Two-dimensional cr2c and a preparation method thereof

Abstract

The application provides a two-dimensional Cr2C and a preparation method thereof, wherein the preparation method comprises the following steps: step S1, providing a Cr2(AlLi)C solid solution; and step S2, de-alloying AlLi in the Cr2(AlLi)C solid solution to generate the two-dimensional Cr2C. According to the preparation method of the application, the reaction reagents can be selected from water, an aqueous alkali metal halide solution, methanol or a methanol aqueous solution and the like, which are clean and environmentally friendly, and the preparation method has the characteristics of environmental protection, economy and high efficiency, and is different from the acid etching method which is seriously polluted and high in cost. In addition, by using different etching solutions, the types of functional groups of the two-dimensional Cr2C can be selected. In addition, the two-dimensional Cr2C prepared by the preparation method of the embodiment of the application has a smaller thickness, oligolayer Cr2C enes can be obtained, and two-dimensional Cr2C with an accordion shape can also be obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of new materials, and particularly relates to a two-dimensional Cr2C and a preparation method thereof. BACKGROUND

[0002] MAX phase is a ternary layered compound, in which M is a transition metal element, A is a group IIIA or VIA element, and X is C or N. It has high conductivity, thermal conductivity and certain high-temperature plasticity similar to metal materials, and also has high modulus, low density and excellent tribological properties like ceramics.

[0003] MXene is a new two-dimensional material obtained by selectively etching A atoms of MAX phase by HF. In addition to the excellent performance of traditional two-dimensional materials, MXene also has high conductivity, good lubricity and electromagnetic properties due to its special quantum effect, which has attracted widespread attention in the academic field. MXene has been widely used in energy storage, catalysis, lubrication, sensors, water purification and composite materials, and has achieved certain results and progress. MXene can be directly used as a double-layer capacitor electrode material, or can be compounded with other pseudo-capacitive materials as a conductive matrix to prepare a hybrid capacitor electrode material.

[0004] Among them, two-dimensional Cr2C graphene-like material is predicted to have ferromagnetism, making it have excellent application value in the fields of electronic devices, magnetic liquids, magnetic storage materials, etc. However, so far, there are few reports on the preparation method of two-dimensional Cr2C graphene-like material, and the only report is prepared by HF etching method. However, this preparation method has the problems of complex process, serious pollution, high energy consumption, and great danger. SUMMARY

[0005] Therefore, the application aims to provide a new, clean, efficient, cheap and environmentally friendly preparation method of two-dimensional Cr2C.

[0006] The application also aims to provide a two-dimensional Cr2C material with single-layer, multiple and few defects.

[0007] To solve the above technical problems, the application adopts the following technical solutions:

[0008] According to the first aspect of the application, a preparation method of two-dimensional Cr2C is provided, comprising the following steps:

[0009] Step S1, providing a Cr2(AlLi)C solid solution;

[0010] Step S2, de-alloying AlLi in the Cr2(AlLi)C solid solution to generate the two-dimensional Cr2C.

[0011] Further, the step S1 comprises:

[0012] Step S11, weighing Cr powder, AlLi alloy powder and graphite powder according to the molar ratio of Cr:Al:C 2:(1.2-1.6):1;

[0013] Step S12, mixing various raw materials to obtain a mixed powder;

[0014] Step S13, pressing the mixed powder into a green body;

[0015] Step S14, sintering the green body to obtain the Cr2(AlLi)C solid solution.

[0016] Further, the atomic percentage of Li in the AlLi alloy powder is 10%-60%.

[0017] Further, the step S12 comprises:

[0018] The various raw materials weighed in step S11 are put into a ball mill, and ball milling is carried out at a ball-to-material ratio of (2-20):1 and a rotation speed of 90-300 rpm for 5-12 hours;

[0019] The powder after ball milling is sieved with a 20-400 mesh sieve to obtain the mixed powder.

[0020] Further, the step S13 comprises:

[0021] The mixed powder is laid on the bottom of a cold pressing mold with a thickness of 10-20 mm, and cold pressing is carried out at 120-200 MPa to obtain the green body.

[0022] Further, the step S14 comprises:

[0023] Rising at a temperature rising rate of 5-20 ℃ / min to 1200-1400 ℃ under vacuum or inert gas atmosphere, and keeping the temperature for 5-20 min to obtain the Cr2(AlLi)C solid solution.

[0024] Further, the step S2 comprises:

[0025] The Cr2(AlLi)C solid solution is dispersed in an etching solution to make AlLi of the Cr2(AlLi)C solid solution undergo hydrolysis reaction to perform AlLi dealloying, thereby generating the two-dimensional Cr2C.

[0026] The etching solution comprises water, an aqueous solution of an alkali metal halide, methanol or an aqueous methanol solution, and the alkali metal halide comprises any one or more of sodium fluoride, potassium fluoride, sodium chloride and potassium chloride.

[0027] Further, the preparation method further comprises the following steps:

[0028] Step S3, the reaction solution of step S2 is left for 2-4 hours, the supernatant and the bottom turbidity in the reaction solution are extracted;

[0029] Step S4, the supernatant is suction filtered to obtain a two-dimensional Cr2C crude product.

[0030] Further, the preparation method further comprises the following steps:

[0031] Step S5, an aqueous solution of sodium fluoride is added to the two-dimensional Cr2C crude product, and then water washing is performed to obtain a two-dimensional Cr2C material, the two-dimensional Cr2C material being an oligolayer two-dimensional Cr2C.

[0032] Further, the preparation method further comprises the following steps:

[0033] Step S6, the bottom turbidity is suction filtered, and an aqueous solution of sodium fluoride is added to the precipitate obtained by suction filtration, and then water washing is performed to obtain a two-dimensional Cr2C mixed material, the two-dimensional Cr2C mixed material comprising an accordion-shaped two-dimensional Cr2C and an oligolayer Cr2AlC.

[0034] According to a second aspect of the present application, a two-dimensional Cr2C prepared by the preparation method of any of the above embodiments of the first aspect is provided.

[0035] The above technical solution of the present application has at least one of the following beneficial effects:

[0036] According to the preparation method of the present application, unlike the acid etching method which is seriously polluted and high in cost, water, an aqueous solution of an alkali metal halide, methanol or a methanol aqueous solution, etc. can be selected as the reactant, and the preparation method has the characteristics of environmental protection, economy and high efficiency;

[0037] In the preparation method of the two-dimensional Cr2C, by using different etching liquids, the type of functional groups of the two-dimensional Cr2C can be artificially selected, for example, when water, methanol or a methanol aqueous solution is used as the etching liquid, the obtained two-dimensional Cr2C can be modified with OH - functional groups; when an aqueous solution of sodium fluoride is used as the etching liquid, the obtained two-dimensional Cr2C can be modified with OH - , F - functional groups; and when an aqueous solution of sodium chloride is used as the etching liquid, the obtained two-dimensional Cr2C can be modified with OH - , Cl - functional groups;

[0038] According to the preparation method of the embodiment of the present application, the AlLi alloy prepared industrially can be selected as the raw material for preparing the Cr2(AlLi)C, and the purity of the AlLi alloy does not need to be considered, so that the preparation cost is significantly reduced, and economic advantages are achieved.

[0039] In addition, the two-dimensional Cr2C prepared by the preparation method of the embodiment of the present application has a smaller thickness, and can obtain oligolayer Cr2C ene and accordion-shaped two-dimensional Cr2C. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 XRD patterns of the Cr2(AlLi)C solid solution and the two-dimensional Cr2C prepared by different embodiments are shown;

[0041] Figure 2 A scanning electron microscope image of the Cr2(AlLi)C solid solution is shown;

[0042] Figure 3 A scanning electron microscope image of the two-dimensional Cr2C according to the embodiment of the present application is shown, wherein (a) shows a scanning electron microscope image of the two-dimensional Cr2C obtained by the embodiment 1, and (b) shows a scanning electron microscope image of the two-dimensional Cr2C obtained by the embodiment 2. DETAILED DESCRIPTION

[0043] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the present application will be described clearly and completely in combination with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the described embodiments of the present application, all other embodiments obtained by those skilled in the art belong to the scope of protection of the present application.

[0044] First, the preparation method of the two-dimensional Cr2C according to the embodiment of the present application will be described in detail.

[0045] The preparation method of the two-dimensional Cr2C according to the embodiment of the present application comprises the following steps.

[0046] Step S1, providing a Cr2(AlLi)C solid solution.

[0047] The Cr2(AlLi)C solid solution can be commercially available or prepared by the following method.

[0048] In some embodiments of the present application, the step S1 comprises:

[0049] Step S11, weighing the Cr powder, the AlLi alloy powder and the graphite powder according to the molar ratio of Cr:Al:C of 2:(1.2-1.6):1.

[0050] It should be noted that in the selection of raw materials for preparing Cr2(AlLi)C, an industrially prepared AlLi alloy can be selected, and the purity of the AlLi alloy does not need to be considered, so that the preparation cost is significantly reduced, and economic advantages are obtained.

[0051] In addition, the atomic percentage of Li in the AlLi alloy powder is 10% to 60%. For example, commercially available AlLi alloy powder, AlLi20 alloy powder, or a mixture thereof, etc. can be used.

[0052] In step S12, various raw materials are mixed to obtain a mixed powder.

[0053] In some embodiments of the present application, the step S12 comprises:

[0054] The various raw materials weighed in step S11 are placed in a ball mill at a ball-to-material ratio of 2-20:1, and ball milling is performed at a rotation speed of 90-300 rpm for 5-12 hours.

[0055] The powder after ball milling is sieved with a 20-400 mesh sieve to obtain the mixed powder.

[0056] Ball milling can uniformly mix the various raw materials. In addition, sieving with a 20-400 mesh sieve can obtain the mixed powder with uniform particle size and without large particles or agglomerates, which is beneficial to improve the quality of the prepared Cr2(AlLi)C solid solution.

[0057] In step S13, the mixed powder is pressed into a green body.

[0058] In some embodiments of the present application, the step S13 comprises:

[0059] The mixed powder is laid on the bottom of a cold pressing mold with a thickness of 10-20 mm, and cold pressing is performed under the condition of 120-200 MPa to obtain the green body. Compaction can reduce the reaction steric hindrance of solid phase reaction and promote the progress of solid phase reaction.

[0060] In step S14, the green body is sintered to obtain the Cr2(AlLi)C solid solution.

[0061] In some embodiments of the present application, the step S14 comprises:

[0062] In a vacuum or inert gas atmosphere, the temperature is raised to 1200-1400°C at a temperature raising rate of 5-20°C / min, and the temperature is maintained for 5-20 min to obtain the Cr2(AlLi)C solid solution.

[0063] For example, nitrogen, argon, and preferably argon can be used as the inert gas atmosphere.

[0064] Step S2, dealloying AlLi in the Cr2(AlLi)C solid solution to generate the two-dimensional Cr2C.

[0065] That is, after obtaining the Cr2(AlLi)C solid solution, AlLi needs to be dealloyed to obtain the target product two-dimensional Cr2C.

[0066] In some embodiments of the present application, the step S2 comprises:

[0067] The Cr2(AlLi)C solid solution is dispersed in an etching solution to cause AlLi in the Cr2(AlLi)C solid solution to undergo a hydrolysis reaction to dealloy AlLi and generate the two-dimensional Cr2C.

[0068] The etching solution comprises water, an aqueous solution of an alkali metal halide, methanol, or an aqueous methanol solution, and the alkali metal halide comprises any one or more of sodium fluoride, potassium fluoride, sodium chloride, and potassium chloride.

[0069] That is, according to the preparation method of the present application, the etching solution can be selected as a reaction substance, which is clean and environmentally friendly, and has the characteristics of environmental protection, economy, and high efficiency.

[0070] In addition, in the preparation method of the two-dimensional Cr2C, by using different etching solutions, the type of functional groups of the two-dimensional Cr2C can be artificially selected, for example, when water, methanol, or an aqueous methanol solution is used as the etching solution, the obtained two-dimensional Cr2C can be modified with OH - functional groups; when an aqueous sodium fluoride solution is used as the etching solution, the obtained two-dimensional Cr2C can be modified with OH - , F - functional groups; and when an aqueous sodium chloride solution is used as the etching solution, the obtained two-dimensional Cr2C can be modified with OH- and Cl- functional groups.

[0071] In some embodiments of the present application, the preparation method can further comprise the following steps:

[0072] Step S3, the reaction solution of step S2 is left to stand for 2-4 hours, and supernatant and bottom turbidity are extracted therefrom;

[0073] Step S4, the supernatant is suction filtered to obtain a two-dimensional Cr2C crude product.

[0074] In some embodiments, the preparation method can further comprise the following steps:

[0075] Step S5, adding an aqueous solution of sodium fluoride to the two-dimensional Cr2C crude product, and then washing with water to obtain a two-dimensional Cr2C material, which is an oligolayer two-dimensional Cr2C.

[0076] That is, by collecting the supernatant (dispersing fine solid particles), and by suction filtration to obtain the fine particles in the supernatant, and then by adding an aqueous solution of sodium fluoride to the fine particles to react with Al(OH)3 to convert into slightly soluble Na3AlF6 (0.25 g of Na3AlF6 is dissolved in 1 L of water at 20°C), and then by washing with a large amount of water to dissolve and remove the Na3AlF6, an oligolayer two-dimensional Cr2C can be obtained.

[0077] In some other embodiments, the preparation method can further include the following steps:

[0078] Step S6, suction filtering the bottom turbidity, and adding an aqueous solution of sodium fluoride to the precipitate obtained by suction filtration, and then washing with water to obtain a two-dimensional Cr2C mixed material, which includes an accordion-shaped two-dimensional Cr2C and an oligolayer Cr2AlC.

[0079] That is, for the bottom turbidity (containing larger particles relative to the supernatant) obtained by standing and layering, by suction filtration to remove the liquid and then adding an aqueous solution of sodium fluoride to react with Al(OH)3 to convert into slightly soluble Na3AlF6 (0.25 g of Na3AlF6 is dissolved in 1 L of water at 20°C), and then by washing with a large amount of water to dissolve and remove the Na3AlF6, a large amount of accordion-shaped two-dimensional Cr2C and a small amount of oligolayer Cr2AlC can be obtained.

[0080] In summary, by standing and layering, the supernatant can be treated to obtain an oligolayer two-dimensional Cr2C, and the bottom turbidity can be treated to obtain a mixture of accordion-shaped two-dimensional Cr2C and oligolayer Cr2AlC.

[0081] Next, the preparation method according to the present application and the two-dimensional Cr2C prepared thereby will be further described in conjunction with specific embodiments.

[0082] First, a Cr2(AlLi)C solid solution is prepared as one of the reactants.

[0083] The specific steps are as follows:

[0084] (1) 27.62 g of Cr powder, 8.54 g of AlLi20, and 3.19 g of graphite powder are weighed and placed in a ball milling jar, and maroon balls are put in according to a ball-to-material ratio of 5:1. The ball milling jar is placed on a roller ball mill at a rotation speed of 100 r / min for 10 h to mix uniformly.

[0085] (2) The ball-milled powder is sieved with a 20-mesh sieve.

[0086] (3) 13.12 g of the powder obtained in step (2) is laid on the bottom of a mold with a diameter of 20 mm to obtain a 15-mm-thick powder, and cold-pressed at a pressure of 150 MPa.

[0087] (4) Sintering is performed by pressureless sintering.

[0088] Specific parameters are as follows: under a high-purity argon atmosphere, the temperature is raised to 1300°C at a rate of 15°C / min, and the temperature is kept constant for 10 min before furnace cooling; the temperature is measured by infrared temperature measurement; and after cooling, Cr2(AlLi)C is obtained.

[0089] The Cr2(AlLi)C solid solution prepared above is used as one of the reactants, and different etching solutions are used as the other reactant to prepare two-dimensional Cr2C.

[0090] Example 1: Water is used as the etching solution to prepare two-dimensional Cr2C

[0091] The specific steps are as follows:

[0092] (1) 5 g of the Cr2(AlLi)C prepared above is placed in an Erlenmeyer flask containing 100 ml of pure water. The Erlenmeyer flask is placed on an ultrasonic generator to perform ultrasonic oscillation at 50 kHz to disperse the Cr2(AlLi)C, and the reaction is performed for 2 h.

[0093] (2) The reaction solution is left to stand for 2 h, and the supernatant and the bottom turbidity are extracted.

[0094] (3) The supernatant is subjected to suction filtration to obtain a two-dimensional Cr2C crude product.

[0095] (4) 100 ml of a saturated NaF solution is added to the two-dimensional Cr2C crude product, and the mixture is washed with a large amount of water (10 L) to obtain pure oligolayer two-dimensional Cr2C with OH- functional groups.

[0096] (5) The bottom turbidity obtained in step (2) is subjected to suction filtration, and an aqueous sodium fluoride solution is added to the precipitate obtained by suction filtration, followed by water washing to obtain a large amount of accordion-shaped two-dimensional Cr2C and a small amount of thin-layer Cr2AlC.

[0097] Example 2: An aqueous NaF solution is used as the etching solution to prepare two-dimensional Cr2C

[0098] The specific steps are as follows:

[0099] (1) Take the Cr2(AlLi)C prepared above 5g, and put it into a conical flask containing 100ml saturated NaF aqueous solution. Put the conical flask on the ultrasonic generator to oscillate at 50kHz, so as to disperse it, and react for 2h.

[0100] (2) Let the reaction liquid above stand for 2h, and extract the supernatant and the bottom turbidity.

[0101] (3) Perform suction filtration on the supernatant, and wash it with a large amount of water (10L) to obtain pure oligolayer two-dimensional Cr2C with functional groups OH - , F - .

[0102] (4) Perform suction filtration on the bottom turbidity obtained in (2), and add an aqueous solution of sodium fluoride to the precipitate obtained by suction filtration, and then perform water washing to obtain a large amount of accordion-shaped two-dimensional Cr2C and a small amount of thin-layer Cr2AlC.

[0103] The Cr2(AlLi)C solid solution prepared above, the oligolayer two-dimensional Cr2C obtained in step (4) of Example 1, and the oligolayer two-dimensional Cr2C obtained in step (3) of Example 2 are respectively subjected to XRD testing, and their microstructures are observed by scanning electron microscopy, and the results are shown in Figures 1 to 3 , wherein the XRD pattern of Cr2C is x MXene is the chemical formula and English abbreviation of two-dimensional Cr2C, Figure 2 is the SEM photograph of Cr2(AlLi)C, Figure 3 (a) is the SEM photograph of two-dimensional Cr2C after the reaction of Cr2(AlLi)C with pure water, Figure 3 (b) is the SEM photograph of two-dimensional Cr2C after the reaction of Cr2(AlLi)C with an aqueous solution of NaF.

[0104] The above describes the preferred embodiments of the present application, and it should be noted that, for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing two-dimensional Cr2C, characterized in that, Includes the following steps: Step S1, providing a Cr2(AlLi)C solid solution; Step S2 involves dealloying the Li and Al in the Cr2(AlLi)C solid solution to generate the two-dimensional Cr2C. Step S2 includes: The Cr2(AlLi)C solid solution is dispersed in an etching solution to allow the Li and Al in the Cr2(AlLi)C solid solution to undergo hydrolysis, thereby performing Li and Al dealloying to generate the two-dimensional Cr2C. The etching solution includes water, an aqueous solution of an alkali metal halide, methanol, or an aqueous solution of methanol, wherein the alkali metal halide includes any one or more of sodium fluoride, potassium fluoride, sodium chloride, and potassium chloride. Step S3: Let the reaction solution from step S2 stand for 2-4 hours, and extract the supernatant and the bottom turbid liquid. Step S4: The supernatant is filtered to obtain crude two-dimensional Cr2C. The preparation method further includes: Step S5: Add an aqueous solution of sodium fluoride to the crude two-dimensional Cr2C product, and then wash with water to obtain a two-dimensional Cr2C material, wherein the two-dimensional Cr2C material is an oligolayer two-dimensional Cr2C. or, Step S6: The bottom turbid liquid is filtered, and an aqueous solution of sodium fluoride is added to the precipitate obtained by filtration. After washing with water, a two-dimensional Cr2C mixed material is obtained, which includes accordion-shaped two-dimensional Cr2C and oligolayer Cr2AlC.

2. The preparation method according to claim 1, characterized in that, Step S1 includes: Step S11: Weigh out Cr powder, AlLi alloy powder and graphite powder according to the molar ratio of Cr:Al:C 2:(1.2-1.6):1; Step S12: Mix the various raw materials to obtain a mixed powder; Step S13: Press the mixed powder into a blank; Step S14: Sinter the green body to obtain the Cr2(AlLi)C solid solution.

3. The preparation method according to claim 2, characterized in that, The atomic percentage of Li in the AlLi alloy powder is 10%-60%.

4. The preparation method according to claim 2, characterized in that, Step S12 includes: Place the various raw materials weighed in step S11 into a ball mill and ball mill them at a ball-to-material ratio of (2-20):1 for 5-12 hours at a speed of 90-300 rpm. The ball-milled powder is sieved through a 20-400 mesh sieve to obtain the mixed powder.

5. The preparation method according to claim 2, characterized in that, Step S13 includes: The mixed powder is placed on the bottom of a cold pressing mold with a thickness of 10-20 mm, and then cold-pressed at 120-200 MPa to obtain the blank.

6. The preparation method according to claim 2, characterized in that, Step S14 includes: The Cr2(AlLi)C solid solution is obtained by heating to 1200-1400℃ at a heating rate of 5-20℃ / min under vacuum or inert gas atmosphere and holding at that temperature for 5-20min.

7. A two-dimensional Cr2C prepared by the preparation method according to any one of claims 1 to 6.

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