Diamond / silicon carbide composite material and ultrasonic-assisted gradient high-pressure preparation method thereof

Abstract

The invention discloses a diamond / silicon carbide composite material and an ultrasonic-assisted gradient high-pressure preparation method thereof, and belongs to the technical field of superhard composite materials. According to the method, by means of multi-grading raw material design (silicon powder of 1-100 microns, silicon carbide powder of 1-100 microns and diamond micro-powder of 10-100 microns), powder distribution is optimized in combination with ultrasonic dispersion (20-50 kHz, 200-500 W / L), gradient presintering (2-20 DEG C / min, and staged temperature control) is carried out under inert gas protection, and multi-directional high-pressure sintering (3-5.5 GPa, 1200-1500 DEG C) is carried out through a cubic press. The density of the obtained composite material is larger than or equal to 96%, the heat conductivity coefficient is larger than or equal to 480 W / (m.K), the interface bonding strength is improved to 150 MPa or above, and the problems of interface layering and stress concentration in a traditional technology are remarkably solved. The method is high in process parameter controllability and suitable for the high-end fields of aerospace, electronic device heat dissipation, high-temperature furnace lining materials and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of superhard composite materials and extreme manufacturing technologies, and particularly relates to a method for preparing high-density diamond / silicon carbide (Diamond / SiC) composite materials through an ultrasonic dispersion-gradient pre-sintering-multi-directional high-pressure collaborative process, which is particularly applicable to scenarios with stringent requirements for the comprehensive performance of materials, such as precision cutting tools, heat sinks for high-power lasers, and neutron absorption components in nuclear reactors. Background Art

[0002] Diamond / silicon carbide composite materials have important applications in fields such as precision cutting tools, optical devices, and semiconductor packaging due to their extremely high hardness, thermal conductivity, and wear resistance. However, traditional preparation processes have significant defects: on the one hand, the interfacial bonding strength between diamond and silicon carbide is insufficient, resulting in easy delamination or brittle fracture of the materials; on the other hand, the matching of high-temperature and high-pressure synthesis process parameters is poor, and internal stress concentration is often caused by differences in thermal expansion coefficients, reducing the density and mechanical properties of the materials. In addition, existing technologies mostly rely on high-cost raw materials or complex post-treatment processes, which restricts industrial promotion.

[0003] In the prior art, the mixing method using single-sized raw materials or simple mechanical mixing easily leads to uneven composition distribution and affects the sintering uniformity; the pre-sintering stage lacks inert gas protection and gradient heating design, which easily causes oxidation or out-of-control phase transformation; in the forming process, the connection between cold pressing and hot pressing parameters is insufficient, resulting in low green density or residual structural defects. These problems limit the improvement of the comprehensive performance of composite materials, and there is an urgent need for a preparation method that takes into account process feasibility and performance optimization. Summary of the Invention

[0004] In view of the above problems, the object of the present invention is to propose a method for preparing diamond / silicon carbide composite materials based on multi-scale raw material collaborative dispersion and stepped high-pressure sintering. By precisely controlling the particle size ratio of raw materials, ultrasonic dispersion process, and gradient heating strategy, the interfacial bonding and densification process are optimized, thereby breaking through the bottleneck of traditional processes and realizing the low-cost and high-stability preparation of high-performance diamond / silicon carbide composite materials. Technical Solution

[0005] To achieve the above object, the technical solution of the present invention is as follows: Step 1: Raw material selection. Select high-purity silicon powder, silicon carbide powder (green or black), and diamond powder as the basic raw materials. Among them, the particle size of the high-purity silicon powder is controlled at 1-100 μm, and the proportion is 5 wt.%-40 wt.%; the particle size of the silicon carbide powder is controlled at 1-100 μm, and the proportion is 5 wt.%-40 wt.%; the particle size of the diamond micropowder is 10-100 μm, and the proportion is 20 wt.%-90 wt.%. Additionally, a dispersant is added.

[0006] Step 2: Mixing. Add silicon powder, silicon carbide powder and diamond powder into a beaker containing a dispersant, and perform ultrasonic wet dispersion. Place the obtained mixed slurry in a vacuum drying oven for drying to obtain mixed powder.

[0007] Further, for the mixing in Step 2, the ultrasonic frequency is 20 - 50 kHz, and the mixing time is 60 - 90 min; the dispersant is anhydrous ethanol or deionized water, and the addition amount is 20 - 30% of the total mass of the powder. The drying temperature is 40 - 80 °C, the drying time is 5 - 12 h, and the vacuum degree of the vacuum drying oven is ≤10 Pa.

[0008] Step 3: Pre-sintering. Put the mixed powder obtained in Step 2 into a tubular furnace for sintering to obtain the pre-sintered mixed powder. After sieving it 3 - 5 times, perform internal assembly to obtain a synthetic rod.

[0009] Further, for the pre-sintering in Step 3, an inert gas (such as argon) is passed through the tubular furnace, the gas purity is ≥99.999%, the flow rate is 30 - 50 mL / min, the heating rate is 2 - 20 °C / min, the holding time is ≥2 h, the sieve mesh is 30 - 50 meshes, and for internal assembly, it is assembled into a block using a molybdenum cup or a zirconium cup.

[0010] Step 4: Pre-pressing and forming. Use a hydraulic press to press the internally assembled block obtained in Step 3 into shape. After external assembly, put it into an oven for heat preservation.

[0011] Further, the pre-pressing in Step 4 is cold pressing, the pressure of the hydraulic press is set to 4 MPa - 8 MPa, the pressure holding time is 10 s - 20 s, the temperature of the oven is set to 80 - 140 °C, and the heat preservation time is ≥2 h.

[0012] Step 5: High-temperature and high-pressure forming. Quickly transfer the externally assembled and dried sample to a top press for high-temperature and high-pressure forming. After heating is completed, perform slow pressure relief, cooling, and take it out after the temperature in the cavity drops to room temperature.

[0013] Further, the top press in Step 5 is a domestic hinge-type six-sided top press, the pressure is set to 3 GPa - 5.5 GPa, the temperature is set to 1200 °C - 1500 °C, the time for maintaining pressure and temperature is 5 min - 10 min, and the heating rate is controlled at 400 - 800 °C / min.

[0014] Step 6: Grinding and polishing. For the taken-out ceramic sample, first roughly grind off the cup, then polish it, roughly polish it until it is flat, and then finely polish it. After impurity removal and cleaning, a diamond / silicon carbide composite material is obtained.

[0015] Further, in the grinding and polishing process of Step 6, a diamond grinding disc is selected for rough grinding, a cloth wheel or a woolen cloth is selected for rough polishing, a silk cloth is selected for fine polishing, the polishing agent is a diamond polishing agent, and the rotation speed of the polishing machine is 300 - 620 r / min.

[0016] Advantages of the present invention: First, by precisely controlling the raw material ratio and various process parameters, the densification of the composite material can be effectively improved, making its internal structure more uniform, thereby significantly enhancing key performance indicators such as the hardness, wear resistance, and thermal stability of the material. Second, the preparation method is simple to operate, the process flow is relatively simplified, the production cycle is short, and the cost is low, which is conducive to realizing large-scale industrial production, can effectively reduce the manufacturing cost of diamond / silicon carbide composite materials, and improve market competitiveness.

[0017] In addition, the method of the present invention has moderate requirements for equipment, is easy to implement under existing industrial production conditions, and the product quality is stable and reliable, with good repeatability, which can meet the diverse performance requirements of composite materials in different application scenarios, provide solid technical support for the wide application of diamond / silicon carbide composite materials in high-end fields such as precision cutting tools and heat sinks for high-power lasers, and promote the technological progress and product upgrading of related industries. Description of the drawings

[0018] Figure 1 is the technical roadmap of the present invention Specific embodiments

[0019] The present invention will be further described below in conjunction with specific embodiments: Embodiment

[0020] A diamond / silicon carbide composite material, in terms of mass percentage, consists of the following raw materials: 20% high-purity silicon powder, 10% silicon carbide, and 70% diamond micropowder.

[0021] Weigh the raw materials according to the above ratio. Put high-purity silicon powder (1 - 10 μm), silicon carbide powder (10 μm), diamond micropowder (200 μm), and dispersant (alcohol) into a beaker for ultrasonic wet dispersion. After 1 h of ultrasonic treatment, take out the beaker and put it into a vacuum drying oven. The drying temperature is 60 °C, and after 12 h of drying, put it into a tubular furnace and heat it to 850 °C at a rate of 10 °C / min, hold for 2 h, and then cool and take out to obtain a mixed powder. After sieving it 5 times, use a molybdenum cup for internal assembly to obtain a synthesis rod. Put the synthesis rod into a mold and pre-press it at 5 MPa on a hydraulic press. After external assembly, put it into an oven at 200 °C and keep it warm for 3 h to dry. After drying, conduct a high-temperature and high-pressure synthesis experiment with a six-sided press. Set the pressure to 5.5 GPa, the temperature to 1400 °C, and the holding and pressurizing time to 10 min. Then cool and depressurize. After the temperature in the cavity drops to room temperature, take it out to obtain a ceramic sample with internal assembly. Polish the sample to remove the molybdenum cup, remove impurities and clean it, and finally obtain the diamond / silicon carbide composite material.

[0022] The density of the diamond / silicon carbide composite material prepared in this embodiment is 3.09 g / cm3 , with a relative density of 98.6% and a thermal conductivity of 532 W / (m·K). Example

[0023] A diamond / silicon carbide composite material, in terms of mass percentage, is composed of the following raw materials: 10% high-purity silicon powder, 20% silicon carbide powder, and 70% diamond micropowder.

[0024] Weigh the raw materials according to the above ratios. Put high-purity silicon powder (1 - 10 μm), silicon carbide powder (10 μm), diamond micropowder (200 μm), and a dispersant (alcohol) into a beaker for ultrasonic wet dispersion. After 1 h of ultrasonic treatment, take out the beaker and put it into a vacuum drying oven. The drying temperature is 60 °C, and the drying time is 12 h. Then put it into a tube furnace and heat it up to 850 °C at a rate of 50 °C / min, hold for 2 h, and then cool and take out to obtain a mixed powder. After sieving it 5 times, use a molybdenum cup for internal assembly to obtain a synthesis rod. Put the synthesis rod into a mold and pre-press it at 5 MPa on a hydraulic press. After external assembly, put it into an oven at 120 °C and keep it warm for 3 h to dry. After drying, conduct a high-temperature and high-pressure synthesis experiment with a cubic press. Set the pressure to 5.5 GPa, the temperature to 1500 °C, and the holding time for pressure and temperature to 15 min. Then cool down and reduce the pressure. After the temperature in the cavity drops to room temperature, take it out to obtain a ceramic sample with internal assembly. Polish the sample to remove the molybdenum cup, remove impurities and clean it, and finally obtain the diamond / silicon carbide composite material.

[0025] The density of the diamond / silicon carbide composite material prepared in this example is 2.88 g / cm 3 , with a relative density of 96.8% and a thermal conductivity of 486 W / (m·K). Example

[0026] A diamond / silicon carbide composite material, in terms of mass percentage, is composed of the following raw materials: 15% high-purity silicon powder, 15% silicon carbide powder, and 70% diamond micropowder.

[0027] Weigh the raw materials according to the above ratio. Put high-purity silicon powder (1 - 10 μm), silicon carbide powder (10 μm), diamond micropowder (200 μm) and dispersant (alcohol) into a beaker for ultrasonic wet dispersion. After 1 hour of ultrasonic treatment, take out the beaker and put it into a vacuum drying oven. The drying temperature is 60 °C and the drying time is 12 hours. Then put it into a tubular furnace and heat it up to 850 °C at a rate of 10 °C / min, hold for 2 hours, and then cool and take out to obtain a mixed powder. After sieving it 5 times, use a molybdenum cup for internal assembly to obtain a synthetic rod. Put the synthetic rod into a mold and pre-press it on a hydraulic press at 5 MPa. After external assembly, put it into an oven at 200 °C and keep it warm for 3 hours to dry. After drying, conduct a high-temperature and high-pressure synthesis experiment with a cubic press. Set the pressure to 4.5 GPa, the temperature to 1500 °C, and the holding time for pressure and temperature to 10 minutes. Then cool down and reduce the pressure. After the temperature in the cavity drops to room temperature, take it out to obtain a ceramic sample with internal assembly. Polish the sample to remove the molybdenum cup, remove impurities and clean it, and finally obtain a diamond / silicon carbide composite material.

[0028] The density of the diamond / silicon carbide composite material prepared in this example is 3.01 g / cm 3 , the relative density is 97.9%, and the thermal conductivity is 504 W / (m·K).

[0029] Finally, it should be noted that the above are only preferred embodiments under high temperature and high pressure and are not used to limit the present invention.

Claims

1. An ultrasonic-assisted gradient high-pressure preparation method for diamond / silicon carbide composite materials, characterized in that, It includes the following steps: (1) Raw material selection: By mass fraction, select 5%-40% of high-purity silicon powder with a particle size of 1-100 μm, 5%-40% of silicon carbide powder with a particle size of 1-100 μm, 20%-90% of diamond micropowder with a particle size of 10-100 μm, and add a dispersant accounting for 20%-30% of the total mass of the powder; (2) Mixing: After mixing the raw materials with the dispersant, perform ultrasonic wet dispersion. The ultrasonic frequency is 20-50 kHz and the time is 60-90 min. Then dry it for 5-12 h under the conditions of a vacuum degree ≤ 10 Pa and a temperature of 40-80 °C to obtain a mixed powder; (3) Pre-sintering: Under the protection of an inert gas with a purity ≥ 99.999%, heat the mixed powder to 800-1000 °C at a heating rate of 2-20 °C / min, keep it warm for ≥ 2 h, sieve it through a 30-50 mesh sieve 3-5 times, and then assemble it into a synthesis rod in a molybdenum cup or a zirconium cup; (4) Pre-pressing and forming: Cold-press the synthesis rod at a pressure of 4-8 MPa, and after external assembly, keep it warm in an oven at 80-140 °C for ≥ 2 h; (5) High-temperature and high-pressure forming: Place the sample in a six-sided press, keep it warm for 5-10 min at a pressure of 3-5.5 GPa and a temperature of 1200-1500 °C, and complete sintering at a heating rate of 400-800 °C / min; (6) Grinding and polishing: Coarsely grind with a diamond grinding disc, coarsely polish with a cloth-lined polishing wheel, and finely polish with a silk cloth. The rotation speed of the polishing machine is 300-620 r / min, and finally obtain a diamond / silicon carbide composite material.

2. The preparation method according to claim 1, characterized in that, In the step (1): The diamond micropowder adopts a multi-stage grading design, in which the proportion of particles with a size of 200-300 μm is 50-70%, and the proportion of particles with a size of 50-100 μm is 30-50%.

3. The preparation method according to claim 1, characterized in that, In the step (2): The ultrasonic dispersion power density is 200-500 W / L, and the dispersant is anhydrous ethanol or deionized water.

4. The preparation method according to claim 1, characterized in that, In the step (3): The gradient heating is divided into two stages: when the temperature is below 800 °C, the heating rate ≤ 5 °C / min; when the temperature is above 800 °C, the heating rate ≥ 15 °C / min.

5. The preparation method according to claim 1, wherein, In the step (5): The pressure relief rate of the six-sided press is 10-50 MPa / min, and the cooling rate is 20-100 °C / min.

6. A diamond / silicon carbide composite material, characterized in that, Prepared by the method according to any one of claims 1-5, having a relative density ≥ 96%, a thermal conductivity ≥ 480 W / (m·K), a coefficient of thermal expansion ≤ 4.5×10⁻ 6 / K, an interfacial bonding strength ≥ 150 MPa, and applicable to the fields of aerospace, heat dissipation of electronic devices, high-temperature furnace lining materials, etc.

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