Quantitative analysis method of oxide film crystal structure of formed aluminum foil for electrolytic capacitor

Abstract

The invention belongs to the technical field of electrode foils for aluminum capacitors, and particularly relates to a quantitative analysis method of an oxide film crystal structure of a formed aluminum foil for an electrolytic capacitor, which comprises the following steps: dissolving halogen serving as a solute in an organic alcohol solvent to obtain an organic halogen solution; placing the formed aluminum foil for the capacitor to be detected in the organic halogen solution, and performing microwave ultrasonic treatment; cleaning and drying residues subjected to ultrasonic treatment, and grinding the residues into powder; preparing a halogen organic solution again, adding the powder into the boiling halogen organic solution, and sealing and cooking to obtain white powder; according to the method, an anhydrous system is used for treating a sample, the sample is not in contact with water in the whole testing process, amorphous hydrated alumina is not generated, a new alumina product is not introduced, and the method has the advantages that the method is simple and convenient to operate, the cost is low, and the method is suitable for large-scale industrial production. And the finally stripped aluminum oxide is not polluted.

Description

Technical Field

[0001] The invention belongs to the technical field of electrode foil for aluminum electrolytic capacitors, and in particular relates to a quantitative analysis method for the crystal structure of an oxide film of a chemically formed aluminum foil for an electrolytic capacitor. Background Art

[0002] With the development of electronic whole machine system and frequency conversion technology, aluminum electrolytic capacitors have important and broad application prospects in the fields of mobile communications, information technology, consumer electronics and electric vehicles. The anode foil of aluminum electrolytic capacitors is usually covered with a dense oxide film, which is an important working medium of aluminum electrolytic capacitors. The main structures are γ-Al2O3, amorphous amorphous aluminum oxide and a small amount of hydrated oxide film. The commonly used method for preparing chemical foil for capacitors in industrial manufacturing is electrochemical corrosion. Due to the different electrochemical corrosion processes, the contents of each component in the anode foil under different formation processes are also different. The main structure of the anode foil oxide film contains an amorphous phase, which is very difficult to quantitatively analyze the amorphous phase in the mixed phase. The oxide film of the anode aluminum foil is very thin, and the middle of the two oxide films is a high-purity aluminum base layer. The X-ray diffraction diffraction spectrum will show high-intensity peaks due to the strong texture of aluminum, which makes it difficult to quantitatively analyze the physical phase. Therefore, it is of great significance to study the characterization method of the oxide film on the surface of the anode foil.

[0003] The prior art uses water in the stage of preparing or stripping the oxide film, resulting in a large amount of water and oxide film on the surface of the formed foil in the early stage of treatment, making the method unreliable. These water and oxide films partially evolve into amorphous aluminum oxide during the later treatment process, resulting in inaccurate final calculation results. Summary of the invention

[0004] In view of the deficiencies of the above-mentioned prior art, the object of the present invention is to provide a method for quantitatively analyzing the crystal structure of an oxide film of a chemically formed aluminum foil for an electrolytic capacitor. The present invention dissolves the core layer of the chemically formed foil with an organic halogen solution in an anhydrous environment, peels off the oxide film on the surface, and uses the Rietveld method to refine the crystal structure of the diffraction pattern of the white powder, and calculates the content ratio of crystalline and amorphous aluminum oxide in the oxide film. The present invention uses an anhydrous system to process the sample, does not come into contact with water during the entire testing process, does not regenerate amorphous hydrated aluminum oxide, does not introduce new aluminum oxide products, and does not pollute the finally peeled aluminum oxide.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions: A quantitative analysis method for the crystal structure of an oxide film of a formed aluminum foil for an electrolytic capacitor comprises the following steps: Take halogen as solute and dissolve it in organic solvent to obtain organic halogen solution.

[0006] The capacitor to be tested is placed in the organic halogen solution with a chemically formed aluminum foil and subjected to microwave ultrasonic treatment, so that the organic halogen solution peels off the oxide film on the surface of the chemically formed aluminum foil to obtain the oxide film and residual aluminum, and the residue after ultrasonic treatment is cleaned, dried and ground into powder.

[0007] The organic halogen solution is re-prepared, the powder is added into the boiling organic halogen solution, and the solution is sealed and steamed to dissolve the residual aluminum again, and a white powder is obtained through post-treatment.

[0008] The Rietveld method was used to refine the crystal structure of the diffraction pattern of the white powder and calculate the content ratio of crystalline and amorphous aluminum oxide in the oxide film.

[0009] The present invention dissolves a halogen solute in an organic solvent to obtain an organic halogen solution, then places a capacitor to be tested with a chemically formed aluminum foil in the organic halogen solution, performs microwave ultrasonic treatment, and uses an anhydrous system organic halogen solution to peel off the oxide film on the surface of the chemically formed foil. Since the halogen only reacts with aluminum after being dissolved in an alcohol solvent, and does not react with aluminum oxide, the oxide film on the surface of the chemically formed foil can be completely retained to obtain an oxide film and a small amount of residual aluminum. The oxide film and the small amount of residual aluminum are cleaned, dried, and ground into powder, and then the residual aluminum is dissolved again to obtain a white powder. Finally, the diffraction pattern of the white powder is refined by the Rietveld method to perform crystal structure refinement, and the content ratio of crystalline and amorphous aluminum oxide in the oxide film is calculated. The present invention uses an anhydrous system to process the sample, does not contact with water during the entire test process, does not regenerate amorphous hydrated aluminum oxide, does not introduce new aluminum oxide products, does not pollute the finally stripped aluminum oxide, and has accurate calculation results and small errors.

[0010] In a preferred embodiment of the present invention, the mass percentage of halogen in the organic solvent is 10% to 22%, and more preferably 15% to 22%.

[0011] In a preferred embodiment of the present invention, the organic alcohol solvent does not contain water.

[0012] In a preferred embodiment of the present invention, the microwave ultrasonic treatment time is 24 hours to 48 hours.

[0013] In a preferred embodiment of the present invention, the halogen is chlorine, bromine or iodine.

[0014] In a preferred embodiment of the present invention, the sealed cooking time is 10 minutes to 20 minutes.

[0015] In a preferred embodiment of the present invention, the mass concentration of the re-prepared halogen organic solution is 10% to 22%, and more preferably.

[0016] In a preferred embodiment of the present invention, the diffraction pattern scanning parameters are: light tube power greater than 5 kW~9 kW, scanning speed ≤10° / min, scanning range 5°~100°, and scanning step length ≤0.02° / min.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention dissolves a halogen solute in an organic solvent to obtain an organic halogen solution, then places a capacitor to be tested with a chemically formed aluminum foil in the organic halogen solution, performs microwave ultrasonic treatment, and uses an anhydrous system organic halogen solution to peel off the oxide film on the surface of the chemically formed foil. Since the halogen only reacts with aluminum after being dissolved in an alcohol solvent, and does not react with aluminum oxide, the oxide film on the surface of the chemically formed foil can be completely retained to obtain an oxide film and a small amount of residual aluminum. The oxide film and the small amount of residual aluminum are cleaned, dried, and ground into powder, and then the residual aluminum is dissolved again to obtain a white powder. Finally, the diffraction pattern of the white powder is refined by the Rietveld method to perform crystal structure refinement, and the content ratio of crystalline and amorphous aluminum oxide in the oxide film is calculated. The present invention uses an anhydrous system to process the sample, does not contact with water during the entire test process, does not regenerate amorphous hydrated aluminum oxide, does not introduce new aluminum oxide products, does not pollute the finally stripped aluminum oxide, and has accurate calculation results and small errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the data map index result in Example 1 of the present invention.

[0019] Figure 2 This is a diagram of the fitting results in Example 1 of the present invention.

[0020] Figure 3 This is a diagram showing the fitting results after crystal structure refinement of the diffraction pattern in Example 1 of the present invention.

[0021] Figure 4 This is the index result diagram in Example 2 of the present invention.

[0022] Figure 5 This is a diagram of the fitting results in Example 2 of the present invention.

[0023] Figure 6 This is the index result diagram in Example 3 of the present invention.

[0024] Figure 7 This is a diagram of the fitting results in Example 3 of the present invention.

[0025] Figure 8 This is the index result diagram in Example 4 of the present invention.

[0026] Fig. 9 This is a diagram showing the result after marking and fitting in Example 4 of the present invention.

[0027] Fig.10 This is a diagram showing the fitting results after crystal structure refinement of the diffraction pattern in Example 4 of the present invention.

[0028] Fig.11 Schematic diagram of the oxide film on the surface of high-pressure chemically formed foil.

[0029] Fig.12 This is the X-ray diffraction pattern of the high pressure chemically formed foil surface.

[0030] Fig.13 The following are the partially enlarged images of the X-ray diffraction spectra of the formed foils: (a) FA formed foil, (b) SR formed foil.

[0031] Fig.14 The microstructure of the oxide film on the surface of the electrochemical foil, (a) SEM image at a magnification of 1.5k, (b) SEM image at a magnification of 4.0k.

[0032] Fig.15 The chemically formed foil after treatment with 1% NaOH solution, (a) SEM image at 1.5k magnification, (b) SEM image at 4.0k magnification, (c) X-ray diffraction spectrum. DETAILED DESCRIPTION

[0033] The following is a detailed description of the technical solutions in the embodiments of the present invention in combination with the preferred embodiments and the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] It should be noted that all professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods.

[0035] There are the following difficulties in studying the composition and structure of the oxide film on the surface of chemically formed aluminum foil: (1) The surface oxide film is too thin, making it difficult to perform peeling detection. The thickness of aluminum oxide in the electrolytic capacitor foil is related to its formation voltage, which is generally 1.4nm / V~1.5nm / V. The formation voltage is also related to the rated working voltage, which is generally 1.2 times~2 times the rated working voltage. The surface oxide film thickness of the general high-voltage electronic aluminum foil (above 500V) is about 1um.

[0036] Schematic diagram of the oxide film on the surface of high pressure chemically formed foil Fig.11As shown in the figure, from the research results of Shen Xingsu and Shimizu Kenichi on the anodized film on the surface of electroplated foil, it was learned that the amorphous aluminum oxide film was initially formed by anodization, and then reacted with the hot electrolyte on the surface of the aluminum base layer to generate γ'-Al2O3 crystal nuclei, and finally formed a γ-Al2O3 film.

[0037] (2) Analysis of the high-purity aluminum base layer of the backing of the chemically formed foil. The processed aluminum foil has a high cubic texture content, which will show a high-intensity peak in the X-ray diffraction spectrum, which has a great impact on the X-ray diffraction phase analysis. The X-ray diffraction spectrum of the surface of the high-pressure chemically formed foil is as follows: Fig.12 As shown, by directly using XRD to detect the formed foil phase, a large number of aluminum diffraction peaks can be seen, while no diffraction peaks can be seen from the surface oxide film.

[0038] (3) The oxide film contains a large amount of amorphous amorphous aluminum oxide. The X-ray diffraction ability of the amorphous phase is very poor, and the quantitative analysis of the amorphous phase in the mixed sample is difficult. Fig.13 This is a partial enlarged view of the X-ray diffraction spectrum of the chemical foil. It can be seen from the figure that it contains amorphous aluminum oxide and γ-Al2O3. The detection of amorphous aluminum oxide is more difficult.

[0039] Therefore, the invention is mainly used for characterizing the crystal structure of the surface oxide film due to the change of the formation process during the industrial production of formed aluminum foil for electrolytic capacitors. Due to the difference in the formation process, the structure of the surface oxide film is different. The structure of the oxide film mainly determines the withstand voltage of the capacitor. The withstand voltage of dense aluminum oxide is higher, and the withstand voltage of loose γ-alumina is lower. On the one hand, the present invention can guide the formation process to the crystal structure of the oxide film of the formed aluminum foil for electrolytic capacitors, and on the other hand, it can also be used for quality inspection of the formed foil.

[0040] The present invention is mainly divided into two parts. The first is to strip the oxide film of the aluminum foil used for electrolytic capacitors. This method uses an anhydrous system to strip the oxide film on the surface of the foil. The anhydrous system includes but is not limited to halogen pure substances such as bromine and iodine that are easily soluble in methanol, ethanol, and other alcohols. From the perspective of environmental protection and experimental safety, iodine is generally used as a solute. It is dissolved in alcohol substances such as methanol and ethanol to prepare a saturated iodine solution to strip the oxide film on the surface of the foil. Since the halogen only reacts with aluminum after dissolving in alcohols such as methanol or ethanol, and does not react with aluminum oxide, the oxide film on the surface of the foil can be completely retained.

[0041] The second is the quantitative calculation of the structure of the oxidized aluminum oxide in the oxide film of the electrolytic capacitor aluminum foil. The X-ray diffraction method is used to calculate the crystalline and amorphous content of aluminum oxide in the oxide film. The calculation of amorphous aluminum oxide is calculated by all fitting methods, and then the external standard method is used to calculate the accuracy of the data.

[0042] Example 1 Weigh about 5 grams of 1# foil (forming voltage is 530V, forming liquid is inorganic acid) for the capacitor to be tested, and cut the material into thin strips. Note that the width of the thin strips should be about 2 mm. To speed up the experiment, use a paper cutter to cut the sample shorter again, with a length of less than 10 cm, and put it into a 1 L beaker.

[0043] 100 grams of pure iodine was added to 500 mL of anhydrous methanol to prepare an iodine-methanol solution, and the chopped foil and the iodine-methanol solution were added to a 1 L beaker, and the beaker was placed on a microwave ultrasonic device for 20 hours. In order to avoid insufficient reaction between iodine and aluminum, 50 grams of pure iodine was added again after 20 hours of ultrasonication, and then ultrasonication was performed for 20 hours. After the end of the ultrasonication, the beaker was kept still for 30 minutes, the supernatant was poured out, and the residue and precipitate were retained. 500 mL of anhydrous methanol was added to the above suspension again, and the supernatant was kept still for 30 minutes after ultrasonication for 5 minutes. The supernatant was poured out, the precipitate was retained, and the above cleaning process was repeated 5 times. The residue and the remaining residual liquid were poured into a petri dish for drying, and then placed in an agate crucible and ground into powder.

[0044] Place 600 mL of anhydrous methanol in a 1 L beaker, heat the methanol to boiling, and add 100 grams of pure iodine powder again. Add the above powder to the boiling iodine-methanol solution and steam in a closed container for 10 minutes. After cooling the liquid and letting it stand for 30 minutes, pour out the supernatant and retain the residue and precipitate. Add 500 mL of anhydrous methanol to the above suspension again, ultrasonicate for 5 minutes and let it stand for 30 minutes. Pour out the supernatant and retain the precipitate. After repeating the above cleaning process 5 times, pour the retained precipitate into a petri dish to dry, and grind the powder again.

[0045] The white powder was scanned by X-ray powder diffraction using a diffractometer. The light tube power was 9 kW, the target was copper, the scanning speed was 5° / min, and the scanning step was 0.02° / min. The scanning range was 5° to 100°. The data crystal form spectrum was indexed, and the COD card number of the indexed aluminum oxide was: 1512488. The indexing results are as follows: Figure 1 As shown, the crystalline aluminum oxide phase (Al2O3) is marked, and the amorphous aluminum oxide is marked as Amorphous. Figure 2 shown.

[0046] The diffraction pattern was refined using the Rietveld method. The final result of the structure refinement was Rwp(%) = 1.8%. Al2O3 is crystalline alumina, and its COD card number is: 1512488. The rest is amorphous alumina, marked as Amorphous. The calculated crystallinity is 63%, and the fitting is as follows Figure 3 As shown, the final calculated amorphous aluminum oxide content is 37%.

[0047] Example 2 Weigh about 6 grams of the capacitor foil 2# (forming voltage is 375V, and the forming liquid is organic acid), and cut the material into thin strips. Note that the width of the thin strips should be about 1 mm. To speed up the experiment, use a paper cutter to cut the sample again, with a length of 4 cm, and put it into a 1 L beaker.

[0048] 100 g of pure iodine was added to 500 mL of anhydrous methanol to prepare an iodine-methanol solution, and the chopped foil and the iodine-methanol solution were added to a 1 L beaker, and the beaker was placed on a microwave ultrasonic device for 20 hours. In order to avoid insufficient reaction between iodine and aluminum, 50 g of pure iodine was added again after stopping the ultrasound, and then the ultrasound was continued for 20 hours. After the ultrasound was completed, the beaker was left to stand for 20 minutes, the supernatant was poured out, and the residue and precipitate were retained. 500 mL of anhydrous methanol was added to the above suspension again, and the ultrasound was continued for 5 minutes and then left to stand for 20 minutes. The supernatant was poured out and the precipitate was retained. After repeating the above cleaning process 5 times, the residue and the remaining residual liquid were poured into a petri dish for drying, and then placed in an agate crucible and ground into powder.

[0049] Place 600 mL of anhydrous methanol in a 1 L beaker, heat the methanol to boiling, and add 100 grams of pure iodine powder again. Add the above powder to the boiling iodine-methanol solution and cook in a closed container for 10 minutes. After cooling the liquid and letting it stand for 20 minutes, pour out the supernatant and retain the residue and precipitate. Add 500 mL of anhydrous methanol to the above suspension again, ultrasonicate for 5 minutes and let it stand for 20 minutes. Pour out the supernatant and retain the precipitate. Repeat the above cleaning process 5 times and retain the precipitate. Pour the precipitate into a petri dish and dry it, and grind the powder again. Use a diffractometer to perform X-ray powder diffraction scanning on the white powder. The light tube power is 9 kw rotating target, copper target. The scanning speed is 5° per minute and the scanning step is 0.02° per minute. The scanning range is 5° to 100°. The data crystal form spectrum is indexed, and the indexed COD card number of alumina is: 1512488. The indexing results are as follows: Figure 4 shown.

[0050] The crystalline aluminum oxide phase (Al2O3) is marked, and the amorphous aluminum oxide is marked as Amorphous. Figure 5 As shown. The diffraction pattern was refined using the Rietveld method, and the final result of the structure refinement showed Rwp (%) = 1.93%. Among them, Al2O3 is crystalline alumina, and its COD card number is: 1512488. The rest is amorphous alumina, marked as Amorphous. The calculated crystallinity is 60%. The final calculated amorphous alumina content is 40%.

[0051] Example 3 Weigh about 5 grams of the capacitor foil 3# (forming voltage is 630 V; forming liquid is inorganic acid) to be tested, and cut the material into thin strips. Note that the width of the thin strips should be about 2 mm. To speed up the experiment, use a paper cutter to cut the sample again, with a length of 4 cm, and put it into a 1 L beaker.

[0052] 100 g of pure iodine was added to 500 mL of anhydrous methanol to prepare an iodine-methanol solution, and the chopped foil and the iodine-methanol solution were added to a 1 L beaker, and the beaker was placed on a microwave ultrasonic device for 20 hours. In order to avoid insufficient reaction between iodine and aluminum, 50 g of pure iodine was added again after stopping the ultrasound, and then the ultrasound was continued for 20 hours. After the ultrasound was completed, the beaker was left to stand for 20 minutes, the supernatant was poured out, and the residue and precipitate were retained. 500 mL of anhydrous methanol was added to the above suspension again, and the ultrasound was continued for 5 minutes and then left to stand for 20 minutes. The supernatant was poured out and the precipitate was retained. After repeating the above cleaning process 5 times, the residue and the remaining residual liquid were poured into a petri dish for drying, and then placed in an agate crucible and ground into powder.

[0053] Place 600 mL of anhydrous methanol in a 1 L beaker, heat the methanol to boiling, and add 100 grams of pure iodine powder again. Add the above powder to the boiling iodine-methanol solution and steam in a closed container for 10 minutes. After cooling the liquid and letting it stand for 20 minutes, pour out the supernatant and retain the residue and precipitate. Add 500 mL of anhydrous methanol to the above suspension again, ultrasonicate for 5 minutes and let it stand for 20 minutes. Pour out the supernatant and retain the precipitate. Repeat the above cleaning process 5 times and retain the precipitate. Pour the precipitate into a petri dish and dry it, and grind the powder again. Use a diffractometer to perform an X-ray powder diffraction scan on the white powder. The light tube power is 9kw rotating target, copper target. The scanning speed is 5° per minute and the scanning step is 0.02° per minute. The scanning range is 5° to 100°. The data crystal form spectrum is indexed, and the COD card number of the indexed alumina is: 1512488. The indexing results are as follows: Figure 6 shown.

[0054] The crystalline aluminum oxide phase (Al2O3) is marked, and the amorphous aluminum oxide is marked as Amorphous. The diffraction pattern is refined using the Rietveld method. The final result of the structure refinement is Rwp (%) = 1.78%. Among them, Al2O3 is crystalline aluminum oxide, and its COD card number is: 1512488. The rest is amorphous aluminum oxide marked as Amorphous. The fitting results are as follows Figure 7 The calculated crystallinity is 60%. The final calculated amorphous aluminum oxide content is 40%.

[0055] Example 4 Weigh about 5 grams of the capacitor foil 4# (forming voltage is 620V: the forming liquid is organic acid) to be tested, and cut the material into thin strips. Note that the width of the thin strips should be about 2 mm. To speed up the experiment, use a paper cutter to cut the sample again, with a length of less than 10 cm, and put it into a 1 L beaker.

[0056] 100 grams of pure iodine was added to 500 mL of anhydrous methanol to prepare an iodine-methanol solution, and the chopped foil and the iodine-methanol solution were added to a 1L beaker, and the beaker was placed on a microwave ultrasonic device for 20 hours. In order to avoid insufficient reaction between iodine and aluminum, 50 grams of pure iodine was added again after 20 hours of ultrasonication, and then ultrasonication was continued for 20 hours. After the end of the ultrasonication, the beaker was left to stand for 30 minutes, the supernatant was poured out, and the residue and precipitate were retained. 500 mL of anhydrous methanol was added to the above suspension again, and the suspension was left to stand for 30 minutes after 5 minutes of ultrasonication. The supernatant was poured out and the precipitate was retained. After repeating the above cleaning process 5 times, the residue and the remaining residual liquid were poured into a petri dish for drying, and then placed in an agate crucible and ground into powder.

[0057] Place 600 mL of anhydrous methanol in a 1L beaker, heat the methanol to boiling, and add 100 grams of pure iodine powder again. Add the above powder to the boiling iodine-methanol solution and cook in a closed container for 10 minutes. After cooling the liquid and letting it stand for 30 minutes, pour out the supernatant and retain the residue and precipitate. Add 500 mL of anhydrous methanol to the above suspension again, ultrasonicate for 5 minutes and let it stand for 30 minutes. Pour out the supernatant and retain the precipitate. Repeat the above cleaning process 5 times and retain the precipitate. Pour the precipitate into a petri dish and dry it, and grind the powder again. Use a diffractometer to perform X-ray powder diffraction scanning on the white powder. The light tube power is 9kw rotating target, copper target. The scanning speed is 5° per minute and the scanning step is 0.02° per minute. The scanning range is 5° to 100°. The data crystal form spectrum is indexed, and the COD card number of the indexed alumina is: 1512488. The indexing results are as follows: Figure 8 shown.

[0058] The crystalline aluminum oxide phase (Al2O3) is marked, and the amorphous aluminum oxide is marked as Amorphous. Fig. 9 As shown. The diffraction pattern was refined using the Rietveld method, and the final result of the structure refinement showed Rwp (%) = 1.83%. Among them, Al2O3 is crystalline aluminum oxide, and its COD card number is: 1512488. The rest is amorphous aluminum oxide marked as Amorphous. The calculated crystallinity is 65%. After fitting, it is as follows Fig.10 shown.

[0059] In order to explore the quantitative analysis method of the oxide film on the surface of the chemical foil samples under two different chemical processes, the chemical foil samples were analyzed by scanning electron microscope (SEM). The microscopic morphology of the oxide film on the surface of the two chemical foils is shown in Figure 2. Fig.14 It can be found that the aluminum oxide film after chemical formation has formed a very obvious aluminum oxide dense pore structure, and there are loose attached floccules on the pore surface.

[0060] The most ideal way to study the surface oxide film is to directly peel off the oxide film from the chemical foil through pretreatment. Dong Xiaohong, et al. conducted a qualitative study on the physical phase of the oxide film on the surface of the chemical foil. They immersed the high-pressure chemical foil in a 1% NaOH solution and peeled off the oxide film by dissolving the aluminum base layer. The present invention attempts to use the same method to peel off the surface oxide film, hoping to achieve accurate quantitative analysis of the oxide film phase. After being treated with a 1% NaOH solution, the aluminum base layer of the chemical foil was completely dissolved, and the whole was stratified into multiple layers of white-gray flakes. It was subjected to scanning electron microscopy analysis and testing, and the microscopic morphology is as follows: Fig.15 As shown in (a) and (b) in Figure 1, it can be found that part of the aluminum oxide pore structure is destroyed, and a large number of lamellar structures are stacked. It is preliminarily judged that other substances may be generated. The treated chemical foil sample is ground into powder using a mortar, and its X-ray diffraction analysis results are shown in Figure 1. Fig.15 As shown in (c), a large amount of Al(OH)3 and other hydrated aluminum oxides were found in the oxide film on the surface of the chemical foil after treatment with NaOH solution, and they adhered to the surface of the oxide film. During the treatment of the chemical foil with NaOH solution, the aluminum oxide film will also participate in the reaction and be corroded by NaOH, thereby destroying its own pore structure. This fully demonstrates that the method of stripping the oxide film of the chemical foil using NaOH solution has limitations, and this method is not applicable to the quantitative analysis of the oxide film.

[0061] There are also some patents involving methods for quantifying oxide films of chemical foils, for example: Wang Landong et al. used an alkaline aqueous solution of sodium hydroxide and sodium phosphate to strip the chemical foil. For example: Huang Huirong et al. used microwave digestion to treat the chemical foil. For example: Deng Lisong et al. used a mixed solution of CuCl2 and hydrochloric acid to dissolve the aluminum matrix in the chemical foil, and then used an acid solution to dissolve the amorphous aluminum oxide, and then calculated the content of amorphous aluminum oxide. The patent uses the same method as the former, and the biggest problem is that water agents are used in the stage of preparing or stripping the oxide film. As a result, a large amount of water and oxide film have appeared on the surface of the chemical foil in the early stage of treatment. This makes the method unreliable. These water and oxide films partially evolve into amorphous aluminum oxide during the later treatment process. The final calculation result is inaccurate.

[0062] Therefore, this method uses an anhydrous system to peel off the oxide film on the surface of the chemical foil. The anhydrous system includes but is not limited to pure halogen substances such as bromine and iodine, and pure halogen substances are easily soluble in methanol, ethanol, and other alcohols. From the perspective of environmental protection and experimental safety, iodine is generally used as a solute. Dissolved in alcohol substances such as methanol and ethanol, a saturated iodine solution is prepared to peel off the oxide film on the surface of the chemical foil. Since the halogen only reacts with aluminum after being dissolved in alcohols such as methanol or ethanol, and does not react with aluminum oxide, the oxide film on the surface of the chemical foil can be completely retained. In addition, in a water system, aluminum reacts with water to produce aluminum hydroxide containing crystal water, and part of the amorphous aluminum oxide in the oxide film of the oxide film on the surface of the chemical foil also reacts with water to generate water and aluminum hydroxide. After subsequent drying treatment, water and aluminum hydroxide will be dehydrated to become aluminum hydroxide and amorphous aluminum oxide. In short, the water introduced into the system will eventually form new aluminum oxide, resulting in a large system error. After preparing the sample, the Rietveld method is used to refine the crystal structure of the diffraction pattern (peak position, intensity, line shape, etc.), and the proportion of amorphous aluminum oxide is calculated after the structure is refined.

[0063] In summary, the present invention uses an anhydrous system to process the sample, and there is no contact with water during the entire testing process, no regeneration of amorphous hydrated aluminum oxide, no introduction of new aluminum oxide products, and no pollution to the final stripped aluminum oxide.

[0064] It should be noted that when the present invention involves a numerical range, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes a preferred embodiment. Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the attached claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0065] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A quantitative analysis method for the crystal structure of an oxide film of an electrolytic capacitor formed aluminum foil, characterized in that: The following steps are involved: Taking halogen as solute, dissolving it in an organic alcohol solvent, to obtain an organic halogen solution; Placing the capacitor-to-be-tested aluminum foil in the organic halogen solution and subjecting it to microwave ultrasonic treatment, so that the organic halogen solution peels off the oxide film on the surface of the aluminum foil to obtain the oxide film and residual aluminum, washing the oxide film and residual aluminum after the ultrasonic treatment, drying and grinding them into powder; Re-preparing an organic halogen solution, adding the powder into the boiling organic halogen solution, sealing and steaming, dissolving the residual aluminum again, and obtaining a white powder through post-treatment; The Rietveld method was used to refine the crystal structure of the diffraction pattern of the white powder and calculate the content ratio of crystalline and amorphous aluminum oxide in the oxide film.

2. The quantitative analysis method of the crystal structure of the oxide film of the chemically formed aluminum foil for electrolytic capacitors according to claim 1, characterized in that: The mass percentage of halogen in the organic alcohol solvent is 10%~22%.

3. The quantitative analysis method of the crystal structure of the oxide film of the chemically formed aluminum foil for electrolytic capacitors according to claim 1, characterized in that: The organic alcohol is methanol, ethanol or propanol, and the organic alcohol solvent does not contain water.

4. The quantitative analysis method of the crystal structure of the oxide film of the chemically formed aluminum foil for electrolytic capacitors according to claim 1, characterized in that: The microwave ultrasonic treatment time is 24 hours to 48 hours.

5. The quantitative analysis method of the crystal structure of the oxide film of the chemically formed aluminum foil for electrolytic capacitors according to claim 1, characterized in that: The halogen is chlorine, bromine or iodine.

6. The quantitative analysis method of the crystal structure of the oxide film of the chemically formed aluminum foil for electrolytic capacitors according to claim 1, characterized in that: The sealed steaming time is 10 to 20 minutes.

7. The quantitative analysis method of the crystal structure of the oxide film of the chemically formed aluminum foil for electrolytic capacitors according to claim 1, characterized in that: The mass concentration of the reconstituted halogen organic solution is 10%~22%.

8. The method for quantitatively analyzing the crystal structure of the oxide film of the chemically formed aluminum foil for electrolytic capacitors according to claim 1, characterized in that: The scanning parameters of the diffraction pattern were as follows: light tube power 5 kW~9 kW, scanning speed ≤10° / min, scanning range 5°~100°, and scanning step ≤0.02° / min.

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