Method for testing particle size of powder

Abstract

The invention relates to the technical field of powder particle size testing, in particular to a powder particle size testing method which comprises the following specific steps: sieving powder, and adding the powder into a hexadecyl mercaptan solution, so that mercaptan forms a molecular layer on the surface of the powder; separating out powder by using a centrifugal machine, and washing by using hexane to remove non-adsorbed mercaptan molecules; the powder is subjected to acid pickling to remove colored impurities, and acid-pickled powder is obtained; mixing the acid-washed powder with deionized water to prepare turbid liquid, putting the turbid liquid on a magnetic stirrer for stirring, and adjusting the pH value of the turbid liquid to be neutral by using a sodium hydroxide solution; and putting the turbid liquid into an ultrasonic cleaning machine for external ultrasonic treatment. Hexadecyl mercaptan can protect the powder from being interfered by external impurities, the surface tension of a dispersion medium and the sedimentation performance of the powder are optimized, and the stability of the testing process is improved. Various impurities in the powder can be effectively removed through acid pickling, the purity of the powder can be improved, and it is ensured that the test result is accurate.

Description

Technical Field

[0001] The invention relates to the technical field of powder particle size testing, and in particular to a powder particle size testing method. Background Art

[0002] In the field of materials science, the performance of powder materials is closely related to their particle size. In catalyst preparation, powder catalysts with appropriate particle size can provide a larger specific surface area, thereby significantly improving the efficiency of the catalytic reaction. In ceramic production, the uniformity of the powder particle size distribution directly affects the density, mechanical strength and appearance quality of ceramic products. In the chemical industry, the powder particle size is related to the solubility, dispersibility and reactivity of the product. In the pharmaceutical field, the particle size of drug powders plays a decisive role in the solubility, bioavailability and efficacy of the drug.

[0003] Traditional powder particle size testing methods have many limitations: although the screening method is simple to operate, it is not effective for testing powders smaller than 40 microns, and the screening efficiency is low, the error is large, and it is difficult to accurately obtain particle size distribution information; the sedimentation method is easily affected by various factors such as particle shape, density, and medium viscosity, and the accuracy and repeatability of the test results are poor. In view of this, we propose a powder particle size testing method. Summary of the invention

[0004] The purpose of the present invention is to provide a method for testing the particle size of powders, so as to solve the problem that the screening method proposed in the above background technology is simple to operate, but has poor testing effect on powders less than 40 microns, and has low screening efficiency and large errors, making it difficult to accurately obtain particle size distribution information; the sedimentation method is easily affected by various factors such as particle shape, density and medium viscosity, and the accuracy and repeatability of the test results are poor.

[0005] To achieve the above object, the present invention provides a method for testing the particle size of a powder, comprising the following steps:

[0006] S1.1, sieve the powder to make the powder particle size 0.1-1000μm;

[0007] S1.2, dissolving hexadecyl mercaptan in toluene to obtain a hexadecyl mercaptan solution; adding powder to the hexadecyl mercaptan solution, stirring at room temperature at a speed of 300-600 rpm for 12-24 hours, so that the mercaptan forms a molecular layer on the surface of the powder; separating the powder by a centrifuge, and washing with hexane for 3-5 times to remove unabsorbed mercaptan molecules;

[0008] Hexadecyl mercaptan can form a molecular layer on the surface of the powder. On the one hand, this molecular layer can change the surface properties of the powder, such as wettability and roughness, so that it is more in line with the needs of subsequent experiments or applications; on the other hand, this molecular layer can isolate the powder from the external environment, reduce unnecessary chemical reactions between the powder and other substances, and protect the powder; in the process of preparing powder suspension, hexadecyl mercaptan can effectively reduce the interaction force between powder particles, so that the powder is more evenly dispersed in the solution and avoid agglomeration; in addition, the molecular layer formed by hexadecyl mercaptan can also improve the stability of the powder under different environmental conditions. For example, in the pickling process, it can protect the powder surface to a certain extent and prevent the powder from being excessively eroded by acid, thereby maintaining the structure of the powder.

[0009] S1.3, acid-washing the powder in S1.2 to remove colored impurities and obtain acid-washed powder;

[0010] S1.4, mix the acid-washed powder with deionized water to form a suspension; place the suspension on a magnetic stirrer, stir at a speed of 300-400 rpm for 5 minutes, and adjust the pH value of the suspension to neutral with sodium hydroxide solution;

[0011] S1.5. Place the suspension in S1.4 into an ultrasonic cleaning machine with an ultrasonic power of 100% and an external ultrasonic time of 10 minutes.

[0012] Preferably, in S1.2, the concentration of the hexadecyl mercaptan solution is 0.1-1 mM.

[0013] Preferably, in S1.2, the thickness of the molecular layer formed by thiol on the surface of the powder is 1-2 nm.

[0014] Preferably, in S1.2, the rotation speed of the centrifuge is 3000-5000 rpm, and the centrifugation time is 10-20 min.

[0015] Preferably, in S1.3, the powder is pickled by adding the powder into dilute nitric acid, stirring, and standing to soak for 1-4 hours; after pickling, the powder is rinsed with deionized water to remove residual acid and impurities; the powder is then soaked in anhydrous ethanol for 10-30 minutes; after the ethanol soaking, the powder is rinsed with deionized water, and then vacuum dried to obtain the pickled powder.

[0016] Dilute nitric acid is highly oxidizing and acidic, and can react with a variety of metals and their oxides to generate water-soluble nitrates. For example, metal impurities such as iron and copper can be dissolved and removed by dilute nitric acid, thereby improving the purity of the powder and preventing impurities from interfering with the particle size test results. For carbonate impurities that may exist in the powder, dilute nitric acid will react with them to generate carbon dioxide gas and water-soluble nitrates, thereby achieving the purpose of removing impurities. After pickling with dilute nitric acid, most of the generated nitrates are easily soluble in water and can be easily removed through subsequent cleaning steps. Impurities that are difficult to remove will not remain in the powder, ensuring the purity of the powder and facilitating accurate particle size test results. In addition, dilute nitric acid can also adjust the charge properties of the powder surface, increase the electrostatic repulsion between powder particles, and thus inhibit the agglomeration of particles. This helps to make the powder particles exist in a more dispersed state during the particle size test and improve the accuracy of the test results.

[0017] Preferably, the concentration of the dilute nitric acid is 2-5M.

[0018] Preferably, the powder is added into dilute nitric acid and stirred at a speed of 100-300 rpm for 5-10 min.

[0019] Preferably, the drying temperature is 50-60° C., and the drying time is 6-12 hours.

[0020] Preferably, in S1.4, the ratio of powder to deionized water in the prepared suspension is 1 g:20 ml.

[0021] Preferably, in S1.4, the concentration of the sodium hydroxide solution is 0.05-0.1M.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. In this powder particle size test method, hexadecyl mercaptan is added. Since the thiol group at one end can adsorb to the powder surface, and the long carbon chain at the other end forms a steric hindrance, the interaction between particles is reduced, agglomeration is reduced, and the powder is dispersed more evenly in the dispersion medium, which is conducive to accurate measurement of particle size. At the same time, it can also protect the powder from interference from external impurities, prevent particle aggregation, optimize the surface tension of the dispersion medium and the powder sedimentation performance, and improve the stability of the test process and the reliability of the results.

[0024] 2. In this powder particle size test method, acid washing can effectively remove various impurities in the powder. These impurities will interfere with the particle size test. After removal, the purity of the powder can be improved to ensure the accuracy of the test results. In addition, the acid washing process can adjust the surface charge of the powder, inhibit the agglomeration of particles, and allow the powder to exist better in a single particle state in the subsequent dispersion process, which is conducive to accurate measurement of the particle size. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. 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.

[0026] Embodiment 1: A method for testing the particle size of a powder, comprising the following steps:

[0027] S1.1. Sieve the powder to make the particle size of the powder 2μm;

[0028] S1.2, dissolving hexadecyl mercaptan in toluene to obtain a hexadecyl mercaptan solution with a concentration of 0.1 mM; adding powder to the hexadecyl mercaptan solution, stirring at 500 rpm for 16 h at room temperature, so that the mercaptan forms a molecular layer with a thickness of 1 nm on the surface of the powder; separating the powder by centrifugation at a speed of 4000 rpm for 20 min, and washing with hexane 5 times to remove unabsorbed mercaptan molecules;

[0029] S1.3, add the powder in S1.2 to 2M dilute nitric acid, stir at 300rpm for 10min, and soak for 4h; after pickling, rinse the powder with deionized water to remove residual acid and impurities; then soak the powder in anhydrous ethanol for 30min; after ethanol soaking, rinse the powder with deionized water, and dry at 60℃ for 12h to obtain pickled powder;

[0030] S1.4, mix the acid-washed powder with deionized water in a ratio of 1g:20ml to prepare a suspension; place the suspension on a magnetic stirrer, stir at a speed of 300rpm for 5min, and adjust the pH value of the suspension to neutral with a 0.1M sodium hydroxide solution;

[0031] S1.5. Place the suspension in S1.4 into an ultrasonic cleaning machine with an ultrasonic power of 100% and an external ultrasonic time of 10 minutes.

[0032] Embodiment 2: A method for testing the particle size of a powder, comprising the following steps:

[0033] S1.1. Sieve the powder to make the particle size of the powder 2μm;

[0034] S1.2, dissolving hexadecyl mercaptan in toluene to obtain a hexadecyl mercaptan solution with a concentration of 0.5 mM; adding powder to the hexadecyl mercaptan solution, stirring at 500 rpm for 16 h at room temperature, so that the mercaptan forms a molecular layer with a thickness of 1 nm on the surface of the powder; separating the powder by centrifugation at a speed of 4000 rpm for 20 min, and washing with hexane 5 times to remove unabsorbed mercaptan molecules;

[0035] S1.3, add the powder in S1.2 to 2M dilute nitric acid, stir at 300rpm for 10min, and soak for 4h; after pickling, rinse the powder with deionized water to remove residual acid and impurities; then soak the powder in anhydrous ethanol for 30min; after ethanol soaking, rinse the powder with deionized water, and dry at 60℃ for 12h to obtain pickled powder;

[0036] S1.4, mix the acid-washed powder with deionized water in a ratio of 1g:20ml to prepare a suspension; place the suspension on a magnetic stirrer, stir at a speed of 300rpm for 5min, and adjust the pH value of the suspension to neutral with a 0.1M sodium hydroxide solution;

[0037] S1.5. Place the suspension in S1.4 into an ultrasonic cleaning machine with an ultrasonic power of 100% and an external ultrasonic time of 10 minutes.

[0038] Embodiment 3: A method for testing the particle size of a powder, comprising the following steps:

[0039] S1.1. Sieve the powder to make the particle size of the powder 2μm;

[0040] S1.2. Dissolve hexadecyl mercaptan in toluene to obtain a hexadecyl mercaptan solution with a concentration of 1 mM; add powder to the hexadecyl mercaptan solution, and stir at 500 rpm for 16 h at room temperature to form a molecular layer of thiol with a thickness of 2 nm on the surface of the powder; separate the powder using a centrifuge at a speed of 4000 rpm for 20 min, and wash with hexane 5 times to remove unadsorbed thiol molecules;

[0041] S1.3, add the powder in S1.2 to 2M dilute nitric acid, stir at 300rpm for 10min, and soak for 4h; after pickling, rinse the powder with deionized water to remove residual acid and impurities; then soak the powder in anhydrous ethanol for 30min; after ethanol soaking, rinse the powder with deionized water, and dry at 60℃ for 12h to obtain pickled powder;

[0042] S1.4, mix the acid-washed powder with deionized water in a ratio of 1g:20ml to prepare a suspension; place the suspension on a magnetic stirrer, stir at a speed of 300rpm for 5min, and adjust the pH value of the suspension to neutral with a 0.1M sodium hydroxide solution;

[0043] S1.5. Place the suspension in S1.4 into an ultrasonic cleaning machine with an ultrasonic power of 100% and an external ultrasonic time of 10 minutes.

[0044] Embodiment 4: A method for testing the particle size of a powder, comprising the following steps:

[0045] S1.1. Sieve the powder to make the particle size of the powder 2μm;

[0046] S1.2, dissolving hexadecyl mercaptan in toluene to obtain a hexadecyl mercaptan solution with a concentration of 0.5 mM; adding powder to the hexadecyl mercaptan solution, stirring at 500 rpm for 16 h at room temperature, so that the mercaptan forms a molecular layer with a thickness of 1 nm on the surface of the powder; separating the powder by centrifugation at a speed of 4000 rpm for 20 min, and washing with hexane 5 times to remove unabsorbed mercaptan molecules;

[0047] S1.3, add the powder in S1.2 to 3M dilute nitric acid, stir at 300rpm for 10min, and soak for 4h; after pickling, rinse the powder with deionized water to remove residual acid and impurities; then soak the powder in anhydrous ethanol for 30min; after ethanol soaking, rinse the powder with deionized water, and dry at 60℃ for 12h to obtain pickled powder;

[0048] S1.4, mix the acid-washed powder with deionized water in a ratio of 1g:20ml to prepare a suspension; place the suspension on a magnetic stirrer, stir at a speed of 300rpm for 5min, and adjust the pH value of the suspension to neutral with a 0.1M sodium hydroxide solution;

[0049] S1.5. Place the suspension in S1.4 into an ultrasonic cleaning machine with an ultrasonic power of 100% and an external ultrasonic time of 10 minutes.

[0050] Comparative Example 1

[0051] Using the old method, take an appropriate amount of powder and dissolve it in deionized water (do not control the ratio of powder to deionized water), stir it evenly, and add it dropwise to the particle size analyzer for particle size testing.

[0052] Comparative Example 2

[0053] S1.1. Sieve the powder to make the particle size of the powder 2μm;

[0054] S1.2, add the powder to 3M dilute nitric acid, stir at 300rpm for 10min, and soak for 4h; after pickling, rinse the powder with deionized water to remove residual acid and impurities; then soak the powder in anhydrous ethanol for 30min; after ethanol soaking, rinse the powder with deionized water, and dry at 60℃ for 12h to obtain pickled powder;

[0055] S1.3, mix the acid-washed powder with deionized water in a ratio of 1g:20ml to prepare a suspension; place the suspension on a magnetic stirrer, stir at a speed of 300rpm for 5min, and adjust the pH value of the suspension to neutral with a 0.1M sodium hydroxide solution;

[0056] S1.4. Place the suspension in S1.4 into an ultrasonic cleaning machine with an ultrasonic power of 100% and an external ultrasonic time of 10 minutes.

[0057] Comparative Example 3

[0058] S1.1. Sieve the powder to make the particle size of the powder 2μm;

[0059] S1.2, dissolving hexadecyl mercaptan in toluene to obtain a hexadecyl mercaptan solution with a concentration of 0.5 mM; adding powder to the hexadecyl mercaptan solution, stirring at 500 rpm for 16 h at room temperature, so that the mercaptan forms a molecular layer with a thickness of 1 nm on the surface of the powder; separating the powder by centrifugation at a speed of 4000 rpm for 20 min, and washing with hexane 5 times to remove unabsorbed mercaptan molecules;

[0060] S1.3, add the powder in S1.2 to 3M sulfuric acid, stir at 300rpm for 10min, and soak for 4h; after pickling, rinse the powder with deionized water to remove residual acid and impurities; then soak the powder in anhydrous ethanol for 30min; after ethanol soaking, rinse the powder with deionized water, and dry at 60℃ for 12h to obtain acid-washed powder;

[0061] S1.4, mix the acid-washed powder with deionized water in a ratio of 1g:20ml to prepare a suspension; place the suspension on a magnetic stirrer, stir at a speed of 300rpm for 5min, and adjust the pH value of the suspension to neutral with a 0.1M sodium hydroxide solution;

[0062] S1.5. Place the suspension in S1.4 into an ultrasonic cleaning machine with an ultrasonic power of 100% and an external ultrasonic time of 10 minutes.

[0063] The present invention adopts a powder particle size testing method using acid washing and adding hexadecyl mercaptan, wherein the test items and test standards of the powder particle size testing method are as follows:

[0064] According to GB / T 32618-2016 standard, taking zirconium oxide dry powder and zirconium oxide calcined powder as examples, the corresponding absorption rate of zirconium oxide dry powder is 0 and the refractive index is 1.9-2.2, and the corresponding absorption rate of zirconium oxide calcined powder is 0 and the refractive index is 2.0-2.2; add water to the injector and stir at a speed of 2300-2800r / min, the instrument background is lower than 80 (particle size is less than 1μm, the background cannot exceed 60), the shading rate is 10-20, the internal super time is 1min, the power is 100%, and the particle size test is carried out.

[0065] The same sample was tested three times in parallel, the results of each test were recorded, and the average and mean square error of the three particle sizes were calculated.

[0066] According to the above standards, the particle sizes of the powders in the above Examples 1-4 and Comparative Examples 1-3 were tested, and the obtained data are shown in Tables 1 and 2:

[0067] Table 1 Particle size test data of zirconium oxide dry powder of Examples 1-4 and Comparative Examples 1-3

[0068]

[0069] Table 2 Particle size test data of zirconium oxide calcined powder of Examples 1-4 and Comparative Examples 1-3

[0070]

[0071] It can be seen from Table 1 and Table 2 that the particle size of the powders in Examples 1-4 exhibits a significantly low mean square error value; Taking Example 4 as the optimal example and combining it with Comparative Example 1, it can be seen that when the old method is used, the mean square error value of the particle size of the powder is significantly improved;

[0072] Failure to control the ratio of powder to deionized water may result in uneven dispersion of powder in the solution. If the powder concentration is too high, agglomerates are likely to form; in particle size testing, these agglomerates may be misjudged as large particles, thus affecting the accuracy of the measurement results; and when a large number of agglomerates exist, the dispersion of the test results will increase, significantly increasing the mean square error value; the uneven dispersion state will make the representativeness of the test sample worse, causing the randomness of the test results to increase, and failing to accurately reflect the true particle size distribution of the powder, resulting in large differences in the measurement results in different regions, which in turn affects the overall particle size average and mean square error.

[0073] Example 4 is the best example, and combined with Comparative Example 2, it can be seen that in the powder particle size test method, when hexadecyl mercaptan is removed, the mean square error value of the powder particle size is significantly improved;

[0074] Hexadecyl mercaptan forms a molecular layer on the surface of powder particles, which prevents the particles from approaching and agglomerating through steric hindrance. This mechanism of action is similar to the application of other dispersants in nanopowders, which inhibits particle agglomeration through steric hindrance, thereby improving the dispersion effect of the powder; after removing hexadecyl mercaptan, the attraction between particles (such as van der Waals force) is enhanced, making the particles more likely to agglomerate. The agglomerated particles are regarded as larger particles in the particle size test, and when some agglomerates are redispersed during the test, the discreteness of the particle size measurement results increases, and the mean square error significantly increases; after removing hexadecyl mercaptan, the surface properties of the powder particles change, which may reduce the dispersion stability of the particles in the dispersion medium and make them more likely to aggregate and settle, which will lead to large differences in particle concentration and agglomeration state at different positions and times during the test, thereby affecting the accuracy of the particle size measurement.

[0075] Hexadecyl mercaptan helps to improve the dispersion effect of powder in the dispersion medium, so that the powder particles are evenly distributed in the medium; after removing hexadecyl mercaptan, the powder particles may not be evenly dispersed, resulting in local concentrations that are too high or too low. During testing, particles in local high-concentration areas are prone to agglomeration, while particles in low-concentration areas may be diluted, which will cause large deviations in the measurement results and increase the mean square error of the particle size.

[0076] Example 4 is the best example, and combined with Comparative Example 3, it can be seen that in the powder particle size test method, when sulfuric acid is used instead of dilute nitric acid, the mean square error value of the powder particle size is significantly improved;

[0077] There are significant differences between sulfuric acid and dilute nitric acid in terms of oxidizability and acidity, which causes them to react with impurities in powders at different rates and degrees. For example, for some metal impurities, dilute nitric acid can quickly and fully dissolve and remove them, while sulfuric acid may react more slowly or fail to completely dissolve these impurities, resulting in the presence of residual impurities. These residual impurities will affect the particle size test results of the powder, causing the particle size average and mean square deviation to be abnormal. Sulfuric acid may change the charge distribution on the surface of the powder particles, resulting in changes in the electrostatic interaction between the particles. If the surface charge of the particles decreases, the electrostatic repulsion weakens, and the particles are more likely to agglomerate, thereby affecting the accuracy of the particle size measurement and increasing the mean square deviation of the particle size. The addition of sulfuric acid to the dispersion medium may change the properties of the dispersion medium, such as surface tension, viscosity, etc. These changes in properties will affect the dispersion stability of the powder particles in the dispersion medium, making the particles more likely to aggregate or settle, which in turn leads to deviations in the particle size test results.

[0078] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and the above embodiments and the descriptions in the specification are only preferred examples of the present invention and are not used to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A method for testing the particle size of a powder, characterized in that: The following steps are involved: S1.1, sieve the powder to make the powder particle size 0.1-1000μm; S1.2, dissolving hexadecyl mercaptan in toluene to obtain a hexadecyl mercaptan solution; adding powder to the hexadecyl mercaptan solution, stirring at room temperature at a speed of 300-600 rpm for 12-24 hours, so that the mercaptan forms a molecular layer on the surface of the powder; separating the powder by a centrifuge, and washing with hexane for 3-5 times to remove unabsorbed mercaptan molecules; S1.3, acid-washing the powder in S1.2 to remove colored impurities and obtain acid-washed powder; S1.4, mix the acid-washed powder with deionized water to form a suspension; place the suspension on a magnetic stirrer, stir at a speed of 300-400 rpm for 5 minutes, and adjust the pH value of the suspension to neutral with sodium hydroxide solution; S1.

5. Place the suspension in S1.4 into an ultrasonic cleaning machine with an ultrasonic power of 100% and an external ultrasonic time of 10 minutes.

2. The method for measuring the particle size of powder according to claim 1, characterized in that: In the S1.2, the concentration of the hexadecyl mercaptan solution is 0.1-1 mM.

3. The method for measuring the particle size of powder according to claim 1, characterized in that: In S1.2, the thickness of the molecular layer formed by thiol on the surface of the powder is 1-2 nm.

4. The method for measuring the particle size of powder according to claim 1, characterized in that: In S1.2, the rotation speed of the centrifuge is 3000-5000 rpm, and the centrifugation time is 10-20 min.

5. The method for measuring the particle size of powder according to claim 1, characterized in that: In S1.3, the powder is pickled by adding the powder into dilute nitric acid, stirring, and standing to soak for 1-4 hours; after pickling, the powder is rinsed with deionized water to remove residual acid and impurities; the powder is then soaked in anhydrous ethanol for 10-30 minutes; after the ethanol soaking is completed, the powder is rinsed with deionized water, and then vacuum dried to obtain the pickled powder.

6. The method for measuring the particle size of powder according to claim 5, characterized in that: The concentration of the dilute nitric acid is 2-5M.

7. The method for measuring the particle size of powder according to claim 5, characterized in that: The powder is added into dilute nitric acid and stirred at a speed of 100-300 rpm for 5-10 min.

8. The method for testing the particle size of powder according to claim 5, characterized in that: The drying temperature is 50-60° C., and the drying time is 6-12 hours.

9. The method for measuring the particle size of powder according to claim 1, characterized in that: In the above-mentioned S1.4, the ratio of powder to deionized water in the prepared suspension is 1 g:20 ml.

10. The method for testing the particle size of powder according to claim 1, characterized in that: In S1.4, the concentration of the sodium hydroxide solution is 0.05-0.1M.

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