Two-phase shear nanoparticle dispersion method

Abstract

The present invention relates to the field of nanomaterial processing and dispersion, and discloses a two-phase shear nanoparticle dispersion method, which mainly comprises the following steps: uniformly mixing the nanomaterial to be dispersed, a liquid working fluid, and a dispersant; cooling the mixture loaded into a tubular mold, and liquefying a small amount of the working fluid in the contact area between the solid mixture and the outer surface of a friction disk to form an extremely thin liquid film, which will form an extremely high shear flow field and exert a strong deagglomeration effect on the nanoparticles contained in the liquid film.

Description

Technical Field

[0001] The invention relates to a method for dispersing nano materials, and belongs to the field of nano material processing and dispersion. Background Art

[0002] Nanomaterials such as carbon nanotubes offer excellent properties, but due to factors such as van der Waals forces and high aspect ratios, they are prone to entanglement and aggregation, hindering their full performance in subsequent applications. Therefore, nanomaterials often require thorough dispersion before application. Deagglomeration, a key component of nanomaterial dispersion, is the foundation and prerequisite for nanoparticle dispersion. Deagglomeration generally refers to the mechanical or physical breaking up of tightly aggregated nanoparticle clumps into smaller nanoparticle agglomerates or individual nanoparticles. Subsequent application of surfactants, coupling agents, and other agents maintains the nanoparticles in a homogeneous state within the system for a prolonged period. Current deagglomeration methods include ultrasonication, grinding, impact, and high-speed stirring. While various approaches based on these principles exist, they all share a common characteristic: centralized, overlapping processes. Specifically, each deagglomeration action, targeting a specific microscopic dispersed object, occurs with a certain probability, potentially impacting or not impacting the target. By cumulatively applying these deagglomerations at high frequencies, a high probability of deagglomeration is achieved, effectively achieving the desired deagglomeration effect. Taking high-speed stirring as an example, the blades are macroscopic in size, at least on the millimeter scale, while the objects being dispersed are carbon nanotubes, whose individual carbon nanotubes are at the nanometer scale. Obviously, each rotation of the blade cannot hit all the carbon nanotubes in the system. However, over time, the proportion of carbon nanotubes effectively hit by the blades will accumulate and increase, eventually achieving the desired proportion. It is noteworthy that the mechanical action randomly generates carbon nanotubes in the system, and a certain proportion of carbon nanotubes will remain undispersed during the dispersion process. Some carbon nanotubes will be repeatedly affected, resulting in a highly uneven application of the mechanical action. The resulting dispersed system contains carbon nanotubes of varying degrees of dispersion, resulting in poor dispersion quality. Furthermore, the continuous overlap of dispersion actions will lead to problems such as low energy utilization and low dispersion efficiency. Summary of the Invention

[0003] In view of the shortcomings of the prior art in the above background technology, the present invention provides a two-phase shear nanoparticle dispersion method, which completes the deagglomeration in one step without repeated mechanical action, thereby improving the dispersion quality and dispersion efficiency. To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0004] The two-phase shear nanoparticle dispersion method mainly includes the following steps:

[0005] 1. Evenly mix the nanomaterial to be dispersed, liquid working fluid and dispersant to obtain a mixture;

[0006] 2. Filling the mixture into a tubular mold;

[0007] 3. The mixture loaded into the tubular mold is cooled to T1. At T1, the working medium in the mixture is converted into a solid state and the temperature of the mixture in the tubular mold is maintained. At T1, the mixture as a whole does not have fluidity;

[0008] 4. Push part of the solid mixture in step 3 out of the tubular mold, and make the part extend 0.1-10mm beyond the end surface of the tubular mold;

[0009] 5. Place the end face of the solid mixture pushed out in step 4 in contact with the outer surface of the friction disk, with the axis of the tubular mold perpendicular to the plane of the friction disk, and the positions of the tubular mold and the friction disk relatively fixed;

[0010] 6. The friction disc rotates at a speed of 100-20,000 rpm, and the contact surface pressure between the solid mixture and the outer surface of the friction disc remains stable at 10-3500 Pa;

[0011] 7. The cold / hot gas blown out of the friction disc through the side blowpipe is used as a temperature compensation method to maintain the contact surface temperature between the solid mixture and the outer surface of the friction disc at T2;

[0012] 8. In the contact area between the solid mixture and the outer surface of the friction disk, a small amount of the working medium is liquefied to form an extremely thin liquid film. One side of the liquid film is the solid mixture, and the other side is the outer surface of the friction disk. Affected by the relative motion of the two, and because the axial thickness of the liquid film is extremely small, an extremely high shear flow field will be formed in the liquid film, which will form a strong deagglomeration effect on the nanoparticles contained in the liquid film. The dispersed nanoparticles are stabilized in the liquid phase system under the action of the dispersant in the liquid film and are thrown out under the action of centrifugal force. After continuous collection, a nano-dispersion liquid is obtained.

[0013] In step 1, the nanomaterial accounts for 0.1-30% of the mixture, and the dispersant accounts for 1-15% of the mixture. Other proportions are not required.

[0014] In step 1, the working fluid is the main substance required in the nanomaterial dispersion system, such as water, ethanol, and acetone;

[0015] In step 1, the mixture should be liquid or viscous liquid and should have high fluidity so as to fill the tubular mold;

[0016] In step 2, the diameter of the tubular mold should be uniform and the inner surface should be smooth to facilitate the ejection of the solid mixture;

[0017] In step 3, T1 is less than or equal to the freezing point temperature of the liquid working medium (K)*0.95;

[0018] In step 3, the mixture as a whole does not have fluidity at temperature T1, and the strength of the solid mixture should be such that it does not break, fall, or splash into fragments during the rotation of the friction disk;

[0019] In step 4, the solid mixture is pushed out of the tubular die at a speed that is uniform with the pressure on the outer surface of the friction disc, and the solid mixture is continuously replenished as it is consumed, forming a dynamic balance;

[0020] In step 5, the outer surface roughness of the friction disc is less than Ra0.012;

[0021] In step 7, T2 is greater than or equal to the freezing point temperature of the liquid working medium (K)*1.05 and less than or equal to the freezing point temperature of the liquid working medium (K)*1.25;

[0022] In step 8, the thickness of the liquid film is less than or equal to 0.02 mm.

[0023] The beneficial effect of the present invention is that it provides a two-phase shear nanoparticle dispersion method, which places the nanoparticles to be dispersed in the solid phase by freezing, and forms a liquid phase liquid film on the friction surface under high-speed friction of the friction disk. Because the liquid film thickness is extremely thin and the relative movement rate of the two sides of the liquid film is large, a strong shear flow field is formed in the liquid film, which has a strong dispersing effect on the nanoparticles therein and causes the nanoagglomerates to break up. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the operation of the two-phase shear nanoparticle dispersion method of the present invention.

[0025] In the figure: 1. Tubular mold, 2. Solid mixture, 3. Friction disk, 4. Friction disk shaft, 5. Side blowing pipe. DETAILED DESCRIPTION

[0026] The following further illustrates the specific implementation method of the present invention with reference to the accompanying drawings, using carbon nanotubes as the nanomaterial to be dispersed, deionized water as the working fluid, and SDBS as the dispersant:

[0027] 1. Evenly mix carbon nanotubes, deionized water, and SDBS in a mass ratio of 1:15:1 to obtain a mixture;

[0028] 2. Filling the mixed material into a tubular mold (1);

[0029] 3. Cooling the mixture loaded into the tubular mold (1) to T1. At T1, the working medium in the mixture changes to a solid state and maintains the temperature of the mixture in the tubular mold (1). At T1, the mixture as a whole does not have fluidity;

[0030] 4. Push part of the solid mixture (2) in step 3 out of the tubular mold (1), and make the part extend 1 mm beyond the end surface of the tubular mold (1);

[0031] 5. The end face of the solid mixture (2) pushed out in step 4 is brought into contact with the outer surface of the friction disk (3), the axis of the tubular mold (1) and the plane of the friction disk (3) are kept perpendicular, and the positions of the tubular mold (1) and the friction disk (3) are relatively fixed;

[0032] 6. The friction disc (3) rotates at a speed of 10,000 rpm, and the contact surface pressure between the solid mixture (2) and the outer surface of the friction disc (3) remains stable at 350 Pa;

[0033] 7. The cold / hot gas blown out of the friction disc (3) through the side blowing pipe (5) is used as a temperature compensation means to maintain the contact surface temperature between the solid mixture (2) and the outer surface of the friction disc (3) at T2;

[0034] 8. In the contact area between the solid mixture (2) and the outer surface of the friction disk (3), a small amount of the working medium is liquefied to form an extremely thin liquid film. One side of the liquid film is the solid mixture, and the other side is the outer surface of the friction disk (3). Affected by the relative motion of the two, and because the axial thickness of the liquid film is extremely small, an extremely high shear flow field will be formed in the liquid film, which will form a strong deagglomeration effect on the nanoparticles contained in the liquid film. The dispersed nanoparticles are stabilized in the liquid phase system under the action of the dispersant in the liquid film and are thrown out under the action of centrifugal force. After continuous collection, a carbon nanotube dispersion is obtained.

[0035] In step 2, the tubular mold (1) has a circular cross section, an inner diameter of 10 mm, and an inner wall roughness of Ra0.01;

[0036] In step 3, T1 = 260K;

[0037] In step 4, the solid mixture (2) is pushed out of the tubular mold at a speed of 2 mm / min, and the pushing method is an electric cylinder piston type;

[0038] In step 5, the outer surface roughness of the friction disc (3) is Ra0.011;

[0039] In step 7, T2 = 280K;

[0040] In step 8, the liquid film has a thickness of 0.01 mm.

Claims

1. The two-phase shear nanoparticle dispersion method mainly includes the following steps: (1) uniformly mixing the nanomaterial to be dispersed, the liquid working medium, and the dispersant to obtain a mixture; (2) filling the mixed material into a tubular mold; (3) Cooling the mixture loaded into the tubular mold to T1. At T1, the working medium in the mixture changes to a solid state and maintains the temperature of the mixture in the tubular mold. At T1, the mixture as a whole does not have fluidity; (4) pushing a portion of the solid mixture in step 3 out of the tubular mold, and allowing the portion to extend 0.1-10 mm beyond the end surface of the tubular mold; (5) The end face of the solid mixture pushed out in step 4 is brought into contact with the outer surface of the friction disk, the axis of the tubular mold is kept perpendicular to the plane of the friction disk, and the positions of the tubular mold and the friction disk are relatively fixed; (6) The friction disc rotates at a speed of 100-20,000 rpm, and the contact surface pressure between the solid mixture and the outer surface of the friction disc remains stable at 10-3500 Pa; (7) The cold / hot gas blown out of the friction disc through the side blowpipe is used as a temperature compensation method to maintain the contact surface temperature between the solid mixture and the outer surface of the friction disc at T2; (8) In the contact area between the solid mixture and the outer surface of the friction disk, a small amount of the working fluid is liquefied to form an extremely thin liquid film. One side of the liquid film is the solid mixture, and the other side is the outer surface of the friction disk. Under the relative motion of the two, and because the axial thickness of the liquid film is extremely small, an extremely high shear flow field will be formed in the liquid film, which will form a strong deagglomeration effect on the nanoparticles contained in the liquid film. The dispersed nanoparticles are stabilized in the liquid phase system under the action of the dispersant in the liquid film and are thrown out under the action of centrifugal force. After continuous collection, a nano-dispersion liquid is obtained; In step (1), the nanomaterial accounts for 0.1-30% of the mixture, the dispersant accounts for 1-15% of the mixture, and the working fluid is the main substance required in the nanomaterial dispersion system, such as water, ethanol, and acetone; the mixture should be a liquid or viscous liquid and should have high fluidity so as to fill the tubular mold; in step (2), the diameter of the tubular mold should be uniform and the inner surface should be smooth so as to facilitate the solid mixture to be pushed out of it; in step (3), T1 is less than or equal to the freezing point temperature of the liquid working fluid (K)*0.95; at the temperature T1, the mixture as a whole has no fluidity, and the solid mixture has The strength should be sufficient to prevent it from breaking, falling or splashing into fragments during the rotation of the friction disc; in step (4), the solid mixture is pushed out of the tubular mold at a speed and a uniform pressure on the outer surface of the friction disc, and the solid mixture is continuously replenished as it is consumed to form a dynamic balance; in step (5), the roughness of the outer surface of the friction disc is less than Ra0.012; in step (7), T2 is greater than or equal to the freezing point temperature of the liquid working medium (K)*1.05 and less than or equal to the freezing point temperature of the liquid working medium (K)*1.25; in step (8), the thickness of the liquid film is less than or equal to 0.02mm.

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