A method for rapidly preparing high-concentration MXene slurry

Abstract

The present invention discloses a method for rapidly preparing a high-concentration MXene slurry, and the method comprises the following steps: First, mix hydrochloric acid and nitric acid to obtain a capturer; Second, mix the capturer with a Ti3C2T x MXene dispersion liquid to obtain an MXene dispersion liquid; Third, pass the MXene dispersion liquid through a vacuum filtration device to form a filter cake on a filter membrane, and wash the filter cake by adding deionized water to obtain a hydrogel-like MXene filter cake; Fourth, peel the MXene filter cake from the surface of the filter membrane, transfer it to a beaker, and perform homogenization treatment at room temperature by a high-speed homogenizer to obtain an MXene slurry. By introducing hydrochloric acid and nitric acid as capturers, the present invention greatly improves the filtration speed of the MXene dispersion liquid and can be converted into a high-concentration MXene slurry within 10 minutes. The solid content of the slurry is 12-15 wt%, the viscoelasticity is good, and the residual acid content is <0.001 M / L.

Description

Technical Field

[0001] The invention belongs to the technical field of microelectronic device materials and relates to a method for preparing a MXene slurry. Background Art

[0002] As a new type of two-dimensional material, MXene has become an ideal choice for functional ink formulations due to its unique chemical, electrical, optical and mechanical properties. Through screen printing technology, MXene ink can be used to prepare high-performance microelectronic devices on a large scale on various substrates. Screen printing requires MXene inks with a higher solid content (10-15wt%). However, the MXene dispersion prepared by chemical etching has a low concentration, with a solid content of about 1wt%. In order to obtain MXene inks with a high solid content, people usually use long-term high-speed centrifugation to concentrate the MXene dispersion. In previous studies, the applicant obtained a semi-solid MXene with a solid content of 19.4wt% by combining high-speed centrifugation (10,000 rpm, 1 hour) with long-term heating evaporation (50°C, 6-8 hours). The semi-solid MXene has good dispersibility in water and can be processed into MXene slurries of different concentrations according to actual needs (ACS Materials Letters, 2020, 2(12): 1598-1605.). However, this method requires a high-speed centrifuge to centrifuge the MXene dispersion for a long time, and the single processing volume is only 100 to 200 mL. The equipment cost is high and the efficiency is low. The centrifuged product needs to be further processed by heating and evaporation for a long time, which makes the MXene ink have the risk of oxidation and deterioration. The whole process takes more than ten hours, which limits the preparation efficiency of high-concentration MXene ink. In addition, some researchers have freeze-dried the MXene dispersion for a long time and then rehydrated it to convert it into a semi-solid MXene with a high solid content of 60wt%, but the whole process takes 2 to 3 days (Advanced Science, 2023, 10 (19): 2300660.). At present, the existing methods for preparing high-concentration MXene slurry are complicated and inefficient, requiring several or even dozens of hours of processing. For practical applications, it is necessary to develop a method suitable for industrial production that can quickly convert low-concentration MXene dispersion into MXene slurry with high solid content. High-concentration MXene slurry is the core raw material for screen-printed MXene devices. The facile and rapid preparation of high-concentration MXene slurry is an important prerequisite for the realization of large-scale screen-printed MXene devices. Summary of the invention

[0003] In order to solve the problem of low efficiency in preparing high-concentration MXene slurry, the present invention provides a method for quickly preparing high-concentration MXene slurry. The method converts MXene nanosheets into microgels by preparing a mixed solution of hydrochloric acid and nitric acid as a capture agent, and obtains a high-concentration MXene slurry by vacuum-assisted filtration, thereby solving the problem of low efficiency in preparing high-concentration MXene slurry.

[0004] The objective of the present invention is achieved through the following technical solutions:

[0005] A method for rapidly preparing a high-concentration MXene slurry comprises the following steps:

[0006] Step 1, capture agent preparation: 5M / L hydrochloric acid and 2M / L nitric acid are mixed in a volume ratio of 2:1 to 5:1, and mixed evenly by magnetic stirring. The magnetic stirring time is controlled to be 1 to 5 minutes and the rotation speed is 200 to 800 rpm to obtain a capture agent;

[0007] Step 2: MXene dispersion treatment: The capture agent obtained in step 1 was mixed with Ti3C2T x The MXene dispersion is mixed at a volume ratio of 0.5 to 2:10, and mixed evenly by magnetic stirring, and the magnetic stirring time is controlled to be 1 to 5 minutes and the rotation speed is 200 to 800 rpm to obtain a MXene dispersion;

[0008] Step 3, preparation of MXene filter cake: the MXene dispersion obtained in step 2 is passed through a vacuum filtration device, the solvent is separated on a mixed cellulose ester microporous filter membrane with a pore size of 0.45 μm to form a filter cake, and the filter cake is washed by adding deionized water and filtering again to obtain a hydrogel-like MXene filter cake;

[0009] Step 4. Preparation of high-concentration MXene slurry: The MXene filter cake obtained in step 3 is peeled off from the surface of the filter membrane, transferred to a beaker, and homogenized by a high-speed homogenizer at room temperature. The homogenization time is controlled to be 2 to 5 minutes, and the rotation speed is 10,000 rpm to obtain a MXene slurry with a concentration of 12 to 15 wt%. The slurry can be used for screen printing to obtain a MXene device pattern with a clear pattern and uniform thickness.

[0010] Compared with the prior art, the present invention has the following advantages:

[0011] 1. The present invention greatly improves the filtration speed of MXene dispersion by introducing hydrochloric acid and nitric acid as capture agents, and can convert MXene dispersion into high-concentration MXene slurry within 10 minutes. The solid content of the slurry is 12-15wt%, the viscoelasticity is good, and the residual acid content is less than 0.001M / L, which does not affect its subsequent processing as the initial raw material.

[0012] 2. The high-concentration MXene slurry of the present invention has a high storage modulus and loss modulus, and can be directly used in a screen printing device without additional disorder treatment. In addition, the MXene device obtained by screen printing has excellent conductivity (8000S / cm) and electrothermal properties, and has excellent low-pressure rapid heating performance (5V, 90°C) after testing.

[0013] 3. The operation of preparing MXene slurry according to the present invention is simple, the equipment requirements are low, the MXene slurry output is high, the oxidation is slow, and the MXene slurry can be stored for 180 days.

[0014] 4. The present invention solves the problem of producing high-concentration MXene slurry required for application scenarios such as MXene film coating, MXene material 3D printing, and MXene transfer printing. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the MXene filter cake with excess hydrochloric acid residue in Example 1.

[0016] Figure 2 This is the MXene filter cake after washing in Example 1.

[0017] Figure 3 This is the high concentration MXene slurry prepared in Example 1.

[0018] Figure 4 The viscosity and shear rate diagram of the high-concentration MXene slurry prepared in Example 1 and the MXene device obtained by screen printing.

[0019] Figure 5 This is the low-pressure rapid heating performance of the MXene device prepared in Example 1.

[0020] Figure 6 This is the pattern of the MXene device that undergoes blurring in Example 5.

[0021] Figure 7 The low-pressure rapid thermal performance and electrical conductivity of the MXene device prepared in Example 6. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is further described below in conjunction with the accompanying drawings, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be included in the protection scope of the present invention.

[0023] The present invention provides a method for quickly preparing a high-concentration MXene slurry. First, by configuring a mixed solution of nitric acid and hydrochloric acid as a capture agent, the MXene nanosheets in the dispersion are converted into MXene microgels. Next, most of the solvent in the MXene aggregates can be quickly removed by vacuum-assisted filtration to form a MXene filter cake with a high solid content. Since MXene is a hydrophilic material, the filtered MXene filter cake still has a certain amount of residual moisture and capture agent. Afterwards, in order to further remove the residual capture agent, deionized water is added for washing. After the surface moisture is filtered off, the remaining product is transferred to a beaker. Finally, the MXene slurry is homogenized by a high-speed homogenizer, and the product is a high-concentration MXene slurry. Specifically comprising the following steps:

[0024] Step 1: Preparation of the capture agent: Mix 5M / L hydrochloric acid and 2M / L nitric acid in a volume ratio of 2:1 to 5:1, and mix them evenly by magnetic stirring for 1 to 5 minutes (200 to 800 rpm) to obtain a capture agent.

[0025] In this step, if the concentration of nitric acid is too high, the product cannot be processed into a high-concentration slurry in step four. If the concentration of hydrochloric acid is too high, the product will be filtered too fast in step three, and the concentration of the MXene slurry processed in step four exceeds 40wt%, which is not suitable for screen printing devices. On the contrary, if the concentrations of nitric acid and hydrochloric acid are too low, the filtering speed of step three will be slowed down, and it will take 1 hour to complete step two, which greatly prolongs the total preparation time. The present invention finds that only when the concentration of 5M / L hydrochloric acid and 2M / L nitric acid are mixed in a volume ratio of 2:1 to 5:1, a suitable capture agent can be obtained, and the rapid filtration of MXene nanosheets and subsequent high-concentration slurry can be achieved simultaneously. The remaining ratios will lead to insufficient cross-linking of the MXene dispersion, which will lead to a low filtration rate, requiring several hours to filter, or the MXene cross-linking degree is too large, resulting in the filter cake after filtration. Even after multiple washings, there is still serious cross-linking between the internal MXenes, and it cannot be restored to a slurry state.

[0026] Although rapid filtration of MXene can be achieved by adding potassium hydroxide, the filtered product cannot be slurried. The introduction of metal ions can also trigger the gelation of MXene dispersions, but the metal ions will react too strongly with MXene, resulting in subsequent inability to slurry. The present invention adjusts the ratio of hydrochloric acid and nitric acid to achieve a moderate degree of gelation of the MXene dispersion, thereby avoiding the problem of inability to slurry caused by excessive cross-linking of MXene. By optimizing the capture agent ratio, rapid filtration of the MXene dispersion and subsequent high-concentration slurrying are achieved at the same time.

[0027] Step 2: MXene dispersion treatment: The capture agent obtained in step 1 was mixed with Ti3C2T x The MXene dispersions were mixed in a volume ratio of 0.5 to 2:10 and uniformly mixed by magnetic stirring for 1 to 5 minutes (200 to 800 rpm).

[0028] In this step, the MXene dispersion is a colloidal dispersion, and the electrostatic repulsion between the MXene nanosheets is the main force driving the stability of the colloidal system. The hydroxyl groups on the MXene surface will be protonated, and the hydroxyl groups will release H + Enter the solvent environment. The protonation of hydroxyl groups causes the MXene surface to be electronegative, and at the same time generates a sufficiently strong electrostatic repulsion to stabilize the MXene colloidal dispersion. When the capture agent is introduced into the MXene dispersion, the protonation process of hydroxyl groups on the MXene surface is inhibited, destroying the electrostatic balance between MXene nanosheets. In particular, H + and NO 3- MXene can be effectively and quickly formed into microgels. Water molecules can quickly pass through the gaps in the microgels. In addition, a small amount of lithium fluoride will remain in the dispersion during the preparation of MXene. When hydrochloric acid is added to the MXene dispersion, the hydrochloric acid will react with the residual lithium fluoride on the surface of the MXene, causing it to be redispersed in the solvent and removed in subsequent filtration.

[0029] Step 3, MXene filter cake preparation: The mixed solution obtained in step 2 is passed through a vacuum filtration device, and the solvent is completely separated within 30 to 60 seconds using a mixed cellulose ester microporous filter membrane (pore size 0.45 μm). Most of the solvent is filtered, and a small amount of solvent and MXene nanosheets remain on the filter membrane to form a filter cake. Add deionized water, and after the water is filtered out, add deionized water again to wash again. After the water is filtered out, a hydrogel-like MXene filter cake is obtained.

[0030] In this step, the mixed solution of step 2 is filtered, and most of the solvent and capture agent are removed. However, some capture agents remain in the remaining filter cake, which affects the rheological properties of the MXene slurry, and the MXene slurry needs to be further cleaned. In this step, the MXene slurry is cleaned by adding deionized water and filtering again, adding 150 mL each time, and repeating twice.

[0031] Step 4: Preparation of high-concentration MXene slurry: The MXene filter cake obtained in step 3 is peeled off from the surface of the filter membrane, transferred to a beaker, and processed by a high-speed homogenizer at room temperature for 2 to 5 minutes (10,000 rpm) to obtain a uniform, viscous MXene slurry (12 to 15 wt%). The slurry can be used for 200-mesh screen printing to obtain a MXene device pattern with a clear pattern and uniform thickness.

[0032] In this step, the concentration of the MXene slurry after cleaning in step three is uneven, and further mixing treatment is required to obtain a high-concentration MXene slurry with uniform concentration.

[0033] Example:

[0034] Example 1

[0035] Step 1: Mix 5M / L hydrochloric acid and 2M / L nitric acid in a volume ratio of 3:1, and mix them evenly by magnetic stirring for 1 minute (500 rpm) to obtain a capture agent.

[0036] Step 2: Mix the capture agent prepared in step 1 and Ti3C2T3 with a concentration of 5 mg / mL. x The MXene dispersion was mixed in a beaker at a volume ratio of 1:10, and the total volume of the mixed solution was 2 L. The mixture was stirred for 1 minute (500 rpm) by a magnetic stirring device to mix evenly. The MXene dispersion flocculated, and the solution state was a solution containing precipitation. After the MXene dispersion in this state was stored for 10 days, severe oxidation occurred.

[0037] Step 3: The mixed solution obtained in step 2 was passed through a 3L vacuum filtration device, and the solvent was completely separated within 1 minute using a mixed cellulose ester microporous filter membrane (pore size 0.45μm). Most of the solvent was filtered, and a small amount of solvent and MXene nanosheets remained on the filter membrane to form a filter cake about 2cm thick. Excess hydrochloric acid and nitric acid (0.5M / L) remained in the filter cake, which was loose as a whole and not in a slurry state, such as Figure 1 As shown. Add 150mL of deionized water, and after the water is filtered out, add 150mL of deionized water again for washing. After the water is filtered out, a hydrogel-like MXene filter cake is obtained, as shown Figure 2 shown.

[0038] Step 4: Peel off the MXene filter cake from the filter membrane surface, transfer it to a 500 mL beaker, and process it in a high-speed homogenizer at room temperature for 3 minutes (10,000 rpm) to obtain a uniform, viscous MXene slurry ( Figure 3 ), solid content 12-15wt%. The slurry has good viscoelasticity and can be used for 200 mesh screen printing to obtain clear patterns ( Figure 4 ), MXene device pattern with uniform thickness. After testing, the device has an electrical conductivity of 8000S / cm, which has excellent electrical conductivity. The device also has excellent low-pressure rapid heating performance, which can quickly rise to a constant temperature within 10 seconds, and has a heating effect of 95°C under a load voltage of 5V ( Figure 5 ).

[0039] Example 2

[0040] The difference between this embodiment and embodiment 1 is that the volume ratio of hydrochloric acid to nitric acid is 1: 10. After adding the capture agent, the MXene dispersion liquid does not flocculate, and the solution state is a uniform colloidal dispersion liquid.

[0041] Example 3

[0042] The difference between this embodiment and embodiment 1 is that the concentration of nitric acid is 10M / L. After adding the capture agent, the MXene dispersion flocculates, and the solution state is a solution containing precipitation. After step three and step four, the product is still granular and cannot be converted into a high-concentration MXene slurry.

[0043] Example 4

[0044] The difference between this embodiment and embodiment 1 is that the total volume of the mixed solution is 20 L. After adding the capture agent, the MXene dispersion flocculates, and the solution state is a solution containing precipitation. After step three and step four, the product is still granular and cannot be converted into a high-concentration MXene slurry. After the reaction system is scaled up, the local concentration is too high when the capture agent is added, resulting in abnormal experimental results.

[0045] Example 5

[0046] The difference between this embodiment and embodiment 1 is that the slurry is not processed by a high-speed homogenizer, but only processed by a magnetic stirring device (500 rpm, 3 minutes). The slurry concentration is uneven and has obvious granularity. The slurry is used for 200 mesh screen printing, and the pattern is blurred ( Figure 6 ), MXene device pattern with uneven thickness. Due to its irregular shape, the device does not form a conductive path and cannot load voltage for low-voltage rapid heating applications.

[0047] Example 6

[0048] The difference between this embodiment and embodiment 1 is that the high-speed homogenizer treatment time is 30 minutes. The long-term treatment increases the slurry temperature from room temperature to 80°C. The long-term high-temperature treatment causes the MXene slurry to oxidize. The slurry is used for 200-mesh screen printing to obtain a MXene device pattern with a clear pattern and uniform thickness. However, the conductivity of the device is reduced from 8000S / cm to 3000S / cm, and its low-pressure rapid heating performance is reduced. Under a load voltage of 5V, the heating temperature drops from 95°C to 73°C ( Figure 7 ).

[0049] It can be concluded from the above examples that the method provided by the present invention can be used to quickly convert a low-concentration MXene dispersion into a high-concentration MXene slurry. The slurry has a high concentration (12-15wt%) and is suitable for screen printing. The prepared MXene device has excellent conductivity and low-pressure rapid heating effect.

Claims

1. A method for rapidly preparing a high-concentration MXene slurry, characterized in that The method comprises the following steps: Step 1: preparing the capture agent: mixing 5 M / L hydrochloric acid and 2 M / L nitric acid in a volume ratio of 2:1 to 5:1, and mixing them evenly by magnetic stirring. The magnetic stirring time is controlled to be 1 to 5 minutes and the rotation speed is 200 to 800 rpm to obtain the capture agent. Step 2: MXene dispersion treatment: The capture agent obtained in step 1 was mixed with Ti3C2T x The MXene dispersion is mixed at a volume ratio of 0.5 to 2:10, and mixed evenly by magnetic stirring. The magnetic stirring time is controlled to be 1 to 5 minutes, and the rotation speed is 200 to 800 rpm to obtain a MXene dispersion. Step 3, preparation of MXene filter cake: the MXene dispersion obtained in step 2 is passed through a vacuum filtration device, the solvent is separated on a mixed cellulose ester microporous filter membrane with a pore size of 0.45 μm to form a filter cake, and the filter cake is washed by adding deionized water and filtering again to obtain a hydrogel-like MXene filter cake; Step 4. Preparation of high-concentration MXene slurry: The MXene filter cake obtained in step 3 is peeled off from the surface of the filter membrane, transferred to a beaker, and homogenized by a high-speed homogenizer at room temperature. The homogenization time is controlled to be 2 to 5 minutes, and the rotation speed is 10,000 rpm to obtain a MXene slurry with a concentration of 12 to 15 wt%.

2. The method for rapidly preparing a high-concentration MXene slurry according to claim 1, characterized in that In the step 3, the solvent separation time is 30 to 60 seconds.

3. The method for rapidly preparing a high-concentration MXene slurry according to claim 1, characterized in that In step 3, the MXene slurry is washed twice, and 150 mL is added each time.

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