CN112094121A - A kind of high-entropy MAX phase solid solution material in chalcogenide and its preparation method and application - Google Patents

Abstract

The invention discloses a high-entropy MAX phase solid solution material in a sulfur system, and a preparation method and application thereof. M position of the high-entropy MAX phase solid solution material in the sulfur system comprises any three or more than four combinations of transition metal elements of Ti, Zr, Hf, V, Nb and Ta, A position is sulfur element, and X position is carbon element. The preparation method comprises the following steps: ferrous sulfide is used as a high-temperature solid sulfur source, transition metal sulfide is obtained through a displacement reaction between a transition metal simple substance and the ferrous sulfide, and then the transition metal sulfide reacts with metal carbide to obtain the high-entropy MAX-phase solid solution material in the sulfur system. The ferrous sulfide sulfur source and the sulfur-containing intermediate product adopted by the invention are stable metal sulfides, so that the volatilization of elemental sulfur in the high-temperature preparation process is avoided, and the synthetic path of a target phase is favorably controlled; the obtained high-entropy MAX phase solid solution material in the sulfur system is expected to have good application prospect in the field of extreme environment structure materials such as nuclear power, high-speed rails and the like.

Description

A kind of high-entropy MAX phase solid solution material in chalcogenide and its preparation method and application

technical field

The invention relates to a MAX phase solid solution material, in particular to a high-entropy MAX phase solid solution material in a sulfur system, a preparation method and application thereof, and belongs to the technical field of ternary layered compound MAX phase materials.

Background technique

The MAX phase is a nano-layered ternary compound with diverse structures and properties, with hexagonal symmetry (P6 ₃ /mmc) and the general molecular formula of Mn ₊₁ AX _n . Among them, M is a metal of the early transition group, A is usually an element of the IIIA and IVA groups, X is a carbon or nitrogen element, and n is mostly 1-3 (MWBarsoum et al., Prog.Solid State Chem., 2000, 28, 201- 281). It is generally believed that the crystal structure of the MAX phase is composed of Mn _{+ 1Xn} nanostructured sublayers and A-site monoatomic layers alternately stacked. Among them, the Mn _{+ 1Xn} nanostructured sublayer is composed of covalently bonded M ₆ X octahedral layers with common edges, and X elements occupy the octahedral gaps composed of M elements. However, the interaction force between the A-site single atomic layer and the Mn ₊₁ X _n nanostructure sublayer is weak, and it is in a state similar to a metal bond. In the MAX phase crystal structure, the two adjacent Mn _{+1 Xn} sublayers are in twinning orientation, and the mirror surface is located on the sandwiched A-site single atomic layer (P.Eklundet al., Thin Solid Films, 2010, 518, 1851 -1878). Theoretical calculation predictions show that more than 600 MAX phases are thermodynamically stable, of which more than 70 pure MAX phases have been successfully synthesized (S. Aryal et al., Phys. Status Solidi B, 2014, 251, 1480-1497). The distribution of M-site, A-site and X-site elements of the MAX phase has been found so far, including 14 kinds of M-site elements, 17 kinds of A-site elements and 2 kinds of X-site elements. These MAX phases typically combine the light weight, high strength, oxidation resistance, creep resistance and good thermal stability of ceramics with the high electrical conductivity, high thermal conductivity, relative flexibility and excellent damage tolerance, high temperature plasticity and workability of metals (MWBarsoum et al., Prog. Solid State Chem., 2000, 28, 201-281); recent studies have also found that the MAX phase has low radiation activity and good material bonding properties (C. Wang et al., Nature Communications, 2019, 10, 622; X. Zhou et al., Carbon, 2016, 102: 106-115). Therefore, most of the current research on the application field of MAX phase mainly focuses on the direction of high-safety structural materials including high-temperature electrodes, high-speed rail pantographs, and nuclear fuel cladding tubes.

其中k_B为玻尔兹曼常数，x_i为i组分的摩尔分数。通常中熵陶瓷的组元需要三种不同的元素，高熵陶瓷的组元需要四种及以上不同的元素。目前，氧化物、碳化物、硼化物、氮化物、硅化物已经实现了中高熵化。MAX相具有丰富的化学多样性，通过M位、A位和X位可以获得双组元固溶的MAX相固溶体。目前已有研究者合成(Ti，Zr，Hf，Nb，Ta)₂AlC的高熵MAX相，然而A位为硫系的中高熵MAX相目前暂未有报道(W.Bao et al.，Scripta Mater.，2020，183，33-38)。Medium and high entropy ceramics is one of the current research hotspots. The principle of medium and high entropy ceramics is to obtain ceramic materials with high hardness, high strength, good fracture toughness and oxidation resistance by increasing the value of configuration entropy in the compound and reducing the Gibbs free energy of the system. Usually this configuration entropy can be expressed as

where k _B is the Boltzmann constant and x _i is the mole fraction of the i component. Generally, the components of medium-entropy ceramics require three different elements, and the components of high-entropy ceramics require four or more different elements. At present, oxides, carbides, borides, nitrides, and silicides have achieved medium and high entropy. The MAX phase has rich chemical diversity, and a two-component solid solution of the MAX phase can be obtained through the M-site, A-site and X-site. At present, researchers have synthesized the high-entropy MAX phase of (Ti, Zr, Hf, Nb, Ta) ₂ AlC, but the medium-high-entropy MAX phase of which the A site is a chalcogenide has not yet been reported (W. Bao et al., Scripta Mater., 2020, 183, 33-38).

Compared with the conventional A-site MAX phase with an approximate free metal aluminum layer, the sulfur in the chalcogenide MAX phase has a strong binding force with the M-site metal atoms. Therefore, for the same type of MAX phase, the MAX phase with sulfur at the A site has higher Young's modulus, shear modulus and hardness. (Y.L.Du et al., Phys.B-Condensed Matter., 2010, 405, 720-723) At the same time, the sulfur-containing MAX phase has better chemical stability and oxidation resistance (S.R.Kulkami et al., J.Alloy. Compd., 2009, 469, 395-400). It is of great significance to explore the synthesis of high-entropy MAX in sulfur-containing phase to further improve the physical and chemical properties of the MAX phase and expand its application.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to provide a high-entropy MAX phase solid solution material in a sulfur system and a preparation method thereof, so as to overcome the deficiencies in the prior art, solve the high temperature required for the synthesis of the high-entropy MAX phase in the sulfur system, and be volatile with the elemental sulfur source. Instability, it is difficult to synthesize the target phase of higher purity.

Another object of the present invention is to provide the application of the high-entropy MAX phase solid solution material in the sulfur system.

In order to realize the foregoing invention purpose, the technical scheme adopted in the present invention includes:

The embodiment of the present invention provides a high-entropy MAX phase solid solution material in a chalcogenide system, the M site of which includes any three (medium entropy) or more than four (high-entropy) transition metal elements Ti, Zr, Hf, V, Nb, and Ta. entropy), the A site is sulfur and the X site is carbon.

M_i包括Ti、Zr、Hf、V、Nb、Ta中的任意三种或者四种以上的组合，x_i为M_i组分在M位的摩尔常数，n为3～5，i指代第i个组分，取值为1～n的整数。In some embodiments, the chemical formula of the high-entropy MAX phase solid solution material in the chalcogenide is M ₂ SC, wherein

_Mi includes any three or a combination of more than four of Ti, Zr, Hf, V, Nb and Ta, _xi is the molar constant of the _Mi component at the M position, n is 3 to 5, and i refers to the first i components, which are integers ranging from 1 to n.

The embodiment of the present invention also provides a preparation method of a high-entropy MAX phase solid solution material in a sulfur system, comprising:

Provide ferrous sulfide as a high temperature solid sulfur source;

The mixture containing the ferrous sulfide, transition metal element and/or transition metal hydride and transition metal carbide is reacted at 1400 to 1800 ° C for 10 to 30 minutes to obtain the high entropy MAX phase solid solution material in the sulfur system, and its chemical formula is M ₂ SC, wherein M includes any three or a combination of four or more of Ti, Zr, Hf, V, Nb, and Ta.

In some embodiments, the preparation method specifically includes:

mixing ferrous sulfide, transition metal element and/or transition metal hydride and transition metal carbide according to the molar ratio of (1.0-1.2): (1.9-2.1): (0.8-1) to obtain a mixture;

Using a spark plasma sintering system, the mixture is heated to 1400-1800°C at a heating rate of 25-50°C/min, and the reaction is kept for 10-30 minutes, followed by post-treatment to obtain the sulfur-based medium high-entropy MAX phase solid solution material .

Further, the transition metal element includes any three or a combination of four or more of Ti, Zr, Hf, V, Nb, Ta, etc., but is not limited thereto.

Further, the transition metal carbide includes any three or a combination of four or more of TiC, ZrC, HfC, VC, NbC, TaC, etc., but is not limited thereto.

The embodiment of the present invention also provides the use of the high-entropy MAX phase solid solution material in the sulfur system in the field of preparing structural materials for extreme environments such as nuclear power and high-speed iron.

Compared with the prior art, the advantages of the present invention are at least as follows:

(1) The present invention uses ferrous sulfide as a high-temperature solid sulfur source, obtains transition metal sulfide through the replacement reaction between transition metal element and ferrous sulfide, and then combines with metal carbide to successfully obtain ternary and quaternary sulfur systems , five-element MAX phase solid solution material, the ferrous sulfide sulfur source and the sulfur-containing intermediate product used in the preparation method are both stable metal sulfides, which avoids the volatilization of elemental sulfur in the high-temperature preparation process, and is beneficial to control the synthesis of the target phase Path to reduce the pollution of volatile sulfur to experimental equipment and the environment. The method is simple and easy to implement, and combined with the pickling post-treatment process, a sulfur-based multi-component (high-entropy) MAX phase solid solution material with high purity can be obtained, which can be used as a reference for the design of the synthesis process of other non-aluminum-based multi-component MAX phase solid solution materials;

(2) The high-entropy MAX phase solid solution material obtained by the present invention is expected to have good application prospects in the field of extreme environmental structural materials such as nuclear power and high-speed rail.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments described in the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

Fig. 1 is the XRD pattern of the entropy MAX phase solid solution material in (Ti, Zr, Hf) ₂ SC prepared in Example 1 of the present invention;

2a-2e are SEM images of the entropy MAX phase solid solution material in (Ti, Zr, Hf) ₂ SC prepared in Example 1 of the present invention;

Fig. 3 is the XRD pattern of the (Ti, Zr, Hf, V) ₂ SC high-entropy MAX phase solid solution material prepared in Example 2 of the present invention;

4a-4f are SEM images of the (Ti, Zr, Hf, V) ₂ SC high-entropy MAX phase solid solution material prepared in Example 2 of the present invention;

Fig. 5 is the XRD pattern of the (Ti, Zr, Hf, V, Nb) ₂ SC high-entropy MAX phase solid solution material prepared in Example 3 of the present invention;

6a-6g are SEM images of the (Ti, Zr, Hf, V, Nb) ₂ SC high-entropy MAX phase solid solution material prepared in Example 3 of the present invention.

Detailed ways

In view of the defects of the prior art, the inventor of the present case has been able to propose the technical solution of the present invention through long-term research and a large amount of practice, which mainly uses ferrous sulfide as a high-temperature solid-state sulfur source, and mixes transition metal elemental substances (and/or or transition metal hydride) or metal carbide, high-entropy MAX phase solid solution material in sulfur system can be obtained under certain temperature conditions, and the obtained powder can be further improved by pickling the purity of the MAX phase. The technical solutions of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

An aspect of the present invention provides a high-entropy MAX phase solid solution material in a chalcogenide system where the M site includes any three or a combination of more than four transition metal elements Ti, Zr, Hf, V, Nb, Ta, etc., The A site is sulfur, and the X site is carbon. When the M site is composed of three elements, the MAX phase solid solution can meet the definition requirements of medium-entropy ceramics; when the M site is composed of four or more elements, the MAX phase solid solution can meet the definition requirements of high-entropy ceramics.

M_i包括Ti、Zr、Hf、V、Nb、Ta中的任意三种或者四种以上的组合，x_i为M_i组分在M位的摩尔常数，n为3～5，i指代第i个组分，取值为1～n的整数(如取值为1、2……n)。In some embodiments, the high-entropy MAX phase solid solution material in chalcogenide has the following general chemical formula M ₂ SC, wherein

_Mi includes any three or a combination of more than four of Ti, Zr, Hf, V, Nb and Ta, _xi is the molar constant of the _Mi component at the M position, n is 3 to 5, and i refers to the first i components, the value is an integer from 1 to n (eg, the value is 1, 2...n).

In some embodiments, the high-entropy MAX phase solid solution material in the chalcogenide has a hexagonal layered structure, and the space group is P63/mmc.

In some embodiments, the particle size distribution of the high-entropy MAX phase solid solution material in the sulfur system is about 1-10 μm.

In some embodiments, the high-entropy MAX phase solid solution material in the chalcogenide system includes (Ti, Zr, Hf) ₂ SC, (Ti, Zr, V) ₂ SC, (V, Nb, Ta) ₂ SC, (Ti, Any one or a combination of two or more of Zr, Hf, V) ₂ SC, (Ti, Zr, Hf, V, Nb) ₂ SC, etc., but not limited thereto.

Another aspect of the embodiments of the present invention provides a method for preparing a high-entropy MAX phase solid solution material in a sulfur system, comprising: providing ferrous sulfide as a high-temperature solid sulfur source;

The mixture containing the ferrous sulfide, transition metal element and/or transition metal hydride and transition metal carbide is reacted at 1400 to 1800 ° C for 10 to 30 minutes to obtain the high entropy MAX phase solid solution material in the sulfur system, and its chemical formula is M ₂ SC, wherein M includes any three or a combination of four or more of Ti, Zr, Hf, V, Nb, and Ta.

In some embodiments, the preparation method specifically includes:

mixing ferrous sulfide, transition metal element and/or transition metal hydride and transition metal carbide according to the molar ratio of (1.0-1.2): (1.9-2.1): (0.8-1) to obtain a mixture;

Using a spark plasma sintering system, the mixture is heated to 1400-1800°C at a heating rate of 25-50°C/min, and the reaction is kept for 10-30 minutes, followed by post-treatment to obtain the sulfur-based medium high-entropy MAX phase solid solution material . The reaction mechanism of the preparation method of the present invention may be:

First, by using ferrous sulfide as a high-temperature solid sulfur source, transition metal sulfides are obtained through the replacement reaction between transition metals such as titanium, zirconium, hafnium, vanadium, niobium, and tantalum (or transition metal hydrides) and ferrous sulfide, The high-temperature solid-state sulfur source can undergo replacement reaction with transition metal element (or transition metal hydride) to obtain metal sulfide and elemental iron without decomposing to produce elemental sulfur. The replacement reaction between the transition metal and ferrous sulfide needs to satisfy that the transition metal has stronger reducibility than iron. At the same time, the atoms in solid solution at the M site need to have a small difference in atomic radius and electronegativity; according to the Hume-Rothery semi-empirical rule, the difference in atomic radius needs to be less than 8-10%, and the difference in electronegativity is less than 0.4-0.5 . In addition, valence electron solubility and relative valence effects need to be considered.

Secondly, the generated metal sulfide reacts with the corresponding metal carbide at a certain temperature to obtain a metal carbon-sulfur compound, that is, a sulfur-based ternary, quaternary, and pentary MAX phase solid solution material is successfully obtained.

The ferrous sulfide sulfur source and the sulfur-containing intermediate product used in the preparation method are both stable metal sulfides, which avoids the volatilization of elemental sulfur in the high-temperature preparation process, is beneficial to control the synthesis path of the target phase, and reduces the impact of volatilized sulfur on experimental equipment and experimental equipment. pollution of the environment.

In some embodiments, the transition metal element includes any three or a combination of four or more of Ti, Zr, Hf, V, Nb, Ta, etc., but is not limited thereto.

In some embodiments, the transition metal hydride includes any three or a combination of four or more of titanium hydride, zirconium hydride, hafnium hydride, vanadium hydride, niobium hydride, tantalum hydride, etc., but is not limited thereto. The present invention can also use transition metal hydride mainly to replace the original transition metal element, reduce oxide impurities in the reaction product, and help improve the purity of the target phase.

In some embodiments, the transition metal carbide includes any three or a combination of four or more of TiC, ZrC, HfC, VC, NbC, TaC, etc., but is not limited thereto.

In some embodiments, the post-processing includes: pulverizing the sulfur-based medium-high-entropy MAX phase solid solution material, and grinding to 200-500 mesh to obtain a sulfur-based medium-high-entropy MAX phase solid solution powder material with uniform particle size distribution.

In some embodiments, the post-processing further includes: performing acid washing on the high-entropy MAX phase solid solution powder material in the sulfur system. The elemental iron remaining in the reaction can be removed by pickling process to improve the final target phase purity.

Further, the pickling treatment includes: placing the high-entropy MAX phase solid solution powder material in the sulfur system in an acid solution with a temperature of room temperature to 100° C. and a molar concentration of 1 to 5 mol/L to perform an etching treatment for 1 to 10 minutes. 3 days.

Further, the acid solution includes hydrochloric acid, sulfuric acid, etc., but is not limited thereto.

Further, the specific process of the pickling treatment preferably includes: treating the reacted sulfur-based high-entropy MAX phase solid solution powder material in dilute hydrochloric acid or dilute sulfuric acid with a molar concentration of 1 to 5 mol/L at room temperature to 100 °C. 1 to 3 days.

Further, the method of the present invention is simple and easy to implement, and a high-entropy MAX phase solid solution material with high purity can be obtained in combination with the pickling post-treatment process, which can be used as a reference for the design of the synthesis process of other non-aluminum-based multi-component MAX phase solid solution materials. .

Another aspect of the embodiments of the present invention also provides the use of the aforementioned high-entropy MAX phase solid solution material in the chalcogenide system, which is expected to have good application prospects in the field of extreme environmental structural materials such as nuclear power and high-speed rail.

The technical solutions in the present invention will be clearly and completely described below with reference to the drawings and embodiments of the specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. It should be noted that the raw materials in the following examples can be purchased from the market or prepared by themselves, and the experimental equipment and equipment involved can also be purchased from channels known to those in the relevant technical field.

Example 1:

In this embodiment, the entropy MAX phase solid solution material in the sulfur system is (Ti, Zr, Hf) ₂ SC. The preparation steps of the solid solution material are as follows:

(1) Select titanium carbide, zirconium, zirconium carbide, hafnium hydride and ferrous sulfide as raw materials, according to the molar ratio of TiC: Zr: ZrC: HfH ₂ : FeS 2: 1: 1: 2: 3.2, in grinding with Mix alcohol as a medium for 30min, and dry in a vacuum drying oven. In this embodiment, if the simple substance of hafnium is used for easy oxidation, the use of hafnium hydride is beneficial to improve the purity of the target phase.

(2) Using a spark plasma sintering system, the temperature was kept at 1600°C for 20min at a heating rate of 50°C/min.

(3) crushing the powder obtained in step (2) and grinding to 300 meshes to obtain a precursor powder with uniform particle size distribution.

(4) A dilute hydrochloric acid aqueous solution with a concentration of 3 mol/L was selected as the etchant, and the etching was carried out at 50° C. for 2 days with sufficient magnetic stirring. (5) Using polyvinylidene fluoride microporous membrane (PVDF, pore diameter of 0.45 μm) as the separation membrane, filtering the product obtained in step (4), fully washing with deionized water, and then washing with ethanol and then vacuum drying at room temperature Dry.

The powder treated in step (3) was detected by X-ray diffraction (XRD). The full spectrum analysis of Reitveld method can be obtained (R _wp = 10.2%), this method successfully synthesized the entropy MAX phase solid solution material in (Ti, Zr, Hf) ₂ SC (as shown in Figure 1), and its lattice constant is a = 0.3334 nm, c = 1.1797 nm. A small amount of hafnium oxide impurities and iron appearing in the powder, the former may originate from the oxidation of hafnium element during the preparation process, and the latter originate from the by-products obtained from the replacement reaction of ferrous sulfide and metal raw materials.

Using a scanning electron microscope (SEM) to observe the powder treated in step (5), it can be found that the synthesized powder exhibits a typical MAX phase layered structure (as shown in Figure 2a-2d). As shown in Table 1, energy spectrum analysis can further verify the above speculation. The powder is composed of elements such as Ti, Zr, Hf, S, C, O, etc. The sum of the atomic percentages of Ti, Zr, and Hf elements at the M position is the same as that of S The atomic percent ratio of 1.98 is approximately 2, which is in line with the experimental design and XRD analysis.

Table 1: Energy spectrum analysis results of the obtained powder

Example 2:

In this embodiment, the sulfur-based high-entropy MAX phase solid solution material is (Ti, Zr, Hf, V) ₂ SC. The preparation steps of the solid solution material are as follows:

(1) Select titanium carbide, zirconium, hafnium hydride, vanadium carbide and ferrous sulfide as raw materials, according to the molar ratio of TiC: Zr: HfH ₂ : VC: FeS 2: 2: 2: 2: 4.2, in grinding with Mix alcohol as a medium for 30min, and dry in a vacuum drying oven.

(2) Using a spark plasma sintering system, the temperature was kept at 1600°C for 20min at a heating rate of 50°C/min.

(3) crushing the powder obtained in step (2) and grinding to 300 meshes to obtain a precursor powder with uniform particle size distribution.

(4) A dilute hydrochloric acid aqueous solution with a concentration of 3 mol/L was selected as the etchant, and the etching was carried out at 50° C. for 2 days with sufficient magnetic stirring.

(5) Using polyvinylidene fluoride microporous membrane (PVDF, pore diameter of 0.45 μm) as the separation membrane, filtering the product obtained in step (4), fully washing with deionized water, and then washing with ethanol and then vacuum drying at room temperature Dry.

The powder treated in step (5) is detected by X-ray diffraction (XRD). (R _wp = 13.51%) can be obtained by the full spectrum analysis of Reitveld method. This method successfully synthesized (Ti, Zr, Hf, V) ₂ SC high-entropy MAX phase solid solution material (as shown in Figure 3). Its lattice constant is a=0.3327nm, c=1.1723nm. A small amount of vanadium carbide titanium and hafnium oxide impurities appear in the powder, the former belongs to the intermediate product that has not been fully reacted, and the latter belongs to the oxidation of hafnium element in the preparation process.

Using a scanning electron microscope (SEM) to observe the powder treated in step (5), it can be found that the synthesized powder exhibits a typical MAX phase layered structure (as shown in Figure 4a-4f). As shown in Table 2, energy spectrum analysis can further verify the above speculation, and the powder contains Ti, Zr, Hf, V at the M site, and S at the A site. The ratio of the sum of the mole fractions of Ti, Zr, Hf, and V at the M site to the mole fraction of S is approximately 2, which is in line with the experimental design and XRD analysis.

Table 2: Energy spectrum analysis results of the obtained powder

Example 3:

In this embodiment, the sulfur-based high-entropy MAX phase solid solution material is (Ti, Zr, Hf, V, Nb) ₂ SC. The preparation steps of the solid solution material are as follows:

(1) Select titanium, titanium carbide, zirconium, hafnium hydride, vanadium carbide, niobium carbide and ferrous sulfide as raw materials, and the molar ratio of Ti:TiC:Zr:HfH ₂ :VC:NbC:FeS is 1:1:2 : 2: 2: 2: 5.1, mix with alcohol as a medium for 30min during grinding, and dry in a vacuum drying oven.

(2) Using a spark plasma sintering system, the temperature was kept at 1600°C for 20min at a heating rate of 50°C/min.

(3) crushing the powder obtained in step (2) and grinding to 300 meshes to obtain a precursor powder with uniform particle size distribution.

(4) A dilute hydrochloric acid aqueous solution with a concentration of 3 mol/L was selected as the etchant, and the etching was carried out at 50° C. for 2 days with sufficient magnetic stirring.

(5) Using polyvinylidene fluoride microporous membrane (PVDF, pore diameter of 0.45 μm) as the separation membrane, filtering the product obtained in step (4), fully washing with deionized water, and then washing with ethanol and then vacuum drying at room temperature Dry.

The powder treated in step (5) is detected by X-ray diffraction (XRD). (R _wp =15.67%) can be obtained by the full spectrum analysis of Reitveld method. This method successfully synthesized (Ti, Zr, Hf, V, Nb) ₂ SC solid solution material (as shown in Figure 5), and its lattice constant is a = 0.3316 nm, c = 1.1652 nm. Vanadium carbide, niobium titanium carbide and hafnium oxide impurities appearing in the powder, the former two belong to raw materials and intermediate products that have not been fully reacted, and the latter belongs to the oxidation of hafnium element in the preparation process.

Using a scanning electron microscope (SEM) to observe the powder treated in step (3), it can be found that the synthesized powder exhibits a typical MAX phase layered structure (as shown in Fig. 6a-Fig. 6g). Energy spectrum analysis can further verify the above speculation, the powder is composed of Ti, Zr, Hf, V, Nb, S, C, O and other elements, and the sum of the mole fractions of Ti, Zr, Hf, V, and Nb elements in the M position The ratio to the mole fraction of S is approximately 2, which is in line with the experimental design and XRD analysis.

Table 3: Energy spectrum analysis results of the obtained powder

Example 4:

In this embodiment, the entropy MAX phase solid solution material in the sulfur system is (Ti, Zr, Ta) ₂ SC. The preparation steps of the solid solution material are as follows:

(1) Select titanium carbide, zirconium, zirconium carbide, tantalum and ferrous sulfide as raw materials, according to the molar ratio of TiC:Zr:ZrC:Ta:FeS 2:1:1:2:3.2, in grinding, use alcohol as The medium was mixed for 30 minutes and dried in a vacuum drying oven.

(2) Using a spark plasma sintering system, the temperature was kept at 1800°C for 10 min at a heating rate of 25°C/min.

(3) crushing the powder obtained in step (2) and grinding to 200 meshes to obtain a precursor powder with uniform particle size distribution.

(4) A dilute hydrochloric acid aqueous solution with a concentration of 1 mol/L was selected as the etchant, and the etching was carried out at 50° C. for 2 days with sufficient magnetic stirring.

(5) Using polyvinylidene fluoride microporous membrane (PVDF, pore diameter of 0.45 μm) as the separation membrane, filtering the product obtained in step (4), fully washing with deionized water, and then washing with ethanol and then vacuum drying at room temperature Dry.

The powder treated in step (3) was detected by X-ray diffraction (XRD). It can be concluded from the full spectrum analysis of Reitveld method that the method successfully synthesized the entropy MAX phase solid solution material in (Ti, Zr, Ta) ₂ SC.

Example 5

In this embodiment, the entropy MAX phase solid solution material in the sulfur system is (Ti, Zr, Ta) ₂ SC. The preparation steps of the solid solution material are as follows:

(1) Select titanium carbide, zirconium, zirconium carbide, tantalum and ferrous sulfide as raw materials, and the molar ratio of TiC:Zr:ZrC:Ta:FeS is 1:1.1:0.9:2:3.2, and alcohol is used in grinding. The medium was mixed for 30 minutes and dried in a vacuum drying oven.

(2) Using a spark plasma sintering system, the temperature was kept at 1400°C for 30 minutes at a heating rate of 40°C/min.

(3) The powder obtained in step (2) is crushed and ground to 500 mesh to obtain a precursor powder with uniform particle size distribution.

(4) A dilute sulfuric acid aqueous solution with a concentration of 5 mol/L was selected as the etchant, and the etching was performed at 100° C. for 1 day, with sufficient magnetic stirring.

(5) Using polyvinylidene fluoride microporous membrane (PVDF, pore diameter of 0.45 μm) as the separation membrane, filtering the product obtained in step (4), fully washing with deionized water, and then washing with ethanol and then vacuum drying at room temperature Dry.

The powder treated in step (3) was detected by X-ray diffraction (XRD). It can be concluded from the full spectrum analysis of Reitveld method that the method successfully synthesized the entropy MAX phase solid solution material in (Ti, Zr, Ta) ₂ SC.

Example 6

This example is basically the same as Example 1, except that the molar ratio of ferrous sulfide (FeS), transition metal element and transition metal hydride (Zr, HfH ₂ ) to transition metal carbide (TiC, ZrC) is 1.0:1.9:0.9.

Example 7

This example is basically the same as Example 1, except that the molar ratio of ferrous sulfide (FeS), transition metal element and transition metal hydride (Zr, HfH ₂ ) to transition metal carbide (TiC, ZrC) is 1.2:2.1:1.

Comparative Example 1

This example is basically the same as Example 1, except that the molar ratio of ferrous sulfide (FeS), transition metal element (Ti) and transition metal carbide (TiC) is 1:1:1. The hardness (8GPa) of the obtained Ti ₂ SC is smaller than that of the medium and high entropy (Ti, Zr, Hf) ₂ SC (9GPa), (Ti, Zr, Hf, V) ₂ SC (10GPa), which reflects the medium and high entropy. Strength advantage of the back material.

Comparative Example 2

This example is basically the same as Example 1, except that the molar ratio of ferrous sulfide (FeS), transition metal element (Zr) and transition metal carbide (TiC) is 1:1:1. The hardness of the obtained (Ti, Zr) ₂ SC (about 8GPa) is smaller than that of the medium and high entropy (Ti, Zr, Hf) ₂ SC (9GPa), (Ti, Zr, Hf, V) ₂ SC (10GPa) , which reflects the strength advantage of the material after medium and high entropy.

To sum up, the ferrous sulfide sulfur source and the sulfur-containing intermediate product used in the preparation method of the present invention are both stable metal sulfides, which avoids the volatilization of elemental sulfur in the high-temperature preparation process, is beneficial to control the synthesis path of the target phase, and reduces the volatilized sulfur Pollution of experimental equipment and the environment. The method is simple and easy to implement, and combined with the pickling post-treatment process, a high-entropy MAX phase solid solution material with high purity can be obtained, which can be used as a reference for the design of the synthesis process of other non-aluminum-based multi-component MAX phase solid solution materials. The obtained high-entropy MAX phase solid solution material in chalcogenide is expected to have good application prospects in the field of extreme environmental structural materials such as nuclear power and high-speed rail.

In addition, the inventors of the present application also carried out relevant experiments with other raw materials and process conditions mentioned in this specification instead of the corresponding raw materials and process conditions in the foregoing Examples 1-3, and the results all show that high-entropy MAX phase solid solution materials in sulfur systems can be obtained. . The aspects, embodiments, features, and examples of the present invention are to be considered in all respects illustrative and not intended to limit the invention, the scope of which is defined only by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.

The use of headings and sections in this application is not meant to limit the invention; each section is applicable to any aspect, embodiment or feature of the invention.

Throughout this specification, where a composition is described as having, comprising or including particular components, or where a process is described as having, comprising or including particular process steps, it is contemplated that the compositions of the present teachings will also be substantially The above consists of or consists of the recited components, and the processes taught herein also consist essentially of, or consist of, the recited process steps.

The use of the terms "include, includes, including," "have, has, or having" should generally be understood to be open-ended and not limiting unless specifically stated otherwise.

It should be understood that the order of the steps or the order in which the particular actions are performed is not critical so long as the present teachings remain operable. Furthermore, two or more steps or actions may be performed simultaneously.

Although the present invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions and/or additions and the like may be made without departing from the spirit and scope of the invention Effects replace elements of the described embodiments. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is not intended herein to limit the invention to the particular embodiments disclosed for carrying out the invention, but it is intended that this invention include all embodiments falling within the scope of the appended claims. Furthermore, unless specifically stated, any use of the terms first, second, etc. does not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another.

Claims (10)

1. a high-entropy MAX phase solid solution material in a sulfur system, is characterized in that: the M position of the high-entropy MAX phase solid solution material in the sulfur system includes any three kinds of transition metal elements Ti, Zr, Hf, V, Nb, Ta Or a combination of four or more, the A site is sulfur, and the X site is carbon. 2 . The high-entropy MAX phase solid solution material in the sulfur system according to claim 1 , wherein the chemical formula of the high-entropy MAX phase solid solution material in the sulfur system is M ₂ SC, wherein

_Mi includes any three or a combination of more than four of Ti, Zr, Hf, V, Nb and Ta, _xi is the molar constant of the _Mi component at the M position, n is 3 to 5, and i refers to the first i components, which are integers ranging from 1 to n. 3. The high-entropy MAX phase solid solution material according to claim 1, wherein the high-entropy MAX phase solid solution material in the sulfur system has a hexagonal layered structure, and the space group is P63/mmc; And/or, the particle size of the high-entropy MAX phase solid solution material in the sulfur system is 1-10 μm; And/or, the high-entropy MAX phase solid solution material in the sulfur system includes (Ti, Zr, Hf) ₂ SC, (Ti, Zr, V) ₂ SC, (V, Nb, Ta) ₂ SC, (Ti, Zr, Any one or a combination of two or more of Hf, V) ₂ SC and (Ti, Zr, Hf, V, Nb) ₂ SC. 4. the preparation method of the high-entropy MAX phase solid solution material in the sulfur system described in any one of claim 1-3, it is characterized in that comprising: Provide ferrous sulfide as a high temperature solid sulfur source; The mixture containing the ferrous sulfide, transition metal element and/or transition metal hydride and transition metal carbide is reacted at 1400 to 1800 ° C for 10 to 30 minutes to obtain the high entropy MAX phase solid solution material in the sulfur system, and its chemical formula is M ₂ SC, wherein M includes any three or a combination of four or more of Ti, Zr, Hf, V, Nb, and Ta. 5. preparation method according to claim 4 is characterized in that specifically comprising: mixing ferrous sulfide, transition metal element and/or transition metal hydride and transition metal carbide according to the molar ratio of (1.0-1.2): (1.9-2.1): (0.8-1) to obtain a mixture; Using a spark plasma sintering system, the mixture is heated to 1400-1800°C at a heating rate of 25-50°C/min, and the reaction is kept for 10-30 minutes, followed by post-treatment to obtain the sulfur-based medium high-entropy MAX phase solid solution material . 6. The preparation method according to claim 4 or 5, characterized in that: the transition metal element comprises any three or a combination of four or more in Ti, Zr, Hf, V, Nb, Ta; and/or , the transition metal hydride includes any three or a combination of four or more selected from titanium hydride, zirconium hydride, hafnium hydride, vanadium hydride, niobium hydride, and tantalum hydride. 7 . The preparation method according to claim 4 , wherein the transition metal carbide comprises any three or a combination of more than four of TiC, ZrC, HfC, VC, NbC, and TaC. 8 . 8 . The preparation method according to claim 5 , wherein the post-processing comprises: pulverizing the high-entropy MAX phase solid solution material in the sulfur system, and grinding to 200-500 mesh to obtain sulfur with uniform particle size distribution. 9 . It is a medium-high-entropy MAX phase solid solution powder material. 9 . The preparation method according to claim 8 , wherein the post-processing further comprises: performing a pickling process on the high-entropy MAX phase solid solution powder material in the sulfur system, and preferably, the pickling process comprises the following steps: 10 . : The high-entropy MAX phase solid solution powder material in the sulfur system is placed in an acid solution with a temperature of room temperature to 100° C. and a molar concentration of 1 to 5 mol/L for etching treatment for 1 to 3 days; preferably, the acid The liquid includes hydrochloric acid and/or sulfuric acid. 10 . The use of the high-entropy MAX phase solid solution material in the sulfur system according to any one of claims 1 to 3 in the field of preparing nuclear power or high iron structural materials. 11 .

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