Method for preparing composites on basis of graphene bonding

Abstract

The invention utilizes swelling and fusion effects of graphene oxide in a solvent to implement cross-linked bonding of a graphene material itself and materials such as polymers, metal, paper, glass, carbon materials, and ceramics. The present invention not only overcomes the shortcoming in traditional adhesives of residual formaldehyde, but also has short drying time, high bonding strength and high corrosion resistance. The present invention is widely applied in the fields of aviation, aerospace, automobiles, machinery, construction, chemical, light industry, electronics, electrical appliances, and daily life, etc.

Claims

1. A method for preparing a highly thermally conductive thick graphene film, wherein the thickness is greater than 50 μm, the porosity is 5-40%, the in-plane thermal conductivity is 1000-2000 W/mK; the pleat density on the graphene sheet is controlled to 50-500 mm/mm2, and the graphene sheet has few defects and has an I.sub.D/I.sub.G ratio of <0.02; there is no delamination in the graphene thick film, and the distance between any two adjacent graphene sheets is less than 20 nm; and the preparation method comprises the following steps: (1) formulating graphene oxide having an average size greater than 50 μm into an aqueous graphene oxide solution having a concentration of 1 to 20 mg/mL, and naturally drying after a film is formed from the solution, to obtain a graphene oxide film; (2) laminating a plurality of graphene oxide films specifically by uniformly spraying a liquid on the surface of the graphene oxide films to swell the surface, and then bonding the plurality of graphene oxide films together in the thickness direction; (3) drying the bonded graphene oxide composite film in an oven at a temperature of not higher than 40° C.; (4) transferring the dried graphene oxide composite film to a hot-pressing chamber of a hot press, heating to 200° C. at a ramping rate of 0.1 to PC/min and then hot pressing by repeating the following hot-pressing process 8-10 times: maintaining the pressure at 20 MPa for 1 hr, gradually releasing the pressure to 0 MPa, and evacuating the hot-pressing chamber for 5 min to a vacuum level of −100-10 KPa; then heating to 300° C. for 0.5 hr at a ramping rate of 0.1-5° C./min, and then hot pressing by repeating the following hot pressing process 4-6 times: maintaining the pressure at 60 MPa for 1 hr, gradually releasing the pressure to 0 MPa, and evacuating the hot-pressing chamber for 5 min to a vacuum level of −100-10 KPa; and naturally cooling after hot pressing; and (5) heating the graphene oxide film that is hot pressed in Step 4 to a temperature of 1800-3000° C. at a ramping rate of 1-20° C./min under an inert gas atmosphere and further hot pressing, wherein the temperature and pressure are held for 0.5-8 hrs, and the pressure is 10 MPa; and pressing at a reduced temperature, to obtain a highly thermally conductive thick graphene film.

2. The method for preparing a highly thermally conductive thick graphene film according to claim 1, wherein the thickness of the graphene oxide film prepared in Step 1 is 1 to 30 μm.

3. The method for preparing a highly thermally conductive thick graphene film according to claim 1, wherein the film forming method in Step 1 is selected from suction filtration, blade coating, spin coating, spray coating, and dip coating.

4. The method for preparing a highly thermally conductive thick graphene film according to claim 1, wherein the carbon/oxygen ratio in the graphene oxide film prepared in Step 1 is ranged from 1.8:1 to 2.1:1.

5. The method for preparing a highly thermally conductive thick graphene film according to claim 1, wherein the liquid for spraying in Step 2 is deionized water, a graphene oxide aqueous solution having a concentration of 1 to 10 mg/mL, or other solutions containing deionized water.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of a non-woven fabric of boron nitride fibers crosslinked with the graphene of the present invention.

(2) FIG. 2 is a schematic diagram of a non-twisted yarn of boron nitride fibers crosslinked with the graphene of the present invention.

(3) FIGS. 3a and 3b are SEM images of an individual carbon fiber before and after coating, respectively, and FIG. 3c is a cross-sectional view of two crosslinked carbon fibers.

(4) FIG. 4 is a graph showing the bonding performance of various concentrations of adhesives (graphene oxide).

(5) FIG. 5 is a graph showing the bonding performance of various concentrations of adhesives (graphene oxide after reduction).

(6) FIG. 6 is a schematic diagram of a continuous coating apparatus.

(7) FIG. 7 is an SEM image at the cross section of a thick graphene film bonded with deionized water.

(8) FIG. 8 is an SEM image at the cross section of a thick graphene film bonded with an aqueous graphene oxide solution.

DESCRIPTION OF THE EMBODIMENTS

(9) The present invention will be specifically described by the following examples, which are only used to further illustrate the present invention, and are not to be construed as limiting the scope of the present invention. Some non-essential changes and adjustments made by those skilled in the art according to the disclosure the present invention are contemplated in the scope of protection of the present invention.

(10) Unless otherwise specifically indicated, the percentages in the following examples are quantitative percentages. For example, “single-layer graphene oxide accounts for 81.5% of the total amount of graphene oxide” means that out of 1000 sheets of graphene oxide, the number of single-layer graphene oxide is 815 sheets; “the amount of graphene oxide sheets with a size of less than 5 μm is 7±3% sheets” means that the number of graphene oxide sheets with a size of less than 5 μm is 7±3 out of 100 sheets of graphene oxide. In addition, C/O is a commonly used technical term in the art, and represents the ratio of the number of atoms of C and O.

Example 1-1

(11) In this example, the bonding properties of graphene oxide adhesives at various concentrations are studied under the conditions that follow.

(12) In the graphene oxide solution used, the amount of graphene oxide sheets with a size of less than 5 μm is 7±3%, the amount of graphene oxide sheets with a size of greater than 30 μm is 65±4%, and the rest has a size between 5-30 μm; and the overall C/O ratio is 2.5:1, and single-layer graphene oxide accounts for 81.5% of the total amount of graphene oxide.

(13) Aqueous graphene oxide solutions having a concentration of 2-20 mg/ml are formulated, and two glass slides are bonded therewith through a method comprising hydrophilically treating the glass slides, then coating the graphene oxide adhesive evenly between the two slides, and drying. As a result, the two slides are bonded by graphene oxide.

(14) The bonding effect at various concentrations is shown in FIG. 4. It can be seen from the figure that a good bonding effect is exhibited when the concentration of graphene oxide is more than 4 mg/ml.

Example 1-2

(15) In this example, the bonding properties of graphene oxide adhesives with various C/O ratios (1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 5:1) are studied under the conditions that follow.

(16) In the graphene oxide used, the amount of graphene oxide sheets with a size of less than 5 μm is 5±3%, the amount of graphene oxide sheets with a size of greater than 30 μm is 60±5%, and the rest has a size between 5-30 μm; and single-layer graphene oxide accounts for 95.8% of the total amount of graphene oxide. An aqueous graphene oxide solution having a concentration of 8 mg/ml is formulated, and two glass slides are bonded therewith through a method comprising hydrophilically treating the glass slides, then coating the graphene oxide adhesive evenly between the two slides, and drying. As a result, the two slides are bonded by graphene oxide.

(17) By testing the bonding performance of 6 adhesive samples, it is found that when C/O is less than or equal to 3:1, a good bonding effect is exhibited, and the bonding effect of two adhesive samples with a C/O ratio of 2:4 and 5:1 respectively is poor.

Example 1-3

(18) In this example, the bonding properties of graphene oxide adhesives with various size distributions are studied under the conditions that follow.

(19) The graphene oxide used has a size distribution as shown in Table 1, the overall C/O ratio is 2.5:1, and the content of single-layer graphene oxide is 91.6%. An aqueous graphene oxide solution having a concentration of 4 mg/ml is formulated, and two glass slides are bonded therewith through a method comprising hydrophilically treating the glass slides, then coating the graphene oxide adhesive evenly between the two slides, and drying. As a result, the two slides are bonded by graphene oxide.

(20) The bonding effects of graphene oxide adhesives with various size distributions are shown in Table 1. It can be seen from the table that the amount of graphene oxide sheets with a size of less than 5 μm should not be more than 10%, and the amount of graphene oxide sheets with a size of greater than 30 μm should not be less than 60%.

(21) TABLE-US-00001 TABLE 1 Size of GO Less than Greater than Bonding 5 μm 30 μm 5-30 μm effect Content % 20 50 30 Fall off 20 60 20 0.01 MPa 20 70 10 0.01 MPa 5 60 35 0.06 MPa 10 60 30 0.05 MPa 10 70 20 0.05 MPa 5 50 45 0.03 MPa 5 20 75 Fall off

Example 1-4

(22) (1) Graphene oxide with a C/O ratio of 3:1 and a proportion of single-layer graphene oxide of 81.4% is used, in which the amount of graphene oxide sheets with a size of less than 5 μm is 6%, the amount of graphene oxide sheets with a size of greater than 30 μm is 71%, and the rest has a size between 5-30 μm. A graphene oxide dispersion having a concentration of 4 mg/ml is formulated, where the dispersing phase is water, and this dispersion is used as a graphene adhesive.

(23) (2) The graphene adhesive is evenly coated on the surface of the polyethylene terephthalate (PET) material, and then dried, to effect the bonding. The bonding strength is tested to reach 0.11 MPa.

Example 1-5

(24) (1) Graphene oxide with a C/O ratio of 2.3:1 is used, in which the amount of graphene oxide sheets with a size of less than 5 μm is 10%, the amount of graphene oxide sheets with a size of greater than 30 μm is 87%, and the rest has a size between 5-30 μm. A graphene oxide dispersion having a concentration of 16 mg/ml is formulated, where the dispersing phase is water, and this dispersion is used as a graphene adhesive.

(25) (2) The graphene adhesive is evenly coated on the surface of the polyimide (PI) material, and then dried, to effect the bonding. The bonding strength is tested to reach 0.36 MPa.

Example 1-6

(26) (1) Graphene oxide with a C/O ratio of 0.5:1 and a proportion of single-layer graphene oxide of 96.8% is used, in which the amount of graphene oxide sheets with a size of less than 5 μm is 3%, the amount of graphene oxide sheets with a size of greater than 30 μm is 94%, and the rest has a size between 5-30 μm. A graphene oxide dispersion having a concentration of 18 mg/ml is formulated, where the dispersing phase is DMF, and this dispersion is used as a graphene adhesive.

(27) (2) The graphene adhesive is evenly coated on the surface of the glass material, and then dried to effect the bonding. The bonding strength is tested to reach 0.45 MPa.

Example 1-7

(28) (1) Graphene oxide with a C/O ratio of 1.7:1 and a proportion of single-layer graphene oxide of 88.9% is used, in which the size is controlled to the range of 50-80 μm. A graphene oxide dispersion having a concentration of 18 mg/ml is formulated, where the dispersing phase is water, and this dispersion is used as a graphene adhesive.

(29) (2) The graphene adhesive is evenly coated on the surface of the paper material, and then dried to effect the bonding. The bonding strength is tested to reach 0.62 MPa.

Example 1-8

(30) (1) Graphene oxide with a C/O ratio of 3:1 and a proportion of single-layer graphene oxide of 97.5% is used, in which the amount of graphene oxide sheets with a size of less than 5 μm is 4%, the amount of graphene oxide sheets with a size of greater than 30 μm is 91%, and the rest has a size between 5-30 μm. A graphene oxide dispersion having a concentration of 18 mg/ml is formulated, where the dispersing phase is water, and this dispersion is used as a graphene adhesive.

(31) (2) The graphene adhesive is evenly coated on the surface of the ceramic material, and then dried to effect the bonding. The bonding strength is tested to reach 0.22 MPa.

Example 2-1

(32) In this example, the effect of graphene oxide solutions at various concentrations on the final bonding property of graphene is studied specifically as follows.

(33) In the graphene oxide solution used, the amount of graphene oxide sheets with a size of less than 5 μm is 8±1%, the amount of graphene oxide sheets with a size of greater than 30 μm is 70±3%, and the rest has a size between 5-30 μm, and the overall C/O ratio is 2:1, and single-layer graphene oxide accounts for 98.8% of the total amount of graphene oxide.

(34) Aqueous graphene oxide solutions having a concentration of 2-20 mg/ml are formulated, and two glass slides are bonded therewith through a method comprising hydrophilically treating the glass slides, then coating the graphene oxide adhesive evenly between the two slides, drying, and chemically reducing with hydrazine hydrate vapor at 95° C., where the graphene has a C/O ratio of about 6:1 after reduction. As a result, the two slides are bonded by graphene oxide.

(35) The bonding effect at various concentrations is shown in FIG. 5. It can be seen from the figure that a good bonding effect is exhibited when the concentration of graphene oxide is more than 4 mg/ml.

Example 2-2

(36) In this example, the effect of graphene oxide with various size distributions on the final bonding property of graphene is studied specifically as follows.

(37) The graphene oxide used has a size distribution as shown in Table 2, the overall C/O ratio is 2:1, and the content of single-layer graphene oxide is 95.8%. An aqueous graphene oxide solution having a concentration of 4 mg/ml is formulated, and two glass slides are bonded therewith through a method comprising hydrophilically treating the glass slides, then coating the graphene oxide adhesive evenly between the two slides, drying, and chemically reducing with hydroiodic acid vapor at 90° C., where the graphene has a C/O ratio of about 5:1 after reduction. As a result, the two slides are bonded by graphene oxide.

(38) The bonding effects of graphene oxide adhesives with various size distributions are shown in Table 2. It can be seen from the table that the amount of graphene oxide sheets with a size of less than 5 μm should not be more than 10%, and the amount of graphene oxide sheets with a size of greater than 30 μm should not be less than 65%.

(39) TABLE-US-00002 TABLE 2 Size of GO Less than Greater than Bonding 5 μm 30 μm 5-30 μm effect Content % 15 45 40 Fall off 20 60 20 Fall off 20 70 10 0.01 MPa 5 70 25 0.02 MPa 10 65 25 0.02 MPa 10 80 10 0.02 MPa 5 60 35 0.01 MPa 5 20 75 Fall off

Example 2-3

(40) In this example, the effect of graphene oxide with various degrees of reduction (various C/O ratio) on the final bonding property is studied specifically as follows.

(41) The size of graphene oxide used is 30-80 μm, and the C/O ratio varies in the range of 2:1-3:1. The single-layer graphene oxide accounts for 84.1% of the total graphene oxide. An aqueous graphene oxide solution having a concentration of 8 mg/ml is formulated, and two ITO sheets are bonded therewith through a method comprising hydrophilically treating the ITO sheet, then coating the graphene oxide adhesive evenly between the two ITO sheets, drying, and thermally reducing under vacuum by slowly heating up to 300° C. at a ramping rate of 1° C./min, or chemically reducing with hydrazine hydrate vapor. Through the selection of C/O ratio in graphene oxide and control of the reduction method, the C/O ratio in the reduced graphene is 3.5:1, 4:1, 5:1, and 6:1.

(42) On the one hand, the bonding performance test is performed on 4 bonded samples, and it is found that the bonding effect decreases with the increase of the C/O ratio (the increase of the reduction degree). However, due to the advantages such as size distribution of and the proportion of single-layer graphene in the graphene sheet, a good bonding effect is always maintained. On the other hand, the electrical conductivity of the two bonded ITO is tested. The test result shows that the conductivity of the adhesive layer is significantly improved with increasing C/O ratio, and when the C/O ratio is 4:1, the conductivity of the ITO itself is achieved.

(43) It can be known from the above example that the carbon/oxygen ratio, size distribution and concentration of graphene oxide precursor can be adjusted by those skilled in the art according to the practical requirements for bonding effect and electrical conductivity, so as to achieve perfect bonding using the bonding method of the present invention. For example, if a high conductivity is required, the reduced graphene needs to have a high carbon/oxygen ratio. At this time, the bonding can be achieved by increasing the content of large-sized graphene sheets or increasing the concentration of graphene oxide precursor.

Example 2-4

(44) (1) Graphene oxide with a proportion of single-layer graphene oxide of 81.4% is used, in which the amount of graphene oxide sheets with a size of less than 5 μm is 6%, the amount of graphene oxide sheets with a size of greater than 30 μm is 87%, and the rest has a size between 5-30 μm. A graphene oxide dispersion having a concentration of 4 mg/ml is formulated, where the dispersing phase is water, and this dispersion is used as a graphene adhesive.

(45) (2) The graphene adhesive is evenly coated on the surface of the polyaniline material, and then dried to effect the bonding. The bonding strength is tested to reach 0.11 MPa.

(46) (3) After reduction with a hydroiodic acid solution at 90° C. for 30 min, the C/O ratio is tested to be 4:1. The bonding strength at the bonding site is tested to be 0.04 MPa, and excellent electrical conductivity and resistance to acids, alkali and salts are exhibited.

Example 2-5

(47) (1) Graphene oxide with a proportion of single-layer graphene oxide of 96.3% is used, in which the amount of graphene oxide sheets with a size of less than 5 μm is 3%, the amount of graphene oxide sheets with a size of greater than 30 μm is 91%, and the rest has a size between 5-30 μm. A graphene oxide dispersion having a concentration of 16 mg/ml is formulated, where the dispersing phase is water, and this dispersion is used as a graphene adhesive.

(48) (2) The graphene adhesive is evenly coated on the surface of an iron sheet, and then dried to effect the bonding. The bonding strength is tested to reach 0.36 MPa.

(49) (3) After reduction with a hydrazine hydrate solution at 70° C. for 20 min, the C/O ratio is tested to be 4:1. The bonding strength at the bonding site is tested to be 0.04 MPa, and the electrical conductivity and resistance to acids, alkali and salts are exhibited.

Example 2-6

(50) (1) Graphene oxide with a proportion of single-layer graphene oxide of 97.2% is used, in which the size is controlled to the range of 50-80 μm. A graphene oxide dispersion having a concentration of 12 mg/ml is formulated, where the dispersing phase is DMF, and this dispersion is used as a graphene adhesive.

(51) (2) The graphene adhesive is evenly coated on the surface of the electrically conductive glass material, and then dried, to effect the bonding. The bonding strength is tested to reach 0.11 MPa.

(52) (3) After 20 min of thermal reduction by heating to 200° C. at a ramping rate of 1° C./min, the C/O ratio is tested to be 4:1. The bonding strength at the bonding site is tested to be 0.03 MPa, and the electrical conductivity and resistance to acids, alkali and salts are exhibited.

Example 2-7

(53) (1) Graphene oxide with a proportion of single-layer graphene oxide of 95.4% is used, in which the size is controlled to the range of 50-80 μm. A graphene oxide dispersion having a concentration of 18 mg/ml is formulated, where the dispersing phase is water, and this dispersion is used as a graphene adhesive.

(54) (2) The graphene adhesive is evenly coated on the surface of the electrically conductive ceramic material, and then dried. The bonding strength is tested to reach 0.22 MPa.

(55) (3) After reduction with a hydroiodic acid solution at 80° C. for 60 min, the C/O ratio is tested to be 5:1. The bonding strength at the bonding site is tested to be 0.02 MPa, and the electrical conductivity and resistance to acids, alkali and salts are exhibited.

Example 3-1

(56) (1) Commercially available carbon fibers T800H are refluxed in acetone at 80° C. for 72 hrs to remove the sizing agent on the surface. Then the fibers are immersed in hydrogen peroxide at 110° C. for 2 hrs and then in concentrated nitric acid at 115° C. for 12 hrs, and finally washed with water and dried, to obtain carbon fibers with a surface modified by oxidation.

(57) (2) The surface of the carbon fibers is repeatedly coated with an aqueous graphene oxide dispersion (in which the graphene oxide sheet has a size of 40-50 μm, and a concentration as shown in Table 3) by the continuous coating equipment as shown in FIG. 6, and dried (at a temperature of 40° C.). The process is repeated 15 times, and carbon fibers coated with graphene oxide are obtained.

(58) (3) 30 carbon fibers coated with graphene oxide are immersed and swelled in a water tank, and they are drawn out from the water simultaneously. The fibers spontaneously approach each other to form a tow due to the surface tension of water. Subsequently, the tow is dried at room temperature, and the volatilization of water allows the graphene oxide sheets on the surface of the carbon fibers to be fused to each other, so that the carbon fibers are crosslinked with each other.

(59) (4) The carbon fiber tow crosslinked with graphene oxide is thermally reduced at 3000° C. to obtain a high-performance carbon fiber tow crosslinked with graphene.

(60) After the above steps, the tow of 30 carbon fibers is completely cross-linked by graphene, which is stacked on each other in the axial direction. The tow density is 1.7 g/cm.sup.3, the tensile strength is 4.9 GPa, the electrical conductivity is 0.8×10.sup.5 S/m, and the thermal conductivity is 43 W/mK.

(61) TABLE-US-00003 TABLE 3 Concentration Thickness of graphene of graphene Tensile Electrical Thermal oxide oxide layer Tow density strength conductivity conductivity (mg/ml) (μpm) (g/cm.sup.3) (GPa) (S/m) (W/mK) 0.1 0.5 0.9 1 1.2 × 10.sup.3 34 1 1 1.4 1.8   3 × 10.sup.4 39 7 3 1.7 4.9   8 × 10.sup.4 43 13 5.2 0.8 0.8 0.9 × 10.sup.3 32

(62) It can be seen from Table 3 that with the same number of coatings, when the concentration of graphene oxide is 7 mg/ml, the thickness of the graphene oxide coating on the surface of the carbon fibers is 3 μm, and is uniformly distributed along the fiber axis; the density, tensile strength, electrical conductivity, and thermal conductivity of the obtained carbon fiber tow are the highest; and the cross-linking effect is optimum. As the concentration of graphene oxide declines, the thickness of graphene oxide on the surface of the carbon fibers decreases; the density, tensile strength, electrical conductivity, and thermal conductivity of the obtained carbon fiber tow are lowered, and the cross-linking effect is deteriorated. As the concentration of graphene oxide rises, the thickness of graphene oxide on the surface of the carbon fibers increases, and is uniformly distributed along the fiber axis; the density, tensile strength, electrical conductivity, and thermal conductivity of the obtained carbon fiber tow are lowered, and the cross-linking effect is deteriorated.

Example 3-2

(63) Step (1) is the same as that in Example 3-1.

(64) (2) The surface of the carbon fibers are repeatedly coated with a 7 mg/ml aqueous graphene oxide dispersion (in which the graphene oxide sheet has a size of 40-50 μm) by continuous coating equipment, and dried (at a temperature of 25° C.). The process is repeated 20 times, and carbon fibers coated with graphene oxide are obtained. The thickness of the graphene oxide coating is about 3.8 μm, and is uniformly distributed along the fiber axis.

(65) (3) About 1000 carbon fibers (metric method) coated with graphene oxide are immersed and swelled in a water tank, and they are drawn out from the water simultaneously. The fibers spontaneously approach each other to form a tow due to the surface tension of water. Subsequently, the tow is dried at room temperature, and the volatilization of water allows the graphene oxide sheets on the surface of the carbon fibers to be fused to each other, so that the carbon fibers are crosslinked with each other.

(66) (4) The carbon fiber tow crosslinked with graphene oxide is reduced with hydroiodic acid to obtain a high-performance carbon fiber tow crosslinked with graphene.

(67) After the above steps, the tow of 1000 carbon fibers is completely cross-linked by graphene, which is stacked on each other in the axial direction. The tow density is 1.4 g/cm.sup.3, the tensile strength is 3.9 GPa, the electrical conductivity is 6.0×10.sup.4 S/m, and the thermal conductivity is 18 W/mK.

Example 3-3

(68) (1) Commercially available carbon fibers T800H are refluxed in acetone at 57° C. for 72 hrs to remove the sizing agent on the surface. Then the fibers are immersed in hydrogen peroxide at 108° C. for 2 hrs and then in concentrated nitric acid at 115° C. for 12 hrs, and finally washed with water and dried, to obtain carbon fibers with a surface modified by oxidation.

(69) (2) The surface of the carbon fibers are repeatedly coated with a 7 mg/ml aqueous graphene oxide dispersion (in which the graphene oxide sheet has a size of 40-50 μm) by continuous coating equipment, and dried (at a temperature of 40° C.). The process is repeated 15 times, and carbon fibers coated with graphene oxide are obtained. The thickness of the graphene oxide coating is about 3 μm, and is uniformly distributed along the fiber axis.

(70) (3) The carbon fibers coated with graphene oxide are woven into a woven fabric of 50×50 by plain weaving, immersed in a water tank for 3 min, taken out, and dried at 60° C. The volatilization of water allows the graphene oxide sheets on the surface of the carbon fibers at the contact nodes in the woven fabric to be fused to each other, so that the carbon fibers are crosslinked with each other, to obtain a carbon fiber woven fabric crosslinked with graphene oxide.

(71) (4) The carbon fiber woven fabric crosslinked with graphene oxide is thermally reduced at 3000° C. to obtain a high-performance carbon fiber woven fabric crosslinked with graphene.

(72) After the above steps, the carbon fibers at the contact nodes in the woven fabric are completely cross-linked by graphene, which is stacked on each other. The tensile strength is 4.1 GPa, the electrical conductivity is 0.4×10.sup.5 S/m, and the thermal conductivity is 36 W/mK.

Example 3-4

(73) (1) Commercially available carbon fibers T800H are refluxed in acetone at 100° C. for 6 hrs to remove the sizing agent on the surface. Then the fibers are immersed in hydrogen peroxide at 108° C. for 2 hrs and then in concentrated nitric acid at 115° C. for 12 hrs, and finally washed with water and dried, to obtain carbon fibers with a surface modified by oxidation.

(74) (2) The surface of the carbon fibers are repeatedly coated with a 7 mg/ml aqueous graphene oxide dispersion (in which the graphene oxide sheet has a size of 40-50 μm) by continuous coating equipment, and dried (at a temperature of 50° C.). The process is repeated 15 times, and carbon fibers coated with graphene oxide are obtained. The thickness of the graphene oxide coating is about 3 μm, and is uniformly distributed along the fiber axis.

(75) (3) The carbon fibers coated with graphene oxide are cut into short fibers, dispersed an aqueous solution, filtered under suction, and dried at 60° C. The volatilization of water allows the graphene oxide sheets on the surface of the carbon fibers at the contact nodes in the non-woven fabric to be fused to each other, so that the carbon fibers are crosslinked with each other, to obtain a carbon fiber non-woven fabric crosslinked with graphene oxide.

(76) (4) The carbon fiber woven fabric crosslinked with graphene oxide is thermally reduced at 3000° C. to obtain a high-performance carbon fiber non-woven fabric crosslinked with graphene.

(77) After the above steps, the carbon fibers at the contact nodes in the non-woven fabric are completely cross-linked by graphene, which is stacked on each other. The tensile strength is 600 MPa, the electrical conductivity is 0.6×10.sup.5 S/m, and the thermal conductivity is 42 W/mK.

(78) In addition, it is found through comparison of Examples 3-1 to 3-4 that in the carbon fiber tows obtained in Examples 3-1 and 3-2, the graphene sheets are more uniformly dispersed than in other examples, indicating that the carbon fibers modified by the oxidation modification scheme in Example 3-1 have better affinity with the active groups on the surface of graphene oxide.

Example 4-1

(79) (1) The surface of boron nitride fibers is repeatedly coated with an aqueous graphene oxide dispersion and dried. The process is repeated 15 times, to obtain boron nitride fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(80) (2) The boron nitride fibers coated with graphene oxide obtained in Step (1) are subjected to surface swelling in water, and then overlapped and dried to form a non-woven fabric, where the drying temperature is below 100° C.

(81) (3) The graphene oxide crosslinked boron nitride fibers obtained in Step (2) are placed in a closed vessel containing hydrazine hydrate and reduced at 80° C. for 12 hrs.

(82) Through the above steps, graphene is coated on the surface of the boron nitride fibers, and the surface of the boron nitride fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The boron nitride fibers are cross-linked by graphene coated on the surface, and the composite fibers are randomly overlapped to form a non-woven fabric structure. The areal density is 90.9 g/m.sup.2, the breaking strength is 1.98 GPa, the breaking strength retention rate is 86% after immersion for 24 hrs in water at 25° C., the electrical conductivity is 2.3×10.sup.4 S/m, and the thermal conductivity is 29 W/mK.

(83) TABLE-US-00004 TABLE 4 Breaking strength retention rate Thickness after immersion Concentration of graphene Areal density Breaking for 24 hrs in Electrical Thermal of graphene oxide layer of composite strength water at conductivitvity conductivity oxide (mg/ml) (μm) fiber (g/m.sup.2) (GPa) 25° C. (%) (S/m) (W/mK) 0 0 82.1 1.84 51 — — 0.1 0.5 83.7 1.93 78 1.1 × 10.sup.3 21 1 1 85 1.96 81 4.9 × 10.sup.3 23 7 3 90.9 1.98 86 2.3 × 10.sup.4 29 13 5.2 95.6 1.92 83 1.9 × 10.sup.3 24

(84) In addition, the graphene oxide concentration and coating thickness are the optimum results obtained after repeated testes. It can be seen from Table 4 that with the same number of coatings, when the concentration of graphene oxide is 7 mg/ml, the thickness of the graphene oxide coating on the surface of the boron carbide fibers is 3 μm; the breaking strength, electrical conductivity, and thermal conductivity of the obtained boron carbide fiber non-woven fabric are the highest; the hydrolytic stability is good, and the cross-linking effect is optimum. As the concentration of graphene oxide declines, the thickness of graphene oxide on the surface of the boron carbide fibers decreases; the breaking strength, electrical conductivity, and thermal conductivity of the obtained boron carbide fiber non-woven fabric are lowered; and the cross-linking effect and water resistance are deteriorated. As the concentration of graphene oxide rises, the thickness of graphene oxide on the surface of the boron carbide fibers increases, and distributed unevenly, and the degree of crosslinking decreases; the breaking strength, electrical conductivity, and thermal conductivity of the obtained boron carbide fiber non-woven fabric are lowered; and the hydrolytic stability is deteriorated.

Example 4-2

(85) (1) The surface of boron nitride fibers is repeatedly coated with a graphene oxide dispersion in N,N-dimethyl formamide and dried. The process is repeated 13 times, to obtain boron nitride fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(86) (2) The boron nitride fibers coated with graphene oxide obtained in Step (1) are subjected to surface swelling in a solvent, and then overlapped and dried to form a non-woven fabric, where the drying temperature is below 100° C.

(87) (3) The graphene oxide crosslinked boron nitride fibers obtained in Step (2) are placed in a closed vessel containing hydrazine hydrate and reduced at 80° C. for 12 hrs.

(88) Through the above steps, graphene is coated on the surface of the boron nitride fibers, and the surface of the boron nitride fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The boron nitride fibers are cross-linked by graphene coated on the surface, and the composite fibers are randomly overlapped to form a non-woven fabric structure. The areal density is 91.1 g/m.sup.2, the breaking strength is 1.94 GPa, the breaking strength retention rate is 84% after immersion for 24 hrs in water at 25° C., the electrical conductivity is 1.7×10.sup.4 S/m, and the thermal conductivity is 26 W/mK.

Example 4-3

(89) (1) The surface of boron nitride fibers is repeatedly coated with a graphene oxide dispersion in ethanol and dried. The process is repeated 16 times, to obtain boron nitride fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(90) (2) The boron nitride fibers coated with graphene oxide obtained in Step (1) are subjected to surface swelling in a solvent, and then overlapped and dried to form a non-woven fabric, where the drying temperature is below 100° C.

(91) (3) The graphene oxide crosslinked boron nitride fibers obtained in Step (2) are placed in a closed vessel containing hydroiodic acid and reduced at 90° C. for 18 hrs.

(92) Through the above steps, graphene is coated on the surface of the boron nitride fibers, and the surface of the boron nitride fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The boron nitride fibers are cross-linked by graphene coated on the surface, and the composite fibers are randomly overlapped to form a non-woven fabric structure. The areal density is 91.7 g/m.sup.2, the breaking strength is 1.99 GPa, the breaking strength retention rate is 88% after immersion for 24 hrs in water at 25° C., the electrical conductivity is 2.7×10.sup.4 S/m, and the thermal conductivity is 30 W/mK.

Example 4-4

(93) (1) The surface of boron nitride fibers that are arranged in parallel is repeatedly coated with a graphene oxide dispersion in ethylene glycol and dried. The process is repeated 12 times, to obtain boron nitride filament fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(94) (2) The boron nitride filament fibers coated with graphene oxide obtained in Step (1) are subjected to surface swelling in ethylene glycol, and then combined and dried to form a non-twisted yarn, where the drying temperature is below 100° C. to volatilize ethylene glycol.

(95) (3) The graphene oxide crosslinked boron nitride filament fibers obtained in Step (2) are placed in a closed vessel containing hydroiodic acid and reduced at 90° C. for 18 hrs.

(96) Through the above steps, graphene is coated on the surface of the boron nitride fibers, and the surface of the boron nitride fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The boron nitride fibers are cross-linked by graphene coated on the surface, and the composite fibers are arranged in parallel to form a non-twisted yarn structure. The breaking strength is 2.09 GPa, the breaking strength retention rate is 85% after immersion for 24 hrs in water at 25° C., the electrical conductivity is 2.4×10.sup.4 S/m, and the thermal conductivity is 26 W/mK.

Example 4-5

(97) (1) The surface of boron nitride fibers that are arranged in parallel is repeatedly coated with an aqueous graphene oxide dispersion and dried. The process is repeated 15 times, to obtain boron nitride fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(98) (2) The boron nitride fibers coated with graphene oxide obtained in Step (1) are subjected to surface swelling in ethylene glycol, and then combined and dried to form a non-twisted yarn, where the drying temperature is below 100° C. to volatilize ethylene glycol.

(99) (3) The graphene oxide crosslinked boron nitride filament fibers obtained in Step (2) are placed in a closed vessel containing hydroiodic acid and reduced at 90° C. for 18 hrs.

(100) Through the above steps, graphene is coated on the surface of the boron nitride fibers, and the surface of the boron nitride fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The boron nitride fibers are cross-linked by graphene coated on the surface, and the composite fibers are arranged in parallel to form a non-twisted yarn structure. The breaking strength is 2.14 GPa, the breaking strength retention rate is 85% after immersion for 24 hrs in water at 25° C., the electrical conductivity is 3.1×10.sup.4 S/m, and the thermal conductivity is 28 W/mK.

Example 5-1

(101) (1) Quartz fibers are soaked in toluene, heated to 300° C. for 10 min, and dried.

(102) (2) The surface of quartz fibers obtained in Step (1) is repeatedly coated with an aqueous graphene oxide dispersion and dried. The process is repeated 15 times, to obtain quartz fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(103) (3) The quartz fibers coated with graphene oxide obtained in Step (2) are subjected to surface swelling in water, and then overlapped and dried to form a non-woven fabric, where the drying temperature is below 100° C.

(104) (4) The graphene oxide crosslinked quartz fibers obtained in Step (3) are placed in a closed vessel containing hydrazine hydrate and reduced at 80° C. for 12 hrs.

(105) Through the above steps, graphene is coated on the surface of the quartz fibers, and the surface of the quartz fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The quartz fibers are cross-linked by graphene coated on the surface, and the composite fibers are randomly overlapped to form a non-woven fabric structure. The areal density is 87.1 g/m.sup.2, the breaking strength is 2.2 GPa, the strength retention rate is 89% after immersion for 12 hrs in alkali liquor at pH 12, the electrical conductivity is 4.9×104 S/m, and the thermal conductivity is 23 W/mK.

(106) TABLE-US-00005 TABLE 5 Strength Thickness retention rate Concentration of graphene Areal density Breaking after immersion Electrical Thermal of graphene oxide layer of composite strength in alkali liquor conductivitvity conductivity oxide (mg/ml) (μm) fiber (g/m.sup.2) (GPa) (%) (S/m) (W/mK) 0 0 80.7 1.72 35 — — 0.1 0.5 81.6 1.81 81 7.6 × 10.sup.2 11 1 1 82.6 1.94 84 2.4 × 10.sup.3 16 7 3 87.1 2.2 89 4.9 × 10.sup.4 23 13 5.2 91 1.84 82 2.2 × 10.sup.3 18

(107) In addition, the graphene oxide concentration and coating thickness are the optimum results obtained after repeated testes. It can be seen from Table 5 that with the same number of coatings, when the concentration of graphene oxide is 7 mg/ml, the thickness of the graphene oxide coating on the surface of the quartz fibers is 3 μm; the breaking strength, electrical conductivity, and thermal conductivity of the obtained quartz fiber non-woven fabric are the highest; and the cross-linking effect is optimum. As the concentration of graphene oxide declines, the thickness of graphene oxide on the surface of the quartz fibers decreases; the breaking strength, electrical conductivity, and thermal conductivity of the obtained quartz fiber non-woven fabric are lowered; and the cross-linking effect and alkali resistance are deteriorated. As the concentration of graphene oxide rises, the thickness of graphene oxide on the surface of the quartz fibers increases, and distributed unevenly, and the degree of crosslinking decreases; and the breaking strength, electrical conductivity, and thermal conductivity of the obtained quartz fiber non-woven fabric are lowered.

Example 5-2

(108) (1) Quartz fibers are soaked in toluene, heated to 300° C. for 10 min, and dried.

(109) (2) The surface of quartz fibers obtained in Step (1) is repeatedly coated with a graphene oxide dispersion in N,N-dimethylformamide and dried. The process is repeated 13 times, to obtain quartz fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(110) (3) The quartz fibers coated with graphene oxide obtained in Step (2) are subjected to surface swelling in water, and then overlapped and dried to form a non-woven fabric, where the drying temperature is below 100° C.

(111) (4) The graphene oxide crosslinked quartz fibers obtained in Step (3) are placed in a closed vessel containing hydrazine hydrate and reduced at 80° C. for 12 hrs.

(112) Through the above steps, graphene is coated on the surface of the quartz fibers, and the surface of the quartz fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The quartz fibers are cross-linked by graphene coated on the surface, and the composite fibers are randomly overlapped to form a non-woven fabric structure. The areal density is 88.3 g/m.sup.2, the breaking strength is 2.1 GPa, the strength retention rate is 87% after immersion for 12 hrs in alkali liquor at pH 12, the electrical conductivity is 5.1×10.sup.4 S/m, and the thermal conductivity is 25 W/mK.

Example 5-3

(113) (1) Quartz fibers are soaked in toluene, heated to 300° C. for 10 min, and dried.

(114) (2) The surface of quartz fibers obtained in Step (1) is repeatedly coated with a graphene oxide dispersion in ethanol and dried. The process is repeated 16 times, to obtain quartz fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(115) (3) The quartz fibers coated with graphene oxide obtained in Step (2) are subjected to surface swelling in water, and then overlapped and dried to form a non-woven fabric, where the drying temperature is below 100° C.

(116) (4) The graphene oxide crosslinked quartz fibers obtained in Step (3) are placed in a closed vessel containing hydroiodic acid and reduced at 90° C. for 18 hrs.

(117) Through the above steps, graphene is coated on the surface of the quartz fibers, and the surface of the quartz fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The quartz fibers are cross-linked by graphene coated on the surface, and the composite fibers are randomly overlapped to form a non-woven fabric structure. The areal density is 86.4 g/m.sup.2, the breaking strength is 2.3 GPa, the strength retention rate is 82% after immersion for 12 hrs in alkali liquor at pH 12, the electrical conductivity is 3.9×10.sup.4 S/m, and the thermal conductivity is 22 W/mK.

Example 5-4

(118) (1) Quartz fibers that are arranged in parallel are soaked in toluene, heated to 300° C. for 10 min, and dried.

(119) (2) The surface of quartz fibers obtained in Step (1) is repeatedly coated with a graphene oxide dispersion in ethylene glycol and dried. The process is repeated 12 times, to obtain quartz filament fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(120) (3) The quartz filament fibers coated with graphene oxide obtained in Step (2) are subjected to surface swelling in ethylene glycol, and then combined and dried to form a non-twisted yarn, where the drying temperature is below 100° C. to volatilize ethylene glycol.

(121) (4) The graphene oxide crosslinked quartz filament fibers obtained in Step (3) are placed in a closed vessel containing hydroiodic acid and reduced at 90° C. for 18 hrs.

(122) Through the above steps, graphene is coated on the surface of the quartz fibers, and the surface of the quartz fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The quartz fibers are cross-linked by graphene coated on the surface, and the composite fibers are arranged in parallel to form a non-twisted yarn structure. The breaking strength is 2.7 GPa, the strength retention rate is 84% after immersion for 12 hrs in alkali liquor at pH 12, the electrical conductivity is 6.8×10.sup.4 S/m, and the thermal conductivity is 29 W/mK.

Example 5-5

(123) (1) Quartz fibers that are arranged in parallel are soaked in toluene, heated to 300° C. for 10 min, and dried.

(124) (2) The surface of quartz fibers obtained in Step (1) is repeatedly coated with an aqueous graphene oxide dispersion and dried. The process is repeated 15 times, to obtain quartz fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(125) (3) The quartz fibers coated with graphene oxide obtained in Step (2) are subjected to surface swelling in ethylene glycol, and then combined and dried to form a non-twisted yarn, where the drying temperature is below 100° C. to volatilize ethylene glycol.

(126) (4) The graphene oxide crosslinked quartz filament fibers obtained in Step (3) are placed in a closed vessel containing hydroiodic acid and reduced at 90° C. for 18 hrs.

(127) Through the above steps, graphene is coated on the surface of the quartz fibers, and the surface of the quartz fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The quartz fibers are cross-linked by graphene coated on the surface, and the composite fibers are arranged in parallel to form a non-twisted yarn structure. The breaking strength is 2.8 GPa, the strength retention rate is 82% after immersion for 12 hrs in alkali liquor at pH 12, the electrical conductivity is 6.3×10.sup.4 S/m, and the thermal conductivity is 27 W/mK.

Example 6-1

(128) (1) The surface of silicon carbide fibers having a round cross section is repeatedly coated with an aqueous graphene oxide dispersion and dried. The process is repeated 15 times, to obtain silicon carbide fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(129) (2) The silicon carbide fibers coated with graphene oxide obtained in Step (1) are subjected to surface swelling in water, and then overlapped and dried to form a non-woven fabric, where the drying temperature is below 100° C.

(130) (3) The graphene oxide crosslinked silicon carbide fibers obtained in Step (2) are placed in a closed vessel containing hydrazine hydrate and reduced at 80° C. for 12 hrs.

(131) Through the above steps, graphene is coated on the surface of the silicon carbide fibers, and the surface of the silicon carbide fibers and the graphene sheet are connected by van der Waals force. The silicon carbide fibers are cross-linked by graphene coated on the surface, and the composite fibers are randomly overlapped to form a non-woven fabric structure. The areal density is 11 g/m.sup.2, the breaking strength is 2.91 GPa, the electrical conductivity is 2.8×10.sup.4 S/m, and the thermal conductivity is 22 W/mK.

(132) TABLE-US-00006 TABLE 6 Concentration Thickness Areal density of graphene of graphene of composite Breaking Electrical Thermal oxide oxide layer fiber strength conductivity conductivity (mg/ml) (μm) (g/m.sup.2) (GPa) (S/m) (W/mK) 0 0 108.3 2.81 — — 0.1 0.5 109.6 2.83 4.6 × 10.sup.2 16 1 1 111 2.87 1.1 × 10.sup.3 19 7 3 116.6 2.91 2.8 × 10.sup.4 13 5.2 124.3 2.81 3.9 × 10.sup.3 18

(133) In addition, the graphene oxide concentration and coating thickness are the optimum results obtained after repeated testes. It can be seen from Table 6 that with the same number of coatings, when the concentration of graphene oxide is 7 mg/ml, the thickness of the graphene oxide coating on the surface of the silicon carbide fibers is 3 μm; the breaking strength, electrical conductivity, and thermal conductivity of the obtained silicon carbide fiber non-woven fabric are the highest; and the cross-linking effect is optimum. As the concentration of graphene oxide declines, the thickness of graphene oxide on the surface of the silicon carbide fibers decreases; the breaking strength, electrical conductivity, and thermal conductivity of the obtained silicon carbide fiber non-woven fabric are lowered; and the cross-linking effect is deteriorated. As the concentration of graphene oxide rises, the thickness of graphene oxide on the surface of the silicon carbide fibers increases, and distributed unevenly, and the degree of crosslinking decreases; and the breaking strength, electrical conductivity, and thermal conductivity of the obtained silicon carbide fiber non-woven fabric are lowered.

Example 6-2

(134) (1) The surface of iron-containing silicon carbide fibers having a round cross section is repeatedly coated with a graphene oxide dispersion in N,N-dimethylformamide and dried. The process is repeated 13 times, to obtain silicon carbide fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(135) (2) The silicon carbide fibers coated with graphene oxide obtained in Step (1) are subjected to surface swelling in water, and then overlapped and dried to form a non-woven fabric, where the drying temperature is below 100° C.

(136) (3) The graphene oxide crosslinked silicon carbide fibers obtained in Step (2) are placed in a closed vessel containing hydrazine hydrate and reduced at 80° C. for 12 hrs.

(137) Through the above steps, graphene is coated on the surface of the silicon carbide fibers, and the surface of the silicon carbide fibers and the graphene sheet are connected by van der Waals force. The silicon carbide fibers are cross-linked by graphene coated on the surface, and the composite fibers are randomly overlapped to form a non-woven fabric structure. The areal density is 112.6 g/m.sup.2, the breaking strength is 2.89 GPa, the electrical conductivity is 2.5×10.sup.4 S/m, and the thermal conductivity is 23 W/mK.

Example 6-3

(138) (1) The surface of titanium-containing silicon carbide fibers having a trilobal cross section is repeatedly coated with a graphene oxide dispersion in ethanol and dried. The process is repeated 16 times, to obtain silicon carbide fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(139) (2) The silicon carbide fibers coated with graphene oxide obtained in Step (1) are subjected to surface swelling in water, and then overlapped and dried to form a non-woven fabric, where the drying temperature is below 100° C.

(140) (3) The graphene oxide crosslinked silicon carbide fibers obtained in Step (2) are placed in a closed vessel containing hydroiodic acid and reduced at 90° C. for 18 hrs.

(141) Through the above steps, graphene is coated on the surface of the silicon carbide fibers, and the surface of the silicon carbide fibers and the graphene sheet are connected by van der Waals force. The silicon carbide fibers are cross-linked by graphene coated on the surface, and the composite fibers are randomly overlapped to form a non-woven fabric structure. The areal density is 113.5 g/m.sup.2, the breaking strength is 2.93 GPa, the electrical conductivity is 3.5×10.sup.4 S/m, and the thermal conductivity is 24 W/mK.

Example 6-4

(142) (1) The surface of silicon carbide fibers that are arranged in parallel and have a round cross section is repeatedly coated with a graphene oxide dispersion in ethylene glycol and dried. The process is repeated 12 times, to obtain silicon carbide filament fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(143) (2) The silicon carbide filament fibers coated with graphene oxide obtained in Step (1) are subjected to surface swelling in ethylene glycol, and then combined and dried to form a non-twisted yarn, where the drying temperature is below 100° C. to volatilize ethylene glycol.

(144) (3) The graphene oxide crosslinked silicon carbide filament fibers obtained in Step (2) are placed in a closed vessel containing hydroiodic acid and reduced at 90° C. for 18 hrs.

(145) Through the above steps, graphene is coated on the surface of the silicon carbide fibers, and the surface of the silicon carbide fibers and the graphene sheet are connected by van der Waals force. The silicon carbide fibers are cross-linked by graphene coated on the surface, and the composite fibers are arranged in parallel to form a non-twisted yarn structure. The breaking strength is 2.92 GPa, the electrical conductivity is 5.7×10.sup.4 S/m, and the thermal conductivity is 27 W/mK.

Example 6-5

(146) (1) The surface of hollow aluminum-containing silicon carbide fibers that are arranged in parallel is repeatedly coated with an aqueous graphene oxide dispersion and dried. The process is repeated 15 times, to obtain silicon carbide fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(147) (2) The silicon carbide fibers coated with graphene oxide obtained in Step (1) are subjected to surface swelling in ethylene glycol, and then combined and dried to form a non-twisted yarn, where the drying temperature is below 100° C. to volatilize ethylene glycol.

(148) (3) The graphene oxide crosslinked silicon carbide filament fibers obtained in Step (2) are placed in a closed vessel containing hydroiodic acid and reduced at 90° C. for 18 hrs.

(149) Through the above steps, graphene is coated on the surface of the silicon carbide fibers, and the surface of the silicon carbide fibers and the graphene sheet are connected by van der Waals force. The silicon carbide fibers are cross-linked by graphene coated on the surface, and the composite fibers are arranged in parallel to form a non-twisted yarn structure. The breaking strength is 2.86 GPa, the electrical conductivity is 4.8×10.sup.4 S/m, and the thermal conductivity is 27 W/mK.

Example 7-1

(150) (1) Basalt fibers are heated in toluene at 250° C., ultrasonically washed for 10-30 min to remove the sizing agent and oil on the surface, and dried.

(151) (2) The surface of basalt fibers obtained in Step (1) is repeatedly coated with an aqueous graphene oxide dispersion and dried. The process is repeated 15 times, to obtain basalt fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(152) (3) The basalt fibers coated with graphene oxide obtained in Step (2) are subjected to surface swelling in water, and then overlapped and dried to form a non-woven fabric, where the drying temperature is below 100° C.

(153) (4) The graphene oxide crosslinked basalt fibers obtained in Step (3) are placed in a closed vessel containing hydrazine hydrate and reduced at 80° C. for 12 hrs.

(154) Through the above steps, graphene is coated on the surface of the basalt fibers, and the surface of the basalt fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The basalt fibers are cross-linked by graphene coated on the surface, and the composite fibers are randomly overlapped to form a non-woven fabric structure. The areal density is 86.1 g/m.sup.2, the breaking strength is 3.24 GPa, the strength retention rate is 89% after immersion for 6 hrs in alkali liquor at pH 12, the electrical conductivity is 1.6×10.sup.4 S/m, and the thermal conductivity is 29 W/mK.

(155) TABLE-US-00007 TABLE 7 Retention rate Thickness after immersion Concentration of graphene Areal density Breaking for 6 hrs in Electrical Thermal of graphene oxide layer of composite strength alkali liquor at conductivitvity conductivity oxide (mg/ml) (μm) fiber (g/m.sup.2) (GPa) pH 12 (%) (S/m) (W/mK) 0 0 81.3 3.12 52 — — 0.1 0.5 82.4 3.17 78 6.3 × 10.sup.2 19 1 1 83.6 3.21 83 1.1 × 10.sup.3 24 7 3 86.1 3.24 89 1.6 × 10.sup.4 29 13 5.2 89.3 3.16 91 7.3 × 10.sup.3 21

(156) In addition, the graphene oxide concentration and coating thickness are the optimum results obtained after repeated testes. It can be seen from Table 7 that with the same number of coatings, when the concentration of graphene oxide is 7 mg/ml, the thickness of the graphene oxide coating on the surface of the basalt fibers is 3 μm; the breaking strength, electrical conductivity, and thermal conductivity of the obtained basalt fiber non-woven fabric are the highest; and the cross-linking effect is optimum. As the concentration of graphene oxide declines, the thickness of graphene oxide on the surface of the basalt fibers decreases; the breaking strength, electrical conductivity, and thermal conductivity of the obtained basalt fiber non-woven fabric are lowered; and the cross-linking effect is deteriorated. As the concentration of graphene oxide rises, the thickness of graphene oxide on the surface of the basalt fibers increases, and distributed unevenly, and the degree of crosslinking decreases; and the breaking strength, electrical conductivity, and thermal conductivity of the obtained basalt fiber non-woven fabric are lowered.

Example 7-2

(157) (1) Basalt fibers are heated in toluene at 250° C., ultrasonically washed for 10-30 min to remove the sizing agent and oil on the surface, and dried.

(158) (2) The surface of basalt fibers obtained in Step (1) is repeatedly coated with a graphene oxide dispersion in N,N-dimethylformamide and dried. The process is repeated 13 times, to obtain basalt fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(159) (3) The basalt fibers coated with graphene oxide obtained in Step (2) are subjected to surface swelling in water, and then overlapped and dried to form a non-woven fabric, where the drying temperature is below 100° C.

(160) (4) The graphene oxide crosslinked basalt fibers obtained in Step (3) are placed in a closed vessel containing hydrazine hydrate and reduced at 80° C. for 12 hrs.

(161) Through the above steps, graphene is coated on the surface of the basalt fibers, and the surface of the basalt fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The basalt fibers are cross-linked by graphene coated on the surface, and the composite fibers are randomly overlapped to form a non-woven fabric structure. The areal density is 85.2 g/m.sup.2, the breaking strength is 3.21 GPa, the strength retention rate is 87% after immersion for 6 hrs in alkali liquor at pH 12, the electrical conductivity is 1.3×10.sup.4 S/m, and the thermal conductivity is 28 W/mK.

Example 7-3

(162) (1) Basalt fibers are heated in toluene at 250° C., ultrasonically washed for 10-30 min to remove the sizing agent and oil on the surface, and dried.

(163) (2) The surface of basalt fibers obtained in Step (1) is repeatedly coated with a graphene oxide dispersion in ethanol and dried. The process is repeated 16 times, to obtain basalt fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(164) (3) The basalt fibers coated with graphene oxide obtained in Step (2) are subjected to surface swelling in water, and then overlapped and dried to form a non-woven fabric, where the drying temperature is below 100° C.

(165) (4) The graphene oxide crosslinked basalt fibers obtained in Step (3) are placed in a closed vessel containing hydroiodic acid and reduced at 90° C. for 18 hrs.

(166) Through the above steps, graphene is coated on the surface of the basalt fibers, and the surface of the basalt fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The basalt fibers are cross-linked by graphene coated on the surface, and the composite fibers are randomly overlapped to form a non-woven fabric structure. The areal density is 84.6 g/m.sup.2, the breaking strength is 3.23 GPa, the strength retention rate is 85% after immersion for 6 hrs in alkali liquor at pH 12, the electrical conductivity is 2.1×10.sup.4 S/m, and the thermal conductivity is 27 W/mK.

Example 7-4

(167) (1) Basalt filament fibers that are arranged in parallel are heated in toluene at 250° C., ultrasonically washed for 20 min to remove the sizing agent and oil on the surface, and dried.

(168) (2) The surface of basalt fibers obtained in Step (1) is repeatedly coated with a graphene oxide dispersion in ethanol and dried. The process is repeated 12 times, to obtain basalt filament fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(169) (3) The basalt filament fibers coated with graphene oxide obtained in Step (2) are subjected to surface swelling in ethylene glycol, and then combined and dried to form a non-twisted yarn, where the drying temperature is below 100° C. to volatilize ethylene glycol.

(170) (4) The graphene oxide crosslinked basalt filament fibers obtained in Step (3) are placed in a closed vessel containing hydroiodic acid and reduced at 90° C. for 18 hrs.

(171) Through the above steps, graphene is coated on the surface of the basalt fibers, and the surface of the basalt fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The basalt fibers are cross-linked by graphene coated on the surface, and the composite fibers are arranged in parallel to form a non-twisted yarn structure. The breaking strength is 3.42 GPa, the strength retention rate is 85% after immersion for 6 hrs in alkali liquor at pH 12, the electrical conductivity is 3.9×10.sup.4 S/m, and the thermal conductivity is 31 W/mK.

Example 7-5

(172) (1) Basalt filament fibers that are arranged in parallel are heated in toluene at 250° C., ultrasonically washed for 20 min to remove the sizing agent and oil on the surface, and dried.

(173) (2) The surface of basalt fibers obtained in Step (1) is repeatedly coated with an aqueous graphene oxide dispersion and dried. The process is repeated 15 times, to obtain basalt fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(174) (3) The basalt fibers coated with graphene oxide obtained in Step (2) are subjected to surface swelling in ethylene glycol, and then combined and dried to form a non-twisted yarn, where the drying temperature is below 100° C. to volatilize ethylene glycol.

(175) (4) The graphene oxide crosslinked basalt filament fibers obtained in Step (3) are placed in a closed vessel containing hydroiodic acid and reduced at 90° C. for 18 hrs.

(176) Through the above steps, graphene is coated on the surface of the basalt fibers, and the surface of the basalt fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The basalt fibers are cross-linked by graphene coated on the surface, and the composite fibers are arranged in parallel to form a non-twisted yarn structure. The breaking strength is 3.45 GPa, the strength retention rate is 84% after immersion for 6 hrs in alkali liquor at pH 12, the electrical conductivity is 4.4×10.sup.4 S/m, and the thermal conductivity is 26 W/mK.

Example 8-1

(177) (1) The surface of alumina fibers is repeatedly coated with an aqueous graphene oxide dispersion and dried. The process is repeated 15 times, to obtain alumina fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(178) (2) The alumina fibers coated with graphene oxide obtained in Step (3) are subjected to surface swelling in water, and then overlapped and dried to form a non-woven fabric, where the drying temperature is below 100° C.

(179) (3) The graphene oxide crosslinked alumina fibers obtained in Step (2) are placed in a closed vessel containing hydrazine hydrate and reduced at 80° C. for 12 hrs.

(180) Through the above steps, graphene is coated on the surface of the alumina fibers, and the surface of the alumina fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The alumina fibers are cross-linked by graphene coated on the surface, and the composite fibers are randomly overlapped to form a non-woven fabric structure. The areal density is 96.5 g/m.sup.2, the breaking strength is 2.23 GPa, the electrical conductivity is 3.7×10.sup.4 S/m, and the thermal conductivity is 24 W/mK.

(181) TABLE-US-00008 TABLE 8 Concentration Thickness Areal density of graphene of graphene of composite Breaking Electrical Thermal oxide oxide layer fiber strength conductivity conductivity (mg/ml) (μm) (g/m.sup.2) (GPa) (S/m) (W/mK) 0 0 91.6 2.0 — — 0.1 0.5 92.3 2.12 8.2 × 10.sup.2 19 1 1 93.1 2.17 1.8 × 10.sup.3 21 7 3 96.5 2.23 3.7 × 10.sup.4 24 13 5.2 99.7 2.06 2.5 × 10.sup.3 19

(182) In addition, the graphene oxide concentration and coating thickness are the optimum results obtained after repeated testes. It can be seen from Table 8 that with the same number of coatings, when the concentration of graphene oxide is 7 mg/ml, the thickness of the graphene oxide coating on the surface of the alumina fibers is 3 μm; the breaking strength, electrical conductivity, and thermal conductivity of the obtained alumina fiber non-woven fabric are the highest; and the cross-linking effect is optimum. As the concentration of graphene oxide declines, the thickness of graphene oxide on the surface of the alumina fibers decreases; the breaking strength, electrical conductivity, and thermal conductivity of the obtained alumina fiber non-woven fabric are lowered; and the cross-linking effect and alkali resistance are deteriorated. As the concentration of graphene oxide rises, the thickness of graphene oxide on the surface of the alumina fibers increases, and distributed unevenly, and the degree of crosslinking decreases; and the breaking strength, electrical conductivity, and thermal conductivity of the obtained alumina fiber non-woven fabric are lowered.

Example 8-2

(183) (1) The surface of alumina fibers is repeatedly coated with a graphene oxide dispersion in N,N-dimethyl formamide and dried. The process is repeated 13 times, to obtain alumina fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(184) (2) The alumina fibers coated with graphene oxide obtained in Step (1) are subjected to surface swelling in water, and then overlapped and dried to form a non-woven fabric, where the drying temperature is below 100° C.

(185) (3) The graphene oxide crosslinked alumina fibers obtained in Step (2) are placed in a closed vessel containing hydrazine hydrate and reduced at 80° C. for 12 hrs.

(186) Through the above steps, graphene is coated on the surface of the alumina fibers, and the surface of the alumina fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The alumina fibers are cross-linked by graphene coated on the surface, and the composite fibers are randomly overlapped to form a non-woven fabric structure. The areal density is 95.6 g/m.sup.2, the breaking strength is 2.3 GPa, the electrical conductivity is 4.5×10.sup.4 S/m, and the thermal conductivity is 25 W/mK.

Example 8-3

(187) (1) The surface of alumina fibers is repeatedly coated with a graphene oxide dispersion in ethanol and dried. The process is repeated 16 times, to obtain alumina fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(188) (2) The alumina fibers coated with graphene oxide obtained in Step (3) are subjected to surface swelling in water, and then overlapped and dried to form a non-woven fabric, where the drying temperature is below 100° C.

(189) (3) The graphene oxide crosslinked alumina fibers obtained in Step (2) are placed in a closed vessel containing hydroiodic acid and reduced at 90° C. for 18 hrs.

(190) Through the above steps, graphene is coated on the surface of the alumina fibers, and the surface of the alumina fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The alumina fibers are cross-linked by graphene coated on the surface, and the composite fibers are randomly overlapped to form a non-woven fabric structure. The areal density is 95.7 g/m.sup.2, the breaking strength is 2.24 GPa, the electrical conductivity is 4.1×10.sup.4 S/m, and the thermal conductivity is 23 W/mK.

Example 8-4

(191) (1) The surface of alumina fibers that are arranged in parallel is repeatedly coated with a graphene oxide dispersion in ethylene glycol and dried. The process is repeated 12 times, to obtain alumina filament fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(192) (2) The alumina filament fibers coated with graphene oxide obtained in Step (1) are subjected to surface swelling in ethylene glycol, and then combined and dried to form a non-twisted yarn, where the drying temperature is below 100° C. to volatilize ethylene glycol.

(193) (3) The graphene oxide crosslinked alumina filament fibers obtained in Step (2) are placed in a closed vessel containing hydroiodic acid and reduced at 90° C. for 18 hrs.

(194) Through the above steps, graphene is coated on the surface of the alumina fibers, and the surface of the alumina fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The alumina fibers are cross-linked by graphene coated on the surface, and the composite fibers are arranged in parallel to form a non-twisted yarn structure. The breaking strength is 2.42 GPa, the electrical conductivity is 7.2×10.sup.4 S/m, and the thermal conductivity is 27 W/mK.

Example 8-5

(195) (1) The surface of alumina fibers that are arranged in parallel is repeatedly coated with an aqueous graphene oxide dispersion and dried. The process is repeated 15 times, to obtain alumina fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(196) (2) The alumina fibers coated with graphene oxide obtained in Step (1) are subjected to surface swelling in ethylene glycol, and then combined and dried to form a non-twisted yarn, where the drying temperature is below 100° C. to volatilize ethylene glycol.

(197) (3) The graphene oxide crosslinked alumina filament fibers obtained in Step (2) are placed in a closed vessel containing hydroiodic acid and reduced at 90° C. for 18 hrs.

(198) Through the above steps, graphene is coated on the surface of the alumina fibers, and the surface of the alumina fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The alumina fibers are cross-linked by graphene coated on the surface, and the composite fibers are arranged in parallel to form a non-twisted yarn structure. The breaking strength is 2.52 GPa, the electrical conductivity is 7.6×10.sup.4 S/m, and the thermal conductivity is 28 W/mK.

Example 9-1

(199) (1) ultrasonically washing glass fibers in acetone to remove the oil on the surface, and drying;

(200) (2) The surface of glass fibers obtained in Step (1) is repeatedly coated with an aqueous graphene oxide dispersion and dried. The process is repeated 15 times, to obtain glass fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(201) (3) The glass fibers coated with graphene oxide obtained in Step (2) are subjected to surface swelling in water, and then overlapped and dried to form a non-woven fabric, where the drying temperature is below 100° C.

(202) (4) The graphene oxide crosslinked glass fibers obtained in Step (3) are placed in a closed vessel containing hydrazine hydrate and reduced at 80° C. for 12 hrs.

(203) Through the above steps, graphene is coated on the surface of the glass fibers, and the surface of the glass fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The glass fibers are cross-linked by graphene coated on the surface, and the composite fibers are randomly overlapped to form a non-woven fabric structure. The areal density is 92.4 g/m.sup.2, the breaking strength is 134 N, the electrical conductivity is 6.5×10.sup.4 S/m, and the thermal conductivity is 26 W/mK.

(204) TABLE-US-00009 TABLE 9 Concentration Thickness Areal density of graphene of graphene of composite Breaking Electrical Thermal oxide oxide layer fiber strength conductivity conductivity (mg/ml) (μm) (g/m.sup.2) (N) (S/m) (W/mK) 0 0 85.9 106 — — 0.1 0.5 87.2 116 5.8 × 10.sup.2 14 1 1 88.6 128 1.8 × 10.sup.3 19 7 3 92.4 134 6.5 × 10.sup.4 26 13 5.2 96.8 119 1.1 × 10.sup.3 17

(205) In addition, the graphene oxide concentration and coating thickness are the optimum results obtained after repeated testes. It can be seen from Table 9 that with the same number of coatings, when the concentration of graphene oxide is 7 mg/ml, the thickness of the graphene oxide coating on the surface of the glass fibers is 3 μm; the breaking strength, electrical conductivity, and thermal conductivity of the obtained glass fiber non-woven fabric are the highest; and the cross-linking effect is optimum. As the concentration of graphene oxide declines, the thickness of graphene oxide on the surface of the glass fibers decreases; the breaking strength, electrical conductivity, and thermal conductivity of the obtained glass fiber non-woven fabric are lowered; and the cross-linking effect is deteriorated. As the concentration of graphene oxide rises, the thickness of graphene oxide on the surface of the glass fibers increases, and distributed unevenly, and the degree of crosslinking decreases; and the breaking strength, electrical conductivity, and thermal conductivity of the obtained glass fiber non-woven fabric are lowered.

Example 9-2

(206) (1) ultrasonically washing glass fibers in acetone to remove the oil on the surface, and drying;

(207) (2) The surface of glass fibers obtained in Step (1) is repeatedly coated with a graphene oxide dispersion in N,N-dimethylformamide and dried. The process is repeated 13 times, to obtain glass fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(208) (3) The glass fibers coated with graphene oxide obtained in Step (2) are subjected to surface swelling in water, and then overlapped and dried to form a non-woven fabric, where the drying temperature is below 100° C.

(209) (4) The graphene oxide crosslinked glass fibers obtained in Step (3) are placed in a closed vessel containing hydrazine hydrate and reduced at 80° C. for 12 hrs.

(210) Through the above steps, graphene is coated on the surface of the glass fibers, and the surface of the glass fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The glass fibers are cross-linked by graphene coated on the surface, and the composite fibers are randomly overlapped to form a non-woven fabric structure. The areal density is 93.1 g/m.sup.2, the breaking strength is 136 N, the electrical conductivity is 6.1×10.sup.4 S/m, and the thermal conductivity is 26 W/mK.

Example 9-3

(211) (1) ultrasonically washing glass fibers in acetone to remove the oil on the surface, and drying;

(212) (2) The surface of glass fibers obtained in Step (1) is repeatedly coated with a graphene oxide dispersion in ethanol and dried. The process is repeated 16 times, to obtain glass fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(213) (3) The glass fibers coated with graphene oxide obtained in Step (2) are subjected to surface swelling in water, and then overlapped and dried to form a non-woven fabric, where the drying temperature is below 100° C.

(214) (4) The graphene oxide crosslinked glass fibers obtained in Step (3) are placed in a closed vessel containing hydroiodic acid and reduced at 90° C. for 18 hrs.

(215) Through the above steps, graphene is coated on the surface of the glass fibers, and the surface of the glass fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The glass fibers are cross-linked by graphene coated on the surface, and the composite fibers are randomly overlapped to form a non-woven fabric structure. The areal density is 94.6 g/m.sup.2, the breaking strength is 139N, the electrical conductivity is 5.7×10.sup.4 S/m, and the thermal conductivity is 23 W/mK.

Example 9-4

(216) (1) Glass filament fibers that are arranged in parallel are ultrasonically washed in acetone to remove the oil on the surface, and dried.

(217) (2) The surface of glass fibers obtained in Step (1) is repeatedly coated with a graphene oxide dispersion in ethylene glycol and dried. The process is repeated 12 times, to obtain glass filament fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 m.

(218) (3) The glass filament fibers coated with graphene oxide obtained in Step (2) are subjected to surface swelling in ethylene glycol, and then combined and dried to form a non-twisted yarn, where the drying temperature is below 100° C. to volatilize ethylene glycol.

(219) (4) The graphene oxide crosslinked glass filament fibers obtained in Step (3) are placed in a closed vessel containing hydroiodic acid and reduced at 90° C. for 18 hrs.

(220) Through the above steps, graphene is coated on the surface of the glass fibers, and the surface of the glass fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The glass fibers are cross-linked by graphene coated on the surface, and the composite fibers are arranged in parallel to form a non-twisted yarn structure. The breaking strength is 2.1 GPa, the electrical conductivity is 7.3×10.sup.4 S/m, and the thermal conductivity is 27 W/mK.

Example 9-5

(221) (1) Glass filament fibers that are arranged in parallel are ultrasonically washed in acetone to remove the oil on the surface, and dried.

(222) (2) The surface of glass fibers obtained in Step (1) is repeatedly coated with an aqueous graphene oxide dispersion and dried. The process is repeated 15 times, to obtain glass fibers coated with graphene oxide on the surface. The thickness of the graphene oxide layer is 3 μm.

(223) (3) The glass fibers coated with graphene oxide obtained in Step (2) are subjected to surface swelling in ethylene glycol, and then combined and dried to form a non-twisted yarn, where the drying temperature is below 100° C. to volatilize ethylene glycol.

(224) (4) The graphene oxide crosslinked glass filament fibers obtained in Step (3) are placed in a closed vessel containing hydroiodic acid and reduced at 90° C. for 18 hrs.

(225) Through the above steps, graphene is coated on the surface of the glass fibers, and the surface of the glass fibers and the graphene sheet are connected by van der Waals force and hydrogen bonding. The glass fibers are cross-linked by graphene coated on the surface, and the composite fibers are arranged in parallel to form a non-twisted yarn structure. The breaking strength is 2.17 GPa, the electrical conductivity is 5.9×10.sup.4 S/m, and the thermal conductivity is 25 W/mK.

Example 10-1

(226) (1) Graphene oxide having an average size greater than 50 μm is formulated into an aqueous graphene oxide solution having a concentration of 7 mg/mL. The graphene oxide solution is spread at a thickness of 5 mm by blade coating to form a film, which is naturally dried, to obtain a graphene oxide film.

(227) (2) Two graphene oxide films having a size of 8 cm*8 cm are sprayed with a liquid and laminated. Specifically, a layer of aqueous graphene oxide solution having a concentration of 4 mg/mL is uniformly sprayed on the surface of the graphene oxide films, and then the graphene oxide films are bonded together in the thickness direction.

(228) (3) The bonded graphene oxide composite film is dried in an oven at a temperature of 40° C.

(229) (4) The dried graphene oxide composite film and the original graphene oxide film are respectively transferred to a hot-pressing chamber of a hot press, heated up to 200° C. at a ramping rate of 2° C./min, and then hot pressed by repeating the following hot pressing process 10 times: maintaining the pressure at 20 MPa for 1 hr, gradually releasing the pressure to 0 MPa, and evacuating the hot-pressing chamber for 5 min to a vacuum level of −50 KPa; then heated to 300° C. for 0.5 hr at a ramping rate of 2° C./min, and then hot pressed by repeating the following hot pressing process 5 times: maintaining the pressure at 60 MPa for 1 hr, gradually releasing the pressure to 0 MPa, and evacuating the hot-pressing chamber for 5 min to a vacuum level of −50 KPa; and naturally cooled after hot pressing.

(230) (5) The film that is hot pressed in Step 4 is heated to a temperature of 2800° C. at a ramping rate of 5° C./min under an inert gas atmosphere and further hot pressed, where the temperature and pressure are held for 2 hrs; and the pressure is 60 MPa. After cooling, a graphene film with high thermal conductivity is obtained.

(231) Through the above steps, the graphene oxide films are fused by the force at the bonded site to form an integrated structure. Through further low-temperature hot pressing and high temperature hot pressing, annealing, and reduction, a graphene composite film with high thermal conductivity is finally obtained. The graphene composite film bonded by coating the graphene oxide solution has fewer defects and more compact and complete structure because the graphene oxide therein can also fill the gaps. As tested, the thickness of the original graphene film is 26 μm, the pleat density on the graphene sheet is 92 mm/mm.sup.2, and the graphene sheet has very few defects, and has an I.sub.D/I.sub.G ratio of 0.004, a porosity of 8.6%, a density of 2.01 g/cm.sup.3, and an in-plane thermal conductivity of 1613.2 W/mK. After the above treatments, the thickness of the graphene composite film is 53 μm, the pleat density on the graphene sheet is 113 mm/mm.sup.2, and the graphene sheet has very few defects, and has an ID/TG ratio of 0.005, a porosity of 9.0%, a density of 1.99 g/cm.sup.3, and an in-plane thermal conductivity of 1563.9 W/mK. There is no delamination in the thick graphene film, and the distance between any two adjacent graphene sheets is less than 20 nm.

Example 10-2

(232) (1) Graphene oxide having an average size greater than 50 μm is formulated into an aqueous graphene oxide solution having a concentration of 7 mg/mL. The graphene oxide solution is spread at a thickness of 5 mm by blade coating to form a film, which is naturally dried, to obtain a graphene oxide film.

(233) (2) Ten graphene oxide films having a size of 8 cm*8 cm are sprayed with different liquids and laminated. Specifically, the surface of the graphene oxide films is uniformly sprayed with deionized water to swell the surface, and then multiple graphene oxide films are bonded together in the thickness direction. The sample thus prepared is designated as Sample A. The surface of the graphene oxide films is uniformly coated with a layer of aqueous graphene oxide solution having a concentration of 4 mg/mL, and then multiple graphene oxide films are bonded together in the thickness direction. The sample thus prepared is designated as Sample B.

(234) (3) The two bonded graphene oxide composite films are dried in an oven at a temperature of lower than 40° C.

(235) (4) The dried graphene oxide composite films are transferred to a hot-pressing chamber of a hot press, heated to 200° C. at a ramping rate of 2° C./min, and then hot pressed by repeating the following hot pressing process 10 times: maintaining the pressure at 20 MPa for 1 hr, gradually releasing the pressure to 0 MPa, and evacuating the hot-pressing chamber for 5 min to a vacuum level of −50 KPa; then heated to 300° C. for 0.5 hr at a ramping rate of 2° C./min, and then hot pressed by repeating the following hot pressing process 5 times: maintaining the pressure at 60 MPa for 1 hr, gradually releasing the pressure to 0 MPa, and evacuating the hot-pressing chamber for 5 min to a vacuum level of −50 KPa; and naturally cooled after hot pressing.

(236) (5) The graphene oxide composite film that is hot pressed in Step 4 is heated to a temperature of 2800° C. at a ramping rate of 5° C./min under an inert gas atmosphere, and further hot pressed, where the temperature and pressure are held for 2 hrs; and the pressure is 60 MPa. After cooling, a thick graphene film with high thermal conductivity is obtained.

(237) Through the above steps, the graphene oxide films are fused by the force at the bonded site to form an integrated structure. Through further low-temperature hot pressing and high temperature hot pressing, annealing, and reduction, a thick graphene composite film with high thermal conductivity is finally obtained. The thick graphene composite film bonded by coating the graphene oxide solution has fewer defects and more compact and complete structure because the graphene oxide therein can also fill the gaps. As tested, the thickness of Sample A is 279 μm, the pleat density on the graphene sheet is 143 mm/mm.sup.2, and the graphene sheet has very few defects, and has an I.sub.D/I.sub.G ratio of 0.008, a porosity of 11.8%, and a density of 1.94 g/cm.sup.3. As shown in FIG. 7, there is no delamination in the thick graphene film, and the distance between any two adjacent graphene sheets is less than 20 nm. The thermal conductivity is 1448.9 W/mK. The thickness of Sample B is 291 μm, the pleat density on the graphene sheet is 134 mm/mm.sup.2, and the graphene sheet has very few defects, and has an I.sub.D/I.sub.G ratio of 0.007, a porosity of 11.4%, and a density of 1.95 g/cm.sup.3. As shown in FIG. 8, there is no delamination in the thick graphene film, and the distance between any two adjacent graphene sheets is less than 20 nm. The thermal conductivity is 1495.8 W/mK.

Example 10-3

(238) (1) Graphene oxide with a high degree of oxidation and graphene oxide with a low degree of oxidation that have an average size of greater than 50 μm are respectively prepared into a 7 mg/mL aqueous graphene oxide solution, and spread at a thickness of 5 mm by blade coating to form a film, which is naturally dried, to obtain a graphene oxide film with a high degree of oxidation and a graphene oxide film with a low degree of oxidation.

(239) (2) Ten graphene oxide films with a high degree of oxidation and ten graphene oxide films with a low degree of oxidation are respectively laminated, specifically by uniformly spraying deionized water on the surface of the graphene oxide film to swell the surface, and then bonding the plurality of graphene oxide films together in the thickness direction; The graphene oxide films can be self-bonded by the force at the bonding interface to obtain a graphene oxide composite film with a high degree of oxidation and a graphene oxide composite film with a low degree of oxidation, which are respectively designated as Sample C and Sample D.

(240) (3) The two bonded graphene oxide composite film are dried in an oven at a temperature of lower than 40° C., where a pressure is gradually applied during the drying process.

(241) (4) The dried graphene oxide composite films are transferred to a hot-pressing chamber of a hot press, heated to 200° C. at a ramping rate of 2° C./min, and then hot pressed by repeating the following hot pressing process 10 times: maintaining the pressure at 20 MPa for 1 hr, gradually releasing the pressure to 0 MPa, and evacuating the hot-pressing chamber for 5 min to a vacuum level of −50 KPa; then heated to 300° C. for 0.5 hr at a ramping rate of 2° C./min, and then hot pressed by repeating the following hot pressing process 5 times: maintaining the pressure at 60 MPa for 1 hr, gradually releasing the pressure to 0 MPa, and evacuating the hot-pressing chamber for 5 min to a vacuum level of −50 KPa; and naturally cooled after hot pressing.

(242) (5) The graphene oxide composite film that is hot pressed in Step 4 is heated to a temperature of 2800° C. at a ramping rate of 5° C./min under an inert gas atmosphere, and further hot pressed, where the temperature and pressure are held for 2 hrs; and the pressure is 60 MPa. After cooling, a thick graphene film with high thermal conductivity is obtained.

(243) Through the above steps, the graphene oxide films are fused by the force at the bonded site to form an integrated structure. Through further low-temperature hot pressing and high temperature hot pressing, annealing, and reduction, a thick graphene composite film with high thermal conductivity is finally obtained. Because the graphene oxide with high degree of oxidation has more functional groups, after the graphene oxide films with high degree of oxidation are bonded by evenly coating a layer of water, the hydrogen bonding and van der Waals forces at the interface are stronger, leading to a better bonding effect and a more compact structure. As tested, the thickness of Sample C is 261 μm, the pleat density on the graphene sheet is 151 mm/mm.sup.2, and the graphene sheet has very few defects, and has an ID/TG ratio of 0.008, a porosity of 12.3%, a density of 1.93 g/cm.sup.3, and an in-plane thermal conductivity of 1466.9 W/mK. There is no delamination in the thick graphene film, and the distance between any two adjacent graphene sheets is less than 20 nm. The thickness of Sample D is 255 μm, the pleat density on the graphene sheet is 139 mm/mm.sup.2, and the graphene sheet has very few defects, and has an I.sub.D/I.sub.G ratio of 0.09, a porosity of 13.2%, a density of 1.91 g/cm.sup.3, and a thermal conductivity of 1418.7 W/mK. There is no delamination in the thick graphene film, and the distance between any two adjacent graphene sheets is less than 20 nm.

Example 10-4

(244) (1) Graphene oxide having an average size greater than 50 μm is formulated into an aqueous graphene oxide solution having a concentration of 7 mg/mL. The graphene oxide solution is spread at a thickness of 5 mm and 2.5 mm respectively by blade coating to form films, which are naturally dried, to obtain two graphene oxide films having different thickness.

(245) (2) Fiver thick graphene oxide films and ten thin graphene oxide films are respectively laminated. Specifically, a layer of aqueous graphene oxide solution having a concentration of 4 mg/mL is uniformly sprayed on the surface of the graphene oxide films, and then the graphene oxide films are bonded together in the thickness direction, to obtain two different graphene oxide composite films, which are designated as Sample E and Sample F respectively.

(246) (3) The two bonded graphene oxide composite film are dried in an oven at a temperature of lower than 40° C., where a pressure is gradually applied during the drying process.

(247) (4) The dried graphene oxide composite films are transferred to a hot-pressing chamber of a hot press, heated to 200° C. at a ramping rate of 2° C./min, and then hot pressed by repeating the following hot pressing process 10 times: maintaining the pressure at 20 MPa for 1 hr, gradually releasing the pressure to 0 MPa, and evacuating the hot-pressing chamber for 5 min to a vacuum level of −50 KPa; then heated to 300° C. for 0.5 hr at a ramping rate of 2° C./min, and then hot pressed by repeating the following hot pressing process 5 times: maintaining the pressure at 60 MPa for 1 hr, gradually releasing the pressure to 0 MPa, and evacuating the hot-pressing chamber for 5 min to a vacuum level of −50 KPa; and naturally cooled after hot pressing.

(248) (5) The graphene oxide composite film that is hot pressed in Step 4 is heated to a temperature of 2800° C. at a ramping rate of 5° C./min under an inert gas atmosphere, and further hot pressed, where the temperature and pressure are held for 2 hrs; and the pressure is 60 MPa. After cooling, a thick graphene film with high thermal conductivity is obtained.

(249) Through the above steps, the graphene oxide films are fused by the force at the bonded site to form an integrated structure. The defects are repaired through further low-temperature hot pressing and high temperature treatment, and thick graphene films with high thermal conductivity are finally obtained. As tested, the thickness of Sample E is 135 μm, the pleat density on the graphene sheet is 121 mm/mm.sup.2, and the graphene sheet has very few defects, and has an I.sub.D/I.sub.G ratio of 0.009, a porosity of 12.7%, a density of 1.92 g/cm.sup.3, and a thermal conductivity of 1518.4 W/mK. There is no delamination in the thick graphene film, and the distance between any two adjacent graphene sheets is less than 20 nm. The thickness of the graphene composite film is 138 μm, the pleat density on the graphene sheet is 118 mm/mm.sup.2, and the graphene sheet has very few defects, and has an I.sub.D/I.sub.G ratio of 0.009, a porosity of 13.2%, a density of 1.91 g/cm.sup.3, and a thermal conductivity of 1521.7 W/mK. There is no delamination in the thick graphene film, and the distance between any two adjacent graphene sheets is less than 20 nm.

Example 10-5

(250) (1) Graphene oxide having an average size greater than 50 μm is formulated into an aqueous graphene oxide solution having a concentration of 7 mg/mL. The graphene oxide solution is spread at a thickness of 5 mm by blade coating to form a film, which is naturally dried, to obtain a graphene oxide film.

(251) (2) 100 graphene oxide films having a size of 4 cm*4 cm are laminated. Specifically, a layer of aqueous graphene oxide solution having a concentration of 4 mg/mL is uniformly sprayed on the surface of the graphene oxide films, and then the graphene oxide films are bonded together in the thickness direction.

(252) (3) The bonded graphene oxide composite film is dried in an oven at a temperature of lower than 40° C.

(253) (4) The dried graphene oxide composite films are transferred to a hot-pressing chamber of a hot press, heated to 200° C. at a ramping rate of 2° C./min, and then hot pressed by repeating the following hot pressing process 10 times: maintaining the pressure at 20 MPa for 1 hr, gradually releasing the pressure to 0 MPa, and evacuating the hot-pressing chamber for 5 min to a vacuum level of −100-10 KPa; then heated to 300° C. for 0.5 hr at a ramping rate of 2° C./min, and then hot pressed by repeating the following hot pressing process 5 times: maintaining the pressure at 60 MPa for 1 hr, gradually releasing the pressure to 0 MPa, and evacuating the hot-pressing chamber for 5 min to a vacuum level of −100-10 KPa, and naturally cooled after hot pressing.

(254) (5) The graphene oxide composite film that is hot pressed in Step 4 is heated to a temperature of 2500° C. at a ramping rate of 5° C./min under an inert gas atmosphere, and further hot pressed, where the temperature and pressure are held for 2 hrs; and the pressure is 60 MPa. After cooling, a thick graphene film with high thermal conductivity is obtained.

(255) Through the above steps, the graphene oxide films are fused by the force at the bonded site and the graphene oxide in the coating solution fills the gaps to form an integrated structure. Through further low-temperature hot pressing and high temperature hot pressing, annealing, and reduction, a thick graphene composite film with high thermal conductivity is finally obtained. As tested, the thickness of the graphene film is 2.93 mm, the pleat density on the graphene sheet is 310 mm/mm.sup.2, and the graphene sheet has very few defects, and has an I.sub.D/I.sub.G ratio of 0.018, a porosity of 20.1%, a density of 1.74 g/cm.sup.3, and a thermal conductivity of 1287.1 W/mK. There is no delamination in the thick graphene film, and the distance between any two adjacent graphene sheets is less than 20 nm.

Example 10-6

(256) (1) Graphene oxide having an average size greater than 100 μm is formulated into an aqueous graphene oxide solution having a concentration of 1 mg/mL, and naturally dried after a film is formed from the solution, to obtain a graphene oxide film. The thickness of the graphene oxide film is 15 μm, and the carbon/oxygen ratio in the graphene oxide film is 1.8.

(257) (2) A plurality of graphene oxide films is laminated specifically by uniformly spraying water on the surface of the graphene oxide film to swell the surface, and then bonding the plurality of graphene oxide films together in the thickness direction.

(258) (3) The bonded graphene oxide composite film is dried in an oven at a temperature of 40° C.

(259) (4) The dried graphene oxide composite film is transferred to a hot-pressing chamber of a hot press, heated to 200° C. at a ramping rate of 0.1° C./min, and then hot pressed by repeating the following hot pressing process 8 times: maintaining the pressure at 20 MPa for 1 hr, gradually releasing the pressure to 0 MPa, and evacuating the hot-pressing chamber for 5 min to a vacuum level of −100 KPa; then heated to 300° C. for 0.5 hr at a ramping rate of 0.1° C./min, and then hot pressed by repeating the following hot pressing process 4 times: maintaining the pressure at 60 MPa for 1 hr, gradually releasing the pressure to 0 MPa, and evacuating the hot-pressing chamber for 5 min to a vacuum level of −100 KPa; and naturally cooled after hot pressing.

(260) (5) The graphene oxide composite film that is hot pressed in Step 4 is heated to a temperature of 1800° C. at a ramping rate of 1° C./min under an inert gas atmosphere, and further hot pressed, where the temperature and pressure are held for 8 hrs; and the pressure is 60 MPa. After pressing at a reduced temperature, a thick graphene film with high thermal conductivity is obtained.

(261) As tested, the thickness of the prepared thick graphene film is 54 μm, the density is 2.1 g/cm.sup.3, the porosity is 5%, the thermal conductivity is 1987.1 W/mK, and the pleat density on the graphene sheet is 50 mm/mm.sup.2; and the graphene sheet has few detects, and has an I.sub.D/I.sub.G ratio of 0.005. There is no delamination in the thick graphene film, and the distance between any two adjacent graphene sheets is less than 20 nm.

Example 10-7

(262) (1) Graphene oxide having an average size greater than 50 μm is formulated into an aqueous graphene oxide solution having a concentration of 20 mg/mL, and naturally dried after a film is formed from the solution, to obtain a graphene oxide film having a thickness of 50 μm and a carbon/oxygen ratio of 2.1.

(263) (2) A plurality of graphene oxide films is laminated specifically by uniformly spraying an aqueous graphene oxide solution having a concentration of 1 mg/mL on the surface of the graphene oxide film to swell the surface, and then bonding the plurality of graphene oxide films together in the thickness direction.

(264) (3) The bonded graphene oxide composite film is dried in an oven at a temperature of 30° C.

(265) (4) The dried graphene oxide composite film is transferred to a hot-pressing chamber of a hot press, heated to 200° C. at a ramping rate of 5° C./min, and then hot pressed by repeating the following hot pressing process 10 times: maintaining the pressure at 20 MPa for 1 hr, gradually releasing the pressure to 0 MPa, and evacuating the hot-pressing chamber for 5 min to a vacuum level of −10 KPa; then heated to 300° C. for 0.5 hr at a ramping rate of 5° C./min, and then hot pressed by repeating the following hot pressing process 6 times: maintaining the pressure at 60 MPa for 1 hr, gradually releasing the pressure to 0 MPa, and evacuating the hot-pressing chamber for 5 min to a vacuum level of −10 KPa; and naturally cooled after hot pressing.

(266) (5) The graphene oxide composite film that is hot pressed in Step 4 is heated to a temperature of 3000° C. at a ramping rate of 20° C./min under an inert gas atmosphere, and further hot pressed, where the temperature and pressure are held for 0.5 hrs; and the pressure is 10 MPa. After pressing at a reduced temperature, a thick graphene film with high thermal conductivity is obtained.

(267) As tested, the thickness of the prepared thick graphene film is 4.56 mm, the porosity is 40%, and the pleat density on the graphene sheet is about 500 mm/mm.sup.2; and the graphene sheet has few detects, and has an ID/TG ratio of 0.02. There is no delamination in the thick graphene film, and the distance between any two adjacent graphene sheets is less than 20 nm.