Identification method of carbon nanofiber-carbon nanotube double-layer composite material

Abstract

The invention discloses a method for identifying a carbon nanofiber-carbon nanotube double-layer composite material, which comprises the following steps of: 1, observing with an electron microscope: observing crisscrossed fibers with the diameter of 10-100nm and the length of 1-100mu m; villus-shaped attachments are distributed on the outer walls of the fibers, and the villus-shaped attachments on the outer walls of the single fibers are mutually wound; 2, observation by a transmission electron microscope: observing that a single villus-shaped attachment is of a hollow tubular structure, wherein the diameter of the villus-shaped attachment is 2-6nm; the crystal is observed to be layered, and the interlayer spacing is 0.343 nm; 3, testing the powdery sample to be tested by adopting an X-ray photoelectron spectrometer, and calculating the content percentage of the obtained carbon atoms; and 4, if the to-be-detected sample meets the first and second observation requirements and the carbon atom content is greater than or equal to the carbon content judgment value, judging that the to-be-detected sample meets the first and second observation requirements. The method has the advantages that the method is simple and reliable, and reliable technical guarantee is provided for port detection work.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon nanofiber composite material determination, and particularly to the determination of carbon nanofiber-carbon nanotube bilayer composites. Background Art

[0002] The carbon nanofiber-carbon nanotube bilayer composite material is based on electrospun carbon nanofibers as the substrate, and carbon nanotubes are grown on its surface based on high-temperature chemical vapor deposition technology, thereby constructing a novel bilayer nanofiber material. This novel bilayer nanofiber material has excellent mechanical properties, electrical conductivity, thermal conductivity, and adsorption properties.

[0003] In order to adapt to the continuous development and application of carbon nanofiber-carbon nanotube bilayer composite materials in the market, the customs work also needs to establish a corresponding identification and determination system in a timely manner, so as to carry out the detection work of corresponding materials by the customs well. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: to provide a method for identifying carbon nanofiber-carbon nanotube bilayer composites, which is simple, convenient, and has good accuracy.

[0005] To solve the above problems, the technical solution adopted by the present invention is: a method for identifying carbon nanofiber-carbon nanotube bilayer composites, characterized by comprising the following steps: I. Observation with an electron microscope: Take the sample to be tested, dry it, place the dried sample to be tested on the sample stage. The observation with an electron microscope needs to meet the following requirements: At a magnification of 3000 - 10000 times, crisscrossed fibers can be observed, and the diameter of the fibers is measured to be 10 - 100 nm, and the length is 1 - 100 μm; At a magnification of 10000 - 20000 times, villous attachments can be observed on the outer wall of the fibers, and the villous attachments on the outer wall of a single fiber are intertwined. II. Observation with a transmission electron microscope: Take the sample to be tested, dry it, fully grind and stir it evenly. The observation with a transmission electron microscope needs to meet the following requirements: At a magnification of 100000 - 200000 times, it can be observed that a single villous attachment has a hollow tubular structure with a wall thickness, and the diameter distribution of the villous attachments of a single hollow tubular structure is 2 - 6 nm; At a magnification of 200000 times, it is observed that the crystal is layered, and the layer spacing is measured to be 0.343 nm. III. Take the sample to be tested, dry it, fully grind and stir it evenly. Take the ground and stirred sample to be tested, and use an X-ray photoelectron spectrometer to test the powdered sample to be tested to obtain the atomic spectral peak areas of all elements in the sample. The percentage of carbon atom content is calculated using the following formula. The formula for the percentage of carbon atom content is as follows: Ni = L i / S i ; C A = N A / ∑N i ×100; In the formula: N i represents the corrected atomic peak area, L i represents the spectral peak area of the atom, S i is the sensitivity factor of the atom, C A is the percentage content of carbon atoms, N A is the corrected peak area of carbon atoms; The calculated percentage content of carbon atoms is greater than or equal to the carbon content determination value, and the carbon content determination value is 85% - 90%; IV. If the sample to be tested meets the observation requirements of the first and second steps, and the carbon atom content in the third step is greater than or equal to the carbon content determination value, then it is determined that the sample to be tested is a carbon nanofiber-carbon nanotube bilayer composite material.

[0006] Furthermore, in the foregoing method for identifying a carbon nanofiber-carbon nanotube bilayer composite material, in the first, second, and third steps, the drying temperature is 60°C - 80°C.

[0007] Furthermore, in the foregoing method for identifying a carbon nanofiber-carbon nanotube bilayer composite material, in the third step, randomly take the samples to be tested at 3 - 5 positions, respectively test the calculated percentage content of carbon atoms, and the average value of all the percentage contents of carbon atoms is the percentage content of carbon atoms of the sample to be tested.

[0008] Furthermore, in the foregoing method for identifying a carbon nanofiber-carbon nanotube bilayer composite material, in the third step, the conditions of the X-ray photoelectron spectrometer include: Alka characteristic X-ray; spot size 400μm; full spectrum scan 1 time, pass energy 160ev, energy step 1.0ev; high-resolution XPS elemental spectrum scan 5 times, pass energy 50ev, energy step 0.1ev.

[0009] Furthermore, in the foregoing method for identifying a carbon nanofiber-carbon nanotube bilayer composite material, the method for determining the carbon content determination value includes the following steps: at least prepare the carbon nanofiber-carbon nanotube bilayer composite material 60 times, and the preparation process each time is as follows: in 100 mL of absolute ethanol, add 2.5 g of nickel nitrate solution, the concentration of the nickel nitrate solution is 0.1 mol / L, stir evenly, and take 100 cm of carbon nanofibers 2Immerse it for 2 to 3 hours, and then place the impregnated carbon nanofibers in a plasma chemical vapor deposition equipment for treatment. The equipment conditions include: power of 300 to 500 W, flow rate ratio of hydrogen to methane of 2.5:1, and growth time of 15 to 30 minutes; a carbon nanofiber-carbon nanotube bilayer composite material is prepared. Take the carbon nanofiber-carbon nanotube bilayer composite material samples prepared each time, and conduct the first and second step observations. The samples that meet the requirements of the first and second step observations are valid samples. Conduct the third step carbon content determination on the valid samples, record the carbon content percentage, obtain the carbon content percentage range, and take the minimum value; the number of valid samples is not less than 50.

[0010] The advantages of the present invention are as follows: The method for identifying a carbon nanofiber-carbon nanotube bilayer composite material according to the present invention is simple and can accurately identify, thereby providing reliable technical support for port detection work. Description of the Drawings

[0011] Figure 1 It is an electron microscope observation image of a sample that is not used as a valid sample among the 80 times of carbon nanofiber-carbon nanotube bilayer composite materials prepared in the specific embodiment.

[0012] Figure 2 It is an electron microscope observation image of another sample that is not used as a valid sample among the 80 times of carbon nanofiber-carbon nanotube bilayer composite materials prepared in the specific embodiment.

[0013] Figure 3 It is a lens observation image of a sample that is not used as a valid sample among the 80 times of carbon nanofiber-carbon nanotube bilayer composite materials prepared in the specific embodiment.

[0014] Figure 4 It is an electron microscope observation image of the sample to be tested in Example 1.

[0015] Figure 5 It is an electron microscope observation image of the sample to be tested in Example 1 at a magnification of 20,000 times.

[0016] Figure 6 It is a transmission electron microscope observation image of the sample to be tested in Example 1 at a magnification of 200,000 times.

[0017] Figure 7 It is an electron microscope observation image of the sample to be tested in Example 2. Embodiment

[0018] The present invention will be further described in detail below with reference to the drawings and preferred embodiments.

[0019] Prepare 80 times of carbon nanofiber-carbon nanotube bilayer composites. The preparation process for each time is as follows: Add 2.5 g of nickel nitrate solution with a concentration of 0.1 mol / L into 100 mL of absolute ethanol, stir evenly, and take 100 cm of carbon nanofibers 2 Immerse them in it for 2 - 3 hours, and then place the impregnated carbon nanofibers in a plasma chemical vapor deposition equipment for treatment. The equipment conditions include: the power is 300 - 500 W, the flow ratio of hydrogen to methane is 2.5:1, and the growth time is 15 - (30) minutes; obtain the carbon nanofiber-carbon nanotube bilayer composites.

[0020] For each time of preparing the carbon nanofiber-carbon nanotube bilayer composites, electron microscope observation and lens observation are carried out. Among them, 77 observations meet the requirements and are used as effective samples. Among them, 3 tests are not effective samples. The three tests that cannot be used as effective samples are as shown in the scanning electron microscope Figure 1 , Figure 2 , Figure 3 . Figure 1 Among them, a large number of beads appear on the surface of the fiber membrane, Figure 2 there is a phenomenon of needle blockage in Figure 3 , and the carbon nanotubes grown in

[0021] are too short and have a small specific surface area, unable to achieve the expected function. The above all do not meet the requirements of material preparation. The main reason for the samples that do not meet the requirements is that the process parameters in the preparation process are manually controlled and are prone to deviation, resulting in this result. The atomic content percentage determination is carried out for each effective sample. The steps for the atomic content percentage determination for each effective sample include: Sampling (0.05) grams at four different positions on each effective sample, drying, fully grinding and stirring evenly. Take the ground and stirred sample, and use an X-ray photoelectron spectrometer to test the powdered sample to measure the atomic peak areas of all elements in the effective sample. The carbon atom content percentage is calculated using the following formula. The carbon atom content percentage formula is as follows: N i =L i / S i ; C A =N A / ∑N i ×100; In the formula: N i represents the corrected atomic peak area, L i represents the atomic peak area, S i is the atomic sensitivity factor, C A is the carbon atom content percentage, and N A is the corrected carbon atom peak area; The determination results of the atomic content percentage of 77 valid samples are recorded as shown in Table 1: 。

[0022] The above experiments show that the carbon content of the carbon nanofiber-carbon nanotube bilayer composite material that meets the requirements is between 85% and 93.7%. Therefore, the minimum carbon content of 85% is used as the carbon content determination value.

[0023] Example 1: Sample 1 # to be tested. (Carbon nanofiber-carbon nanotube bilayer composite film purchased from the School of Textile Engineering, Tianjin Polytechnic University) I. Take Sample 1 # to be tested, dry it at 60 °C, place the dried Sample 1 # to be tested on the sample stage, and observe it using an electron microscope (produced by HITACHI, model S4800 cold field emission electron microscope). The observation results are as follows: At magnifications of 3000 - 10000, crisscrossed fibers are observed. The diameter of the fibers is measured to be 10 - 100 nm, and the length is 1 - 100 μm. At magnifications of 10000 - 20000, villous attachments can be observed on the outer wall of the fibers, and the villous attachments on the outer wall of a single fiber are intertwined. As Figure 4 、 Figure 5 shown.

[0024] II. Take the sample to be tested, fully grind and stir it evenly after drying, and observe it using a transmission electron microscope. The following requirements need to be met: At magnifications of 100000 - 200000, single villous attachments with a wall thickness can be observed to have a hollow tubular structure, and the diameter distribution of the single villous attachments with a hollow tubular structure is 2 - 6 nm. At a magnification of 200,000, the crystals are observed to be layered, and the layer spacing is measured to be 0.343 nm, as Figure 6 shown.

[0025] III. Take the sample to be tested, fully grind and stir it evenly after drying, take the ground and stirred sample to be tested, and use an X-ray photoelectron spectrometer to test the powdered sample to be tested to obtain the atomic spectral peak areas of all elements in the sample. The percentage of carbon atom content is calculated using the following formula. The formula for the percentage of carbon atom content is as follows: N i =L i / S i ; C A =N A / ∑N i ×100; In the formula: N i represents the corrected atomic peak area, L i represents the atomic spectral peak area, S iis the sensitivity factor of the atom, C A is the percentage content of carbon atoms, N A is the corrected peak area of carbon atoms; as shown in Table 2: .

[0026] The calculated percentage content of carbon atoms is greater than or equal to the carbon content determination value, and the carbon content determination value is 92%, which is greater than the carbon content determination value of 85%.

[0027] IV. The sample to be tested meets the observation requirements of the first and second steps, and the carbon atom content in the third step meets the requirement of being greater than or equal to the carbon content determination value. Therefore, it is determined that the sample to be tested is a carbon nanofiber-carbon nanotube bilayer composite material.

[0028] Example 2: The reverse osmosis membrane purchased on the market has an appearance similar to that of a common membrane, and its composition and structure are unknown.

[0029] I. Take several samples to be tested, repeatedly rinse the surface of the membrane with deionized water to remove the adsorbed dust on the surface, and then place it in a vacuum drying oven at 50 °C for 24 hours. Cut the dried membrane into pieces of 0.2×0.2 cm, and stick it on the sample stage with conductive glue.

[0030] Observation was carried out using an electron microscope (produced by HITACHI, model S4800 cold field emission electron microscope), and the observation results are as follows Figure 7 As shown, the SEM image of the reverse osmosis membrane is significantly different from the SEM surface and cross-sectional images of the carbon nanofiber-carbon nanotube bilayer composite membrane. It can be seen from the figure that the SEM image of the reverse osmosis membrane shows a disordered arrangement of macromolecules, which are arranged tightly with voids in the middle. The internal structures of the two membranes are completely different, reflecting different forming processes. No fiber arrangement is seen in the reverse osmosis membrane, which may be formed by polymerization of polymer materials.

[0031] II. Take the sample to be tested, dry it and then grind and stir it evenly. Observation using a transmission electron microscope shows that no image can be observed. It may be that the thickness of the reverse osmosis membrane is relatively large, and the electron beam of the transmission electron microscope can only penetrate a thin sample less than one hundred nanometers, so the membrane cannot be analyzed using a transmission electron microscope.

[0032] III. Take the sample to be tested, dry it and then grind and stir it evenly. Take the ground and stirred sample to be tested, and use an X-ray photoelectron spectrometer to test the powdered sample to be tested. The measured element contents in the sample are shown in Table 3: .

[0033] The carbon content is 76.8%. In summary, it can be judged that this membrane is not a CNFS-CNTS material.

[0034] It can be obtained from the above embodiments that the method for identifying a carbon nanofiber-carbon nanotube bilayer composite material according to the present invention is simple and can accurately identify, thus providing reliable technical support for port detection work.

Claims

1. A method for identifying a carbon nanofiber-carbon nanotube bilayer composite material, characterized in that: It includes the following steps: I. Electron microscope observation: Take the sample to be tested, dry it, place the dried sample to be tested on the sample stage. The electron microscope observation needs to meet the following requirements: At a magnification of 3000 - 10000 times, crisscrossed fibers can be observed, and the diameter of the fibers is measured to be 10 - 100 nm, and the length is 1 - 100 μm; At a magnification of 10000 - 20000 times, villous attachments can be observed on the outer wall of the fibers, and the villous attachments on the outer wall of a single fiber are in a mutually entangled state; II. Transmission electron microscope observation: Take the sample to be tested, fully grind and stir it evenly after drying. The transmission electron microscope observation needs to meet the following requirements: At a magnification of 100000 - 200000 times, a single villous attachment can be observed to have a hollow tubular structure with a wall thickness, and the diameter distribution of the villous attachments of a single hollow tubular structure is 2 - 6 nm; At a magnification of 200000 times, the crystal is observed to be layered, and the layer spacing is measured to be 0.343 nm; III. Take the sample to be tested, fully grind and stir it evenly after drying. Take the ground and stirred sample to be tested, and use an X-ray photoelectron spectrometer to test the powdered sample to be tested to obtain the atomic spectral peak areas of all elements in the sample. The percentage of carbon atom content is calculated using the following formula. The formula for the percentage of carbon atom content is as follows: N i = L i / S i ; C A = N A / ∑N i × 100; Where: N i represents the corrected atomic peak area, L i represents the spectral peak area of the atom, S i is the sensitivity factor of the atom, C A is the percentage content of carbon atoms, N A is the corrected carbon atom peak area; The calculated percentage of carbon atom content is greater than or equal to the carbon content determination value, and the carbon content determination value is 85% - 90%; IV. If the sample to be tested meets the observation requirements of the first and second steps and the carbon atom content in the third step is greater than or equal to the carbon content determination value, then it is determined that the sample to be tested is a carbon nanofiber-carbon nanotube bilayer composite material.

2. The method for identifying a carbon nanofiber-carbon nanotube bilayer composite material according to claim 1, characterized in that: In the first, second, and third steps, the drying temperature is 60°C - 80°C.

3. The method for identifying a carbon nanofiber-carbon nanotube bilayer composite material according to claim 1, characterized in that: In the third step, take the sample to be tested at 3 - 5 arbitrary positions, respectively test and calculate the percentage of carbon atom content, and the average value of all the percentages of carbon atom content is the percentage of carbon atom content of the sample to be tested.

4. The method for identifying a carbon nanofiber-carbon nanotube bilayer composite material according to claim 1, characterized in that: In the third step, the conditions of the X-ray photoelectron spectrometer include: Alka characteristic X-ray; spot size 400 μm; full spectrum scan 1 time, pass energy 160 ev, energy step 1.0 ev; high-resolution XPS elemental spectrum scan 5 times, pass energy 50 ev, energy step 0.1 ev.

5. The method for identifying a carbon nanofiber-carbon nanotube bilayer composite material according to claim 4, characterized in that: The method for determining the carbon content determination value includes the following steps: At least 60 times of carbon nanofiber-carbon nanotube bilayer composites are prepared, and the preparation process for each time is as follows: In 100 mL of absolute ethanol, 2.5 g of nickel nitrate solution with a concentration of 0.1 mol / L is added, stirred evenly, and 100 cm of carbon nanofibers are taken 2 and impregnated therein for 2 to 3 hours, and then the impregnated carbon nanofibers are placed in a plasma chemical vapor deposition device for treatment. The device conditions include: the power is 300 to 500 W, the flow ratio of hydrogen to methane is 2.5:1, and the growth time is 15 to 30 minutes; the carbon nanofiber-carbon nanotube bilayer composite is obtained; Take the carbon nanofiber-carbon nanotube bilayer composite material samples prepared each time and conduct the first and second step observations. The samples that meet the requirements of the first and second step observations are valid samples. Conduct the third step carbon content determination on the valid samples, record the carbon content percentage, obtain the carbon content percentage range, and take the minimum value; the number of valid samples is not less than 50.

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