High thermal conductivity silicon carbide ceramic suitable for joule heat pressure sintering and preparation method thereof

Abstract

The application relates to the technical field of advanced ceramic material preparation, and discloses high-thermal-conductivity silicon carbide ceramics suitable for joule heat pressure sintering and a preparation method thereof. The method takes silicon carbide powder as main raw material, adds a sintering aid, mixes through ball milling, dries, sieves, and then performs joule heat pressure sintering, realizes rapid densification of the material under the joint action of rapid electric heating and external pressure, and high-thermal-conductivity silicon carbide ceramics are prepared. The application utilizes the characteristics of the joule heat pressure sintering, such as fast heating speed, short sintering period, low energy consumption and high densification efficiency, effectively reduces the porosity of the material, promotes uniform grain growth, and improves the density, thermal conductivity and mechanical properties of the ceramics. Compared with the traditional heat pressure sintering process, the application has the advantages of simple process, high sintering efficiency, excellent comprehensive performance and the like, and is suitable for the fields of electronic packaging, semiconductor heat dissipation and high-temperature thermal management.

Description

Technical Field

[0001] This invention belongs to the field of advanced ceramic material preparation technology, specifically relating to a method for preparing high thermal conductivity silicon carbide ceramics, and more particularly to a method for rapidly preparing high thermal conductivity and high density silicon carbide ceramics by Joule hot pressing sintering. Background Technology

[0002] Silicon carbide (SiC) ceramics are widely used in electronic packaging, semiconductor equipment, aerospace, high-temperature heat exchangers, and new energy fields due to their high thermal conductivity, high hardness, high strength, high temperature resistance, corrosion resistance, wear resistance, low coefficient of thermal expansion, and excellent thermal stability. Among these, high thermal conductivity silicon carbide ceramics are particularly effective in improving device heat dissipation efficiency and reducing thermal stress, thus demonstrating broad application prospects.

[0003] However, due to the strong covalent bond characteristics of silicon carbide and its low self-diffusion coefficient, the sintering driving force is insufficient, making densification difficult. Currently, high-performance silicon carbide ceramics are mainly prepared using methods such as pressureless sintering, hot pressing, hot isostatic pressing, and spark plasma sintering (SPS). Traditional pressureless sintering typically requires high temperatures of 1900–2200℃ and long holding times, placing high demands on sintering aids; while hot pressing can improve density, it involves complex equipment, slow heating rates, long sintering cycles, and low production efficiency; although spark plasma sintering has the advantage of rapid heating, its equipment cost is high, and sample size is limited, hindering industrial-scale promotion.

[0004] Joule hot pressing sintering is a rapid sintering technology developed in recent years. It uses a conductive medium to generate Joule heat, which enables rapid heating of the sample. Combined with external pressure, it promotes particle rearrangement and material diffusion, which can significantly shorten sintering time, reduce energy consumption, and inhibit abnormal grain growth, thereby obtaining ceramic materials with uniform structure and excellent performance.

[0005] However, current research on the preparation of high thermal conductivity silicon carbide ceramics using Joule hot pressing is still limited, especially lacking suitable sintering aid systems and process parameter designs. Existing technologies struggle to simultaneously achieve high density, high thermal conductivity, and rapid sintering efficiency. Therefore, it is necessary to develop a method for preparing high thermal conductivity silicon carbide ceramics using Joule hot pressing to meet the industrial-scale production needs of high-performance silicon carbide ceramics. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies, such as high sintering temperature, long sintering time, high energy consumption, easy abnormal grain growth, and difficulty in simultaneously achieving high thermal conductivity. This invention provides a rapid preparation method for high thermal conductivity silicon carbide ceramics based on Joule hot pressing sintering. This method can achieve rapid densification of silicon carbide ceramics within a short sintering time, resulting in silicon carbide ceramics with high density, high thermal conductivity, and excellent mechanical properties.

[0007] A high thermal conductivity silicon carbide ceramic suitable for Joule hot pressing sintering and its preparation method, comprising the following steps:

[0008] Step 1: Preparation of powder ingredients;

[0009] Weigh out SiC powder, sintering aids (A2O3, Y2O3), and BN powder in a certain proportion;

[0010] Step 2: Mixing the powders;

[0011] The four powders from step one were placed in a ball mill jar, and anhydrous ethanol was added as a dispersion medium to obtain a uniform mixed fraction.

[0012] Step 3: Drying the mixed powder;

[0013] The mixed powder obtained in step two is placed in an oven and sieved to obtain the prepared powder;

[0014] Step 4: Sintering of the mixed powders;

[0015] The powder obtained in step three is placed in a Joule hot pressing sintering equipment, a certain pressure is applied under a protective atmosphere, and the temperature is rapidly raised to the sintering temperature by Joule heating and held at that temperature. After cooling, SiC ceramic is obtained.

[0016] Step 5: Polishing SiC ceramics;

[0017] The SiC ceramic sintered in step four is then polished to obtain a SiC ceramic with high thermal conductivity.

[0018] In step one, the mass fraction of silicon carbide powder is 90wt%-99wt%, the mass fraction of sintering aid Al2O3 is 1wt%-3wt%, the mass fraction of sintering aid Y2O3 is 3wt%-5wt%, and the mass fraction of BN is 1wt%-1.25wt%, which are then mixed to form powder.

[0019] In step two, the four powders are mixed in a ball mill. The total mass of powders to anhydrous ethanol is 1:1.3, the ball-to-powder ratio is 3:1, the ball milling time is 2.5-4 hours, and the rotation speed is 300-350 r / min.

[0020] The powder mixed evenly in step three is placed in a drying oven and dried for 8-10 hours, and then sieved through a 100-mesh sieve.

[0021] In step four, the sieved powder is placed in a Joule hot press mold. The sintering temperature is 1700-2000℃, the sintering pressure is 20-40MPa, the heating rate is 180-240℃ / min, the pressure rate is 6-8MPa / min, and the holding time is 90s.

[0022] In step five, the sintered silicon carbide ceramic is polished with 600-800 grit sandpaper and graphite paper is used to polish the surface of the ceramic.

[0023] The beneficial effects of this invention, which describes a high thermal conductivity silicon carbide ceramic suitable for Joule hot pressing sintering and its preparation method, are as follows:

[0024] This invention utilizes Joule hot-pressing sintering technology to prepare high thermal conductivity silicon carbide ceramics. By leveraging the Joule effect, rapid heating and sintering are achieved. Under varying pressures and with the synergistic effect of the sintering aid system, material diffusion and rapid densification between silicon carbide particles are effectively promoted, resulting in high-density silicon carbide ceramics at relatively low sintering temperatures or short holding times. Simultaneously, the rapid sintering process effectively inhibits abnormal grain growth, reduces porosity and grain boundary impurities, lowers grain boundary thermal resistance, and improves the material's thermal conductivity and overall mechanical properties. Compared to traditional hot-pressing sintering processes, this invention offers advantages such as shorter sintering cycles, lower energy consumption, higher production efficiency, and better process stability. The prepared high thermal conductivity silicon carbide ceramics exhibit excellent thermal conductivity, mechanical properties, and thermal stability, demonstrating promising prospects for industrial applications. Attached Figure Description

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and specific implementation methods.

[0026] Figure 1 This is a scanning electron microscope image of a high thermal conductivity silicon carbide ceramic suitable for Joule hot pressing sintering and its preparation method according to the present invention.

[0027] Figure 2 This is an X-ray diffraction pattern of a high thermal conductivity silicon carbide ceramic suitable for Joule hot pressing sintering and its preparation method according to the present invention.

[0028] Figure 3 This is a density and porosity diagram of a high thermal conductivity silicon carbide ceramic suitable for Joule hot pressing sintering and its preparation method according to the present invention.

[0029] Figure 4 The mechanical properties of a high thermal conductivity silicon carbide ceramic suitable for Joule hot pressing sintering and its preparation method are shown in the figure.

[0030] . Figure 5 This is a hardness diagram of a high thermal conductivity silicon carbide ceramic suitable for Joule hot pressing sintering and its preparation method according to the present invention. Detailed Implementation

[0031] A high thermal conductivity silicon carbide ceramic suitable for Joule hot pressing sintering and its preparation method, comprising the following steps:

[0032] Step 1: Preparation of powder: Weigh out SiC powder, sintering aids (A2O3, Y2O3), and BN powder in a certain proportion.

[0033] The powder consists of silicon carbide powder with a mass fraction of 90wt%-99wt%, sintering aid Al2O3 with a mass fraction of 1wt%-3wt%, sintering aid Y2O3 with a mass fraction of 3wt%-5wt%, and BN with a mass fraction of 1wt%-1.25wt%.

[0034] Step 2, Powder Mixing: Place the four powders in a ball mill jar, add anhydrous ethanol as a dispersion medium, and obtain a uniform mixed fraction.

[0035] The four powders were mixed in a ball mill with a total powder-to-anhydrous ethanol ratio of 1:1.3, a ball-to-powder ratio of 3:1, a ball milling time of 2.5-4 hours, and a rotation speed of 300-350 r / min.

[0036] Step 3: Drying the mixed powder: Place the obtained mixed powder in an oven and sieve it to obtain the prepared powder.

[0037] The uniformly mixed powder is placed in a drying oven and dried for 8-10 hours, and then sieved through a 100-mesh sieve.

[0038] Step 4: Sintering of the mixed powder: The obtained powder is placed in a Joule hot pressing sintering equipment, a certain pressure is applied under a protective atmosphere, and the temperature is rapidly raised to the sintering temperature by Joule heating and held at that temperature. After cooling, SiC ceramic is obtained.

[0039] The sieved powder is placed in a Joule hot press mold, and the sintering temperature is 1700-2000℃, the sintering pressure is 20-40MPa, the heating rate is 180-240℃ / min, the pressure rate is 6-8MPa / min, and the holding time is 90 seconds.

[0040] Step 5: Polishing SiC ceramics: Polish the surface of the sintered SiC ceramics to obtain high thermal conductivity SiC ceramics.

[0041] Among them, the sintered silicon carbide ceramic is polished with 600-800 grit sandpaper and graphite paper is used to polish the surface of the ceramic.

[0042] Example 1:

[0043] Step 1: Mix silicon carbide powder with a mass fraction of 93.5 wt%, sintering aid Al2O3 with a mass fraction of 2.5 wt%, sintering aid Y2O3 with a mass fraction of 4 wt%, and BN with a mass fraction of 1 wt% to form a powder.

[0044] Step 2: The four powders are mixed in a ball mill. The total mass of powders to anhydrous ethanol is 1:1.3, the ball-to-powder ratio is 3:1, the ball milling time is 3 hours, and the rotation speed is 320 r / min.

[0045] Step 3: Place the well-mixed powder in a drying oven and dry for 8 hours, then sieve it through a 100-mesh sieve.

[0046] Step 4: The sieved powder is placed in a Joule hot press mold. The sintering temperature is 1800℃, the sintering pressure is 10MPa, the heating rate is 240℃ / min, the pressure rate is 8MPa / min, and the holding time is 90 seconds.

[0047] Step 5: Polish the sintered silicon carbide ceramic with 600-800 grit sandpaper to remove the graphite paper from the ceramic surface.

[0048] In Example 1, the SiC ceramic after hot pressing and sintering has low pressure, limited particle rearrangement, insufficient densification, many pores, low sample strength, and is prone to breakage or cracking during demolding. Its relative density and thermal conductivity are also low.

[0049] Example 2:

[0050] Step 1: Mix silicon carbide powder with a mass fraction of 93.5 wt%, sintering aid Al2O3 with a mass fraction of 2.5 wt%, sintering aid Y2O3 with a mass fraction of 4 wt%, and BN with a mass fraction of 1 wt% to form a powder.

[0051] Step 2: The four powders are mixed in a ball mill. The total mass of powders to anhydrous ethanol is 1:1.3, the ball-to-powder ratio is 3:1, the ball milling time is 3 hours, and the rotation speed is 320 r / min.

[0052] Step 3: Place the well-mixed powder in a drying oven and dry for 8 hours, then sieve it through a 100-mesh sieve.

[0053] Step 4: The sieved powder is placed in a Joule hot press mold. The sintering temperature is 1800℃, the sintering pressure is 15MPa, the heating rate is 240℃ / min, the pressure rate is 8MPa / min, and the holding time is 90 s.

[0054] Step 5: Polish the sintered silicon carbide ceramic with 600-800 grit sandpaper to remove the graphite from the ceramic surface.

[0055] Compared with the previous example, the SiC ceramic after hot pressing and sintering in Example 1 showed a significant improvement in densification, a reduction in the number of pores, improved sample integrity, and enhanced thermal conductivity and mechanical properties.

[0056] Example 3:

[0057] Step 1: Mix silicon carbide powder with a mass fraction of 93.5 wt%, sintering aid Al2O3 with a mass fraction of 2.5 wt%, sintering aid Y2O3 with a mass fraction of 4 wt%, and BN with a mass fraction of 1 wt% to form a powder.

[0058] Step 2: The four powders are mixed in a ball mill. The total mass of powders to anhydrous ethanol is 1:1.3, the ball-to-powder ratio is 3:1, the ball milling time is 3 hours, and the rotation speed is 320 r / min.

[0059] Step 3: Place the well-mixed powder in a drying oven and dry for 8 hours, then sieve it through a 100-mesh sieve.

[0060] Step 4: The sieved powder is placed in a Joule hot press mold. The sintering temperature is 1800℃, the sintering pressure is 20MPa, the heating rate is 240℃ / min, the pressure rate is 8MPa / min, and the holding time is 90 s.

[0061] Step 5: Polish the sintered silicon carbide ceramic with 600-800 grit sandpaper to remove the graphite paper from the ceramic surface.

[0062] By further increasing the pressure of the sample prepared in Example 3, the particles are in closer contact, the sintering driving force is enhanced, and higher density, uniform structure, fewer pores, and higher levels of thermal conductivity and mechanical properties can be obtained.

[0063] Example 4:

[0064] Step 1: Mix silicon carbide powder with a mass fraction of 93.5 wt%, sintering aid Al2O3 with a mass fraction of 2.5 wt%, sintering aid Y2O3 with a mass fraction of 4 wt%, and BN with a mass fraction of 1 wt% to form a powder.

[0065] Step 2: The four powders are mixed in a ball mill. The total mass of powders to anhydrous ethanol is 1:1.3, the ball-to-powder ratio is 3:1, the ball milling time is 3 hours, and the rotation speed is 320 r / min.

[0066] Step 3: Place the well-mixed powder in a drying oven and dry for 8 hours, then sieve it through a 100-mesh sieve.

[0067] Step 4: The sieved powder is placed in a Joule hot press mold. The sintering temperature is 1800℃, the sintering pressure is 25MPa, the heating rate is 240℃ / min, the pressure rate is 8MPa / min, and the holding time is 90 s.

[0068] Step 5: Polish the sintered silicon carbide ceramic with 600-800 grit sandpaper to remove the graphite paper from the ceramic surface.

[0069] Example 4 shows that the sample prepared under the condition of ensuring the stability of the sintering process has achieved a high density, tight grain bonding, and few residual pores, and the overall performance is further improved, with high thermal conductivity and good mechanical properties.

[0070] Example 5:

[0071] Step 1: Mix silicon carbide powder with a mass fraction of 93.5 wt%, sintering aid Al2O3 with a mass fraction of 2.5 wt%, sintering aid Y2O3 with a mass fraction of 4 wt%, and BN with a mass fraction of 1 wt% to form a powder.

[0072] Step 2: The four powders are mixed in a ball mill. The total mass of powders to anhydrous ethanol is 1:1.3, the ball-to-powder ratio is 3:1, the ball milling time is 3 hours, and the rotation speed is 320 r / min.

[0073] Step 3: Place the well-mixed powder in a drying oven and dry for 8 hours, then sieve it through a 100-mesh sieve.

[0074] Step 4: The sieved powder is placed in a Joule hot press mold. The sintering temperature is 1800℃, the sintering pressure is 30MPa, the heating rate is 240℃ / min, the pressure rate is 8MPa / min, and the holding time is 90 s.

[0075] Step 5: Polish the sintered silicon carbide ceramic with 600-800 grit sandpaper to remove the graphite paper from the ceramic surface.

[0076] Example 5 shows that samples prepared under stable sintering conditions can be further densified to obtain ceramics with densities close to the theoretical density. However, excessive pressure may cause localized stress concentration, accelerated mold wear, or structural defects, thus the performance improvement tends to plateau and may not continue to increase significantly.

Claims

1. A high thermal conductivity silicon carbide ceramic suitable for Joule hot pressing sintering and its preparation method, comprising the following steps: Step 1: Preparation of powder ingredients; Weigh out SiC powder, sintering aids (A2O3, Y2O3), and BN powder in a certain proportion; Step 2: Mixing the powders; The four powders from step one were placed in a ball mill jar, and anhydrous ethanol was added as a dispersion medium to obtain a uniform mixed fraction. Step 3: Drying the mixed powder; The mixed powder obtained in step two is placed in an oven and sieved to obtain the prepared powder; Step 4: Sintering of the mixed powders; The powder obtained in step three is placed in a Joule hot pressing sintering equipment, a certain pressure is applied under a protective atmosphere, and the temperature is rapidly raised to the sintering temperature by Joule heating and held at that temperature. After cooling, SiC ceramic is obtained. Step 5: Polishing SiC ceramics; The SiC ceramic sintered in step four is then polished to obtain a SiC ceramic with high thermal conductivity.

2. The method for preparing SiC ceramics according to claim 1, characterized in that, In step one, the mass fraction of silicon carbide powder is 90wt%-99wt%, the mass fraction of sintering aid Al2O3 is 1wt%-3wt%, the mass fraction of sintering aid Y2O3 is 3wt%-5wt%, and the mass fraction of BN is 1wt%-1.25wt%, which are then mixed to form powder.

3. The method for preparing SiC ceramics according to claim 1, characterized in that, In step two, the four powders are mixed in a ball mill. The total mass of powders to anhydrous ethanol is 1:1.3, the ball-to-powder ratio is 3:1, the ball milling time is 2.5-4 hours, and the rotation speed is 300-350 r / min.

4. The method for preparing SiC ceramics according to claim 1, characterized in that, The powder mixed evenly in step three is placed in a drying oven and dried for 8-10 hours, and then sieved through a 100-mesh sieve.

5. The method for preparing SiC ceramics according to claim 1, characterized in that, In step four, the sieved powder is placed in a Joule hot press mold. The sintering temperature is 1700-2000℃, the sintering pressure is 20-40MPa, the heating rate is 180-240℃ / min, the pressure rate is 6-8MPa / min, and the holding time is 90 seconds.

6. The method for preparing SiC ceramics according to claim 1, characterized in that, In step five, the sintered silicon carbide ceramic is polished with 600-800 grit sandpaper and graphite paper is used to polish the surface of the ceramic.

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