, 4 wt% boron carbide sintering aid, 2 wt% polyethylene glycol dispersant, and 4 wt% polyvinyl alcohol binder were weighed according to the following mass fractions. The graphite composite phase was the same as in Example 1.

[0076] The rest is the same as in Example 1.

[0077] Compared to Example 1, the most significant change in Example 4 is the increased proportion of carbon phase. Although theoretically, increasing the proportion of graphite composite phase helps improve the thermal conductivity and thermal conductivity of the composite ceramic material, the final sample obtained in this example showed a significant decrease in density and mechanical properties, with a density of 2.915 g / cm³. 3 The flexural strength was 207.6 MPa, which proved that there were a lot of defects inside the ceramic material, affecting its performance. The final sample had an electrical conductivity of 3.982 S / cm and a room temperature thermal conductivity of 162.45 W / (m·K), with only a certain degree of improvement in thermal conductivity.

[0078] Example 5: The following changes are made compared to Example 1:

[0079] Step 1) The powder raw material composition was modified to include 87 wt% micron-sized α-silicon carbide powder, 5 wt% nano-sized graphite powder, 2 wt% boron carbide, 2 wt% polyethylene glycol, and 4 wt% polyvinyl alcohol by mass fraction. The graphite composite was prepared in the same manner as in Example 1.

[0080] The rest is the same as in Example 1.

[0081] Compared to Example 1, the most significant change in Example 5 is the reduced proportion of carbon phase added. Example 5 exhibits good density and mechanical properties, but it provides virtually no electrical conductivity; its density is 3.112 g / cm³. 3 It has a flexural strength of 382.1 MPa, an electrical conductivity of 0.0487 S / cm, and a thermal conductivity of 153.48 W / (m·K) at room temperature.

[0082] Example 6: The following changes are made compared to Example 1:

[0083] In step 1), the mass ratio of micron-sized graphite powder, nano-sized graphite powder and graphite whiskers in the graphite composite phase is changed to 1:6:3.

[0084] The rest is the same as in Example 1.

[0085] Compared to Example 1, the biggest change in Example 6 is the proportion of the various components in the graphite composite phase, with an increased proportion of nano-graphite powder. Example 6 exhibits excellent density and mechanical properties, but its cost is higher and only some properties are slightly superior to Example 1; its density is 3.085 g / cm³. 3 It has a flexural strength of 331.1 MPa, an electrical conductivity of 4.177 S / cm, and a thermal conductivity of 161.26 W / (m·K) at room temperature.

[0086] Example 7: The following changes are made compared to Example 1:

[0087] In step 1), the mass ratio of micron-sized graphite powder, nano-sized graphite powder and graphite whiskers in the graphite composite phase is modified to 6:1:3.

[0088] The rest is the same as in Example 1.

[0089] Compared to Example 1, the biggest change in Example 7 is the proportion of the various components in the graphite composite phase, with an increased proportion of micron-sized graphite powder. Due to the coarser overall particle size, internal defects increased during sintering, resulting in lower overall performance for Example 7 compared to Example 1, with a density of 3.023 g / cm³. 3 It has a flexural strength of 309.4 MPa, an electrical conductivity of 3.891 S / cm, and a thermal conductivity of 134.03 W / (m·K) at room temperature.

[0090] Comparative Example 1: The following changes were made compared to Example 1:

[0091] In step 1), the carbon source in the powder raw material composition is completely replaced by nanoscale graphite powder instead of graphite composite phase. The amount of carbon source remains unchanged, and the rest is the same as the powder raw material in Example 1.

[0092] Since the overall carbon source consists of nano-sized graphite powder with very small particle size, a large amount of nano-graphite powder is prone to agglomeration when directly added to the slurry. Therefore, it is necessary to prepare a dispersion with a certain solid content in advance so that the carbon element can be evenly distributed in the silicon carbide ceramic matrix. The specific operation is as follows: the weighed nano-graphite powder is placed in a stirrer, deionized water and polyethylene glycol (nano-graphite powder: added polyethylene glycol = 98:2) are added as a dispersant and stirred for 8 hours to obtain a nano-graphite powder dispersion with a solid content of 20%. Then, the nano-graphite powder dispersion and the other components of the powder raw material other than nano-graphite powder are added to a ball mill, and a certain amount of deionized water is added so that the total amount of deionized water is still 1.5 times the weight of the powder raw material. Stir and ball mill for 8 hours to prepare a uniform water-based slurry.

[0093] The rest is the same as in Example 1.

[0094] Compared to Example 1, the biggest change in Comparative Example 1 is the change in the carbon source. Compared to Example 1, this example requires first preparing a nano-graphite powder dispersion, which is more cumbersome; and the increased amount of nano-graphite powder leads to an overall increase in cost. Furthermore, since no graphite whisker reinforcing phase was added, its mechanical properties are inferior to those of Example 1, which included graphite whiskers; the final sample density is 3.062 g / cm³. 3 It has a flexural strength of 304.9 MPa, an electrical conductivity of 4.510 S / cm, and a thermal conductivity of 155.3 W / (m·K) at room temperature.

[0095] Comparative Example 2: The following changes were made compared to Example 1:

[0096] In step 1), the carbon source in the powder raw material composition is completely replaced by micron-sized graphite instead of graphite composite phase, while the amount of carbon source remains unchanged; the rest is the same as in Example 1.

[0097] Compared to Example 1, the biggest change in Comparative Example 2 is the change in the carbon source. Compared to Example 1, the increased graphite particle size leads to more internal defects due to stress changes during sintering. Furthermore, the lack of whisker reinforcement results in a decline in various properties, with a density of 2.983 g / cm³. 3It has a flexural strength of 273.6 MPa, an electrical conductivity of 0.698 S / cm, and a thermal conductivity of 113.5 W / (m·K) at room temperature.

[0098] Comparative Example 3: The following changes were made compared to Example 1:

[0099] In step 1), the carbon source in the powder raw material composition is completely replaced by graphite whiskers instead of graphite composite phase, while the amount of carbon source remains unchanged; the rest is the same as in Example 1.

[0100] Compared to Example 1, the biggest change in Comparative Example 3 is the replacement of the carbon source with graphite whiskers, which have a higher aspect ratio. Due to the change in the morphology of the carbon source, the graphite changes from granular to fibrous graphite whiskers. Since these whiskers act as a more reinforcing phase, the mechanical properties are somewhat improved compared to Example 1. However, the morphology leads to reduced dispersion uniformity, resulting in uneven carbon distribution within the composite ceramic. Therefore, the overall thermal and electrical conductivity does not exceed that of Example 1, and its density is 3.015 g / cm³. 3 It has a flexural strength of 349.1 MPa, an electrical conductivity of 3.841 S / cm, and a thermal conductivity of 131.8 W / (m·K) at room temperature.

[0101] Comparative Example 4: A method for preparing silicon carbide containing a carbon phase by hot pressing sintering, comprising the following steps in sequence:

[0102] Step 1) Modify the powder raw material composition to weigh out 92 wt% micron-sized α-silicon carbide powder, 2 wt% boron carbide, 2 wt% polyethylene glycol, and 4 wt% polyvinyl alcohol by mass fraction.

[0103] Compared to Example 1, the biggest change in the comparative examples is the absence of a carbon phase in the composite process. Comparative Example 4 exhibits higher mechanical properties but is essentially an insulator, with a density of 3.189 g / cm³. 3 The flexural strength is 412.7 MPa, and the electrical conductivity is 4.36 × 10⁻⁶ MPa. -2 The thermal conductivity at room temperature is 187.6 W / (m·K), with a density of S / cm.

[0104] Finally, it should be noted that the above examples are merely some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing silicon carbide ceramics containing a carbon phase, characterized in that... Includes the following steps: 1) Raw material mixing and ball milling: The raw material consists of the following components by weight: 75~87 wt% micron-sized silicon carbide powder, 5~15 wt% carbon source, 2~4 wt% sintering aid, (2 ±0.1) wt% dispersant and (4 ±0.1) wt% binder; The raw materials are mixed with water and then ball-milled to obtain a slurry. The carbon source is a graphite composite phase composed of micron-sized graphite powder, nano-sized graphite powder, and graphite whiskers in a mass ratio of 1~6:1~6:3; 2) Spray granulation: The mixture slurry obtained in step 1) is spray-dried to obtain granulated powder; 3) Hot pressing and sintering: The granulated powder obtained in step 2) is subjected to hot pressing sintering: the sintering temperature is 2000℃~2100℃ and the sintering pressure is 30±0.5 MPa for 30~90 min to obtain silicon carbide ceramics containing carbon phase.

2. The method for preparing silicon carbide ceramics containing a carbon phase according to claim 1, characterized in that... Step 3) is as follows: The granulated powder obtained in step 2) is filled into a graphite mold and placed in a hot press sintering furnace. The initial pressure is set to 5±0.5 MPa. Then, the furnace cavity is evacuated and heated to the discharge temperature according to the set heating program one and kept at the temperature for 1~2 hours. Then, it is heated to the sintering temperature according to the set heating program two, and at the same time, the pressure is increased to the sintering pressure. Then, it is kept at the sintering temperature and sintering pressure for 30~90 minutes and then cooled with the furnace to obtain silicon carbide ceramic containing carbon phase. The glue discharge temperature is 400±50℃, and the heating rate of both heating program one and heating program two is 8~10 ℃ / min.

3. The method for preparing silicon carbide ceramics containing a carbon phase according to claim 2, characterized in that: The sintering aid is at least one of the following: boron carbide, alumina, or yttrium oxide; The dispersant is polyethylene glycol; The adhesive is polyvinyl alcohol.

4. The method for preparing silicon carbide ceramics containing a carbon phase according to claim 3, characterized in that: The weight ratio of raw materials to water is 1:1.4~1.6; The ball milling time is 8~12 hours.

5. The method for preparing silicon carbide ceramics containing a carbon phase according to claim 4, characterized in that: In step 2) spray granulation, the slurry feed rate is 40~60 mL / min, the hot air inlet temperature is 280±5℃, the outlet temperature is 70~90℃, and the centrifugal atomizer frequency is 40~70 Hz.

6. The method for preparing silicon carbide ceramics containing a carbon phase according to any one of claims 1 to 5, characterized in that: The raw material consists of the following components by weight: 81 wt% micron-sized α-silicon carbide powder, 10 wt% graphite composite phase, 3 wt% boron carbide, 2 wt% polyethylene glycol, and 4 wt% polyvinyl alcohol. In the graphite composite phase, the mass ratio of micron-sized graphite powder, nano-sized graphite powder and graphite whiskers is 5:2:

3.

7. The silicon carbide ceramic containing a carbon phase prepared by any one of claims 1 to 6.

Images