A method for characterizing the graphitization degree of non-graphitic carbon materials

Abstract

The present application relates to carbon material detection technical field, disclose a kind of non-graphite carbon material graphitization degree characterization method, comprising the following steps: S1 standard substance selection;S2 gradient mixed sample preparation;S3 Raman spectrum test;S4 calibration curve establishment;S5 sample under test test;S6 graphitization degree calculation.The present application is greater than 99.9% of the ultra-pure graphite representative 100% graphite structure, coconut shell carbonization material represents 0% graphite structure, prepares different proportion homogeneous mixed sample, by Raman spectrum test to establish the linear calibration curve of value and graphitization degree and empirical formula, again test the value of sample under test and substitute into calculation graphitization degree.This method is accurate, fast, good repeatability, fills the technical blank of the graphitization degree quantitative characterization of this kind of special carbon material, provides reliable means for its research and development and production quality control.

Description

Technical Field

[0001] This invention relates to the field of graphitization degree characterization technology for non-graphite carbon materials, specifically a method for characterizing the graphitization degree of non-graphite carbon materials. Background Technology

[0002] The degree of graphitization is an important indicator characterizing the regularity of carbon atom arrangement in carbon materials, reflecting the perfection of the graphite crystal structure, and has a decisive influence on the physicochemical properties of carbon materials, such as electrical conductivity, thermal conductivity, and mechanical strength. Accurate determination of the degree of graphitization in carbon materials is of great significance for their research, development, production, and application.

[0003] Currently, the determination of graphitization degree mainly adopts the X-ray diffraction (XRD) method, and relevant standards include "SN / T5579-2023 Determination of graphitization degree of carbon materials by X-ray diffraction" and "YB / T6139.1-2023 Test methods for graphite anode materials Part 1: Determination of graphitization degree", etc.

[0004] The characterization of graphitization degree is based on the interlayer spacing calculated from the 2θ angle of XRD test analysis, which is then substituted into the formula G=(3.44-d002) / (3.44-3.354)x100% to obtain an accurate value. However, the above method is only applicable to graphitic carbon materials, or carbon materials with a graphite structure ratio greater than 95%. For non-graphitic carbon materials that simultaneously have a high proportion of graphite structure and defect or disordered structure, due to the broadening and asymmetry of their (002) diffraction peak, the interlayer spacing d002 obtained by XRD test often exceeds the theoretical value of 0.3440 nm for completely ungraphitized carbon materials, resulting in a negative calculated degree of graphitization and inaccurate results.

[0005] Raman spectroscopy is another commonly used method for characterizing the structure of carbon materials. It involves measuring the intensity ratio of the D peak to the G peak. This reflects the degree of defects and disorder in carbon materials. A higher value indicates more defects, higher disorder, and lower graphitization in the material. However, Raman spectroscopy can only obtain relative values. The ratio cannot be directly converted into a percentage value of graphitization degree, which limits its application in quantitative characterization.

[0006] Therefore, developing a method that can accurately characterize the graphitization degree of non-graphite carbon materials that simultaneously possess graphite structure and defect or disordered structure has become a technical problem that urgently needs to be solved in this field.

[0007] In view of this, the applicant conducted in-depth research on the above-mentioned issues, which led to this case. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a method for characterizing the degree of graphitization of non-graphite carbon materials, solving the technical problems that existing XRD methods cannot accurately characterize the degree of graphitization of non-graphite carbon materials and Raman spectroscopy cannot quantitatively calculate the degree of graphitization.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] A method for characterizing the graphitization degree of non-graphite carbon materials, characterized by comprising the following steps:

[0011] S1: Selection of Standard Materials: Ultrapure graphite with a purity greater than 99.9% was selected as the standard material with a 100% graphite structure, and carbonized coconut shell was selected as the standard material with a 0% graphite structure. Ultrapure graphite has a perfect graphite crystal structure, and its graphitization degree can be considered 100%; carbonized coconut shell has undergone high-temperature carbonization but has not been graphitized, and has a highly disordered structure, so its graphitization degree can be considered 0%.

[0012] S2: Gradient Mixed Sample Preparation: The two standard substances mentioned above are uniformly mixed in different mass ratios to prepare a series of homogeneous mixed samples with graphitization gradients.

[0013] S3: Raman spectroscopy test: Raman spectroscopy tests were performed on the above gradient mixed samples to obtain the intensity ratio of the D peak to the G peak of each mixed sample. .

[0014] S4: Calibration Curve Establishment: Using the degree of graphitization of the mixed sample as the ordinate, the corresponding... The x-axis is used to plot the calibration curve and fit it to obtain a linear empirical formula.

[0015] S5: Sample Testing: Perform Raman spectroscopy on the non-graphite carbon material under the same conditions to obtain its... value.

[0016] S6: Calculation of graphitization degree: Calculate the graphitization degree of the sample to be tested. Substituting the values ​​into the above linear empirical formula, the degree of graphitization of the sample to be tested is calculated.

[0017] Furthermore, in step S2, the graphitization gradient of the gradient mixed sample, that is, the mass percentage of the standard substance with 100% graphite structure in the gradient mixed sample, includes 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, and 100%.

[0018] Furthermore, in step S2, the specific method for uniform mixing is as follows: weigh the two standard substances according to the proportion and place them in an agate jar, add anhydrous alcohol and agate balls, grind them thoroughly on a planetary ball mill at a speed of 45±5Hz for 1 hour, and then dry them at 105℃ for 1 hour to remove the anhydrous alcohol.

[0019] Furthermore, the total weight of the mixed sample is 10g, accurate to 0.001g; the volume of anhydrous ethanol added is 100mL; and the agate balls have a diameter of 1mm and a quantity of 50.

[0020] Furthermore, in steps S3 and S5, the Raman spectroscopy test uses a 532nm laser with a laser power of 2mW. At least 100 sites are randomly detected for each sample, and the average value is taken as the sample's Raman spectroscopy result. value.

[0021] Furthermore, in step S4, the linear empirical formula takes the form: G = a × ( )+b, where G is the degree of graphitization (%), and a and b are constants obtained from the fitting.

[0022] This invention provides a method that has the following beneficial effects:

[0023] 1. This invention solves the problem of characterizing the graphitization degree of non-graphite carbon materials that simultaneously possess graphite structure and defect / disordered structure, filling a gap in the prior art. For non-graphite carbon materials with a graphite structure ratio between 1% and 95%, this method can provide accurate percentage values ​​for the graphitization degree.

[0024] 2. This invention utilizes Raman spectroscopy... The relative value was converted into the absolute value of the degree of graphitization, which fully leveraged the advantages of Raman spectroscopy in terms of speed, non-destructiveness, and micro-area analysis, while also achieving quantitative characterization.

[0025] 3. This invention uses a standard substance gradient mixing method to establish calibration curves. The method is simple, reliable, and has good repeatability. It is easy to promote and apply within enterprises, providing an effective technical means for the research and development and production quality control of non-graphite carbon materials.

[0026] 4. This invention expands the applicability of the graphitization degree testing method, no longer limited to high-purity graphite materials, and has good applicability to various carbon materials that have undergone partial graphitization treatment. Attached Figure Description

[0027] Figure 1 For graphitization degree and A trend graph of the values. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Preparation of standard materials: Ultrapure graphite with a purity greater than 99.9% was used as the standard material representing 100% graphite structure, and carbonized coconut shell material was used as the standard material representing 0% graphite structure. The carbonization temperature of the coconut shell material was 800℃ and the holding time was 2h. XRD test showed no graphite (002) diffraction peak, and the degree of graphitization was ≤0.1%. Before use, both materials were dried to constant weight in an oven at 105℃.

[0030] Gradient Mixed Sample Preparation: Using 10g (accurate to 0.001g) as the total weight, ultrapure graphite and coconut shell carbonized material were accurately weighed according to the mass ratios shown in Table 1 to form a series of standard mixed samples with different graphite structure proportions. The weighed carbon materials were placed in an agate jar, and 100mL of anhydrous ethanol and 50 agate balls with a particle size of 1mm were added. The jar was sealed and ground thoroughly on a planetary ball mill at a motor speed of 45±5Hz for 1 hour. After grinding, the mixed samples were removed and dried in an oven at 105℃ for 1 hour to obtain the various standard mixed samples.

[0031] Table 1: Preparation Ratio Table for Mixed Samples

[0032] Sample 1 0.000 10.000 0 Sample 2 0.500 9.500 5 Sample 3 1.000 9.000 10 Sample 4 1.500 8.500 15 Sample 5 2.000 8.000 20 Sample 6 2.500 7.500 25 Sample 7 3.000 7.000 30 Sample 8 3.500 6.500 35 Sample 9 4.000 6.000 40 Sample 10 4.500 5.500 45 Sample 11 5.000 5.000 50 Sample 12 5.500 4.500 55 Sample 13 6.000 4.000 60 Sample 14 6.500 3.500 65 Sample 15 7.000 3.000 70 Sample 16 7.500 2.500 75 Sample 17 8.000 2.000 80 Sample 18 8.500 1.500 85 Sample 19 9.000 1.000 90 Sample 20 9.500 0.500 95 Sample 21 10.000 0.000 100

[0033] Raman spectroscopy testing: Each standard mixture sample was laid flat on the sample cup of the Raman spectrometer and placed on the testing platform. A 532nm laser was used to randomly detect 100 sites on each sample, with a scanning range of 200μm × 200μm, a laser spot diameter of 1μm, and an integration time of 10s. 100 sites were then collected. The arithmetic mean of the values ​​is used as the sample value. The representative value was calculated, and the standard deviation was also calculated to measure the homogeneity of the sample. The test results are shown in Table 2.

[0034] Table 2: Raman spectra of mixed samples with different graphite structure proportions Value Statistics Table

[0035] Calibration curve establishment: The graphitization degree of the mixed sample is plotted on the ordinate, corresponding to... The x-axis is used to plot a calibration curve and fit it to obtain a linear empirical formula, which has the form: G = a × ( ) + b, where G is the degree of graphitization (%), and a and b are constants obtained from the fitting. In this embodiment, the specific form of the linear empirical formula is calculated to be G = -1.0941 × ( +1.0491, =0.9842. Graphitization degree and The trend relationship of the values ​​is shown in the appendix. Figure 1 As shown in the figure. The working curves show that the proportion of ultrapure graphite is related to... The values ​​generally show a good linear correlation in terms of trend, and an empirical formula can be obtained through linear regression for calculating the degree of graphitization of similar non-graphite carbon materials.

[0036] Test sample: The test sample is a non-graphite porous carbon material that has undergone graphitization treatment. The tested porous carbon material simultaneously exhibits a graphite structure and a defect / disordered structure. The test sample was tested under the same Raman spectroscopy conditions as in step S3, and its... The average value is 0.46. This... By referring to the data in Table 2 or substituting them into the regression equation of the working curve, the graphitization degree of the sample to be tested is found to be approximately 50%.

[0037] Method verification: Another batch of known ultrapure graphite and coconut shell carbonized material were used to prepare a mixed sample for verification according to the same steps. The proportion of ultrapure graphite was 0%, 25%, 50%, 75%, and 100%, respectively. The readings were verified by Table 1. The results showed that the deviation between the measured value and the prepared value did not exceed 5 percentage points. The accuracy and repeatability of the method were good. The test results are shown in Table 3.

[0038] Table 3 Raman spectra of the test samples Value Statistics Table

[0039]

[0040] Refer to the five sets of verification samples Figure 1 The trend relationship graph was used to obtain the graphitization degree value. The absolute deviation and average absolute deviation between the graphitization degree value and the prepared value were both within acceptable ranges. This indicates that the method has extremely high accuracy and repeatability, and can meet the requirements for accurate quantitative characterization of graphitization degree in non-graphite carbon materials.

[0041] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for characterizing the degree of graphitization of non-graphite carbon materials, characterized in that, Includes the following steps, S1: Selection of standard materials: Ultra-pure graphite with a purity greater than 99.9% is selected as the standard material with a 100% graphite structure, and coconut shell carbonized material is selected as the standard material with a 0% graphite structure. S2: Gradient Mixed Sample Preparation: The two standard substances mentioned above are uniformly mixed in different mass ratios to prepare a series of homogeneous mixed samples with graphitization gradients; S3: Raman spectroscopy test: Raman spectroscopy tests were performed on the above gradient mixed samples to obtain the intensity ratio of the D peak to the G peak of each mixed sample. ; S4: Calibration Curve Establishment: Plot the graphitization degree of the mixed sample on the ordinate, and the corresponding... The x-axis is used to plot the calibration curve and fit it to obtain a linear empirical formula. S5: Sample Testing: Perform Raman spectroscopy on the non-graphite carbon material under the same conditions to obtain its... value; S6: Calculation of graphitization degree: Calculate the graphitization degree of the sample to be tested. Substituting the values ​​into the above linear empirical formula, the degree of graphitization of the sample to be tested is calculated.

2. The method for characterizing the graphitization degree of a non-graphite carbon material according to claim 1, characterized in that, In step S2, the graphitization gradient of the gradient mixed sample includes 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, and 100%.

3. The method for characterizing the graphitization degree of a non-graphite carbon material according to claim 1, characterized in that, In step S2, the specific method for uniform mixing is as follows: weigh the two standard substances according to the proportion and place them in an agate jar, add anhydrous alcohol and agate balls, grind them thoroughly on a planetary ball mill at a speed of 45±5Hz for 1 hour, and then dry them at 105℃ for 1 hour.

4. The method for characterizing the degree of graphitization of non-graphite carbon materials according to claim 3, characterized in that, The total weight of the mixed sample is 10g, accurate to 0.001g; the volume of anhydrous ethanol added is 100mL; and the agate balls have a diameter of 1mm and a quantity of 50.

5. The method for characterizing the graphitization degree of a non-graphite carbon material according to claim 1, characterized in that, In steps S3 and S5, the Raman spectroscopy test uses a 532nm laser with a laser power of 2mW. At least 100 sites are randomly detected for each sample, and the average value is taken as the sample's Raman spectroscopy result. value.

6. The method for characterizing the degree of graphitization of non-graphite carbon materials according to claim 1, characterized in that, In step S4, the linear empirical formula takes the form: G = a × ( )+b, where G is the degree of graphitization (%), and a and b are constants obtained from the fitting.

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