KR20130081448A - Composite material and method of producing the same - Google Patents

Abstract

PURPOSE: A composite material and a manufacturing method of the same are provided to obtain a composite material with superior thermal conductivity by mixing polyimide, graphene, carbon nanotubes, and silicon carbide (SiC) at the optimal rate. CONSTITUTION: A composite material comprises polyimde, graphene, carbon nanotubes, and silicon carbide. The carbon nanotubes are multi-walled carbon nanotubes. The ratio of the graphene, carbon nanotubes, and silicon carbide to the polyimde is 10:1-8:1. The ratio of the silicon carbide to the graphene and carbon nanotubes is 9:1-7:3. A manufacturing method of a composite material comprises the steps of: preparing polyimde, graphene, carbon nanotubes, and silicon carbide; preparing a solvent; dissolving the polyimide, graphene, carbon nanotubes, and silicon carbide into the solvent; and obtaining a composite material by removing the solvent from the mixed solution. [Reference numerals] (AA) Surface resistance (Ω/□); (BB) Graphene & carbon nanotube: SiC

Description

Composite material and method of producing the same

TECHNICAL FIELD This invention relates to a composite material. Specifically, It is related with the composite material containing polyimide and graphene, and its manufacturing method.

Polymers and polymer resins are used in various ways because of their unique characteristics, and applications and researches are being actively conducted in universities and industries. Aromatic polyimides have many useful properties such as high thermal stability, good mechanical properties, and low dielectric constants. Therefore, polyimide has very high applicability in microelectronics and can be used for preparing mixed gas separation membranes.

Graphene materials are also expected to be applicable to various fields. Graphene produced by the exfoliation of graphite is composed of sp2 hybrid bonds of carbon as a continuous chemical bond of carbon atoms. Graphene has a lower production price than carbon nanotubes. On the other hand, graphene has high electrical and thermal conductivity and high mechanical properties, so it is expected to be a representative nanomaterial that can replace carbon nanotubes.

Meanwhile, in order to take advantage of various materials, there is a growing interest in composite materials in which materials are composited. New composite applications require a basic understanding of it. The physical properties of composites should be taken into consideration to develop the devices on which new composites are based. For example, composites are often applied as a coating film on special substrates or composed of a multi-layered layered structure. Serious problems such as winding or warping, shifting, cracking, and delamination are caused by thermal inconsistencies, the physical properties of multi-layered or complex interfacial layers. The thermal dependence of the thermal expansion coefficient and residual stress in these composites should be studied to avoid mechanical property mismatches.

In order to commercialize a complex having various advantages, it is urgent to develop a manufacturing method that can efficiently identify and express the characteristics of the complex and easily prepare the complex.

Meanwhile, Korean Patent Publication No. 2011-0016289 discloses a carbon nanoplate composite prepared by using a carbon nanoplate which is graphene oxide or graphene as a material and chemically and physically dispersing it and then complexing the composite into a composite material using a dispersion. Is disclosed.

The present invention provides a composite material having excellent thermal conductivity and a method of manufacturing the same.

The present invention provides a composite material comprising polyimide, graphene, carbon nanotubes, and silicon carbide (SiC) and a method of manufacturing the same.

The present invention provides a composite material and a method of manufacturing the same, the thermal conductivity and the sheet resistance is adjusted according to the content of silicon carbide.

Composite materials according to embodiments of the present invention include polyimide, graphene, carbon nanotubes and silicon carbide.

The carbon nanotubes are multi-walled carbon nanotubes.

The ratio of the graphene, carbon nanotubes and silicon carbide to the polyimide is 10: 1 to 8: 1, and the ratio of the silicon carbide to graphene and carbon nanotubes is 9: 1 to 7: 3. .

The sheet resistance and thermal conductivity are controlled according to the content of the silicon carbide, and the sheet resistance and the thermal conductivity increase as the content of the silicon carbide increases.

Method for producing a composite material according to embodiments of the present invention comprises the steps of preparing a polyimide, graphene, carbon nanotubes and silicon carbide raw material; Preparing a solvent; Preparing a mixed solution by dissolving the polyimide, graphene, carbon nanotube and silicon carbide raw material in the solvent; And removing the solvent from the mixed solution to prepare a composite material.

Embodiments of the present invention can produce a composite material of polyimide, graphene, carbon nanotubes and silicon carbide in a simple and simple manner. In addition, various types of composite materials such as sheets and films can be easily produced.

According to embodiments of the present invention, the thermal conductivity and the sheet resistance can be adjusted according to the content of silicon carbide, and the thermal conductivity can be utilized in various electronic components and devices, such as excellent thermal conductivity.

1 is a process flow diagram illustrating a method of manufacturing a composite material according to embodiments of the present invention.
2 is a graph showing the sheet resistance characteristics of the composite material according to the embodiments of the present invention.
3 is a SEM photograph of a composite material according to embodiments of the present invention.
Figure 4 is a graph showing the thermal conductivity of the composite material according to embodiments of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various forms, and only the embodiments are intended to complete the disclosure of the present invention and to those skilled in the art. It is provided for complete information.

The composite material according to the embodiment of the present invention includes polyimide, graphene, carbon nanotubes and silicon carbide (SiC). Carbon nanotubes may use multi-walled carbon nanotubes (MWCNTs).

Polyimide is a high molecular material having an imide ring, and is mainly synthesized using aromatic anhydrides and diamines. Polyimide resins exhibit excellent heat resistance, chemical resistance, abrasion resistance and weather resistance based on the chemical stability of the imide ring, and also exhibit low thermal expansion rate, low breathability, and excellent electrical properties. It has been widely used in high temperature adhesives, engineering plastic materials, aerospace, microelectronics, optics, etc. by utilizing various applicable properties, and development of monomers and synthesis methods suitable for specific purposes is more diverse and sophisticated. As it progresses, its application is gradually expanding. Examples of the polyimide resin applied to the inside and outside of articles commonly encountered in the surroundings include flexible circuit boards mainly used inside mobile phones, alignment films and photoresists of LCD TVs and monitors, and O-rings used at high temperatures. In addition to industrial applications such as column chromatography for gas chromatography, a technique for producing Lang-muir-Blodgett (LB) film, which is a monolayer film of a molecular unit using polyimide resin, has been developed and reported. Polyimide can be divided into three types: ① straight chain thermoplastic, ② straight chain non-thermoplastic, and ③ thermosetting according to the molecular structure and molding processability of the finally obtained polymer solid. Straight chain thermoplastics are linear polymers having a molecular weight of 1 to 100,000, and are reversible thermoplastic resins capable of injection molding / extrusion molding. The straight chain non-thermoplastic type is a linear polymer having a molecular weight of 10,000 to 100,000 and cannot be melt kneaded because it has no melt flowability or is very bad, and is thus formed by compression / sintering or solution cast / desolvent method. The thermosetting property is obtained by curing reactive monomers (and a combination thereof) or an oligomer prepared by preliminarily polymerizing the monomer (s) and pressurizing the mixture by heating for a predetermined time to obtain a cured molded article which is three-dimensionally crosslinked. The oligomers are referred to as B stage polymers (molecular weights of about 300 to 3,000) and are solid at room temperature but soluble in a solvent and exhibit irreversible thermoplastic. In this embodiment, diamine, 5 (6) -amino-1- (4'aminophenyl) -1,3-trimethylinyne (5 (6) -amino-1- (4 'aminophenyl) -1, Soluble thermoplastic polyimide based on 3-trimethylindane) was used.

Graphene is a carbon nanomaterial with one layer of the surface layer of graphite stripped. In other words, graphite has a structure in which carbon layers are stacked in a hexagonal honeycomb shape, and graphene is the thinnest layer of graphite. Graphene, a carbon allotrope, is a nanomaterial composed of carbon number 6, such as carbon nanotubes and fullerenes. It has a two-dimensional planar shape and is extremely thin, about 0.2 nm, and has high physical and chemical stability. It is 100 times more electricity than copper, and can transfer electrons 100 times faster than single crystal silicon, which is mainly used as a semiconductor. The strength is more than 200 times stronger than steel, and more than twice the thermal conductivity of diamond, which boasts the highest thermal conductivity. In addition, it is excellent in elasticity and does not lose its electrical properties even when stretched or bent. Due to these characteristics, graphene is evaluated as a material that surpasses carbon nanotubes, which is emerging as a next-generation new material, and is more likely to be applied industrially since it has a uniform metallicity than carbon nanotubes. In addition, graphene is attracting attention as a future new material in the electronic information industry that can make bendable displays, electronic paper, wearable computers and the like.

Carbon nanotubes are tiny molecules with a diameter of only several to several tens of nanometers in which long carbons connected by hexagonal rings form a long shape. Carbon nanotubes are similar in electrical conductivity to copper, thermal conductivity is the best diamond in nature, and 100 times stronger than steel. Carbon fiber can be broken by only 1% deformation while carbon nanotubes can withstand 15% deformation. Carbon nanotubes have various properties depending on the shape of single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), and bundles. Among them, multi-walled carbon nanotubes are carbon nanotubes formed by concentric circles of 5 to 100 nm in diameter, 50 to 300 GPa in tension, 5.1 x 10 ^-8 Ω · m in electrical resistance, and 3000 W / m in thermal conductivity. It has a characteristic of about K.

Silicon carbide (SiC) is a material in which silicon (Si) and carbon (C) are combined in a 1: 1 ratio, and the strongest covalent property is second only to diamond (Moss hardness 9.2). Pure is a colorless transparent hexagonal plate crystal, which has a melting point of 2,700 ° C or higher and sublimes at 2,200 ° C. Usually it is brown or black crystals due to impurities. Silicon carbide has a variety of crystal polymorphs, and to distinguish it is classified into 3C-SiC, 4H-SiC, 6H-SiC, 15R-SiC. Different lamination cycles in a particular crystallographic direction (0001 direction in the hexagonal axis) result in the most advanced numbers of these names indicating these lamination cycles. For example, in the case of 3C-SiC, the three layers are periodically repeated as one unit, and are composed of four layers in 4H-SiC, six layers in 6H-SiC, and the like. Next, the English letter means the crystal axis system, C means cubic, H means hexagonal, and R means rhombohedral.

1 is a process flowchart of a composite material manufacturing method according to an embodiment of the present invention.

Referring to Figure 1, the composite material manufacturing method according to an embodiment of the present invention is a process for preparing a polyimide, graphene, carbon nanotubes, silicon carbide raw material, a process for preparing a solvent, graphene in the solvent, carbon nano Dissolving the tube, silicon carbide and polyimide to form a solution, and removing the solvent from the solution and obtaining a composite material. Since the composite material of the present invention is prepared by dissolving polyimide, graphene, carbon nanotubes, and silicon carbide in a solution, the materials are uniformly dispersed and can be manufactured in various forms such as sheets and films.

First, prepare raw materials. That is, polyimide, graphene, carbon nanotubes, and silicon carbide are prepared, respectively. The polyimide is diamine, 5 (6) -amino-1- (4'aminophenyl) -1,3-trimethylinyne (5 (6) -amino-1- (4'aminophenyl), as described above. Soluble thermoplastic polyimide based on) -1,3-trimethylindane) is used. In addition, graphene is obtained from graphite oxide prepared by modifying the Hummers method, which will be described in detail below. First, graphite is used by heat treatment at 500 ° C. and argon atmosphere to remove residual impurities. 5 g of powdered flake graphite and 2.5 g of sodium nitrate (NaNO ₃ ) are added to 100 ml of sulfuric acid (H ₂ SO ₄ ), followed by stirring for about 30 minutes. The reaction components require cooling around 0 ° C. in the ice reactor for safe reaction. While vigorous stirring is maintained, 15 g of potassium permanganate (KMnO ₄ ) is added to the mixture. At this time, the dosing rate is a small amount of 0.1g level over several dozen times in order not to exceed the temperature of the mixture 20 ℃. The ice bath is then removed and the mixture maintained at 32-38 ° C. for 30 minutes. As the reaction proceeds, the mixture becomes thicker as the bubbles shrink. After 20 minutes from this temperature, the mixture reached a paste-like paste state, releasing a small amount of gas, at which time the reaction became greyish brown. After 30 minutes, 250 ml of water is added to the paste and stirred slowly, followed by vigorous boiling and an increase in temperature up to 98 ° C. The brownish reaction is now held at high temperature for 15 minutes. The reaction is then further diluted with 700 ml of warm water (30-40 ° C.) and treated with 50 ml of 30% hydrogen peroxide (H ₂ O ₂ ) to reduce residual permanganate and manganese dioxide. Treatment with peroxide turns the reactant to a bright yellow color. The mixture diluted with distilled water is filtered through a filter paper having pores of 5 μm size to obtain a yellowish-brown cake-like result. The yellow-brown filter cake is washed at least three times with distilled water (250 mL x 3). The graphite oxide washed by centrifugation is taken and the washing process is completed when the pH of the wastewater reaches around 7. Graphite oxide diluted in distilled water at a concentration of 1 g / l breaks the weakened interlayer bonds of graphite oxide by sonication for about two hours, thereby bringing it into graphene oxide. Thereafter, an additional 1 ml of hydrazine hydrate per 100 mg of graphite oxide was added and refluxed for 24 hours to form reduced graphene. Finally, powdery graphene can be obtained by washing with distilled water, methanol, filtration and drying.

Carbon nanotubes use multi-walled carbon nanotubes, and CMP-310 series purchased from Hanwha Nanotech Corp. was used. The multi-walled carbon nanotubes used in the present invention have a diameter of 6 to 9 nm, and have excellent field emission characteristics, excellent electrical and thermal conductivity, high specific surface area, and high length / diameter ratio. Multi-walled carbon nanotubes exist in the form of bundles due to the prominent cohesion between tubes due to van der Waals forces. For the application, additional chemical processing to dismantle these bundles is essential. Therefore, in the present invention, the multi-walled carbon nanotubes and hydrogen peroxide (H ₂ O ₂ ) were formed into a mixture of 100mg / 100ml concentration, and then refluxed at 60 ° C. for 72 hours to surface and terminate the multi-walled carbon nanotubes. A hydroxyl group (OH) was predominantly produced.

Silicon carbide uses a powder having an average particle size of 20 to 30 nm. Silicon carbide powder was used as received from American elements.

The solvent is a material capable of dissolving polyimide, graphene, multi-walled carbon nanotubes and silicon carbide powder. As a solvent, for example, meta-cresol may be used.

Thus prepared graphene, multi-walled carbon nanotubes and silicon carbide powder and polyimide are dissolved or dispersed on a m-Cresol solvent to prepare a composite solution. For example, graphene, multi-walled carbon nanotubes, and silicon carbide were injected into a certain amount of meta-cresol and sonicated for about 1 hour, after which polyimide and the remaining meta-cresol were added, followed by mechanical sterling for about one day. Done. That is, the composite solution is subjected to sonication and stirring for dispersion and dissolution. Solid components (graphene, multi-walled carbon nanotubes and silicon carbide powder) relative to the solvent may be used in 5wt% to 15wt%. That is, the ratio of the solid component to the solvent may be determined according to the application method of the composite solution. In the case of spray coating, a low viscosity composite solution having a low content of the solid component may be used, and in the case of casting, a high content of the solid component may be used. High viscosity complex solutions can be used. In this case, when the content of the solid component is too low, less than 5wt%, the drying process performed after coating, that is, the time required for removing the solvent becomes long, and the probability of non-uniform drying increases, resulting in a decrease in process efficiency. . In addition, when the spray coating is used and the content of the solid component exceeds 15wt%, the viscosity may increase, causing clogging of the nozzle for coating, resulting in uneven film quality. In addition, the ratio of graphene, multi-walled carbon nanotubes and silicon carbide powder to polyimide is mixed in a ratio of 10: 1 to 8: 1, and uniformly dispersed by stirring and sonication on a solvent.

Moreover, after apply | coating a composite solution, it dries about 24 hours at the temperature of normal temperature-60 degreeC, for example.

Experimental Example

Polyimide, graphene, multi-walled carbon nanotubes and silicon carbide powder were dissolved in a meta-cresol solvent. In this case, in order to investigate the characteristics according to the content of silicon carbide, Experimental Example 1, in which silicon carbide was not mixed, and Experimental Examples 2 to 4 in which the content of silicon carbide was different, were prepared, respectively. The component ratios of these experimental examples are shown in the following table, and they were uniformly dispersed by stirring and sonication on the meta-cresol solvent.

Polyimide
(mg) Graphene & Multiwalled Carbon Nanotubes: SiC Graphene
(mg) Multi-walled Carbon Nanotubes
(mg) SiC (mg) Graphene + Multi-walled Carbon Nanotubes + SiC Experimental Example 1
600

10: 0 40 26.7 -

6.766.7 Experimental Example 2 9: 1 36 24 6.7 Experimental Example 3 8: 2 31.8 21.2 13 Experimental Example 4 7: 3 28.3 18.8 20

That is, graphene, multi-walled carbon nanotubes, and silicon carbide are added to 600 mg of polyimide in a predetermined ratio. Graphene and multi-walled carbon nanotubes to silicon carbide are prepared in a ratio of 10: 0 for Experimental Example 1, 9: 1 for Experimental Example 2, 8: 2 for Experimental Example 3, and 7: 3 for Experimental Example 4. In this case, Experimental Example 1 is prepared by mixing 40 mg of graphene and 26.7 mg of multi-walled carbon nanotubes, and Experimental Example 2 are prepared by mixing 36 mg of graphene, 24 mg of multi-walled carbon nanotubes, and 6.7 mg of silicon carbide. In addition, Experimental Example 3 was prepared by mixing graphene 31.8mg, multi-walled carbon nanotubes 21.2mg, silicon carbide 13mg, Experimental Example 4 mixed graphene 28.3mg, multi-walled carbon nanotubes 18.8mg, silicon carbide 20mg To prepare.

The composite solution of the composition was used after 3 hours of sonication and 24 hours of sterling, respectively, for dispersion and dissolution. In addition, the spacer was placed between the upper and lower glass in order to uniformly control the thickness of the film during film production, and the composite solution was injected. Drying is suitably in the temperature range of room temperature to 60 ° C, and breakage occurs at higher temperatures. The final sample has a thickness of 200 μm with a volume reduction following 24 hours of drying.

Experiment result

Figure 2 is a graph showing the sheet resistance according to the silicon carbide content of the composite material according to an embodiment of the present invention, it is the result of measuring the sheet resistance of Experimental Examples 1 to 4 in the air at 25 ℃. As shown, graphene and multi-walled carbon nanotubes: silicon carbide has a sheet resistance of 10: 0 from Experimental Example 1 to Experimental Example 2 of 9: 1, Experimental Example 3 of 8: 2, and Experimental Example 4 of 7: 3. This increases linearly. That is, Experimental Example 1, 2, 3, and 4 show the sheet resistance of 6.42E + 03, 1.52E + 04, 2.43E + 04, and 3.03E + 04kV / square, respectively. In comparison, the sheet resistance of the film containing only silicon carbide is 10 ⁷ GPa / s or more. Accordingly, the film of the composite material according to the present invention has a sheet resistance lower than that of the film containing only silicon carbide, but the sheet resistance increases as the content of silicon carbide increases.

3 is an electron micrograph (SEM) of the manufactured composite material, Figure 3 (a) is a photograph of the fracture surface, Figure 3 (b) is an enlarged photograph at a first ratio, Figure 3 (c) is It is a photograph enlarged by the 2nd ratio enlarged than 1 ratio. Graphene having a plate-like structure is difficult to discern in a polyimide matrix, but carbon nanotubes having a one-dimensional structure and granular silicon carbide are easily observed. The voids seen from the image can be reduced at low drying temperatures.

Figure 4 shows the thermal conductivity of the composite material according to the silicon carbide content. In the case where silicon carbide is not contained, the thermal conductivity is the smallest, and as the content of silicon carbide increases, the thermal conductivity gradually improves. In addition, the thermal conductivity at 50 ° C. was higher than that at 25 ° C. Such high thermal conductivity composite materials can be utilized as fillers for heat dissipating materials.

As described above, as the content of silicon carbide increases, sheet resistance increases and thermal conductivity also increases. That is, according to the content of silicon carbide, the electrical conductivity is lowered and the thermal conductivity is improved.

Although the technical spirit of the present invention has been described in detail according to the above embodiment, it should be noted that the above embodiment is for the purpose of description and not for the purpose of limitation. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention.

Claims (7)

As a composite material containing a plurality of components,
Composite materials comprising polyimide, graphene, carbon nanotubes and silicon carbide.
The composite material of claim 1, wherein the carbon nanotubes are multi-walled carbon nanotubes.
The composite material of claim 1, wherein a ratio of the graphene, carbon nanotubes, and silicon carbide to the polyimide is 10: 1 to 8: 1.
The composite material of claim 1, wherein the ratio of silicon carbide to graphene and carbon nanotubes is from 9: 1 to 7: 3.
The composite material of claim 4, wherein sheet resistance and thermal conductivity are controlled according to the content of the silicon carbide. The composite material of claim 5, wherein the sheet resistance and the thermal conductivity increase as the content of the silicon carbide increases.
As a method for producing a composite material,
Preparing a polyimide, graphene, carbon nanotube and silicon carbide raw material;
Preparing a solvent;
Preparing a mixed solution by dissolving the polyimide, graphene, carbon nanotube and silicon carbide raw material in the solvent; And
Removing the solvent from the mixed solution to produce a composite material.

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