Pretreatment method for iron phosphate laser particle size detection

Abstract

The invention provides a pretreatment method for iron phosphate laser particle size detection, and relates to the technical field of material analysis and detection. The method comprises the following steps: weighing 0.02-0.05 g of iron phosphate powder, adding a dispersing agent consisting of 1-3ml of absolute ethyl alcohol and 45-55ml of deionized water, and treating for 0.5-2 minutes by adopting a synergistic dispersion mode in which stirring and ultrasound are synchronously carried out. Through the synergistic effect of mechanical stirring and ultrasonic cavitation, sufficient dispersion of iron phosphate particles is realized within an extremely short time, and the problems of detection environment instability and data distortion caused by heating due to long-time operation of ultrasonic equipment are fundamentally solved. According to the method, the accuracy, stability and reproducibility of data during batch detection are remarkably improved, the processing efficiency is improved, expensive equipment does not need to be transformed, the cost is low, and the method is easy to popularize and use in the industry.

Description

Technical Field

[0001] This invention relates to the field of materials analysis and testing technology, specifically to a pretreatment method for laser particle size analysis of iron phosphate. Background Technology

[0002] Laser particle size analyzers are key equipment for determining the particle size distribution of powder materials, and the accuracy of their wet-method detection results is highly dependent on the effectiveness of sample pretreatment. For iron phosphate (especially high-purity iron phosphate used in lithium-ion battery cathode materials), its particle size distribution directly affects the electrochemical performance of the product; therefore, accurate particle size detection is crucial.

[0003] Currently, standard pretreatment methods for laser particle size analysis of iron phosphate typically include: sampling, adding a dispersant (such as a mixture of anhydrous ethanol and water), and ultrasonic dispersion. Ultrasonic dispersion utilizes the intense shock waves and microjets generated by cavitation to break up particle agglomerates, and is the core step in ensuring sufficient particle dispersion. There is a general consensus among those skilled in the art that longer ultrasonic time usually means more thorough dispersion. Therefore, existing technologies generally require longer ultrasonic times (usually no less than 5 minutes) to ensure effective dispersion, and relevant operating procedures and academic literature also emphasize and extend the ultrasonic time as a primary means of ensuring detection accuracy.

[0004] However, in long-term industrial batch testing practice, the applicant has found that this traditional method has inherent defects: when multiple samples need to be tested continuously, the long-term high-power operation of the ultrasonic equipment will cause the transducer to overheat severely and the water temperature in the ultrasonic tank to rise significantly. This thermal effect will bring the following problems: (1) Decreased dispersion stability: The temperature rise may change the physicochemical properties of the dispersant (such as surface tension and viscosity) and exacerbate the evaporation of the solvent, destroying the established dispersion equilibrium and causing the particles to re-aggregate. (2) Ultrasonic energy attenuation: The heat generated by the transducer will reduce its conversion efficiency, resulting in a decrease in the actual ultrasonic power applied to the sample and a weakening of the cavitation effect. (3) Increased measurement error: The above factors together lead to poor repeatability of the test results and large data deviations between parallel samples, especially when tested continuously, the measured particle size of the last few samples is significantly larger. (4) Low efficiency: Each sample needs to wait for the equipment to cool down or for a long ultrasonic time, which seriously reduces the efficiency of batch testing.

[0005] Therefore, the field has been pursuing a balance between longer ultrasound time and errors caused by equipment heating, and there is an urgent need for a preprocessing method that can fundamentally avoid the impact of equipment heating, while ensuring detection accuracy and repeatability, and significantly improving detection efficiency. Summary of the Invention

[0006] The purpose of this invention is to provide a pretreatment method for laser particle size detection of iron phosphate, which fundamentally avoids the data distortion problem caused by the continuous heating of ultrasonic equipment, thereby ensuring the accuracy and stability of data during batch detection and significantly improving detection efficiency.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A pretreatment method for laser particle size detection of iron phosphate includes the following steps: S1. Sampling: Weigh 0.02-0.05g of ferric phosphate powder into a beaker; S2. Preparation of dispersion system: Add 1-3 ml of anhydrous ethanol and 45-55 ml of deionized water to the beaker to form a mixture; S3. Co-dispersion treatment: Place the beaker containing the mixture in an ultrasonic cleaner equipped with a magnetic stirring device, and simultaneously start the magnetic stirring and ultrasonic treatment so that the stirring and ultrasonic treatment work together on the dispersion system; wherein, the rotation speed of the magnetic stirring is 300-600 rpm, the power of the ultrasonic treatment is 180-300W, and the treatment time is 0.5-2 minutes. Then the dispersion after the above treatment is used for laser particle size analyzer detection; that is: S4, detection: the dispersion after step S3 is quickly transferred to the sample cell of the laser particle size analyzer and the particle size distribution is immediately detected.

[0008] In this invention, further, in step S3, the magnetic stirring and ultrasonic treatment are carried out simultaneously, and dispersion is achieved through the synergistic effect of mechanical shear force and cavitation effect.

[0009] In this invention, further, in step S3, the processing time is 0.8-1.2 minutes.

[0010] In this invention, further, in step S3, the processing time is 1 minute.

[0011] In this invention, further, in step S3, the power of the ultrasonic treatment is 200-280W.

[0012] In this invention, further, in step S3, the power of the ultrasonic treatment is 240W. In this invention, further, in step S3, the rotation speed of the magnetic stirring is 400-550 rpm.

[0013] In this invention, further, in step S3, the rotation speed of the magnetic stirring is 500 rpm.

[0014] The present invention also proposes an apparatus system for implementing the above-described method, comprising: a laser particle size analyzer, an ultrasonic cleaner, and a magnetic stirring device disposed in the ultrasonic tank of the ultrasonic cleaner.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: (1) This invention significantly reduces the ultrasonic time from more than 5 minutes to less than 2 minutes, eliminating the long-term operation of the main heat source from the source. At the same time, the introduction of stirring promotes the macroscopic flow and thermal convection of the liquid, greatly accelerating the diffusion of the trace heat generated by ultrasonic energy and avoiding local overheating. This allows the ultrasonic tank water temperature to be maintained below 27°C when processing multiple samples continuously (as shown in Examples 1-3), thus completely avoiding the serious distortion problem in the traditional method (Comparative Example 1) where the D50 value drifts from 2.14μm to 2.65μm due to the water temperature rising to 42°C. This ensures the stability of the detection environment and fundamentally improves the stability and reproducibility of the detection results (the standard deviation SD of the D50 value is less than 0.011).

[0016] (2) This invention creatively combines magnetic stirring with ultrasonic treatment simultaneously, resulting in a synergistic effect of "1+1 >> 2". The macroscopic shear force provided by magnetic stirring can not only quickly break up large soft agglomerates and make the particles uniformly suspended, but more importantly, it continuously and uniformly delivers the particle group to the area where the ultrasonic cavitation effect is strongest, greatly improving the utilization rate of ultrasonic energy; while the high-energy micro-jets and shock waves generated by the ultrasonic cavitation effect can effectively depolymerize hard agglomerates that are difficult to solve by mechanical stirring. The two complement each other in real time, so that the processing effect of this invention in only 1 minute far exceeds that of traditional ultrasound in 5 minutes and any comparative examples of step-by-step processing (comparative examples 2-4) in terms of data stability (SD value) and prevention of particle agglomeration (Span value), thereby maximizing the degree of dispersion in a very short time.

[0017] (3) This invention significantly improves the efficiency and economic benefits of batch testing: thanks to the exponential increase in dispersion effect per unit time brought about by the above-mentioned synergistic effect, the pretreatment time of a single sample is shortened from more than 5 minutes to less than 2 minutes, and the efficiency is improved by more than 60%. This not only saves the time of a single test, but also fundamentally solves the problem of equipment overheating, so that batch continuous testing can be carried out continuously without waiting for the equipment to cool down, which greatly liberates manpower and equipment capacity, reduces the testing cost per unit sample, and has significant economic benefits.

[0018] (4) The solution of this invention cleverly utilizes the modular combination of existing laboratory equipment. It does not require modification of the expensive laser particle size analyzer host. It can be achieved simply by adding a low-cost magnetic stirring device to the most common ultrasonic cleaner in the laboratory. This improvement does not involve designing a completely new and complex instrument. Therefore, it has strong universality and operability. Any laboratory can upgrade its pretreatment process at almost zero cost. It is very easy to promote and popularize in this industry and has extremely high practical value and commercial prospects.

[0019] In summary, this invention, by creatively employing a "stirring-ultrasonic synergistic dispersion" mechanism, not only overcomes the technical challenge of data distortion caused by equipment heating, but also significantly improves the accuracy, stability, and efficiency of detection through a highly efficient synergistic effect. The solution is simple and easy to implement, with significant economic benefits, and possesses outstanding substantive features and remarkable progress. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and comparative examples. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0021] All experiments in this embodiment were conducted in an air-conditioned environment at 25±2℃ to eliminate interference from ambient temperature. The ultrasonic equipment used was a KQ-300DE CNC ultrasonic cleaner with a rated power of 300W and a built-in magnetic stirring device. The laser particle size analyzer was a Malvern Mastersizer 3000. Experimental material description: The iron phosphate powder used in this invention is a battery-grade positive electrode material, specifically purchased from Guizhou Anda Technology Energy Co., Ltd. Example 1

[0022] S1. Using an analytical balance of 0.01 g / mL, accurately weigh 0.03 g of ferric phosphate powder into a 100 ml beaker.

[0023] S2. Use a graduated cylinder to transfer 2 ml of anhydrous ethanol into a beaker, moisten the powder, and then add 50 ml of deionized water.

[0024] S3. Place a 2.5cm PTFE magnetic stir bar in the beaker, then place the beaker in the ultrasonic tank of an ultrasonic cleaner with a built-in magnetic stirring device. After securing the beaker, simultaneously start the magnetic stirring (set the speed to 500 rpm) and ultrasonic dispersion (set the power to 240W), and process for 1 minute. Record the water temperature at this time as 25℃.

[0025] S4. After processing, immediately use a dropper to draw up the dispersion and inject it into the sample cell of the laser particle size analyzer for particle size detection. Analyze each sample three times and take the average value. Example 2

[0026] This embodiment is basically the same as Embodiment 1, with only some parameters changed: S1. Sampling: Weigh 0.02g of ferric phosphate powder into a 100ml beaker.

[0027] S2. Preparation of dispersion system: Use a graduated cylinder to transfer 1 ml of anhydrous ethanol into a beaker, wet the powder, and then add 45 ml of deionized water.

[0028] S3. Collaborative dispersion treatment: Simultaneously start magnetic stirring and ultrasonic dispersion, set the magnetic stirring speed to 300 rpm, the ultrasonic power to 180W, and the processing time to 0.5 minutes.

[0029] S4. Detection: Same as in Example 1. Example 3

[0030] S1. Sampling: Weigh 0.05g of ferric phosphate powder into a 150ml beaker.

[0031] S2. Preparation of dispersion system: Use a graduated cylinder to transfer 3 ml of anhydrous ethanol into a beaker, wet the powder, and then add 55 ml of deionized water.

[0032] S3. Collaborative dispersion treatment: Simultaneously start magnetic stirring and ultrasonic dispersion, set the magnetic stirring speed to 600 rpm, the ultrasonic power to 300W, and the processing time to 2 minutes.

[0033] S4. Detection: Same as in Example 1.

[0034] Comparative Example 1 (Traditional Long-Term Ultrasound) Steps S1, S2, and S4 are the same as in Example 1.

[0035] S3. Place the beaker in the ultrasonic cleaner, turn on only the ultrasonic dispersion, set the power to 240W, and the processing time to 5 minutes. Test the 1st, 3rd, and 5th samples respectively, and record the water temperature before each ultrasonic treatment.

[0036] Comparative Example 2 (stirring first, then sonicating) Steps S1, S2, and S4 are the same as in Example 1.

[0037] S3. First, place the beaker on a magnetic stirrer and stir (500 rpm) for 1 minute, then transfer it to an ultrasonic cleaner and ultrasonically treat it separately (240W) for 1 minute.

[0038] Comparative Example 3 (ultrasound first, then stirring) Steps S1, S2, and S4 are the same as in Example 1.

[0039] S3. First, place the beaker in an ultrasonic cleaner and ultrasonically treat it separately (240W) for 1 minute, then transfer it to a magnetic stirrer and stir (500 rpm) for 1 minute.

[0040] Comparative Example 4 (Asynchronous stirring and sonication) Steps S1, S2, and S4 are the same as in Example 1.

[0041] S3. Place the beaker in the equipment and alternate between stirring and sonication: stir for 10 seconds, then sonicate for 10 seconds, and repeat this cycle. The total processing time is still 1 minute.

[0042] Experimental Example: Comparative Analysis of Effects For each of the above groups of experiments, batch testing was performed on 5 consecutive samples, and the key data (D50, μm) were recorded as shown in the table below:

[0043] Based on the above experimental results, we know that: (1) The method of the present invention solves the problem of equipment overheating: the water temperature of the ultrasonic tank in all embodiments (1-3) of the present invention is always below 27°C, with almost no temperature rise. In contrast, the water temperature of Comparative Example 1 (conventional method) rises to 42°C, and that of Comparative Example 3 (ultrasound first) also rises to 38°C. This directly proves that the synergistic method of "synchronous stirring-ultrasound" can efficiently disperse energy, greatly reduce the thermal effect caused by localized energy accumulation, and fundamentally solve the problem of equipment overheating.

[0044] (2) The standard deviation (SD) of the D50 values ​​measured in Examples 1-3 were all less than 0.011, which was much lower than that of all comparative examples. This indicates that the method of the present invention has excellent reproducibility and stability in continuous detection. In Comparative Example 1, the D50 value drifted from 2.14 μm to 2.65 μm, proving that heating did indeed cause serious distortion of the results.

[0045] (3) Although the effects of Comparative Examples 2, 3, and 4 (stepwise or alternating treatment) were better than those of Comparative Example 1, they were all far worse than those of Examples 1-3, which were treated simultaneously. This strongly proves that "simultaneous processing" is the key to the present invention, and its effect is not a simple superposition of the effects of stirring and ultrasound, but rather produces an unexpected synergistic effect.

[0046] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A pretreatment method for laser particle size detection of iron phosphate, characterized in that, Includes the following steps: S1. Sampling: Weigh 0.02-0.05g of ferric phosphate powder into a beaker; S2. Preparation of dispersion system: Add 1-3 ml of anhydrous ethanol and 45-55 ml of deionized water to the beaker to form a mixture; S3. Co-dispersion treatment: Place the beaker containing the mixture in an ultrasonic cleaner equipped with a magnetic stirring device, and simultaneously start the magnetic stirring and ultrasonic treatment so that the stirring and ultrasonic treatment work together on the dispersion system; wherein, the rotation speed of the magnetic stirring is 300-600 rpm, the power of the ultrasonic treatment is 180-300W, and the treatment time is 0.5-2 minutes. The dispersion after the above treatment was then used for laser particle size analysis.

2. The method according to claim 1, characterized in that, In step S3, the magnetic stirring and ultrasonic treatment are carried out simultaneously, and dispersion is achieved through the synergistic effect of mechanical shear force and cavitation effect.

3. The method according to claim 1, characterized in that, In step S3, the processing time is 0.8-1.2 minutes.

4. The method according to claim 3, characterized in that, In step S3, the processing time is 1 minute.

5. The method according to claim 1, characterized in that, In step S3, the power of the ultrasonic treatment is 200-280W.

6. The method according to claim 5, characterized in that, In step S3, the power of the ultrasonic treatment is 240W.

7. The method according to claim 1, characterized in that, In step S3, the rotation speed of the magnetic stirrer is 400-550 rpm.

8. The method according to claim 7, characterized in that, In step S3, the magnetic stirring speed is 500 rpm.

9. An apparatus system for implementing the method of any one of claims 1-8, characterized in that, include: A laser particle size analyzer, an ultrasonic cleaner, and a magnetic stirring device disposed in the ultrasonic tank of the ultrasonic cleaner.

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