Heat dissipating composition comprising nanoized carbon structure

Abstract

The present invention relates to a heat dissipation composition comprising a nano-sized carbon structure that exhibits excellent dispersibility and heat dissipation effects. The heat dissipation composition comprising a nanoscaled carbon structure according to the present invention has the effect of having excellent dispersibility and adhesion by including the nanoscaled carbon structure. The heat dissipation composition according to the present invention has the effect of preventing precipitation even during long-term storage, as the zeta potential is controlled within a certain range, thereby improving dispersion stability in a solvent. The heat dissipation composition according to the present invention includes a nano-sized carbon structure with controlled particle size and thickness, which is uniformly coated on the surface of a substrate, thereby improving heat dissipation performance.

Description

Technology Field

[0001] The present invention relates to a heat dissipation composition comprising a nano-sized carbon structure that exhibits excellent dispersibility and heat dissipation effects. Background Technology

[0003] As modern electronic products and industrial devices rapidly become more high-performance and miniaturized, heat generation is emerging as a serious technical challenge.

[0004] In particular, the amount of heat generated in mobile devices such as smartphones, tablets, and laptops is increasing due to the high performance of Application Processors (APs) and batteries, leading to product performance degradation, user inconvenience, and safety issues. To address these heat generation problems, conventional methods have utilized metal heat sinks, ceramic heat dissipation materials, thermally conductive polymers, and heat pipes. Among these, heat pipes are small components widely used to improve the heat dissipation characteristics of small electronic devices, consisting of a sealed metal tube structure filled with a refrigerant.

[0005] A heat pipe is a device that transfers heat using the evaporation and condensation of a refrigerant. It operates on the principle that when heat enters from the outside, the refrigerant in the evaporator evaporates and moves to the condenser, where it condenses to transfer heat to the outside. Through this system, small electronic devices feature a structure in which the evaporator is placed in contact with the heat-generating part, and the condenser is positioned at the part requiring heat transfer to the outside, thereby transferring the heat generated from the heat-generating part to the external environment.

[0006] Currently, refrigerants used in heat pipes are mainly DI (Deionized Water) or ethanol, and very small amounts are used. Depending on the internal volume of the heat pipe, less than 10 ml of refrigerant is used in most cases, and in particular, about 0.5 mg of DI water is used in heat pipes applied to mobile devices. In addition, the structure of heat pipes for mobile devices is very miniaturized, with a thickness of less than 0.4 mm and a length of less than 80 mm.

[0007] The key factor determining the heat transfer efficiency of a heat pipe is the physical properties of the refrigerant, and in particular, specific heat and thermal conductivity play an important role.

[0008] Comparing the specific heats of water and ethanol, water has a specific heat of 1 cal / g·K (4.2 J / g·°C), while ethanol has a specific heat of 0.56 cal / g·K (2.46 J / g·°C). Generally, in refrigeration cycles, refrigerants with low freezing points, such as R22 and R134a, are used because the evaporator temperature becomes sub-zero; however, their specific heats are 1.30 J / g·K and 1.51 J / g·K, respectively, which are lower than those of water. Since heat pipes operate at room temperature, there is no need to use refrigerants with low freezing points. For room-temperature chillers, using ethanol instead of water as a refrigerant can increase the heat transfer rate, thereby improving cooling efficiency. To maximize the heat transfer effect with a small amount of refrigerant used within a heat pipe, it is important to use a material with a low specific heat and, at the same time, a material with high thermal conductivity. Reducing the latent heat region during the phase change of the refrigerant is key to increasing the heat transfer effect, and adding a material with excellent thermal conductivity to the refrigerant is an effective method for this.

[0009] As can be seen from the graph illustrating the phase change of water in Fig. 1, using a material with good thermal conductivity results in a reduction in the latent heat region, which causes the vaporization stage to proceed earlier. In other words, when a highly conductive material is added to the refrigerant, the region in which the refrigerant vaporizes to transfer heat from the condenser to the evaporator is reduced, thereby increasing the heat conduction effect and improving the heat dissipation effect. Additionally, adding additives to the refrigerant reduces the supercooling region, leading to increased cooling efficiency and the ability to expand the temperature range that needs to be transferred. Generally, mixed refrigerants are used to increase the cooling effect; in this case, a method is employed to enhance the cooling effect by using refrigerants with different operating temperature ranges.

[0010] However, there are several technical challenges to commercialize general thermally conductive materials as refrigerant additives for heat pipes.

[0011] First, there is the problem of difficulty in ensuring dispersibility. Conventional thermally conductive particles tend to aggregate easily in refrigerant solvents such as water or ethanol, making it difficult to prepare a uniform dispersion. In particular, when using micro-sized particles, dispersion stability in the solvent is very low, causing rapid precipitation, which leads to the formation of a non-uniform distribution inside the heat pipe. Since the amount of refrigerant used in the heat pipe is very small (approximately 0.5 mg), if dispersion stability is not ensured, the additive becomes concentrated in only certain areas of the heat pipe, resulting in a problem where the heat transfer path becomes non-uniform.

[0012] Second, it is difficult to ensure affinity for ethanol and DI water. Since water and ethanol, used as refrigerants in heat pipes, are both polar solvents, additives must also be hydrophilic to ensure excellent dispersibility; however, typical thermally conductive particles are hydrophobic, making it difficult to disperse them in polar solvents.

[0013] Third, there is a sedimentation problem during long-term operation. Since heat pipes must operate continuously throughout the product's lifespan, the dispersion stability of particles added to the refrigerant must be maintained for a long period. However, existing thermally conductive particles settle over time and accumulate on the inner walls of the heat pipe, which hinders the circulation of the refrigerant and reduces heat transfer efficiency.

[0014] Fourth, there is a problem with internal pipe blockage in the heat pipe. Heat pipes for mobile devices have very narrow flow paths with a thickness of less than 0.4 mm, and if additives with large particle sizes are used, they can block the internal wick structure and hinder the capillary flow of the refrigerant.

[0015] Fifth, there is a problem with the difficulty of controlling the zeta potential. To ensure the dispersion stability of nanoparticles, the zeta potential on the particle surface must be ± 30mV or higher, but general thermally conductive particles find it difficult to satisfy this condition. When the zeta potential is low, the electrostatic repulsion between particles is insufficient, leading to aggregation, which reduces dispersion stability in the refrigerant.

[0016] Therefore, there is a need to develop heat dissipation compositions applicable to various heat transfer systems, including heat pipe refrigerant additives. Prior art literature

[0018] Korean Registered Patent No. 10-1897110, Korean Published Patent No. 10-2015-0107074 The problem to be solved

[0019] Accordingly, the inventors of the present invention completed the present invention by researching and striving to develop a heat dissipation composition capable of exhibiting excellent heat dissipation performance, and by discovering that a heat dissipation composition having excellent dispersibility and adhesion can be provided by including a nano-sized carbon structure.

[0020] The objective of the present invention is to provide a heat dissipation composition comprising a nano-sized carbon structure applicable to various fields, including refrigerants for cooling systems, home appliances, automobiles, and industrial equipment. means of solving the problem

[0022] The present invention relates to a heat dissipation composition comprising a nano-sized carbon structure.

[0023] The above nanoscaled carbon structure may be one or more selected from the group consisting of nanoscale graphene oxide, nanoscale graphene reduction, nanoscale graphene oxide variants, nanoscale graphene reduction variants, and graphene quantum dots.

[0024] The above nanoscaled carbon structure may have a zeta potential range of -100 to -30 mV.

[0026] The nano-sized carbon structure may have a D50 of 50 nm or less.

[0027] The above nano-sized carbon structure may have a thickness of less than 5 nm.

[0028] The above composition can be used as a refrigerant or refrigerant additive for a cooling system. Effects of the invention

[0030] The heat dissipation composition comprising a nanoscaled carbon structure according to the present invention has the effect of having excellent dispersibility and adhesion by including the nanoscaled carbon structure.

[0031] The heat dissipation composition according to the present invention has the effect of preventing precipitation even during long-term storage, as the zeta potential is controlled within a certain range, thereby improving dispersion stability in a solvent.

[0032] The heat dissipation composition according to the present invention includes a nano-sized carbon structure with controlled particle size and thickness, which is uniformly coated on the surface of a substrate, thereby improving heat dissipation performance.

[0033] The heat dissipation composition according to the present invention can be used as a refrigerant in a cooling system, and thus has the effect of being applicable to various industrial fields. Brief explanation of the drawing

[0035] Figure 1 is a graph illustrating the changes in the state of water. Figure 2 is a TEM image of nano graphene oxide prepared in the preparation example of the present invention. Figure 3 is a graph showing the particle size of nano graphene oxide produced in the manufacturing example of the present invention. Figure 4 is a graph showing the measured zeta potential of nano-graphene oxide prepared in the preparation example of the present invention. Figure 5 is a graph showing the difference between the fiber surface temperature and the internal temperature of the heat dissipation fiber of Example 1 for evaluating heat dissipation performance. Figure 6 is a graph showing the difference between the fiber surface temperature and the internal temperature of the heat dissipation fiber of Example 2 for evaluating heat dissipation performance. Figure 7 is a graph showing the difference between the heat source temperature and the fiber surface temperature of the heat dissipation fiber of Example 1 for evaluating heat dissipation performance. Figure 8 is a graph showing the difference between the heat source temperature and the fiber surface temperature of the heat dissipation fiber of Example 2 for evaluating heat dissipation performance. Specific details for implementing the invention

[0036] The present invention will be described in detail below. Terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0038] The present invention is characterized by a heat dissipation composition comprising a nano-sized carbon structure.

[0039] The above nanoscaled carbon structure may be one or more selected from the group consisting of nanoscale graphene oxide, nanoscale graphene reduction, nanoscale graphene oxide variants, nanoscale graphene reduction variants, and graphene quantum dots.

[0041] The above nano graphene oxide can have the structure of Chemical Formula 1 below.

[0042] [Chemical Formula 1]

[0043]

[0044] The above graphene oxide may include a structure in which a functional group containing an oxygen atom, such as a carboxyl group, a hydroxyl group, or an epoxy group, is bonded to the graphene, and may include aminated graphene oxide or pegylated graphene oxide as a variant.

[0046] The above nano-reduced graphene can have the structure of Chemical Formula 2 below.

[0047] [Chemical Formula 2]

[0048]

[0050] The above nano graphene oxide or nano graphene reduction may be manufactured through generally known graphene oxide manufacturing methods such as the Hummus method, Taylor method, and Brody method, but is not limited thereto.

[0051] The above nano-sized carbon structure may be included in the total composition at a concentration of 0.001 to 1 weight%, preferably 0.005 to 0.5 weight%, and most preferably 0.01 to 0.1 weight%.

[0052] The above nanoscaled carbon structure may have a zeta potential range of -100 to -30 mV, preferably the zeta potential range may be -80 to -35 mV, and more preferably -60 to -40 mV.

[0053] The zeta potential mentioned above serves as an indicator of the charge state on the particle surface; as the absolute value increases, the electrostatic repulsion between particles increases, which can improve dispersion stability. Specifically, if the zeta potential is less than -100 mV, the charge on the particle surface becomes excessively high, which may lead to unstable interactions with the solvent, while if it exceeds -30 mV, the repulsion between particles is insufficient, which may result in aggregation.

[0054] The above nano-sized carbon structure may have a D50 of 50 nm or less, preferably 1 to 20 nm, and more preferably 5 to 15 nm. The above D50 refers to the particle size at the point where the cumulative curve of the particle size distribution becomes 50% when the cumulative curve is obtained with the total weight set to 100%. With the above particle size, dispersibility is maximized, and variations in heat dissipation performance can be minimized.

[0055] The above particle size can be measured through Dynamic Light Scattering (DLS), Centrifuging Methods (CPS), or Transmission Electron Microscopy (TEM) analysis.

[0056] The above nano-sized carbon structure may have a thickness of less than 5 nm, preferably 0.1 to 3 nm, and more preferably 0.5 to 2 nm.

[0057] The heat dissipation composition according to the present invention can be prepared by including the step of dispersing a nano-sized carbon structure in a solvent.

[0058] The above solvent may be one or more of water, ethanol, isopropanol, acetone, toluene, dimethylformamide (DMF), and dimethyl sulfoxide (DMSO).

[0059] In one embodiment, the dispersion step may be performed by one or more methods of ultrasonic treatment, ball milling, high-pressure homogenization, and shear mixing.

[0060] Specifically, the ultrasonic treatment can be performed at a frequency of 20 to 40 kHz for 10 minutes to 2 hours, thereby allowing the nano-sized carbon structure (110) to be uniformly dispersed in the solvent.

[0061] The above ball milling can be performed using zirconia balls or alumina balls at a speed of 100 to 500 rpm for 1 to 24 hours.

[0062] The above high-pressure homogenization can be performed at a pressure of 100 to 1000 bar and can effectively crush aggregates of carbon structures.

[0063] The above shear mixing can be performed at a speed of 1,000 to 10,000 rpm for 10 minutes to 1 hour.

[0064] The heat dissipation composition of the present invention can be used as a refrigerant or refrigerant additive in a cooling system.

[0065] The above cooling system may be one or more of an electronic device cooling system, an automotive cooling system, or an industrial equipment cooling system.

[0066] Specifically, the above electronic device cooling system can be applied to computer CPU coolers, graphics card coolers, smartphone heat pipes, etc.

[0067] The above automotive cooling system can be applied to engine coolant, battery cooling systems, power electronics cooling systems, etc.

[0068] The above industrial facility cooling system can be applied to cooling systems in power plants, manufacturing plants, data centers, etc.

[0070] Meanwhile, the heat dissipation composition of the present invention can be applied to manufacture heat dissipation fibers by coating them onto a fiber substrate.

[0071] The fiber substrate may be a natural fiber, a synthetic fiber, or a blend thereof. Specifically, the natural fiber may be one or more of cotton, wool, silk, and linen. The synthetic fiber may be one or more of polyester (PET), nylon, acrylic, polypropylene, and spandex. The fiber substrate may be a jersey fabric, which has excellent breathability and flexibility, making it suitable for application to speaker grilles of home appliances, etc.

[0072] The method for manufacturing the heat dissipation fiber may include the step of applying the heat dissipation composition to a fiber substrate. The application method may be one or more of dip coating, spray coating, doctor blade coating, and roll coating.

[0073] Specifically, the above-mentioned dip coating is a method of forming a coating layer by immersing a fiber substrate in a heat dissipation composition and then withdrawing it, which allows for simple and large-area coating.

[0074] The above spray coating is a method of spraying a heat dissipation composition onto the surface of a fiber substrate through a sprayer, and the coating thickness can be easily controlled.

[0075] The above doctor blade coating is a method of uniformly applying a heat dissipation composition to the surface of a fiber substrate using a blade, and allows for precise thickness control. The above roll coating is a method of transferring a heat dissipation composition onto the surface of a fiber substrate by applying it to a rotating roll, and allows for continuous production.

[0076] The method for manufacturing the heat-dissipating fiber described above may further include a step of drying the coated fiber substrate. The drying step may be performed by one or more methods among natural drying at room temperature, oven drying at 50 to 150°C, infrared drying, and hot air drying. Specifically, the oven drying may be performed at 80 to 120°C for 10 minutes to 1 hour, and the solvent may be completely removed to improve the adhesion of the coating layer.

[0077] When manufacturing the above-mentioned heat dissipation fiber, the heat dissipation composition may further include a water-repellent agent. The water-repellent agent may serve to help uniformly coat the surface of the fiber with nano-sized carbon structures and may improve the adhesion between the fiber and the carbon structures.

[0078] The above water repellent may be one or more of a fluorine-based water repellent, a silicone-based water repellent, a paraffin-based water repellent, and a wax-based water repellent.

[0079] Specifically, the above-mentioned fluorine-based water-repellent agent is a compound containing a perfluoroalkyl group, and has low surface tension, allowing it to form a uniform coating layer on the fiber surface.

[0080] The above silicone-based water repellent may include silicone compounds such as polydimethylsiloxane (PDMS) and can provide excellent heat resistance and flexibility.

[0081] The above-mentioned paraffin-based water repellent is composed of long-chain hydrocarbons and can be inexpensive and environmentally friendly.

[0082] The above wax-based water repellent may include natural or synthetic wax and can impart a soft touch to the fiber.

[0083] The above water-repellent agent may be used in an amount of 1 to 100 parts by weight per 100 parts by weight of the heat-dissipating composition, preferably in an amount of 10 to 80 parts by weight, and most preferably in an amount of 20 to 50 parts by weight.

[0085] Hereinafter, the present invention will be described in detail through examples and experimental examples to specifically explain the invention. However, the embodiments according to the present invention may be modified in various different forms, and the scope of the present invention should not be interpreted as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the invention to those with average knowledge in the art.

[0087] Preparation Example: Preparation of nano graphene oxide

[0088] Uncontaminated graphene oxide (GO) was synthesized using the modified Taylor's method.

[0089] Specifically, high-purity graphite, sodium nitrate (NaNO3), and sulfuric acid (H2SO4) were mixed, and potassium permanganate (KMnO4) was added to the mixture over an ice bath or a cooled bath and subjected to a constant rotational speed (causing a swelling effect of the graphite due to rotation) for a certain period of time. Afterward, a constant rotational force was applied for a certain period of time to provide shear force to the expanded graphite to facilitate interlayer separation. Subsequently, hydrogen peroxide (H2O2) was added to the mixture and centrifuged to produce graphene oxide. The produced graphene oxide was freeze-dried to prepare dried graphene oxide.

[0090] Nano-graphene oxide (nano-GO) was prepared by vacuum-filtering the prepared graphene oxide through a cellulose nitrate membrane filter (0.45 μm, GE Healthcare). In the example, it was prepared based on a 1% nanoGO concentration solution (3 mg / mL), and the concentration (%) was adjusted as needed.

[0092] Experimental Example 1: Characterization of Nano Graphene Oxide

[0093] To identify the size and shape of the nano-GO prepared in the above preparation example, transmission electron microscopy (TEM) imaging analysis was performed.

[0094] As a result of the analysis above, the size of the nano graphene oxide prepared in the above preparation example was confirmed to be an average of 6 nm (Fig. 2), and the D50 was confirmed to be 12 nm (Fig. 3).

[0095] In addition, zeta potential analysis was performed to confirm the dispersion state of the manufactured nano graphene oxide, and it was confirmed that the zeta potential was -40 mV (Fig. 4), indicating that the nano graphene oxide itself exhibits excellent dispersion stability.

[0097] Example 1: Preparation of heat dissipation composition and heat dissipation fiber 1

[0098] A heat dissipation composition was prepared by dispersing 0.05 wt% of the nano graphene oxide of Preparation Example 1 in water, and then a heat dissipation coating composition was prepared by mixing the heat dissipation composition with a paraffin-based water repellent in a weight ratio of 1:1.

[0099] A heat-dissipating fiber was manufactured by coating the above heat-dissipating coating composition onto a PET jersey fabric using a dip coating method, and then drying it in an 80°C oven for 30 minutes.

[0101] Example 2: Preparation of heat-dissipating fibers with different water-repellent contents

[0102] A heat-dissipating fiber was manufactured in the same manner as in Example 1 above, except that the mixing ratio of the heat-dissipating composition and the paraffin-based water-repellent agent was 5:1.

[0104] Experimental Example 2: Evaluation of Heat Dissipation Performance

[0105] The heat source was installed inside the sealed system and positioned at the center of the bottom of the system.

[0106] A thermocouple was installed in the center of the internal space of the system to measure the internal temperature.

[0107] Next, the heat dissipation fiber specimens of Examples 1 and 2 were mounted in the opening at the top of the system, and a thermocouple was attached to the surface of the specimen to measure the surface temperature.

[0108] After setting the temperature of the heat source to 43℃ and sealing the system, the internal temperature of the system, the fiber surface temperature, and the internal temperature were measured at 10-minute intervals for 120 minutes starting from the initial time point (0 min). The above evaluation was repeated at least twice for each composition concentration to confirm reproducibility.

[0109] Graphs measuring the difference between the surface temperature and the internal temperature of the fiber are shown in FIG. 5 (Example 1) and FIG. 6 (Example 2).

[0110] As a result, the temperature difference between the fiber surface and the interior was found to be 5°C or less. In particular, in the case of Example 2, it was confirmed that the temperature difference was reduced, confirming that the heat generated inside is effectively transferred to the outside by the coating of the heat dissipation composition of the present invention.

[0111] In addition, graphs measuring the difference between the heat source temperature and the fiber surface temperature are shown in FIG. 7 (Example 1) and FIG. 8 (Example 2).

[0112] The smaller the difference between the heat source temperature and the fiber surface temperature, the better the heat dissipation performance. It was confirmed that the heat dissipation fiber according to the present invention exhibits excellent heat dissipation performance, with a temperature difference of 3.5℃ or less.

Claims

Claim 1 A heat dissipation composition characterized by including a nano-sized carbon structure. Claim 2 A heat dissipation composition according to claim 1, characterized in that the nano-sized carbon structure is one or more selected from the group consisting of nano-oxidized graphene, nano-reduced graphene, nano-oxidized graphene variants, nano-reduced graphene variants, and graphene quantum dots. Claim 3 A heat dissipation composition according to claim 1, wherein the nano-sized carbon structure has a zeta potential range of -100 to -30 mV. Claim 4 A heat dissipation composition according to claim 1, wherein the nano-sized carbon structure has a D50 of 50 nm or less. Claim 5 A heat dissipation composition according to claim 1, characterized in that the nano-sized carbon structure has a thickness of less than 5 nm. Claim 6 A heat dissipation composition according to claim 1, characterized in that the composition is used as a refrigerant or refrigerant additive in a cooling system.

Images