Aramid carbon nano dispersion and preparation method thereof

Abstract

The invention discloses an aramid carbon nano dispersion and a preparation method thereof, aiming to solve the problem that the graphene material cannot be evenly dispersed when the existing graphene and carbon nanotubes are composited, resulting in defects in mechanical properties and thermal conductivity of the composite material prepared thereby. The interaction between graphene and carbon nanotubes is improved by introducing aramid nanofibers, so that the composite material prepared thereby has both excellent mechanical properties and high thermal conductivity.

Description

Technical Field

[0001] The invention discloses an aramid carbon nano dispersion and a preparation method thereof, and specifically relates to an aramid modified carbon nano material dispersion and a preparation method thereof, and belongs to the field of new nano materials. Background Art

[0002] In the thermal management technology of electronic components, carbon materials are often used as high thermal conductivity materials due to their advantages such as light weight, corrosion resistance, good mechanical properties, excellent thermal conductivity, and small thermal expansion coefficient, such as graphene oxide (GO) and carbon nanotube (CNT). Among them, graphene oxide (GO) is a precursor material for the synthesis of graphene. It has a large number of hydrophilic groups (-COOH, -OH, etc.) on its surface, which enables it to exist stably in most solvents without agglomeration. However, compared with graphene, the introduction of oxygen-containing groups has destroyed its structural integrity to a certain extent, and these doping points have also become the locations where phonons and electrons scatter, thereby greatly reducing its electrical and thermal conductivity, and limiting the effective performance of thermoelectric performance. Carbon nanotubes (CNTs) can be seen as graphene or graphene sheets curled up, with both ends covered by hemispherical large fullerene molecules. Depending on the number of graphene layers that make up the CNT curls, they can be divided into multi-walled carbon nanotubes, double-walled carbon nanotubes and single-walled carbon nanotubes. The main thermal conductivity of carbon nanotubes (CNTs) is lattice vibration phonon conduction, which has extremely high thermal conductivity. The thermal conductivity of single-walled carbon nanotubes can reach 3900 W / (m. K), and the thermal conductivity of multi-walled carbon nanotubes is 3500 W / (m. K).

[0003] In the prior art, a pure carbon composite film can be obtained by compounding a graphene film with a carbon nanotube, wherein the carbon nanotube will make up for the grain boundary defects of the graphene, giving full play to the advantages of both, thereby improving the mechanical properties and thermal conductivity of the film. For example, in the invention patent with the publication number CN103725263A, graphene and carbon nanotubes are mixed evenly by stirring and ultrasonic dispersion, and then the graphene and carbon nanotubes are fully reacted under hydrothermal or solvothermal conditions. After the reaction is completed and the solvent is removed, a graphene-carbon nanotube composite material with an entangled network structure can be obtained. The method is simple to operate, low in cost, and has great commercial application value.

[0004] However, the comprehensive performance of the GO / CNT composite film after adding CNTs in the prior art has not reached the ideal value, and the mechanical and heat resistance properties cannot be taken into account at the same time. The addition of CNTs does not significantly improve the vertical plane thermal conductivity of graphene. This is because the dispersibility of CNTs in the graphene matrix is ​​poor, and the connection ability between CNTs and graphene sheets is still weak. For graphene materials, their two-dimensional structure and huge specific surface area make them difficult to disperse and easy to agglomerate, and this agglomeration is irreversible, which will greatly affect the thermal conductivity of graphene dispersion; for carbon nanotubes, due to their own structure with a high aspect ratio and large surface area, there is a large van der Waals attraction between the tubes, making them almost insoluble, and they are entangled with each other, cross-linked, and strongly agglomerated and entangled. Therefore, in order to effectively improve the comprehensive performance of carbon nanotube and graphene composite materials, it is necessary to improve the dispersion performance of graphene materials in composite materials. Summary of the invention

[0005] The purpose of the present invention is to provide an aramid carbon nano dispersion and a preparation method thereof, aiming to solve the problem that the graphene material cannot be evenly dispersed when the existing graphene and carbon nanotubes are composited, resulting in the defects of the composite material prepared therefrom in terms of mechanical properties and thermal conductivity. The interaction between graphene and carbon nanotubes is improved by introducing aramid nanofibers, so that the composite material prepared therefrom has both excellent mechanical properties and high thermal conductivity.

[0006] The present invention is achieved through the following technical solution: A method for preparing aramid carbon nano dispersion, comprising the following steps:

[0007] (1) Aramid fiber and KOH are mixed with dimethyl sulfoxide in a mass ratio of 1:1 to 1:2, and stirred to form an ANF / DMSO solution. Water is then added to the ANF / DMSO solution in a volume ratio of water to the ANF / DMSO solution of 1:1 to 4:1, and stirred to obtain an ANF / DMSO / H2O solution. The aramid nanofiber dispersion is then obtained after suction filtration, water washing, and homogenization.

[0008] (2) Mix and disperse 0.005-0.05 parts of carbon nanotube powder, 0.005-0.1 parts of dispersant, 0.005-0.1 parts of stabilizer and 1 part of water by weight to obtain a carbon nanotube dispersion, and then add the aramid nanofiber dispersion prepared in step (1) to the carbon nanotube dispersion to obtain a modified carbon nanotube dispersion;

[0009] (3) adding graphene oxide to water, controlling the mass concentration of graphene oxide to be 0.005-1%, stirring to obtain a graphene dispersion, and adding the modified carbon nanotube dispersion of step (2) to the graphene dispersion to obtain an aramid carbon nanotube dispersion.

[0010] In the step (1), the aramid fiber has a length of 1 to 13 μm.

[0011] In the step (1), the mass ratio of water added to the ANF / DMSO solution to the solvent in the solution is 1:1 to 1:50.

[0012] In the step (2), the length of the carbon nanotube powder is greater than 5 um.

[0013] In the step (2), one or more selected from the group consisting of the compound of formula (1), TNRDIS, Disponer 983, FA 196, FX 9086, sodium glycocholate and its derivatives, sodium glycodeoxycholate and its derivatives, sodium chenodeoxycholate and its derivatives, sodium taurocholate and its derivatives, sodium deoxycholate and its derivatives, polyvinylpyrrolidone and its derivatives, polyvinyl caprolactam and its derivatives, polyvinyl acetamide and its derivatives, and sodium dodecylbenzene sulfonate,

[0014] (1)

[0015] Among them, R1 is -OH, -ONa, -NH3C2O2Na, -NHCH2COOH, -N2H8C4SO4Na or -NH5C2SO3Na, and R2 is -H, -OH, halogen, -OCH3, -OCH2CH3 or an ester group with 2-8 carbon atoms.

[0016] In the step (2), the stabilizer is selected from one or more of polymer stabilizers DNA / RNA, cellulose and its derivatives, and sodium carboxymethyl cellulose.

[0017] In the step (2), the aramid nanofiber aqueous dispersion and the carbon nanotube dispersion are mixed in a volume ratio of 1:1 to 1:2.

[0018] In the step (3), the modified carbon nanotube dispersion and the graphene dispersion are mixed in a volume ratio of 2.5:50 to 50:100.

[0019] The invention also provides an aramid carbon nano dispersion prepared by the method.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] (1) The present invention provides a mixed dispersion of modified CNT and GO, which can be used to prepare a thin film product with high thermal conductivity and excellent mechanical properties. It can be used on the surface of electronic components and exhibits excellent heat dissipation effect. Therefore, it has good application prospects in existing high power density devices and microelectronic integrated assembly equipment.

[0022] (2) The present invention introduces aramid nanofibers into the existing GO / CNT dispersion for the first time. First, carbon nanotubes are modified by using aramid nanofibers, and then mixed with graphene to obtain a corresponding aqueous dispersion. In this method, aramid nanofibers are introduced into the system in the form of aramid nanofiber aqueous dispersion, which can have a strong π-π interaction with GO and CNT. They can be further connected and bridged in the composite membrane material prepared therefrom to form a longitudinal bridging enhanced network, thereby better solving the problems of poor dispersibility of CNT in GO and poor mechanical properties of the film, and thereby preparing a composite membrane material with a high thermal conductivity.

[0023] (3) The present invention prepares modified carbon nanotubes by mixing aramid nanofiber aqueous dispersion and carbon nanotube dispersion. The entire modification system uses water as solvent. Similarly, graphene oxide dispersion also uses water as solvent. The raw materials are non-toxic, easy to obtain, and low in cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the cross-sectional morphology of the GO / CNT / ANF film in Example 4 (left: 10 μm, right: 5 μm).

[0025] Figure 2 This is the cross-sectional morphology of the GO / CNT film in Comparative Example 2 (left: 10 μm, right: 5 μm).

[0026] Figure 3 This is the cross-sectional morphology of the ANF / CNT film in Comparative Example 3 (left: 10 μm, right: 5 μm). DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0028] Embodiment 1:

[0029] 1g aramid (PPTA) fiber (1~13μm) and 1.5g KOH were added to 500ml dimethyl sulfoxide, and then 20ml deionized water was added, and then magnetically stirred for 4h to form an ANF / DMSO solution; deionized water was added to the ANF / DMSO solution at a volume ratio of 4:1, and magnetically stirred for 1h, and then washed with deionized water several times with the assistance of vacuum filtration to remove excess KOH and DMSO, and then dispersed evenly with a homogenizer at a speed of 20000rpm to obtain an aramid nanofiber dispersion.

[0030] 0.5 g of carbon nanotube powder (5 μm or more) was added to 100 ml of deionized water, and then 0.25 g of compound (2), 0.25 g of sodium deoxycholate, 0.25 g of DNA and 0.25 g of cellulose were added. After mixing, the mixture was dispersed by ball milling (ultrasound, three-roll milling, Dyno-mill grinding, stirring and extrusion and other methods can also be used instead of ball milling to achieve a good dispersion effect) to obtain a carbon nanotube dispersion.

[0031] (2)

[0032] The aramid nanofiber dispersion liquid was mixed with an equal volume of the carbon nanotube dispersion liquid, and the mixture was dispersed evenly by a homogenizer at a rotation speed of 10000 rpm to obtain a modified carbon nanotube dispersion liquid.

[0033] Graphene oxide was added to deionized water, and the mass concentration of graphene oxide was controlled to be 0.005%. After magnetic stirring for 2 hours, a graphene dispersion was obtained. Then, the modified carbon nanotube dispersion and the graphene dispersion were mixed at a volume ratio of 50%:50%, and magnetic stirring was performed for 4 hours to obtain a homogeneously dispersed aramid carbon nano dispersion.

[0034] Embodiment 2:

[0035] 1g aramid (PPTA) fiber (1~13μm) and 1.5g KOH were added to 500ml dimethyl sulfoxide, and then 100ml deionized water was added, and then magnetically stirred for 6h to form an ANF / DMSO solution; deionized water was added to the ANF / DMSO solution at a volume ratio of 1:1, and magnetically stirred for 2h, and then washed with deionized water several times with the assistance of vacuum filtration to remove excess KOH and DMSO, and then dispersed evenly with a homogenizer at a speed of 20000rpm to obtain an aramid nanofiber dispersion.

[0036] 2.0 g of carbon nanotube powder (5 μm or more) was added to 100 ml of deionized water, and then 0.5 g of compound (3), 0.5 g of polyvinyl pyrrolidone, 0.5 g of DNA and 0.5 g of cellulose were added, mixed and dispersed by ball milling to obtain a carbon nanotube dispersion.

[0037] (3)

[0038] The aramid nanofiber dispersion liquid was mixed with an equal volume of the carbon nanotube dispersion liquid, and the mixture was dispersed evenly by a homogenizer at a rotation speed of 10000 rpm to obtain a modified carbon nanotube dispersion liquid.

[0039] Graphene oxide was added to deionized water, and the mass concentration of graphene oxide was controlled to be 0.008%. After magnetic stirring for 3 hours, a graphene dispersion was obtained. Then, the modified carbon nanotube dispersion and the graphene dispersion were mixed at a volume ratio of 50%:50%, and magnetic stirring was performed for 4 hours to obtain a homogeneously dispersed aramid carbon nano dispersion.

[0040] Embodiment 3:

[0041] 1g aramid (PPTA) fiber (1~13μm) and 1.5g KOH were added to 500ml dimethyl sulfoxide, and then 20ml deionized water was added, and then magnetically stirred for 4h to form an ANF / DMSO solution; then 50ml deionized water was added to the ANF / DMSO solution at a volume ratio of 4:1, and magnetically stirred for 1h, and then washed with deionized water several times with the assistance of vacuum filtration to remove excess KOH and DMSO, and then dispersed evenly with a homogenizer at a speed of 20000rpm to obtain an aramid nanofiber dispersion.

[0042] 0.5 g of carbon nanotube powder (5 μm or more) was added to 100 ml of deionized water, and then 0.25 g of compound (2), 0.25 g of sodium deoxycholate, 0.25 g of DNA and 0.25 g of cellulose were added, mixed and dispersed by ball milling to obtain a carbon nanotube dispersion.

[0043] (2)

[0044] The aramid nanofiber dispersion was mixed with 2 times the volume of the carbon nanotube dispersion, and the mixture was dispersed evenly with a homogenizer at a rotation speed of 15000 rpm to obtain a modified carbon nanotube dispersion.

[0045] Graphene oxide was added to deionized water, and the mass concentration of graphene oxide was controlled to be 0.05%. After magnetic stirring for 2 hours, a graphene dispersion was obtained. Then, the modified carbon nanotube dispersion and the graphene dispersion were mixed at a volume ratio of 15%:85%, and magnetic stirring was performed for 4 hours to obtain a homogeneously dispersed aramid carbon nano dispersion.

[0046] Example 4: GO / CNT / ANF film

[0047] The aramid carbon nano dispersion of Example 1 was vacuum filtered and dried in an oven at 70° C. to form a film, thereby obtaining a GO / CNT / ANF film.

[0048] Comparative Example 1: GO / CNT / ANF film

[0049] The GO / CNT / ANF film was prepared in the same manner as in Example 1 and Example 4, except that the aramid nanofiber dispersion and the carbon nanotube dispersion were mixed in a volume ratio of 15%:85%, and the modified carbon nanotube dispersion and the graphene dispersion were mixed in a volume ratio of 25%:75%.

[0050] Comparative Example 2: GO / CNT film

[0051] The carbon nanotube dispersion and graphene dispersion were prepared in the same manner as in Example 1.

[0052] The carbon nanotube dispersion and the graphene dispersion were mixed in a mass ratio of 15%:85%, and magnetically stirred for 4 hours to obtain a homogeneously dispersed GO / CNT dispersion. The prepared solution was vacuum filtered and dried in an oven at 70°C to form a film, thereby obtaining a GO / CNT film.

[0053] Comparative Example 3: ANF / CNT film

[0054] The carbon nanotube dispersion was prepared in the same manner as in Example 1, and the aramid nanofiber aqueous dispersion was prepared in the same manner as in Example 2.

[0055] The aramid nanofiber aqueous dispersion was mixed with an equal volume of carbon nanotube dispersion, and dispersed evenly with a homogenizer at a speed of 10,000 rpm to obtain a CNT / ANF dispersion solution. The prepared solution was vacuum filtered and dried in an oven at 70°C to form a film, thereby obtaining an ANF / CNT film.

[0056] The GO / CNT / ANF films prepared in Example 4 and Comparative Example 1 were immersed in 100 ml of 25 mg / ml L-ascorbic acid solution, respectively, and reduced in a water bath at 80°C for 30 min. The films were taken out, washed with deionized water several times, and naturally air-dried. After that, the films were subjected to hot-press reduction treatment. The upper and lower plate temperatures of the double-plate hot press were set to 200°C. After preheating, the film samples were successively covered with transparent PI sheets on both sides, and the names were marked and clamped in steel plates. They were sent into the hot press, and the pressure was set to 10 MPa. After 15 min, the samples were taken out to obtain sample A and comparative sample I.

[0057] The GO / CNT film and ANF / CNT film obtained in the above-mentioned Comparative Example 2 and Comparative Example 3 were subjected to hot pressing reduction treatment respectively. The upper and lower plate temperatures of the double-plate hot press were set to 200°C. After preheating, the film samples were successively covered with transparent PI sheets on both sides. After being marked with names, they were clamped in steel plates and sent into the hot press. The pressure was set to 10 MPa. The samples were taken out after 15 minutes to obtain Comparative Samples II and III.

[0058] The above sample A and comparative samples I, II and III were tested as follows:

[0059] (1) Film morphology test

[0060] The results were observed using a field emission scanning electron microscope (FE-SEM) (Inspect-F, FEI, Finland) at an accelerating voltage of 15 kV. Figure 1 (Sample A), Figure 2 (Comparative Sample II) and Figure 3 (Comparative sample III).

[0061] in, Figure 1 The film materials shown have a well-layered structure, in which the rGO sheets are parallel to the film plane, and ANFs and CNTs appear between the rGO sheets, forming a well-structured network. Figure 2 The cross-sectional morphology of the GO film shown is a stacked layered structure with some gaps between graphene oxide layers. Carbon nanotubes are loaded on the surface of graphene oxide and form a connected network structure between graphene layers, effectively filling the air pores between graphene layers, but the filled network does not form a dense connection. Figure 3 The ANF / CNT network of SWCNT and ANF shown is tightly interwoven, which can evenly distribute the stress on the framework and improve the mechanical properties, but lacks the supporting structure of the layer.

[0062] (2) Thermal conductivity test

[0063] The thermal diffusion coefficient α of the film is measured by LFA467. The specific heat capacity Cp of the sample is tested by DSC, and the density ρ of the sample is measured by Archimedean principle: first weigh the weight of the sample in the air m1, then put the sample in ethanol solution, and weigh the weight of the sample in ethanol solution m2. The measurement environment is: 25℃, ethanol density 0.79 g / cm3. The formula can be used for calculation:

[0064] The thermal conductivity of the film is calculated as λ=α*ρ*Cp.

[0065] (3) Mechanical properties test

[0066] The mechanical properties of the films were tested using an American INSTRON universal material testing machine, and each group of samples was tested three times to obtain the average value.

[0067] The performance parameters of the test are shown in Table 1.

[0068] Table 1

[0069]

[0070] As can be seen from Table 1 above, the method of the present invention can prepare a composite thermally conductive film with low conductivity and high tensile strength, which meets the specific performance index system required for the heat dissipation components of electronic equipment. Comparative Example 1 Although a film with equivalent density and thermal conductivity can be prepared by changing the mixing volume ratio of the dispersion, its mechanical properties are significantly reduced, and the conductivity is increased. The reason may be that the dispersion performance of aramid fiber in graphene is deteriorated. Comparative Example 2 is the preparation process of GO / CNT film. Due to the introduction of graphene material, its thermal conductivity can reach 48.4939 W / m*k, but its mechanical properties are poor and the conductivity is high. Comparative Example 3 is the preparation process of ANF / CNT film. Due to the introduction of aramid fiber, the mechanical properties of the film are enhanced, and the conductivity is significantly increased.

[0071] In summary, the present invention actually provides a GO / CNT / ANF dispersion for preparing a film with a specific performance index system, and the thermal conductivity, tensile strength and electrical conductivity of the prepared film can meet the specific index range, namely: thermal conductivity at 25°C: 4.5~4.8W / m*k or more; density: 1.2~1.3 g / cm 3 ; Tensile strength: 60-65 MPa; Electrical conductivity: 11-12.5 S / cm. Since the index performance of the films of Comparative Examples 1 to 3 cannot meet the index system, they are not suitable for use in heat dissipation components of electronic equipment.

[0072] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing aramid carbon nano dispersion, characterized in that: The following steps are involved: (1) Aramid fiber and KOH are mixed with dimethyl sulfoxide in a mass ratio of 1:1 to 1:2, and stirred to form an ANF / DMSO solution. Water is then added to the ANF / DMSO solution in a volume ratio of water to the ANF / DMSO solution of 1:1 to 4:1, and stirred to obtain an ANF / DMSO / H2O solution. The aramid nanofiber dispersion is then obtained after suction filtration, water washing, and homogenization. (2) By weight, 0.005-0.05 parts of carbon nanotube powder, 0.005-0.1 parts of dispersant, 0.005-0.1 parts of stabilizer and 1 part of water are mixed and dispersed to prepare a carbon nanotube dispersion liquid, wherein the stabilizer is selected from one or more of polymer stabilizers DNA / RNA, cellulose and its derivatives, and sodium carboxymethyl cellulose. Then, the aramid nanofiber dispersion of step (1) is added to the carbon nanotube dispersion, and the mixture is mixed at a volume ratio of 1:1 to 1:2 to obtain a modified carbon nanotube dispersion; (3) adding graphene oxide to water, controlling the mass concentration of graphene oxide to be 0.005-1%, stirring to obtain a graphene dispersion, adding the modified carbon nanotube dispersion of step (2) to the graphene dispersion, and mixing them at a volume ratio of the modified carbon nanotube dispersion to the graphene dispersion of 2.5:50-50:100, to obtain an aramid carbon nano dispersion.

2. The method according to claim 1, characterized in that: In the step (1), the aramid fiber has a length of 1 to 13 μm.

3. The method according to claim 1, characterized in that: In the step (1), the mass ratio of water added to the ANF / DMSO solution to the solvent in the solution is 1:1 to 1:

50.

4. The method according to claim 1, characterized in that: In the step (2), the length of the carbon nanotube powder is greater than 5 um.

5. The method according to claim 1, characterized in that: In the step (2), the dispersant is selected from one or more of the compounds of the following formula (1), TNRDIS, Disponer 983, FA 196, FX 9086, sodium glycocholate and its derivatives, sodium glycodeoxycholate and its derivatives, sodium chenodeoxycholate and its derivatives, sodium taurocholate and its derivatives, sodium deoxycholate and its derivatives, polyvinylpyrrolidone and its derivatives, polyvinylcaprolactam and its derivatives, polyvinylacetamide and its derivatives, and sodium dodecylbenzenesulfonate. （1） Among them, R1 is -OH, -ONa, -NH3C2O2Na, -NHCH2COOH, -N2H8C4SO4Na or -NH5C2SO3Na, and R2 is -H, -OH, halogen, -OCH3, -OCH2CH3 or an ester group with 2-8 carbon atoms.

6. An aramid carbon nano-dispersion prepared by the method according to any one of claims 1 to 5.

Images