CN117987965A - Polyacrylonitrile-based carbon fiber, graphitized carbon fiber, and preparation methods and applications thereof - Google Patents
Polyacrylonitrile-based carbon fiber, graphitized carbon fiber, and preparation methods and applications thereof Download PDFInfo
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- 229920000049 Carbon (fiber) Polymers 0.000 title claims abstract description 110
- 239000004917 carbon fiber Substances 0.000 title claims abstract description 110
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 106
- 229920002239 polyacrylonitrile Polymers 0.000 title claims abstract description 77
- 239000011357 graphitized carbon fiber Substances 0.000 title claims abstract description 37
- 238000002360 preparation method Methods 0.000 title claims abstract description 28
- 238000003763 carbonization Methods 0.000 claims abstract description 116
- CKUAXEQHGKSLHN-UHFFFAOYSA-N [C].[N] Chemical compound [C].[N] CKUAXEQHGKSLHN-UHFFFAOYSA-N 0.000 claims abstract description 21
- 238000004519 manufacturing process Methods 0.000 claims abstract description 4
- 238000000034 method Methods 0.000 claims description 57
- 238000012360 testing method Methods 0.000 claims description 41
- 230000008569 process Effects 0.000 claims description 24
- 238000001069 Raman spectroscopy Methods 0.000 claims description 21
- 238000001237 Raman spectrum Methods 0.000 claims description 17
- 230000003647 oxidation Effects 0.000 claims description 15
- 238000007254 oxidation reaction Methods 0.000 claims description 15
- 239000002243 precursor Substances 0.000 claims description 13
- 230000003595 spectral effect Effects 0.000 claims description 13
- 238000001228 spectrum Methods 0.000 claims description 8
- 238000005087 graphitization Methods 0.000 claims description 6
- 239000000463 material Substances 0.000 claims description 6
- 239000003795 chemical substances by application Substances 0.000 claims description 5
- 238000002166 wet spinning Methods 0.000 claims description 4
- 238000006073 displacement reaction Methods 0.000 claims description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 22
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 15
- 229910052799 carbon Inorganic materials 0.000 description 11
- 229910052757 nitrogen Inorganic materials 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 10
- 239000000835 fiber Substances 0.000 description 8
- 238000010438 heat treatment Methods 0.000 description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- NLHHRLWOUZZQLW-UHFFFAOYSA-N Acrylonitrile Chemical compound C=CC#N NLHHRLWOUZZQLW-UHFFFAOYSA-N 0.000 description 1
- 238000002679 ablation Methods 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 229910003481 amorphous carbon Inorganic materials 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 150000001721 carbon Chemical group 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000001186 cumulative effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 239000012761 high-performance material Substances 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 239000003562 lightweight material Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000012643 polycondensation polymerization Methods 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 238000009987 spinning Methods 0.000 description 1
- 230000007847 structural defect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
- D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
- D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
- D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
- D01F9/20—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products
- D01F9/21—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
- D01F9/22—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyacrylonitriles
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Textile Engineering (AREA)
- Inorganic Fibers (AREA)
Abstract
The invention discloses polyacrylonitrile-based carbon fiber, graphitized carbon fiber, and a preparation method and application thereof. When the polyacrylonitrile-based carbon fiber is prepared, a carbonization pretreatment step is added between low-temperature carbonization treatment and high-temperature carbonization treatment; and graphitizing the polyacrylonitrile-based carbon fiber to obtain the graphitized carbon fiber. The mechanical properties of the polyacrylonitrile-based graphitized carbon fiber are greatly improved. The invention also provides a parameter model of the carbon fiber structure nitrogen-carbon ratio R, which can reasonably quantify the internal structure of the carbon fiber, and can be well applied to the preparation work of the high-modulus polyacrylonitrile-based carbon fiber by utilizing the parameter, thereby guiding the production and preparation work for the central control index in the preparation process of the high-performance carbon fiber.
Description
Technical Field
The invention relates to the technical field of carbon fibers, in particular to polyacrylonitrile-based carbon fibers, graphitized carbon fibers, and a preparation method and application thereof.
Background
The polyacrylonitrile-based carbon fiber is a high-performance material prepared by the procedures of polymerization reaction, spinning, oxidative carbonization treatment and the like which mainly comprise acrylonitrile monomers. In the oxidation process, long and straight polyacrylonitrile molecular chains in the polyacrylonitrile precursor gradually form a trapezoid high molecular structure with excellent heat resistance; in the subsequent carbonization process, non-carbon elements are gradually removed in a mode of releasing small molecular gas so as to form graphite sheets in the high-temperature carbonization treatment process at a higher temperature, so that the structure inside the fiber is perfected and the macroscopic mechanical property of the final carbon fiber is improved.
In the high temperature carbonization stage, the fiber subjected to the low temperature carbonization treatment needs to be further stripped of non-carbon elements, such as: and (5) denitrification. Before 1000 ℃, the denitrification mainly comprises the removal of NH 3 and HCN, so that the nitrogen content is rapidly reduced. Releasing NH 3 of one molecule, only reducing nitrogen content, and not affecting carbon content; in other words, such a way of removing non-carbon elements does not reduce the carbon yield of the final carbon fiber; however, if the fiber is extracted by releasing one molecule of HCN, the nitrogen content is reduced, and the carbon yield of the final carbon fiber is reduced. The third way of nitrogen removal is N 2, which is a denitrification high peak temperature region at about 1300 ℃, and mainly occurs solid phase condensation polymerization, so that carbon elements are enriched, a six-element carbon net plane structure is generated, and finally, the carbon fiber disordered layer graphite structure is formed.
Disclosure of Invention
The present inventors have found in the study that denitrification at the high-temperature carbonization stage has a significant influence on the amorphous structure (mainly amorphous carbon, and some structures containing carbon and nitrogen structures, etc.) and the ordered region structure (graphite-like structure) inside the carbon fiber, and seriously affects the performance of the high-performance carbon fiber, but the study on this aspect is relatively lacking in the prior art.
The inventor in the deep research of the carbonization process structure evolution mechanism in the preparation process of the polyacrylonitrile-based carbon fiber, proposes the structural parameter of the carbon fiber structure nitrogen-carbon ratio as an intermediate control index, and can control the structural order of the carbon fiber through the control of the index, thereby preparing the high-performance carbon fiber; and a corresponding processing method suitable for the index control is provided, namely: a short carbonization pretreatment is added between the low-temperature carbonization treatment step and the high-temperature carbonization treatment step; and is successfully applied to the preparation process of the high-modulus polyacrylonitrile carbon fiber.
In order to solve the technical problems in the prior art, the invention provides polyacrylonitrile-based carbon fibers, graphitized carbon fibers, and a preparation method and application thereof. The invention improves the mechanical property of the carbon fiber by controlling the structure of the polyacrylonitrile-based carbon fiber and improving the corresponding preparation mode.
One of the purposes of the invention is to provide a polyacrylonitrile-based carbon fiber, wherein the structural nitrogen-carbon ratio R of the polyacrylonitrile-based carbon fiber is 0<R or less than 3.5;
The structural nitrogen-carbon ratio r= (a D+AN)/AG;
Wherein A N is the product of the Y-axis coordinate corresponding to the spectral peak of the N peak of the Raman spectrum test curve and the half-peak width of the N peak;
A D is the product of the Y-axis coordinate corresponding to the spectral peak of the D peak of the Raman spectrum test curve and the half-peak width of the D peak;
A G is the product of the Y-axis coordinate corresponding to the spectral peak of the G peak of the Raman spectrum test curve and the half-peak width of the G peak.
In the raman spectrum of the present invention, a N mainly refers to an N-containing structure, and a G peak mainly refers to an sp 2 hybridized carbon atom structure; the a D peak is an sp 3 hybridized carbon structure; the structural nitrogen-carbon ratio R= (A D+AN)/AG) formula is obtained through inspection, and the R value calculated by the formula can effectively reflect the structural order on the polyacrylonitrile-based carbon fiber, and can be used as a judging index for judging whether the mechanical property of the graphitized carbon fiber is good or not after graphitizing the polyacrylonitrile-based carbon fiber.
According to the research of the inventor, when the structural nitrogen-carbon ratio R of the polyacrylonitrile-based carbon fiber is less than or equal to 3.5, the carbon fiber has more carbon structures (mainly sp2 hybridized carbon atoms) with regular internal arrangement and ordered structure, more structural defects are not formed, and the mechanical property of the final carbon fiber is better; and when R of the polyacrylonitrile-based carbon fiber is more than 3.5, the nitrogen content of the carbon fiber is more, so that more amorphous structures exist in the carbon fiber. When the structural nitrogen-carbon ratio R of the polyacrylonitrile-based carbon fiber is 0<R or less than 3.5, the structural order of the polyacrylonitrile-based carbon fiber is high, and the mechanical property of the prepared graphitized carbon fiber is better.
In the polyacrylonitrile-based carbon fiber according to the present invention, preferably,
The structural nitrogen-carbon ratio 0<R is less than or equal to 3.25.
In the polyacrylonitrile-based carbon fiber according to the present invention, preferably,
The spectrum peak corresponding to the A N is a Raman shift coordinate range of 1500-1540 cm -1, preferably 1510-1530 cm -1;
The corresponding spectrum peak of A D is a Raman displacement coordinate range of 1320-1380 cm -1, preferably 1355-1370 cm -1;
The X-axis coordinate corresponding to the peak of A G is 1575-1620 cm -1, preferably 1590-1620 cm -1.
In the polyacrylonitrile-based carbon fiber according to the present invention, preferably,
The laser wavelength range of the laser used in the Raman spectrum test is 510-640 nm; and/or the number of the groups of groups,
The power of the laser is 5-15 mW; and/or the number of the groups of groups,
The range of the accumulated exposure time is 1-20 s; and/or the number of the groups of groups,
The accumulated exposure times are 1 to 5 times; and/or the number of the groups of groups,
During testing, the output rate of the laser power is 50-100%.
The second object of the invention is to provide a preparation method of polyacrylonitrile-based carbon fiber, which comprises the following steps:
when the polyacrylonitrile-based carbon fiber is prepared, a carbonization pretreatment step is added between low-temperature carbonization treatment and high-temperature carbonization treatment;
the polyacrylonitrile-based carbon fiber described for the purpose of the present invention is preferably prepared.
In the method for preparing the polyacrylonitrile-based carbon fiber according to the present invention, preferably,
The temperature of the carbonization pretreatment is higher than that of the high-temperature carbonization treatment; and/or the number of the groups of groups,
The carbonization pretreatment time is lower than the high-temperature carbonization treatment time;
Preferably, the method comprises the steps of,
The carbonization pretreatment temperature is 1400-1700 ℃; preferably 1550-1700 ℃; such as 1400 ℃, 1450 ℃, 1500 ℃, 1550 ℃, 1600 ℃, 1650 ℃, 1700 ℃, and/or,
The carbonization pretreatment time is 10-20 seconds; preferably 10 to 15 seconds; for example, 10 seconds, 11 seconds, 12 seconds, 13 seconds, 14 seconds, 15 seconds, 16 seconds, 17 seconds, 18 seconds, 19 seconds, 20 seconds; and/or the number of the groups of groups,
The treatment atmosphere is an inert atmosphere, preferably nitrogen; and/or the number of the groups of groups,
The carbonization pretreatment process has no draft ratio, namely the draft ratio is 0.
In the method for preparing the polyacrylonitrile-based carbon fiber according to the present invention, preferably,
The method also comprises pre-oxidation treatment of the precursor before the low-temperature carbonization treatment;
Preferably, the method comprises the steps of,
The precursor is polyacrylonitrile precursor; and/or the number of the groups of groups,
In the invention, the pre-oxidation treatment is carried out under the conventional condition, preferably, the highest temperature of the pre-oxidation treatment is not more than 280 ℃, the lowest temperature is not less than 170 ℃, the total pre-oxidation time is not more than 120min, the treatment atmosphere is air atmosphere, and the draft ratio is 0-6%; preferably 0 to 3%; more preferably a six-stage pre-oxidation treatment;
More preferably, the process is carried out,
The polyacrylonitrile precursor is spun by wet spinning or dry-jet wet spinning; and/or the number of the groups of groups,
The polyacrylonitrile precursor is 3-24K.
In the present invention, the draft ratio means: the ratio of the linear velocity of the furnace exit roller to the linear velocity of the furnace entrance roller is expressed as lambda, the ratio of the difference between lambda and 1 to 1, and the corresponding value is the draft ratio. I.e. positive draft when λ > 1.00, and negative draft when λ < 1.00, for example. Such as: λ=1.01, then 1% of the positive draft; λ=0.99, then 1% negative draft or-1% draft.
In the preparation method of the polyacrylonitrile-based carbon fiber,
The temperature of the low-temperature carbonization treatment is 300-800 ℃; and/or the number of the groups of groups,
The total time of the low-temperature carbonization treatment is 2-6 min; and/or the number of the groups of groups,
The draft ratio is 0 to 6 percent; and/or the number of the groups of groups,
The treatment atmosphere is an inert atmosphere, preferably nitrogen.
More preferably, the low temperature carbonization treatment is performed in four stages, the low carbon four stages, the first stage: 300-400 ℃, 400-500 ℃ in the second section, 550-650 ℃ in the third section, 650-800 ℃ in the fourth section, and 30-50 seconds (preferably 40 seconds) of treatment time of each section.
In the method for preparing the polyacrylonitrile-based carbon fiber according to the present invention, preferably,
The temperature of the high-temperature carbonization treatment is 1000-1400 ℃; and/or the number of the groups of groups,
The total time of the high-temperature carbonization treatment is 1-3 min; and/or the number of the groups of groups,
The draft ratio is-4 to-1 percent; and/or the number of the groups of groups,
The treatment atmosphere is an inert atmosphere, preferably nitrogen.
According to the invention, the polyacrylonitrile precursor is subjected to pre-oxidation, low-temperature carbonization and high-temperature carbonization, and a special carbonization pretreatment step is arranged between the low-temperature carbonization and the high-temperature carbonization, so that the reasonable carbon fiber structure nitrogen-carbon ratio range can be regulated and controlled. The structural nitrogen-carbon ratio 0<R of the polyacrylonitrile-based carbon fiber is less than or equal to 3.5. The polyacrylonitrile-based carbon fiber with the structural nitrogen-carbon ratio 0<R being less than or equal to 3.5 can be subjected to subsequent graphitization treatment with higher heat treatment temperature, so that the high-modulus polyacrylonitrile-based graphitized carbon fiber can be prepared.
When the polyacrylonitrile-based carbon fiber prepared by the method comprising the specific carbonization pretreatment step is not used, the structural nitrogen-carbon ratio R is more than 3.5, which indicates that the carbon fiber has more nitrogen content and more amorphous structure in the carbon fiber. The low-temperature carbonized fiber is not subjected to the carbonization pretreatment step of the invention, and the release of the low-temperature carbonized fiber is not completed as low as possible when the low-temperature carbonized fiber is directly subjected to the high-temperature carbonization treatment, so that more bubbles or pores are left in the fiber, and the mechanical property of the final carbon fiber is poor. When the carbon fiber is subjected to graphitization treatment at a higher temperature, the mechanical properties of the final graphitized carbon fiber are also poor.
The third purpose of the invention is to provide the application of the polyacrylonitrile-based carbon fiber in the preparation of graphitized carbon fiber.
The invention provides a preparation method of graphitized carbon fiber, which comprises the following steps:
Graphitizing the polyacrylonitrile-based carbon fiber to obtain the graphitized carbon fiber, wherein the graphitized carbon fiber is preferably the polyacrylonitrile-based carbon fiber prepared by the polyacrylonitrile-based carbon fiber according to one of the purposes of the invention or the polyacrylonitrile-based carbon fiber prepared by the preparation method according to the second of the purposes of the invention.
In the method for producing graphitized carbon fiber according to the present invention, preferably,
The temperature of the graphitization treatment is 2200-2500 ℃; and/or the number of the groups of groups,
Graphitization treatment time is 1-5 min; and/or the number of the groups of groups,
The draft ratio is 5-10%; and/or the number of the groups of groups,
The treatment atmosphere is an inert atmosphere, preferably argon.
It is a fifth object of the present invention to provide a graphitized carbon fiber prepared by the preparation method of the fourth object of the present invention, preferably,
The tensile strength of the graphitized carbon fiber is more than or equal to 4000MPa, preferably more than or equal to 4288MPa; and/or the number of the groups of groups,
The tensile modulus is equal to or greater than 448GPa, preferably equal to or greater than 455GPa.
The sixth purpose of the invention is to provide the graphitized carbon fiber prepared by the preparation method of the fourth purpose of the invention or the application of the graphitized carbon fiber of the fifth purpose of the invention in high-strength materials.
In the invention, the high-strength material is a common high-strength material in the prior art, such as an aerospace vehicle composite material, an automobile lightweight material, a wind power generator rotor composite material and the like.
The endpoints of the ranges and any values disclosed in the present invention are not limited to the precise range or value, and the range or value should be understood to include values close to the range or value. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein. In the following, the individual technical solutions can in principle be combined with one another to give new technical solutions, which should also be regarded as specifically disclosed herein.
Compared with the prior art, the invention has at least the following advantages:
The invention also provides a parameter model of the carbon fiber structure nitrogen-carbon ratio, which can reasonably quantify the internal structure of the carbon fiber, and can be well applied to the preparation work of the high-modulus polyacrylonitrile-based carbon fiber by utilizing the parameter, thereby guiding the production and preparation work for the central control index in the preparation process of the high-performance carbon fiber.
According to the invention, a carbonization pretreatment step is introduced between a low-temperature carbonization step and a high-temperature carbonization step, and high-temperature instantaneous treatment in the carbonization pretreatment stage enables carbon fibers subjected to low-temperature carbonization to rapidly denitrify, so that the structural nitrogen-carbon ratio of the polyacrylonitrile-based carbon fibers can be well controlled, and the method can be used for preparing the polyacrylonitrile-based graphitized carbon fibers with good mechanical properties or preparing the high-modulus carbon fibers, and has important guiding significance for the high-performance carbon fiber industry. Therefore, the carbonization pretreatment provided by the invention well improves the mechanical properties of the final graphitized carbon fiber.
The mechanical property of the graphitized carbon fiber prepared by the invention exceeds the M46J grade of the east Asia company.
Drawings
FIG. 1 is a graph showing the Raman spectrum of the polyacrylonitrile-based carbon fiber of example 1 of the present invention.
Wherein the abscissa is raman shift (cm -1) and the ordinate is raman intensity (a.u.); y D is the spectral peak of the D peak of the raman spectral test curve; y N is the spectral peak of the N peak of the Raman spectrum test curve; y G is the spectral peak of the G peak of the raman spectral test curve; FWHM D is the half-width of the D peak in the Raman spectrum test curve; FWHM G is the half-width of the G peak in the Raman spectrum test curve; FWHM N is the half-width of the N peak in the Raman spectrum test curve.
Detailed Description
The present invention is described in detail below with reference to the specific drawings and examples, and it is necessary to point out that the following examples are given for further illustration of the present invention only and are not to be construed as limiting the scope of the present invention, since numerous insubstantial modifications and adaptations of the invention to those skilled in the art will still fall within the scope of the present invention.
In addition, the specific features described in the following embodiments may be combined in any suitable manner without contradiction. The various possible combinations of the invention are not described in detail in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention can be made, so long as the concept of the present invention is not deviated, and the technical solution formed thereby is a part of the original disclosure of the present specification, and also falls within the protection scope of the present invention.
The raw materials used in examples and comparative examples, if not particularly limited, are all as disclosed in the prior art, and are, for example, available directly or prepared according to the preparation methods disclosed in the prior art.
The testing method comprises the following steps:
The mechanical property test is carried out on the carbon fiber bundle filaments according to the national standard GB/T25749-2011.
Wherein the raman spectrum test curve is obtained by fitting with Labview software.
[ Example 1]
The polyacrylonitrile precursor spun by the domestic 3K wet method is subjected to gradient heating pre-oxidation treatment in an air atmosphere, six segments of pre-oxidation treatment are adopted for pre-oxidation, the temperature is 170 ℃/220 ℃/235 ℃/253 ℃/258 ℃/263 ℃ in sequence, the total pre-oxidation time is 80min, each segment is 13.3min, and the traction rate is 0. And sequentially carrying out low-temperature carbonization, carbonization pretreatment and high-temperature carbonization treatment on the polyacrylonitrile pre-oxidized filaments subjected to the pre-oxidation treatment in high-purity nitrogen to obtain the polyacrylonitrile-based carbon fibers. Wherein, the low temperature carbonization stage is gradient heating, and 4 sections of heating treatment are adopted in the low temperature carbonization stage, and the low temperature carbonization stage is the first section in sequence: 300 ℃, 450 ℃ in the second section, 550 ℃ in the third section, 750 ℃ in the fourth section, 40 seconds of treatment time in each section, and 0 traction multiplying power; carbonization pretreatment, wherein the temperature is 1400 ℃, the residence time is 15s, and the traction multiplying power is 0. The high-temperature carbonization treatment temperature adopts 4 sections of heating treatment, the first section is 1000 ℃, the second section is 1150 ℃, the third section is 1280 ℃, the fourth section is 1400 ℃, the high-temperature carbonization treatment time is 2min, the high-temperature carbonization treatment time of each section is 30s, and the draft ratio is-4%, thus obtaining the polyacrylonitrile-based carbon fiber.
The Raman spectrometer manufactured by the company Horiba Jobin Yvon in france is used for carrying out the test of Raman spectrum scanning on the polyacrylonitrile-based carbon fiber subjected to high-temperature carbonization treatment, and the result is shown in figure 1; wherein the Raman laser is 533nm, the laser power is 10mW, the exposure time is 10s, the accumulated exposure times are 5, and the output power is 50%; then, the Raman spectral lines of the materials are respectively obtained to obtain A N、AD and A G of a D peak, an N peak and a G peak; finally substituting the obtained product into a calculation formula: and R= (A D+AN)/AG) to obtain the structural nitrogen-carbon ratio of the polyacrylonitrile-based carbon fiber, and finally graphitizing the carbon fiber at a higher temperature, wherein the treatment temperature is 2400 ℃, the heat treatment time is 90s, the draft ratio is 5%, and the mechanical property test is carried out on the carbon fiber bundle filaments according to the national standard GB/T25749-2011, and the test result is shown in Table 1.
[ Example 2]
The carbonization pretreatment is carried out between low-temperature carbonization and high-temperature carbonization, the temperature is 1450 ℃, and the residence time is 15s. Other procedures and process parameters were the same as in example 1. The mechanical properties of the carbon fiber bundles were tested according to the national standard GB/T25749-2011, and the test results are shown in Table 1.
[ Example 3]
The carbonization pretreatment is carried out between low-temperature carbonization and high-temperature carbonization, the temperature is 1500 ℃, and the residence time is 15s. Other procedures and process parameters were the same as in example 1. The mechanical properties of the carbon fiber bundles were tested according to the national standard GB/T25749-2011, and the test results are shown in Table 1.
[ Example 4]
The carbonization pretreatment is carried out between low-temperature carbonization and high-temperature carbonization, the temperature is 1550 ℃, and the residence time is 15s. Other procedures and process parameters were the same as in example 1. The mechanical properties of the carbon fiber bundles were tested according to the national standard GB/T25749-2011, and the test results are shown in Table 1.
[ Example 5]
The carbonization pretreatment is carried out between low-temperature carbonization and high-temperature carbonization, the temperature is 1600 ℃, and the residence time is 15s. Other procedures and process parameters were the same as in example 1. The mechanical properties of the carbon fiber bundles were tested according to the national standard GB/T25749-2011, and the test results are shown in Table 1.
[ Example 6]
The carbonization pretreatment is carried out between low-temperature carbonization and high-temperature carbonization, the temperature is 1650 ℃, and the residence time is 15s. Other procedures and process parameters were the same as in example 1. The mechanical properties of the carbon fiber bundles were tested according to the national standard GB/T25749-2011, and the test results are shown in Table 1.
[ Example 7]
The carbonization pretreatment is carried out between low-temperature carbonization and high-temperature carbonization, the temperature is 1700 ℃, and the residence time is 15s. Other procedures and process parameters were the same as in example 1. The mechanical properties of the carbon fiber bundles were tested according to the national standard GB/T25749-2011, and the test results are shown in Table 1.
[ Example 8]
The carbonization pretreatment is carried out between low-temperature carbonization and high-temperature carbonization, the temperature is 1450 ℃, and the residence time is 20s. Other procedures and process parameters were the same as in example 1. The mechanical properties of the carbon fiber bundles were tested according to the national standard GB/T25749-2011, and the test results are shown in Table 1.
[ Example 9]
The carbonization pretreatment is carried out between low-temperature carbonization and high-temperature carbonization, the temperature is 1500 ℃, and the residence time is 20s. Other procedures and process parameters were the same as in example 1. The mechanical properties of the carbon fiber bundles were tested according to the national standard GB/T25749-2011, and the test results are shown in Table 1.
[ Example 10]
The carbonization pretreatment is carried out between low-temperature carbonization and high-temperature carbonization, the temperature is 1550 ℃, and the residence time is 20s. Other procedures and process parameters were the same as in example 1. The mechanical properties of the carbon fiber bundles were tested according to the national standard GB/T25749-2011, and the test results are shown in Table 1.
[ Example 11]
The carbonization pretreatment is carried out between low-temperature carbonization and high-temperature carbonization, the temperature is 1600 ℃, and the residence time is 20s. Other procedures and process parameters were the same as in example 1. The mechanical properties of the carbon fiber bundles were tested according to the national standard GB/T25749-2011, and the test results are shown in Table 1.
[ Example 12 ]
The carbonization pretreatment is carried out between low-temperature carbonization and high-temperature carbonization, the temperature is 1650 ℃, and the residence time is 20s. Other procedures and process parameters were the same as in example 1. The mechanical properties of the carbon fiber bundles were tested according to the national standard GB/T25749-2011, and the test results are shown in Table 1.
[ Example 13 ]
The carbonization pretreatment is carried out between low-temperature carbonization and high-temperature carbonization, the temperature is 1700 ℃, and the residence time is 20s. Other procedures and process parameters were the same as in example 1. The mechanical properties of the carbon fiber bundles were tested according to the national standard GB/T25749-2011, and the test results are shown in Table 1.
[ Example 14 ]
The carbonization pretreatment is carried out between low-temperature carbonization and high-temperature carbonization, the temperature is 1700 ℃, and the residence time is 10s. Other procedures and process parameters were the same as in example 1.
[ Comparative example 1]
The same preparation conditions as in example 1 were used, except that the carbonization pretreatment step was not included.
A Raman spectrometer manufactured by the company Horiba Jobin Yvon in france is adopted to carry out a test of Raman spectrum scanning on the fiber subjected to high-temperature carbonization treatment; wherein the Raman laser is 533nm, the laser power is 10mW, the exposure time is 10s, the accumulated exposure times are 5, and the output power is 50%; then, the Raman spectral lines of the materials are respectively obtained to obtain A N、AD and A G of a D peak, an N peak and a G peak; finally substituting the obtained product into a calculation formula: and R= (A D+AN)/AG) to obtain the structural nitrogen-carbon ratio of the polyacrylonitrile-based carbon fiber, and finally graphitizing the carbon fiber at a higher temperature, wherein the treatment temperature is 2400 ℃, the heat treatment time is 90s, the draft ratio is 5%, and the mechanical property test is carried out on the carbon fiber bundle filaments according to the national standard GB/T25749-2011, and the test result is shown in Table 1.
[ Comparative example 2]
The laser power for raman test was 40mW, the output power was 100%, the exposure time was 60s, the cumulative exposure time was 10, and other operating steps and process parameters were the same as comparative example 1, but the correct raman data was not successfully obtained. This is because the full power output in comparative example 2 resulted in high laser intensity and relatively easy ablation of the carbon fiber surface, and the physical properties of the sample test points were changed, so that accurate raman data could not be successfully obtained. The mechanical properties of the carbon fiber bundles were tested according to the national standard GB/T25749-2011, and the test results are shown in Table 1.
[ Comparative example 3]
The carbonization pretreatment is carried out between low-temperature carbonization and high-temperature carbonization, the temperature is 1000 ℃, and the residence time is 2s. Other procedures and process parameters were the same as in example 1. The mechanical properties of the carbon fiber bundles were tested according to the national standard GB/T25749-2011, and the test results are shown in Table 1.
[ Comparative example 4]
The carbonization pretreatment is carried out between low-temperature carbonization and high-temperature carbonization, the temperature is 1700 ℃, and the residence time is 30s. Other procedures and process parameters were the same as in example 1.
Comparative example 4 failed to collect samples, so there was no specific carbon fiber mechanical property data and carbon fiber structural nitrogen to carbon ratio R values.
The values of the nitrogen-carbon ratio R of the polyacrylonitrile carbon fibers obtained in the above comparative examples and the results of the mechanical properties (including tensile strength and tensile modulus) of the final polyacrylonitrile-based graphitized carbon fibers are shown in table 1.
TABLE 1
In the invention, the smaller the structural nitrogen-carbon ratio R, the smaller the corresponding carbon fiber defect, the larger the corresponding tensile strength (MPa) and tensile modulus (GPa), namely the better the mechanical properties of the prepared graphitized carbon fiber. As can be seen from the examples 1 and 1 of the present invention, the tensile strength and tensile modulus of the graphitized carbon fiber prepared in example 1 are both significantly increased after the carbonization pretreatment step compared with that of comparative example 1, and the mechanical properties of the graphitized carbon fiber are better.
The invention has been described in detail in connection with the specific embodiments and exemplary examples thereof, but such description is not to be construed as limiting the invention. It will be understood by those skilled in the art that various equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its embodiments without departing from the spirit and scope of the present invention, and these fall within the scope of the present invention. The scope of the invention is defined by the appended claims.
Claims (14)
1. The structural nitrogen-carbon ratio R of the polyacrylonitrile-based carbon fiber is 0<R to be less than or equal to 3.5;
The structural nitrogen-carbon ratio r= (a D+AN)/AG;
Wherein A N is the product of the Y-axis coordinate corresponding to the spectral peak of the N peak of the Raman spectrum test curve and the half-peak width of the N peak;
A D is the product of the Y-axis coordinate corresponding to the spectral peak of the D peak of the Raman spectrum test curve and the half-peak width of the D peak;
A G is the product of the Y-axis coordinate corresponding to the spectral peak of the G peak of the Raman spectrum test curve and the half-peak width of the G peak.
2. The polyacrylonitrile-based carbon fiber according to claim 1, wherein:
The structural nitrogen-carbon ratio 0<R is less than or equal to 3.2.
3. The polyacrylonitrile-based carbon fiber according to claim 1, wherein:
The spectrum peak corresponding to the A N is the spectrum peak of the Raman characteristic peak with the Raman shift coordinate range of 1500-1540 cm -1, and is preferably 1510-1530 cm -1;
The spectrum peak corresponding to A D is the spectrum peak of the Raman characteristic peak with the Raman displacement coordinate range of 1320-1380 cm -1, preferably 1355-1370 cm -1;
The spectrum peak corresponding to A G is the spectrum peak of Raman characteristic peak with the Raman shift coordinate range of 1575-1620 cm -1, preferably 1590-1620 cm -1.
4. The polyacrylonitrile-based carbon fiber according to claim 1, wherein:
The laser wavelength range of the laser used in the Raman spectrum test is 510-640 nm; and/or the number of the groups of groups,
The power of the laser is 5-15 mW; and/or the number of the groups of groups,
The range of the accumulated exposure time is 1-20 s; and/or the number of the groups of groups,
The accumulated exposure times are 1 to 5 times; and/or the number of the groups of groups,
During testing, the output rate of the laser power is 50-100%.
5. The preparation method of the polyacrylonitrile-based carbon fiber comprises the following steps:
when the polyacrylonitrile-based carbon fiber is prepared, a carbonization pretreatment step is added between low-temperature carbonization treatment and high-temperature carbonization treatment;
Preferably for the preparation of the polyacrylonitrile-based carbon fiber as claimed in any of claims 1 to 4.
6. The method for preparing polyacrylonitrile-based carbon fiber according to claim 5, wherein:
The temperature of the carbonization pretreatment is higher than that of the high-temperature carbonization treatment; and/or the number of the groups of groups,
The carbonization pretreatment time is lower than the high-temperature carbonization treatment time;
Preferably, the method comprises the steps of,
The carbonization pretreatment temperature is 1400-1700 ℃; preferably 1550-1700 ℃; and/or the number of the groups of groups,
The carbonization pretreatment time is 10-20 seconds; preferably 10 to 15 seconds; and/or the number of the groups of groups,
The treatment atmosphere is an inert atmosphere.
7. The method for preparing polyacrylonitrile-based carbon fiber according to claim 5, wherein:
the method also comprises pre-oxidation treatment of the precursor before the low-temperature carbonization treatment;
Preferably, the method comprises the steps of,
The precursor is polyacrylonitrile precursor; and/or the number of the groups of groups,
The temperature of the pre-oxidation treatment is 170-280 ℃, the total pre-oxidation time is not more than 120min, the treatment atmosphere is air atmosphere, and the draft ratio is 0-6%; preferably 0 to 3%;
More preferably, the process is carried out,
The polyacrylonitrile precursor is spun by wet spinning or dry-jet wet spinning; and/or the number of the groups of groups,
The polyacrylonitrile precursor is 3-24K.
8. The method for preparing polyacrylonitrile-based carbon fiber according to claim 5, wherein:
the temperature of the low-temperature carbonization treatment is 300-800 ℃; and/or the number of the groups of groups,
The total time of the low-temperature carbonization treatment is 2-6 min; and/or the number of the groups of groups,
The draft ratio is 0 to 6 percent; and/or the number of the groups of groups,
The treatment atmosphere is an inert atmosphere.
9. The method for preparing polyacrylonitrile-based carbon fiber according to claim 5, wherein:
the temperature of the high-temperature carbonization treatment is 1000-1400 ℃; and/or the number of the groups of groups,
The total time of the high-temperature carbonization treatment is 1-3 min; and/or the number of the groups of groups,
The draft ratio is-4 to-1 percent; and/or the number of the groups of groups,
The treatment atmosphere is an inert atmosphere.
10. Use of the polyacrylonitrile-based carbon fiber according to any one of claims 1 to 4 or the polyacrylonitrile-based carbon fiber prepared by the preparation method according to any one of claims 5 to 9 for preparing graphitized carbon fiber.
11. A method for preparing graphitized carbon fiber, comprising the following steps:
graphitizing the polyacrylonitrile-based carbon fiber to obtain the graphitized carbon fiber, wherein the graphitized carbon fiber is preferably the polyacrylonitrile-based carbon fiber prepared by the preparation method of any one of claims 1 to 4 or any one of claims 5 to 9.
12. The method for producing graphitized carbon fiber according to claim 11, wherein:
the temperature of the graphitization treatment is 2200-2500 ℃; and/or the number of the groups of groups,
The graphitization treatment time is 1-5 min; and/or the number of the groups of groups,
The draft ratio is 5-10%;
the treatment atmosphere is an inert atmosphere.
13. Graphitized carbon fiber produced by the process for producing graphitized carbon fiber according to any one of claims 11 to 12, preferably,
The tensile strength of the graphitized carbon fiber is more than or equal to 4000MPa, preferably more than or equal to 4288MPa; and/or the number of the groups of groups,
The tensile modulus is equal to or greater than 448GPa, preferably equal to or greater than 455GPa.
14. Use of graphitized carbon fibers prepared by the preparation method according to any one of claims 11 to 12 or graphitized carbon fibers according to claim 13 in high strength materials.
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