High-throughput preparation method of nearly-fully-compact refractory metal carbide high-entropy ceramic

Abstract

The invention discloses a high-throughput preparation method of nearly-fully-compact refractory metal carbide high-entropy ceramic, and belongs to the field of powder metallurgy. The method comprises the following steps: uniformly mixing a series of refractory metal carbide high-entropy ceramic raw materials; stacking a series of mixed raw materials with different components; and performing high-pressure sintering to obtain a multi-component series refractory metal carbide high-entropy ceramic compact block. According to the method, raw material layered stacking and high-pressure sintering strategies are combined, samples with different components are separated by using isolating membranes which do not participate in reaction, and a plurality of continuous independent sintering spaces which are distributed in the gravity direction and have consistent local sintering conditions are provided in the sintering process; by combining high-pressure sintering, the sintering temperature required by near full compactness (the compactness is greater than or equal to 98%) of the refractory metal carbide high-entropy ceramic is reduced, and the problems of high temperature, low compactness and low preparation efficiency of various components in preparation of the refractory metal carbide high-entropy ceramic are solved; the method is of great significance to rapid screening of refractory metal carbide high-entropy ceramic components capable of forming a single-phase solid solution and batch acquisition of performance data.

Description

Technical Field

[0001] The invention belongs to the technical field of powder metallurgy, and in particular relates to a high-throughput preparation method of nearly fully dense refractory metal carbide high-entropy ceramics. Background Art

[0002] Since the concept of "high entropy" was proposed in 2004, high entropy materials have rapidly received a lot of attention and research. The four core effects of high entropy materials: high entropy effect in thermodynamics, lattice distortion effect in structure, hysteresis diffusion effect in kinetics, and cocktail effect in performance, have enabled the design of materials to break through the limitations of primitives in traditional material design and greatly expanded the composition and performance space of materials. The research scope of high entropy has gradually expanded from the initial alloys to the field of ceramics. For example, high entropy carbides, high entropy oxides, high entropy borides, high entropy nitrides, and high entropy silicides have all been successfully synthesized. Studies have shown that refractory metal carbide high entropy ceramics have better room temperature and high temperature mechanical properties than single-element carbide ceramics, and are expected to meet the service requirements of extreme environments such as key components of hypersonic aircraft and nuclear energy.

[0003] Similar to single-component carbide ceramics, refractory metal carbide ceramics are generally prepared by powder metallurgy. However, the extremely high melting point of refractory metal carbides and the kinetic hysteresis diffusion effect make it difficult to densify refractory metal carbide high-entropy ceramics. The sintering temperature is still higher than 2000℃ under the condition of sintering pressure of 30-50MPa. The excessively high sintering temperature causes a large number of closed pores to be generated in the prepared samples, making it difficult to obtain nearly fully dense refractory metal carbide high-entropy ceramics. In addition, the number of quaternary, pentacyclic and hexacyclic equimolar ratio high-entropy ceramics that can be composed of 9 refractory metal carbide single components is 126, 126 and 84 respectively. Considering the situation of non-equimolar ratio of components, the number of combinations that can form refractory metal carbide high-entropy materials will reach an astronomical number. Faced with such a huge component exploration space, the traditional trial and error method is difficult to cope with, which greatly limits the rapid design, screening, preparation and application of high-entropy ceramic materials with high comprehensive mechanical properties. Therefore, from the perspective of rapid and accurate composition design and performance control of high-entropy ceramics, it is urgent to develop methods for preparing dense refractory metal carbide high-entropy ceramics at low temperatures and with high throughput. By developing high-throughput parallel experimental methods and combining them with high-pressure sintering strategies, a large number of refractory metal carbide high-entropy ceramic bulk samples can be obtained in a short period of time. Assisted by high-throughput characterization tests, the research and development efficiency of high-entropy ceramics can be greatly improved, providing key new technologies for the rapid design and preparation of refractory metal carbide high-entropy ceramics with high comprehensive mechanical properties. Summary of the invention

[0004] The present invention provides a high-throughput preparation method of nearly fully dense refractory metal carbide high-entropy ceramics, which can realize rapid and accurate composition design and performance regulation of high-entropy ceramics, significantly improve research and development efficiency, and further promote the practical application of high-entropy ceramic materials.

[0005] To achieve the above object, the present invention adopts the following technical solution:

[0006] (1) Raw material mixing and multi-layer stacking: According to the chemical composition of the target refractory metal carbide high entropy ceramic, different raw materials are uniformly mixed in a certain proportion to obtain a series of mixed powder raw materials with different components. Multiple groups (N groups) of mixed raw materials with different components are loaded into a graphite mold along the direction of gravity and pre-pressed, and an isolation film is laid between each two adjacent groups of mixed powders to form a multi-layer structure of isolation film-composite powder raw material 1-isolation film-composite powder raw material 2-isolation film-...-isolation film-composite powder raw material N-isolation film in the direction of gravity;

[0007] (2) Sintering and densification of multi-component series samples: Place a graphite mold containing multiple layers of mixed powder raw materials into a sintering furnace, set the sintering process parameters according to the characteristics of the desired sintered ceramic, and after sintering, cool to room temperature and demold to obtain a multi-component series of refractory metal carbide high-entropy ceramic blocks with a certain thickness. Separate the multi-component series of high-entropy ceramic samples along the interlayer isolation membrane to obtain refractory metal carbide high-entropy ceramic blocks of different compositions, which can be polished and then subjected to a series of tests and characterizations.

[0008] Furthermore, the refractory metal carbide raw material in step 1 is MeC x , wherein the refractory metal Me is Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, and x is between 0.5 and 1; each group of mixed powder raw materials should contain four or more refractory metal carbide raw materials, and the molar content of each raw material is between 5 and 35%; the number of groups of samples with different components N is ≥ 5; the pre-pressing pressure of the mixed powder raw materials is between 50 and 150 MPa; the isolation membrane includes carbon paper, carbon cloth, and carbon paper and carbon cloth with boron nitride sprayed on the surface.

[0009] Furthermore, the sintering furnace includes a spark plasma sintering furnace and a hot pressing sintering furnace; the sintering process parameters are determined according to the melting point of the raw materials and the target refractory metal carbide high entropy ceramics: the absolute pressure value of the gas in the furnace during sintering is ≤10Pa, the sintering temperature is between 1600-2200°C, the insulation time is 1-10min, and the sintering pressure is 60-150MPa; the thickness of each layer of the composite powder raw material after sintering and densification is between 20μm and 5mm.

[0010] Beneficial technical effects of the present invention:

[0011] (1) During the sintering process, the isolation membrane between each group of samples can effectively avoid the mutual diffusion of components between blocks of different target components. That is, the isolation membrane is used to separate multiple continuous and independent sintering spaces with consistent local sintering conditions along the gravity direction, ensuring the controllable composition of the target block.

[0012] (2) The high-pressure sintering used in the present invention can reduce the temperature required for the near-full densification of refractory metal carbide high-entropy ceramics. Combined with a multilayer stacking strategy, high-throughput preparation of near-fully dense refractory metal carbide high-entropy ceramic blocks can be achieved.

[0013] (3) The present invention helps to accelerate the rapid screening of components with the ability to form single-phase solid solutions and the design and preparation of high-entropy materials with high comprehensive mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic diagram of the sintering of a multi-component series of high-entropy ceramic samples designed for the present invention and a scanning electron microscope image of the cross-section of a high-entropy ceramic block prepared by high-throughput.

[0015] Figure 2 These are cross-sectional microstructures of 15 refractory metal carbide high-entropy ceramics prepared in Example 1. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail in the following embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0017] On the contrary, the present invention covers any substitution, modification, equivalent method and scheme made on the essence and scope of the present invention as defined by the claims. Further, in order to make the public have a better understanding of the present invention, some specific details are described in detail in the detailed description of the present invention below. Those skilled in the art can fully understand the present invention without the description of these details.

[0018] Example 1

[0019] Fifteen kinds of refractory metal carbide high entropy ceramics with different components were designed, and the target compositions were: (TiZrHfNb)C, (TiZrNbTa)C, (TiZrTaMo)C, (TiHfVTa)C, (HfVNbTa)C, (TiZrHfNbTa)C, (TiZrHfTaMo)C, (TiZrHfTaW)C, (TiZrVNbTa)C, (TiZrNbTaMo)C, (TiHfVNbTa)C, (TiHfNbTaMo)C, (TiHfNbTaW)C, (VNbTaMoW)C, and (TiZrHfNbTaMo)C. According to the target composition, different kinds of commercial carbide powders (TiC (purity 99.9wt.%, ≤1μm), ZrC (purity 99.9wt.%, 1μm), HfC (purity 99wt.%, ≤0.8μm), VC (purity 99wt.%, ≤3μm), NbC (purity 99wt.%, 2-4μm), TaC (purity 99wt.%, ≤1μm), Cr3C2 (purity 99wt.%, ≤1μm), Mo2C (purity 99.5wt.%, 1-3μm), WC (purity 99.9wt.%, ≤0.3μm)) were mixed by ball milling. The ball mill and grinding balls used were made of WC, the ball-to-material mass ratio was 10:1, the ball mill speed was 564r / min, and the ball milling time was 6h. The uniformly mixed raw materials were loaded into a graphite mold (mold diameter was 20 mm), and a layer of carbon paper was laid between every two mixed raw materials as an isolation film, forming a multilayer structure of isolation film-mixed powder raw material 1-isolation film-mixed powder raw material 2-isolation film-...-isolation film-mixed powder raw material 15-isolation film in the direction of gravity. The loading weights of the above 15 groups of mixed powders were 1.01g, 1.04g, 1.09g, 1.23g, 1.30g, 1.16g, 1.20g, 1.34g, 0.99g, 1.06g, 1.17g, 1.24g, 1.39g, 1.13g and 1.16g, respectively. The pre-pressing pressure of the mixed powder was 100MPa. Subsequently, the mold containing 15 different mixed powder raw materials was placed in a spark plasma sintering furnace for sintering and densification. The sintering temperature, pressure and holding time were 2000℃, 100MPa and 1min respectively. After sintering, 15 ceramic blocks with a thickness of about 400μm were obtained, and the density was ≥98%. The X-ray diffraction (XRD) results showed that the 15 ceramic blocks prepared were all typical single-phase face-centered cubic structures of refractory metal carbide high-entropy ceramics. The prepared blocks were high-entropy ceramics containing quaternary, pentacyclic and hexacyclic refractory metal carbides in equal molar ratios.

[0020] Example 2

[0021] Embodiment 2 is substantially the same as Embodiment 1, except that:

[0022] A total of five different groups of refractory metal carbide high entropy ceramic components were designed, with target compositions of (NbTaMoW)C, (Ti 0.25 NbTaMoW)C、(Ti 0.5 NbTaMoW)C、(Ti 0.75 NbTaMoW)C, (TiNbTaMoW)C. Different kinds of commercial carbide powders (TiC (purity 99.9wt.%, ≤1μm), NbC (purity 99wt.%, 2-4μm), TaC (purity 99wt.%, ≤1μm), Mo2C (purity 99.5wt.%, 1-3μm), WC (purity 99.9wt.%, ≤0.3μm)) were mixed by ball milling according to the target composition, and the mixing parameters were consistent with those in Example 1. The difference from Example 1 is that the isolation membrane between different mixed powder raw materials is replaced by carbon cloth from carbon paper, and the pre-pressing pressure of the mixed powder is adjusted from 100MPa to 50Mpa. The loading masses of the above five groups of mixed powders are 10.81g, 10.49g, 10.18g, 9.93g and 9.66g respectively. The sintering furnace is replaced by a spark plasma sintering furnace with a hot pressing sintering furnace. A graphite mold containing five different refractory metal carbide components was placed in a sintering furnace, and the sintering temperature, pressure and holding time were 1650℃, 100MPa and 3min respectively. After sintering, five ceramic blocks with a thickness of about 3mm were obtained, and the density was ≥99.5%. The XRD test results showed that the five prepared ceramic blocks were all single-phase face-centered cubic structures. The prepared blocks are high-entropy ceramics containing quaternary, pentad equimolar ratios and pentad non-equimolar ratios of refractory metal carbides.

[0023] Example 3

[0024] Embodiment 3 is substantially the same as Embodiment 2, except that:

[0025] A total of 10 groups of different refractory metal carbide high-entropy ceramic components were designed, and the target compositions were: (TiZrNbCr)C, (TiZrTaCr)C, (TiVNbCr)C, (TiNbTaCr)C, (VNbTaCr)C, (TiZrNbTaCr)C, (TiZrTaCrMo)C, (TiVNbTaCr)C, (TiVTaCrMo)C, and (VNbCrMoW)C. According to the target composition, different types of commercial carbide powders (TiC (purity 99.9wt.%, ≤1μm), ZrC (purity 99.9wt.%, 1μm), VC (purity 99wt.%, ≤3μm), NbC (purity 99wt.%, 2-4μm), TaC (purity 99wt.%, ≤1μm), Cr3C2 (purity 99wt.%, ≤1μm), Mo2C (purity 99.5wt.%, 1-3μm), WC (purity 99.9wt.%, ≤0.3μm)) were mixed by ball milling, and the mixing parameters were consistent with those in Example 2. The difference from Example 2 is that the isolation membrane between each two layers of mixed raw materials is replaced by carbon cloth with carbon paper sprayed with BN, the pre-pressing pressure of the mixed powder is adjusted from 50MPa to 150MPa, and the loading mass of the above 10 groups of mixed powders is 2.63g, 3.35g, 2.56g, 3.51g, 3.64g, 3.30g, 3.42g, 3.30g, 3.44g and 4.21g respectively. The sintering temperature, pressure and holding time are 1850℃, 60MPa and 3min respectively. After sintering, 10 kinds of ceramic blocks with a thickness of about 1.3mm are obtained, and the density is ≥99.5%. The XRD test results show that the 10 kinds of ceramic blocks prepared are all single-phase refractory metal carbide high entropy ceramics.

Claims

1. A high-throughput preparation method for nearly fully dense refractory metal carbide high-entropy ceramics, characterized in that: The steps include: (1) Raw material mixing and multi-layer stacking: Different raw materials are uniformly mixed according to the chemical composition of the target refractory metal carbide high entropy ceramic to obtain a series of mixed powder raw materials with different components; N groups of mixed raw materials with different components are loaded into a graphite mold along the direction of gravity and pre-pressed, and an isolation film is laid between each two adjacent groups of mixed powders to form a multi-layer structure of isolation film-composite powder raw material 1-isolation film-composite powder raw material 2-isolation film-...-isolation film-composite powder raw material N-isolation film in the direction of gravity; (2) Sintering and densification of multi-component series samples: Place a graphite mold filled with multiple layers of mixed powder raw materials into a sintering furnace. After sintering, cool to room temperature and demold to obtain a multi-component series of refractory metal carbide high-entropy ceramic blocks; separate the multi-component series of high-entropy ceramic samples along the interlayer isolation membrane to obtain refractory metal carbide high-entropy ceramic blocks with different compositions.

2. The preparation method according to claim 1, characterized in that: The refractory metal carbide raw material is MeC x , wherein the refractory metal Me is Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, and x is between 0.5 and 1; each group of mixed powder raw materials should contain more than four refractory metal carbide raw materials, and the molar content of each raw material is between 5 and 35%; the number of groups of samples with different components N is ≥ 5; the pre-pressing pressure of the mixed powder raw materials is between 50 and 150 MPa; the isolation membrane includes carbon paper, carbon cloth, carbon paper with boron nitride sprayed on the surface, or carbon cloth with boron nitride sprayed on the surface.

3. The preparation method according to claim 1, characterized in that: The sintering furnace includes a spark plasma sintering furnace or a hot pressing sintering furnace; during sintering, the absolute pressure value of the gas in the furnace is ≤10Pa, the sintering temperature is between 1600-2200°C, the insulation time is 1-10min, and the sintering pressure is 60-150MPa; the thickness of each layer of the composite powder raw material after sintering and densification is between 20μm and 5mm.

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