MAX-phase multi-component A-site solid solution as well as preparation method and application thereof

Abstract

The invention discloses an MAX-phase multi-component A-site solid solution as well as a preparation method and application thereof. For the binary A-site solid solution, the expression of the binary A-site solid solution is Ti2 (X + Y) C, the element X is selected from Sn or In, and the element Y is selected from one of Ge, Cu, Si, Fe, Ga, Bi and Ag; for a three-element or more A-site solid solution, the expression of the A-site solid solution is Ti2 (SnIn + Z) C, and the Z element is selected from at least one of Al, Ge, Cu, Si, Fe, Ga, Bi and Ag. The controllable synthesis of the MAX-phase multi-component A-site solid solution is realized by a'vacancy presetting + isomorphic occupation 'method. According to the method, phase separation caused by thermodynamic competition is avoided, elements such as Bi and Ag can be introduced into the A site, a series of multi-component A-site solid solutions are synthesized, the component space of the MAX phase is greatly enriched, and the method can be applied to the fields of high-speed rails, ocean, electronic packaging, nuclear energy, aerospace, medicine and the like.

Description

Technical Field

[0001] The present invention relates to a cermet MAX-phase solid solution and a preparation method and application thereof, and particularly relates to a multi-component A-site solid solution of the MAX phase and a preparation method and application thereof. Background Art

[0002] The MAX phase is a class of ternary nano-layered metal carbides and nitrides, and its general formula can be expressed as M n+1 AX n , where M is a transition metal element, A is mainly a group IIIA or group IVA main group element, and X is a C or N element. The crystal structure of such compounds is a hexagonal structure, and the space group is P63 / mmc (No. 194). Microstructurally, the MAX phase is composed of alternating stacks of M6X octahedral layers and A-site single atomic layers. The MAX phase has excellent properties of both metals and ceramics, including good electrical conductivity, thermal conductivity, excellent machinability, oxidation resistance, corrosion resistance, and radiation damage resistance, and has great application potential in many fields such as high-speed rail, marine, electronic packaging, nuclear energy, aerospace, and medicine.

[0003] The composition design and performance regulation of MAX-phase materials are crucial for their practical applications. Currently, more than 300 kinds of MAX phases have been synthesized, and solely relying on the discovery of new elements at the M / A / X sites to expand the MAX-phase family has faced bottlenecks. Therefore, the element solid solution strategy has become an effective way to expand its compositional diversity and regulate properties.

[0004] However, current research mainly focuses on M-site solid solutions, and a variety of medium- and high-entropy MAX phases at the M-site have been successfully synthesized. For example, the Huang Qing team prepared a high-hardness MAX phase (TiVNbZrHf)2SnC material with a high-entropy M-site (ZL 202110157981.0). In contrast, the research on A-site solid solutions is relatively scarce and is only limited to binary systems. It is difficult to synthesize multi-component A-site solid solutions (≥ three elements) through existing technologies (such as pressureless sintering, hot pressing sintering, magnetron sputtering, spark plasma sintering, etc.). Summary of the Invention

[0005] Object of the Invention: The object of the present invention is to provide a multi-component A-site solid solution of the MAX phase that can enrich and expand the members of the MAX-phase family;

[0006] The second object of the present invention is to provide a preparation method for the above-mentioned multi-component A-site solid solution of the MAX phase;

[0007] The third object of the present invention is to provide an application of the above-mentioned multi-component A-site solid solution of the MAX phase.

[0008] Technical solution: For the MAX-phase multi-component A-site solid solution of the present invention, for the binary A-site solid solution, its chemical formula is Ti2(X + Y)C, where the X element is selected from Sn or In, and the Y element is selected from one of Ge, Cu, Si, Fe, Ga, Bi, Ag;

[0009] For the ternary or higher A-site solid solution, its chemical formula is Ti2(SnIn + Z)C, where the Z element is selected from at least one of Al, Ge, Cu, Si, Fe, Ga, Bi, Ag.

[0010] The preparation method of the above-mentioned MAX-phase multi-component A-site solid solution includes the following steps:

[0011] (1) Mix TiC, Ti, and powders of two or more A-site elements to obtain a mixed powder;

[0012] (2) Press the mixed powder into a green body;

[0013] (3) Under a protective atmosphere, first perform the "preset vacancy" step, that is, first sinter the green body in a certain temperature range, and use Sn and / or In to form a primary MAX-phase lattice with a high concentration of A-site vacancies; then perform the "isomorphic occupation" step, that is, then sinter in a higher temperature range, and promote the diffusion of other A-site elements into the A vacancies through liquid-phase mass transfer; after sintering, the MAX-phase multi-component A-site solid solution is obtained.

[0014] Among them, in step (1), TiC, Ti, and powders of two A-site elements are mixed; the two A-site elements include X and Y, where X is selected from Sn or In, and Y is selected from one of Ge, Cu, Si, Fe, Ga, Bi, Ag; the mixing molar ratio is TiC:Ti:X:Y = 0.9:1:x:(1 - x), where x ≥ 0.4;

[0015] Among them, in step (1), TiC, Ti, and powders of more than two A-site elements are mixed; the more than two A-site elements include Sn and In, and Z, where Z is selected from at least one of Al, Ge, Cu, Si, Fe, Ga, Bi, Ag; the mixing molar ratio is TiC:Ti:(Sn + In):Z = 0.9:1:x:(1 - x), where x ≥ 0.4.

[0016] When the powder ratio is within the above range, a high-purity phase of the MAX-phase multi-component A-site solid solution can be obtained by sintering; when it is not within this range, it may not be possible to obtain the MAX-phase solid solution after sintering, or there are many impurities in the product, that is, multiple competing phases are generated, or the raw materials do not react completely and remain in the product, and thus the composition of the solid solution cannot be controlled.

[0017] Among them, in step (2), the mixed powder is made into a green body under a certain pressure and holding time. The pressure is 0 to 50 MPa, and the holding time is 0 to 10 min. Applying a certain pressure to the mixed powder and holding it is beneficial to the powder contacting each other during sintering, improving the reaction efficiency, and the dense green body can reduce the loss of volatile metals during the heating process.

[0018] Among them, in step (3), first sinter the green body at a temperature of 950 to 1050 °C for 20 to 30 min. The sintering step at this temperature is called the "presetting vacancy" step; then sinter at a temperature of 1150 to 1450 °C for 0.5 to 2 h. The sintering step at this temperature is called the "isomorphic occupation" step. When the sintering temperature is within the above range, a high-purity phase of the MAX phase solid solution can be obtained by sintering; when the sintering temperature is too low, the MAX phase solid solution cannot be formed, and when the sintering temperature is too high, serious volatilization of metal elements in the raw materials may occur, deviating from the actual composition. When the sintering holding time is too short, the reaction may be incomplete, and when the sintering holding time is too long, the stability of the formed MAX phase may be reduced, and A-site atoms may diffuse out of the MAX phase lattice, and even thermal decomposition may occur.

[0019] Among them, in step (3), when sintering at a temperature of 950 to 1050 °C, the heating rate is 5 to 10 °C / min; when sintering at a temperature of 1150 to 1450 °C, the heating rate is 2 to 5 °C / min; after sintering is completed, it is cooled to 200 to 300 °C at a cooling rate of 2 to 10 °C / min, and then naturally cooled in the furnace to obtain the MAX phase multi-component A-site solid solution.

[0020] Among them, in step (3), the protective atmosphere is one of vacuum, helium, argon or argon-hydrogen mixture.

[0021] Among them, in step (3), after the MAX phase solid solution material obtained at the end of the entire sintering process is crushed into powder, the powder is pickled with dilute hydrochloric acid for 5 to 12 h to remove impurities, and then dried.

[0022] The above-mentioned MAX phase multi-component A-site solid solution is applied in the fields of high-speed rail, ocean, electronic packaging, nuclear energy, aerospace, and medicine.

[0023] Principle of the invention: The synthesis process of the MAX phase and its solid solution involves complex multi-step reaction kinetics, and the purity of the final product is jointly restricted by thermodynamic and kinetic factors. By innovatively proposing the cooperative strategy of "presetting vacancy" and "isomorphic occupation" and combining the concept of high-entropy design, the present invention has successfully realized the controllable synthesis of multi-component A-site solid solutions. The core principle is as follows:

[0024] (1) Key scientific issues in the synthesis of multi-component A-site solid solutions: The MAX phase has a narrow phase region (only one point) in the ternary phase diagram, has a very small composition stability range, and its formation involves multi-step reactions; M-site elements are usually transition metals with similar physical and chemical properties, while A-site elements have large differences in electronegativity, atomic radius, etc., which makes phase separation more likely to occur when the number of A-site elements increases; in addition, AA, MA, and MAX elements may interact with each other to form thermodynamically competitive phases, hindering the formation of single-phase MAX solid solutions. Therefore, it is difficult to achieve controllable synthesis of A-site multi-component solid solutions using traditional methods. However, the high entropy effect can be used to stabilize new elements and integrate the performance advantages of multiple elements, thereby breaking through thermodynamic limitations.

[0025] (2) "Pre-vacancies" step: The present invention has found through exploration that the formation mechanism of binary solid solutions containing Sn / In at the A site shows that the Sn / In-rich side solid solution can form primary Ti2SnC / Ti2InC phases at relatively low temperatures, providing seeds for subsequent solid solution formation. Based on this, a "pre-vacancies" strategy is proposed, which uses Sn / In to form a primary MAX phase lattice containing a high concentration of A vacancies at relatively low temperatures, which is beneficial to the diffusion of other A-site elements. The schematic diagram is shown in FIG. Figure 1 shown.

[0026] (3) “Isomorphous occupancy” step: Based on the “pre-placed vacancies”, liquid phase mass transfer at a higher temperature is used to promote the diffusion of other A-site elements into the primary MAX phase lattice containing a high concentration of A vacancies, thus breaking through the thermodynamic limitations of traditional synthesis and achieving the controllable synthesis of multi-component A-site solid solutions. The schematic diagram is shown in Figure 2. Figure 1 shown.

[0027] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The method has wide applicability and is the first to use the "pre-vacancies + isomorphous occupancy" strategy for multi-component A-site solid solutions. By avoiding thermodynamic competition reactions, the controllable preparation of MAX phase multi-component A-site solid solutions is achieved; (2) It successfully breaks through the limitations of traditional binary systems and realizes the effective solid solution of new elements such as Ag and Bi at the A-site for the first time, synthesizing a series of multi-component A-site solid solutions, significantly expanding the composition design space of MAX phase materials; (3) By utilizing A-site alloying and entropy increase engineering, the composition of the A atomic layer is designed, and the preparation of A-site high-entropy MAX phase materials is realized for the first time; (4) By precisely controlling the composition and ratio of the A-site elements, it is expected to achieve its application in high-speed rail, ocean, electronic packaging, nuclear energy, aerospace, medicine and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the principle of preparing a MAX phase multi-component A-site solid solution according to the present invention;

[0029] Figure 2XRD patterns of the samples prepared in Examples 1-2 and Comparative Examples 1-2 of the present invention;

[0030] Figure 3 XRD patterns of the samples prepared in Examples 3-5 and Comparative Example 4;

[0031] Figure 4 TEM-EDS images of the Ti2(Sn 1 / 3 In 1 / 3 Al 1 / 3 )C powder prepared in Example 3;

[0032] Figure 5 TEM-EDS images of the Ti2(Sn 1 / 4 In 1 / 4 Al 1 / 4 Bi 1 / 4 )C powder prepared in Example 4;

[0033] Figure 6 TEM-EDS images of the Ti2(Sn 1 / 5 In 1 / 5 Al 1 / 5 Bi 1 / 5 Ag 1 / 5 )C powder prepared in Example 5;

[0034] Figure 7 SEM image and EDS spectrum of the sample prepared in Comparative Example 2;

[0035] Figure 8 XRD pattern and EDS spectrum of the sample prepared in Comparative Example 3. Detailed implementation manners

[0036] The present invention will be further described in detail below.

[0037] Example 1

[0038] A MAX-phase binary A-site solid solution Ti2(Sn 0.8 Bi 0.2 )C, and its preparation method includes the following steps:

[0039] (1) Commercial TiC powder, Ti powder, Sn powder, and Bi powder are prepared according to the molar ratio of TiC:Ti:Sn:Bi = 0.9:1:0.8:0.2, mixed with a powder mixer for 24 h to make the mixture uniform, and then dried at 100 °C for 2 h to remove moisture. Finally, the mixed powder is pressed into a green body with a diameter of 16 mm using a tablet press, the set pressure is 20 MPa, and the pressure holding time is 2 min;

[0040] (2) Using the method of pressureless sintering, sinter the prepared green body in a tubular furnace with argon as the protective atmosphere. First, heat it to 1000 °C and hold for 20 min with a heating rate of 10 °C / min. The sintering step at this temperature is called the "preset vacancy" step; then sinter at 1400 °C for 1 h with a heating rate of 5 °C / min. The sintering step at this temperature is called the "isomorphic substitution" step; after sintering, cool at a rate of 5 °C / min to obtain the Ti2(Sn 0.8 Bi 0.2 )C sintered material; use a crusher to crush the sintered material into powder and sieve it through a 300-mesh sieve for standby.

[0041] Then, carry out acid washing and impurity removal on the sieved powder. Add 5 g of Ti2(Sn 0.8 Bi 0.2 )C to 100 ml of 1 mol / L hydrochloric acid, and accelerate the reaction by means of magnetic stirring. The magnetic stirring speed is 500 r / min, the reaction temperature is 50 °C, and the reaction time is 5 h; after impurity removal, use the method of vacuum filtration to remove the liquid phase, and put the obtained Ti2(Sn 0.8 Bi 0.2 )C powder into a vacuum oven for drying. The drying temperature is 80 °C and the drying time is 8 h.

[0042] Use an X-ray diffractometer (XRD) to perform phase analysis on the dried Ti2(Sn 0.8 Bi 0.2 )C powder, and the results are as Figure 2 shown. The XRD pattern shows that through the "preset vacancy + isomorphic substitution" synthesis method, a high-purity Ti2(Sn 0.8 Bi 0.2 )C phase is successfully prepared.

[0043] For the MAX phase, the mixing entropy of the A site can be calculated using , where R is the gas constant, n represents the number of components, and C i is the molar fraction of the i-th component. The calculated mixing entropy of the A site is 0.53R, belonging to the category of low-entropy MAX phases (ΔS mix ≤ 1R).

[0044] Example 2

[0045] A MAX-phase binary A-site solid solution Ti2(In 0.8 Ag 0.2) C powder material. Compared with Example 1 in its preparation method, the differences are as follows: in step (1), commercial TiC powder, Ti powder, In powder, and Ag powder are formulated according to the molar ratio of TiC:Ti:In:Ag = 0.9:1:0.8:0.2, the set pressure for pressing the green body is 30 Mpa, and the pressure holding time is 1 min; in step (2), the sintering temperature for the "isomorphic site occupation" step is 1150 °C, and the sintering time is 2 h.

[0046] XRD was used to analyze the phase of Ti2(In 0.8 Ag 0.2 )C powder, and the results are as Figure 2 shown. The XRD pattern shows that through the "preset vacancy + isomorphic site occupation" synthesis method, a high-purity Ti2(In 0.8 Ag 0.2 )C phase was successfully prepared. The calculated mixing entropy at site A is 0.55R, belonging to the category of low-entropy MAX phases (ΔS mix ≤1R).

[0047] Example 3

[0048] A MAX-phase medium-entropy site-A solid solution Ti2(Sn 1 / 3 In 1 / 3 Al 1 / 3 )C powder material. Compared with Example 1 in its preparation method, the differences are as follows: in step (1), commercial TiC powder, Ti powder, Sn powder, In powder, and Al powder are formulated according to the molar ratio of TiC:Ti:Sn:In:Al = 0.9:1:0.33:0.33:0.33, the set pressure for pressing the green body is 15 Mpa, and the pressure holding time is 5 min; in step (2), the sintering temperature for the "isomorphic site occupation" step is 1300 °C, and the sintering time is 2 h.

[0049] XRD was used to analyze the phase of the dried Ti2(Sn 1 / 3 In 1 / 3 Al 1 / 3 )C powder, and the results are as Figure 3 shown. The XRD pattern shows that the Ti2(Sn 1 / 3 In 1 / 3 Al 1 / 3 )C phase has a very high phase purity, and no impurities were detected except for the MAX-phase diffraction peaks.

[0050] The actual composition of the synthesized MAX phase A-site solid solution was determined by combining EDS energy spectrum. Samples were taken at 10 points, and the average value was calculated. The EDS composition detection results of the samples are shown in Table 1. The results show that the Ti / A value in the sample is close to 2, and the ratio of the A-site element contents is close to 1:1:1, meeting the elemental ratio requirements of the 211-type MAX phase and the requirement that the component contents in high-entropy alloys are close to equimolar ratios (5 - 35 at%). The calculated mixing entropy of the A-site is 1.10R, belonging to the category of medium-entropy MAX phases (1R ≤ ΔS mix ≤ 1.5R).

[0051] The distribution of the constituent elements of the sample was analyzed by combining transmission electron microscopy (TEM) with EDS area scanning. The results are as Figure 4 shown. The TEM-EDS image shows that the constituent elements Ti, Sn, In, Al, and C in the sample are evenly distributed, indicating the successful realization of homogeneous solid solution in the A-site.

[0052] Example 4

[0053] A MAX phase medium-entropy A-site solid solution Ti2(Sn 1 / 4 In 1 / 4 Al 1 / 4 Bi 1 / 4 )C powder material. Compared with Example 1 in its preparation method, the difference lies in that in step (1), commercial TiC powder, Ti powder, Sn powder, In powder, Al powder, and Bi powder are formulated according to the molar ratio of TiC:Ti:Sn:In:Al:Bi = 0.9:1:0.25:0.25:0.25:0.25; in step (2), the sintering temperature for the "preset vacancy" step is 1050 °C, and the holding time is 20 min.

[0054] XRD was used to perform phase analysis on the dried Ti2(Sn 1 / 4 In 1 / 4 Al 1 / 4 Bi 1 / 4 )C powder. The results are as Figure 3 shown. The XRD pattern shows that the Ti2(Sn 1 / 4 In 1 / 4 Al 1 / 4 Bi 1 / 4 )C phase has a very high phase purity. Except for the MAX phase diffraction peaks, only extremely small amounts of Ti3InC and TiC impurities were detected.

[0055] The actual composition of the synthesized MAX phase A-site solid solution was determined by combining EDS energy spectrum. Ten points of the sample were sampled and the average value was calculated. The EDS composition detection results of the sample are shown in Table 1. The results show that the Ti / A value in the sample is close to 2. Although the content of the A-site element Bi is relatively low, it meets the elemental ratio requirements of the 211-type MAX phase and the requirement that the component content in the high-entropy alloy is close to the equimolar ratio (5-35 at%). And the mixing entropy of the A-site is 1.33R, belonging to the category of medium-entropy MAX phase (1R ≤ ΔS mix ≤ 1.5R).

[0056] The distribution of the constituent elements of the sample was analyzed by TEM combined with EDS area scanning. The results are as Figure 5 shown. The TEM-EDS image shows that the constituent elements Ti, Sn, In, Al, Bi, and C of the sample are evenly distributed, indicating that uniform solid solution of the A-site has been successfully achieved.

[0057] Example 5

[0058] A MAX phase high-entropy A-site solid solution Ti2(Sn 1 / 5 In 1 / 5 Al 1 / 5 Bi 1 / 5 Ag 1 / 5 )C powder material. Compared with Example 1, the preparation method is different in that in step (1), commercial TiC powder, Ti powder, Sn powder, In powder, Al powder, Bi powder, and Ag powder are formulated according to the molar ratio of TiC:Ti:Sn:In:Al:Bi:Ag = 0.9:1:0.2:0.2:0.2:0.2:0.2.

[0059] XRD was used to analyze the phase of the dried Ti2(Sn 1 / 5 In 1 / 5 Al 1 / 5 Bi 1 / 5 Ag 1 / 5 )C powder. The results are as Figure 3 shown. The XRD pattern shows that the Ti2(Sn 1 / 5 In 1 / 5 Al 1 / 5 Bi 1 / 5 Ag 1 / 5 )C phase has a very high phase purity. Except for the MAX phase diffraction peak, only very small amounts of elemental Ag and TiC impurities were detected.

[0060] The actual composition of the synthesized MAX phase A-site solid solution was determined by combining EDS energy spectrum. Ten points of the sample were sampled and the average value was calculated. The EDS composition detection results of the sample are shown in Table 1. The results show that the Ti / A value in the sample is close to 2. Although the content of the A-site element Ag is relatively low, it meets the elemental ratio of the 211-type MAX phase and the requirement that the component contents in the high-entropy alloy are close to the equimolar ratio (5-35 at%). And the mixing entropy of the A-site is 1.59R, belonging to the category of high-entropy MAX phase (ΔS mix ≥1.5R).

[0061] The distribution of the constituent elements of the sample was analyzed by combining TEM with EDS area scanning. The results are as Figure 6 shown. The TEM-EDS image shows that the constituent elements Ti, Sn, In, Al, Bi, Ag, and C of the sample are evenly distributed, indicating that uniform solid solution of the A-site has been successfully achieved.

[0062] Control Example 1

[0063] An attempt was made to prepare a MAX phase Ti2AgC powder material. The preparation method is different from that of Example 1 in that in step (1), commercial TiC powder, Ti powder, and Ag powder are prepared according to the molar ratio of TiC:Ti:Ag = 0.9:1:1.

[0064] The phase analysis of the dried powder was carried out by XRD. The results are as Figure 2 shown. The XRD pattern shows that no diffraction peaks of the typical MAX phase were detected in the sample, and only TiC and elemental Ag were detected. This is mainly attributed to the fact that Ag does not react with TiC, indicating that it is extremely challenging to directly synthesize the terminal Ti2AgC by traditional pressureless sintering.

[0065] Control Example 2

[0066] An attempt was made to prepare a MAX phase A-site solid solution Ti2(In 0.8 Ag 0.2 )C powder material. The preparation method is different from that of Example 1 in that the sintering temperature in the "isomorphic site occupation" step in step (2) is 1500 °C and the sintering time is 1 h.

[0067] The phase analysis of the powder was carried out by XRD. The results are as Figure 2 shown. The XRD pattern shows that in addition to the diffraction peaks of the typical 211-type MAX phase detected in the sample, obvious TiC, elemental In, and impurities of AgIn2 and AgTi3 were also detected, resulting in serious phase separation. Compared with the results of Example 2, too high a sintering temperature in the "isomorphic site occupation" step will seriously affect the phase purity of the sample.

[0068] The composition of the particles was determined by SEM combined with EDS energy spectrum analysis, and the results are as Figure 7 shown. SEM morphology analysis shows that there are a large number of fine impurity particles on the surface of the MAX phase particles. Combining the EDS surface scanning results and XRD diffraction results for further analysis, it is speculated that these impurities may be intermetallic compounds of AgIn2 and AgTi3.

[0069] Comparative Example 3

[0070] An attempt was made to prepare a MAX phase A-site solid solution Ti2(Sn 0.8 Bi 0.2 )C powder material. Compared with Example 1 in its preparation method, the difference lies in that the sintering temperature of the "presetting vacancy" step in step (2) is 800 °C and the holding time is 20 min.

[0071] The phase analysis of the powder was carried out by XRD, and the results are as Figure 8 shown in a. The XRD pattern shows that the diffraction peaks of MAX phase Ti2SnC are detected in the sample, which highly coincides with the Ti2SnC card. The intermetallic compound of Sn 0.3 Bi 0.7 is also detected.

[0072] The composition of the particles was determined by EDS energy spectrum analysis, and the results are as Figure 8 shown in b. The EDS spectrum shows that the particles only contain three elements of Ti, Sn, and C. It is worth noting that the characteristic signal of Bi element is not detected in the spectrum, indicating that the product is a pure Ti2SnC phase, rather than the expected Ti2(Sn 0.8 Bi 0.2 )C. Comparing with the results of Example 1, it shows that when the sintering temperature of the "presetting vacancy" step is too low, it is easy to form the SnBi intermetallic compound, resulting in the inability of Bi element to enter the MAX phase lattice, thus making it difficult to generate the Bi-containing solid solution.

[0073] Comparative Example 4

[0074] An attempt was made to prepare a MAX phase A-site solid solution Ti2(Sn 1 / 4 In 1 / 4 Al 1 / 4 Ni 1 / 4 )C powder material. Compared with Example 4 in its preparation method, the difference lies in that in step (1), commercial TiC powder, Ti powder, Sn powder, In powder, Al powder, and Ni powder were prepared according to the molar ratio of TiC:Ti:Sn:In:Al:Ni = 0.9:1:0.25:0.25:0.25:0.25.

[0075] The phase analysis of the dried powder was carried out by XRD, and the results are as Figure 3As shown. The XRD pattern shows that no diffraction peaks of typical MAX phases are detected in the sample. The impurities are TiC, Ni, InNi2, and TiNi2Al. Severe phase separation occurs, and there is a problem of In being consumed due to the reaction between Ni and In. At the same time, the thermodynamically competing phase TiNi2Al also prevents the formation of MAX phases.

[0076] Table 1 EDS composition detection results of the samples prepared in Examples 3-5

[0077] sample Ti Al Sn In Bi Ag C Ti / A <![CDATA[Ti2(Sn 1 / 3 In 1 / 3 Al 1 / 3 )C(Example 3)]]> 44.92 7.45 7.33 7.12 － － 33.18 2.05 <![CDATA[Ti2(Sn 1 / 4 In 1 / 4 Al 1 / 4 Bi 1 / 4 )C(Example 4)]]> 40.69 5.48 6.26 6.40 2.43 － 38.74 1.98 <![CDATA[Ti2(Sn 1 / 5 In 1 / 5 Al 1 / 5 Bi 1 / 5 Ag 1 / 5 )C(Example 5)]]> 38.48 4.57 4.49 4.36 3.93 2.69 41.48 1.92

Claims

1. A MAX-phase multi-component A-site solid solution, characterized in that, For a binary A-site solid solution, its chemical formula is Ti2(X+Y)C, where the X element is selected from Sn or In, and the Y element is selected from one of Ge, Cu, Si, Fe, Ga, Bi, Ag; For a ternary or higher A-site solid solution, its chemical formula is Ti2(SnIn+Z)C, where the Z element is selected from at least one of Al, Ge, Cu, Si, Fe, Ga, Bi, Ag.

2. The preparation method of the MAX phase multi-component A-site solid solution according to claim 1, characterized in that, It includes the following steps: (1) Mix TiC, Ti, and powders of two or more A-site elements to obtain a mixed powder; (2) Press the mixed powder into a green body; (3) Under a protective atmosphere, first perform the "preset vacancy" step, that is, first sinter the green body in a certain temperature range, and use Sn and / or In to form a primary MAX-phase lattice with a high concentration of A-site vacancies; then perform the "isomorphic occupation" step, that is, then sinter in a higher temperature range, and promote the diffusion of other A-site elements into the A vacancies through liquid-phase mass transfer; after sintering is completed, the MAX-phase multi-component A-site solid solution is obtained.

3. The preparation method of the MAX phase multi-component A-site solid solution according to claim 2, wherein, In step (1), TiC, Ti, and powders of two A-site elements are mixed; the two A-site elements include X and Y, where the X element is selected from Sn or In, and the Y element is selected from one of Ge, Cu, Si, Fe, Ga, Bi, Ag.

4. The preparation method of the MAX phase multi-component A-site solid solution according to claim 2, characterized in that, In step (1), TiC, Ti, and powders of more than two A-site elements are mixed; the more than two A-site elements include Sn and In, and Z, where the Z element is selected from at least one of Al, Ge, Cu, Si, Fe, Ga, Bi, Ag.

5. The preparation method of the MAX-phase binary A-site solid solution according to claim 3, characterized in that, The mixing molar ratio is TiC:Ti:X:Y = 0.9:1:x:(1 - x), where x ≥ 0.

4.

6. The preparation method of the high-entropy A-site solid solution in the MAX phase according to claim 4, characterized in that, The mixing molar ratio is TiC:Ti:(Sn + In):Z = 0.9:1:x:(1 - x), where x ≥ 0.

4.

7. The preparation method of the MAX phase multi-element A-site solid solution according to claim 2, characterized in that In step (3), first sinter the green body at a temperature of 950 - 1050 °C for 20 - 30 min, and then sinter at a temperature of 1150 - 1450 °C for 0.5 - 2 h.

8. The preparation method of the MAX phase multi-element A-site solid solution according to claim 7, characterized in that, In step (3), when sintering at a temperature of 950 - 1050 °C, the heating rate is 5 - 10 °C / min; when sintering at 1150 - 1450 °C, the heating rate is 2 - 5 °C / min; after sintering is completed, cool to 200 - 300 °C at a cooling rate of 2 - 10 °C / min, and then cool naturally in the furnace to obtain the product.

9. The preparation method of the MAX-phase multi-element A-site solid solution according to claim 2, characterized in that, In step (2), the mixed powder is made into a green body under a certain pressure and pressure holding time, the pressure is 0 - 50 MPa, and the pressure holding time is 0 - 10 min.

10. Application of the MAX-phase multi-component A-site solid solution according to claim 1 in the fields of high-speed rail, ocean, electronic packaging, nuclear energy, aerospace, and medicine.

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