Method for preparing high-toughness wave-absorbing integrated SiC / Si3N4 composite ceramic in short period

Abstract

The invention discloses a method for preparing wave-absorbing integrated SiC / Si3N4 composite ceramic with high strength and toughness in a short period. Silicon nitride, silicon carbide, a sintering aid and other powder are mixed and dispersed for a short time through high-strength mechanical vibration, and the high-strength and high-toughness wave-absorbing composite ceramic is prepared after direct sintering. According to the preparation process, the preparation steps of ball milling, drying, sieving and the like are avoided, the preparation process period of the SiC / Si3N4 composite ceramic can be shortened from 1 week to 1 day, and the labor intensity is reduced; according to the preparation process, an organic solvent and a grinding medium do not need to be introduced, and pollution to samples and the environment is avoided; more importantly, the preparation process can effectively disperse the nano-powder and the whiskers, avoids the damage of a grinding medium to the powder such as particles and the whiskers, and enhances the strength and toughness of the ceramic material. The bending strength of the prepared SiC / Si3N4 composite ceramic can reach up to 1007 MPa, the fracture toughness reaches 11.63 MPa.m < 1 / 2 >, the minimum reflection loss of electromagnetic waves is-27 dB, and the wave absorbing bandwidth is 2.28 GHz.

Description

Technical Field

[0001] This paper relates to a method for preparing high-strength, toughness and wave-absorbing integrated SiC / Si3N4 composite ceramics in a short period of time. Background Art

[0002] In the field of armor protection, ceramic materials such as alumina (Al2O3), silicon nitride (Si3N4), silicon carbide (SiC), and boron carbide (B4C) are widely used. With the development of armor protection technology, ballistic ceramic materials are developing in the direction of ballistic resistance, high strength and toughness, electromagnetic wave absorption, and rapid manufacturing. Si3N4 / SiC composite ceramics, as a potential electromagnetic wave absorbing ballistic ceramic material, have the following problems:

[0003] The preparation process is complex and the cycle is long: The traditional process takes a long time to prepare mixed powders. For example, wet ball milling takes 16 hours or even 3 days, and the overall cycle is up to 1 week. It is labor-intensive and inefficient.

[0004] Powder dispersion and damage issues: Grinding balls will destroy reinforcing materials such as whiskers, reducing the mechanical properties of composite ceramics; nanoparticles, whiskers and other powders have poor dispersion effects and are prone to agglomeration, causing ceramics to easily break or pulverize when impacted, limiting their application in continuous shooting scenarios.

[0005] Among the existing preparation processes, CN114591086A discloses a nanopowder-modified silicon carbide-boron carbide composite ceramic and its preparation method. Silicon carbide-boron carbide composite ceramics are made from micro / nano silicon carbide, boron carbide, zirconium oxide, and graphene powders, and are prepared through processes such as powder mixing, spray granulation, pressure molding, and sintering. To achieve the dispersion of nanoceramic powder and graphene powder, a two-stage dispersion process is used, and the ball milling time alone exceeds 16 hours. The toughness of the prepared ceramic is only 5.5 MPa·m 1 / 2 , and the prepared silicon carbide-boron carbide composite ceramics do not have electromagnetic wave absorption properties.

[0006] CN119430885A discloses a wave-transmitting bulletproof ceramic material and its preparation method. The composite ceramic is made from powders such as aluminum oxide, silicon nitride, magnesium carbonate powder, and lanthanum oxide through a process of stirring, grinding, spray granulation, dry pressing, and high-temperature sintering. The ceramic preparation process involves multiple steps and a long cycle, especially during the powder preparation process. The strength of the composite ceramic is less than 700 MPa, and the fracture toughness is less than 7 MPa·m 1 / 2 , and does not have electromagnetic wave absorption performance.

[0007] The paper "Lei Z, et al. Dense Si3N4 / SiC composite ceramics with enhanced mechanical and electromagnetic absorption using micro-sized powders via spark plasma interfering [J]. Ceramics International, doi.org / 10.1016 / j.ceramint.2025.03.250" discloses a method for preparing Si3N4 / SiC composite ceramics. The method involves mixing Si3N4 and SiC powders using wet ball milling (24 hours), drying (10 hours), sieving, and then hot-pressing. The resulting composite ceramic material exhibits a fracture toughness of less than 6.6 MPa·m 1 / 2 The paper "Quan L, et al. Electromagnetic wave absorption properties of hot-pressed Si3N4-SiC ceramic nanocomposites [J]. International Journal of Applied Ceramic Technology, 2023, 1-12" describes a method for preparing Si3N4 / SiC nanocomposites. To disperse the nano-SiC particles, the method involves mixing the nanopowders using wet ball milling (for three days), drying, sieving, and then hot-pressing and sintering. The resulting Si3N4 / SiC nanocomposites exhibit a flexural strength of less than 600 MPa.

[0008] Based on the above analysis, existing technologies for preparing SiC / Si3N4 composite ceramics require multiple steps. In particular, the wet ball milling process has a long cycle time, poor dispersion of nanopowders or whiskers, and damage to the nanopowders and whiskers, resulting in reduced mechanical properties and electromagnetic wave loss capacity of the composite ceramics. Therefore, those skilled in the art urgently need to provide a method for preparing high-strength, high-toughness, integrated electromagnetic wave absorption SiC / Si3N4 composite ceramics in a short cycle time. Summary of the Invention

[0009] The present invention aims to address the deficiencies of the above-mentioned prior art by providing a short-cycle preparation process. This process method does not require wet grinding, thereby avoiding the subsequent drying and screening processes and reducing damage to the raw material morphology. This ceramic preparation method reduces the ceramic material preparation cycle and labor intensity, and improves the preparation efficiency of ceramic materials. The ceramic powder is evenly dispersed, and the mechanical properties and electromagnetic wave absorption properties of Si3N4 / SiC composite ceramics are improved. The specific technical solution is as follows:

[0010] A method for preparing high-strength, tough, and wave-absorbing integrated SiC / Si3N4 composite ceramics in a short period of time comprises the following steps:

[0011] S01. Weighing and mixing of powders:

[0012] Weigh silicon nitride, silicon carbide, and sintering aid according to the set mass fraction; and disperse the mixture of silicon nitride, silicon carbide, and sintering aid using high-intensity mechanical vibration.

[0013] S02. Sintering of composite ceramics:

[0014] The uniformly dispersed composite ceramic powder is sintered.

[0015] In order to obtain a good mixing effect without wet grinding, in step S01, the size and morphology characteristics of silicon nitride and silicon carbide are controlled;

[0016] Silicon nitride is in particle form with a size ranging from 0.1 to 5.0 μm, and silicon carbide is in particle form with a size ranging from 30 nm to 5.0 μm.

[0017] Alternatively, the silicon nitride is in the form of particles with a size ranging from 0.1 to 5.0 μm, and the silicon carbide is in the form of whiskers with a whisker diameter ranging from 0.1 to 10 μm and a length ranging from 10 to 100 μm;

[0018] Alternatively, silicon nitride is in the form of particles with a size in the range of 0.1-5.0 μm, and silicon carbide is in the form of a mixture of particles and whiskers, wherein the particle size is in the range of 30 nm-5.0 μm, the whisker diameter is 0.1-10 μm, and the length is 10-100 μm.

[0019] In order to further improve the bonding strength during sintering, the sintering aid in step S01 is one or a mixture of Y2O3, Al2O3, and MgO, and the particle size is in the range of 0.1-5.0 μm.

[0020] In order to ensure the uniformity of dispersion and not destroy the morphological characteristics of the powder, in step S01, the high-intensity mechanical vibration is a dry mechanical vibration without grinding media, wherein the mechanical vibration frequency is 55-65 Hz, the mixing acceleration is 30-80 g, and the time is 1-60 min.

[0021] Preferably, the sintering method in S02 is hot pressing, gas pressure sintering, or spark plasma sintering. This solution is applicable to various sintering processes. The sintering temperature is 1700-1900°C, the sintering time is 15-120 minutes, and the sintering pressure is 5-50 MPa. The specific parameters are selected to adapt to the size of the product to be prepared and the sintering environment.

[0022] Preferably, the silicon nitride content is 40-90 wt.%, the silicon carbide content is 10-40 wt.%, and the sintering aid content is 2-20 wt.%. By adjusting the ratio of various raw materials, the mechanical properties and wave absorption capacity of the final product can be adjusted.

[0023] Beneficial effects:

[0024] This solution breaks through the conventional wisdom of existing technologies that rely on wet grinding or ball milling. By precisely controlling particle size and morphology and employing high-intensity mechanical vibration, it effectively breaks down the bonds between raw material particles. This innovation not only significantly shortens the material preparation cycle and reduces the need for manual intervention, but also, by eliminating the introduction of any non-final components, it fundamentally addresses the contamination issue during raw material preparation, limiting potential contamination to the transportation stage.

[0025] Compared with the existing preparation process, the process proposed in this application has significant advantages:

[0026] First, the preparation cycle is shorter, and there is almost no damage to the original form of nanopowders or whiskers. Since there is no need to use grinding balls, the damage of grinding media to powders such as ceramic whiskers is avoided, thereby effectively improving the strength and fracture toughness of ceramic materials, and better retaining the mechanical properties and electromagnetic wave absorption properties of composite ceramics.

[0027] Secondly, high-intensity mechanical vibration can more evenly disperse ceramic powders (especially nano-ceramic powders), reducing ceramic defects caused by uneven particle dispersion. Ultimately, by combining the performance advantages of silicon carbide and silicon nitride, a high-quality, radar-absorbing, ballistic-resistant ceramic material that can be quickly produced was successfully produced. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Ceramic preparation process;

[0029] Figure 2 SEM images of Si3N4 and nano-SiC ceramic powders after high-intensity mechanical vibration mixing;

[0030] Figure 3 SEM image of Si3N4 and SiC whiskers after mixing under high-intensity mechanical vibration;

[0031] Figure 4 Photo of the prepared SiC / Si3N4 composite ceramic material. DETAILED DESCRIPTION

[0032] In order to deepen the understanding of the present invention, the present invention will be further described in detail below with reference to embodiments and drawings. The embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0033] Example 1

[0034] Figure 1 This is a ceramic preparation process flow chart. Si3N4 / SiC microwave-absorbing composite ceramics are prepared using silicon carbide nanopowder, silicon nitride submicron powder, aluminum oxide, and yttrium oxide powders as raw materials. The mass fractions of silicon nitride, silicon carbide, aluminum oxide, and yttrium oxide powders are 61wt%, 30wt%, 3wt%, and 6wt%, respectively. The particle size D50 of the silicon nitride submicron powder is 0.7μm, and the particle size of the silicon carbide nanopowder is 60nm. The specific preparation method is as follows:

[0035] Step 1) Weigh silicon nitride submicron powder, silicon carbide nanopowder, aluminum oxide and yttrium oxide ceramic powder according to the above proportions, and place the ceramic powder into a sample tank;

[0036] Step 2) The sample jar containing the ceramic powder was subjected to high-intensity mechanical vibration mixing for 15 minutes, a mixing acceleration of 75g, and a vibration frequency of 60Hz. Figure 2 This is a scanning electron microscope image of the mixed powder after dispersion. It can be seen from the image that SiC nanoparticles are evenly dispersed in the Si3N4 ceramic particles.

[0037] Step 3) The dispersed powder was sintered in a discharge plasma furnace at a sintering temperature of 1750°C, a heating rate of 300°C / min, a holding time of 15 min, a pressure of 30 MPa, and a nitrogen atmosphere.

[0038] The cycle of the SiC / Si3N4 nanocomposite ceramic prepared in this embodiment is less than 3 hours. After testing, the density of the SiC / Si3N4 nanocomposite ceramic prepared in this embodiment is 3.23g / cm 3 , the relative density reaches 97.9%, and the fracture toughness is 9.13MPa·m 1 / 2 , the loss tangent exceeds 0.15, the minimum reflection loss of electromagnetic waves at 15GHz is -27dB, and the absorption bandwidth in the Ku band is 2.28GHz.

[0039] Example 2:

[0040] Si3N4 / SiC microwave-absorbing composite ceramics were prepared using silicon carbide whiskers, submicron silicon nitride powder, aluminum oxide, and yttrium oxide powders as raw materials. The mass fractions of silicon nitride, silicon carbide, aluminum oxide, and yttrium oxide powders were 61wt%, 30wt%, 3wt%, and 6wt%, respectively. The particle size of the submicron silicon nitride powder was D50 = 0.7μm, and the silicon carbide whisker specifications (aspect ratio) were 10-80. The specific preparation method is as follows:

[0041] Step 1) Weigh silicon nitride submicron powder, silicon carbide whiskers, aluminum oxide, and yttrium oxide powder according to the above proportions, and place the ceramic powder into a sample container;

[0042] Step 2) The sample jar containing the ceramic powder was subjected to high-intensity mechanical vibration mixing for 30 minutes, a mixing acceleration of 70g, and a vibration frequency of 60Hz. Figure 2 This is a scanning electron microscope image of the mixed powder after dispersion. It can be seen from the image that the SiC whiskers are evenly dispersed in the Si3N4 ceramic particles, and the whiskers are less damaged, and can maintain the original state of the whiskers, which is beneficial to enhancing the mechanical properties of the composite ceramics.

[0043] Step 3) The dispersed powder was sintered in a discharge plasma furnace at a sintering temperature of 1750°C, a heating rate of 300°C / min, a holding time of 15 min, a pressure of 30 MPa, and a nitrogen atmosphere.

[0044] The cycle of the whisker-reinforced SiC / Si3N4 composite ceramic prepared in this embodiment is less than 3 hours. After testing, the density of the SiC / Si3N4 composite ceramic prepared in this embodiment is 3.19g / cm 3 , the relative density reaches 96.5%, the flexural strength reaches 1007MPa, and the fracture toughness reaches 11.63MPa·m 1 / 2 , the loss tangent exceeds 0.4, the minimum reflection loss of electromagnetic waves at 15GHz is -16dB, and the absorption bandwidth in the X-band is 1.94GHz.

[0045] Example 3:

[0046] Si3N4 / SiC microwave-absorbing composite ceramics were prepared using silicon carbide whiskers, submicron silicon nitride powder, aluminum oxide, and yttrium oxide powders as raw materials. The mass fractions of silicon nitride, silicon carbide, aluminum oxide, and yttrium oxide powders were 61wt%, 30wt%, 3wt%, and 6wt%, respectively. The particle size of the submicron silicon nitride powder was D50 = 0.7μm, and the silicon carbide whisker specifications (aspect ratio) ranged from 8 to 60. The specific preparation method is as follows:

[0047] Step 1) Weigh silicon nitride submicron powder, silicon carbide whiskers, aluminum oxide, and yttrium oxide powder according to the above proportions and place the powders into a sample container;

[0048] Step 2) The sample jar containing the ceramic powder was subjected to high-intensity mechanical vibration mixing for 30 minutes, a mixing acceleration of 70g, and a vibration frequency of 60Hz.

[0049] Step 3) The dispersed powder was sintered in a hot pressing sintering furnace at a sintering temperature of 1750°C, a heating rate of 16°C / min, a holding time of 1 hour, a pressure of 30 MPa, and a nitrogen atmosphere.

[0050] The cycle of the SiC / Si3N4 nanocomposite ceramic prepared in this embodiment is less than 10 hours. After testing, the density of the whisker-reinforced SiC / Si3N4 composite ceramic prepared in this embodiment is 3.09g / cm 3 , the relative density reaches 92.9%, the flexural strength reaches 873MPa, and the fracture toughness reaches 9.1MPa·m 1 / 2 , the loss tangent exceeds 0.4, the minimum reflection loss is -15dB, and the effective absorbing bandwidth in the Ku band is 2.81GHz.

[0051] It should be emphasized that the above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the same. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art will appreciate that the technical solutions of the present invention may be modified or replaced with equivalents without departing from the spirit and scope of the technical solutions of the present invention, and such modifications and replacements are intended to be encompassed within the scope of the claims of the present invention.

Claims

1. A method for preparing high-strength, tough, and wave-absorbing integrated SiC / Si3N4 composite ceramics in a short period of time, characterized in that: The following steps are involved: S01. Weighing and mixing of powders: Weigh silicon nitride, silicon carbide, and sintering aid according to the set mass fraction; and disperse the mixture of silicon nitride, silicon carbide, and sintering aid using high-intensity mechanical vibration. S02. Sintering of composite ceramics: The uniformly dispersed composite ceramic powder is sintered.

2. The method for preparing high-strength, toughness, and wave-absorbing integrated SiC / Si3N4 composite ceramics in a short period of time according to claim 1, characterized in that: In step S01, the size and morphology characteristics of silicon nitride and silicon carbide are controlled; Silicon nitride is in particle form with a size ranging from 0.1 to 5.0 μm, and silicon carbide is in particle form with a size ranging from 30 nm to 5.0 μm. Alternatively, the silicon nitride is in the form of particles with a size ranging from 0.1 to 5.0 μm, and the silicon carbide is in the form of whiskers with a whisker diameter ranging from 0.1 to 10 μm and a length ranging from 10 to 100 μm; Alternatively, silicon nitride is in the form of particles with a size in the range of 0.1-5.0 μm, and silicon carbide is in the form of a mixture of particles and whiskers, wherein the particle size is in the range of 30 nm-5.0 μm, the whisker diameter is 0.1-10 μm, and the length is 10-100 μm.

3. The method for preparing high-strength, toughness, and wave-absorbing integrated SiC / Si3N4 composite ceramics in a short period of time according to claim 1 or 2, characterized in that: The sintering aid in step S01 is one of Y2O3, Al2O3, and MgO, or a mixture thereof, and the particle size is in the range of 0.1-5.0 μm.

4. The method for preparing high-strength, toughness, and wave-absorbing integrated SiC / Si3N4 composite ceramics in a short period of time according to claim 3, characterized in that: In step S01 , the high-intensity mechanical vibration is a dry mechanical vibration without a grinding medium, wherein the mechanical vibration frequency is 55-65 Hz, the mixed acceleration is 30-80 g, and the time is 1-60 min.

5. The method for preparing high-strength, toughness, and wave-absorbing integrated SiC / Si3N4 composite ceramics in a short period of time according to claim 4, characterized in that: The sintering method in S02 is one of hot pressing sintering, gas pressure sintering and spark plasma sintering.

6. The method for preparing high-strength, toughness, and wave-absorbing integrated SiC / Si3N4 composite ceramics in a short period of time according to claim 5, characterized in that: The sintering holding temperature is 1700-1900°C, the sintering time is 15-120 minutes, and the sintering pressure is 5-50 MPa.

7. A method for preparing high-strength, toughness, and wave-absorbing integrated SiC / Si3N4 composite ceramics in a short period of time according to any one of claims 4 to 6, characterized in that: The silicon nitride content is 40-90 wt.%, the silicon carbide content is 10-40 wt.%, and the sintering aid content is 2-20 wt.%.

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