CN113979750A - High-purity isostatic pressing graphite material for spectral analysis and preparation method thereof - Google Patents
High-purity isostatic pressing graphite material for spectral analysis and preparation method thereof Download PDFInfo
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- CN113979750A CN113979750A CN202111146604.3A CN202111146604A CN113979750A CN 113979750 A CN113979750 A CN 113979750A CN 202111146604 A CN202111146604 A CN 202111146604A CN 113979750 A CN113979750 A CN 113979750A
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- 239000007770 graphite material Substances 0.000 title claims abstract description 43
- 238000000462 isostatic pressing Methods 0.000 title claims abstract description 29
- 238000010183 spectrum analysis Methods 0.000 title claims abstract description 29
- 238000002360 preparation method Methods 0.000 title claims abstract description 13
- 239000006229 carbon black Substances 0.000 claims abstract description 96
- 238000000034 method Methods 0.000 claims abstract description 77
- 238000002156 mixing Methods 0.000 claims abstract description 73
- 238000007580 dry-mixing Methods 0.000 claims abstract description 24
- 238000005087 graphitization Methods 0.000 claims abstract description 24
- 238000000748 compression moulding Methods 0.000 claims abstract description 12
- 238000005245 sintering Methods 0.000 claims abstract description 12
- 239000000843 powder Substances 0.000 claims description 157
- 239000002245 particle Substances 0.000 claims description 109
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 99
- 239000000463 material Substances 0.000 claims description 98
- 238000000227 grinding Methods 0.000 claims description 66
- 238000010438 heat treatment Methods 0.000 claims description 58
- 239000011300 coal pitch Substances 0.000 claims description 46
- 239000007787 solid Substances 0.000 claims description 45
- 239000010426 asphalt Substances 0.000 claims description 39
- 239000000571 coke Substances 0.000 claims description 36
- 238000005470 impregnation Methods 0.000 claims description 36
- 239000000203 mixture Substances 0.000 claims description 35
- 239000011294 coal tar pitch Substances 0.000 claims description 30
- 238000012216 screening Methods 0.000 claims description 30
- 239000011230 binding agent Substances 0.000 claims description 18
- 238000001816 cooling Methods 0.000 claims description 17
- 239000010439 graphite Substances 0.000 claims description 16
- 229910002804 graphite Inorganic materials 0.000 claims description 16
- 238000011049 filling Methods 0.000 claims description 15
- 229910052799 carbon Inorganic materials 0.000 claims description 12
- 239000012535 impurity Substances 0.000 claims description 12
- 238000000465 moulding Methods 0.000 claims description 12
- 239000006253 pitch coke Substances 0.000 claims description 9
- 238000005096 rolling process Methods 0.000 claims description 8
- 238000004611 spectroscopical analysis Methods 0.000 claims description 8
- 238000004939 coking Methods 0.000 claims description 7
- 238000002955 isolation Methods 0.000 claims description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- SMWDFEZZVXVKRB-UHFFFAOYSA-N Quinoline Chemical compound N1=CC=CC2=CC=CC=C21 SMWDFEZZVXVKRB-UHFFFAOYSA-N 0.000 claims description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
- 238000007599 discharging Methods 0.000 claims description 6
- 230000004584 weight gain Effects 0.000 claims description 6
- 235000019786 weight gain Nutrition 0.000 claims description 6
- 229910000831 Steel Inorganic materials 0.000 claims description 4
- 239000010959 steel Substances 0.000 claims description 4
- 239000006004 Quartz sand Substances 0.000 claims description 3
- 229910052786 argon Inorganic materials 0.000 claims description 3
- 239000003795 chemical substances by application Substances 0.000 claims description 3
- 238000009694 cold isostatic pressing Methods 0.000 claims description 3
- 239000007789 gas Substances 0.000 claims description 3
- 238000004898 kneading Methods 0.000 claims description 3
- 238000011068 loading method Methods 0.000 claims description 3
- 239000011148 porous material Substances 0.000 claims description 3
- 230000001681 protective effect Effects 0.000 claims description 3
- 239000004576 sand Substances 0.000 claims description 3
- 238000007789 sealing Methods 0.000 claims description 3
- 239000000126 substance Substances 0.000 claims description 3
- 239000000853 adhesive Substances 0.000 claims description 2
- 230000001070 adhesive effect Effects 0.000 claims description 2
- 239000002994 raw material Substances 0.000 abstract description 11
- 238000003763 carbonization Methods 0.000 abstract description 4
- 238000005516 engineering process Methods 0.000 description 5
- 230000003595 spectral effect Effects 0.000 description 5
- 238000001228 spectrum Methods 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 2
- 238000007598 dipping method Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000003921 oil Substances 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 239000002006 petroleum coke Substances 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
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- C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
- C04B35/52—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite
- C04B35/528—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite obtained from carbonaceous particles with or without other non-organic components
- C04B35/532—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite obtained from carbonaceous particles with or without other non-organic components containing a carbonisable binder
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- C04B35/52—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite
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Abstract
The invention relates to a preparation method of a high-purity isostatic pressing graphite material for spectral analysis, which comprises the following steps: the method comprises the steps of obtaining components meeting index conditions, preparing secondary carbon black, performing dry mixing for the first time, performing dry mixing for the second time, performing wet mixing, performing isostatic pressing and subsequent process treatment, and performing graphitization treatment to prepare the high-purity isostatic pressing graphite material for spectral analysis; the invention grinds the raw materials, then carries out compression molding, sintering and carbonization treatment, and finally increases the density and the strength of the high-purity graphite material through a graphitization process.
Description
Technical Field
The invention relates to the field of novel graphite materials, in particular to a high-purity isostatic pressing graphite material for spectral analysis and a preparation method thereof, and especially relates to a high-purity isostatic pressing graphite material for spectral analysis with high mechanical strength and a preparation method thereof.
Background
The graphite material for spectrum analysis is used specially for spectrum analysis. The graphite material applied to the spectral analysis is divided into graphite rods, graphite powder, graphite devices and the like according to the shape. The graphite in the graphite material can be used for spectrochemical analysis of all elements except carbon. The plasma of the carbon arc is above 5000 c, at which time known compounds are dissociated and the elements are excited to produce specific spectra. The existence of each element is identified according to the wavelength of the spectral line, the characteristic spectral line intensity of each element is measured, and the content of the element is measured.
In 1884, German chemists' Bensheng (R.H. Bunsen) mixed two portions of coal powder capable of coking and one portion of coke powder, and then pressed and formed in a steel mould, and then sintered to prepare the carbon electrode for spectral analysis application. Then scientifically and domestic pure carbon black, petroleum coke, pitch coke, coal pitch and the like are used as raw materials, high-intensity current is instantaneously applied to the two ends of the carbon rod after sintering, the carbon rod is graphitized, and the graphite material for spectral analysis is manufactured after impurities are removed.
Since the birth of high-purity graphite in 1942, the high-temperature purification technology of graphite is solved, and subsequently, the development of the spectral analysis technology, the spectral graphite with higher purity is developed and produced in succession in various countries.
The graphite material for spectral analysis needs to be extremely pure and must not contain impurities which are harmful to the analysis particle size while having conductivity, uniformity, thermal shock resistance, high purity, reproducibility. The arc spectrum of the spectrum pure electrode is in the range of 2000-3500, and only the extremely weak spectral lines of the following elements are allowed: boron, silicon, aluminum, magnesium, carbon black, titanium, and should not have spectral lines of other elements.
However, the currently developed graphite material for spectral analysis still has more impurity elements, and the purity still cannot meet the requirements of high-end technology. Therefore, it is necessary to further investigate this.
Disclosure of Invention
In view of this, the present invention aims to provide a high purity isostatic pressing graphite material for spectroscopic analysis and a preparation method thereof, aiming to overcome the defects of the prior art.
In order to achieve the purpose of the invention, the technical scheme adopted by the invention is as follows:
a preparation method of a high-purity isostatic pressing graphite material for spectral analysis comprises the following steps:
(1) obtaining components meeting index conditions, wherein the components comprise aggregate with the particle size of 1-60 mu m, powder with the particle size of 1-40 mu m, a binder and an impregnant, the aggregate is asphalt coke, and the powder comprises carbon black powder with the particle size of 1-20 mu m, graphite powder with the particle size of 1-40 mu m and solid coal tar pitch with the particle size of 1-15 mu m;
(2) preparation of Secondary carbon Black
(2.1) uniformly mixing the preheated carbon black powder and solid coal pitch according to the following weight ratio, and cooling to room temperature;
70 to 80 percent of carbon black powder material
20 to 30 percent of solid coal tar pitch powder
Wherein the mixing temperature is 150-250 ℃, and the mixing time is 1-3 h;
(2.2) rolling and grinding the mixture finished in the previous procedure into powder, so as to form uniformly mixed molding powder with the particle size of 1-50 mu m;
(2.3) carrying out compression molding, roasting, graphitization treatment and grinding on the molding powder finished in the previous procedure to prepare secondary carbon black powder with the particle size of 1-50 mu m;
(3) performing first dry mixing, namely uniformly mixing the secondary carbon black powder prepared in the step (2) and the graphite powder prepared in the step (1) according to the following weight ratio after preheating is completed to form a first dry mixed material;
20 to 25 percent of secondary carbon black powder
75 to 80 percent of graphite powder
Wherein the temperature of the first dry mixing is 150-250 ℃, and the mixing time is 1-3 h;
(4) performing dry mixing for the second time, namely uniformly mixing the first dry mixture prepared in the step (3) and the pitch coke prepared in the step (1) according to the following weight ratio to form a second dry mixture;
30 to 35 percent of first dry mixture
65-70% of aggregate asphalt coke
Wherein the temperature of the second dry mixing is 160-220 ℃, and the mixing time is 1-5 h;
(5) wet mixing, namely uniformly mixing the second dry mixture prepared in the step (4) and the binder prepared in the step (1) according to the following weight ratio to form a paste;
70 to 75 percent of the second dry mixture
25 to 30 percent of binder
Wherein the temperature of the wet mixing adhesive is 120-170 ℃, and the wet mixing time is 40-60 minutes;
(6) isostatic pressing and subsequent processing, namely filling the wet mixed material formed in the step (5) into a rubber mold, sealing, carrying out cold isostatic pressing, keeping the forming pressure at 150MPa for 7min, and then forming the product with the volume density of 2.0-2.5g/cm3The shaped green body of (1); then, the molded green body is subjected to roasting-sintering-dipping-secondary roasting-secondary dipping-tertiary roasting processes to prepare a roasted product for graphitization;
(7) and (4) graphitizing the calcined product for graphitization prepared in the step (6) to prepare the high-purity isostatic-pressing graphite material for spectral analysis.
Furthermore, the aggregate has true density not less than 2.13g/cm3The asphalt coke with ash content less than or equal to 0.1 percent and volatile matter less than or equal to 0.5 percent, and the aggregate with the particle size of 1-60 mu m comprises the following six asphalt cokes with different particle size ranges:
the asphalt coke with the granularity of 1-10 mu m accounts for 10 percent of the weight of the asphalt coke;
20% of the asphalt coke with the particle size of 10-20 μm;
20% of the asphalt coke with the particle size of 20-30 μm;
20% of the asphalt coke with the particle size of 30-40 μm;
20% of the asphalt coke with the particle size of 40-50 μm;
the asphalt coke with the particle size of 50-60 mu m accounts for 10 percent of the weight of the asphalt coke.
Furthermore, the graphite powder with the particle size of 1-40 mu m adopts the graphite powder with the true density of more than or equal to 2.00g/cm3Powder with resistivity less than or equal to 8.0 mu omega m, breaking strength more than or equal to 25Mpa, compressive strength more than or equal to 35Mpa and particle sizeThe graphite powder with the particle size of 1-40 mu m comprises the following four graphite powders with different particle size ranges:
graphite powder with the particle size of 1-10 mu m accounts for 25 percent of the weight of the graphite powder;
graphite powder with the particle size of 10-20 mu m accounts for 25 percent of the weight of the graphite powder;
graphite powder with the particle size of 20-30 mu m accounts for 25 percent of the weight of the graphite powder;
graphite powder with a particle size of 30-40 μm accounts for 25% of the weight of the graphite powder.
Further, the carbon black powder with the particle size of 1-20 μm has the purity of 99.99%, and the carbon black powder with the particle size of 1-20 μm comprises the following four carbon black powders with different particle size ranges, specifically:
the carbon black powder with the granularity of 1-5 mu m accounts for 20 percent of the weight of the carbon black powder;
carbon black powder with the particle size of 5-10 mu m accounts for 30 percent of the weight of the carbon black powder;
the carbon black powder with the particle size of 10-15 mu m accounts for 30 percent of the weight of the carbon black powder;
the carbon black powder with the particle size of 15-20 mu m accounts for 20 percent of the weight of the carbon black powder.
Further, the solid coal tar pitch with the grain diameter of 1-15 μm comprises the following three solid coal tar pitch powder materials with different grain diameter ranges:
the solid coal tar pitch powder with the granularity of 1-5 mu m accounts for 35 percent of the weight of the solid coal tar pitch powder;
the solid coal tar pitch powder with the granularity of 5-10 mu m accounts for 35 percent of the weight of the solid coal tar pitch powder;
the solid coal tar pitch powder with the granularity of 10-15 mu m accounts for 30 percent of the weight of the coal tar pitch powder.
Furthermore, the binder is modified coal pitch, and the technical indexes are that the softening point is 105-120 ℃, the coking value is more than or equal to 55 percent, and the ash content is less than or equal to 0.1 percent; the impregnant is medium-temperature coal pitch, and has the technical indexes that the softening point is 83-88 ℃, the coking value is more than or equal to 52 percent, and the quinoline insoluble substance is less than or equal to 0.30 percent.
Further, the step (2.1) of uniformly mixing the preheated carbon black powder and the solid coal pitch according to the weight ratio and then cooling the mixture to room temperature specifically comprises the following steps: respectively preheating carbon black powder and solid coal pitch in a preheating furnace at the temperature of 200-300 ℃ for 60-120min, placing the preheated carbon black powder and the solid coal pitch in a grinding machine, and grinding for 40-80min at the rotating speed of 350-600 r/min; after grinding, screening and grading, then mixing the screened and graded carbon black powder and solid coal pitch according to the proportion, and uniformly mixing the prepared carbon black powder and solid coal pitch in a kneading pot at the mixing temperature of 150-250 ℃ for 1-3 h; after the mixing is finished, naturally cooling the powder to room temperature;
the mixture involved in the step (2.2) is subjected to sheet rolling and powder grinding to form grinding powder with the particle size of 1-50 mu m and uniform mixing, and the method specifically comprises the following steps: the method comprises the following steps of performing twice sheet rolling on the mixture completed in the previous procedure to form a primary rolled sheet with the particle size of 2-3mm and a secondary rolled sheet with the particle size of 1-1.5mm, then cooling the completed rolled sheet to below 40 ℃, crushing and grinding the rolled sheet by using a grinding machine to form ground powder with the particle size of 1-50 mu m, and screening and grading the ground powder to form the following five screened materials with different particle size ranges, wherein the screening materials specifically comprise:
the weight of the screening material with the grain diameter of 1-10 μm accounts for 25 percent,
the sieve material with the grain diameter of 10-20 μm accounts for 20% of the weight of the material,
the sieve material with the grain diameter of 20-30 μm accounts for 10% of the weight of the material,
the sieve material with the grain diameter of 30-40 μm accounts for 20% of the weight of the material,
the weight of the screening material with the grain diameter of 40-50 μm accounts for 25 percent;
further uniformly mixing the screened materials with different particle size ranges after screening and grading by adopting a cyclone mixer to form formed powder;
the molding powder involved in the step (2.3) is subjected to compression molding, roasting, graphitization treatment and grinding to prepare secondary carbon black powder with the particle size of 1-50 mu m, and the method specifically comprises the following steps:
(2.3.1) filling the uniformly mixed molding powder into a die, compacting, and performing compression molding by using a double-screw vertical oil press to form a molded green body;
(2.3.2) placing the molded green body into a graphite dry pot, filling metallurgical coke powder, compacting, then placing into a ring type roasting furnace, simultaneously filling the furnace with the coke powder, quartz sand and river sand, gradually heating according to a heating curve under the condition of air isolation, roasting to prepare a roasted green body, naturally cooling to room temperature, and discharging; the gradual heating and temperature rise according to the temperature rise curve specifically comprises the following steps: when the temperature is 150 ℃ and 350 ℃, the heating rate is 3.3 ℃/h, and the holding time is 60 h; at the temperature of 350 ℃ and 400 ℃, the heating rate is 1.7 ℃/h, and the holding time is 30 h; at the temperature of 400 ℃ and 500 ℃, the heating rate is 1.1 ℃/h, and the holding time is 90 h; at the temperature of 500 ℃ and 650 ℃, the heating rate is 2.0 ℃/h, and the holding time is 75 h; at 650 plus 750 ℃, the heating rate is 4.0 ℃/h, and the holding time is 25 h; at the temperature of 750 and 850 ℃, the heating rate is 4.0 ℃/h, and the holding time is 25 h; at 850-; at 1150-1250 ℃, the heating rate is 4 ℃/h, and the holding time is 25 h; keeping at 1250 ℃ for 24 h;
(2.3.3) placing the roasted blank into an Acheson graphitizing furnace, heating the roasted product to 2750-3200 ℃ by current under the condition of air isolation, converting the two-dimensional structure carbon product into a three-dimensional graphite grid structure, and transmitting power for 8-10 days according to the specification and size of the product to prepare a graphitized material;
(2.3.4) crushing the prepared graphitized material, placing the crushed graphitized material in a grinding machine, grinding the material for 50 to 80 minutes at the rotating speed of 350 to 600r/min to prepare grinding powder with the particle size of 1 to 50 mu m, and screening and classifying the grinding powder to form the following five grinding and screening materials with different particle size ranges,
the grinding sieve material with the grain diameter of 1-10 μm accounts for 25% of the weight of the material,
the grinding sieve material with the grain diameter of 10-20 μm accounts for 20% of the weight of the material,
the grinding sieve material with the grain diameter of 20-30 μm accounts for 10% of the weight of the material,
the grinding sieve material with the grain diameter of 30-40 μm accounts for 20% of the weight of the material,
the grinding sieve material with the grain diameter of 40-50 μm accounts for 25% of the weight of the material;
and then uniformly mixing the grinding and screening materials with different particle size ranges after screening and grading by adopting a cyclone mixer to form secondary carbon black powder for later use.
Further, the first dry mixing involved in the step (3) comprises the following specific processes: preheating secondary carbon black powder and graphite powder in a preheating furnace with the temperature of 200-350 ℃ for 60-120min respectively, then respectively placing the preheated secondary carbon black powder and the graphite powder in a grinding machine, grinding the preheated secondary carbon black powder and the graphite powder for 40-80min at the rotating speed of 350-600 r/min to form ground secondary carbon black powder and graphite powder, then mixing the ground secondary carbon black powder and the graphite powder according to the proportion, and then carrying out first dry mixing, wherein the temperature of the first dry mixing is 150-250 ℃, and the mixing time is 1-3 h to prepare a first dry mixed material;
the second dry mixing in the step (4) comprises the following specific processes: mixing the first dry mixture and the pitch coke according to the proportion, and then performing second dry mixing at the temperature of 160-220 ℃ for 1-5 hours to prepare a second dry mixture;
the wet mixing in the step (5) comprises the following specific processes: and uniformly mixing the second dry mixture and the modified coal pitch of the binder, wherein the temperature of the wet mixing binder is 120-170 ℃, and the wet mixing time is 40-60 minutes.
Further, the step (6) of subjecting the formed green body to a roasting-sintering-impregnating-secondary roasting-secondary impregnating-tertiary roasting process to prepare a roasted product for graphitization specifically comprises the following steps:
(6.1) placing the formed green body into a roasting furnace for primary roasting to obtain a primary roasted green body, wherein the roasting temperature is 20-1250 ℃, and the roasting process specifically comprises the following steps: heating at room temperature of-100 deg.C at a rate of 100 deg.C/h, and maintaining for 1 h; raising the temperature at 100 ℃ and 200 ℃ according to the speed of 100 ℃/h, and keeping the temperature for 1 h; heating at 200-900 deg.c and 100 deg.c/h for 7 hr; raising the temperature at 900-1250 ℃ according to the speed of 150 ℃/h, and keeping the temperature for 2 h; preserving heat for 4 hours at 1250 ℃, then naturally cooling and discharging;
(6.2) putting the primary baked blank into a sintering furnace to completely wrap the steel carbon, then filling protective gas argon until the pressure reaches 15-20 MPa, then heating to 1000-1250 ℃, keeping for 24-32 hours, and then taking out;
(6.3) preheating the sintered blank with the cleaned surface to 350 ℃, keeping the temperature for 10 hours, then putting the sintered blank into an impregnation tank, vacuumizing and pressurizing for 2.5 hours, then injecting the impregnant medium-temperature coal pitch into the impregnation tank, and keeping the pressure for 2.5 hours to ensure that the impregnant medium-temperature coal pitch is immersed into the pores of the sintered blank to complete primary impregnation; in the first impregnation process, the weight gain rate of the medium-temperature coal pitch in the impregnant in the first roasted product is more than or equal to 18 percent;
(6.4) carrying out secondary roasting on the primary impregnated green body by a tunnel kiln, wherein the aim of quickly sintering the asphalt is fulfilled in the roasting process, the highest roasting temperature is 750 ℃, and the roasting time is 192 h;
(6.5) putting the second-time roasted green body into an impregnation tank, and injecting an impregnant medium-temperature coal pitch into the impregnation tank under the conditions of keeping vacuum and pressurization to perform second impregnation treatment, wherein the specific impregnation process comprises the following steps: preheating the second-time roasted blank body, wherein the preheating temperature is 290-350 ℃, the preheating time is 14-18 hours, then the second-time roasted blank body is put into an impregnation tank, the vacuum pressure of the impregnation tank is-0.086 MPa, the vacuumizing time is 60-90 minutes, then the temperature of the impregnating agent medium temperature coal pitch is 140-160 ℃, the pressurizing pressure is 1.7-1.85 MPa, and the second impregnation is completed after the pressurizing time is 6-8 hours; in the second impregnation process, the weight gain rate of the medium-temperature coal pitch in the impregnant in the second roasting product is more than or equal to 15 percent.
(6.6) loading the second impregnated blank into a roasting furnace for third roasting to obtain a roasted product for graphitization, wherein the third roasting process is as follows: the temperature rise rate is 6-7 ℃/h at 20-300 ℃; when the temperature is 300-980 ℃, the heating rate is 2-3 ℃/h; when the temperature is 980-1100 ℃, the heating rate is 3-4 ℃/h; preserving the heat for 15-20 hours at 1100 ℃;
wherein at 300-980 ℃, the following temperature rise curve is preferably selected: the heating rate is 2 ℃/h at the temperature of 300-350 ℃; the heating rate is 1.5 ℃/h at 350-400 ℃; the heating rate is 0.9-1.2 ℃/h at 400-800 ℃; the temperature rise rate is 2-3 ℃/h at 800-980 ℃.
In addition, the invention also provides a high-purity isostatic pressing graphite material for spectral analysis, which is prepared based on the method, and the prepared high-purity isostatic pressing graphite material for spectral analysis has the flexural strength of more than or equal to 95MPa, the compressive strength of more than or equal to 40MPa, the resistivity of less than or equal to 10 mu omega.m, the porosity of 20-25 percent and the ash content of less than or equal to 10 mu omega.m-5Percent and volume density of 1.85-2.0g/cm3Total impurities ofElement is less than or equal to 6 x 10-5Percent, each impurity element is less than or equal to 2 x 10-5％。
The invention has the beneficial effects that:
the secondary carbon black, graphite powder and the like are added into the raw material pitch coke and are fused with other materials in the raw material, so that the mechanical strength of the finished graphite material can be supplemented; the raw materials are ground, then are subjected to compression molding, sintering and carbonization treatment, and finally are graphitized, so that the density and strength of the high-purity graphite material can be increased; the high-purity isostatic-pressing graphite material for spectral analysis prepared by the preparation method has the flexural strength of more than or equal to 95Mpa, the compressive strength of more than or equal to 40Mpa, the resistivity of less than or equal to 10 mu omega.m, the porosity of 20-25 percent and the ash content of less than or equal to 10 x 10-5Percent and volume density of 1.85-2.0g/cm3Total impurity elements less than or equal to 6 x 10-5Percent, each impurity element is less than or equal to 2 x 10-5％。
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed 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. For a person skilled in the art, it is possible to derive other relevant figures from these figures without inventive effort.
FIG. 1 is a flow chart of the preparation method of the present invention.
Detailed Description
Based on the background technology, the currently developed graphite material for spectral analysis still has more impurity elements, and the purity still cannot meet the requirements of high-end technology.
The inventor of the application finds that the mechanical strength of the finished graphite material can be supplemented by adding secondary carbon black, graphite powder and the like into the raw material pitch coke and fusing the secondary carbon black, the graphite powder and other materials in the raw material; the invention grinds the raw materials, then carries out compression molding, sintering and carbonization treatment, and finally increases the density and the strength of the high-purity graphite material through a graphitization process.
The above prior art solutions have drawbacks that are the results of practical and careful study, and therefore, the discovery process of the above problems and the solutions proposed by the following embodiments of the present application to the above problems should be the contributions of the applicant to the present application in the course of the present application.
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, 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, presented in the accompanying drawings, is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The following detailed description is presented in conjunction with certain embodiments of the present application.
As shown in fig. 1, a method for preparing a high-purity isostatic pressing graphite material for spectroscopic analysis comprises the following steps:
(1) obtaining each component meeting index conditions
The components comprise aggregate with the grain diameter of 1-60 mu m, powder with the grain diameter of 1-40 mu m, a binder and an impregnant.
Wherein the aggregate has true density of more than or equal to 2.13g/cm3The asphalt coke with ash content less than or equal to 0.1 percent and volatile matter less than or equal to 0.5 percent, and the aggregate with the particle size of 1-60 mu m comprises the following six asphalt cokes with different particle size ranges:
the asphalt coke with the granularity of 1-10 mu m accounts for 10 percent of the weight of the asphalt coke;
20% of the asphalt coke with the particle size of 10-20 μm;
20% of the asphalt coke with the particle size of 20-30 μm;
20% of the asphalt coke with the particle size of 30-40 μm;
20% of the asphalt coke with the particle size of 40-50 μm;
the asphalt coke with the particle size of 50-60 mu m accounts for 10 percent of the weight of the asphalt coke.
Wherein the powder material comprises carbon black powder with the particle size of 1-20 mu m, graphite powder with the particle size of 1-40 mu m and solid coal pitch with the particle size of 1-15 mu m;
in the invention, the carbon black powder with the particle size of 1-20 μm has the purity of 99.99 percent, and the carbon black powder with the particle size of 1-20 μm comprises the following four carbon black powders with different particle size ranges:
the carbon black powder with the granularity of 1-5 mu m accounts for 20 percent of the weight of the carbon black powder;
carbon black powder with the particle size of 5-10 mu m accounts for 30 percent of the weight of the carbon black powder;
the carbon black powder with the particle size of 10-15 mu m accounts for 30 percent of the weight of the carbon black powder;
the carbon black powder with the particle size of 15-20 mu m accounts for 20 percent of the weight of the carbon black powder.
In the invention, the graphite powder with the particle size of 1-40 mu m adopts the graphite powder with the true density of more than or equal to 2.00g/cm3The graphite powder with the specific resistance less than or equal to 8.0 mu omega m, the flexural strength more than or equal to 25Mpa and the compressive strength more than or equal to 35Mpa, and the graphite powder with the particle size of 1-40 mu m comprises the following four graphite powders with different particle size ranges:
graphite powder with the particle size of 1-10 mu m accounts for 25 percent of the weight of the graphite powder;
graphite powder with the particle size of 10-20 mu m accounts for 25 percent of the weight of the graphite powder;
graphite powder with the particle size of 20-30 mu m accounts for 25 percent of the weight of the graphite powder;
graphite powder with a particle size of 30-40 μm accounts for 25% of the weight of the graphite powder.
In the invention, the solid coal tar pitch with the grain diameter of 1-15 μm comprises the following three solid coal tar pitch powder materials with different grain diameter ranges:
the solid coal tar pitch powder with the granularity of 1-5 mu m accounts for 35 percent of the weight of the solid coal tar pitch powder;
the solid coal tar pitch powder with the granularity of 5-10 mu m accounts for 35 percent of the weight of the solid coal tar pitch powder;
the solid coal tar pitch powder with the granularity of 10-15 mu m accounts for 30 percent of the weight of the coal tar pitch powder.
In the invention, the binder is modified coal pitch, and the technical indexes are that the softening point is 105-120 ℃, the coking value is more than or equal to 55 percent, and the ash content is less than or equal to 0.1 percent; the impregnant is medium-temperature coal pitch, and has the technical indexes that the softening point is 83-88 ℃, the coking value is more than or equal to 52 percent, and the quinoline insoluble substance is less than or equal to 0.30 percent.
(2) Preparation of Secondary carbon Black
(2.1) uniformly mixing the preheated carbon black powder and solid coal pitch according to the following weight ratio, and cooling to room temperature; the following are: the weight ratio of the carbon black powder to the solid coal tar pitch
70 to 80 percent of carbon black powder material
20 to 30 percent of solid coal tar pitch powder
In this step, the specific process is expressed as: respectively preheating carbon black powder and solid coal pitch in a preheating furnace at the temperature of 200-300 ℃ for 60-120min, placing the preheated carbon black powder and the solid coal pitch in a grinding machine, and grinding for 40-80min at the rotating speed of 350-600 r/min; after grinding, screening and grading, then mixing the screened and graded carbon black powder and solid coal pitch according to the proportion, and uniformly mixing the prepared carbon black powder and solid coal pitch in a kneading pot at the mixing temperature of 150-250 ℃ for 1-3 h; after the mixing is finished, naturally cooling the powder to room temperature;
(2.2) rolling and grinding the mixture finished in the previous procedure into powder, so as to form uniformly mixed molding powder with the particle size of 1-50 mu m;
in this step, the specific process is expressed as: the method comprises the following steps of performing twice sheet rolling on the mixture completed in the previous procedure to form a primary rolled sheet with the particle size of 2-3mm and a secondary rolled sheet with the particle size of 1-1.5mm, then cooling the completed rolled sheet to below 40 ℃, crushing and grinding the rolled sheet by using a grinding machine to form ground powder with the particle size of 1-50 mu m, and screening and grading the ground powder to form the following five screened materials with different particle size ranges, wherein the screening materials specifically comprise:
the weight of the screening material with the grain diameter of 1-10 μm accounts for 25 percent,
the sieve material with the grain diameter of 10-20 μm accounts for 20% of the weight of the material,
the sieve material with the grain diameter of 20-30 μm accounts for 10% of the weight of the material,
the sieve material with the grain diameter of 30-40 μm accounts for 20% of the weight of the material,
the weight of the screening material with the grain diameter of 40-50 μm accounts for 25 percent;
further uniformly mixing the screened materials with different particle size ranges after screening and grading by adopting a cyclone mixer to form formed powder;
(2.3) carrying out compression molding, roasting, graphitization treatment and grinding on the molding powder finished in the previous procedure to prepare secondary carbon black powder with the particle size of 1-50 mu m;
in the above steps, the detailed process is as follows:
(2.3.1) filling the uniformly mixed molding powder into a die, compacting, and performing compression molding by using a double-screw vertical oil press to form a molded green body;
(2.3.2) placing the molded green body into a graphite dry pot, filling metallurgical coke powder, compacting, then placing into a ring type roasting furnace, simultaneously filling the furnace with the coke powder, quartz sand and river sand, gradually heating according to a heating curve under the condition of air isolation, roasting to prepare a roasted green body, naturally cooling to room temperature, and discharging; the gradual heating and temperature rise according to the temperature rise curve specifically comprises the following steps: when the temperature is 150 ℃ and 350 ℃, the heating rate is 3.3 ℃/h, and the holding time is 60 h; at the temperature of 350 ℃ and 400 ℃, the heating rate is 1.7 ℃/h, and the holding time is 30 h; at the temperature of 400 ℃ and 500 ℃, the heating rate is 1.1 ℃/h, and the holding time is 90 h; at the temperature of 500 ℃ and 650 ℃, the heating rate is 2.0 ℃/h, and the holding time is 75 h; at 650 plus 750 ℃, the heating rate is 4.0 ℃/h, and the holding time is 25 h; at the temperature of 750 and 850 ℃, the heating rate is 4.0 ℃/h, and the holding time is 25 h; at 850-; at 1150-1250 ℃, the heating rate is 4 ℃/h, and the holding time is 25 h; keeping at 1250 ℃ for 24 h;
(2.3.3) placing the roasted blank into an Acheson graphitizing furnace, heating the roasted product to 2750-3200 ℃ by current under the condition of air isolation, converting the two-dimensional structure carbon product into a three-dimensional graphite grid structure, and transmitting power for 8-10 days according to the specification and size of the product to prepare a graphitized material;
(2.3.4) crushing the prepared graphitized material, placing the crushed graphitized material in a grinding machine, grinding the material for 50 to 80 minutes at the rotating speed of 350 to 600r/min to prepare grinding powder with the particle size of 1 to 50 mu m, and screening and classifying the grinding powder to form the following five grinding and screening materials with different particle size ranges,
the grinding sieve material with the grain diameter of 1-10 μm accounts for 25% of the weight of the material,
the grinding sieve material with the grain diameter of 10-20 μm accounts for 20% of the weight of the material,
the grinding sieve material with the grain diameter of 20-30 μm accounts for 10% of the weight of the material,
the grinding sieve material with the grain diameter of 30-40 μm accounts for 20% of the weight of the material,
the grinding sieve material with the grain diameter of 40-50 μm accounts for 25% of the weight of the material;
and then uniformly mixing the grinding and screening materials with different particle size ranges after screening and grading by adopting a cyclone mixer to form secondary carbon black powder for later use.
(3) First dry blending
Uniformly mixing the secondary carbon black powder prepared in the step (2) and the graphite powder prepared in the step (1) according to the following weight ratio after preheating is finished to form a first dry mixture;
20 to 25 percent of secondary carbon black powder
75 to 80 percent of graphite powder
The specific process of the step is as follows: preheating the secondary carbon black powder and the graphite powder in a preheating furnace with the temperature of 200-350 ℃ for 60-120min, respectively placing the preheated secondary carbon black powder and the graphite powder in a grinding machine, grinding the preheated secondary carbon black powder and the graphite powder for 40-80min at the rotating speed of 350-600 r/min to form the ground secondary carbon black powder and the ground graphite powder, then mixing the ground secondary carbon black powder and the ground graphite powder according to the proportion, and performing first dry mixing at the temperature of 150-250 ℃ for 1-3 h to prepare a first dry mixed material.
(4) Second dry blending
Uniformly mixing the first dry mixture prepared in the step (3) with the asphalt coke prepared in the step (1) according to the following weight ratio to form a second dry mixture;
30 to 35 percent of first dry mixture
65-70% of aggregate asphalt coke
The specific process of the second dry mixing is as follows: and (3) mixing the first dry mixture and the pitch coke according to the proportion, and then carrying out dry mixing for the second time, wherein the temperature of the dry mixing for the second time is 160-220 ℃, and the mixing time is 1-5 h, so as to prepare a second dry mixture.
(5) Wet mixing
Uniformly mixing the second dry mixture prepared in the step (4) and the binder prepared in the step (1) according to the following weight ratio to form a paste;
70 to 75 percent of the second dry mixture
25 to 30 percent of binder
The wet mixing process comprises the following specific steps: and uniformly mixing the second dry mixture and the modified coal pitch of the binder, wherein the temperature of the wet mixing binder is 120-170 ℃, and the wet mixing time is 40-60 minutes.
(6) Isostatic compaction and subsequent processing
Filling the wet mixed material formed in the step (5) into a rubber mold, sealing, carrying out cold isostatic pressing, keeping the molding pressure at 150MPa for 7min, and then forming the rubber mold with the volume density of 2.0-2.5g/cm3The shaped green body of (1); and then the molded green body is subjected to the processes of roasting, sintering, dipping, secondary roasting, secondary dipping and tertiary roasting to prepare a roasted product for graphitization.
The molded green body is prepared into a calcined product for graphitization by roasting-sintering-impregnating-secondary roasting-secondary impregnating-tertiary roasting processes, and the specific process comprises the following steps:
(6.1) placing the formed green body into a roasting furnace for primary roasting to obtain a primary roasted green body, wherein the roasting temperature is 20-1250 ℃, and the roasting process specifically comprises the following steps: heating at room temperature of-100 deg.C at a rate of 100 deg.C/h, and maintaining for 1 h; raising the temperature at 100 ℃ and 200 ℃ according to the speed of 100 ℃/h, and keeping the temperature for 1 h; heating at 200-900 deg.c and 100 deg.c/h for 7 hr; raising the temperature at 900-1250 ℃ according to the speed of 150 ℃/h, and keeping the temperature for 2 h; preserving heat for 4 hours at 1250 ℃, then naturally cooling and discharging;
(6.2) putting the primary baked blank into a sintering furnace to completely wrap the steel carbon, then filling protective gas argon until the pressure reaches 15-20 MPa, then heating to 1000-1250 ℃, keeping for 24-32 hours, and then taking out;
(6.3) preheating the sintered blank with the cleaned surface to 350 ℃, keeping the temperature for 10 hours, then putting the sintered blank into an impregnation tank, vacuumizing and pressurizing for 2.5 hours, then injecting the impregnant medium-temperature coal pitch into the impregnation tank, and keeping the pressure for 2.5 hours to ensure that the impregnant medium-temperature coal pitch is immersed into the pores of the sintered blank to complete primary impregnation; in the first impregnation process, the weight gain rate of the medium-temperature coal pitch in the impregnant in the first roasted product is more than or equal to 18 percent;
(6.4) carrying out secondary roasting on the primary impregnated green body by a tunnel kiln, wherein the aim of quickly sintering the asphalt is fulfilled in the roasting process, the highest roasting temperature is 750 ℃, and the roasting time is 192 h;
(6.5) putting the second-time roasted green body into an impregnation tank, and injecting an impregnant medium-temperature coal pitch into the impregnation tank under the conditions of keeping vacuum and pressurization to perform second impregnation treatment, wherein the specific impregnation process comprises the following steps: preheating the second-time roasted blank body, wherein the preheating temperature is 290-350 ℃, the preheating time is 14-18 hours, then the second-time roasted blank body is put into an impregnation tank, the vacuum pressure of the impregnation tank is-0.086 MPa, the vacuumizing time is 60-90 minutes, then the temperature of the impregnating agent medium temperature coal pitch is 140-160 ℃, the pressurizing pressure is 1.7-1.85 MPa, and the second impregnation is completed after the pressurizing time is 6-8 hours; in the second impregnation process, the weight gain rate of the medium-temperature coal pitch in the impregnant in the second roasting product is more than or equal to 15 percent.
(6.6) loading the second impregnated blank into a roasting furnace for third roasting to obtain a roasted product for graphitization, wherein the third roasting process is as follows: the temperature rise rate is 6-7 ℃/h at 20-300 ℃; when the temperature is 300-980 ℃, the heating rate is 2-3 ℃/h; when the temperature is 980-1100 ℃, the heating rate is 3-4 ℃/h; preserving the heat for 15-20 hours at 1100 ℃;
wherein at 300-980 ℃, the following temperature rise curve is preferably selected: the heating rate is 2 ℃/h at the temperature of 300-350 ℃; the heating rate is 1.5 ℃/h at 350-400 ℃; the heating rate is 0.9-1.2 ℃/h at 400-800 ℃; the temperature rise rate is 2-3 ℃/h at 800-980 ℃.
(7) Graphitization treatment
And (4) graphitizing the calcined product for graphitization prepared in the step (6) to prepare the high-purity isostatic-pressing graphite material for spectral analysis. The specific process comprises the following steps: and (3) placing the roasted product for graphitization into an Acheson graphitization furnace, heating the roasted product to 2750-3200 ℃ by current under the condition of air isolation, converting the two-dimensional structure carbon product into a three-dimensional graphite grid structure, and transmitting power for 8-10 days according to the specification and size of the product to form the high-purity isostatic pressure graphite material for spectral analysis.
In addition, the invention also provides a high-purity isostatic pressing graphite material for spectral analysis, which is prepared based on the method, and the prepared high-purity isostatic pressing graphite material for spectral analysis has the flexural strength of more than or equal to 95MPa, the compressive strength of more than or equal to 40MPa, the resistivity of less than or equal to 10 mu omega.m, the porosity of 20-25 percent and the ash content of less than or equal to 10 mu omega.m-5Percent and volume density of 1.85-2.0g/cm3Total impurity elements less than or equal to 6 x 10-5Percent, each impurity element is less than or equal to 2 x 10-5％。
The secondary carbon black, graphite powder and the like are added into the raw material pitch coke and are fused with other materials in the raw material, so that the mechanical strength of the finished graphite material can be supplemented; the invention grinds the raw materials, then carries out compression molding, sintering and carbonization treatment, and finally increases the density and the strength of the high-purity graphite material through a graphitization process.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement, component separation or combination and the like made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims (10)
1. A preparation method of a high-purity isostatic pressing graphite material for spectral analysis is characterized by comprising the following steps: the method comprises the following steps:
(1) obtaining components meeting index conditions, wherein the components comprise aggregate with the particle size of 1-60 mu m, powder with the particle size of 1-40 mu m, a binder and an impregnant, the aggregate is asphalt coke, and the powder comprises carbon black powder with the particle size of 1-20 mu m, graphite powder with the particle size of 1-40 mu m and solid coal tar pitch with the particle size of 1-15 mu m;
(2) preparation of Secondary carbon Black
(2.1) uniformly mixing the preheated carbon black powder and solid coal pitch according to the following weight ratio, and cooling to room temperature;
70 to 80 percent of carbon black powder material
20 to 30 percent of solid coal tar pitch powder
Wherein the mixing temperature is 150-250 ℃, and the mixing time is 1-3 h;
(2.2) rolling and grinding the mixture finished in the previous procedure into powder, so as to form uniformly mixed molding powder with the particle size of 1-50 mu m;
(2.3) carrying out compression molding, roasting, graphitization treatment and grinding on the molding powder finished in the previous procedure to prepare secondary carbon black powder with the particle size of 1-50 mu m;
(3) performing first dry mixing, namely uniformly mixing the secondary carbon black powder prepared in the step (2) and the graphite powder prepared in the step (1) according to the following weight ratio after preheating is completed to form a first dry mixed material;
20 to 25 percent of secondary carbon black powder
75 to 80 percent of graphite powder
Wherein the temperature of the first dry mixing is 150-250 ℃, and the mixing time is 1-3 h;
(4) performing dry mixing for the second time, namely uniformly mixing the first dry mixture prepared in the step (3) and the pitch coke prepared in the step (1) according to the following weight ratio to form a second dry mixture;
30 to 35 percent of first dry mixture
65-70% of aggregate asphalt coke
Wherein the temperature of the second dry mixing is 160-220 ℃, and the mixing time is 1-5 h;
(5) wet mixing, namely uniformly mixing the second dry mixture prepared in the step (4) and the binder prepared in the step (1) according to the following weight ratio to form a paste;
70 to 75 percent of the second dry mixture
25 to 30 percent of binder
Wherein the temperature of the wet mixing adhesive is 120-170 ℃, and the wet mixing time is 40-60 minutes;
(6) isostatic compactionAnd subsequent process treatment, namely filling the wet mixed material formed in the step (5) into a rubber mold, sealing, carrying out cold isostatic pressing, keeping the pressure for 7min at 150MPa to form the rubber with the volume density of 2.0-2.5g/cm3The shaped green body of (1); then, the molded green body is subjected to roasting-sintering-dipping-secondary roasting-secondary dipping-tertiary roasting processes to prepare a roasted product for graphitization;
(7) and (4) graphitizing the calcined product for graphitization prepared in the step (6) to prepare the high-purity isostatic-pressing graphite material for spectral analysis.
2. The method for preparing a high-purity isostatic-pressing graphite material for spectroscopic analysis according to claim 1, wherein: the aggregate has true density of more than or equal to 2.13g/cm3The asphalt coke with ash content less than or equal to 0.1 percent and volatile matter less than or equal to 0.5 percent, and the aggregate with the particle size of 1-60 mu m comprises the following six asphalt cokes with different particle size ranges:
the asphalt coke with the granularity of 1-10 mu m accounts for 10 percent of the weight of the asphalt coke;
20% of the asphalt coke with the particle size of 10-20 μm;
20% of the asphalt coke with the particle size of 20-30 μm;
20% of the asphalt coke with the particle size of 30-40 μm;
20% of the asphalt coke with the particle size of 40-50 μm;
the asphalt coke with the particle size of 50-60 mu m accounts for 10 percent of the weight of the asphalt coke.
3. The method for preparing a high-purity isostatic-pressing graphite material for spectroscopic analysis according to claim 1, wherein: the graphite powder with the particle size of 1-40 mu m adopts the graphite powder with the true density of more than or equal to 2.00g/cm3The graphite powder with the specific resistance less than or equal to 8.0 mu omega m, the flexural strength more than or equal to 25Mpa and the compressive strength more than or equal to 35Mpa, and the graphite powder with the particle size of 1-40 mu m comprises the following four graphite powders with different particle size ranges:
graphite powder with the particle size of 1-10 mu m accounts for 25 percent of the weight of the graphite powder;
graphite powder with the particle size of 10-20 mu m accounts for 25 percent of the weight of the graphite powder;
graphite powder with the particle size of 20-30 mu m accounts for 25 percent of the weight of the graphite powder;
graphite powder with a particle size of 30-40 μm accounts for 25% of the weight of the graphite powder.
4. The method for preparing a high-purity isostatic-pressing graphite material for spectroscopic analysis according to claim 1, wherein: the carbon black powder with the particle size of 1-20 mu m has the purity of 99.99 percent, and the carbon black powder with the particle size of 1-20 mu m comprises the following four carbon black powders with different particle size ranges:
the carbon black powder with the granularity of 1-5 mu m accounts for 20 percent of the weight of the carbon black powder;
carbon black powder with the particle size of 5-10 mu m accounts for 30 percent of the weight of the carbon black powder;
the carbon black powder with the particle size of 10-15 mu m accounts for 30 percent of the weight of the carbon black powder;
the carbon black powder with the particle size of 15-20 mu m accounts for 20 percent of the weight of the carbon black powder.
5. The method for preparing a high-purity isostatic-pressing graphite material for spectroscopic analysis according to claim 1, wherein: the solid coal tar pitch with the grain diameter of 1-15 mu m comprises the following three solid coal tar pitch powder with different grain diameter ranges:
the solid coal tar pitch powder with the granularity of 1-5 mu m accounts for 35 percent of the weight of the solid coal tar pitch powder;
the solid coal tar pitch powder with the granularity of 5-10 mu m accounts for 35 percent of the weight of the solid coal tar pitch powder;
the solid coal tar pitch powder with the granularity of 10-15 mu m accounts for 30 percent of the weight of the coal tar pitch powder.
6. The method for preparing a high-purity isostatic-pressing graphite material for spectroscopic analysis according to claim 1, wherein: the binder is modified coal pitch, and the technical indexes are that the softening point is 105-120 ℃, the coking value is more than or equal to 55 percent, and the ash content is less than or equal to 0.1 percent; the impregnant is medium-temperature coal pitch, and has the technical indexes that the softening point is 83-88 ℃, the coking value is more than or equal to 52 percent, and the quinoline insoluble substance is less than or equal to 0.30 percent.
7. The method for preparing a high-purity isostatic-pressing graphite material for spectroscopic analysis according to claim 1, wherein:
the step (2.1) of uniformly mixing the preheated carbon black powder and the solid coal pitch according to the weight ratio and then cooling the mixture to room temperature specifically comprises the following steps: respectively preheating carbon black powder and solid coal pitch in a preheating furnace at the temperature of 200-300 ℃ for 60-120min, placing the preheated carbon black powder and the solid coal pitch in a grinding machine, and grinding for 40-80min at the rotating speed of 350-600 r/min; after grinding, screening and grading, then mixing the screened and graded carbon black powder and solid coal pitch according to the proportion, and uniformly mixing the prepared carbon black powder and solid coal pitch in a kneading pot at the mixing temperature of 150-250 ℃ for 1-3 h; after the mixing is finished, naturally cooling the powder to room temperature;
the mixture involved in the step (2.2) is subjected to sheet rolling and powder grinding to form grinding powder with the particle size of 1-50 mu m and uniform mixing, and the method specifically comprises the following steps: the method comprises the following steps of performing twice sheet rolling on the mixture completed in the previous procedure to form a primary rolled sheet with the particle size of 2-3mm and a secondary rolled sheet with the particle size of 1-1.5mm, then cooling the completed rolled sheet to below 40 ℃, crushing and grinding the rolled sheet by using a grinding machine to form ground powder with the particle size of 1-50 mu m, and screening and grading the ground powder to form the following five screened materials with different particle size ranges, wherein the screening materials specifically comprise:
the weight of the screening material with the grain diameter of 1-10 μm accounts for 25 percent,
the sieve material with the grain diameter of 10-20 μm accounts for 20% of the weight of the material,
the sieve material with the grain diameter of 20-30 μm accounts for 10% of the weight of the material,
the sieve material with the grain diameter of 30-40 μm accounts for 20% of the weight of the material,
the weight of the screening material with the grain diameter of 40-50 μm accounts for 25 percent;
further uniformly mixing the screened materials with different particle size ranges after screening and grading by adopting a cyclone mixer to form formed powder;
the molding powder involved in the step (2.3) is subjected to compression molding, roasting, graphitization treatment and grinding to prepare secondary carbon black powder with the particle size of 1-50 mu m, and the method specifically comprises the following steps:
(2.3.1) filling the uniformly mixed molding powder into a die, compacting, and performing compression molding by using a double-screw vertical oil press to form a molded green body;
(2.3.2) placing the molded green body into a graphite dry pot, filling metallurgical coke powder, compacting, then placing into a ring type roasting furnace, simultaneously filling the furnace with the coke powder, quartz sand and river sand, gradually heating according to a heating curve under the condition of air isolation, roasting to prepare a roasted green body, naturally cooling to room temperature, and discharging; the gradual heating and temperature rise according to the temperature rise curve specifically comprises the following steps: when the temperature is 150 ℃ and 350 ℃, the heating rate is 3.3 ℃/h, and the holding time is 60 h; at the temperature of 350 ℃ and 400 ℃, the heating rate is 1.7 ℃/h, and the holding time is 30 h; at the temperature of 400 ℃ and 500 ℃, the heating rate is 1.1 ℃/h, and the holding time is 90 h; at the temperature of 500 ℃ and 650 ℃, the heating rate is 2.0 ℃/h, and the holding time is 75 h; at 650 plus 750 ℃, the heating rate is 4.0 ℃/h, and the holding time is 25 h; at the temperature of 750 and 850 ℃, the heating rate is 4.0 ℃/h, and the holding time is 25 h; at 850-; at 1150-1250 ℃, the heating rate is 4 ℃/h, and the holding time is 25 h; keeping at 1250 ℃ for 24 h;
(2.3.3) placing the roasted blank into an Acheson graphitizing furnace, heating the roasted product to 2750-3200 ℃ by current under the condition of air isolation, converting the two-dimensional structure carbon product into a three-dimensional graphite grid structure, and transmitting power for 8-10 days according to the specification and size of the product to prepare a graphitized material;
(2.3.4) crushing the prepared graphitized material, placing the crushed graphitized material in a grinding machine, grinding the material for 50 to 80 minutes at the rotating speed of 350 to 600r/min to prepare grinding powder with the particle size of 1 to 50 mu m, and screening and classifying the grinding powder to form the following five grinding and screening materials with different particle size ranges,
the grinding sieve material with the grain diameter of 1-10 μm accounts for 25% of the weight of the material,
the grinding sieve material with the grain diameter of 10-20 μm accounts for 20% of the weight of the material,
the grinding sieve material with the grain diameter of 20-30 μm accounts for 10% of the weight of the material,
the grinding sieve material with the grain diameter of 30-40 μm accounts for 20% of the weight of the material,
the grinding sieve material with the grain diameter of 40-50 μm accounts for 25% of the weight of the material;
and then uniformly mixing the grinding and screening materials with different particle size ranges after screening and grading by adopting a cyclone mixer to form secondary carbon black powder for later use.
8. The method for preparing the high-purity isostatic pressing graphite material for spectral analysis according to claim 1, wherein the method comprises the following steps:
the first dry mixing in the step (3) comprises the following specific processes: preheating secondary carbon black powder and graphite powder in a preheating furnace with the temperature of 200-350 ℃ for 60-120min respectively, then respectively placing the preheated secondary carbon black powder and the graphite powder in a grinding machine, grinding the preheated secondary carbon black powder and the graphite powder for 40-80min at the rotating speed of 350-600 r/min to form ground secondary carbon black powder and graphite powder, then mixing the ground secondary carbon black powder and the graphite powder according to the proportion, and then carrying out first dry mixing, wherein the temperature of the first dry mixing is 150-250 ℃, and the mixing time is 1-3 h to prepare a first dry mixed material;
the second dry mixing in the step (4) comprises the following specific processes: mixing the first dry mixture and the pitch coke according to the proportion, and then performing second dry mixing at the temperature of 160-220 ℃ for 1-5 hours to prepare a second dry mixture;
the wet mixing in the step (5) comprises the following specific processes: and uniformly mixing the second dry mixture and the modified coal pitch of the binder, wherein the temperature of the wet mixing binder is 120-170 ℃, and the wet mixing time is 40-60 minutes.
9. The method for preparing the high-purity isostatic pressing graphite material for spectral analysis according to claim 1, wherein the method comprises the following steps:
the molded green body involved in the step (6) is subjected to roasting-sintering-impregnation-secondary roasting-secondary impregnation-tertiary roasting processes to prepare a roasted product for graphitization, and the specific process comprises the following steps:
(6.1) placing the formed green body into a roasting furnace for primary roasting to obtain a primary roasted green body, wherein the roasting temperature is 20-1250 ℃, and the roasting process specifically comprises the following steps: heating at room temperature of-100 deg.C at a rate of 100 deg.C/h, and maintaining for 1 h; raising the temperature at 100 ℃ and 200 ℃ according to the speed of 100 ℃/h, and keeping the temperature for 1 h; heating at 200-900 deg.c and 100 deg.c/h for 7 hr; raising the temperature at 900-1250 ℃ according to the speed of 150 ℃/h, and keeping the temperature for 2 h; preserving heat for 4 hours at 1250 ℃, then naturally cooling and discharging;
(6.2) putting the primary baked blank into a sintering furnace to completely wrap the steel carbon, then filling protective gas argon until the pressure reaches 15-20 MPa, then heating to 1000-1250 ℃, keeping for 24-32 hours, and then taking out;
(6.3) preheating the sintered blank with the cleaned surface to 350 ℃, keeping the temperature for 10 hours, then putting the sintered blank into an impregnation tank, vacuumizing and pressurizing for 2.5 hours, then injecting the impregnant medium-temperature coal pitch into the impregnation tank, and keeping the pressure for 2.5 hours to ensure that the impregnant medium-temperature coal pitch is immersed into the pores of the sintered blank to complete primary impregnation; in the first impregnation process, the weight gain rate of the medium-temperature coal pitch in the impregnant in the first roasted product is more than or equal to 18 percent;
(6.4) carrying out secondary roasting on the primary impregnated green body by a tunnel kiln, wherein the aim of quickly sintering the asphalt is fulfilled in the roasting process, the highest roasting temperature is 750 ℃, and the roasting time is 192 h;
(6.5) putting the second-time roasted green body into an impregnation tank, and injecting an impregnant medium-temperature coal pitch into the impregnation tank under the conditions of keeping vacuum and pressurization to perform second impregnation treatment, wherein the specific impregnation process comprises the following steps: preheating the second-time roasted blank body, wherein the preheating temperature is 290-350 ℃, the preheating time is 14-18 hours, then the second-time roasted blank body is put into an impregnation tank, the vacuum pressure of the impregnation tank is-0.086 MPa, the vacuumizing time is 60-90 minutes, then the temperature of the impregnating agent medium temperature coal pitch is 140-160 ℃, the pressurizing pressure is 1.7-1.85 MPa, and the second impregnation is completed after the pressurizing time is 6-8 hours; in the second impregnation process, the weight gain rate of the medium-temperature coal pitch in the impregnant in the second roasting product is more than or equal to 15 percent.
(6.6) loading the second impregnated blank into a roasting furnace for third roasting to obtain a roasted product for graphitization, wherein the third roasting process is as follows: the temperature rise rate is 6-7 ℃/h at 20-300 ℃; when the temperature is 300-980 ℃, the heating rate is 2-3 ℃/h; when the temperature is 980-1100 ℃, the heating rate is 3-4 ℃/h; preserving the heat for 15-20 hours at 1100 ℃;
wherein at 300-980 ℃, the following temperature rise curve is preferably selected: the heating rate is 2 ℃/h at the temperature of 300-350 ℃; the heating rate is 1.5 ℃/h at 350-400 ℃; the heating rate is 0.9-1.2 ℃/h at 400-800 ℃; the temperature rise rate is 2-3 ℃/h at 800-980 ℃.
10. A high-purity isostatic pressing graphite material for spectral analysis, which is prepared by the method of any one of claims 1 to 9, and has a flexural strength of not less than 95MPa, a compressive strength of not less than 40MPa, a resistivity of not more than 10 [ mu ] Ω -m, a porosity of 20 to 25%, and an ash content of not more than 10 x 10-5Percent and volume density of 1.85-2.0g/cm3Total impurity elements less than or equal to 6 x 10-5Percent, each impurity element is less than or equal to 2 x 10-5％。
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