GRAPHENE OXIDE-NANODIAMOND COMPOSITE, MANUFACTURING METHOD THEREOF, AND NANOFLUID INCLUDING THE SAME

Abstract

Disclosed herein is a composite comprising a graphene oxide and a nanodiamond that is chemically bonded on a surface of the graphene oxide.

Claims

1. A composite, comprising: a graphene oxide; and a nanodiamond that is bonded on a surface of the graphene oxide.

2. The composite of claim 1, wherein the graphene oxide and the nanodiamond are chemically bonded by a linker group selected from the group consisting of an alkylene, a cycloalkylene, a bivalent aromatic ring group, —CO—O, —S—, —O—, —CO—, —SO.sub.2—, —N(R)— wherein R is a hydrogen atom or an alkyl group, and a combination thereof.

3. The composite of claim 1, wherein the graphene oxide and the nanodiamond are bonded by —CO—O—.

4. The composite of claim 1, wherein a thickness of the graphene oxide is about 1 to 2 nm, and a diameter thereof is about 1 to 3 μm.

5. The composite of claim 1, wherein an average diameter of the nanodiamond is about 3 to 10 nm.

6. The composite of claim 1, wherein an amount of about 50 to 150 parts by weight of the nanodiamond based on 100 parts by weight of the graphene oxide are chemically bonded.

7. A method of manufacturing a composite comprising a graphene oxide and a nanodiamond, comprising: preparing a nanodiamond; attaching a functional group on a surface of the nanodiamond by heat-treating the nanodiamond; dispersing the nanodiamond comprising the functional group in a first solvent to prepare a nanodiamond dispersion; dispersing a graphene oxide in a second solvent to prepare a graphene oxide dispersion; and mixing the graphene oxide dispersion and the nanodiamond dispersion; and forming a bond between the graphene oxide and the nanodiamond.

8. The method of claim 7, wherein an average diameter of the nanodiamond is about 3 to 10 nm.

9. The method of claim 7, wherein the functional group is attached on the surface of the nanodiamond by heat-treating the nanodiamond at a temperature of about 400° C. to 500° C. for about 1 to 3 h.

10. The method of claim 7, wherein the functional group attached on the surface of the nanodiamond is —COOH.

11. The method of claim 7, wherein the nanodiamond dispersion further comprises a catalyst.

12. The method of claim 11, wherein the catalyst is one or more selected from the group consisting of N,N′-dicyclohexylcarbodiimide (DCC) and 4-(dimethyl amino)pyridine (DMAP).

13. The method of claim 7, wherein the first solvent is one or more selected from the group consisting of an amide-based solvent, an ether-based solvent, and a halogenated solvent.

14. The method of claim 7, wherein when the graphene oxide is dispersed in the second solvent, a hydroxyl group or an alkyl group is attached on the surface of the graphene oxide.

15. The method of claim 7, wherein when the graphene oxide is dispersed in the second solvent, a thickness of the graphene oxide is about 1 to 2 nm, and a diameter thereof is about 1 to 3 μm.

16. The method of claim 7, wherein an amount of about 50 to 150 parts by weight of the nanodiamond based on 100 parts by weight of the graphene oxide are mixed with the graphene oxide to form the bond between the graphene oxide and the nanodiamond.

17. The method of claim 7, wherein the bond between the graphene oxide and the nanodiamond is formed by esterification reaction.

18. A nanofluid comprising a complex of claim 1 and a polar fluid.

19. The nanofluid of claim 18, wherein the polar fluid is water, ethylene glycol, propylene glycol, or a combination thereof.

20. A vehicle comprising a nanofluid of claim 18.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] It should be understood that the accompanying drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment. In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing.

[0047] FIG. 1 illustrates an exemplary composite of a graphene oxide and a nanodiamond according to an exemplary embodiment of the present invention.

[0048] FIG. 2 illustrates an exemplary manufacturing method of an exemplary composite comprising a graphene oxide and a nanodiamond according to an exemplary embodiment of the present invention.

[0049] FIG. 3 illustrates a result of infrared spectroscopic analysis (FT-IR) of an exemplary nanodiamond before heat treatment in an exemplary embodiment of the present invention.

[0050] FIG. 4 illustrates a result of infrared spectroscopic analysis (FT-IR) of an exemplary nanodiamond after heat treatment in an exemplary embodiment of the present invention.

[0051] FIG. 5 illustrates an infrared spectroscopic analysis (FT-IR) result of an exemplary composite comprising a graphene oxide and a nanodiamond manufactured according to an exemplary embodiment of the present invention.

[0052] FIG. 6 illustrates a scanning electron microscope (SEM) photograph of an exemplary composite comprising a graphene oxide and a nanodiamond manufactured according to an exemplary embodiment of the present invention.

[0053] FIG. 7 illustrates a metal corrosion test result for an exemplary nanofluid in an experimental example according to an exemplary embodiment of the present invention.

[0054] FIG. 8 illustrates a photograph of an exemplary nanofluid manufactured in an experimental example according to an exemplary embodiment of the present invention.

[0055] FIG. 9 illustrates a metal corrosion test result of a nanofluid in a comparative example.

DETAILED DESCRIPTION

[0056] The advantages and features of the present invention and the methods for accomplishing the same will be apparent from the exemplary embodiments described hereinafter with reference to the accompanying drawings. However, the present invention is not limited to the exemplary embodiments described hereinafter, but may be embodied in many different forms. The following exemplary embodiments are provided to make the invention of the present invention complete and to allow those skilled in the art to clearly understand the scope of the present invention, and the present invention is defined only by the scope of the appended claims. Throughout the specification, the same reference numerals denote same constituent elements.

[0057] In some exemplary embodiments, detailed description of well-known technologies will be omitted to prevent the invention of the present invention from being interpreted ambiguously. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. In addition, throughout the specification, unless explicitly described to the contrary, the word “comprise” and variations such as “comprises” or “comprising” will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. Further, as used herein, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0058] Unless specifically stated or obvious from context, as used herein, the term “about” is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from the context, all numerical values provided herein are modified by the term “about.”

[0059] It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles.

[0060] Throughout the specification, unless otherwise defined, “average diameter” refers to an average of the longest diameter of each particle in the group.

[0061] As used herein, unless otherwise defined, “substituted” refers to a group substituted with a C1 to C30 alkyl group, a C1 to C10 alkylsilyl group, a C3 to C30 cycloalkyl group, a C6 to C30 aryl group, a C2 to C30 heteroaryl group, a C1 to C10 alkoxy group, a fluoro group, a C1 to C10 trifluoroalkyl group such as trifluoromethyl group, or a cyano group.

[0062] As used herein, unless otherwise defined, “alky group” includes “saturated alkyl group” having no alkene or alkyne group, or “unsaturated alkyl group” having at least one alkene or alkyne group. The “alkene group” means a substituent having at least two carbon atoms bound to each other via at least one carbon-carbon double bond, and “alkyne group” means a substituent having at least two carbon atoms bound to each other via at least one carbon-carbon triple bond. The alkyl group may be branched, linear, or cyclic.

[0063] The alkyl group may be a C1 to C20 alkyl group, more particularly a C1 to C6 lower alkyl group, a C7 to C10 medium alkyl group, or a C11 to C20 higher alkyl group.

[0064] For example, a C1 to C4 alkyl group means an alkyl group having 1 to 4 carbon atoms in its alkyl chain, and is selected from the group consisting of methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl.

[0065] Typical alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, ethenyl, propenyl, butenyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, or the like.

[0066] According to an exemplary embodiment of the present invention, a graphene oxide-nanodiamond complex includes a graphene oxide and a nanodiamond attached on the surface of the graphene oxide. For example, the graphene oxide and the nanodiamond may be chemically bonded, for example, by a covalent bond, ionic bond, or the like.

[0067] According to an exemplary embodiment of the present invention, provided is a composite of including the graphene oxide and the nanodiamond complex, which may be chemically bonded nanomaterials. The graphene oxide may have high dispersion in a polar solution and high thermal conductivity but low corrosion stability, and the nanodiamond may have high metal corrosion stability and high thermal conductivity but low dispersion to a polar solution. According to an exemplary embodiment of the present invention, the composite comprising the graphene oxide and nanodiamond may be used as a nanomaterial to manufacture a nanofluid which satisfies both dispersion stability and metal corrosion stability and has high thermal conductivity.

[0068] Generally, a nanodiamond, as used herein, may be formed by an explosive reaction of graphite, and may be formed in fine nanoparticles having a size from about [ ] to about [ ]. The nanodiamond generally may contain various functional groups on the surface thereof, unlike a general diamond.

[0069] Generally, the nanodiamond does not have a complete SP.sup.3 structure and may include various functional groups. Particularly, functional groups may become various depending on conditions of an explosive reaction. For example, the surface of the nanodiamond may have a functional group such as alkyl, cycloalkyl, alkenyl, —COOH, —SH, —OH, —COH, and —SO.sub.2H—N(R)H (R is a hydrogen atom or an alkyl group). However, for a selective chemical reaction, one functional group among surface reaction groups may be modified to be predominant, and the nanodiamond and the graphene oxide may be chemically bonded through the functional group and the chemical reaction with the functional group formed on the surface of the graphene oxide.

[0070] Particularly, the graphene oxide and the nanodiamond may be chemically bonded through an alkylene group, a cycloalkylene group, a bivalent aromatic ring group, —CO—O, —S—, —O—, —CO—, —SO.sub.2—, —N(R)— (R is a hydrogen atom or a alkyl group), and a bivalent linking group which is a complex thereof. More particularly, the graphene oxide and the nanodiamond may be chemically bonded through —CO—O—.

[0071] FIG. 1 illustrates an exemplary graphene oxide-nanodiamond complex according to an exemplary embodiment of the present invention. As shown in FIG. 1, a chemical bond by —CO—O— may be formed by an esterification reaction of a —COOH functional group introduced on a surface of a nanodiamond and an —OH functional group introduced on a surface of a graphene oxide. However, the present invention is not limited thereto, and it may be bonded through various bivalent linking groups.

[0072] Since a graphene oxide (GO) has a planar structure, it may provide sufficient space for attaching the nanodiamond, which may be a circular-shaped particle. The graphene oxide may have a nanosize in a thickness direction, while it is a plane spread by a length of a micrometer size, thus the graphene oxide may have a surface reaction with several nanodiamonds. In other words, the several nanodiamonds may approach into a surface reaction with the graphene oxide and may cover a surface of the graphene oxide. When the nanodiamonds are bonded to a top surface and a bottom surface of the graphene oxide, an actual metal may not be directly bonded to the surface of the graphene oxide, and the nanodiamond may contact a surface of the metal. As a result, a metal corrosion problem by the graphene oxide may be solved. Moreover, the nanodiamond with high thermal conductivity may be attached or bonded on the graphene oxide, thus a decrease of the thermal conductivity may not occur, and aggregation between the graphene oxides may decrease due to the nanodiamond bonded on the surface of the graphene oxide.

[0073] Although the graphene oxide may be highly dispersed in a polar solvent, contact between graphenes may be applied to produce steric hindrance due to the nanodiamond, thereby increasing dispersion stability for a long period.

[0074] A thickness of the graphene oxide may be about 1 to 2 nm, and a diameter of the graphene oxide may be about 1 to 3 μm. According to the thickness and diameter, sufficient space in which the nanodiamonds may be bonded is provided.

[0075] An amount of about 50 to 150 parts by weight of the nanodiamond based on 100 parts by weight of the graphene oxide may be chemically bonded to the graphene oxide. In other words, a weight ratio between the nanodiamond and the graphene oxide to form suitable bonding may be about 0.5-1.5:1 by weight. When the bonded amount of the nanodiamond is less than the predetermined amount, for example, less than about 50 parts by weight based on 100 parts by weight of the graphene oxide, the metal corrosion stability may deteriorate. In contrast, when the bonded amount of the nanodiamond is greater than the predetermined amount, for example, greater than about 150 parts by weight based on 100 parts by weight of the graphene oxide, the dispersion stability may deteriorate.

[0076] FIG. 2 illustrates a flowchart of a manufacturing method of a graphene oxide-nanodiamond complex according to an exemplary embodiment of the present invention, however, and the present invention is not limited thereto. Thus, a manufacturing method of the graphene oxide-nanodiamond complex may be variously modified.

[0077] As shown in FIG. 2, the manufacturing method of the graphene oxide-nanodiamond according to the exemplary embodiment of the present invention may include: preparing a nanodiamond at step S10; attaching a functional group on a surface of the nanodiamond by heat-treating the nanodiamond at step S20; dispersing the nanodiamond comprising the functional group in a first solvent at step S30 thereby forming a nanodiamond dispersion; dispersing a graphene oxide in a second solvent thereby forming a graphene oxide dispersion at step S40; mixing the graphite oxide solution with the nanodiamond dispersion; and forming a bond reaction at step S50.

[0078] Respective steps will be described in detail.

[0079] First, the nanodiamond may be prepared at step S10. Since the nanodiamond has been described above, a duplicated description thereof will be omitted.

[0080] Next, the functional group is introduced on the surface by heat-treating the nanodiamond at step S20. For a selective chemical reaction, at least one functional group among surface reaction groups present in the nanodiamond may be modified to be predominant. When the heat treatment is performed by one method described above, some unstable functional groups on the surface of the nanodiamond may be oxidized and changed to a carboxyl (—COOH) group. For example, the heat treatment may be performed for about 1 to 3 hours at a temperature of about 400° C. to 500° C. in the air.

[0081] When the heat treatment temperature is less than the predetermined range, for example, less than about 400° C., the functional group may not be sufficiently introduced, and when the heat treatment temperature is greater than the predetermined range, for example, greater than about 500° C., the nanodiamond may be carbonized. When the reaction time is less than the predetermined range, for example, less than about 1 hour, a reaction may not be sufficiently performed, and when the reaction time is greater than the predetermined range, for example, greater than about 3 hour, the nanodiamond may be carbonized.

[0082] The nanodiamond treated by heat and containing the predominant functional group may be dispersed in the first solvent at step S30. In this case, a catalyst may be added to the nanodiamond dispersion for promoting a bond formation reaction with the graphene oxide. For example, the catalyst may be one or more selected from the group consisting of N,N′-dicyclohexylcarbodiimide (DCC) and 4-(dimethyl amino)pyridine (DMAP).

[0083] For example, when the DCC is used as catalyst, the —COOH functional group formed on the surface of the nanodiamond may be activated according to Reaction Formula 1, and may react with the graphene oxide. Accordingly, the nanodiamond and the graphene oxide may form chemically bonding through the —CO—O— group.

##STR00001##

[0084] The solvent is not limited as long as it properly disperses the nanodiamond, and it may be one or more selected from the group consisting of an amide-based solvent, an ether-based solvent, and a halogenated solvent. Preferably, the amide solvent may include dimethylformamide (DMF), dimethylacetamide (DMAc), and N-methyl-2-pyrrolidone (NMP). The ether-based solvent suitably may include tetrahydrofuran (THF) and dioxane. The halogenated solvent suitably may be chloroform or methylene chloride.

[0085] The graphene oxide dispersion in which the graphene oxide is dispersed in the second solvent is manufactured at step S40. A description with respect to the graphene oxide is the same as the above-mentioned description, so a repeated description thereof will be omitted. A hydroxyl group or an alkyl group may be attached on the surface of the graphene oxide at step S40.

[0086] Next, the graphene oxide dispersion may be mixed with the nanodiamond dispersion and the graphene oxide and the nanodiamond may be bonded at step S50.

[0087] Preferably, an amount of about 50 to 150 parts by weight of the nanodiamonds based on 100 parts by weight of the graphene oxide may be bonded, by a chemical bonding such as covalent bond, with the graphene oxide. When the bonded amount of the nanodiamond is less than the predetermined amount, for example, less than about 50 parts by weight based on 100 parts by weight of the graphene oxide, the metal corrosion stability may deteriorate. In contrast, when the bonded amount of the nanodiamond is greater than the predetermined amount, for example, greater than about 150 parts by weight based on 100 parts by weight of the graphene oxide, the dispersion stability may deteriorate.

[0088] The bond may be formed by an esterification reaction forming ester bond according to Reaction Formula 1. Other reactions may occur between functional groups in the graphene oxide and the nanodiamond.

[0089] In addition, according to the exemplary embodiment of the present invention, the nanofluid may include the above described compositing comprising the graphene oxide and the nanodiamond and the polar fluid.

[0090] According to the nanofluid including the graphene oxide-nanodiamond complex, since the corrosion stability to the metal through which the fluid flows may be achieved, the aggregation among the nanoparticles may be prevented, and two materials having high thermal conductivity are bonded, the characteristic deterioration problem may be solved.

[0091] The polar fluid suitably may be selected from the group consisting of water, ethylene glycol, propylene glycol, and a combination thereof.

[0092] The nanofluid may be manufactured by mixing and dispersing the nanodiamond and the polar fluid.

Example

[0093] Hereinafter, examples of the present invention and comparative examples are described. These examples, however, should not in any sense be interpreted as limiting the scope of the present invention.

Exemplary Embodiment: Preparation of the Graphene Oxide-Nanodiamond Complex

[0094] 0.1 g of the nanodiamond (Manufacturer: HeYuan ZhongLian Nanotech Co. LTD) was prepared by pulverizing with jet mill until obtaining an average diameter of about 20 nm. The nanodiamond powder was heat-treated for about 1 h at 500° C. in the air. FIG. 3 and FIG. 4 illustrate the infrared spectroscopic analysis result of the nanodiamond before and after the heat treatment, respectively. As shown in FIG. 4, a peak was observed around about 1764 cm.sup.−1, and it can be confirmed that a C═O functional group of COOH was formed.

[0095] The heat-treated nanodiamond was introduced into 100 ml of tetrahydrofuran (THF) and dispersed by ultrasonic waves for about 2 h, 5 g of N,N′-dicyclohexylcarbodiimide (DCC) was introduced into 50 ml of a tetrahydrofuran (THF) solution, then the DCC solution was introduced into and mixed with the nanodiamond dispersion solution.

[0096] 0.1 g of the graphene oxide (thickness of 1 nm and diameter of 2 μm) was introduced into the THF solution and dispersed by ultrasonic waves for about 2 h, the nanodiamond was added to the DCC complex solution, and then the esterification bond reaction was performed for about 12 h.

[0097] After the reaction, a resulting sediment was filtered, washed, and dried to obtain the graphene oxide-nanodiamond complex.

[0098] FIG. 5 illustrates infrared spectroscopic analysis results of the prepared graphene oxide-nanodiamond complex. As shown in FIG. 5, it can be confirmed that the C═O peak was weakened and the chemical bond between the graphene oxide and the nanodiamond was formed.

[0099] FIG. 6 illustrates a scanning electron microscope (SEM) photograph of the prepared graphene oxide-nanodiamond complex. As shown in FIG. 6, it can be confirmed that the nanodiamond particles were bonded on the planar graphene.

Experimental Example: Preparation and Evaluation of the Nanofluid

[0100] 5 parts by weight of the graphene oxide-nanodiamond complex prepared according to the exemplary embodiment were added to 95 parts by weight of a 1:1 complex solvent of water and ethylene glycol, and were dispersed by ultrasonic waves to prepare the nanofluid.

[0101] In order to test the metal corrosion of the nanofluid, aluminum, cast iron, steel, brass, solder, and copper as samples were prepared, and were dipped into the nanofluid. FIG. 7 illustrates a photograph of the metal samples after being taken out.

[0102] Table 1 represents the corrosion states of the metal samples observed by the naked eye.

[0103] FIG. 8 illustrates a photograph after the prepared nanofluid is left to stand. As shown in FIG. 8, it can be seen that the dispersion was excellent even though the prepared nanofluid was left to stand for a long period of time.

Comparative Example

[0104] The nanofluid was prepared by adding the graphene oxide to 95 parts by weight of a 1:1 complex solvent of water and ethylene glycol and dispersing them with ultrasonic waves.

[0105] The same corrosion test as in the experimental example described above was performed, and a photograph of the metal samples which were taken out was illustrated in FIG. 9.

[0106] Table 1 represents the corrosion states of the metal samples observed with the naked eye.

TABLE-US-00001 TABLE 1 Cast Aluminum iron Steel Brass Solder Copper Experimental No No No No No No Example corrosion cor- cor- cor- cor- cor- rosion rosion rosion rosion rosion Comparative Severe Severe Severe Severe Severe Severe Example corrosion cor- cor- cor- cor- cor- rosion rosion rosion rosion rosion

[0107] As represented in Table 1, it can be seen that the nanofluid including the graphene oxide-nanodiamond complex according to the exemplary embodiment of the present invention had excellence corrosion stability.

[0108] While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Therefore, the embodiments described above are only examples and should not be construed as being limitative in any respects.