High-density high-strength carbon graphite material and short-process preparation method thereof

Abstract

The application discloses a high-density and high-strength carbon graphite material and a short-process preparation method thereof. The short-process preparation method is as follows: carbon raw materials are pressed and formed to obtain green bodies, the green bodies are baked in a sealed container, and finally graphitization treatment is performed to obtain the high-density and high-strength carbon graphite material. The carbon raw materials are green coke powder or mesophase carbon microbeads. Carbon raw materials of the same type as the green bodies are mixed in the buried burning materials during the baking. The high-density and high-strength carbon graphite material can be prepared by the short-process preparation method, and the carbon graphite material can be effectively prevented from cracking, and the yield of finished products can be improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of carbon materials, and particularly relates to a high-density and high-strength carbon graphite material and a short-process preparation method thereof. BACKGROUND

[0002] Graphite sealing materials are crowned as the "sealing king" due to their low density, self-lubricating property, good chemical stability, high thermal conductivity, low expansion, small friction coefficient and good processability. The graphite sealing materials used in aerospace have extremely high performance requirements due to their harsh working conditions, and need to have the characteristics of high density and high strength.

[0003] Carbon graphite materials include solid materials mainly composed of non-graphitic carbon and graphitic carbon. Currently, there are two main methods for preparing carbon graphite materials in China. The first traditional process is to use calcined coke as aggregate and coal pitch as binder to prepare graphite materials through processes such as mixing, sheet rolling, molding, baking, impregnation and graphitization. In order to meet the use requirements, the materials often need to undergo multiple impregnation-baking processes, and the preparation method is complicated, the cycle is long, and the energy consumption is large. The second self-sintering process uses green coke or mesocarbon microbeads with self-sintering ability as raw materials, and does not need mixing, using the volatile components carried by the raw materials as binders. Compared with the traditional process, the self-sintering process can save the processes of mixing, sheet rolling and repeated impregnation-baking, and the preparation cycle and cost are significantly reduced.

[0004] However, the current self-sintering process is not the mainstream for preparing high-density and high-strength carbon graphite materials, and the main reasons are as follows: first, the self-sintering carbon block prepared by the self-sintering process has a low yield and is prone to cracking; second, the carbon block has poor performance and low strength and density, and the performance of the once-baked and graphitized product cannot meet the use requirements. In order to meet the use requirements of high density and high strength, the self-sintering carbon block also needs to undergo repeated impregnation-baking processes, and the preparation cycle of the material is still very long, which does not fundamentally solve the problem of high cost of high-strength carbon graphite.

[0005] Related research shows that the self-sintering process using ultra-fine particle (D50≤5 μm) green coke powder or mesocarbon microbeads as raw materials is an effective way to prepare high-density and high-strength carbon graphite materials in a short process, but the current preparation methods are prone to cracking and poor performance. Therefore, how to improve the yield and performance of ultra-fine particles as self-sintering raw materials has become a major challenge in the short-process preparation of high-density and high-strength carbon graphite materials. SUMMARY

[0006] In view of the above-mentioned deficiencies of the prior art, the purpose of the present application is to provide a high-density and high-strength carbon graphite material and a short-process preparation method thereof, which can prepare the carbon graphite material with high density and high mechanical strength in a short process, and effectively prevent the carbon graphite material from cracking and improve the yield.

[0007] The technical solution of the present application is implemented as follows:

[0008] The short-process preparation method of the high-density and high-strength carbon graphite material comprises the following steps: pressing and forming a carbon raw material to obtain a green body, then baking the green body in a sealed container, and finally graphitizing to obtain the high-density and high-strength carbon graphite material, wherein the carbon raw material is green coke powder or mesophase carbon microbeads; and the baking is performed by mixing the carbon raw material of the same type as the green body into the buried material.

[0009] Further, the green coke powder is green petroleum coke or green pitch coke, and the D50 of the green coke powder is 0.1-5 μm, and the D50 of the mesophase carbon microbeads is 0.1-10 μm.

[0010] Further, the buried material further contains heterogeneous volatile components.

[0011] Further, the heterogeneous volatile components are one or more of oil-based, organic-based and inorganic-based components which generate gas at 20-200 ℃; wherein the oil-based components include products in petroleum cracking such as coal tar and anthracene oil; the organic-based components include polar solvents such as toluene and quinoline; and the inorganic-based components include water and ethanol.

[0012] Further, the mass ratio of the carbon raw material and the heterogeneous volatile components mixed in the buried material is 1:4-4:1.

[0013] Further, the mass of the carbon raw material and the heterogeneous volatile components in the buried material accounts for 10-20% of the total mass of the buried material.

[0014] Further, the pressing and forming specifically comprises the following steps: pre-molding the carbon raw material on a flat plate vulcanizing machine at a pressure of 1-5 MPa for 10-30 s, then cold isostatic pressing at a pressure of 150-250 MPa for 5-10 min, and then standing for 10-20 h to obtain the green body.

[0015] Further, the baking specifically comprises the following steps: increasing the temperature to 1000-1200 ℃ at a rate of 0.1-4 ℃ / min under the protection of inert gas, maintaining the temperature for 2-6 h, then decreasing the temperature to below 200 ℃ at a rate of 0.1-0.5 ℃ / min, and then naturally cooling to room temperature.

[0016] Further, the graphitization treatment specific steps are as follows: under the protection of inert gas, the temperature is raised to 2400-2800 DEG C at the heating rate of 0.3-0.7 DEG C / min, the temperature is kept for 1h, then the temperature is reduced to below 200 DEG C at the cooling rate of 0.3-0.7 DEG C / min, and then the temperature is naturally cooled to room temperature.

[0017] Compared with the prior art, the present application has the following beneficial effects:

[0018] 1. The present application introduces the heterogeneous volatile and the carbonaceous raw material with the same quality as the green body into the buried burning material, that is, the strategy of introducing the heterogeneous and homogeneous artificial volatile is adopted, so that the green body can achieve the larger volume shrinkage, smaller mass loss, better homogeneity, less internal defects and porosity in the baking process, thereby achieving the purpose of densification and enhancement.

[0019] The green body formed by the green coke powder and the mesophase carbon microbeads will have a large number of chemical reactions in the baking process, and release a large amount of CO, CO2, H2, CH4 and other gases, which can be compressed under the action of the closed container to play the role of pressurization, which is beneficial to increase the volume shrinkage of the green body block. At the same time, the carbonaceous raw material (homogeneous volatile) and the heterogeneous volatile in the buried burning material will release gas before the homogeneous volatile and the green body in the heating process, so that the internal baking pressure is rapidly increased, and then the homogeneous volatile will release gas. At the same time, because the green body block is located in the center of the buried burning material and the green body block is block-shaped, and the homogeneous volatile is powder-shaped, so the chemical rate of the homogeneous volatile is greater than that of the green body block. Therefore, the gas released by the homogeneous volatile will increase the polycondensation reaction and polymerization reaction in the subsequent green body block. In addition, in the liquid phase sintering stage, the binding components in the homogeneous volatile will penetrate into the green body block, thereby avoiding the gradient flow of the binding components in the liquid phase sintering reaction caused by the influence of gravity, so as to avoid the uneven density distribution of the block, and greatly reduce the mass loss of the green body block, thereby solving the problems of too small volume shrinkage, too large mass loss, and cracking caused by the uneven distribution of the binding components due to the influence of gravity.

[0020] 2. The present application can effectively prevent the carbon graphite material from cracking, so that the yield can reach 100%, and the volume density of the carbon graphite material prepared by the present application can reach 1.93 g / cm 3 , the open porosity is only 1.08%, the bending strength is 144.00 MPa, and the compressive strength is 259.45 MPa, which is far superior to domestic and imported graphite products.

[0021] 3、The preparation process of the present application is simple, only needs forming-baking-graphitization process, the whole process from raw materials to high density and high strength graphite block only needs 10-15 days, including baking 4-10 days and graphitization 5-7 days. It does not need to treat raw materials and repeated impregnation-baking, has the advantages of short process for preparing carbon and graphite materials, and has wide industrial application value. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 -Physical map of the carbon and graphite material baking block prepared in Example 1 and Comparative Example 3. Among them, Figure 1 (a) is an optical photo of the baking block SCB-E prepared in Comparative Example 3, Figure 1 (b) is an optical photo of the carbon and graphite material baking product SCB-A prepared in Example 1.

[0023] Figure 2 -Graphite block bending and compressive stress-strain curve diagram prepared in Example 1, wherein Figure 2 (a) is a bending stress-strain curve diagram, Figure 2 (b) is a compressive stress-strain curve diagram.

[0024] Figure 3 -Surface morphology diagram and backscattering diagram of the graphite block SG-A prepared in Example 1, wherein, Figure 3 (b) are respectively SEM and backscattering SEM diagrams of SG-A surface magnification (x2000) and its corresponding backscattering SEM diagram; Figure 3 (c), Figure 3 (d) are respectively SEM and backscattering SEM diagrams of SG-A surface magnification (x200) and its corresponding backscattering SEM diagram.

[0025] Figure 4 -Cross-sectional morphology diagram and backscattering diagram of the graphite block SG-A prepared in Example 1, wherein, Figure 4 (a), Figure 4 (b) are respectively SEM and backscattering SEM diagrams of SG-A cross section magnification (x2000) and its corresponding backscattering SEM diagram; Figure 4 (c), Figure 4 (d) are respectively SEM and backscattering SEM diagrams of SG-A cross section magnification (x200) and its corresponding backscattering SEM diagram. DETAILED DESCRIPTION

[0026] The present application will be further described in detail below in combination with the drawings and specific embodiments.

[0027] Example 1

[0028] A short process preparation method of high density and high strength carbon and graphite material, which adopts self-sintering mode to sinter the carbon and graphite material in the baking process, comprising the following steps:

[0029] (1) Green petroleum coke powder with an average particle size of 2 μm was molded under a flat press at a pressure of 3 MPa, and the block was then isostatically pressed at 200 MPa for 10 min and left to stand for 12 h or more to obtain a green body.

[0030] (2) The green body block obtained in (1) was placed in a closed sagger, and the remaining space was filled with buried burning material mixed with a certain amount of green petroleum coke powder and anthracene oil as artificial volatile matter, wherein the mass ratio of green petroleum coke powder to anthracene oil was 1:1, and the total mass of green petroleum coke powder and anthracene oil was 20% of the total mass of the buried burning material.

[0031] (3) The sagger loaded in step (2) was placed in a five-sided furnace, and heated to 1050°C at a heating rate of 0.1°C / min under argon protection, and held for 4 h, and then cooled to below 200°C at a cooling rate of 0.1°C / min, and then naturally cooled to room temperature to obtain the high-density high-strength carbon graphite baked block, designated as SCB-A.

[0032] (4) The carbon graphite baked block SCB-A prepared in step (3) was heated to 2500°C at a heating rate of 0.5°C / min under argon protection, and held for 1 h, and then cooled to below 200°C at a cooling rate of 0.5°C / min, and then naturally cooled to room temperature to obtain the high-density high-strength graphite block, designated as SG-A.

[0033] Example 2

[0034] This example is the same as Example 1, except that no anthracene oil was mixed in the buried burning material in this example, and the obtained high-density high-strength carbon graphite baked block was designated as SCB-B, and the high-density high-strength graphite block obtained after graphitization treatment was designated as SG-B.

[0035] Comparative Example 1

[0036] This example is the same as Example 1, except that no green coke powder and anthracene oil were mixed in the buried burning material in this example, and the obtained high-density high-strength carbon graphite baked block was designated as SCB-C.

[0037] Comparative Example 2

[0038] This example is the same as Example 1, except that no green coke powder and anthracene oil were mixed in the buried burning material in this example, and the sagger was semi-closed, and the obtained high-density high-strength carbon graphite baked block was designated as SCB-D.

[0039] Comparative Example 3

[0040] This example is the same as Example 1, except that no green coke powder and anthracene oil were mixed in the buried burning material in this example, and the sagger was open, and the obtained high-density high-strength carbon graphite baked block was designated as SCB-E.

[0041] 1. The performance of the calcined blocks SCB-A, SCB-B, SCB-C, SCB-D and SCB-E obtained from Examples 1-2 and Comparative Examples 1-3 was tested according to the test method of the national standard, and the mass loss rate and the volume shrinkage rate were the mass / volume loss rate of the sample after calcination. The basic performance parameters of the calcined blocks are shown in Table 1.

[0042] As can be seen from Table 1, the calcined blocks prepared by introducing artificial volatile components have obvious performance advantages. For the artificial volatile component self-sintering process using raw petroleum coke powder and anthracene oil mixed buried burning material as filler, the density of the calcined blocks can reach 1.72 g / cm 3 , while the density of the calcined blocks prepared by artificial volatile component pressure using only raw petroleum coke powder mixed buried burning material as filler can reach 1.69 g / cm 3 , the density of the calcined blocks prepared by artificial volatile component pressure using only green body is only 1.65 g / cm 3 , the density of the calcined blocks prepared by semi-closed sagger in a semi-pressure five-side furnace is only 1.52 g / cm 3 , and the calcined blocks prepared by open self-sintering process directly using sagger in a five-side furnace cracked. The Shore hardness, volume shrinkage rate and open porosity of all the calcined blocks showed a consistent trend with the density.

[0043] As can be seen from SCB-A and SCB-B, the effect of the combined action of homogeneous and heterogeneous volatile components is better than that of only homogeneous volatile components, which can greatly reduce the mass loss of the green body, improve the volume shrinkage, reduce the porosity, increase the density and strength, and improve the yield.

[0044] Table 1. Basic performance parameters of calcined blocks

[0045] Performance parameters SCB-A SCB-B SCB-C SCB-D SCB-E Green density (g / cm 3 )]]> 1.25 1.25 1.25 1.25 1.25 Baked bulk density (g / cm 3 )]]> 1.72 1.69 1.65 1.52 Cracking Shore hardness (HSD) 121.00 115.00 114.00 111.00 / Mass loss rate (%) 13.73 14.68 14.15 15.68 / Volume shrinkage rate (%) 36.99 36.41 35.02 31.53 / Open porosity (%) 4.30 5.37 6.54 9.36 /

[0046] 2. The performance of the graphite blocks SG-A and SG-B obtained from Example 1 and Example 2 was tested according to the test method of the national standard, and the basic performance parameters of the graphite blocks are shown in Table 2.

[0047] Table 2. Basic performance parameters of graphite blocks

[0048] Performance parameters SG-A SG-B Baked bulk density (g / cm 3 ) 1.72 1.69 Graphite bulk density (g / cm 3 )]]> 1.93 1.90 Shore hardness (HSD) 84.00 80.00 Open porosity (%) 1.08 2.63 Resistivity (μΩ-m) 19.44 23.23 Flexural strength (MPa) 144.00 126.89 Compressive strength (MPa) 259.45 240.95

[0049] As can be seen from Table 2, the calcined blocks SCB-A and SCB-B prepared by the combined action of homogeneous / heterogeneous volatile components and the action of homogeneous volatile components alone were graphitized once to obtain SG-A and SG-B, and the densities were 1.93 g / cm 3 and 1.90 g / cm 3, the Shore hardness is 84HS and 80HS, the open porosity is 1.08% and 2.63%, the bending strength is up to 144.00MPa and 126.89MPa, the compressive strength is up to 259.45MPa and 240.95MPa, the resistivity is 19.44μΩ.m and 23.23. It is embodied that the homogenous / heterogeneous volatile components together are more beneficial to the densification and enhancement of the graphite material, and the performances are superior to most of the domestic and imported graphite materials.

[0050] 3. The actual photos of the carbon graphite material sintered block prepared in Example 1 and Comparative Example 3 are shown in Figure 1 . Figure 1 (a) is the optical photo of the sintered block SCB-E prepared in Comparative Example 3, Figure 1 (b) is the optical photo of the carbon graphite material sintered product SCB-A prepared in Example 1.

[0051] It can be obviously seen that the sintered block SCB-E sintered in the open environment appears obvious cracks, while the sintered block SCB-A sintered in the closed environment with the self-pressurization of the homogenous and heterogeneous volatile components does not appear the cracking phenomenon, which indicates that the method of using the volatile component gas as the pressurized sintering can effectively prevent the cracking of the carbon block.

[0052] 4. The bending and compressive stress-strain curves of the graphite block prepared in Example 1 are shown in Figure 2 , wherein Figure 2 (a) is the bending stress-strain curve, Figure 2 (b) is the compressive stress-strain curve. It can be clearly seen that the SG-A has extremely excellent mechanical properties.

[0053] 5. The surface morphology and backscattering photos of the graphite block SG-A prepared in Example 1 are shown in Figure 3 , wherein, Figure 3 (a) and Figure 3 (b) are respectively the SEM photo and the corresponding backscattering SEM photo of the surface of SG-A under the magnification of x2000; Figure 3 (c) and Figure 3 (d) are respectively the SEM photo and the corresponding backscattering SEM photo of the surface of SG-A under the magnification of x200.

[0054] It can be seen from the photos that: the surface of SG-A has only a few very small pores, and only under the magnification of 2000, it can be seen that the SG-A has very dense structure. And under the backscattering SEM under the magnification of 200 and 2000, there is no bright spot, and the surface has no impurities, which indicates that the SG-A has very homogeneous structure.

[0055] 6. The cross-section morphology and backscattering photos of the graphite block SG-A prepared in Example 1 are shown in Figure 4As shown in the figure, Figure 4 (a) and Figure 4 (b) are SEM and backscattered SEM images of SG-A section, respectively; Figure 4 (c) and Figure 4 (d) are SEM and backscattered SEM images of SG-A section, respectively.

[0056] As can be seen from the figure: the section structure of SG-A is very smooth, which shows that there is no crack initiation and propagation inside, and no cracks and pores, which shows that the internal structure is also very homogeneous and dense.

[0057] The above descriptions can all show that the use of artificial volatile components can greatly improve the yield, density and mechanical properties of carbon graphite materials, reduce pores and internal defects, and reduce the preparation cycle, which is due to the advantages of self-sintering raw materials of green coke and the reasonable use of artificial volatile components. Promote the cross-linking of molecular chains between carbon particles, improve the chemical properties of volatile components, improve the bonding ability between particles, reduce mass loss, increase volume shrinkage, reduce porosity, thereby realizing the short process preparation of high-density and high-strength graphite materials.

[0058] Finally, it should be noted that the above embodiments of the present application are only examples for illustrating the present application, and are not a limitation on the embodiments of the present application. For those skilled in the art, on the basis of the above description, other different forms of changes and variations can also be made. Here, all the embodiments cannot be exhausted. Any obvious changes or variations derived from the technical solutions of the present application still fall within the protection scope of the present application.

Claims

1. A short-process preparation method for high-density, high-strength carbon-graphite materials, characterized in that, Carbonaceous raw materials are pressed into green bodies, which are then placed in a sealed container for calcination. Finally, graphitization is performed to obtain the high-density, high-strength carbon-graphite material. The carbonaceous raw materials are raw coke powder or mesophase carbon microspheres. The calcination material used during calcination contains heterogeneous volatiles and carbonaceous raw materials of the same nature as the green bodies. The heterogeneous volatilization is classified into one or more of the following: oil-based, organic-based, and inorganic-based systems that can generate gas at 20-200℃; wherein the oil-based system includes coal tar and anthracene oil; the organic-based system includes toluene and quinoline; and the inorganic-based system includes water and ethanol.

2. The short-process preparation method for high-density, high-strength carbon-graphite material according to claim 1, characterized in that, The raw coke powder is raw petroleum coke or raw pitch coke, and the D50 of the raw coke powder is 0.1~5 μm, while the D50 of the mesophase carbon microspheres is 0.1~10 μm.

3. The short-process preparation method for high-density, high-strength carbon-graphite material according to claim 1, characterized in that, The mass ratio of carbonaceous raw materials and heterogeneous volatiles mixed in the burial material is 1:4 to 4:

1.

4. A short-process preparation method for high-density, high-strength carbon-graphite materials according to claim 1 or 3, characterized in that, The mass of carbonaceous raw materials and heterogeneous volatiles in the burial feed accounts for 10-20% of the total mass of the burial feed.

5. The short-process preparation method for high-density, high-strength carbon-graphite material according to claim 1, characterized in that, The specific steps of compression molding are as follows: carbonaceous aggregate is pre-molded by pressing it with a pressure of 1~5 MPa for 10~30 s on a flat vulcanizing machine, and then pressed with a pressure of 150~250 MPa for 5~10 min by a cooling press, and then left to stand for 10~20 h to obtain green body.

6. The short-process preparation method for high-density, high-strength carbon-graphite material according to claim 1, characterized in that, The specific roasting method is as follows: under the protection of inert gas, the temperature is raised to 1000~1200 ℃ at a heating rate of 0.1~4 ℃ / min and held for 2~6 h, then cooled to below 200 ℃ at a cooling rate of 0.1~0.5 ℃ / min, and then naturally cooled to room temperature.

7. The short-process preparation method for high-density, high-strength carbon-graphite material according to claim 1, characterized in that, The specific steps of graphitization are as follows: under the protection of inert gas, the temperature is raised to 2400~2800℃ at a heating rate of 0.3~0.7℃ / min, held for 1 h, and then cooled to below 200℃ at a cooling rate of 0.3~0.7℃ / min, followed by natural cooling to room temperature.

8. A high-density, high-strength carbon-graphite material, characterized in that, It is prepared using the short-process preparation method of any one of claims 1 to 7 for high-density, high-strength carbon graphite material.

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