A high-entropy carbide ceramic with controllable porosity and a 3D printing preparation method thereof

Abstract

This invention discloses a high-entropy carbide ceramic with controllable porosity and its 3D printing preparation method, belonging to the field of high-entropy carbide ceramic powder preparation technology. Utilizing 3D printing technology, and leveraging the advantages of digital design and layer-by-layer manufacturing, this invention can prepare complex-structured high-entropy ceramics without molds. By constructing a precursor with controllable pore structure and introducing in-situ methane carbonization, the density is significantly improved while porosity can be controlled, providing a new approach for the preparation of porous thermal insulation materials. The innovative method employs a high-entropy alloy and phenolic resin composite powder combined with in-situ methane carbonization to directly generate a high-entropy carbide ceramic layer. In-situ carbonization eliminates powder transfer loss, significantly improving raw material utilization to 90%–95%, an improvement of approximately 10%–15% compared to existing technologies. This reduces preparation costs while avoiding process bottlenecks in powder preparation.

Description

Technical Field

[0001] This invention relates to the field of high-entropy carbide ceramic powder preparation technology, and in particular to a high-entropy carbide ceramic with controllable porosity and its 3D printing preparation method. Background Technology

[0002] Ultra-high temperature ceramics mainly include transition metal borides, carbides, and nitrides, with melting points above 3000℃. They are special-purpose ceramic materials with strong physical and chemical stability under high temperature and oxidizing atmospheres. These materials also have advantages such as high thermal conductivity, high strength, high hardness, and high modulus, and are expected to be used in the fabrication of hot-end structural components such as nose cones and wing leading edges of aircraft. Compared with traditional ultra-high temperature carbide ceramics containing only one or two transition metal elements, high-entropy carbide (HEC) ceramics, as a rapidly developing new type of material in recent years, have a single-phase solid solution structure. The multi-component characteristics of HEC ceramics allow for diversified designs through compositional control, thus exhibiting special properties different from traditional materials. Like high-entropy alloys, HEC ceramics have four core effects, which can be summarized as the thermodynamic high-entropy effect, the crystallographic lattice distortion effect, the kinetic hysteresis diffusion effect, and the performance "cocktail" effect. Transition metals, with their higher degree of disorder, exhibit large lattice distortions and possess better mechanical and thermal properties, making them promising for applications in extreme environments. As a result, they have attracted widespread attention from scholars both at home and abroad.

[0003] In the field of high-entropy carbide ceramics preparation, traditional technologies are encountering a series of thorny and urgent problems. Regarding the fabrication of complex structures, traditional manufacturing or mold-forming methods are inadequate. High-entropy carbide ceramics are characterized by high hardness, poor machinability, and a tendency to develop microcracks, while traditional methods heavily rely on molds. Mold design and manufacturing are not only costly and time-consuming, but their fixed structure also makes flexible adjustments difficult. This results in the inability of traditional methods to produce high-entropy carbide ceramics with arbitrarily complex structures such as porous and gradient structures when facing the urgent needs of the aerospace industry for complex internal flow channels and the optical device industry for precision irregular structures and integrated, lightweight products. This severely limits the application expansion of this material in these high-end fields. In densification, traditional sintering processes such as chemical vapor deposition and precursor impregnation pyrolysis have significant shortcomings. These processes are cumbersome, requiring multiple complex steps, which not only increases production costs and time but also results in materials with low density. High-entropy carbides inherently exhibit slow atomic diffusion and are difficult to sinter. Traditional processes struggle to overcome these inherent characteristics, failing to effectively improve material density and resulting in ceramics with suboptimal properties. Furthermore, cost control is a major challenge of traditional preparation techniques. Traditional methods rely on high-entropy carbide powders, whose synthesis is complex, requiring precise control of element ratios and reaction conditions. This leads to long preparation cycles and persistently high costs. Additionally, a certain percentage of raw material is lost during the preparation process, limiting overall raw material utilization and further increasing production costs. Summary of the Invention

[0004] The purpose of this invention is to provide a high-entropy carbide ceramic with controllable porosity and its 3D printing preparation method, solving the aforementioned problems. This invention utilizes 3D printing technology, leveraging the advantages of digital design and layer-by-layer manufacturing, to prepare complex high-entropy ceramics without molds. By constructing a precursor with controllable porosity and introducing in-situ methane carbonization, the density is significantly improved while porosity can be controlled, providing a new approach for the preparation of porous thermal insulation materials. The innovative method employs a high-entropy alloy and phenolic resin composite powder combined with in-situ methane carbonization to directly generate a high-entropy carbide ceramic layer. In-situ carbonization eliminates powder transfer loss, significantly improving raw material utilization to 90%–95%, an improvement of approximately 10%–15% compared to existing technologies. This reduces preparation costs while avoiding process bottlenecks in powder preparation.

[0005] To achieve the above objectives, this invention provides a 3D printing method for preparing high-entropy carbide ceramics with controllable porosity, comprising the following steps:

[0006] Step 1: Raw material preparation

[0007] The high-entropy alloy powder is selected from a five-element or larger atomic ratio system of Ti, Zr, Hf, Ta, Nb, and Mo (purity ≥99.5%), with particle size controlled at 5~50μm to ensure compatibility with 3D printing process. The high-entropy alloy powder and phenolic resin powder (particle size ≤30μm) are mixed at a mass ratio of (7:3) to (9:1) using a V-type vacuum mixer at a vacuum degree of 0.08~0.1MPa and a rotation speed of 60~80 rpm for 360~480 minutes to obtain a uniformly dispersed composite powder.

[0008] Step 2: SLS Selective Laser Sintering

[0009] Sintering is performed using a laser power of 50-100W, a scanning speed of 1000-2000mm / s, and a layer thickness of 0.05-0.1mm. A porous precursor structure is formed through layer-by-layer melting and deposition. The unmelted powder recovery rate after sintering can reach over 90%. Simultaneously, argon protection at 200°C for 2 hours is employed to ensure the removal of phenolic resin from the precursor and to prevent abnormal growth of the high-entropy alloy phase. The porosity formed in this stage provides nucleation sites for the subsequent carbonization reaction.

[0010] Step 3: In-situ carbonization treatment

[0011] The carbonization process employs a mixed atmosphere of CH4 (500~1000 sccm) and Ar2 (protective gas), at a pressure of 0.1~1 atm. The temperature gradient is set as follows: 5°C / min to 600°C (degassing stage), and 10°C / min to 1600~2000°C (carbon diffusion stage). The carbonization reaction of the TiZrHfNbTaC phase is carried out in the range of 1600~1800°C, and holding at this temperature for 4~8 hours can achieve gradient diffusion of carbon and alloying elements. By controlling the heating rate, a composite ceramic material with a continuous carbide ceramic phase (volume fraction 10~25%) can be formed while maintaining the high-entropy alloy single phase.

[0012] The present invention also provides a high-entropy carbide ceramic with controllable porosity prepared by the above preparation method, which is a multi-component high-entropy carbide.

[0013] In the process of preparing materials by mixing high-entropy alloys and phenolic resins, the porosity of the material can be controlled by adjusting the mixing ratio of the two. The porosity P is related to the mass mixing ratio ω of the phenolic resin, the density ρa of the phenolic resin, and the theoretical density ρb of the high-entropy alloy as follows:

[0014]

[0015] This formula allows for effective control of material porosity based on parameters such as the mass mixing ratio of phenolic resin and the porosity of the final material.

[0016] Therefore, the present invention has the following beneficial effects:

[0017] (1) Significant advantages in structural design and performance optimization: This invention, leveraging 3D printing technology, breaks through the limitations of traditional processes and can directly fabricate complex high-entropy carbide components with pore gradients, honeycomb structures, or functional gradients. It also provides a porosity calculation formula, based on parameters such as the mass mixing ratio of phenolic resin and referring to the porosity of the final material, thereby achieving effective control over the material's porosity. This not only achieves lightweighting (controllable porosity) but also optimizes compressive strength, achieving high specific strength, perfectly adapting to scenarios with stringent structural and performance requirements, such as high-temperature resistant components for aerospace applications.

[0018] (2) In-situ synthesis achieves a leap in material performance: Using phenolic resin pyrolysis carbon and methane carbon as dual carbon sources, and through laser selective sintering and high-temperature carbonization processes, alloying elements (Ti, Zr, Nb, Hf, Ta, Mo, etc.) react with carbon in situ to generate multi-component high-entropy carbides (such as MC type). This method significantly improves the hardness and high-temperature stability of the material, opening up a new path for improving material performance.

[0019] (3) Precise control ensures stable material quality: The 3D interconnected pores formed by the pyrolysis of phenolic resin create conditions for methane permeation. Combined with precise control of temperature and CH4 flow rate, a gradient distribution of carbonization depth and phase composition is achieved. At the same time, the volume expansion during the carbonization process is effectively buffered to avoid cracking and ensure stable and reliable material quality.

[0020] (4) High efficiency and alignment with green manufacturing concept: Near-net-shape characteristics significantly reduce subsequent machining steps, reducing material loss by 20-30% compared to traditional methods, and the powder recycling system further reduces raw material costs. It reduces machining energy consumption and waste emissions, which is highly in line with the development trend of green manufacturing.

[0021] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0022] Figure 1 The image shows an SEM image of the composite powder prepared in Example 1.

[0023] Figure 2 EDS image of the porous precursor prepared in Example 1;

[0024] Figure 3 EDS image of the high-entropy carbide ceramic prepared in Example 1;

[0025] Figure 4The images show the XRD patterns of materials prepared at different stages in Example 1, where a is the XRD pattern of the porous precursor and b is the XRD pattern of the high-entropy carbide ceramic.

[0026] Figure 5 The image shown is an EDS image of the high-entropy ceramic sample prepared in Comparative Example 1. Detailed Implementation

[0027] The technical solution of the present invention will be further described below through examples and embodiments.

[0028] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0029] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. These other embodiments are also covered within the scope of protection of this invention.

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below.

[0031] Example 1:

[0032] This embodiment provides a method for preparing (TiZrHfTaNb)C high-entropy carbide ceramics by 3D printing, and the preparation method is as follows:

[0033] Step 1: Raw material preparation

[0034] High-entropy alloy powders of TiZrHfTaNb with equiatomic ratios were selected, requiring a purity ≥99.5% and a particle size controlled between 5 and 50 μm to ensure compatibility with the 3D printing process. Phenolic resin powder (particle size ≤30 μm) was mixed at a mass ratio of 7:3 using a V-type vacuum mixer at a vacuum of 0.08 MPa and a rotation speed of 60 rpm for 360 minutes to obtain a uniformly dispersed composite powder. The SEM image of the composite powder is shown below. Figure 1 As shown, phenolic resin powder is uniformly distributed in TiZrHfTaNb high-entropy alloy powder.

[0035] Step 2: SLS Selective Laser Sintering

[0036] Sintering was performed using a 50W laser power, a scanning speed of 1000 mm / s, and a layer thickness of 0.05 mm to form a porous precursor through layer-by-layer melting and deposition. The unmelted powder recovery rate after sintering reached over 90%. Simultaneously, argon protection at 200°C for 2 hours was employed to ensure the removal of phenolic resin from the precursor and to prevent the abnormal growth of the high-entropy alloy phase. The porosity formed in this stage provides nucleation sites for the subsequent carbonization reaction. The EDS image of the porous precursor prepared in this step is shown below. Figure 2 As shown, the results indicate that the precursor has a porosity of 51.21% and the elements are relatively evenly distributed in the material, providing a basis for the next step of in-situ generation of high-entropy carbides.

[0037] Step 3 In-situ carbonization treatment

[0038] The carbonization process uses a mixed atmosphere of CH4 (500 sccm) and Ar2 (protective gas) at a pressure of 0.1 atm. The temperature gradient is set as follows: 5°C / min to 600°C (degassing stage), and 10°C / min to 1600°C (carbon diffusion stage). The carbonization reaction of the (TiZrHfNbTa)C phase is carried out in the range of 1600~1800°C, and holding at this temperature for 4 hours can achieve gradient diffusion of carbon and alloying elements. By controlling the heating rate, a continuous carbide ceramic phase (volume fraction 10~25%) can be formed while maintaining the high-entropy alloy single phase. The EDS image of the high-entropy carbide ceramic prepared in this step is shown below. Figure 3 As shown, the high-entropy alloy undergoes volume expansion during carburization, reducing the porosity from the original 51.21% (measured) to 18.23% (measured). This adjustment of porosity and uniform distribution of elements contribute to the stability of material properties.

[0039] = =53.33% (theoretical)

[0040] When TiZrHfNbTa is carbonized to (TiZrHfNbTa)C, the volume expands by about 20% to 30%. According to the formula, the porosity of the expanded material is about 28.13% to 34.54%. Due to the uncertainties in the experimental process, there is an error range of 2% to 10%, which is consistent with the experimental results.

[0041] XRD analysis was performed on the porous precursor prepared in step 2 and the high-entropy carbide ceramic prepared in step 3, respectively. The results are as follows: Figure 4 As shown, the results indicate that the high-entropy alloy with a single BCC structure in step 2 is transformed into a high-entropy carbide ceramic with a single FCC structure by in-situ carbonization in a methane atmosphere in step 3.

[0042] Example 2:

[0043] This embodiment provides a method for preparing (TiZrHfTaMo)C high-entropy carbide ceramics by 3D printing, and the preparation method is as follows:

[0044] Step 1: Raw material preparation

[0045] TiZrHfTaNbMo high-entropy alloy powder with an atomic ratio of ≥99.5% and a particle size controlled between 5 and 50 μm was selected to ensure compatibility with the 3D printing process. Phenolic resin powder (particle size ≤30 μm) was mixed at a mass ratio of 8:2 using a V-type vacuum mixer at a vacuum degree of 0.09 MPa and a rotation speed of 70 rpm for 410 minutes to obtain a uniformly dispersed composite powder.

[0046] Step 2: SLS Selective Laser Sintering

[0047] Sintering was performed using an 80W laser power, a scanning speed of 1500mm / s, and a layer thickness of 0.07mm. A porous precursor structure was formed through layer-by-layer melting and deposition. The unmelted powder recovery rate after sintering reached over 90%. Simultaneously, argon protection at 200°C for 2 hours was employed to ensure the removal of phenolic resin from the precursor and to prevent the abnormal growth of the high-entropy alloy phase. The porosity formed at this stage provides nucleation sites for the subsequent carbonization reaction.

[0048] Step 3 In-situ carbonization treatment

[0049] The carbonization process employs a mixed atmosphere of CH4 (800 sccm) and Ar2 (protective gas) at a pressure of 0.5 atm. The temperature gradient is set as follows: 5°C / min to 600°C (degassing stage), and 10°C / min to 1750°C (carbon diffusion stage). The carbonization reaction of the (TiZrHfNbMo)C phase is carried out in the range of 1600–1800°C, and a holding time of 4–8 hours can achieve gradient diffusion of carbon and alloying elements. By controlling the heating rate, a continuous high-entropy carbide ceramic phase (volume fraction 10–25%) can be formed while maintaining the high-entropy alloy single phase. According to the test, the porosity of the high-entropy carbide ceramic prepared in this embodiment is 9.21% (measured). When TiZrHfNbTa is carbonized to (TiZrHfNbTa)C, the volume expands by about 20%~30%. According to the formula, the porosity of the expanded material is about 4.82%~0%. Due to the uncertainties in the experimental process, there is an error range of 2%~10%, which is consistent with the experimental results. Compared with Example 1, the porosity has been controlled.

[0050] Example 3:

[0051] This embodiment provides a method for preparing (TiZrHfTaNbMo)C high-entropy carbide ceramics by 3D printing, and the preparation method is as follows:

[0052] Step 1: Raw material preparation

[0053] TiZrHfTaNbMo high-entropy alloy powder with an atomic ratio of ≥99.5% and a particle size controlled between 5 and 50 μm was selected to ensure compatibility with the 3D printing process. Phenolic resin powder (particle size ≤30 μm) was also selected. The mass ratio of the two was 9:1. The powder was mixed in a V-type vacuum mixer at a vacuum of 0.1 MPa and a rotation speed of 80 rpm for 480 minutes to obtain a uniformly dispersed composite powder.

[0054] Step 2: SLS Selective Laser Sintering

[0055] Sintering was performed using a 100W laser power, a scanning speed of 2000 mm / s, and a layer thickness of 0.1 mm. A porous precursor structure was formed through layer-by-layer melting and deposition. The unmelted powder recovery rate after sintering reached over 90%. Simultaneously, argon protection at 200°C for 2 hours was employed to ensure the removal of phenolic resin from the precursor and to prevent the abnormal growth of the high-entropy alloy phase. The porosity formed at this stage provides nucleation sites for the subsequent carbonization reaction.

[0056] Step 3 In-situ carbonization treatment

[0057] The carbonization process employs a mixed atmosphere of CH4 (1000 sccm) and Ar2 (protective gas) at a pressure of 1 atm. The temperature gradient is set as follows: 5°C / min to 600°C (degassing stage), and 10°C / min to 2000°C (carbon diffusion stage). The carbonization reaction of the (TiZrHfNbTaMo)C phase is carried out in the range of 1600–1800°C, and a holding time of 4–8 hours can achieve gradient diffusion of carbon and alloying elements. By controlling the heating rate, a continuous carbide ceramic phase (volume fraction 10–25%) can be formed while maintaining the high-entropy alloy single phase.

[0058] Comparative Example 1:

[0059] Step 1: Material Preparation

[0060] High-entropy carbide powder (Ti, Zr, Hf, Ta, Nb)C with a purity of not less than 99.5% (mass fraction) and a particle size of 1~5μm should be selected to ensure sintering activity. Argon gas with a purity of 99.9% (volume fraction) should be used as a protective atmosphere. Graphite molds with an inner diameter of 20~50mm should be selected according to the sample size. Before use, surface impurities should be removed by wiping with alcohol.

[0061] Step 2: Spark Plasma Sintering

[0062] The prepared high-entropy carbide powder is evenly filled into a clean graphite mold. The mold is gently vibrated to ensure the powder is compacted, and the filling height is controlled to ensure uniform powder distribution within the mold. The graphite mold containing the powder is then placed on the lower electrode of the spark plasma sintering (SPS) equipment. The mold position is adjusted to ensure good contact between the upper and lower electrodes and the mold. The equipment cavity is closed, and the vacuum pump is started to reduce the pressure inside the cavity to below 10⁻³ Pa to remove air. Argon gas is then introduced to atmospheric pressure, and the vacuuming and argon purging process is repeated 2-3 times to ensure a pure atmosphere inside the cavity. The heating rate is set to 50-100℃ / min, and the temperature is raised from room temperature to the sintering temperature, typically 1600-2000℃. Once the set sintering temperature is reached, a pressure of 10-50 MPa is applied through the equipment's hydraulic system to ensure uniform pressure distribution on the mold. The temperature is held at the set temperature and pressure for 5-30 minutes to allow the powder to fully sinter and densify. After the heat treatment is completed, heating is stopped, and the pressure is kept constant, allowing the sample to cool naturally to room temperature in an argon atmosphere. The cooling rate is approximately 50~100℃ / min. Once the chamber temperature has dropped to room temperature, the pressure is released, the chamber is opened, and the graphite mold is removed. The sintered high-entropy carbide ceramic sample is carefully removed from the mold, and any residual graphite powder on the sample surface is cleaned, completing the preparation process. The energy dispersive spectroscopy (EDS) spectrum of the high-entropy ceramic sample prepared in this comparative example is shown below. Figure 5 As shown, the material also has a certain particle structure. During the spark plasma sintering process, factors such as sintering temperature, pressure, holding time, as well as the particle size, purity, and loose density of the powder raw materials will affect the porosity. Therefore, the size, number, and distribution of pores are difficult to control precisely. At the same time, the introduction of O elements will have an adverse effect on the mechanical and physical properties of the material.

[0063] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for 3D printing high-entropy carbide ceramics with controllable porosity, characterized in that, A homogeneous mixed powder is obtained by mixing high-entropy alloy powder with phenolic resin powder in a multi-element equiatomic ratio system. The mixed powder is then melted and deposited layer by layer through SLS selective laser sintering to form a precursor with a controllable porous structure. The phenolic resin is then pyrolyzed. Subsequently, the porous precursor is subjected to in-situ carbonization treatment using a dual carbon source of carbon from pyrolyzed phenolic resin and carbon from methane. The controllable porous structure provides nucleation sites, enabling gradient diffusion of carbon elements and high-entropy alloy powder. This process yields a high-entropy carbide ceramic, which is a composite ceramic material with a high-entropy alloy single phase and a continuous carbide ceramic phase. The multi-element equiatomic ratio system is a five-element or greater equiatomic ratio system selected from Ti, Zr, Hf, Ta, Nb, and Mo; the particle size of the high-entropy alloy powder is 5~50μm; and the particle size of the phenolic resin powder is less than 30μm. The porosity of the high-entropy carbide ceramic is controlled by the mixing ratio of high-entropy alloy powder and phenolic resin powder, satisfying the following relationship: in, The porosity of high-entropy carbide ceramics, The mass mixing ratio of high-entropy alloy powder and phenolic resin powder. The density of phenolic resin. This represents the theoretical density of the high-entropy alloy. The mass ratio of high-entropy alloy powder to phenolic resin powder is (7:3) to (9:1). The in-situ carbonization treatment is carried out in a mixed atmosphere of CH4 and Ar2, at a pressure of 0.1~1 atm, with a temperature gradient, and includes the following stages: (1) Degassing stage: The temperature is increased from 5°C / min to 600°C; (2) Carbon diffusion stage: Increase to 1600~2000°C at 10°C / min and keep warm for 4~8 hours.

2. The 3D printing preparation method of high-entropy carbide ceramics with controllable porosity according to claim 1, characterized in that, In the high-entropy carbide ceramic, the volume fraction of the continuous carbide ceramic phase is 10-25%.

3. The 3D printing preparation method of high-entropy carbide ceramics with controllable porosity according to claim 1, characterized in that, The high-entropy alloy powder and the phenolic resin powder are mixed in a V-type vacuum mixer at a vacuum of 0.08~0.1MPa and a rotation speed of 60~80 rpm for 360~480 minutes to obtain a uniformly mixed powder.

4. The 3D printing preparation method of high-entropy carbide ceramics with controllable porosity according to claim 1, characterized in that, The SLS selective laser sintering process uses a laser power of 50~100W, a scanning speed of 1000~2000mm / s, and a layer thickness of 0.05~0.1mm to sinter a uniformly mixed powder. It is carried out under argon protection at 200°C for 2 hours, and a porous precursor structure is formed by layer-by-layer melting and stacking.

5. The 3D printing preparation method of a high-entropy carbide ceramic with controllable porosity according to claim 1, characterized in that, The flow rate of methane is 500~1000 sccm.

6. A high-entropy carbide ceramic with controllable porosity, characterized in that, The high-entropy carbide ceramic is prepared by the 3D printing method according to any one of claims 1-5.

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