CN115353391A

CN115353391A - Method for preparing special graphite material by isostatic pressing graphite waste in short process

Info

Publication number: CN115353391A
Application number: CN202211085606.0A
Authority: CN
Inventors: 涂川俊; 刘平; 游睿智; 陈宜兴
Original assignee: Hunan University
Current assignee: Hunan University
Priority date: 2022-09-06
Filing date: 2022-09-06
Publication date: 2022-11-18
Anticipated expiration: 2042-09-06
Also published as: CN115353391B

Abstract

The invention discloses a method for preparing a special graphite material by isostatic pressing graphite waste in a short process, which comprises the following steps: pretreating the waste graphite powder to obtain graphite powder with the D50 of 3-10 mu m; putting graphite powder, a sulfur-containing cross-linking agent 1 and oleic acid 1 into a kneading pot, removing water, then melting a binder 1, adding the melted binder 1 into the kneading pot for kneading, carrying out flaking, crushing and grinding, carrying out compression molding, then carrying out pressurization and low-temperature carbonization treatment, and then carrying out crushing, grinding and sieving to obtain low-temperature carbonized powder A; putting the forged coke powder, the sulfur-containing cross-linking agent 2 and the oleic acid 2 into a kneading pot, removing water, heating, melting the binder 2, adding into the kneading pot, kneading, and obtaining low-temperature carbonized powder B according to the method; and finally, preparing the special graphite material by adopting the low-temperature carbonized powder A, the low-temperature carbonized powder B, the solvent pretreated raw coke powder and the high-carbon-residue modified asphalt. The method can effectively improve the added value and the use amount of the waste graphite powder, and the prepared graphite material has excellent breaking strength and compressive strength.

Description

Method for preparing special graphite material by isostatic pressing graphite waste in short process

Technical Field

The invention belongs to the technical field of graphite materials, and particularly relates to a method for preparing a special graphite material by isostatic pressing graphite waste in a short process.

Background

Isostatic pressing graphite is a new material developed in the last 60 years internationally. Because of excellent mechanical property, corrosion resistance, self-lubricating property and thermal conductivity, the isostatic pressing graphite is widely applied to the fields of semiconductors, photovoltaics, spaceflight, nuclear power, new energy automobiles and the like. In particular, it is mainly used for a graphite crucible for the production of single crystal silicon; rocket nozzles and sealing elements for aerospace; neutron moderator, reflector of a nuclear reactor; electrodes in the process of electric spark machining; a new energy automobile electronic water pump bearing and the like.

However, during the production of the graphite parts by using isostatic pressing graphite, a large amount of milling powder, fragments and leftover materials (collectively referred to as graphite waste powder) are generated, and account for about 30 to 50 wt.%. Moreover, the graphite waste powder has the characteristics of high graphitization degree, low strength, low edge carbon atom activity, few heteroatoms, smooth surface and the like, so that the high-performance graphite material is generally difficult to prepare by the traditional method. Therefore, under the large background of the strategic target of 'double carbon', the application of the waste graphite powder in different fields is actively researched, and the method has practical significance for environmental protection and full utilization of non-renewable resources.

At present, isostatic graphite processing enterprises purchase graphite blanks from isostatic graphite manufacturers at high price, and graphite waste powder generated in the processing process is only sold to relative manufacturers such as carburant, anode paste, carbon brush, carbon brick, graphite crucible and the like at low price. For this reason, manufacturers purchasing waste graphite powder usually only add a small amount of the waste graphite powder as a filler (about 5 to 10 wt.% of the aggregate) to properly reduce the cost and improve the manufacturability, thermal conductivity and the like of the product.

Therefore, how to further improve the added value and the usage amount of the waste graphite powder is still the research focus of the related carbon graphite enterprises.

Disclosure of Invention

In view of the above disadvantages of the prior art, the present invention aims to provide a short-flow method for preparing a special graphite material from isostatic pressing graphite waste, which can effectively improve the added value and the usage amount of graphite waste powder, and the prepared graphite material has excellent properties such as breaking strength and compressive strength.

The technical scheme of the invention is realized as follows:

a method for preparing a special graphite material by isostatic pressing graphite waste in a short process specifically comprises the following steps:

s1: pretreating the waste graphite powder to obtain graphite powder with the D50 of 3-10 mu m, wherein the waste graphite powder is leftover materials, fragments and milling powder of isostatic pressing graphite;

s2: preparing and weighing 30-40 parts of binder, 50-70 parts of graphite powder obtained in S1, 1-5 parts of sulfur-containing crosslinking agent and 1-5 parts of oleic acid;

s3: putting the graphite powder, the sulfur-containing cross-linking agent and oleic acid in the S2 into a kneading pot for premixing, heating to 155-185 ℃ after moisture is removed, melting the binder of the S2, adding the melted binder into the kneading pot for kneading, after the kneading is finished, rolling, crushing, grinding, pressing and forming, then carrying out pressurization low-temperature carbonization treatment, crushing, grinding and sieving to obtain low-temperature carbonized powder A;

s4: preparing and weighing 25 to 30 parts of binder, 50 to 80 parts of calcined coke powder, 1 to 5 parts of sulfur-containing crosslinking agent and 1 to 5 parts of oleic acid;

s5: putting the calcined coke powder, the sulfur-containing cross-linking agent and the oleic acid in the step S4 into a kneading pot, removing water, heating to 155-185 ℃, melting the binder in the step S4, adding the melted binder into the kneading pot for kneading, after kneading, rolling, crushing, grinding, pressing and forming, then pressurizing for low-temperature carbonization treatment, crushing, grinding and sieving to obtain low-temperature carbonized powder B;

s6: 10-20 parts of high-carbon-residue modified asphalt with accurate weight, 60-70 parts of low-temperature carbonized powder A in S3, 10-20 parts of low-temperature carbonized powder B in S5 and 1-5 parts of solvent pretreated green coke powder;

s7: putting the low-temperature carbonized powder A, the low-temperature carbonized powder B and the solvent pretreated green coke powder in the step S6 into a kneading pot, removing water, heating to 170-200 ℃, melting the high-residual carbon modified asphalt in the step S6, adding the melted asphalt into the kneading pot for kneading, and obtaining pressed powder after flaking, crushing and grinding;

s8: will be provided withS7, pressing the obtained pressed powder into a powder with the density of 1.1 to 1.3 g/cm ³ Placing the block in a vacuum packaging bag for a period of time, and then placing the block in cold static pressure equipment for cold static pressure pressing for 1 to 3 times to obtain the block with the density of 1.63 to 1.66 g/cm ³ Green compact blocks of (a);

s9: placing the green body block in a stainless steel crucible, filling the green body block with an embedding material, placing the green body block in a roasting furnace, applying pressure, introducing nitrogen or argon in the process of pressurized roasting, roasting at 800 to 1200 ℃ for 2 to 6 hours, reducing the temperature to 200 to 300 ℃ under program control, and naturally cooling to room temperature to obtain the product with the density of 1.68 to 1.74 g/cm ³ The fired block of (2);

s10: placing the baked block in a vacuum graphitization furnace for atmosphere protection, processing at 2400-2800 ℃ for 1-4 h, performing program control, cooling to 200-300 ℃, and naturally cooling to room temperature to obtain the product with the volume density of 1.81-1.85 g/cm ³ The special graphite material of (3).

Further, in the step S1, metal impurities in the waste graphite powder are removed by using magnetic separation equipment, and the waste graphite powder is sieved and classified, then the waste graphite powder is subjected to primary grinding by using a 3R Raymond mill, and then fine grinding is performed by using an airflow mill, so that the graphite powder with the D50 of 3-10 mu m is obtained.

Further, the binder is low-temperature pitch, modified pitch, medium-temperature pitch or high-temperature pitch with low quinoline insoluble content, and one or more of anthracene oil, coal tar and ethylene tar.

Further, the sulfur-containing crosslinking agent is one or more of dodecyl mercaptan, tetramethyl thiuram disulfide, dithiodimorpholine, an alkylphenol polysulfide methylol resin, an alkylphenol sulfide, or an alkylphenol polysulfide.

Further, the specific steps of S3 are:

s3.1: putting the graphite powder, the sulfur-containing cross-linking agent and oleic acid into a kneading pot, mixing for 1 to 2 hours at 110 to 120 ℃, removing water, and rotating the kneading pot at a speed of 10 to 50 r/min in a forward rotation manner;

s3.2: after the water is removed, heating to 155-185 ℃, adding the binder in the S2 into a kneading pot after the binder is melted, kneading for 1-2 hours to obtain paste, wherein the rotation speed of the kneading pot is 10-50 r/min, the forward rotation and the reverse rotation are alternately carried out, and the cover is intermittently opened and closed for mixing;

s3.3: after kneading is finished, quickly transferring the paste to a material hopper of a sheet rolling machine, rolling for 2 to 3 times, wherein the thickness of the rolled sheet is 1 to 2 mm, the temperature of the rolled sheet corresponds to the kneading temperature, and the rotating speed is 10 to 30 r/min;

s3.4: after the rolling is finished and the temperature is cooled to room temperature, the mixture is placed for 2 to 10 hours, crushed and ground, and is sieved by a sieve with 100 to 320 meshes, and then placed for 2 to 10 hours to prepare pressed powder;

s3.5: and (2) performing compression molding on the prepared powder under the pressure of 10 to 20 MPa by a compression molding process, standing for 2 to 10 hours, placing the powder in an atmosphere resistance furnace, performing pressure coking treatment at 500 to 650 ℃ for 2 to 6 hours by program temperature control, cooling to room temperature along with the furnace, crushing and grinding the coked block, and sieving by a sieve of 100 to 200 meshes to prepare the low-temperature carbonized powder A.

Furthermore, the forged coke powder in S4 is one or two of calcined asphalt coke, petroleum coke and needle coke, and the D50 of the forged coke powder is 3-10 mu m.

Further, the specific step of S5 is:

s5.1: putting the calcined coke powder, the sulfur-containing cross-linking agent and oleic acid into a kneading pot, mixing for 1-2 h at 110-120 ℃, removing water, and rotating the kneading pot at a speed of 10-50 r/min in a forward direction;

s5.2: after the water is removed, heating to 155-185 ℃, adding the binder in the S4 into a kneading pot after the binder is melted, kneading for 1-2 hours to obtain paste, wherein the rotation speed of the kneading pot is 10-50 r/min, the forward rotation and the reverse rotation are alternately carried out, and the cover is intermittently opened and closed for mixing;

s5.3: after kneading is finished, quickly transferring the paste to a material hopper of a sheet rolling machine, rolling for 2 to 3 times, wherein the thickness of the rolled sheet is 1 to 2 mm, the temperature of the rolled sheet corresponds to the kneading temperature, and the rotating speed is 10 to 30 r/min;

s5.4: after the rolling is finished and the temperature is cooled to room temperature, the mixture is placed for 2 to 10 hours, crushed and ground, and is sieved by a sieve with 100 to 320 meshes, and then placed for 2 to 10 hours to prepare pressed powder;

s5.5: and (2) performing compression molding on the prepared powder under the pressure of 10 to 30 MPa by a compression molding process, standing for 2 to 10 hours, placing the powder in an atmosphere resistance furnace, performing pressure coking treatment at the temperature of 300 to 600 ℃ for 2 to 6 hours by program temperature control, cooling to room temperature along with the furnace, crushing and grinding the coked block, and sieving by a sieve of 100 to 200 meshes to prepare the low-temperature carbonized powder B.

Further, the solvent in S6 is used for pretreating the raw coke powder to obtain one or more of raw petroleum coke, raw asphalt coke, raw needle coke or raw mesocarbon microbeads.

Further, the specific steps of S7 are:

s7.1: putting the low-temperature carbonized powder A, the low-temperature carbonized powder B and the solvent pretreated green coke powder into a kneading pot, mixing for 1 to 2 hours at 110 to 120 ℃, removing water, and rotating the kneading pot at a rotating speed of 10 to 50 r/min in a forward rotation manner;

s7.2: after the water is removed, heating to 240-300 ℃, melting the high carbon residue modified asphalt in S6, adding the melted asphalt into a kneading pot, kneading for 1-2 h at the rotation speed of 10-50 r/min, alternately performing forward rotation and reverse rotation, and intermittently opening and closing a cover for mixing;

s7.3: and after kneading is finished, quickly transferring the mixture to a material hopper of a sheet mill, rolling for 1 to 2 times, wherein the thickness of the rolled sheet is 1 to 4 mm, the temperature of the rolled sheet corresponds to the kneading temperature, the rotating speed is 10 to 30 r/min, cooling by program temperature control after the sheet rolling is finished, cooling to room temperature, standing for 2 to 10 hours, crushing and grinding, sieving by a sieve with 100 to 320 meshes, and standing for 2 to 10 hours to prepare the pressed powder.

Further, the specific step of S8 is:

s8.1: pressing the powder obtained in S7 under 1 to 5 MPa to form the powder with the density of 1.1 to 1.3 g/cm ³ The block is placed in a vacuum packaging bag for 2 to 10 hours;

s8.2: placing the mixture in a cold isostatic pressing device, pressing the mixture for 5 to 30min at 50 to 100 MPa, and then carrying out gradient pressure relief;

s8.3: standing for 2 to 10 hours after pressure relief is finished, pressing for 5 to 30min at 150 to 200 MPa, performing gradient pressure relief, taking out, peeling off a packaging bag, standing for 2 to 10 hours to obtain the density of 1.63 to 1.66 g/cm ³ The green block of (1).

Compared with the prior art, the invention has the following beneficial effects:

1. the invention adopts graphite powder, a sulfur-containing cross-linking agent, a dispersing agent oleic acid, a low quinoline insoluble content asphalt, anthracene oil, coal tar, ethylene tar and other binders to prepare low-temperature carbonized powder A, and adopts a binder, calcined coke powder, a sulfur-containing cross-linking agent and a dispersing agent oleic acid to prepare low-temperature carbonized powder B.

In the preparation process, the dispersing agent can disperse the agglomerated graphite powder and the calcined coke powder, and the binder is easy to permeate into pores of the graphite powder and the calcined coke powder due to good fluidity and wettability, fills the pores and is coated on the surfaces of the graphite powder and the calcined coke powder. The sulfur-containing cross-linking agent is used as a cross-linking dehydrogenating agent, so that aromatic hydrocarbon molecules in the binder are condensed, aromatized and cyclized to form a cross-linked network to be coated on the surfaces of the graphite powder and the forged coke powder, and a hydrogen sulfide gas is separated out, so that the residual carbon content of the coal pitch is increased, the true density of the graphite powder and the forged coke powder is improved, and the porosity of the special graphite material is effectively reduced; and after low-temperature coking, carbide layers and carbides with activity and self-sintering performance are formed on the surfaces and in the pores of the graphite powder and the forged coke powder.

So make low temperature carbonization powder A and low temperature carbonization powder B have similar carbide layer and carbide to can effectively reduce the coefficient of thermal expansion difference of graphite powder and the burnt powder after forging, avoid the unburned bricks block that the preparation obtained to ftracture in heat treatment process, the burnt powder after forging has higher mechanical strength simultaneously, thereby is favorable to improving special graphite material's intensity.

Meanwhile, superfine green coke powder is pretreated by introducing a solvent with excellent self-sintering performance to fill in an in-situ welding spot formed between the interfaces of the low-temperature carbonization powder A and the low-temperature carbonization powder B, so that the self-shrinkage performance and the homogeneity of the low-temperature carbonization powder A and the low-temperature carbonization powder B are improved; and the superfine solvent pretreated green coke powder can fill in pores formed by the low-temperature carbonized powder A and the low-temperature carbonized powder B, increase the green body pressing density, reduce the open porosity and further improve the strength of the special graphite material.

2. According to the invention, the low-price waste graphite powder is used as the main aggregate to prepare the special graphite material, so that the cost of raw materials for preparing the special graphite material is reduced, the additional value and the usage amount of the waste graphite powder are improved, the self-sintering performance and the self-adhesion performance are improved by introducing the sintering factor, the special graphite material is prepared by one-step roasting graphitization, and the prepared special graphite material has excellent breaking strength and compressive strength.

3. The invention does not need dipping and multiple times of roasting, after the pressing and the forming, the graphitization can be directly carried out after one-time roasting and sintering, the process flow is simplified, the production period is shortened, and the labor cost, the energy cost, the time cost, the equipment investment and maintenance cost and the pollution treatment cost to the environment are greatly saved.

Drawings

FIG. 1 is a transmission electron micrograph of graphite powder and low-temperature-carbonized powder A in example 1.

Fig. 2-adsorption curve of graphite powder and low-temperature carbonized powder a in example 1.

Fig. 3-a graph showing the distribution of micropores of the graphite powder and the low-temperature carbonized powder a in example 1.

Fig. 4 is a macroscopic photograph showing that the graphite powder and the low-temperature carbonized powder a in example 1 are dissolved in tetrahydrofuran.

Fig. 5-ESR graphs of graphite powder and low-temperature-carbonized powder a in example 1.

FIG. 6 is a cross-sectional view of a specialty graphite material prepared in example 1, along with a polished-surface topography and backscatter plot.

Fig. 7-section view of the specialty graphite material prepared in example 2 along with topography and backscatter of the polished surface.

Fig. 8-section view of special graphite material prepared in example 3 and topography and backscatter plot of the polished surface.

Fig. 9-section view of the graphite material 1 and topography and backscatter of the polished surface.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

Example 1

S1: the method comprises the steps of purchasing isostatic pressing graphite waste powder from a graphite processing factory at low cost, removing metal impurities introduced by the powder through magnetic separation equipment, primarily grinding the graphite waste powder through a 3R Raymond mill, and preparing the graphite powder with the D50 of about 6.0 mu m by using an airflow mill for later use.

S2: 18 parts of modified asphalt with low quinoline insoluble content, 14 parts of medium-temperature asphalt, 8 parts of coal tar, 55 parts of graphite powder obtained by S1, 2 parts of dodecyl mercaptan, 1 part of tetramethyl thiuram disulfide and 2 parts of oleic acid are accurately weighed.

S3: putting graphite powder, dodecyl mercaptan, tetramethyl thiuram disulfide and oleic acid into a kneading pot, mixing for 1 h at 120 ℃, removing water, and rotating the kneading pot at a rotating speed of 30 r/min in a positive direction; after the moisture is removed, heating the powder to 185 ℃, introducing the modified asphalt, the medium-temperature asphalt and the coal tar mixed adhesive which are melted at the corresponding temperature (70 to 80 ℃ higher than the softening point of the asphalt) for kneading for 1 hour, wherein the rotation speed of a kneading pot is 50 r/min, the forward rotation and the reverse rotation are alternately carried out, and the mixing is carried out by intermittently opening and closing a cover. And after kneading is finished, the paste is quickly transferred to a material hopper of a sheet rolling machine, the sheet rolling is carried out for 2 times, the thickness of the rolled sheet is 2 mm, the temperature of the rolled sheet corresponds to the kneading temperature, the rotating speed is 10 r/min, cooling is carried out after the sheet rolling is finished, the material is crushed and ground after being placed for 10 hours after the temperature of the material is reduced to the room temperature, and the crushed powder is sieved by a sieve of 160 meshes and placed for 10 hours to prepare the pressed powder. And (2) performing compression molding on the prepared powder under 10 MPa by a compression molding process, standing for 10 h, placing in an atmosphere resistance furnace, performing pressure coking treatment at 500 ℃ for 4 h by program temperature control, cooling to room temperature along with the furnace, crushing and grinding the coking block, and sieving by a 200-mesh sieve to obtain the low-temperature carbonized powder A.

S4: 30 parts of modified asphalt with low quinoline insoluble content, 65 parts of calcined asphalt coke, 2 parts of dodecyl mercaptan, 1 part of tetramethyl thiuram disulfide and 2 parts of oleic acid are accurately weighed.

S5: putting the calcined asphalt coke, the dodecyl mercaptan, the tetramethyl thiuram disulfide and the oleic acid in the S4 into a kneading pot, mixing for 1 h at 120 ℃, removing water, and positively rotating the kneading pot at the rotating speed of 30 r/min; after the moisture is removed, heating to 175 ℃, melting the modified asphalt in the S4 and the medium-temperature asphalt, adding the melted modified asphalt and the medium-temperature asphalt into a kneading pot, kneading for 1 hour to obtain paste, wherein the rotation speed of the kneading pot is 50 r/min, forward rotation and reverse rotation are alternately performed, and intermittently opening and closing a cover for mixing; after kneading is finished, the paste is quickly transferred to a material hopper of a sheet rolling machine, the sheet rolling is carried out for 2 times, the sheet rolling thickness is 2 mm, the sheet rolling temperature corresponds to the kneading temperature, and the rotating speed is 10 r/min; cooling to room temperature after the sheet rolling is finished, standing for 10 h, crushing and grinding, sieving with a 160-mesh sieve, and standing for 10 h to obtain pressed powder; and (2) performing compression molding on the prepared powder under 10 MPa through a compression molding process, standing for 10 hours, placing in an atmosphere resistance furnace, performing temperature programming control, performing pressure coking treatment at 550 ℃ for 2 to 6 hours, cooling to room temperature along with the furnace, crushing and grinding the coked block, and sieving by using a 200-mesh sieve to obtain the low-temperature carbonized powder B.

S6: 15 parts of modified asphalt with accurate weight and high carbon residue, 70 parts of low-temperature carbonized powder A in S3, 10 parts of low-temperature carbonized powder B in S5 and 5 parts of solvent pretreated raw petroleum coke.

S7: putting the low-temperature carbonized powder A, the low-temperature carbonized powder B and the solvent pretreated raw petroleum coke in the step S6 into a kneading pot, mixing for 1 h at 120 ℃, removing water, and positively rotating the kneading pot at the rotating speed of 30 r/min; after the water removal is finished, heating the powder to 185 ℃, introducing the high-carbon residue modified high-temperature asphalt melted at the corresponding temperature, kneading for 1 h at the rotation speed of 50 r/min in a kneading pot, alternately performing forward rotation and reverse rotation, and intermittently opening and closing a cover for mixing. And after kneading is finished, quickly transferring the paste to a material hopper of a sheet rolling machine, rolling for 2 times, wherein the thickness of the rolled sheet is 2 mm, the temperature of the rolled sheet corresponds to the kneading temperature, the rotating speed is 20 r/min, cooling by program temperature control is carried out after the rolling is finished, crushing and grinding are carried out after the temperature of the material is reduced to room temperature and the material is placed for 10 hours, and the pressed powder is prepared after the material is sieved by a 160-mesh sieve and placed for 10 hours.

S8: pressing the pressed powder of S7 under 1 MPa to form a pressed powder with the density of 1.1 to 1.3 g/cm ³ The block body is packaged in a vacuum sealing bag and is placed for 5 hours; placing in a cold isostatic pressing device, maintaining the pressure at 200 MPa for 10 min, performing gradient pressure relief, taking out a sample, peeling off a packaging bag, and standing for 10 h to obtain the product with the density of 1.63-1.66 g/cm ³ The green block of (1).

S9: placing the green body block prepared in the step S8 in a stainless steel crucible, filling the green body block with a burying material, introducing nitrogen/argon, roasting at 1050 ℃ for 4 hours, cooling to 300 ℃ under program control, and naturally cooling to room temperature to obtain the green body block with the density of 1.68-1.74 g/cm ³ The fired block of (1). Placing the roasted block in a vacuum graphitization furnace for atmosphere protection, treating for 1 h at 2500 ℃, and then lowering the temperature to 200 ℃ under program controlThen, the mixture was naturally cooled to room temperature to obtain a bulk density of 1.83 g/cm ³ The special graphite material of (3).

1. The transmission electron microscope image, the adsorption curve, the micropore distribution curve, the macro-photograph of tetrahydrofuran-dissolved and the ESR curve of the graphite powder obtained by pretreatment and the low-temperature carbonized powder a obtained by preparation in this example are shown in fig. 1, fig. 2, fig. 3, fig. 4 and fig. 5, respectively.

Fig. 1 (a) shows graphite powder, fig. 1 (b) shows low-temperature carbonized powder a, and as can be seen from fig. 1, the active layer is successfully constructed on the surface of the graphite powder. As is clear from FIG. 2, the specific surface areas of the graphite powder and the low-temperature carbonized powder A were 14.445 m, respectively ² G and 4.077 m ² As can be seen from fig. 3, the pore volume of the low-temperature carbonized powder a is significantly lower than that of the graphite powder, indicating that the micropores of the graphite powder are filled with the modified pitch with low quinoline insoluble content and the medium-temperature pitch, thereby forming active layers in the pores of the graphite powder and increasing the true density of the graphite powder. The active layer filled in the pores of the graphite powder and the active layer wrapped on the surface of the graphite powder can play a 'needle effect' to construct a firmer structure.

Fig. 4 (a) shows the low-temperature carbonized powder a, fig. 4 (b) shows graphite powder, and as can be seen from fig. 4, the graphite powder does not change in color in tetrahydrofuran, but the low-temperature carbonized powder a changes to brown in tetrahydrofuran, which shows that the low-temperature carbonized powder a has active substances such as aliphatic and aromatic compounds soluble in tetrahydrofuran. Further, as can be seen from fig. 5, the radical content of the low-temperature carbonized powder a is much higher than that of the graphite powder, and the higher the radical content is, the stronger the strength is, indicating that the low-temperature carbonized powder a has higher activity and strength than the graphite powder.

2. The cross-sectional view, the polished surface topography and the back scattering pattern of the special graphite material prepared in this embodiment are shown in fig. 6, where fig. 6 (a) is the cross-sectional view, and the left and right views of fig. 6 (b) are the polished surface topography and the back scattering pattern, respectively, and as can be seen from fig. 6 (a), a dimple appears at the cross-sectional port, the structure is dense, and there is no through crack. As can be seen from fig. 6 (b), the special graphite material prepared in this example has a dense structure, uniform pore distribution, and no macropores. The results show that the special graphite material prepared by the invention has a compact structure and excellent performance.

Example 2

S2: 13 parts of modified asphalt with low quinoline insoluble content, 12 parts of coal tar, 5 parts of anthracene oil, 65 parts of graphite powder obtained by S1, 1 part of dodecyl mercaptan, 1 part of poly-sulfurized alkylphenol hydroxymethyl resin and 3 parts of oleic acid are accurately weighed.

S3: putting graphite powder, dodecyl mercaptan, polysulfide alkylphenol hydroxymethyl resin and oleic acid into a kneading pot, mixing for 1 h at 120 ℃, removing water, controlling the rotation speed of the kneading pot to be 30 r/min, and rotating positively; after the water is removed, heating the powder to 175 ℃, introducing modified asphalt and medium-temperature asphalt which are melted at corresponding temperature (70-80 ℃ higher than the softening point of the asphalt) for kneading for 1 h, wherein the rotation speed of a kneading pot is 50 r/min, the forward rotation and the reverse rotation are alternately carried out, and the cover is intermittently opened and closed for mixing. And after kneading is finished, the paste is quickly transferred to a material hopper of a sheet rolling machine, the sheet rolling is carried out for 2 times, the thickness of the rolled sheet is 2 mm, the temperature of the rolled sheet corresponds to the kneading temperature, the rotating speed is 10 r/min, cooling is carried out after the sheet rolling is finished, the material is crushed and ground after being placed for 10 hours after the temperature of the material is reduced to the room temperature, and the crushed powder is sieved by a sieve of 160 meshes and placed for 10 hours to prepare the pressed powder. And (2) performing compression molding on the prepared powder under 10 MPa through a compression molding process, standing for 10 hours, placing in an atmosphere resistance furnace, performing temperature program control, performing pressure coking treatment at 550 ℃ for 4 hours, cooling to room temperature along with the furnace, crushing and grinding the coking blocks, and sieving by using a 200-mesh sieve to obtain the low-temperature carbonized powder A.

S4: accurately weighing 10 parts of modified asphalt with low quinoline insoluble content, 10 parts of coal tar, 5 parts of ethylene tar, 70 parts of calcined asphalt coke, 1 part of dodecyl mercaptan, 2 parts of polysulfide alkylphenol hydroxymethyl resin and 2 parts of oleic acid.

S5: putting the calcined asphalt coke, the dodecyl mercaptan, the alkylphenol polysulfide hydroxymethyl resin and the oleic acid in the S4 into a kneading pot, mixing for 2 hours at 120 ℃, removing water, and positively rotating the kneading pot at the rotating speed of 50 r/min; after the water is removed, heating to 185 ℃, melting the modified asphalt in the S4 and the moderate-temperature asphalt, adding the melted modified asphalt and the moderate-temperature asphalt into a kneading pot, kneading for 1 to 2 hours to obtain paste, wherein the rotation speed of the kneading pot is 30 r/min, the forward rotation and the reverse rotation are alternately carried out, and the mixing is carried out by intermittently opening and closing a cover; after kneading is finished, the paste is quickly transferred to a material hopper of a sheet rolling machine, the sheet rolling is carried out for 2 times, the thickness of the rolled sheet is 2 mm, the sheet rolling temperature corresponds to the kneading temperature, and the rotating speed is 20 r/min; cooling to room temperature after the sheet rolling, standing for 10 h, crushing and grinding, sieving with a 160-mesh sieve, and standing for 10 h to obtain pressed powder; and (2) performing compression molding on the prepared powder under 10 MPa through a compression molding process, standing for 10 hours, placing in an atmosphere resistance furnace, performing pressure coking treatment at 500 ℃ for 6 hours through program temperature control, cooling to room temperature along with the furnace, crushing and grinding the coking blocks, and sieving by using a 200-mesh sieve to obtain the low-temperature carbonized powder B.

S6: the method comprises the following steps of accurately weighing 17 parts of high-carbon-residue modified asphalt, 65 parts of low-temperature carbonized powder A in S3, 15 parts of low-temperature carbonized powder B in S5 and 3 parts of solvent pretreated raw asphalt coke.

S7: putting the low-temperature carbonized powder A, the low-temperature carbonized powder B and the solvent pretreated raw pitch coke in the S6 into a kneading pot, mixing for 1 h at 120 ℃, removing water, and rotating the kneading pot at a rotating speed of 30 r/min in a forward direction; after the moisture removal is finished, heating the powder to 200 ℃, introducing high-carbon-residue modified high-temperature asphalt melted at the corresponding temperature, kneading for 1 h at the rotation speed of 50 r/min in a kneading pot, alternately performing forward rotation and reverse rotation, and intermittently opening and closing a cover for mixing. And after kneading is finished, quickly transferring the paste to a material hopper of a sheet rolling machine, rolling for 2 times, wherein the thickness of the rolled sheet is 2 mm, the temperature of the rolled sheet corresponds to the kneading temperature, the rotating speed is 20 r/min, cooling by program temperature control is carried out after the rolling is finished, crushing and grinding are carried out after the temperature of the material is reduced to room temperature and the material is placed for 10 hours, and the pressed powder is prepared after the material is sieved by a 160-mesh sieve and placed for 10 hours.

S8: pressing the pressed powder of S7 under 1 MPa to form the powder with the density of 1.1 to 1.3 g/cm ³ The block body is packaged in a vacuum packaging bag and is placed for 5 hours; placing in cold isostatic pressing equipment, maintaining the pressure at 200 MPa for 10 min, performing gradient pressure relief, taking out a sample,peeling off the packaging bag, and standing for 10 h to obtain the product with the density of 1.63-1.66 g/cm ³ The green block of (1).

S9: placing the green body block prepared in the S8 into a stainless steel crucible, filling the green body block with a burying material, introducing nitrogen/argon, roasting at 1050 ℃ for 4 hours, cooling to 300 ℃ under program control, and naturally cooling to room temperature to obtain the green body block with the density of 1.68-1.74 g/cm ³ The fired block of (2). Placing the roasted block in a vacuum graphitization furnace for atmosphere protection, treating for 1 h at 2500 ℃, cooling to 200 ℃ under program control, and naturally cooling to room temperature to obtain the bulk density of 1.82 g/cm ³ The special graphite material of (2).

The cross-sectional view, the polished surface topography and the back scattering pattern of the special graphite material prepared in this embodiment are shown in fig. 7, in which fig. 7 (a) is the cross-sectional view, and the left side view and the right side view of fig. 7 (b) are the polished surface topography and the back scattering pattern, respectively, and as can be seen from fig. 7 (a), the fracture surface has dimples at the end, the structure is dense, and there are no through cracks. As can be seen from fig. 7 (b), the special graphite material prepared in this example has a dense structure, uniform pore distribution, and no macropores. The results show that the special graphite material prepared by the invention has a compact structure and excellent performance.

Example 3

S2: accurately weighing 10 parts of coal tar, 21 parts of medium-temperature pitch, 4 parts of anthracene oil, 61 parts of graphite powder obtained by S1, 2 parts of poly-sulfurized alkylphenol hydroxymethyl resin and 2 parts of oleic acid.

S3: putting graphite powder, polysulfide alkylphenol hydroxymethyl resin and oleic acid into a kneading pot, mixing for 1 h at 120 ℃, removing water, and positively rotating the kneading pot at the rotating speed of 30 r/min; after the water is removed, the powder is heated to 185 ℃, the modified asphalt and the medium temperature asphalt which are melted at the corresponding temperature (70 to 80 ℃ higher than the softening point of the asphalt) are introduced for kneading for 1 hour, the rotation speed of a kneading pot is 50 r/min, the forward rotation and the reverse rotation are alternately carried out, and the mixing is carried out by intermittently opening and closing a cover. And after kneading is finished, the paste is quickly transferred to a material hopper of a sheet rolling machine, the sheet rolling is carried out for 2 times, the thickness of the rolled sheet is 2 mm, the temperature of the rolled sheet corresponds to the kneading temperature, the rotating speed is 10 r/min, cooling is carried out after the sheet rolling is finished, the material is crushed and ground after being placed for 10 hours after the temperature of the material is reduced to the room temperature, and the crushed powder is sieved by a sieve of 160 meshes and placed for 10 hours to prepare the pressed powder. And (2) performing compression molding on the prepared powder under 10 MPa by a compression molding process, standing for 10 h, placing in an atmosphere resistance furnace, performing pressure coking treatment at 600 ℃ for 4 h by program temperature control, cooling to room temperature along with the furnace, crushing and grinding the coking block, and sieving by a 200-mesh sieve to obtain the low-temperature carbonized powder A.

S4: accurately weighing 2 parts of coal tar, 12 parts of medium-temperature pitch, 13 parts of modified pitch with low quinoline insoluble content, 68 parts of calcined pitch coke, 1 part of dodecyl mercaptan, 2 parts of alkylphenol sulfide and 2 parts of oleic acid.

S5: putting the calcined asphalt coke in the S4, dodecyl mercaptan, alkylphenol sulfide and oleic acid into a kneading pot, mixing for 1 to 2 hours at 110 to 120 ℃, removing water, and rotating the kneading pot at a rotating speed of 10 to 50 r/min in a forward rotation manner; after the moisture is removed, heating to 155 ℃, melting the modified asphalt in the S4 and the medium-temperature asphalt, adding the melted modified asphalt and the medium-temperature asphalt into a kneading pot, kneading for 2 hours to obtain paste, wherein the rotation speed of the kneading pot is 10 r/min, forward rotation and reverse rotation are alternately performed, and intermittently opening and closing a cover for mixing; after kneading is finished, the paste is quickly transferred to a material hopper of a sheet rolling machine, the sheet rolling is carried out for 2 times, the thickness of the rolled sheet is 2 mm, the sheet rolling temperature corresponds to the kneading temperature, and the rotating speed is 30 r/min; after the rolling is finished and the temperature is cooled to room temperature, crushing and grinding are carried out after the rolling is carried out for 2 hours, and after the rolling is carried out by a sieve of 160 meshes, the rolling is carried out for 10 hours to prepare pressed powder; and (2) performing compression molding on the prepared powder under 30 MPa by a compression molding process, standing for 10 h, placing in an atmosphere resistance furnace, performing pressure coking treatment at 600 ℃ for 6 h by program temperature control, cooling to room temperature along with the furnace, crushing and grinding the coking block, and sieving by a 200-mesh sieve to obtain the low-temperature carbonized powder B.

S6: accurately weighing 18 parts of high-carbon-residue modified asphalt, 60 parts of low-temperature carbonized powder A in S3, 20 parts of low-temperature carbonized powder B in S5 and 2 parts of raw needle coke powder pretreated by a solvent.

S7: putting the low-temperature carbonized powder A, the low-temperature carbonized powder B and the solvent pretreated raw needle coke powder in the S6 into a kneading pot, mixing for 1 h at 120 ℃, removing water, and rotating the kneading pot at a rotating speed of 30 r/min in a forward direction; after the moisture is removed, the powder is heated to 190 ℃, then the high-carbon residue modified high-temperature asphalt which is melted at the corresponding temperature is introduced, the kneading is carried out for 1 h, the rotation speed of a kneading pot is 50 r/min, the forward rotation and the reverse rotation are alternately carried out, and the mixing is carried out by intermittently opening and closing a cover. And after kneading is finished, the paste is quickly transferred to a material hopper of a sheet rolling machine, the sheet rolling is carried out for 2 times, the thickness of the rolled sheet is 2 mm, the temperature of the rolled sheet corresponds to the kneading temperature, the rotating speed is 20 r/min, cooling by program temperature control is carried out after the sheet rolling is finished, crushing and grinding are carried out after the temperature of the material is reduced to room temperature and the material is sieved by a sieve of 160 meshes and then the material is shelved for 10 hours, so that the pressed powder is prepared.

S8: pressing the pressed powder of S7 under 1 MPa to form a pressed powder with the density of 1.1 to 1.3 g/cm ³ The block body is packaged in a vacuum packaging bag and is placed for 5 hours; placing in a cold isostatic pressing device, maintaining the pressure at 200 MPa for 10 min, performing gradient pressure relief, taking out a sample, peeling off a packaging bag, and standing for 10 h to obtain the product with the density of 1.63-1.66 g/cm ³ The green block of (1).

S9: placing the green body block prepared in the step S8 in a stainless steel crucible, filling the green body block with a burying material, introducing nitrogen/argon, roasting at 1050 ℃ for 4 hours, cooling to 300 ℃ under program control, and naturally cooling to room temperature to obtain the green body block with the density of 1.68-1.74 g/cm ³ The fired block of (1). Placing the roasted block in a vacuum graphitization furnace for atmosphere protection, treating for 1 h at 2500 ℃, cooling to 200 ℃ under program control, and naturally cooling to room temperature to obtain the bulk density of 1.84 g/cm ³ The special graphite material of (3).

The cross-sectional view, the polished surface topography and the back scattering pattern of the special graphite material prepared in this embodiment are shown in fig. 8, in which fig. 8 (a) is the cross-sectional view, and the left side view and the right side view of fig. 8 (b) are the polished surface topography and the back scattering pattern, respectively, and as can be seen from fig. 8 (a), the fracture surface has dimples at the end, the structure is dense, and there are no through cracks. As can be seen from fig. 8 (b), the special graphite material prepared in this example has a compact structure, uniform pore distribution, and no macropores. The results show that the special graphite material prepared by the invention has a compact structure and excellent performance.

Fig. 9 shows a cross-sectional view, a polished surface topography and a back scattering view of a special graphite material prepared in this embodiment from a commercially available graphite material (denoted as graphite material 1) abroad, where fig. 9 (a) is the cross-sectional view, and a left drawing and a right drawing of fig. 9 (b) are the polished surface topography and the back scattering view, respectively, and as compared with examples 1 to 3, it can be seen from fig. 9 (a) that no dimple appears at a cross-sectional port of the graphite material 1, the structure is loose, and no through crack exists. As can be seen from fig. 9 (b), under the same magnification (500 times), the graphite material 1 has a loose structure and obvious pores, and it can be clearly seen that many pores remain at the interface connection between particles, and some interconnected pores exist, and macropores appear. Therefore, the special graphite materials prepared in the examples 1 to 3 have better performance than the graphite material 1.

The basic performance parameters of the special graphite materials prepared in examples 1 to 3 and the graphite material 1 are shown in Table 1.

TABLE 1 basic Performance parameter comparison Table

As can be seen from the above table, the basic performance of the special graphite material prepared by the invention is superior to that of the graphite material 1, and simultaneously, the special graphite material also meets the current standards of isostatic pressing graphite YB/T4379-2014, isostatic pressing graphite YB/T4745-2019 for electric spark machining and isostatic pressing graphite YB/T4746-2019 for casting, namely: the volume density is more than or equal to 1.80 g/cm ³ The resistivity is less than or equal to 15 mu omega-m, the compressive strength is more than or equal to 85 MPa, the breaking strength is more than or equal to 40 MPa, the Shore hardness is more than or equal to 50 HS, and the ash content is less than or equal to 500 ppm.

Finally, it should be noted that the above-mentioned examples of the present invention are only examples for illustrating the present invention, and are not intended to limit the embodiments of the present invention. Variations and modifications in other variations will occur to those skilled in the art upon reading the foregoing description. Not all embodiments are exhaustive. All obvious changes and modifications of the present invention are within the scope of the present invention.

Claims

1. A method for preparing a special graphite material by isostatic pressing graphite waste in a short process is characterized by comprising the following steps:

s3: putting the graphite powder, the sulfur-containing cross-linking agent and the oleic acid in the S2 into a kneading pot for premixing, heating to 155-185 ℃ after moisture is removed, melting the binder of the S2, adding the melted binder into the kneading pot for kneading, after kneading, rolling, crushing, grinding, pressing and forming, then pressurizing for low-temperature carbonization treatment, crushing, grinding and sieving to obtain low-temperature carbonized powder A;

s4: preparing and weighing 25-30 parts of binder, 50-80 parts of calcined coke powder, 1-5 parts of sulfur-containing crosslinking agent and 1-5 parts of oleic acid;

s5: putting the calcined coke powder in the step S4, a sulfur-containing cross-linking agent and oleic acid into a kneading pot, removing water, heating to 155-185 ℃, melting the binder in the step S4, adding the melted binder into the kneading pot for kneading, after kneading, rolling, crushing, grinding, pressing and forming, then pressurizing for low-temperature carbonization treatment, crushing, grinding and sieving to obtain low-temperature carbonized powder B;

s6: accurately weighing 10 to 20 parts of high-carbon-residue modified asphalt, 60 to 70 parts of low-temperature carbonized powder A in S3, 10 to 20 parts of low-temperature carbonized powder B in S5, and 1 to 5 parts of solvent pretreated green coke powder;

s7: putting the low-temperature carbonized powder A, the low-temperature carbonized powder B and the solvent pretreated green coke powder in the step S6 into a kneading pot, removing water, heating to 170-200 ℃, melting the high-residual carbon modified asphalt in the step S6, adding the melted asphalt into the kneading pot, kneading, flaking, crushing and grinding to obtain pressed powder;

s8: pressing the pressed powder obtained in the step S7 into a powder with the density of 1.1 to 1.3 g/cm ³ Placing the block in a vacuum packaging bag for a period of time, and then placing the block in a cold static pressure device for cold static pressure pressing for 1 to 3 times to obtain the block with the density of 1.63 to 1.66 g/cm ³ Green compact blocks of (a);

s9: placing the green body block in a stainless steel crucible, filling the green body block with an embedding material, placing the green body block in a roasting furnace, applying pressure, introducing nitrogen or argon in the process of pressurized roasting, roasting at 800 to 1200 ℃ for 2 to 6 hours, reducing the temperature to 200 to 300 ℃ under program control, and naturally cooling to room temperature to obtain the product with the density of 1.68 to 1.74 g/cm ³ The block is roasted;

s10: placing the roasted block in a vacuum graphitization furnace for atmosphere protection, processing at 2400 to 2800 ℃ for 1 to 4 hours, performing program control to reduce the temperature to 200 to 300 ℃, and naturally cooling to room temperature to obtain the block with the volume density of 1.81 to 1.85 g/cm ³ The special graphite material of (2).

2. The method for preparing the special graphite material by the isostatic pressing graphite waste in the short process according to claim 1, wherein in S1, metal impurities in the graphite waste powder are removed by a magnetic separation device, and are sieved and classified, then the graphite waste powder is subjected to primary grinding by a 3R Raymond mill, and then is subjected to fine grinding by an airflow mill, so that the graphite powder with the D50 of 3-10 μm is obtained.

3. The method for preparing the special graphite material by the isostatic pressing graphite waste in the short process according to claim 1, wherein the binder is one or more of low-temperature pitch, modified pitch, medium-temperature pitch or high-temperature pitch with low quinoline insoluble content, anthracene oil, coal tar and ethylene tar.

4. The method for the short-run preparation of special graphite materials from isostatic pressing graphite waste according to claim 1, wherein the sulfur-containing cross-linking agent is one or more of dodecyl mercaptan, tetramethyl thiuram disulfide, dithiodimorpholine, alkylphenol methylol polysulfide resin, alkylphenol sulfide or alkylphenol polysulfide.

5. The method for preparing the special graphite material by the isostatic pressing graphite waste in the short process according to claim 1, wherein the step S3 comprises the following steps:

s3.1: putting the graphite powder, a sulfur-containing cross-linking agent and oleic acid into a kneading pot, mixing for 1 to 2 hours at 110 to 120 ℃, removing water, and rotating the kneading pot at a rotating speed of 10 to 50 r/min in a forward rotation manner;

s3.2: after the water is removed, heating to 155-185 ℃, melting the binder in the S2, adding the molten binder into a kneading pot, kneading for 1-2 h to obtain paste, wherein the rotation speed of the kneading pot is 10-50 r/min, and the forward rotation and the reverse rotation are alternately performed, and intermittently opening and closing a cover for mixing;

6. The method for preparing the special graphite material by the isostatic pressing graphite waste in the short process according to claim 1, wherein the calcined coke powder in S4 is one or two of calcined asphalt coke, petroleum coke and needle coke, and the D50 of the calcined coke powder is 3-10 μm.

7. The method for preparing a special graphite material by using isostatic pressing graphite waste in a short process according to claim 1, wherein the specific step of S5 is as follows:

s5.4: after the sheet rolling is finished and the sheet is cooled to the room temperature, the sheet is placed for 2 to 10 hours, then the sheet is crushed and ground, the sheet is sieved by a sieve with 100 to 320 meshes, and the sheet is placed for 2 to 10 hours to prepare pressed powder;

8. The method for preparing the special graphite material by the isostatic pressing graphite waste in the short process according to claim 1, wherein the solvent pretreatment raw coke powder in the S6 is one or more of raw petroleum coke, raw asphalt coke, raw needle coke or raw meso-carbon microspheres.

9. The method for preparing the special graphite material by the isostatic pressing graphite waste in the short process according to claim 1, wherein the step S7 comprises the following steps:

s7.3: and after kneading, quickly transferring to a material hopper of a sheet rolling machine, rolling for 1 to 2 times, wherein the thickness of the rolled sheet is 1 to 4 mm, the temperature of the rolled sheet corresponds to the kneading temperature, the rotating speed is 10 to 30 r/min, cooling by program temperature control after the rolling is finished, cooling to room temperature, standing for 2 to 10 hours, crushing and grinding, sieving by a sieve with 100 to 320 meshes, and standing for 2 to 10 hours to prepare the pressed powder.

10. The method for preparing a special graphite material by using isostatic pressing graphite waste in a short process according to claim 1, wherein the specific step of S8 is as follows:

s8.1: pressing the powder obtained in S7 under 1 to 5 MPa to form the powder with the density of 1.1 to 1.3 g/cm ³ Standing the block in a vacuum packaging bag for 2 to 10 hours;