CN114014662B - Selenium-graphene composite isostatic graphite material and preparation method thereof - Google Patents
Selenium-graphene composite isostatic graphite material and preparation method thereof Download PDFInfo
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Abstract
The invention relates to a preparation method of a selenium-graphene composite isostatic pressing graphite material, which specifically comprises the following steps: obtaining each component meeting index conditions, namely, first material mixing, first preforming and process treatment, second material mixing, second preforming, isostatic pressing and process treatment, and graphitizing treatment, and preparing the selenium-graphene composite isostatic pressing graphite material based on the steps, wherein the selenium-graphene composite isostatic pressing graphite material prepared by the method has uniform and fine structure, high volume density and excellent physicochemical index; through the selenium soaking process technology, the conductivity and the mechanical strength of the material are enhanced, the abrasion is small, the high temperature resistance is high, the thermal conductivity is strong, the corrosion resistance effect is excellent, and the service life and the stability of the material are improved.
Description
Technical Field
The invention relates to the field of novel graphite materials, in particular to a selenium-graphene composite isostatic pressing graphite material and a preparation method thereof, and especially relates to a selenium-graphene composite isostatic pressing graphite material with high volume density, high conductivity and good mechanical strength and a preparation method thereof.
Background
The unique structure of graphite makes it possess good self-lubricating property and good heat and electric conductivity, good corrosion resistance and thermal shock resistance, and at the same time, it also possesses low friction factor. Therefore, the method is widely applied in industry.
However, graphite has the disadvantages of high porosity and low mechanical strength, so that when graphite is used as a soft surface material, impregnation or the like is required to fill pores so as to improve the mechanical strength.
In the impregnation process, it is very important to select an appropriate impregnating agent. The nature of the impregnating agent determines the chemical stability, thermal stability, mechanical strength, and use temperature of the impregnated graphite.
However, the composite isostatic graphite material which has been researched and developed still has the defects of low volume density, low conductivity and low mechanical strength, and can not meet the requirements of high-end products. Accordingly, there is a need for improvements over existing composite isostatic graphite materials.
Disclosure of Invention
In view of the above, the invention aims to provide a selenium-graphene composite isostatic pressing graphite material with high conductivity, high mechanical strength and large volume density and a preparation method thereof, and aims to overcome the defects of the prior art.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: a preparation method of a selenium-graphene composite isostatic pressing graphite material comprises the following steps:
(1) Obtaining all components meeting index conditions, wherein the components comprise aggregate with the particle size of 1-45 mu m, powder with the particle size of 5-40 mu m, a binder, an impregnant and reduced selenium powder with the particle size of 10-50 mu m, wherein the aggregate is asphalt coke, and the powder comprises graphene, carbon black and graphite powder;
(2) Mixing the aggregate and the powder in the following weight ratio for the first time to prepare mixed powder A passing through a vibration screen;
wherein the mixing temperature is 100-200 ℃, the mixing time is 1-1.5h, and the mixture is naturally cooled to room temperature after mixing;
(3) Performing primary preforming and technological treatment, namely performing pressing, roasting, soaking and secondary roasting on the mixed powder A prepared in the step (2), crushing the prepared roasting green body B, and grinding the crushed roasted green body B into mixed powder A1 passing through a vibration screen;
(4) Mixing the mixed powder A1 obtained in the step (3) and the selenium powder in the step (1) for the second time according to the following weight ratio to prepare mixed powder A2 passing through a vibration screen;
90-95% of mixed powder A1
Selenium powder 5-10%
Wherein the mixing temperature is 160-180 ℃, the mixing time is 1.5-3h, and the mixture is naturally cooled to room temperature after mixing;
(5) A second pre-forming step, namely placing the mixed powder A2 prepared in the step (4) into a kneading pot, forming paste by a dry-mixing and wet-mixing process, performing second pre-forming, crushing a blank body obtained by the second pre-forming, and grinding to prepare mixed powder A3 passing through a vibration screen; wherein, the mixing powder A2 in the wet mixing process and the binder in the step (1) are mixed according to the following weight ratio:
70-75% of mixed powder A2
25-30% of binder
(6) Isostatic compaction and technological treatment, namely filling mixed powder A3 into a rubber mold, sealing, performing cold isostatic compaction, maintaining the molding pressure at 150MPa for 7min to form an isostatic compaction blank, and then performing the procedures of roasting, soaking, secondary roasting, secondary soaking and tertiary roasting on the isostatic compaction blank to form a roasting blank B1, wherein the secondary soaking is to add liquid selenium with the purity of 99% into the roasting blank in the previous procedure as a soaking agent;
(7) And (3) graphitizing, namely placing the baked blank B1 prepared in the step (6) into a graphitizing furnace, heating the baked blank B1 to 2750-3200 ℃ under the condition of air isolation, converting the two-dimensional structure carbon product into a three-dimensional graphite grid structure, and transmitting electricity for 8-10 days according to the specification of the product to form the selenium-graphene composite isostatic pressing graphite material.
Further, the aggregate adopts the aggregate with the true density more than or equal to 2.13g/cm 3 The ash content is less than or equal to 0.20%, the volatile component is less than or equal to 0.25%, the sulfur content is less than or equal to 0.50%, and the aggregate consists of four asphalt cokes with different particle size ranges, specifically:
preferably, the aggregate is composed of four asphalt cokes with different particle size ranges, and specifically comprises the following components:
further, the powder material with the particle size of 5-40 μm specifically comprises:
graphene powder with particle size of 5-35 mu m and purity of 99.90% -99.99%;
carbon black powder with the grain diameter of 5-40 mu m and the resistivity of 0.6-0.9 mu omega-m;
graphite powder with particle size of 5-30 mu m and true density of more than or equal to 2.08g/cm 3 The resistivity is 5-8 mu omega m.
Further, the binder adopts medium-temperature coal tar pitch, the softening point is 83-86 ℃, the coking value is more than or equal to 51%, the ash content is less than or equal to 0.25%, and the quinoline insoluble matter is less than or equal to 0.50%; the impregnant adopts phenolic resin, and the water content is less than or equal to 4%; free phenol is less than or equal to 7 percent; the solid content is more than or equal to 75 percent; the carbon residue is more than or equal to 45 percent; the pH value is 6.5-7.5.
Further, the reduced selenium powder is prepared by mixing selenium powder with a density of 4.81×103/cm 3 Placing selenium powder with purity of 99.9% in a reduction furnace, reducing under the protection of hydrogen atmosphere to eliminate oxygen content and work hardening phenomenon in selenium powder, reducing at 300-450 deg.C for 3-5 hr, ball milling qualified selenium powder in ball mill for 0.5-1 hr, atomizing by electrodynamic atomization, and cooling at 10 deg.C 5 -10 6 K/s, and finally preparing the reduced selenium powder with the granularity of 10-50 mu m.
Further, the procedure treatment of pressing, roasting, impregnating and secondary roasting the mixed powder A in the step (3) is specifically as follows:
(3.1) charging the powder mixture A into a pressing mold at a rate of 1.5T/cm 2 Is formed by pressure pressing;
(3.2) placing the blank subjected to the first press molding into a roasting furnace for first roasting, wherein the roasting temperature is 20-1250 ℃, and the blank is kept at the 1250 ℃ for 48 hours, the roasting time is 400-500 hours, and naturally cooling to room temperature after discharging;
(3.3) placing the blank body finished in the previous step into an impregnation tank, adding phenolic resin for impregnation, wherein the impregnation temperature is 200 ℃, the impregnation pressure is 7-15MPa, and the impregnation time is 2-3h;
(3.4) placing the impregnated blank body in a roasting furnace again for secondary roasting at the roasting temperature of 20-1200 ℃ for 48h at the temperature of 1200 ℃ for 450-550h, and naturally cooling to room temperature after discharging to obtain a roasting blank body B.
Further, the mixed powder A2 in the step (5) is put into a kneading pot, and is subjected to a second pre-pressing forming process after being formed into paste by a dry-wet mixing process, specifically:
(5.1) pouring the mixed powder A2 into a kneading pot, and firstly carrying out dry mixing and stirring, wherein the dry mixing temperature is 130-140 ℃ and the dry mixing time is 45-50 minutes;
(5.2) after the dry mixing is finished, wet mixing the mixed powder A2 and the binder according to the weight ratio, wherein the temperature of the wet mixing binder is 140-150 ℃, and the wet mixing time is 40-45 minutes to form paste;
(5.3) placing the formed paste into a pressing die for secondary prepressing and forming, wherein the prepressing pressure is 25MPa, and the prepressing time is 5min.
Wherein, in the dry mixing and wet mixing process, the inlet temperature of the kneading pot is 220-250 ℃.
Further, the isostatic pressing blank body related in the step (6) is formed into a baked blank body B1 after the procedures of baking, dipping, secondary baking, secondary dipping and tertiary baking, specifically:
(6.1) the volume density of the isostatic pressing green body formed by the isostatic pressing process of the mixed powder A3 is 2.5-3.0g/cm 3 ；
(6.2) placing the isostatic pressing blank body into a graphite dry pot, filling metallurgical coke powder, compacting, filling into a ring-type roasting furnace, filling the roasting furnace with the coke powder, quartz sand and river sand, gradually heating according to a temperature rising curve under the condition of air isolation, and naturally cooling to room temperature and discharging;
(6.3) putting the blank body finished in the previous step into an impregnation tank, adding phenolic resin to carry out a first impregnation process, wherein the impregnation temperature is 220 ℃, the impregnation pressure is 7-15MPa, and the impregnation time is 2-3h;
(6.4) putting the blank body finished in the previous step into a roasting furnace again for secondary roasting, wherein the roasting temperature is 20-1250 ℃, the heat is preserved for 48 hours at the temperature of 1250 ℃, the roasting time is 550-600 hours, and naturally cooling to room temperature after discharging;
(6.5) carrying out a second impregnation process by taking the blank body finished in the previous step as an impregnant by adopting metal liquid selenium, firstly placing the blank body finished in the previous step into a graphite crucible, and then placing the graphite crucible into a preheating furnace for preheating to 320-350 ℃; meanwhile, placing metal selenium into a melting tank, adjusting the current to 220A, and metallizing the metal selenium into liquid after electrifying for 2 hours; then the crucible is pulled out of the preheating furnace and placed under a melting pool, molten metal selenium solution is poured into a high-temperature crucible with carbon strips, the high-temperature crucible is placed into vacuum equipment, vacuum pumping is started after no error is ensured, after the vacuum degree reaches 0.085MPa, the vacuum pumping is finished, and then the crucible is placed into the preheating furnace again to be preheated for half an hour to room temperature and then taken out;
(6.6) repeatedly placing the blank body finished in the previous step into a roasting chamber again for third roasting, wherein the roasting temperature is 20-1250 ℃, the heat is preserved for 48 hours at the temperature of 1250 ℃, the roasting time is 550-600 hours, and the blank body is naturally cooled to room temperature after being discharged from a furnace, so that a roasting blank body B1 is finally formed.
In addition, the invention also provides a selenium-graphene composite isostatic pressing graphite material which is prepared based on the preparation method, and the volume density of the prepared selenium-graphene composite isostatic pressing graphite material is more than or equal to 3.0g/cm 3 The resistivity is less than or equal to 8.0 mu omega m, the flexural strength is more than or equal to 75Mpa, the compressive strength is more than or equal to 160Mpa, the ash content is less than or equal to 0.25%, and the thermal expansion coefficient is less than or equal to 2.2 x 10 -6 /℃。
The invention has the beneficial effects that:
the selenium-graphene composite isostatic pressing graphite material prepared by the preparation method disclosed by the invention is uniform and fine in structure, high in volume density and excellent in physicochemical index; the invention enhances the conductivity and mechanical strength of the graphite composite conductive polymer material through the selenium soaking process technology, has small abrasion, high temperature resistance, strong thermal conductivity, excellent corrosion resistance effect and improves the service life and stability of the material; meanwhile, the volume density of the selenium-graphene composite isostatic pressing graphite material prepared by the invention is more than or equal to 3.0g/cm 3 The resistivity is less than or equal to 8.0 mu omega m, the flexural strength is more than or equal to 75Mpa, the compressive strength is more than or equal to 160Mpa, the ash content is less than or equal to 0.25%, and the thermal expansion coefficient is less than or equal to 2.2 x 10 -6 /℃。
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below. It is appreciated that the following drawings depict only certain embodiments of the application and are therefore not to be considered limiting of its scope. Other relevant drawings may be made by those of ordinary skill in the art without undue burden from these drawings.
FIG. 1 is a flow chart of the preparation method of the invention.
Detailed Description
Based on the background technology, the composite isostatic pressing graphite material which is researched and developed at present still has the defects of low volume density, low conductivity and low mechanical strength, and can not meet the requirements of high-end products.
The inventor of the application finds that the addition of graphene powder, graphite powder and liquid selenium is more beneficial to obtaining a high-quality composite isostatic pressing graphite material and improving the qualification rate of the composite isostatic pressing graphite material, and the physicochemical index of the final product can be fully satisfied, namely the requirements of volume density of more than or equal to 3.0g/cm < 3 >, resistivity of less than or equal to 8.0 mu omega m, flexural strength of more than or equal to 75Mpa, compressive strength of more than or equal to 160Mpa, ash content of less than or equal to 0.25% and thermal expansion coefficient of less than or equal to 2.2x10 < -6 >/DEG C are met.
The above prior art solutions have all the drawbacks that the applicant has obtained after practice and careful study, and therefore the discovery process of the above problems and the solutions presented in the following examples of the present application for the above problems should be all contributions to the present application made by the applicant during the course of the present application.
For the purposes of making the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application are clearly and completely described below, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. Thus, the following detailed description of the embodiments of the present application is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, based on the embodiments herein, which would be apparent to one of ordinary skill in the art without making any inventive effort, are intended to be within the scope of the present application.
Some embodiments of the present application are described in detail below.
As shown in fig. 1, the preparation method of the selenium-graphene composite isostatic pressing graphite material comprises the following steps:
(1) Obtaining each component meeting the index condition
The components comprise aggregate with the particle size of 1-45 mu m, powder with the particle size of 5-40 mu m, binder, impregnant and reduced selenium powder. Wherein the aggregate is asphalt coke, and the powder comprises graphene, carbon black and graphite powder.
The aggregate adopts the aggregate with the true density more than or equal to 2.13g/cm 3 The ash content is less than or equal to 0.20%, the volatile component is less than or equal to 0.25%, the sulfur content is less than or equal to 0.50%, and the aggregate consists of four asphalt cokes with different particle size ranges, specifically:
the invention uses a coarse crusher to crush asphalt coke to the particle size, and then uses an air flow mill to crush the asphalt coke to the particle size, and then uses the particle size to grind, screen and mix materials.
In the invention, the aggregate is preferably composed of four asphalt cokes with different particle size ranges, and specifically comprises the following components:
the powder material related in the invention is a powder material mixture with the particle size of 5-40 mu m, and specifically comprises the following components:
graphene powder with particle size of 5-35 mu m and purity of 99.90% -99.99%;
carbon black powder with the grain diameter of 5-40 mu m and the resistivity of 0.6-0.9 mu omega-m;
graphite powder with particle size of 5-30 mu m and true density of more than or equal to 2.08g/cm 3 The resistivity is 5-8 mu omega m.
The binder adopts medium-temperature coal pitch, the softening point is 83-86 ℃, the coking value is more than or equal to 51%, the ash content is less than or equal to 0.25%, and the quinoline insoluble matter is less than or equal to 0.50%.
The impregnant in the invention adopts phenolic resin, and the water content is less than or equal to 4%; free phenol is less than or equal to 7 percent; the solid content is more than or equal to 75 percent; the carbon residue is more than or equal to 45 percent; the pH value is 6.5-7.5.
The selenium powder is the reduced selenium powder, the particle size is 10-50 mu m, and the specific reduction process is as follows: the density was set at 4.81X 103/cm 3 Placing selenium powder with purity of 99.9% in a reduction furnace, reducing under the protection of hydrogen atmosphere to eliminate oxygen content and work hardening phenomenon in selenium powder, reducing at 300-450 deg.C for 3-5 hr, ball milling qualified selenium powder in ball mill for 0.5-1 hr, atomizing by electrodynamic atomization, and cooling at 10 deg.C 5 -10 6 K/s, and finally preparing the reduced selenium powder with the granularity of 10-50 mu m.
The inventor carries out multiple experiments, research analysis and product test production, and finally determines the components and the technical parameters of the components on the basis of raw material selection. The purpose of selecting materials is that, especially, graphene powder, graphite powder and selenium are added for immersing, thereby being more beneficial to obtaining high-quality selenium-based graphite composite conductive polymer material, being beneficial to extracting the qualification rate of the selenium-based graphite composite conductive polymer material, and the physicochemical index of the final product can be fully satisfied.
(2) First mixing material
Uniformly mixing the aggregate and the powder according to the following weight ratio, wherein the mixing temperature is 100-200 ℃, the mixing time is 1-1.5h, mixing to form mixed powder A ', naturally cooling to room temperature, and then placing the uniformly mixed powder A' into a Raymond mill for grinding to prepare mixed powder A passing through a vibration screen, wherein the mixed powder A comprises the following components: the particle size of the mixed powder A passing through the vibration screen is 5-10 mu m;
(3) First preforming and processing
After the mixed powder A prepared in the step (2) is subjected to the working procedures of pressing, roasting, soaking and secondary roasting, the prepared roasting green body B is crushed and then ground into mixed powder A1 passing through a vibration screen; wherein the particle size of the mixed powder A1 is 5-10 mu m.
Wherein, the procedure treatment of pressing, roasting, dipping and secondary roasting of the mixed powder A in the invention is specifically as follows:
(3.1) charging the powder mixture A into a pressing mold at a rate of 1.5T/cm with a 2500 ton press 2 The blank is pressed and molded for the first time;
(3.2) placing the blank subjected to the first press molding into a roasting furnace for first roasting, wherein the roasting temperature is 20-1250 ℃, and the blank is kept at the 1250 ℃ for 48 hours, the roasting time is 400-500 hours, and naturally cooling to room temperature after discharging;
(3.3) placing the blank body finished in the previous step into an impregnation tank, adding phenolic resin for primary impregnation, wherein the impregnation temperature is 200 ℃, the impregnation pressure is 7-15MPa, and the impregnation time is 2-3h;
(3.4) placing the blank after the first impregnation in a roasting furnace again for the second roasting, wherein the roasting temperature is 20-1200 ℃, the heat preservation is carried out for 48 hours at the temperature of 1200 ℃, the roasting time is 450-550 hours, and the blank is naturally cooled to room temperature after being discharged from the furnace, so as to obtain a roasting blank B.
Secondly, crushing the obtained roasting green body B by adopting a jaw crusher, and grinding by adopting a Raymond mill to obtain mixed powder A1 passing through a vibration screen.
(4) Second mixing
Uniformly mixing the mixed powder A1 obtained in the step (3) and the reduced selenium powder in the step (1) according to the following weight ratio, wherein the mixing temperature is 160-180 ℃, the mixing time is 1.5-3h, forming dry mixed powder A2 'after mixing, naturally cooling to room temperature, and then grinding the uniformly mixed dry mixed powder A2' by adopting an air flow mill and a Raymond mill to prepare mixed powder A2 passing through a vibration screen; wherein, the liquid crystal display device comprises a liquid crystal display device,
90-95% of mixed powder A1
Selenium powder 5-10%
(5) Second preforming
Placing the mixed powder A2 prepared in the step (4) into a kneading pot, forming paste by a dry-wet mixing process, performing secondary prepressing molding, crushing a secondary prepressing molding blank, and grinding into powder to prepare mixed powder A3 passing through a vibration screen;
in the above steps, the mixed powder A2 is formed into a paste after sequentially performing a dry-wet mixing process and then is preformed by a second pre-pressing process, and the specific process comprises the following steps:
(5.1) pouring the mixed powder A2 into a kneading pot, and firstly carrying out dry mixing and stirring uniformly, wherein the dry mixing temperature is 130-140 ℃ and the dry mixing time is 45-50 minutes;
(5.2) after the dry mixing is finished, wet mixing the mixed powder A2 and a binder according to the following weight ratio, wherein the temperature of the wet mixing binder is 140-150 ℃, and the wet mixing time is 40-45 minutes to form a paste;
70-75% of mixed powder A2
25-30% of binder
And (5.3) placing the paste formed by kneading into a pressing die for secondary prepressing and forming, wherein the prepressing pressure is 25MPa, and the prepressing time is 5min, so that a secondary prepressing and forming blank is obtained.
Wherein in the kneading process of the above (5.1) and (5.2), the kneading pot is a horizontal double reamer type, and the inlet temperature of the kneading pot is 220-250 ℃.
Meanwhile, in the wet mixing process of (5.2), the preferable weight ratio of the mixed powder A2 to the binder is 72:28.
the preferred weight ratio of the mixed powder A2 to the binder is as follows: at the moment, aggregate particles with different particle diameters are compactly stacked, and the volume density, the porosity, the mechanical strength and the thermal expansion coefficient of the selenium-graphene isostatic graphite composite material can reach a very good balance, namely the selenium-graphene isostatic graphite composite material has the characteristics of large volume density, small porosity and small thermal expansion coefficient.
In the step (5), the second pre-pressed blank is crushed by a jaw crusher, then is ground by an air flow mill and a Raymond mill, and finally is made into mixed powder A3 passing through a vibration screen.
(6) Isostatic compaction and technological treatment
And (3) filling the mixed powder A3 into a rubber mold, sealing, performing cold isostatic pressing, forming the isostatic pressing blank after maintaining the pressure for 7min at 150MPa, and then forming a baked blank B1 after the procedures of baking, dipping, secondary baking, secondary dipping and tertiary baking. The specific process is as follows:
(6.1) the volume density of the isostatic pressing green body formed by the isostatic pressing process of the mixed powder A3 is 2.3-2.5g/cm 3 ；
(6.2) placing the isostatic pressing blank body into a graphite dry pot, filling metallurgical coke powder, compacting, filling into a ring-type roasting furnace, filling the roasting furnace with the coke powder, quartz sand and river sand, gradually heating according to a temperature rising curve under the condition of air isolation, and naturally cooling to room temperature and discharging;
wherein, the gradual heating according to the temperature rise curve specifically means: at 150-350 ℃, the heating rate is 2.0-3.0 ℃/h, and the holding time is 55h; at 350-400 ℃, the temperature rising rate is 1.4-1.7 ℃/h, and the holding time is 40h; at 400-500 ℃, the temperature rising rate is 1.2-1.3 ℃/h, and the holding time is 85h; at 500-650 ℃, the temperature rising rate is 1.7-2.0 ℃/h, and the holding time is 72h; at 650-750 ℃, the temperature rising rate is 3.5-4.5 ℃/h, and the holding time is 24h; at 750-850 ℃, the temperature rising rate is 4.0-5.0 ℃/h, and the holding time is 24h; at 850-1150 ℃, the temperature rising rate is 6.5-8.5 ℃/h, and the holding time is 30h; at 1150-1250 ℃, the temperature rising rate is 8.0-8.5 ℃/h, and the holding time is 24h; maintaining at 1250 ℃ for 22 hours, naturally cooling to room temperature, and discharging;
(6.3) putting the blank body finished in the previous step into an impregnation tank, adding phenolic resin to carry out a first impregnation process, wherein the impregnation temperature is 220 ℃, the impregnation pressure is 7-15MPa, and the impregnation time is 2-3h;
(6.4) putting the blank body finished in the previous step into a roasting furnace again for secondary roasting, wherein the roasting temperature is 20-1250 ℃, the heat is preserved for 48 hours at the temperature of 1250 ℃, the roasting time is 550-600 hours, and naturally cooling to room temperature after discharging;
(6.5) carrying out a second impregnation process by taking the blank body finished in the previous step as an impregnant by adopting metal liquid selenium, firstly placing the blank body finished in the previous step into a graphite crucible, and then placing the graphite crucible into a preheating furnace for preheating to 320-350 ℃; meanwhile, placing metal selenium into a melting tank, adjusting the current to 220A, and metallizing the metal selenium into liquid after electrifying for 2 hours; then the crucible is pulled out of the preheating furnace and placed under a melting pool, molten metal selenium solution is poured into a high-temperature crucible with carbon strips, the high-temperature crucible is placed into vacuum equipment, vacuum pumping is started after no error is ensured, after the vacuum degree reaches 0.085MPa, the vacuum pumping is finished, and then the crucible is placed into the preheating furnace again to be preheated for half an hour to room temperature and then taken out;
(6.6) repeatedly placing the blank body finished in the previous step into a roasting chamber again for third roasting, wherein the roasting temperature is 20-1250 ℃, the heat is preserved for 48 hours at the temperature of 1250 ℃, the roasting time is 550-600 hours, and the blank body is naturally cooled to room temperature after being discharged from a furnace, so that a roasting blank body B1 is finally formed.
(7) Graphitization treatment
And (3) placing the roasting green body B1 prepared in the step (6) into an Acheson graphitization furnace, heating the roasting green body B1 to 2750-3200 ℃ under the condition of air isolation, converting a two-dimensional structure carbon product into a three-dimensional graphite grid structure, and transmitting electricity for 8-10 days according to the specification of the product to form the selenium-graphene composite isostatic pressing graphite material.
In addition, the invention also provides a selenium-graphene composite isostatic pressing graphite material which is prepared based on the preparation method, and the volume density of the prepared selenium-graphene composite isostatic pressing graphite material is more than or equal to 3.0g/cm 3 The resistivity is less than or equal to 8.0 mu omega m, the flexural strength is more than or equal to 75Mpa, the compressive strength is more than or equal to 160Mpa, the ash content is less than or equal to 0.25%, and the thermal expansion coefficient is less than or equal to 2.2 x 10 -6 /℃。
The selenium-graphene composite isostatic pressing graphite material prepared by the preparation method disclosed by the invention is uniform and fine in structure, high in volume density and excellent in physicochemical index; the invention enhances the conductivity and mechanical strength of the graphite composite conductive polymer material by selenium soaking process technology, has small abrasion, high temperature resistance and thermal conductivityThe material has strong corrosion resistance, and the service life and stability of the material are improved; meanwhile, the volume density of the selenium-graphene composite isostatic pressing graphite material prepared by the invention is more than or equal to 3.0g/cm 3 The resistivity is less than or equal to 8.0 mu omega m, the flexural strength is more than or equal to 75Mpa, the compressive strength is more than or equal to 160Mpa, the ash content is less than or equal to 0.25%, and the thermal expansion coefficient is less than or equal to 2.2 x 10 -6 /℃。
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, component disassembly, or combination thereof, etc. that falls within the spirit and principles of the present invention should be included in the scope of the present invention.
Claims (2)
1. A preparation method of a selenium-graphene composite isostatic pressing graphite material is characterized by comprising the following steps: the method comprises the following steps:
(1) Obtaining all components meeting index conditions, wherein the components comprise aggregate with the particle size of 1-45 mu m, powder with the particle size of 5-40 mu m, a binder, an impregnant and reduced selenium powder with the particle size of 10-50 mu m, wherein the aggregate is asphalt coke, and the powder comprises graphene, carbon black and graphite powder;
the aggregate adopts the aggregate with the true density more than or equal to 2.13g/cm 3 The ash content is less than or equal to 0.20%, the volatile component is less than or equal to 0.25%, the sulfur content is less than or equal to 0.50%, and the aggregate consists of four asphalt cokes with different particle size ranges, specifically:
particle size of 35 μm < 45 μm < 15wt%;
15 μm < particle size less than or equal to 35 μm 15wt%;
particle size of 10 μm is less than or equal to 15 μm 30wt%;
1< particle size less than or equal to 10 mu m 40wt%;
the powder with the particle size of 5-40 mu m specifically comprises the following components:
graphene powder with particle size of 5-35 mu m and purity of 99.90% -99.99%;
carbon black powder with the grain diameter of 5-40 mu m and the resistivity of 0.6-0.9 mu omega-m;
particle size of 5-30 μmGraphite powder material with true density not less than 2.08g/cm 3 The resistivity is 5-8 mu omega m;
the binder adopts medium-temperature coal pitch, the softening point is 83-86 ℃, the coking value is more than or equal to 51%, the ash content is less than or equal to 0.25%, and the quinoline insoluble matter is less than or equal to 0.50%; the impregnant adopts phenolic resin, and the water content is less than or equal to 4%; free phenol is less than or equal to 7 percent; the solid content is more than or equal to 75 percent; the carbon residue is more than or equal to 45 percent; the pH value is 6.5-7.5;
the reduced selenium powder is prepared by mixing selenium powder with density of 4.81×10 3 /cm 3 Placing selenium powder with purity of 99.9% in a reduction furnace, reducing under the protection of hydrogen atmosphere to eliminate oxygen content and work hardening phenomenon in selenium powder, reducing at 300-450 deg.C for 3-5 hr, ball milling qualified selenium powder in ball mill for 0.5-1 hr, atomizing by electrodynamic atomization, and cooling at 10 deg.C 5 -10 6 K/s, and finally preparing reduced selenium powder with the granularity of 10-50 mu m;
(2) Mixing the aggregate and the powder in the following weight ratio for the first time to prepare mixed powder A passing through a vibration screen;
50-60% of pitch coke
15-20% of graphene powder
10 to 15 percent of carbon black powder
10-15% of graphite powder
Wherein the mixing temperature is 100-200 ℃, the mixing time is 1-1.5h, and the mixture is naturally cooled to room temperature after mixing;
(3) Performing primary preforming and technological treatment, namely performing pressing, roasting, soaking and secondary roasting on the mixed powder A prepared in the step (2), crushing the prepared roasting green body B, and grinding the crushed roasted green body B into mixed powder A1 passing through a vibration screen;
the procedure treatment of pressing, roasting, dipping and secondary roasting of the mixed powder A in the step (3) is specifically as follows:
(3.1) charging the powder mixture A into a pressing mold at a rate of 1.5T/cm 2 Is formed by pressure pressing;
(3.2) placing the blank subjected to the first press molding into a roasting furnace for first roasting, wherein the roasting temperature is 20-1250 ℃, and the blank is kept at the 1250 ℃ for 48 hours, the roasting time is 400-500 hours, and naturally cooling to room temperature after discharging;
(3.3) placing the blank body finished in the previous step into an impregnation tank, adding phenolic resin for impregnation, wherein the impregnation temperature is 200 ℃, the impregnation pressure is 7-15MPa, and the impregnation time is 2-3h;
(3.4) placing the impregnated blank body in a roasting furnace again for secondary roasting at the roasting temperature of 20-1200 ℃ for 48h at the temperature of 1200 ℃ for 450-550h, and naturally cooling to room temperature after discharging to obtain a roasted blank body B;
(4) Mixing the mixed powder A1 obtained in the step (3) and the selenium powder in the step (1) for the second time according to the following weight ratio to prepare mixed powder A2 passing through a vibration screen;
90-95% of mixed powder A1
Selenium powder 5-10%
Wherein the mixing temperature is 160-180 ℃, the mixing time is 1.5-3h, and the mixture is naturally cooled to room temperature after mixing;
(5) A second pre-forming step, namely placing the mixed powder A2 prepared in the step (4) into a kneading pot, forming paste by a dry-mixing and wet-mixing process, performing second pre-forming, crushing a blank body obtained by the second pre-forming, and grinding to prepare mixed powder A3 passing through a vibration screen; wherein, the mixing powder A2 in the wet mixing process and the binder in the step (1) are mixed according to the following weight ratio:
70-75% of mixed powder A2
25-30% of binder
The mixed powder A2 in the step (5) is put into a kneading pot, and is subjected to a second pre-pressing forming process after being formed into paste through a dry-mixing and wet-mixing process, and the method specifically comprises the following steps:
(5.1) pouring the mixed powder A2 into a kneading pot, and firstly carrying out dry mixing and stirring, wherein the dry mixing temperature is 130-140 ℃ and the dry mixing time is 45-50 minutes;
(5.2) after the dry mixing is finished, wet mixing the mixed powder A2 and the binder according to the weight ratio, wherein the temperature of the wet mixing binder is 140-150 ℃, and the wet mixing time is 40-45 minutes to form paste;
(5.3) putting the formed paste into a pressing die for secondary pre-pressing forming, wherein the pre-pressing pressure is 25MPa, and the pre-pressing time is 5min;
wherein, in the dry mixing and wet mixing process, the inlet temperature of the kneading pot is 220-250 ℃;
(6) Isostatic compaction and technological treatment, namely filling mixed powder A3 into a rubber mold, sealing, performing cold isostatic compaction, maintaining the molding pressure at 150MPa for 7min to form an isostatic compaction blank, and then performing the procedures of roasting, soaking, secondary roasting, secondary soaking and tertiary roasting on the isostatic compaction blank to form a roasting blank B1, wherein the secondary soaking is to add liquid selenium with the purity of 99% into the roasting blank in the previous procedure as a soaking agent;
the isostatic pressing blank related in the step (6) is formed into a baked blank B1 after the procedures of baking, dipping, secondary baking, secondary dipping and tertiary baking, and the method specifically comprises the following steps: (6.1) the volume density of the isostatic pressing green body formed by the isostatic pressing process of the mixed powder A3 is 2.5-3.0g/cm 3 ；
(6.2) placing the isostatic pressing blank body into a graphite dry pot, filling metallurgical coke powder, compacting, filling into a ring-type roasting furnace, filling the roasting furnace with the coke powder, quartz sand and river sand, gradually heating according to a temperature rising curve under the condition of air isolation, and naturally cooling to room temperature and discharging;
(6.3) putting the blank body finished in the previous step into an impregnation tank, adding phenolic resin to carry out a first impregnation process, wherein the impregnation temperature is 220 ℃, the impregnation pressure is 7-15MPa, and the impregnation time is 2-3h;
(6.4) putting the blank body finished in the previous step into a roasting furnace again for secondary roasting, wherein the roasting temperature is 20-1250 ℃, the heat is preserved for 48 hours at the temperature of 1250 ℃, the roasting time is 550-600 hours, and naturally cooling to room temperature after discharging;
(6.5) carrying out a second impregnation process by taking the blank body finished in the previous step as an impregnant by adopting metal liquid selenium, firstly placing the blank body finished in the previous step into a graphite crucible, and then placing the graphite crucible into a preheating furnace for preheating to 320-350 ℃; meanwhile, placing metal selenium into a melting tank, adjusting the current to 220A, and metallizing the metal selenium into liquid after electrifying for 2 hours; then the crucible is pulled out of the preheating furnace and placed under a melting pool, molten metal selenium solution is poured into a high-temperature crucible with carbon strips, the high-temperature crucible is placed into vacuum equipment, vacuum pumping is started after no error is ensured, after the vacuum degree reaches 0.085MPa, the vacuum pumping is finished, and then the crucible is placed into the preheating furnace again to be preheated for half an hour to room temperature and then taken out;
(6.6) repeatedly placing the blank body finished in the previous step into a roasting chamber again for third roasting, wherein the roasting temperature is 20-1250 ℃, the heat is preserved for 48 hours at the temperature of 1250 ℃, the roasting time is 550-600 hours, and the blank body is naturally cooled to room temperature after being discharged from a furnace, so that a roasting blank body B1 is finally formed;
(7) And (3) graphitizing, namely placing the baked blank B1 prepared in the step (6) into a graphitizing furnace, heating the baked blank B1 to 2750-3200 ℃ under the condition of air isolation, converting the two-dimensional structure carbon product into a three-dimensional graphite grid structure, and transmitting electricity for 8-10 days according to the specification of the product to form the selenium-graphene composite isostatic pressing graphite material.
2. A selenium-graphene composite isostatic pressing graphite material is characterized in that the selenium-graphene composite isostatic pressing graphite material is prepared by adopting the method of any one of claims 1, and the volume density of the prepared selenium-graphene composite isostatic pressing graphite material is more than or equal to 3.0g/cm 3 The resistivity is less than or equal to 8.0 mu omega-m, the flexural strength is more than or equal to 75MPa, the compressive strength is more than or equal to 160MPa, the ash content is less than or equal to 0.25%, and the thermal expansion coefficient is less than or equal to 2.2 x 10 -6 /℃。
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