Alumina fineness testing method suitable for electric porcelain production

Abstract

A method for testing the fineness of alumina in electrical porcelain production, belonging to the field of materials testing, involves mixing 100g of alumina sample with 300ml of deionized water, adding 30ml of sodium hexametaphosphate dispersant, and ultrasonically sonicating at 40kHz for 30min. The mixture is then poured into a 320-mesh standard sieve and washed until the water is clear. After standing, the supernatant is poured off and heated to constant weight. The fineness is calculated based on the mass difference. Addressing the issue of alumina powder agglomeration during testing, leading to large deviations in fineness results, this method effectively disperses agglomerated alumina particles by ultrasonically dispersing the alumina sample with the dispersant, obtaining a uniform and stable suspension. The wet sieving method is used to determine the sieve residue of the suspension, significantly improving the reproducibility and accuracy of the test, providing more reliable test results for production guidance; it also improves the quality monitoring standards for alumina raw materials in the electrical porcelain industry, providing technical support for developing more precise testing specifications.

Description

Technical Field

[0001] This invention belongs to the field of materials testing technology, specifically relating to a method for testing the fineness of alumina suitable for the production of electrical porcelain. Background Technology

[0002] Alumina, an indispensable raw material in the production of ultra-high voltage electrical porcelain, plays a crucial role in improving the service performance of porcelain insulators due to its excellent electrical insulation, heat resistance, and chemical stability. In the actual production process of electrical porcelain products, the fineness testing of raw material powder is the primary step in ensuring product quality. Wet sieving, as a common standard method for evaluating alumina fineness, relies on dispersing the powder in a liquid medium and defining the upper limit of fineness through physical sieving. However, the molecular attraction and electrostatic forces between fine alumina particles easily induce physical agglomeration. Agglomerated particles appear as large particles during testing, leading to inflated fineness results. Given the specific surface activity and fineness characteristics of alumina raw materials (the molecular attraction and electrostatic forces between particles easily induce agglomeration, and the ordinary wet sieving method has a large error and cannot break up the agglomerates), we propose an alumina fineness testing method suitable for electrical porcelain production. This method effectively disperses agglomerated alumina particles, obtains accurate and reliable fineness results, improves the quality monitoring standards for alumina raw materials in the electrical porcelain industry, and provides technical support for the development of more precise testing specifications. Summary of the Invention

[0003] The purpose of this invention is to provide a method for testing the fineness of alumina in the production of electrical porcelain, which can solve the defects of existing testing methods and reduce testing errors.

[0004] The technical solution adopted is: A method for testing the fineness of alumina suitable for the production of electrical porcelain includes the following steps: (1) Weigh 100g of the alumina sample powder to be tested, dried to constant weight, place the weighed powder in a 500ml clean and dried beaker, add 300ml of deionized water, and stir evenly to obtain a slurry. The deionized water must have a conductivity ≤30µS / cm.

[0005] (2) Add 30 ml of sodium hexametaphosphate dispersant with a concentration of 8% (mass fraction) to the slurry mixed in step (1), and then perform ultrasonic treatment. The ultrasonic treatment frequency is fixed at 40 kHz and the ultrasonic treatment time is 30 min.

[0006] (3) Pour the slurry prepared in step (2) directly into a 320-mesh standard sieve. Place the sieve in a container filled with clean water, gently tap the 320-mesh standard sieve with your hand, and rinse the alumina sample in the sieve with running water until the water is clear. Transfer the residue from the sieve to a porcelain dish using a wash bottle, let it stand for half an hour, then pour off part of the upper aqueous solution. Place the porcelain dish containing the residue into an oven at a temperature of 105℃-110℃ for 1-2 hours until the weight is constant. Then place it in a desiccator to cool to room temperature and weigh it.

[0007] (4) The fineness of alumina is calculated according to the following formula.

[0008]

[0009] In the formula: A Fineness of alumina (in %).

[0010] m 1 Mass of the porcelain dish (in grams).

[0011] m 2 Mass of porcelain dish and residue (in grams).

[0012] Its advantages are: This method addresses the problem of alumina powder agglomeration during testing, which leads to large deviations in fineness results. By mixing the alumina sample with a dispersant and then subjecting it to ultrasonic dispersion, the agglomerated alumina particles are effectively dispersed, resulting in a uniform and stable suspension. The wet sieving method is used to determine the sieve residue of the suspension, which significantly improves the reproducibility and accuracy of the test, providing more reliable test results to guide production. It also improves the quality monitoring standards for alumina raw materials in the electrical porcelain industry and provides technical support for the development of more precise testing specifications. Attached Figure Description

[0013] Figure 1 This image shows the microstructure and magnified details of alumina powder used in electrical porcelain.

[0014] Figure 2 The effect of dispersant content and ultrasonic time on the fineness of alumina.

[0015] Figure 3 This illustration shows that the fineness of the three alumina samples with different particle sizes in the examples was reduced to the minimum. Detailed Implementation

[0016] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings: In this embodiment, the materials are three types of alumina powder with different particle sizes. The original crystals D of the three types of alumina powder... 50The particle sizes are: 2.9 μm (sample 1), 3.4 μm (sample 2), and 3.8 μm (sample 3).

[0017] In this embodiment, after the alumina samples of different particle sizes were dried to constant weight, 11 portions of each sample were taken, each portion being 100g, for a total of 33 portions. Each portion was dissolved in 300ml of deionized water and stirred evenly to prepare 33 slurries.

[0018] This embodiment was conducted using two methods. In method one, a sodium hexametaphosphate dispersant (an aqueous solution of sodium hexametaphosphate) with a mass fraction of 8% was added to each portion of the mixed slurry. The amounts added to six portions of each sample were 0 ml, 10 ml, 20 ml, 30 ml, 40 ml, and 50 ml, respectively. All samples were then subjected to ultrasonic treatment at a frequency of 40 kHz for 30 minutes. The experimental results are attached. Figure 2 As shown in (a).

[0019] In Scheme Two, 15 portions of the mixed slurry from the three samples were first mixed with 30 ml of a prepared sodium hexametaphosphate dispersant at a mass concentration of 8%. Then, ultrasonic treatment was performed at a frequency of 40 kHz for 10, 20, 30, 40, and 50 minutes for each sample. The experimental results are attached. Figure 2 As shown in (b).

[0020] Next, each portion of slurry from Scheme 1 and Scheme 2 in this embodiment was directly poured into a 320-mesh standard sieve. The sieve was placed in a container filled with clean water, and the sieve was gently tapped by hand to rinse the alumina sample inside the sieve with running water until the water was clear. The residue from each portion of slurry was transferred to a porcelain dish using a wash bottle, and after standing for half an hour, part of the upper aqueous solution was poured off. The porcelain dish containing the residue was then placed in an oven. It was dried to constant weight at an oven temperature of 105℃-110℃ for 1-2 hours. After cooling to room temperature in a desiccator, it was weighed. In this embodiment, the alumina fineness result is calculated according to the following formula.

[0021]

[0022] In the formula: A Fineness of alumina (in %) m 1 Mass of the porcelain dish (in grams); m 2 Mass of porcelain dish and residue (in grams).

[0023] In this embodiment, Figure 1 Alumina powder for use in the production of electrical porcelain. Figure 1 In (a), alumina powder exhibits a significant tendency to agglomerate, with naturally agglomerated particles reaching up to 100 μm. Figure 1 (b) shows that individual alumina particles exhibit distinct hexagonal plate-like features, which is a typical morphology of high-temperature calcined alumina powder.

[0024] In this embodiment, Figure 2 Figure (a) shows the effect of dispersant dosage on the fineness of alumina. When the ultrasonic time was 30 min, samples of different particle sizes showed a consistent trend. The alumina fineness result was lowest when the amount of dispersant solution added reached 20-30 ml. As the amount of dispersant added further increased, the alumina fineness result increased. This demonstrates that an appropriate amount of dispersant can effectively reduce the surface tension of particles, weaken the van der Waals forces and electrostatic attraction between particles, making it easier for particles to disperse in the liquid phase, reducing the retention of large particles on the sieve due to agglomeration, and thus improving the accuracy of the test results. However, when the amount of dispersant added exceeds the optimal concentration, excessive sodium hexametaphosphate may induce flocculation between particles, causing alumina particles to recombine into larger flocs, ultimately leading to a rebound in the fineness result.

[0025] Figure 2 Figure (b) shows the effect of ultrasonic time on fineness results under the condition of 30 ml dispersant addition. For alumina samples with relatively large particle sizes, the fineness results show a continuous decreasing trend with the extension of ultrasonic time, and tend to stabilize and reach the lowest point after 30 min of treatment. This indicates that the ultrasonic intensity of 30 min is sufficient to provide the energy required to overcome the van der Waals forces between micron-sized particles, causing the macroscopic agglomerates to be fully reduced to the original grains, thus passing smoothly through the sieve. However, for the alumina samples with the smallest particle size, the fineness results decreased significantly in the first 30 min of ultrasonic treatment; but when the treatment time was extended to 40 min, the fineness results of some samples rebounded. This result can be attributed to the extremely high specific surface energy of the ultrafine particles.

[0026] In this embodiment, when 30 ml of 8% sodium hexametaphosphate dispersant was added to the slurry of the three samples and the ultrasonic time was not less than 30 min, the fineness of the three alumina samples with different particle sizes was reduced to the lowest level.

[0027] The specific embodiments of the present invention have been described in detail above. The addition of dispersants and ultrasonic treatment effectively dispersed alumina particle agglomerates, significantly reducing the influence of agglomerated particles on the fineness results, thus more accurately reflecting the actual fineness composition of the powder. The alumina fineness testing method for electrical porcelain production described in this invention is convenient and feasible. This method has high precision and good repeatability. By employing methods such as ultrasound and dispersants, it achieves accurate and reliable detection of alumina powder fineness test results, and is practical.

Claims

1. A method for testing the fineness of alumina suitable for the production of electrical porcelain, characterized in that... Includes the following steps: (1) Weigh 100g of the alumina sample powder to be tested, dried to constant weight, and stir 100g of alumina sample powder with 300ml of deionized water to obtain a slurry. (2) Add 30 ml of sodium hexametaphosphate dispersant to the slurry mixed in step (1) and sonicate. (3) Pour the slurry processed in step (2) into a 320-mesh standard sieve; place the sieve in a container filled with clean water, rinse the alumina sample in the sieve with running water until the water is clear; transfer the residue to a container, let it stand for half an hour, pour off part of the upper aqueous solution, dry the container containing the residue to constant weight and cool it to room temperature, and weigh it. (4) The fineness of alumina is calculated according to the following formula; ; A: Fineness of alumina, expressed in % . m1: The mass of the container, in grams; m2: Mass of container and residue, in grams.

2. The method for testing the fineness of alumina suitable for the production of electrical porcelain according to claim 1, characterized in that... Includes the following steps: The conductivity of the deionized water is ≤30µS / cm.

3. The method for testing the fineness of alumina suitable for the production of electrical porcelain according to claim 1, characterized in that... Includes the following steps: The sodium hexametaphosphate dispersant is an 8% aqueous solution of sodium hexametaphosphate, where the concentration is a mass fraction.

4. The method for testing the fineness of alumina suitable for the production of electrical porcelain according to claim 1, characterized in that... Includes the following steps: The ultrasonic treatment frequency was 40 kHz, and the ultrasonic treatment time was 30 min.

5. The method for testing the fineness of alumina suitable for the production of electrical porcelain according to claim 1, characterized in that... Includes the following steps: In step (3), an oven is used for drying until the weight is constant.

6. The method for testing the fineness of alumina suitable for the production of electrical porcelain according to claim 5, characterized in that... Includes the following steps: The oven temperature is 105-110℃, and the time is 1-2 hours.

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