CN117164359A - Method for preparing carbon graphite material by in-situ densification - Google Patents
Method for preparing carbon graphite material by in-situ densification Download PDFInfo
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- CN117164359A CN117164359A CN202310813079.9A CN202310813079A CN117164359A CN 117164359 A CN117164359 A CN 117164359A CN 202310813079 A CN202310813079 A CN 202310813079A CN 117164359 A CN117164359 A CN 117164359A
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 129
- 239000007770 graphite material Substances 0.000 title claims abstract description 91
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 90
- 238000000034 method Methods 0.000 title claims abstract description 90
- 238000011065 in-situ storage Methods 0.000 title claims abstract description 62
- 238000000280 densification Methods 0.000 title claims abstract description 53
- 239000002994 raw material Substances 0.000 claims abstract description 16
- 238000011282 treatment Methods 0.000 claims abstract description 13
- 238000003825 pressing Methods 0.000 claims abstract description 3
- 230000008569 process Effects 0.000 claims description 41
- 239000010439 graphite Substances 0.000 claims description 22
- 229910002804 graphite Inorganic materials 0.000 claims description 22
- 238000010438 heat treatment Methods 0.000 claims description 21
- 239000000463 material Substances 0.000 claims description 18
- 239000002245 particle Substances 0.000 claims description 16
- 239000000843 powder Substances 0.000 claims description 14
- 239000011230 binding agent Substances 0.000 claims description 11
- 238000004898 kneading Methods 0.000 claims description 11
- 238000000465 moulding Methods 0.000 claims description 10
- 239000010426 asphalt Substances 0.000 claims description 8
- 239000011331 needle coke Substances 0.000 claims description 7
- 238000000462 isostatic pressing Methods 0.000 claims description 6
- 239000006253 pitch coke Substances 0.000 claims description 4
- RHZUVFJBSILHOK-UHFFFAOYSA-N anthracen-1-ylmethanolate Chemical compound C1=CC=C2C=C3C(C[O-])=CC=CC3=CC2=C1 RHZUVFJBSILHOK-UHFFFAOYSA-N 0.000 claims description 3
- 239000003830 anthracite Substances 0.000 claims description 3
- 239000002008 calcined petroleum coke Substances 0.000 claims description 3
- 239000006229 carbon black Substances 0.000 claims description 3
- 239000003610 charcoal Substances 0.000 claims description 3
- 239000000203 mixture Substances 0.000 claims description 3
- 238000001354 calcination Methods 0.000 claims description 2
- 239000011261 inert gas Substances 0.000 claims description 2
- 239000002006 petroleum coke Substances 0.000 claims description 2
- 238000012545 processing Methods 0.000 claims description 2
- 230000003068 static effect Effects 0.000 claims description 2
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- 230000000052 comparative effect Effects 0.000 description 36
- 238000001816 cooling Methods 0.000 description 25
- 238000001878 scanning electron micrograph Methods 0.000 description 24
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 16
- 238000005245 sintering Methods 0.000 description 14
- 238000010304 firing Methods 0.000 description 13
- 238000006243 chemical reaction Methods 0.000 description 12
- 238000011049 filling Methods 0.000 description 9
- 229910052786 argon Inorganic materials 0.000 description 8
- 238000006116 polymerization reaction Methods 0.000 description 7
- 238000012360 testing method Methods 0.000 description 7
- 239000002010 green coke Substances 0.000 description 6
- 238000006068 polycondensation reaction Methods 0.000 description 6
- 239000000571 coke Substances 0.000 description 5
- 150000001875 compounds Chemical class 0.000 description 4
- 238000005336 cracking Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 238000002360 preparation method Methods 0.000 description 4
- 238000012876 topography Methods 0.000 description 4
- 239000003039 volatile agent Substances 0.000 description 4
- 230000002968 anti-fracture Effects 0.000 description 3
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- 230000007423 decrease Effects 0.000 description 3
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- 238000004519 manufacturing process Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- MWPLVEDNUUSJAV-UHFFFAOYSA-N anthracene Chemical compound C1=CC=CC2=CC3=CC=CC=C3C=C21 MWPLVEDNUUSJAV-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
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- 239000011280 coal tar Substances 0.000 description 1
- 239000011294 coal tar pitch Substances 0.000 description 1
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- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
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Abstract
The invention discloses a method for preparing a carbon graphite material by in-situ densification, which comprises the following steps: and pressing and forming the raw materials containing volatile matters for preparing the carbon graphite material to obtain a green body, then placing the green body in a closed container for roasting treatment, volatilizing the volatile matters of the raw materials and raising the internal pressure of the closed container, and obtaining the carbon graphite material after the roasting treatment is finished. The method for preparing the high-performance carbon graphite material by in-situ densification can effectively reduce useless volatile matters and convert part of the useless volatile matters into beneficial volatile matters, and the prepared carbon graphite material has higher density and excellent mechanical property.
Description
Technical Field
The invention belongs to the field of carbon materials, and particularly relates to a preparation method of a carbon graphite material.
Background
The carbon material is also called as carbon material and comprises a material produced by taking carbon and graphite as raw materials. The carbon graphite material has the characteristics of high temperature resistance, high conductivity, low density, high strength, corrosion resistance, self lubrication, excellent electronic performance and the like, attracts great attention in various industries of the world, is widely applied to the industries of nuclear power, automobiles, aerospace, metallurgy, chemical industry, machinery, medical treatment, electronics and the like, becomes an indispensable nonmetallic material in the modern industrial technology, has a name of black gold, is recognized as one of new materials with the most development potential in the 21 st century, and has important significance for the development of science and technology in China and the development of national economy.
The preparation of the carbon graphite material generally comprises a traditional process and a self-sintering process, wherein the traditional process adopts calcined petroleum coke, pitch coke, graphite, carbon black, anthracite, metallurgical carbon, charcoal and the like as solid raw materials, adopts coal pitch, coal tar, anthracene oil, resin and the like as binders, and prepares the carbon graphite material through the processes of proportioning, kneading, forming, roasting, graphitizing and the like. In order to achieve a density and performance that can meet practical applications, repeated impregnation and firing are also required to be performed a plurality of times, which inevitably results in an increase in production cost and an increase in production time. More spacious cakes are formed by the fact that a large amount of useless volatile matters in the binder can generate larger thermal stress, so that interface phase separation and poor binding force between aggregate and the binder are caused, and most carbon graphite materials often show poor performance. The other type of self-sintering process uses raw materials with the bonding function, and only proper forming raw materials are needed to be selected, and a bonding agent is not needed, so that the processes of mixing and kneading and repeated dipping/roasting are omitted, and the production period and the cost are obviously reduced. However, the raw materials used in the self-sintering process often have too high volatile content (10% -20%), and large volume shrinkage, so that further ordered rearrangement of the molecular structure is disturbed to a certain extent, the block is easy to crack and even crack, and the yield and mechanical property of the product are greatly reduced.
Therefore, whether the carbon graphite material is prepared by a traditional process or a self-sintering process, reasonable volatile components are key to preparing the high-performance carbon graphite material, because a part of the beneficial volatile components are used as bonding components to form a bonding network in the heat treatment process so that particles are tightly connected together, and therefore, the carbon graphite material has certain mechanical strength. The other part of useless volatile components is caused by chain breakage and polycondensation of a large number of polymer chains on the surface of the particlesIsochemical reaction to release a large amount of H 2 O、CO、CO 2 、H 2 、CH 4 And (3) generating a large number of air holes and microcracks in the material, wherein the air holes and microcracks have an influence on the performance of a product and even cause cracking of the product.
At present, the method for removing useless volatile matters mainly comprises solvent pretreatment (such as patent CN 113387701A), oxidation heat treatment and other methods, but the methods have the realistic problems of complicated preparation flow, difficult industrialization and the like. Thus, how to reduce unwanted volatiles and even partially convert them into beneficial volatiles to remain within the article, promote in situ welding between particles, increase volume shrinkage while reducing mass loss, and thus achieve in situ densification presents a great challenge in preparing high performance carbon graphite materials.
Disclosure of Invention
The invention aims to overcome the defects and the shortcomings in the background art, and provides a method for preparing a carbon graphite material by in-situ densification, which can effectively reduce useless volatile matters and convert part of the useless volatile matters into beneficial volatile matters, and the prepared carbon graphite material has higher density and excellent mechanical property. In order to solve the technical problems, the technical scheme provided by the invention is as follows:
a method for preparing a carbon graphite material by in-situ densification comprises the following steps: and pressing and forming the raw materials containing volatile matters for preparing the carbon graphite material to obtain a green body, then placing the green body in a closed container for roasting treatment, volatilizing the volatile matters of the raw materials and raising the internal pressure of the closed container, and obtaining the carbon graphite material after the roasting treatment is finished.
In the invention, the atmosphere inside the closed container is not required to be controlled, and the air is adopted, so that other treatments such as vacuumizing or nitrogen filling and pressurizing are not required.
In the above method for preparing carbon graphite material by in-situ densification, preferably, the raw material comprises raw coke powder, wherein the raw coke powder comprises one or more of raw petroleum coke, raw pitch coke, raw needle coke and mesophase carbon microspheres; the particle size D50 of the raw coke powder is 1-20 mu m, and the mass content of volatile matters of the raw coke powder is 10-20%.
In the method for preparing the carbon graphite material by in-situ densification, preferably, the raw materials comprise pressed powder, wherein the pressed powder is powder obtained by processing the aggregate and the binder through the processes including batching, kneading, forming and crushing; the particle diameter D50 of the pressed powder is 1-20 mu m, and the mass content of volatile matters of the pressed powder is 10-20%.
In the above method for preparing carbon graphite material by in-situ densification, preferably, the aggregate comprises one or more of calcined petroleum coke, asphalt coke, graphite, carbon black, anthracite, metallurgical carbon and charcoal; the binder comprises medium temperature asphalt or high temperature asphalt.
In the above method for preparing a carbon graphite material by in-situ densification, preferably, the closed container is a cylindrical container made of graphite, in which a burn-in material is filled, and other spaces after placing the green body are filled with the burn-in material. The buried firing material can be prepared by adopting the existing conventional products, such as a mixture of river sand and metallurgical coke.
In the above method for preparing carbon graphite material by in-situ densification, preferably, the pressure in the closed container is 0.1-5MPa. The invention utilizes the volatile components of the green body itself as a source of in-situ densification for increasing the pressure within the closed vessel.
In the above method for preparing carbon graphite material by in-situ densification, preferably, the press forming includes pre-molding and isostatic pressing, wherein the pre-molding is performed on a press vulcanizer, the isostatic pressing is performed through a cold isostatic press, and then the green compact is obtained by slowly releasing pressure.
In the method for preparing the carbon graphite material by in-situ densification, preferably, the pre-molding is carried out on a flat vulcanizing machine by using the pressure of 1-5MPa for 10-30s, then the pre-molding is carried out on the raw material by using a cold static press under the pressure of 150-250MPa for 5-10min, and then the green body is obtained by slowly releasing pressure.
In the method for preparing the carbon graphite material by in-situ densification, preferably, the roasting treatment is to heat the carbon graphite material to 1050 ℃ for 2-6 hours at a heating rate of 0.1-4 ℃/min under the protection of inert gas, and then slowly cooling the carbon graphite material to room temperature.
The technical principle of the invention is as follows: green body inIn the roasting process, a large number of macromolecular chains have chemical reactions such as chain breakage, polycondensation and the like, and a large number of H is released 2 O、CO、CO 2 、H 2 、CH 4 The method for preparing the carbon graphite material by in-situ densification of the invention can enable a part of useless volatile matters escaping during heat treatment to be filled in a limited space (namely, the inside of a closed container) as a source of external pressure increase, and simultaneously, the process is accompanied with the expansion of the volume of a green body, so that the internal pressure of the container is increased due to multiple reasons. According to the lux principle, in a reversible reaction in which a gas participates or is generated, when the pressure is increased, the equilibrium always moves in the direction in which the pressure decreases. Thus, the green body starts to reach an equilibrium state (decrease in ambient pressure) toward the volume decrease direction, and at the same time, the reaction that originally decomposed also moves toward the polymerization direction (depressurization of polymerization energy). Specifically, the green body can undergo significant volume expansion at 200-600 ℃, and the green body is in a softened plastic state during the process, wherein the process mainly comprises the steps of carrying out severe thermal decomposition and polymerization reaction on the binder, namely, the green body generates low-molecular compounds through high-temperature cracking, polycondensation and other reactions to generate CO 2 、H 2 O, CO, light oil, etc., which causes an increase in the external ambient pressure. The low molecular compound decomposed from the binder is in a liquid state due to the large vapor pressure, so that tiny pores and tiny cracks are further permeated, free radicals are generated by the breakage of unstable chemical bonds, dehydrogenation and polycondensation are synchronously carried out, and then the polymerization is synchronously carried out, so that the blank is further densified, the mass loss is reduced, and meanwhile, the volume shrinkage is increased, namely, the conversion of the useless volatile matters into beneficial volatile matters is realized. Thus, 100% of the volatile components can play a role, thereby playing a role in-situ densification. The conventional self-sintering process or the conventional process cannot exert a pressurizing effect in the stage (200-600 ℃) of the mass generation of volatile matters, the volatile matters directly escape, the external environment of the block is basically at normal pressure, the escape process of the low-molecular compound is accompanied with the expansion of pores and micro cracks, and the internal stress of the block is larger than the external environment pressure at the moment, so that the product is finally cracked or even cracked.
The method for preparing the carbon graphite material by in-situ densification does not need vacuumizing and aims at protectingLeaving a part of air (filled between the buried firing particles or adsorbed on the surface of the buried firing material) to pre-oxidize the green body at an early temperature of 400 ℃ to increase the coke precipitation amount, and a small amount of CO in the air 2 、CO、H 2 O and the like can be regarded as small-molecule volatile matters to promote the progress of polycondensation and polymerization. In addition, the method for preparing the carbon graphite material by in-situ densification does not carry out pressure relief operation in the preparation process, and the pressure in the container is increased by utilizing volatile matters such as low-molecular compounds and the like, so that the polycondensation and polymerization reaction are promoted. The temperature interval of the volatile matters escaping in a large quantity in the roasting process is 200-600 ℃, which is the stage of the product reacting in a large quantity, at this time, the air pressure in the closed container can be more than 2.5MPa (for example, the decomposition reaction and the polymerization reaction of coal tar pitch are carried out at 300-450 ℃ and reach balance simultaneously), and the balance is reached under a certain temperature and pressure, if the pressure relief operation is carried out, the reaction balance is offset, so that a part of gas is further decomposed out by the green body, the subsequent pressure increase is difficult to restore to the reaction balance, and the in-situ densification effect emphasized by the invention is difficult to realize better.
The method for preparing the high-performance carbon graphite material by in-situ densification can effectively reduce useless volatile matters and convert part of the useless volatile matters into beneficial volatile matters, and the prepared carbon graphite material has higher density and excellent mechanical property. More importantly, the method has universality and is also suitable for preparing baked products from other carbon graphite materials.
Compared with the prior art, the invention has the advantages that:
1. the method for preparing the high-performance carbon graphite material by in-situ densification only needs to put the green body in a closed container and bake the green body, the pressure in the closed container is increased by utilizing volatile matters, no additional treatment is needed, and the method is simple, convenient and efficient.
2. According to the method for preparing the high-performance carbon graphite material by in-situ densification, a part of useless volatile matters are converted into beneficial volatile matters, so that the sample mass loss is reduced, the volume shrinkage of the sample is increased, the product performance is improved, the sample is not cracked, the yield can reach 100%, and the densification effect is good.
3. The method for preparing the high-performance carbon graphite material by in-situ densification can ensure that a block product does not crack when the volume of the block product is shrunk more, and the block product has higher density and better mechanical property.
4. The method for preparing the high-performance carbon graphite material by in-situ densification is not only useful for preparing the carbon graphite material by a self-sintering process of raw coke, mesocarbon microbeads and the like, but also plays the same role in promoting the traditional processes of kneading, forming, roasting and the like of aggregate/binder.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a physical diagram of the carbon graphite materials prepared in example 1, comparative example 1, example 2 and example 3; wherein, (a) is a front view of an in-situ densified graphite material baked product ZM-12SJ prepared in example 1, and (b) is a front view of a graphite material baked product 12SJ prepared in comparative example 1; (c) The front view of the in-situ densified graphite material calcined product ZM-12SJ-1 obtained in example 2, and the front view of the calcined product ZM-12SJ-5 obtained in example 3.
FIG. 2 is a physical diagram of the carbon graphite materials prepared in example 4, comparative example 2, example 5 and comparative example 3; wherein, (a) is a front view of an in-situ densified graphite material baked product ZM-6SJ prepared in example 4, and (b) is a front view of a graphite material baked product 6SJ prepared in comparative example 2; (c) The front view of the in-situ densified graphite material baked ZM-ZZJ prepared in example 5, and the front view of the carbon graphite material baked ZZJ prepared in comparative example 3.
FIG. 3 is a graph showing the flexural and compressive curves of the baked blocks prepared in examples 1 to 5 and comparative examples 1 to 3, wherein (a) and (d) are a graph showing the flexural and compressive curves of ZM-12SJ and 12SJ prepared in example 1 and comparative example 1, respectively. (b) And (e) are a flex-line resistance comparison chart and a compression-curve resistance comparison chart of ZM-6SJ and 6SJ prepared in example 4 and comparative example 2, respectively. (c) And (f) are a flex-line resistance comparison chart and a compression-curve resistance comparison chart of ZM-ZZJ and ZZJ obtained in example 5 and comparative example 3, respectively.
FIG. 4 is a surface topography of the calcined product obtained in example 1 and comparative example 1, wherein (a 1) and (a 2) are SEM images of ZM-12SJ obtained in example 1 and corresponding back-scattered SEM images thereof, respectively; (b1) (b 2) are respectively an SEM image of 12SJ obtained in comparative example 1 and a corresponding back-scattered SEM image.
FIG. 5 is a surface topography of the calcined product obtained in example 4 and comparative example 2, wherein (a 1) and (a 2) are SEM images of ZM-6SJ obtained in example 4 and corresponding back-scattered SEM images, respectively; (b1) (b 2) are respectively an SEM image of 6SJ obtained in comparative example 2 and a corresponding back-scattered SEM image.
FIG. 6 is a surface topography of the calcined product obtained in example 5 and comparative example 3, wherein (a 1) and (a 2) are SEM images of ZM-ZZJ obtained in example 5 and corresponding back-scattered SEM images thereof, respectively; (b1) (b 2) are SEM images of ZZJ obtained in comparative example 3 and corresponding back-scattered SEM images, respectively.
FIG. 7 is a graph showing the fracture-resistant morphology of the calcined product obtained in example 1 and comparative example 1, wherein (a 1) and (a 2) are respectively an SEM image of the fracture-resistant surface of ZM-12SJ obtained in example 1 and a corresponding back-scattered SEM image; (b1) (b 2) are respectively an anti-fracture SEM image of 12SJ obtained in comparative example 1 and a corresponding back-scattering SEM image.
FIG. 8 is a graph showing the fracture-resistant morphology of the calcined product obtained in example 4 and comparative example 2, wherein (a 1) and (a 2) are respectively an SEM image of the fracture-resistant surface of ZM-6SJ obtained in example 4 and a corresponding back-scattered SEM image; (b1) (b 2) are respectively an anti-fracture SEM image of 6SJ obtained in comparative example 2 and a corresponding back-scattering SEM image.
FIG. 9 is a graph showing the fracture-resistant morphology of the calcined product obtained in example 5 and comparative example 3, wherein (a 1) and (a 2) are respectively an SEM image of the fracture-resistant surface of ZM-ZZJ obtained in example 5 and a corresponding back-scattered SEM image; (b1) (b 2) are respectively an anti-fracture SEM image of the zzzj obtained in comparative example 3 and a corresponding back-scattering SEM image.
Detailed Description
The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments are shown, for the purpose of illustrating the invention, but the scope of the invention is not limited to the specific embodiments shown.
Unless defined otherwise, all technical and scientific terms used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the scope of the present invention.
Unless otherwise specifically indicated, the various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or may be prepared by existing methods.
Example 1:
a method for preparing a high-performance carbon graphite material by in-situ densification adopts a self-sintering mode to obtain the carbon graphite material by sintering in a roasting process, and comprises the following steps:
(1) The green coke powder having a particle size of 12 μm (D50 of about 11.50 μm) was molded under a press at a pressure of 3MPa and then isostatic pressed at 200MPa for 10min. And (5) standing for more than 12 hours to obtain a green body.
(2) Placing the green body obtained in the step (1) in a graphite cylindrical container with a limited space which does not allow volatile matters to escape, and filling the rest with a buried firing material (mixture of river sand and metallurgical coke, the same applies below).
(3) Placing the graphite cylindrical container in the step (2) in a thermal field, heating to 1050 ℃ at a heating rate of 0.2 ℃/min under the protection of argon, preserving heat for 4 hours, cooling to below 200 ℃ at a cooling rate of 0.2 ℃/min, and naturally cooling to room temperature to obtain an in-situ densified carbon graphite material baked product which is named ZM-12SJ.
Comparative example 1:
a method of carbon graphite material comprising the steps of:
(1) The green coke powder having a particle size of 12 μm (D50 of about 11.50 μm) was molded under a press at a pressure of 3MPa and then isostatic pressed at 200MPa for 10min. And (5) standing for more than 12 hours to obtain a green body.
(2) Placing the green body obtained in the step (1) into a graphite cylindrical container with an open space in which volatile matters can be diffused randomly, and filling the rest part with a buried firing material.
(3) And (3) placing the graphite cylindrical container in the step (2) in a thermal field, heating to 1050 ℃ at a heating rate of 0.2 ℃/min under the protection of argon, preserving heat for 4 hours, cooling to below 200 ℃ at a cooling rate of 0.2 ℃/min, and naturally cooling to room temperature to obtain a carbon graphite material baked product which is named as 12SJ.
Example 2:
a method for preparing a high-performance carbon graphite material by in-situ densification adopts a self-sintering mode to obtain the carbon graphite material by sintering in a roasting process, and comprises the following steps:
(1) The green coke powder having a particle size of 12 μm (D50 of about 11.50 μm) was molded under a press at a pressure of 1MPa and then isostatic pressure of 200MPa for 10min. And (5) standing for more than 12 hours to obtain a green body.
(2) Placing the green body obtained in the step (1) in a graphite cylindrical container with a limited space which does not allow volatile components to escape, and filling the rest part with a burn-in material.
(3) Placing the graphite cylindrical container in the step (2) in a thermal field, heating to 1050 ℃ at a heating rate of 0.2 ℃/min under the protection of argon, preserving heat for 4 hours, cooling to below 200 ℃ at a cooling rate of 0.2 ℃/min, and naturally cooling to room temperature to obtain an in-situ densified carbon graphite material baked product which is named ZM-12SJ-1.
Example 3:
a method for preparing a high-performance carbon graphite material by in-situ densification adopts a self-sintering mode to obtain the carbon graphite material by sintering in a roasting process, and comprises the following steps:
(1) The green coke powder having a particle size of 12 μm (D50 of about 11.50 μm) was molded under a press at a pressure of 5MPa and then isostatic pressed at 200MPa for 10min. And (5) standing for more than 12 hours to obtain a green body.
(2) Placing the green body obtained in the step (1) in a graphite cylindrical container with a limited space which does not allow volatile components to escape, and filling the rest part with a burn-in material.
(3) Placing the graphite cylindrical container in the step (2) in a thermal field, heating to 1050 ℃ at a heating rate of 0.2 ℃/min under the protection of argon, preserving heat for 4 hours, cooling to below 200 ℃ at a cooling rate of 0.2 ℃/min, and naturally cooling to room temperature to obtain an in-situ densified carbon graphite material baked product which is named ZM-12SJ-5.
Example 4:
a method for preparing a high-performance carbon graphite material by in-situ densification adopts a self-sintering mode to obtain the carbon graphite material by sintering in a roasting process, and comprises the following steps:
(1) The green coke powder having a particle size of 6 μm (D50 of about 5.87 μm) was molded under a press at a pressure of 3MPa and then isostatic pressed at 200MPa for 10min. And (5) standing for more than 12 hours to obtain a green body.
(2) Placing the green body obtained in the step (1) in a graphite cylindrical container with a limited space which does not allow volatile components to escape, and filling the rest part with a burn-in material.
(3) Placing the graphite cylindrical container in the step (2) in a thermal field, heating to 1050 ℃ at a heating rate of 0.2 ℃/min under the protection of argon, preserving heat for 4 hours, cooling to below 200 ℃ at a cooling rate of 0.2 ℃/min, and naturally cooling to room temperature to obtain an in-situ densified carbon graphite material baked product which is named ZM-6SJ.
Comparative example 2:
a method of carbon graphite material comprising the steps of:
(1) The green coke powder having a particle size of 6 μm (D50 of about 5.87 μm) was molded under a press at a pressure of 3MPa and then isostatic pressed at 200MPa for 10min. And (5) standing for more than 12 hours to obtain a green body.
(2) Placing the green body obtained in the step (1) into a graphite cylindrical container with an open space in which volatile matters can be diffused randomly, and filling the rest part with a buried firing material.
(3) And (3) placing the graphite cylindrical container in the step (2) in a thermal field, heating to 1050 ℃ at a heating rate of 0.2 ℃/min under the protection of argon, preserving heat for 4 hours, cooling to below 200 ℃ at a cooling rate of 0.2 ℃/min, and naturally cooling to room temperature to obtain a carbon graphite material baked product, wherein the carbon graphite material baked product is named as 6SJ.
Example 5:
a method for preparing a high-performance carbon graphite material by in-situ densification adopts a traditional process mode to sinter the high-performance carbon graphite material in a roasting process, and comprises the following steps:
(1) 160g of needle coke powder with the particle size of 10 mu m (D50 is about 10.01 mu m) is weighed, placed in a kneading pot at room temperature for premixing to 200 ℃, poured into 80g and decocted to 190 ℃ for liquid asphalt (softening point 109 ℃). Closing the cover, kneading for 1h, and after kneading, performing sheet binding, crushing and grinding treatment to obtain needle coke pressed powder.
(2) And (3) molding the needle Jiao Yafen obtained in the step (1) under a press vulcanizer, wherein the pressure is 3MPa, and then isostatic pressing is carried out for 10min under 200 MPa. And (5) standing for more than 12 hours to obtain a green body.
(3) Placing the green body obtained in the step (2) in a graphite cylindrical container with a limited space which does not allow volatile components to escape, and filling the rest part with a burn-in material.
(4) And (3) placing the graphite cylindrical container in the step (3) in a thermal field, heating to 1050 ℃ at a heating rate of 0.1 ℃/min under the protection of argon, preserving heat for 4 hours, cooling to below 200 ℃ at a cooling rate of 0.1 ℃/min, and naturally cooling to room temperature to obtain an in-situ densified graphite material baked product, which is named ZM-ZZJ.
Comparative example 3:
a method of carbon graphite material comprising the steps of:
(1) 160g of needle coke powder with the particle size of 10 mu m (D50 is about 10.01 mu m) is weighed, placed in a kneading pot at room temperature for premixing to 200 ℃, poured into 80g and decocted to 190 ℃ for liquid asphalt (softening point 109 ℃). Closing the cover, kneading for 1h, and after kneading, performing sheet binding, crushing and grinding treatment to obtain needle coke pressed powder.
(2) And (3) molding the needle Jiao Yafen obtained in the step (1) under a press vulcanizer, wherein the pressure is 3MPa, and then isostatic pressing is carried out for 10min under 200 MPa. And (5) standing for more than 12 hours to obtain a green body.
(3) Placing the green body obtained in the step (2) into a graphite cylindrical container with an open space in which volatile matters can be diffused randomly, and filling the rest part with a buried firing material.
(4) And (3) placing the graphite cylindrical container in the step (3) in a thermal field, heating to 1050 ℃ at a heating rate of 0.1 ℃/min under the protection of argon, preserving heat for 4 hours, cooling to below 200 ℃ at a cooling rate of 0.1 ℃/min, and naturally cooling to room temperature to obtain a carbon graphite material baked product named ZZJ.
The above calcined product was measured for bulk density, shore hardness, resistivity, mass loss rate, volume shrinkage, and open porosity, and then a sample was prepared as a standard sample, and flexural strength and compressive strength were measured, and the test data are shown in tables 1 and 2 below. The test of each performance data adopts the following test standard: volumetric density testing: JB/T8133.14-2013; shore hardness test: JB/T8133.4-2013; resistivity test: GB/T24525-2009; flexural strength test: JB/T8133.7-2013; compressive strength test: JB/T8133.8-2013; open porosity test: GB/T24529-2009; the firing mass loss rate and the firing volume shrinkage rate are the mass/volume loss ratio of the sample after firing. Raw coke powder or pressed powder volatile components: GB/T212-2008, the conversion of volatiles is the percentage of the reduced mass loss to volatiles, as shown in tables 1, 2 below.
Table 1: basic performance parameters of the baked products of examples 1 to 3 and comparative example 1
Table 2: basic performance parameters of the baked products in examples 4 to 5 and comparative examples 2 to 3
| Performance parameters | ZM-6SJ | 6SJ | ZM-ZZJ | ZZJ |
| Green density (g/cm) 3 ) | 1.22 | 1.21 | 1.48 | 1.50 |
| Density after firing (g/cm) 3 ) | 1.59 | 1.39 | 1.42 | 1.22 |
| Rate of mass loss by calcination (%) | 13.93 | 14.39 | 8.04 | 10.11 |
| Raw coke powder or pressed powder volatile matter (%) | 14.90 | 14.90 | 11.22 | 11.22 |
| Volatile componentConversion (%) | 6.51 | 3.42 | 28.34 | 9.89 |
| Firing volume shrinkage (%) | 34.05 | 25.24 | 4.27 | -10.22 |
| Shore Hardness (HSD) | 95.5 | 74.67 | 79.2 | 58 |
| Open porosity (%) | 18.62 | 26.04 | 27.77 | 41.68 |
| Resistivity (mu omega m) | 57.65 | 68.02 | 60.26 | 96.96 |
| Compressive strength (MPa) | 171.64 | 59.73 | 136.21 | 65.71 |
| Flexural strength (MPa) | 67.26 | 21.49 | 49.82 | 25.52 |
As can be seen from tables 1 and 2, the above-mentioned carbon graphite material baked block prepared by the in-situ densification process has obvious performance advantages. Specifically, table 1 shows 4 kinds of baked blocks in which green compacts ZM-12SJ and 12SJ, which were also formed under a pressure of 3MPa, were produced with a density of up to 1.49g/cm in the baked product ZM-12SJ prepared by the in-situ densification process 3 The density of the roasted product prepared by the common method is only 1.34g/cm 3 The ZM-12SJ has a density increased by 0.15g/cm compared with 12SJ 3 The open porosity is reduced by 5.86%, the resistivity is reduced by 60.35 omega, the hardness is improved by 8.25HSD, the fracture and compression strength is respectively improved by 134.25% and 179.06%, the volatile conversion rate is improved by 9.88%, and the volume shrinkage rate is increased by 4.09%.
Table 2 shows 4 baked blocks in which ZM-6SJ and 6SJ are also formed at a pressure of 3MPa, the density of the baked product ZM-6SJ obtained by the in-situ densification process being up to 1.59g/cm 3 The density of the roasted product prepared by the common method is only 1.39g/cm 3 The ZM-6SJ has a density increased by 0.2g/cm compared with 6SJ 3 The open porosity is reduced by 7.42%, the resistivity is reduced by 10.37 omega, the hardness is improved by 20.83HSD, the fracture-resistant compressive strength is respectively improved by 212.98% and 187.36%, the volatile conversion rate is improved by 3.09%, and the volume shrinkage rate is increased by 8.81%.
ZM-ZZJ and ZZJ are prepared by adopting the traditional process of taking calcined needle coke as aggregate and asphalt as binder, and are also formed under the pressure of 3MPa, and the density of the roasted product ZM-ZZJ obtained by adopting the in-situ densification process can reach 1.42g/cm 3 The density of the roasted product prepared by the common method is only 1.22g/cm 3 The ZM-12SJ has a density increased by 0.2g/cm compared with 12SJ 3 The open porosity is reduced by 13.91%, the resistivity is reduced by 36.7 omega, the hardness is improved by 21.2HSD, and the fracture resistance and the compression resistance are improvedThe degree is respectively improved by 95.22 percent and 107.29 percent, the volatile conversion rate is improved by 18.45 percent, and the volume shrinkage rate is increased by 14.49 percent.
Fig. 1 is a front view showing the calcined sample of the carbon graphite material prepared in examples 1 to 3 and comparative example 1, and fig. 2 is a front view showing the calcined sample of the carbon graphite material prepared in examples 4 to 5 and comparative example 2 to 3, and it is apparent from the figure that the calcined sample of the carbon graphite material ZM-12SJ (a in fig. 1), ZM-6SJ (a in fig. 2) and ZM-ZZJ (c in fig. 2) prepared by the in-situ densification process has smaller lateral dimensions than the calcined sample of the carbon graphite material 12SJ (b in fig. 1), 6SJ (b in fig. 2) and ZZZJ (d in fig. 2) prepared by the general process because the in-situ densification process improves the density and thus the product performance by reducing the mass loss of the sample and improving the volume shrinkage of the sample. The carbon graphite material roasting products prepared by the general method have larger size (b in figure 1, b in figure 2 and d in figure 2), smaller shrinkage, obvious volume shrinkage non-uniformity, even cracking and other phenomena. The lower right corner of the block ZZJ shown in FIG. 2 d has a significant cracking phenomenon.
FIG. 3 is a graph showing the flexural and compressive resistances of the baked blocks prepared in examples 1-5 and comparative examples 1-3, and it can be clearly seen that the samples ZM-12SJ, ZM-6SJ and ZM-ZZJ prepared by the in-situ densification process have significant mechanical property advantages.
FIGS. 4, 5 and 6 show the surface topography of the calcined product of ZM-12SJ (a in FIG. 4) and 12SJ (b in FIG. 4), ZM-6SJ (a in FIG. 5) and 6SJ (b in FIG. 5), ZM-ZZJ (a in FIG. 6) and ZZJ (b in FIG. 6) prepared in example 1 and comparative example 1, example 4 and comparative example 2, example 5 and comparative example 3 (a in FIG. 4) 1 ，b 1 ) And the corresponding backscatter image (a 2 ，b 2 ). It is obvious that the ZM-12SJ, ZM-6SJ and ZM-ZZJ prepared by the in-situ densification process have a more compact structure than the 12SJ, 6SJ and ZZJ prepared by the general method, which proves that the in-situ densification process can promote the volume shrinkage of the roasted sample and increase the density of the roasted sample.
FIGS. 7, 8 and 9 show ZM-12SJ (a in FIG. 7) and 12SJ (b in FIG. 7), ZM-6SJ (a in FIG. 8) and ZM-12SJ (b in FIG. 7) prepared in example 1 and comparative example 1, example 4 and comparative example 2, example 5 and comparative example 36SJ (b in FIG. 8), ZM-ZZJ (a in FIG. 9) and ZZJ (b in FIG. 9) of the fracture-resistant profile (a) 1 ，b 1 ) And the corresponding backscatter image (a 2 ，b 2 ). It is evident that the sections of ZM-12SJ, ZM-6SJ, ZM-ZZJ prepared by the in-situ densification process have fewer crack defects than the sections of 12SJ, 6SJ, ZZZJ prepared by the general method, which proves that the excellent mechanical properties of the fired sample prepared by the in-situ densification process are attributed to its dense structure and fewer internal crack defects.
The above description can illustrate that the in-situ densification process can greatly improve the density and mechanical properties of the carbon graphite material. The method is mainly characterized in that the pressurizing effect caused by volatile matters escaping is fully utilized, the volume shrinkage of a sample is increased, meanwhile, the mass loss is reduced, the formation of a bonding network among particles is promoted, the formation of microcracks is inhibited, and the density and the strength of a product are greatly improved.
Claims (9)
1. The method for preparing the carbon graphite material by in-situ densification is characterized by comprising the following steps of: and pressing and forming the raw materials containing volatile matters for preparing the carbon graphite material to obtain a green body, then placing the green body in a closed container for roasting treatment, volatilizing the volatile matters of the raw materials and raising the internal pressure of the closed container, and obtaining the carbon graphite material after the roasting treatment is finished.
2. The method of preparing a carbon graphite material by in situ densification of claim 1, wherein the feedstock comprises raw coke powder comprising one or more of raw petroleum coke, raw pitch coke, raw needle coke, and mesophase carbon microbeads; the particle size D50 of the raw coke powder is 1-20 mu m, and the mass content of volatile matters of the raw coke powder is 10-20%.
3. The method for preparing the carbon graphite material by in-situ densification according to claim 1, wherein the raw materials comprise pressed powder, and the pressed powder is powder obtained by processing aggregate and binder through the processes including batching, kneading, forming and crushing; the particle diameter D50 of the pressed powder is 1-20 mu m, and the mass content of volatile matters of the pressed powder is 10-20%.
4. The method of preparing a carbon graphite material by in situ densification according to claim 3, wherein the aggregate comprises one or more of calcined petroleum coke, pitch coke, graphite, carbon black, anthracite, metallurgical carbon, and charcoal; the binder comprises medium temperature asphalt or high temperature asphalt.
5. The method for preparing carbon graphite material by in-situ densification according to claim 1, wherein the closed vessel is a cylindrical vessel made of graphite, filled with a burn-in material, and the other space after placing the green body is filled with the burn-in material.
6. The method for preparing a carbon graphite material by in-situ densification according to claim 1, wherein the pressure in the closed vessel is 0.1 to 5MPa.
7. The method for preparing a carbon graphite material by in-situ densification according to any one of claims 1 to 6, wherein the press forming comprises pre-molding and isostatic pressing, the pre-molding being performed on a press vulcanizer, the isostatic pressing being performed by a cold isostatic press, and then the green body being obtained by slow pressure relief.
8. The method for preparing a carbon graphite material by in-situ densification according to claim 7, wherein the pre-molding is performed by using a pressure of 1-5MPa on a flat vulcanizing machine for 10-30s, then the pre-molding is performed by using a cold static press for 5-10min under a pressure of 150-250MPa, and then the green body is obtained by slowly releasing the pressure.
9. The method for preparing carbon graphite material by in-situ densification according to any one of claims 1 to 6, wherein the calcination treatment is to raise the temperature to 900 to 1200 ℃ at a heating rate of 0.1 to 4 ℃/min under the protection of inert gas, keep the temperature for 2 to 6 hours, and then slowly cool the mixture to room temperature.
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