CN116026731B - A method to determine whether the dispersion of carbon nanotube slurry meets the standard by in-situ identification of particle size - Google Patents

Abstract

The invention provides a method for judging whether the dispersion of carbon nano tube slurry reaches the standard by in-situ identification of particle size. According to the technical scheme, the cause of a limit friction dispersion blind area is firstly explored, and then the relation between the granularity D90 of the carbon nanotube slurry and the diameter of the spherical beads is obtained, so that the nanotube slurry is subjected to suction filtration by adopting a specific pore-size filter material, and whether the dispersion of the carbon nanotube slurry reaches the standard can be judged according to the residual condition of the slurry on the surface of the filter material after the suction filtration. Specifically, if the surface of the filter material has no residue, the dispersion is up to the standard, and if the slurry is remained on the filter material to block the net, the dispersion granularity is larger and the dispersion is not up to the standard; wherein, the following relation is satisfied between the filter pore diameter R and the ball diameter D of the slurry: r=0.07 d·a, where a=15/14. The invention samples without any pretreatment, thus maintaining the authenticity of the structure of the slurry; the accuracy of the test result is ensured through the filtering and screening of the slurry particles D90; meanwhile, the testing method is rapid and convenient, and the timeliness of testing and judging is guaranteed.

Description

A method to determine whether the dispersion of carbon nanotube slurry meets the standard by in-situ identification of particle size

Technical field

The invention relates to the technical field of nanomaterials, and specifically relates to a method for in-situ identification of particle size to determine whether the dispersion of carbon nanotube slurry reaches the standard.

Background technique

At present, in the process of industrial production of carbon nanotube slurry, quality and technical personnel are often required to judge whether the carbon nanotube slurry is dispersion qualified. Commonly used methods are: 1) Scraper fineness method, scrape the slurry on a fineness plate, and observe with the naked eye whether there are large particles. This method has great human subjective factors and huge errors; 2) Viscometer test Method, take the slurry dispersed at different times to test its viscosity and observe whether the viscosity value is consistent. The viscosity of the slurry itself has certain fluctuations, and it is also true that the dispersion of the slurry has a dynamic balance for a period of time. Therefore, there is an error in the judgment of viscosity, such as grinding and dispersing too early or too late. 3) Laser particle size testing method, dilute part of the slurry to a certain concentration, ultrasonically disperse it into a specific solvent, and pass the particle size analyzer test; this method cannot be implemented at the sampling site, and the steps such as dilution and ultrasonic dispersion in this method are harmful to the particle size test method. The slurry itself has a destructive effect, causing distortion of test results.

Contents of the invention

The present invention aims to address the technical shortcomings of the existing technology and provide a method for in-situ identification of particle size to determine whether the dispersion of carbon nanotube slurry reaches the standard, so as to solve the technical problems of conventional methods such as large errors, easy damage to the slurry, and inability to be implemented on site. .

In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

The method of in-situ particle size identification to determine whether the carbon nanotube slurry is dispersed up to standard includes the following steps: Use a negative pressure filtration device to suction filter the carbon nanotube slurry. After the suction filtration, if there is no residue on the surface of the filter material, it indicates dispersion. If the slurry remains blocked on the filter material, it indicates that the dispersed particle size is too large and does not meet the standard; among them, the pore size R of the filter material and the ball diameter D of the slurry satisfy the following relationship: R=0.07D·a, where a=15/14.

Preferably, the amount of carbon nanotube slurry is 20 mL.

Preferably, the duration of the suction filtration is 3 to 5 minutes.

Preferably, the negative pressure filter device includes a filter bottle, a negative pressure filter port, a filter bucket, and a filter material, wherein the negative pressure filter port is located at the side end of the filter bottle, and there is a filter bucket at the top of the filter bottle, and the filter material is fixed on In the filter bucket and intercepting at least one cross section of the filter bucket, a vacuum pump is connected to the negative pressure filter port.

Preferably, the filter material is a stainless steel filter.

As a preferred option, the stainless steel filter mesh is tightly adhered to the surface of the filter bucket.

The invention provides a method for in-situ particle size identification to determine whether the dispersion of carbon nanotube slurry reaches the standard. This method does not require any pre-processing for sampling, thus maintaining the authenticity of the structure of the slurry itself; filtering and screening the slurry particles D90 to ensure the accuracy of the test results; at the same time, the test method is fast and convenient, ensuring the timeliness of the test judgment. .

Description of the drawings

Figure 1 is a schematic structural diagram of the negative pressure filtration device in the present invention;

Figure 2 is a schematic diagram of the microscopic state when different numbers of balls rub against each other;

In the picture:

1. Filter bottle 2. Negative pressure suction filter port 3. Filter bucket 4. Filter material.

Detailed ways

Specific embodiments of the present invention will be described in detail below. In order to avoid too many unnecessary details, well-known structures or functions will not be described in detail in the following embodiments. The approximate language used in the following examples can be used for quantitative expressions, indicating that certain changes in quantities are allowed without changing the basic function. Unless otherwise defined, technical and scientific terms used in the following examples have the same meanings as commonly understood by those skilled in the art to which this invention belongs.

Example 1

A method to identify the particle size in situ to determine whether the dispersion of carbon nanotube slurry meets the standard (i.e. test the filtration passability of particle size D90):

1) Construct a simple negative pressure filtration device. The core of the device is the determination of the mesh number of the filter screen in the middle of the filter bucket and the dense combination of the filter screen and the filter bucket.

2) Determination of carbon nanotube slurry particle size D90. The dispersion of carbon nanotube slurry is based on the friction of continuous motion of the beads. Double-ball friction can achieve seamless friction and achieve nano-dispersion; however, when three-ball friction occurs, it is easy to have a blind zone of extreme friction and dispersion, forming the agglomeration range of dispersed particles, which is the D90 particle size. D90 is equal to 0.07 times the diameter of the ball.

3) Use 20ml of carbon tube slurry dispersed with 1.0mm beads, filter the slurry on a negative pressure filtration device through vacuum filtration (select the filter screen to be 200 mesh, pore size 75um), filter for 3-5 minutes, and filter the slurry. If there is no residue on the surface, it means the dispersion is qualified. If there is residue blocking the network, it means the dispersion particle size is too large and it is unqualified.

Core technical links:

1. Construct a simple negative pressure filtration device

As shown in Figure 1, the device consists of a filter bucket, a stainless steel filter screen, a filter bottle and a negative pressure suction filter port. One of the cores of the device: the dense combination of the stainless steel filter screen and the filter bucket plane; the mesh number of the stainless steel filter screen is 100-500 mesh.

During suction filtration, connect the negative pressure suction filter port through a vacuum pump to conduct a suction filtration experiment.

2. Determination of carbon nanotube slurry particle size D90

The dispersion of carbon nanotube slurry is achieved based on the continuous motion friction of the beads. As shown in Figure 2, the beads continuously move and rub. When the two balls rub, seamless friction can be achieved, that is, nano-dispersion is achieved. When the three balls rub, the dispersion limit blind zone is prone to appear, forming agglomeration range of the slurry particles. Therefore, during the process of grinding the slurry, the size of the overall particle D90 of the slurry (the hole size through which 90% of the particles can pass) is directly consistent with the size of the dispersion limit blind zone.

According to the above mathematical models of ball motion friction, there are four types: 1) single ball rolling, 2) double ball friction and peeling, 3) three ball friction and 4) four ball friction. Four-ball friction has a loose structure and unstable contact interface; three-ball friction can form a fixed structure with a high probability of moving together, resulting in a limit gap of friction contact, that is, a dispersion limit blind zone. According to calculations, the limit spacing of dispersion blind zones is 0.07D, which is 0.07 times the diameter of the ball.

In actual operation, you can refer to the following Table 1 to select the corresponding filter material:

Table 1 Bead diameter, dispersion limit area D90 and screen mesh list

Ball diameter (mm) Limit area-D90 (μm) Screen (mesh) 1.4 98 140--106 1.2 84 160--96 1.0 70 200--75 0.8 56 250--58 0.6 42 325--45 0.4 28 400--38 0.3 twenty one 500--25 0.2 14 800--18

3. Filter large particle test

1) Use 20ml of carbon tube slurry dispersed with 1.0mm beads, filter the slurry on a negative pressure filtration device through vacuum filtration (select the filter screen to be 200 mesh, pore size 75um), and filter for 3-5 minutes. Observe with the naked eye through the filter whether there are large particles or residues. If there is no residue on the surface of the filter, it means the dispersion is qualified. If there is residue blocking the screen, it means the dispersion particle size is too large and it is unqualified.

Table 2 Experimental list of 200 mesh screen filtering 1.0mm bead grinding and dispersing carbon nanotube slurry

Grinding and dispersing sample/hour/100kg screen residue Eligibility 1 Residues, large particles no 2 Residue no 2.5 No residue yes 3 There are residues and particles no

2) Use 20ml of carbon tube slurry dispersed with 0.6mm beads, filter the slurry on a negative pressure filtration device through vacuum filtration (select the filter screen to be 325 mesh, pore size 45um), and filter for 3-5 minutes. Observe with the naked eye through the filter whether there are large particles or residues. If there is no residue on the surface of the filter, it means the dispersion is qualified. If there is residue blocking the screen, it means the dispersion particle size is too large and it is unqualified.

Table 3 Experimental list of 325 mesh screen filtering 0.6mm bead grinding and dispersing carbon nanotube slurry

Grinding and dispersing sample/hour/100kg screen residue Eligibility 1 Residues, large particles no 2 none yes 2.5 Residue no

Example 2

The method of in-situ particle size identification to determine whether the carbon nanotube slurry is dispersed up to standard includes the following steps: Use a negative pressure filtration device to suction filter the carbon nanotube slurry. After the suction filtration, if there is no residue on the surface of the filter material, it indicates dispersion. If the slurry remains blocked on the filter material, it indicates that the dispersed particle size is too large and does not meet the standard; among them, the pore size R of the filter material and the ball diameter D of the slurry satisfy the following relationship: R=0.07D·a, where a=15/14.

Preferably, the amount of carbon nanotube slurry is 20 mL.

Preferably, the duration of the suction filtration is 3 to 5 minutes.

Preferably, the negative pressure filtration device includes a filter bottle 1, a negative pressure filter port 2, a filter bucket 3, and a filter material 4. The negative pressure filter port 2 is located at the side end of the filter bottle 1, and there is a filter at the top of the filter bottle 1. Filter bucket 3, the filter material 4 is fixed in the filter bucket 3 and intercepts at least one cross section of the filter bucket 3, and a vacuum pump is connected to the negative pressure filter port 2.

Preferably, the filter material 4 is a stainless steel filter screen.

Preferably, the surface of the stainless steel filter screen and the filter bucket 3 are tightly adhered.

The embodiments of the present invention have been described in detail above, but the described contents are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the application scope of the present invention shall be included in the protection scope of the present invention.

Claims (6)

1. The method for judging whether the dispersion of the carbon nano tube slurry meets the standard by in-situ identification of the particle size is characterized by comprising the following steps: carrying out suction filtration on the carbon nano tube slurry by using a negative pressure filter device, if the surface of the filter material has no residue after the suction filtration is finished, indicating that the dispersion reaches the standard, and if the slurry has a blocking net remained on the filter material, indicating that the dispersion granularity is larger and does not reach the standard; wherein, the following relation is satisfied between the filter pore diameter R and the ball diameter D of the slurry: r=0.07 d·a, where a=15/14.

2. The method for determining whether the dispersion of the carbon nanotube slurry meets the standard by in-situ identification of particle size according to claim 1, wherein the amount of the carbon nanotube slurry is 20mL.

3. The method for determining whether the dispersion of the carbon nanotube slurry meets the standard by in-situ identification of particle size according to claim 1, wherein the duration of suction filtration is 3-5 min.

4. The method for in-situ identification of particle size to determine whether dispersion of carbon nanotube slurry meets standards according to claim 1, wherein the negative pressure filtering device comprises a filter flask (1), a negative pressure suction filter port (2), a filter funnel (3) and a filter medium (4), wherein the negative pressure suction filter port (2) is positioned at the side end of the filter flask (1), the filter funnel (3) is arranged at the top end of the filter flask (1), the filter medium (4) is fixed in the filter funnel (3) and intercepts at least one cross section of the filter funnel (3), and a vacuum pump is connected to the negative pressure suction filter port (2).

5. The method for determining whether the dispersion of the carbon nanotube slurry meets the standard according to the in-situ identification particle size of claim 4, wherein the filter material (4) is a stainless steel filter screen.

6. The method for judging whether the dispersion of the carbon nano tube slurry meets the standard or not according to the in-situ identification particle size of claim 5, wherein the stainless steel filter screen is tightly attached to the surface of the filter bucket (3).