阅读说明：本技术 层状碳氮化合物刻蚀过程的扫描电镜原位观测制样方法 (Scanning electron microscope in-situ observation sample preparation method for lamellar carbon nitride etching process ) 是由 王双宝 刘玉莹 魏波 韩相彬 董泽健 胡万彪 于 2021-08-06 设计创作，主要内容包括：本发明公开了一种层状碳氮化合物刻蚀过程的扫描电镜原位观测制样方法,包括：1)在显微镜下,用粘结剂粘取碳氮化合物样品；2)烤干后冲洗掉没有粘牢的样品并再次烤干；3)放到SEM中观察,找到适合的样品观察区,并记录样品位置,拍下SEM图；4)取出样品,将HF水溶液倒入塑料离心管中,将粘有样品的铜网放入到烧杯中反应,记录反应时间；5)将塑料离心管的盖子盖住以避免HF水溶液挥发污染空气；6)取出样品,用超纯水以及无水乙醇清洗后,用烤灯烤干,再次到SEM中找到之前记录的样品位置,拍下SEM图；7)重复步骤4)至6),直到实验结束。本发明制备过程在常温下进行,操作简单,适合于所有层状过渡金属碳氮化合物材料。(The invention discloses a scanning electron microscope in-situ observation sample preparation method for a lamellar carbon and nitrogen compound etching process, which comprises the following steps: 1) adhering a carbon-nitrogen compound sample by using a binder under a microscope; 2) after baking, washing off the sample which is not firmly adhered, and baking again; 3) observing in the SEM to find a proper sample observation area, recording the position of the sample, and taking down an SEM picture; 4) taking out the sample, pouring the HF aqueous solution into a plastic centrifuge tube, putting the copper net stuck with the sample into a beaker for reaction, and recording the reaction time; 5) covering the cover of the plastic centrifuge tube to prevent the HF aqueous solution from volatilizing to pollute the air; 6) taking out the sample, cleaning the sample by using ultrapure water and absolute ethyl alcohol, drying the sample by using a baking lamp, finding the position of the sample recorded in the SEM again, and taking down an SEM picture; 7) repeating steps 4) to 6) until the experiment is finished. The preparation process is carried out at normal temperature, is simple to operate and is suitable for all lamellar transition metal carbon nitride compound materials.)

1. A scanning electron microscope in-situ observation sample preparation method for a lamellar carbon and nitrogen compound etching process is characterized by comprising the following steps:

coating a binder on one end of a copper mesh under the observation of an optical microscope, and dipping a small amount of carbon and nitrogen compound samples to coat on one surface with the binder;

step (2), baking with a baking lamp, then washing off the sample which is not firmly adhered with absolute ethyl alcohol, and baking with the baking lamp again;

step (3), the baked sample is placed in a scanning electron microscope for observation, a proper sample observation area is found, the position of the sample is recorded, and an SEM picture is taken;

step (4), after the sample is taken out, pouring the HF aqueous solution into a plastic centrifuge tube, then putting the copper mesh adhered with the sample into a beaker for reaction, and recording the reaction time;

step (5), in the reaction process, covering a cover of the plastic centrifuge tube to prevent the HF aqueous solution from volatilizing to pollute air;

step (6), after the reaction is finished, taking out the sample, cleaning the sample by using ultrapure water and absolute ethyl alcohol, baking the sample by using a baking lamp, finding the position of the sample recorded in the scanning electron microscope again, and taking down an SEM picture;

and (7) repeating the step (4), the step (5) and the step (6) until the experiment is finished.

2. The scanning electron microscope in-situ observation sample preparation method for the etching process of the layered carbon nitride compound as claimed in claim 1, wherein the concentration of the HF aqueous solution is 40%.

3. The scanning electron microscope in-situ observation sample preparation method for the lamellar carbon nitrogen compound etching process according to claim 1, wherein the baking time by a baking lamp is 1-2 min.

4. The scanning electron microscope in-situ observation sample preparation method for the etching process of the layered carbon nitride compound as claimed in claim 1, wherein the binder is an acid-resistant binder.

5. The scanning electron microscope in-situ observation sample preparation method for the lamellar carbon nitride etching process according to claim 4, characterized in that the acid-resistant binder is polytetrafluoroethylene concentrated dispersion or polyvinylidene fluoride emulsion.

6. The scanning electron microscope in-situ observation sample preparation method for the etching process of the layered carbon nitride compound as claimed in claim 1, wherein the copper mesh is a coordinate copper mesh or a duplex copper mesh.

7. The scanning electron microscope in-situ observation sample preparation method for the etching process of the layered carbon nitride compound according to claim 5, wherein the concentration of the polytetrafluoroethylene concentrated dispersion liquid is 60 wt%.

8. The scanning electron microscope in-situ observation sample preparation method for the etching process of the layered carbon nitrogen compound as claimed in any one of claims 1 to 7, wherein the carbon nitrogen compound is Ti₃AlC₂、Ti₂AlC、Ti₃SiC₂And V₂Any one of AlN.

Technical Field

The invention relates to the field of preparation of a two-dimensional layered transition metal carbon nitrogen compound material MXene, in particular to a scanning electron microscope in-situ observation sample preparation method in a layered carbon nitrogen compound etching process.

Background

Layered hexagonal ternary atomic MAX phase compound (M) synthesized by transition metal and carbon nitride_n+1AX_n) Wherein M is a transition metal, a is predominantly a group 13 or 14 (i.e. group IIIA or IVA) element, X is C or N, and N ═ 1,2 or 3.

By selectively etching A layer atoms away from M_n+1AX_nThe two-dimensional layered material MXene is formed in the middle layer, and has wide application prospects in the aspects of Li ion batteries, supercapacitors, selective ion transmission membranes, biosensors, hydrogen storage materials, composite material reinforcing additives, electromagnetic interference shielding, water purification, lubrication, chemical catalysis and the like due to the good conductivity, hydrophilicity, mechanical strength and chemical stability of the MXene.

The conventional preparation of layered transition metal carbonitride materials is by selective etching away of the a layer atoms using different etchants. The etchants that have been reported are mainly: hydrofluoric acid (HF) aqueous solution, hydrochloric acid (HCl) + lithium fluoride (LiF) solution, ammonium bifluoride (NH)₄HF₂) Solution and ammonium fluoride (NH)₄F) Fluorine-containing solution such as solution, and 27.5M aqueous sodium hydroxide (NaOH) solution containing no fluorine [ Li T, et al, Angewandte Chemie International Edition,2018,57(21)]Aqueous hydrochloric acid solution [ Sun W, et al. journal of Materials Chemistry A,2017:10.1039.C7TA05574A]And Lewis acids [ Li Y, et al. Nature Materials,2020,19(8)]And the like. At present, MXene materials are analyzed by methods such as SEM, XRD, XPS, Raman spectrum and the like after etching for different time in the process of observing etching conditions or understanding the etching process. However, the MXene in-situ etching process is still not intuitively obtained, so that the dynamic process and the corresponding etching mechanism thereof cannot be known, the optimization of the MXene material etching process and the regulation and control of the etching microstructure are greatly hindered, and the development of the method for etching the MAX phase material by the in-situ scanning electron microscope has important scientific significance and practical value.

Currently, the etching by using an etchant is still the most common method for preparing MXene materials, the dynamic process of the method is explored by adopting an ex-situ etching method, the dynamic process usually needs longer etching time (such as 72 hours) and stronger etchant concentration to enable the MXene materials to reach the full etching degree, the efficiency is very low, the safety is lower, the operation is complex, and the dosage of the etchant is larger. In addition, the ex-situ method cannot obtain initial crack initiation and other crack formation processes on the same particle, so that a dynamic process and a corresponding micro mechanism in the material etching process are difficult to obtain, and finally, the optimization of the etching process and the research and development of a design and regulation method of a layered material etching microstructure are hindered to a great extent. The etching behavior of the two-dimensional layered material sample is observed through the in-situ SEM, so that the etching process can be intuitively and efficiently understood and the etching microscopic mechanism can be obtained. According to the relevant data documents, no report about a research method for preparing in-situ scanning etching lamellar structure carbon nitrogen compounds at room temperature is found.

Disclosure of Invention

The invention relates to a scanning electron microscope in-situ observation sample preparation method for a lamellar carbon and nitrogen compound etching process, which aims to solve the technical problems that:

(1) the method is suitable for the efficient preparation of in-situ samples of all layered transition metal carbon nitrogen compound materials;

(2) can be widely applied to different etching agents.

The present invention provides a general concept for solving the above technical problems, including:

(1) as a method of fixing the sample, an adhesive is used, wherein the adhesive may be: acid-resistant binders such as polytetrafluoroethylene concentrated dispersion (60 wt%), polyvinylidene fluoride emulsion, etc.;

(2) the position of the sample can be better positioned by using a copper net as a carrier of the sample, wherein the copper net can be: coordinate copper mesh, duplex copper mesh, etc.;

(3) in-situ etching a sample by using a small-caliber small-capacity plastic tubular container with a seal;

(4) and (3) carrying out in-situ etching observation on the samples prepared by the methods (1) and (2) by using a scanning electron microscope.

The technical scheme of the invention is as follows:

a scanning electron microscope in-situ observation sample preparation method for a lamellar carbon and nitrogen compound etching process comprises the following steps:

(1) coating the adhesive on one end of the copper mesh carefully under the observation of an optical microscope, dipping a small amount of sample by using a toothpick, and coating the adhesive on one surface;

(2) baking for 1-2 min by using a baking lamp to dry the sample, then washing the sample which is not firmly adhered by using absolute ethyl alcohol, and baking for 1-2 min by using the baking lamp again;

(3) putting the baked sample into a scanning electron microscope for observation, finding a proper sample observation area, recording the position of the sample, and taking an SEM picture;

(4) after taking out the sample, pouring 2mL of HF aqueous solution (with the concentration of 40%) into a 4mL plastic centrifuge tube, then putting the copper mesh adhered with the sample into a beaker for reaction, and recording the reaction time;

(5) in the reaction process, in order to avoid air pollution caused by volatilization of the HF aqueous solution, a cover of the plastic centrifuge tube is covered;

(6) after the reaction is finished, taking out the sample, cleaning the sample by using ultrapure water and absolute ethyl alcohol, placing the sample under a baking lamp for baking for 1-2 min to dry the sample, finding the position of the sample recorded in the scanning electron microscope again, and taking an SEM picture;

(7) and (5) repeating the steps (4) to (6) until the experiment is finished.

The mechanism and the beneficial effects of the invention are as follows:

(1) the invention provides a preparation method of a scanning electron microscope in-situ observation sample, which can intuitively obtain the structural change of a layered transition metal carbon nitrogen compound material in the etching process;

(2) the application range is wide, and the method is suitable for all layered transition metal carbon nitride compound materials;

(3) in the experiment, a small amount of toxic HF aqueous solution is used as an etching agent, the operation process is safe and environment-friendly, and the working efficiency is improved;

(4) the etching reaction process can be carried out at room temperature, the equipment is easy to obtain, and the experimental operation is simple.

(5) The sample preparation method has high success rate and high experimental efficiency.

Drawings

FIG. 1 is a process of the present invention for converting Ti₃AlC₂In-situ SEM images of 0,1, 2 and 3min etching time in HF solution.

FIG. 2 shows Ti in the condition that the etching temperature is room temperature and the etching time is respectively 1min apart₃AlC₂SEM image of (d).

Detailed Description

The following detailed description of the present invention is provided in connection with the accompanying drawings and examples, but it should be understood that the scope of the present invention is not limited to the specific embodiments.

As shown in FIG. 1, adding Ti₃AlC₂And (3) etching in an HF solution for 0,1, 2 and 3min respectively, wherein the positions of the samples can be positioned in a scanning electron microscope after each etching, and the specific positions of the samples can be accurately found out from the graphs (a-d). In addition, the appearance and the etching condition of the sample can be clearly observed. The information of the two aspects shows that the sample is fixed by using the adhesive, and the sample preparation on the copper mesh can quickly and accurately position the sample, so that an effective method for in-situ scanning etching is realized.

As shown in FIG. 2, adding Ti₃AlC₂Etching in HF solution for 0,1, 2 and 3min, and observing the etching condition of other sample particles. It is apparent from the figure that the position of the sample particles hardly moved after each etching, indicating that the present invention can achieve a stable sample fixation. The etching is carried out every 1min, and the crack change condition of the sample surface can be clearly observed from the graphs (a-d), so that the purpose of experiment is achieved, and the practicability of the invention is further verified.

Example 1

Preparation of Ti₃AlC₂The method for in-situ scanning etching comprises the following steps:

(1) coating polytetrafluoroethylene concentrated dispersion as binder under observation of optical microscopeDipping a small amount of Ti on one end of the copper net by using a toothpick₃AlC₂Coating on one side with the adhesive;

(2) baking for 1-2 min by using a baking lamp to dry the sample, then washing the sample which is not firmly adhered by using absolute ethyl alcohol, and baking for 1-2 min by using the baking lamp again;

(3) putting the baked sample into a scanning electron microscope for observation, finding a proper sample observation area, recording the position of the sample, and taking an SEM picture;

(4) after taking out the sample, pouring 2mL of HF aqueous solution (with the concentration of 40%) into a 4mL plastic centrifuge tube, then putting the copper mesh adhered with the sample into a beaker for reaction, and recording the reaction time;

(5) in the reaction process, in order to avoid air pollution caused by volatilization of the HF aqueous solution, a cover of the plastic centrifuge tube is covered;

(6) after the reaction is finished, taking out the sample, cleaning the sample by using ultrapure water and absolute ethyl alcohol, placing the sample under a baking lamp for baking for 1-2 min to dry the sample, finding the position of the sample recorded in the scanning electron microscope again, and taking an SEM picture;

(7) and (5) repeating the steps (4) to (6) until the experiment is finished.

Example 2

Preparation of Ti₃AlC₂The method for in-situ scanning etching comprises the following steps:

(1) under observation of an optical microscope, polyvinylidene fluoride emulsion as a binder is carefully coated on one end of a copper mesh, and a small amount of Ti is dipped by a toothpick₃AlC₂Coating on one side with the adhesive;

(2) baking for 1-2 min by using a baking lamp to dry the sample, then washing the sample which is not firmly adhered by using absolute ethyl alcohol, and baking for 1-2 min by using the baking lamp again; (ii) a

(3) Putting the baked sample into a scanning electron microscope for observation, finding a proper sample observation area, recording the position of the sample, and taking an SEM picture;

(4) after taking out the sample, pouring 2mL of HF aqueous solution (with the concentration of 40%) into a 4mL plastic centrifuge tube, then putting the copper mesh adhered with the sample into a beaker for reaction, and recording the reaction time;

(5) in the reaction process, in order to avoid air pollution caused by volatilization of the HF aqueous solution, a cover of the plastic centrifuge tube is covered;

(6) after the reaction is finished, taking out the sample, cleaning the sample by using ultrapure water and absolute ethyl alcohol, placing the sample under a baking lamp for baking for 1-2 min to dry the sample, finding the position of the sample recorded in the scanning electron microscope again, and taking an SEM picture;

(7) and (5) repeating the steps (4) to (6) until the experiment is finished.

Example 3

Preparation of Ti₂The AlC in-situ scanning etching method comprises the following steps:

(1) under observation of an optical microscope, the polytetrafluoroethylene concentrated dispersion is used as a binder to be carefully coated on one end of a copper mesh, and a small amount of Ti is dipped by a toothpick₂AlC coated on the surface with the binder; polyvinylidene fluoride emulsion

(2) Baking for 1-2 min by using a baking lamp to dry the sample, then washing the sample which is not firmly adhered by using absolute ethyl alcohol, and baking for 1-2 min by using the baking lamp again; (ii) a

(3) Putting the baked sample into a scanning electron microscope for observation, finding a proper sample observation area, recording the position of the sample, and taking an SEM picture;

(4) after taking out the sample, pouring 2mL of HF aqueous solution (with the concentration of 40%) into a 4mL plastic centrifuge tube, then putting the copper mesh adhered with the sample into a beaker for reaction, and recording the reaction time;

(5) in the reaction process, in order to avoid air pollution caused by volatilization of the HF aqueous solution, a cover of the plastic centrifuge tube is covered;

(6) after the reaction is finished, taking out the sample, cleaning the sample by using ultrapure water and absolute ethyl alcohol, placing the sample under a baking lamp for baking for 1-2 min to dry the sample, finding the position of the sample recorded in the scanning electron microscope again, and taking an SEM picture;

(7) and (5) repeating the steps (4) to (6) until the experiment is finished.

Example 4

Preparation of Ti₃SiC₂The method for in-situ scanning etching comprises the following steps:

(1) under observation of an optical microscope, the polytetrafluoroethylene concentrated dispersion is used as a binder to be carefully coated on one end of a copper mesh, and a small amount of Ti is dipped by a toothpick₃SiC₂Coating on one side with the adhesive;

(2) baking for 1-2 min by using a baking lamp to dry the sample, then washing the sample which is not firmly adhered by using absolute ethyl alcohol, and baking for 1-2 min by using the baking lamp again; (ii) a

(3) Putting the baked sample into a scanning electron microscope for observation, finding a proper sample observation area, recording the position of the sample, and taking an SEM picture;

(4) after taking out the sample, pouring 2mL of HF aqueous solution (with the concentration of 40%) into a 4mL plastic centrifuge tube, then putting the copper mesh adhered with the sample into a beaker for reaction, and recording the reaction time;

(5) in the reaction process, in order to avoid air pollution caused by volatilization of the HF aqueous solution, a cover of the plastic centrifuge tube is covered;

(6) after the reaction is finished, taking out the sample, cleaning the sample by using ultrapure water and absolute ethyl alcohol, placing the sample under a baking lamp for baking for 1-2 min to dry the sample, finding the position of the sample recorded in the scanning electron microscope again, and taking an SEM picture;

(7) and (5) repeating the steps (4) to (6) until the experiment is finished.

Example 5

Preparation of V₂The AlN in-situ scanning etching method comprises the following steps:

(1) under observation of an optical microscope, the polytetrafluoroethylene concentrated dispersion is used as a binder and is carefully coated on one end of a copper mesh, and a small amount of V is dipped by a toothpick₂AlN coated on the side with the binder;

(2) baking for 1-2 min by using a baking lamp to dry the sample, then washing the sample which is not firmly adhered by using absolute ethyl alcohol, and baking for 1-2 min by using the baking lamp again; (ii) a

(3) Putting the baked sample into a scanning electron microscope for observation, finding a proper sample observation area, recording the position of the sample, and taking an SEM picture;

(4) after taking out the sample, pouring 2mL of HF aqueous solution (with the concentration of 40%) into a 4mL plastic centrifuge tube, then putting the copper mesh adhered with the sample into a beaker for reaction, and recording the reaction time;

(5) in the reaction process, in order to avoid air pollution caused by volatilization of the HF aqueous solution, a cover of the plastic centrifuge tube is covered;

(6) after the reaction is finished, taking out the sample, cleaning the sample by using ultrapure water and absolute ethyl alcohol, placing the sample under a baking lamp for baking for 1-2 min to dry the sample, finding the position of the sample recorded in the scanning electron microscope again, and taking an SEM picture;

(7) and (5) repeating the steps (4) to (6) until the experiment is finished.