Method for testing carbonization degree of carbon fiber
By combining X-ray photoelectron spectroscopy and Raman spectroscopy, the surface and structural information of carbon fibers are measured, and a test model for the degree of carbonization of carbon fibers is established. This solves the problem of incomplete evaluation in existing technologies, and realizes rapid and accurate evaluation of the degree of carbonization of carbon fibers, supporting quality control and grading on the production line.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-03
- Publication Date
- 2026-04-10
AI Technical Summary
Existing technologies lack a method to comprehensively evaluate the degree of carbonization of high-modulus carbon fibers by combining surface chemical information with microstructure information, resulting in an incomplete and inaccurate evaluation.
By combining X-ray photoelectron spectroscopy and Raman spectroscopy, the percentages of nitrogen atoms to carbon atoms, oxygen atoms to carbon atoms, and the integral intensity ratio of the D peak and G peak on the carbon fiber surface are measured to establish a test model for the degree of carbonization of carbon fibers, thereby achieving a comprehensive evaluation of the degree of carbonization of carbon fibers.
A rapid and non-destructive method for testing the degree of carbonization of carbon fibers is provided, which enables random sampling of carbon fiber products on the production line, improving the accuracy of quality control and grading.
Smart Images
Figure CN121830758A_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to the field of carbon fiber material characterization, and in particular to a method for testing the degree of carbonization of carbon fibers. Background Technology
[0002] High-modulus carbon fiber refers to a type of carbon fiber that has undergone high-temperature graphitization treatment (typically ≥1800℃) and possesses a high tensile modulus (typically ≥350 GPa). Its preparation process typically includes pre-oxidation, carbonization, and high-temperature graphitization of the precursor (such as polyacrylonitrile). During this process, non-carbon elements (such as N, H, and O) in the carbon fiber are gradually removed, the carbon network planes continuously grow, and the graphite-like microcrystalline structure tends to be perfected, ultimately achieving high-modulus properties. The final degree of this process (i.e., the degree of carbonization / graphitization) directly determines the core properties of the carbon fiber, such as its modulus, thermal conductivity, and electrical conductivity. Currently, methods for evaluating the degree of carbonization of carbon fibers lack a comprehensive evaluation method that combines surface chemical information with microstructural information to comprehensively assess the degree of carbonization of high-modulus carbon fibers. Summary of the Invention
[0003] To address the problems existing in related technologies, this disclosure provides a method for testing the degree of carbonization of carbon fibers, the method comprising: The surface of the carbon fiber to be tested is tested to obtain a first ratio of the percentage of nitrogen atoms to carbon atoms and a second ratio of the percentage of oxygen atoms to carbon atoms on the surface of the carbon fiber to be tested. Raman spectroscopy was performed on the carbon fiber to be tested to obtain the third ratio of the integrated intensity of the D peak to the integrated intensity of the G peak of the carbon fiber to be tested. Based on the first ratio, the second ratio, the third ratio, and the test model for the degree of carbonization of carbon fiber, the graphitization index of the carbon fiber to be tested is determined to determine the degree of carbonization of the carbon fiber to be tested.
[0004] In some embodiments of this disclosure, testing the surface of the carbon fiber to be tested to obtain a first ratio of nitrogen atoms to carbon atoms and a second ratio of oxygen atoms to carbon atoms on the surface of the carbon fiber to be tested includes: The surface of the carbon fiber under test was tested by X-ray photoelectron spectroscopy to obtain C1s, N1s and O1s spectra. Based on the C1s spectrum, the N1s spectrum, and the O1s spectrum, determine the first ratio of nitrogen atoms to carbon atoms and the second ratio of oxygen atoms to carbon atoms on the surface of the carbon fiber to be tested.
[0005] In some embodiments of this disclosure, the step of performing Raman spectroscopy on the carbon fiber to be tested to obtain a third ratio between the integrated intensity of the D peak and the integrated intensity of the G peak of the carbon fiber to be tested includes: Raman spectroscopy was performed on the carbon fiber under test at a preset wavelength, and the D peak and G peak of the carbon fiber under test were collected to obtain the Raman spectrum of the carbon fiber under test. The Raman spectrum is processed to determine the integrated intensity of the D peak and the integrated intensity of the G peak, and a third ratio of the integrated intensity of the D peak and the integrated intensity of the G peak is calculated.
[0006] In some embodiments of this disclosure, the processing of the Raman spectrum includes: Baseline correction and Lorentz peak fitting were performed on the Raman spectrum.
[0007] In some embodiments of this disclosure, the preset wavelength is 530~535nm; or... The preset wavelength is 630~635nm.
[0008] In some embodiments of this disclosure, before testing the surface of the carbon fiber to be tested, the testing method further includes: The carbon fiber to be tested is ultrasonically cleaned using a preset solvent to remove sizing agent and / or contaminants from its surface.
[0009] In some embodiments of this disclosure, the preset solvent includes at least one of acetone, ethanol, or deionized water.
[0010] In some embodiments of this disclosure, the testing method further includes: Provide several carbon fiber standards with known tensile moduli; The surface of each of the carbon fiber standards is tested to obtain the first ratio and the second ratio of the surface of each of the carbon fiber standards; Raman spectroscopy was performed on each of the carbon fiber standards to obtain the third ratio for each of the carbon fiber standards; Using the tensile modulus of each carbon fiber standard as the dependent variable and the first ratio, second ratio, and third ratio of each carbon fiber standard as independent variables, a test model for the degree of carbonization of the carbon fiber is established using a multiple regression analysis method.
[0011] In some embodiments of this disclosure, the graphitization index of the carbon fiber under test is positively correlated with the tensile modulus of the carbon fiber under test.
[0012] In some embodiments of this disclosure, the heat treatment temperature of the carbon fiber standard is 1500~3200℃.
[0013] The beneficial effects of this disclosure include, but are not limited to: the carbon fiber carbonization degree testing method provided in this disclosure combines the first ratio of nitrogen atoms to carbon atoms and the second ratio of oxygen atoms to carbon atoms in the surface chemical state of the carbon fiber under test with the third ratio of the integrated intensity of the D peak and the integrated intensity of the G peak in the Raman spectrum of the carbon fiber under test. This reveals the evolution essence of the carbon fiber under test at high temperatures from two dimensions, resulting in a more comprehensive and profound evaluation of the carbonization degree of the carbon fiber under test. Furthermore, this testing method is fast and non-destructive to the carbon fiber under test, which is beneficial for random inspection of carbon fiber products on the production line, providing a direct basis for the quality control and grading of carbon fiber products.
[0014] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description
[0015] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and, together with the description, serve to explain the principles of these embodiments. In these drawings, similar reference numerals are used to denote similar elements. The drawings described below are some embodiments of the present disclosure, but not all embodiments. Other drawings will be readily available to those skilled in the art based on these drawings without inventive effort.
[0016] Figure 1 This is a schematic flowchart of a method for testing the degree of carbonization of carbon fibers, which is an exemplary embodiment of this disclosure. Figure 2 This is a schematic diagram of a method for testing the degree of carbonization of carbon fibers, which is another exemplary embodiment of this disclosure. Figure 3 This is a schematic diagram of a method for testing the degree of carbonization of carbon fibers, which is another exemplary embodiment of this disclosure. Figure 4 This is a schematic diagram of a method for testing the degree of carbonization of carbon fibers, which is another exemplary embodiment of this disclosure. Detailed Implementation
[0017] To make the objectives, technical solutions, and advantages of this disclosure clearer, the technical solutions of this disclosure will be clearly and completely described below in conjunction with the embodiments of this disclosure. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this disclosure can be arbitrarily combined with each other.
[0018] The final degree of high-temperature graphitization of carbon fiber directly determines its core properties such as modulus, thermal conductivity, and electrical conductivity. Currently, the main methods used in the industry to evaluate the degree of carbonization of carbon fiber include: X-ray diffraction (XRD): This method measures the interplanar spacing (d) of crystal planes. 002 ) and crystallite size (L c This method is used to evaluate the graphitization degree of carbon fibers. It is a standard method for measuring bulk structure, but it is not sensitive to changes in surface structure, and the equipment is expensive and the testing and analysis cycle is long.
[0019] Resistivity method: This method indirectly reflects the degree of graphitization of carbon fibers by measuring their resistance; the higher the degree of graphitization, the lower the resistivity. This method is simple and quick, but the measurement results are highly susceptible to the surface condition of the carbon fibers, contact resistance, and environmental factors, resulting in poor repeatability and accuracy.
[0020] It is noteworthy that during the high-temperature processing of high-modulus carbon fibers, the elemental composition and microstructure evolution of the carbon fibers change synergistically. The residual amounts of non-carbon elements (N, O) decrease sharply and tend to stabilize with increasing temperature; this change is more sensitive than the bulk structure parameters at certain stages. Current technology lacks a method to comprehensively evaluate the degree of carbonization of high-modulus carbon fibers by combining surface chemical information with microstructure information.
[0021] Based on this, this disclosure provides a method for testing the degree of carbonization of carbon fibers. It combines a first ratio of the percentage of nitrogen atoms to carbon atoms and a second ratio of the percentage of oxygen atoms to carbon atoms in the surface chemical state of the carbon fiber under test with a third ratio of the integrated intensity of the D peak and the integrated intensity of the G peak in the Raman spectrum of the carbon fiber under test. This method reveals the evolutionary nature of the carbon fiber under test at high temperatures from two dimensions, providing a more comprehensive and profound evaluation of the degree of carbonization. Furthermore, this testing method is fast and non-destructive to the carbon fiber under test, which is beneficial for random sampling of carbon fiber products on the production line, providing direct evidence for the quality control and grading of carbon fiber products.
[0022] An exemplary embodiment of this disclosure provides a method for testing the degree of carbonization of carbon fibers, such as... Figure 1 As shown, the test method includes: S100. Test the surface of the carbon fiber to be tested to obtain the first ratio of nitrogen atoms to carbon atoms and the second ratio of oxygen atoms to carbon atoms on the surface of the carbon fiber to be tested.
[0023] The degree of carbonization of carbon fibers is closely related to their surface chemical state. For example, the content of non-carbon elements (N, O) on the surface of carbon fibers affects the interfacial properties of the fibers. In step S100, the surface of the carbon fiber to be tested is tested to obtain a first ratio of the percentage of nitrogen atoms to carbon atoms and a second ratio of the percentage of oxygen atoms to carbon atoms on the surface of the carbon fiber to be tested. This allows for the quantification of low-content N and O elements, taking advantage of the characteristics of high-modulus carbon fibers having extremely low non-carbon element content and few structural defects, thereby improving the ability to distinguish subtle differences in the degree of carbonization of carbon fibers in the high-temperature range (≥1800℃).
[0024] S200. Raman spectroscopy is performed on the carbon fiber to be tested to obtain the third ratio of the integrated intensity of the D peak to the integrated intensity of the G peak of the carbon fiber to be tested.
[0025] The degree of carbonization of carbon fiber is related to its internal graphite microcrystalline structure. In step S200, Raman spectroscopy is performed on the carbon fiber to be tested to obtain the D peak (1350 cm⁻¹). -1 The integral intensity (near) and the G peak (1580 cm) -1 The third ratio of the integral intensity (R = I) in the vicinity D / I G ( ), which can characterize the defect density of carbon fibers.
[0026] S300. Based on the first ratio, second ratio, third ratio and the test model of carbon fiber carbonization degree, determine the graphitization degree index of the carbon fiber to be tested, so as to determine the carbonization degree of the carbon fiber to be tested.
[0027] The carbon fiber carbonization degree test model converts the first ratio, second ratio, and third ratio into the graphitization degree index of the carbon fiber to be tested, thereby determining the carbonization degree of the carbon fiber to be tested, which greatly simplifies the determination of the carbonization degree of carbon fiber.
[0028] The carbon fiber carbonization degree testing method provided in this embodiment combines the first ratio of nitrogen to carbon atoms and the second ratio of oxygen to carbon atoms in the surface chemical state of the carbon fiber under test with the third ratio of the integrated intensity of the D peak and the integrated intensity of the G peak in the Raman spectrum of the carbon fiber under test. This reveals the evolutionary nature of the carbon fiber under test at high temperatures from two dimensions, resulting in a more comprehensive and profound evaluation of the carbonization degree. Furthermore, this testing method is fast and non-destructive to the carbon fiber under test, which is beneficial for random sampling of carbon fiber products on the production line, providing direct evidence for the quality control and grading of carbon fiber products.
[0029] In an exemplary embodiment, in step S100, the surface of the carbon fiber to be tested is tested to obtain a first ratio of the percentage of nitrogen atoms to carbon atoms and a second ratio of the percentage of oxygen atoms to carbon atoms on the surface of the carbon fiber to be tested, such as... Figure 2 As shown, it includes: S110. The surface of the carbon fiber under test was tested by X-ray photoelectron spectroscopy to obtain C1s, N1s and O1s spectra.
[0030] X-ray photoelectron spectroscopy (XPS) is a surface-sensitive quantitative elemental analysis technique that can quantify low levels of N and O elements, taking advantage of the extremely low non-carbon element content and few structural defects on the surface of high-modulus carbon fibers. In step S110, the surface of the carbon fiber under test is tested using XPS to obtain C1s, N1s, and O1s spectra, providing a basis for determining the nitrogen and carbon atom content on the surface of the carbon fiber under test.
[0031] S120. Based on the C1s spectrum, N1s spectrum, and O1s spectrum, determine the first ratio of nitrogen atoms to carbon atoms and the second ratio of oxygen atoms to carbon atoms on the surface of the carbon fiber to be tested.
[0032] Based on the C1s, N1s, and O1s spectra, the first and second ratios are determined to quantify the low N and O content on the surface of the carbon fiber to be tested.
[0033] In this embodiment, X-ray photoelectron spectroscopy is used to determine the first ratio of nitrogen atoms to carbon atoms and the second ratio of oxygen atoms to carbon atoms on the surface of the carbon fiber to be tested. This allows for the quantification of low-content N and O elements, taking advantage of the extremely low content of non-carbon elements and few structural defects on the surface of high-modulus carbon fibers. This improves the ability to distinguish subtle differences in the degree of carbonization of carbon fibers in the high-temperature range (≥1800℃).
[0034] In an exemplary embodiment, in step S200, Raman spectroscopy is performed on the carbon fiber to be tested to obtain a third ratio of the integrated intensity of the D peak to the integrated intensity of the G peak of the carbon fiber to be tested, such as... Figure 3 As shown, it includes: S210. Perform Raman spectroscopy on the carbon fiber to be tested at a preset wavelength, collect the D peak and G peak of the carbon fiber to be tested, and obtain the Raman spectrum of the carbon fiber to be tested.
[0035] In this step, multi-point Raman spectroscopy scanning can be performed on the same carbon fiber under test at a preset wavelength, and the data can be collected at 1350 cm⁻¹. -1 Nearby D peak and at 1580 cm -1 The Raman spectrum of the carbon fiber to be tested was obtained from the nearby G peak.
[0036] S220. Process the Raman spectrum to determine the integrated intensity of peak D and peak G, and calculate the third ratio of the integrated intensity of peak D to peak G.
[0037] The third ratio of the integrated intensity of peak D to the integrated intensity of peak G (R = I) D / I G (R) is a sensitive parameter characterizing the degree of graphitization of carbon fibers. This is achieved by calculating the integrated intensity of the D peak and the integrated intensity of the G peak, and then calculating the third ratio (R = I) between the integrated intensities of the D peak and the G peak. D / I G ( ), which can characterize the defect density of carbon fibers.
[0038] In one exemplary embodiment, processing the Raman spectrum includes: baseline correction and Lorentz peak fitting of the Raman spectrum.
[0039] Baseline correction of Raman spectra eliminates interference and ensures the accuracy of the calculated integrated intensities of peaks D and G. Furthermore, Lorentz peak fitting of Raman spectra is an effective method for separating overlapping peaks and accurately calculating their individual integrated intensities. Baseline correction and Lorentz peak fitting of Raman spectra yield high-quality, comparable third ratios (R = I). D / I G This fundamentally ensures the accuracy and stability of the test for the degree of carbonization of the carbon fiber under test.
[0040] In one exemplary embodiment, the preset wavelength is 530~535nm.
[0041] Different laser wavelengths significantly affect the Raman signal intensity and resonance effect of the carbon fiber under test. When the preset wavelength is 530~535nm, it can generate strong and clearly defined D-peak and G-peak signals for the carbon fiber under test, while effectively avoiding damage to the carbon fiber sample that may be caused by excessive laser energy. For example, the preset wavelength can be 530 nm, 532 nm, or 535 nm, or any value between the exemplary wavelengths, such as any value between 531~534 nm.
[0042] In one exemplary embodiment, the preset wavelength is 630~635nm.
[0043] Different laser wavelengths significantly affect the Raman signal intensity and resonance effect of the carbon fiber under test. When the preset wavelength is 630~635nm, it can generate strong and clearly defined D-peak and G-peak signals of the carbon fiber under test, while effectively avoiding damage to the carbon fiber sample that may be caused by excessive laser energy. For example, the preset wavelength can be 630 nm, 633 nm, or 635 nm, or any value between the exemplary wavelengths, such as any value between 631~634 nm.
[0044] In an exemplary embodiment, before testing the surface of the carbon fiber to be tested, the testing method further includes: ultrasonically cleaning the carbon fiber to be tested with a preset solvent to remove sizing agent and / or contaminants from the surface of the carbon fiber to be tested.
[0045] During the production process, carbon fiber surfaces are typically coated with sizing agents and may also become contaminated with environmental pollutants. These substances can interfere with XPS surface analysis results and Raman spectral signals. Before testing the surface of the carbon fiber, ultrasonic cleaning with a pre-set solvent is performed to remove the sizing agent and contaminants from the carbon fiber surface. This eliminates the interference of the sizing agent and contaminants on the test results, improving their reliability and repeatability.
[0046] In one exemplary embodiment, the preset solvent includes at least one of acetone, ethanol, or deionized water.
[0047] Acetone and ethanol are highly efficient organic solvents that can effectively dissolve and remove common sizing agents and organic contaminants from the surface of the carbon fibers being tested, while deionized water can be used to remove water-soluble impurities. These solvents are readily available, inexpensive, and highly volatile, leaving no residue on the surface of the carbon fibers being tested, nor corroding or damaging their structure, ensuring that no new errors are introduced during ultrasonic cleaning that could interfere with the accuracy of the test results.
[0048] In one exemplary embodiment, such as Figure 4 As shown, the test methods for the degree of carbonization of carbon fibers also include: S400 provides several carbon fiber standards with known tensile moduli.
[0049] S500. Test the surface of each carbon fiber standard to obtain the first ratio and the second ratio of the surface of each carbon fiber standard.
[0050] S600. Raman spectroscopy tests were performed on each carbon fiber standard to obtain the third ratio of each carbon fiber standard.
[0051] S700. Using the tensile modulus of each carbon fiber standard as the dependent variable and the first ratio, second ratio, and third ratio of each carbon fiber standard as independent variables, a test model for the degree of carbonization of carbon fiber is established using multiple regression analysis.
[0052] In this embodiment, several carbon fiber standards with known tensile moduli are provided, and their corresponding first, second, and third ratios are collected. A test model for the degree of carbonization of carbon fibers is established using a multiple regression analysis method. This test model clearly establishes a quantitative relationship between the surface / structure parameters (independent variables) and tensile modulus (dependent variable) of carbon fibers. According to this test model, for a given carbon fiber to be tested, only its first, second, and third ratios need to be measured to quickly determine its corresponding tensile modulus, thereby determining its corresponding graphitization index and achieving rapid determination of the degree of carbonization of the carbon fiber to be tested.
[0053] It should be noted that in the process of establishing the test model for the degree of carbonization of carbon fiber, the determination of the first ratio, the second ratio, and the third ratio for each carbon fiber standard should follow the same steps and conditions as the process of determining the degree of carbonization of carbon fiber, so as to ensure the reliability of the determination results of the degree of carbonization of carbon fiber determined by the test model.
[0054] In one exemplary embodiment, the graphitization index of the carbon fiber under test is positively correlated with the tensile modulus of the carbon fiber under test.
[0055] The graphitization degree index (GDI) of the carbon fiber under test is positively correlated with the tensile modulus of the carbon fiber. Therefore, for a certain carbon fiber under test, it is only necessary to measure its first ratio, second ratio, and third ratio. Based on the above test model of carbon fiber carbonization degree, its corresponding tensile modulus can be quickly determined by the test model, and then its corresponding graphitization degree index can be determined. The degree of carbonization / graphitization of the carbon fiber can be directly evaluated based on the value of the graphitization degree index, so as to realize the rapid determination of the degree of carbonization / graphitization of the carbon fiber under test.
[0056] In an exemplary embodiment, in step S300, the graphitization index of the carbon fiber to be tested is determined according to the first ratio, the second ratio, the third ratio, and the test model of carbon fiber carbonization degree, so as to determine the carbonization degree of the carbon fiber to be tested. This includes: determining the tensile modulus of the carbon fiber to be tested according to the first ratio, the second ratio, the third ratio, and the test model of carbon fiber carbonization degree. The graphitization index of the carbon fiber to be tested is positively correlated with the tensile modulus of the carbon fiber to be tested. Therefore, a high tensile modulus of the carbon fiber to be tested indicates a high graphitization index, which in turn indicates a high degree of carbonization. Conversely, a low tensile modulus of the carbon fiber to be tested indicates a low graphitization index, which in turn indicates a low degree of carbonization.
[0057] For example, as the graphitization index of the carbon fiber under test increases from 50 to 70, and then to 90, its corresponding tensile modulus also increases from 250 GPa to 400 GPa, and then to 600 GPa. For instance, during the testing of the carbonization degree of the carbon fiber under test, a preset threshold for the tensile modulus can be set, such as a maximum and a minimum threshold. When the tensile modulus of the carbon fiber under test, determined by the carbon fiber carbonization degree testing model, is higher than the maximum threshold or lower than the minimum threshold, it indicates that its corresponding graphitization index is too high or too low. Accordingly, the carbonization degree of the carbon fiber under test is determined to be too high or too low, and does not meet production requirements. Conversely, when the tensile modulus of the carbon fiber under test, determined by the carbon fiber carbonization degree testing model, is between the maximum and minimum thresholds, it indicates that its corresponding graphitization index is appropriate. Accordingly, the carbonization degree of the carbon fiber under test is determined to be appropriate, and meets production requirements.
[0058] In one exemplary embodiment, the heat treatment temperature of the carbon fiber standard is 1500~3200℃.
[0059] The temperature range of 1500℃ to 3200℃ is the range from moderate carbonization to high graphitization of carbon fibers. By selecting carbon fiber standards within this heat treatment temperature range, the established test model for the degree of carbonization of carbon fibers can effectively determine the tensile modulus of the carbon fibers under test within a wide range of heat treatment temperatures, and thus determine their degree of carbonization. For example, the heat treatment temperature of carbon fiber standards can also be from 1800℃ to 3000℃.
[0060] To more clearly explain the technical solutions provided by the exemplary embodiments of this disclosure, a specific example of the test method for the degree of carbonization of carbon fibers provided by the exemplary embodiments of this disclosure is given.
[0061] Four sets of carbon fiber standards with known tensile modulus are provided.
[0062] The surface of each carbon fiber standard was tested using X-ray photoelectron spectroscopy to obtain a first ratio of nitrogen atoms to carbon atoms and a second ratio of oxygen atoms to carbon atoms on the surface of each carbon fiber standard.
[0063] Raman spectroscopy was performed on each carbon fiber standard at a laser wavelength of 633 nm, and the third ratio (R = I) of the integrated intensity of the D peak and the integrated intensity of the G peak for each carbon fiber standard was obtained. D / I G ).
[0064] The tensile modulus (E), first ratio (N / C), second ratio (O / C), and third ratio (R) of the four groups of carbon fiber standards are shown in Table 1 below: Table 1
[0065] Using the tensile modulus (E) of each carbon fiber standard as the dependent variable, and the first ratio (N / C), second ratio (O / C), and third ratio (R) of each carbon fiber standard as independent variables, a test model for the degree of carbonization of carbon fiber was established using multiple regression analysis, as follows: E = 792.6 - 63.7 (N / C)-183.9 (O / C)-197.3 (R).
[0066] The correlation coefficient R of the above test model equation 2 >0.99.
[0067] The carbon fiber to be tested is ultrasonically cleaned using a preset solvent to remove sizing agent and / or contaminants from its surface.
[0068] The surface of the carbon fiber under test was tested using an X-ray photoelectron spectrometer to obtain C1s, N1s, and O1s spectra.
[0069] Based on the C1s, N1s, and O1s spectra, the first ratio (N / C) of nitrogen atoms to carbon atoms on the surface of the carbon fiber to be tested was determined to be 1.57, and the second ratio (O / C) of oxygen atoms to carbon atoms was determined to be 0.54.
[0070] Raman spectroscopy was performed on the carbon fiber under a 633nm laser wavelength. The D peak and G peak of the carbon fiber were collected to obtain the Raman spectrum of the carbon fiber.
[0071] Baseline correction and Lorentz peak fitting were performed on the Raman spectrum to determine the integrated intensity of peak D and peak G, and the third ratio (R) of the integrated intensity of peak D and peak G was calculated to be 0.59.
[0072] Based on the first ratio of 1.57, the second ratio of 0.54, the third ratio of 0.59, and the test model for the degree of carbon fiber carbonization, E=792.6-63.7 (N / C)-183.9 (O / C)-197.3 (R), the tensile modulus of the carbon fiber to be tested was calculated to be 476 GPa.
[0073] The graphitization degree index (GDI) is determined by the tensile modulus of the carbon fiber under test, thereby evaluating the degree of carbonization of the carbon fiber under test.
[0074] The above-described contents can be implemented individually or in various combinations, and all such variations are within the scope of this disclosure.
[0075] Finally, it should be noted that in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.
[0076] The above embodiments are only used to illustrate the technical solutions of this disclosure, and are not intended to limit it. Although this disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this disclosure.
Claims
1. A method for testing the degree of carbonization of carbon fibers, characterized in that, The testing method includes: The surface of the carbon fiber to be tested is tested to obtain a first ratio of the percentage of nitrogen atoms to carbon atoms and a second ratio of the percentage of oxygen atoms to carbon atoms on the surface of the carbon fiber to be tested. Raman spectroscopy was performed on the carbon fiber to be tested to obtain the third ratio of the integrated intensity of the D peak to the integrated intensity of the G peak of the carbon fiber to be tested. Based on the first ratio, the second ratio, the third ratio, and the test model for the degree of carbonization of carbon fiber, the graphitization index of the carbon fiber to be tested is determined to determine the degree of carbonization of the carbon fiber to be tested.
2. The method for testing the degree of carbonization of carbon fibers according to claim 1, characterized in that, The surface of the carbon fiber to be tested is tested to obtain a first ratio of nitrogen atoms to carbon atoms and a second ratio of oxygen atoms to carbon atoms on the surface of the carbon fiber to be tested, including: The surface of the carbon fiber under test was tested by X-ray photoelectron spectroscopy to obtain C1s, N1s and O1s spectra. Based on the C1s spectrum, the N1s spectrum, and the O1s spectrum, determine the first ratio of nitrogen atoms to carbon atoms and the second ratio of oxygen atoms to carbon atoms on the surface of the carbon fiber to be tested.
3. The method for testing the degree of carbonization of carbon fibers according to claim 1, characterized in that, The step of performing Raman spectroscopy on the carbon fiber to be tested, and obtaining the third ratio of the integrated intensity of the D peak to the integrated intensity of the G peak of the carbon fiber to be tested, includes: Raman spectroscopy was performed on the carbon fiber under test at a preset wavelength, and the D peak and G peak of the carbon fiber under test were collected to obtain the Raman spectrum of the carbon fiber under test. The Raman spectrum is processed to determine the integrated intensity of the D peak and the integrated intensity of the G peak, and a third ratio of the integrated intensity of the D peak and the integrated intensity of the G peak is calculated.
4. The method for testing the degree of carbonization of carbon fibers according to claim 3, characterized in that, The processing of the Raman spectrum includes: Baseline correction and Lorentz peak fitting were performed on the Raman spectrum.
5. The method for testing the degree of carbonization of carbon fibers according to claim 3, characterized in that, The preset wavelength is 530~535nm; or, The preset wavelength is 630~635nm.
6. The method for testing the degree of carbonization of carbon fibers according to claim 1, characterized in that, Before testing the surface of the carbon fiber to be tested, the test method further includes: The carbon fiber to be tested is ultrasonically cleaned using a preset solvent to remove sizing agent and / or contaminants from its surface.
7. The method for testing the degree of carbonization of carbon fiber according to claim 6, characterized in that, The preset solvent includes at least one of acetone, ethanol, or deionized water.
8. The method for testing the degree of carbonization of carbon fiber according to any one of claims 1-7, characterized in that, The testing method also includes: Provide several carbon fiber standards with known tensile moduli; The surface of each of the carbon fiber standards is tested to obtain the first ratio and the second ratio of the surface of each of the carbon fiber standards; Raman spectroscopy was performed on each of the carbon fiber standards to obtain the third ratio for each of the carbon fiber standards; Using the tensile modulus of each carbon fiber standard as the dependent variable and the first ratio, second ratio, and third ratio of each carbon fiber standard as independent variables, a test model for the degree of carbonization of the carbon fiber is established using a multiple regression analysis method.
9. The method for testing the degree of carbonization of carbon fiber according to claim 8, characterized in that, The graphitization index of the carbon fiber under test is positively correlated with the tensile modulus of the carbon fiber under test.
10. The method for testing the degree of carbonization of carbon fibers according to claim 8, characterized in that, The heat treatment temperature of the carbon fiber standard is 1500~3200℃.