Zirconia Slurry Evaluation through Sand Milling

To achieve nanometer-level standards for zirconia, a wet grinding process is required. This not only ensures the desired nanometer level but also results in a well-concentrated and stable particle distribution. It minimizes consumption and equipment wear during the grinding process.

For this experiment, the following equipment was employed: a domestic NT-V series 1L laboratory sand mill, equipped with a silicon carbide cylinder and a rotor made of zirconia material, as well as a material disperser, Malvern laser particle size detection, disposable pipettes, measuring cups, and cleaning equipment.

Pre-Grinding Equipment Cleaning

For the experimental zirconia, the final particle size requirement is D50-200nm, representing a relatively small particle size range.

Firstly, we perform particle size testing on the incoming zirconia material to determine its initial particle size data. Based on this data, we select the size of zirconia beads for grinding. This allows us to compare the particle size before and after grinding, determining the effectiveness of the process.

Before particle size testing, it is necessary to subject the incoming zirconia material to ultrasonic dispersion. This dispersion aims to subject the fluid material to thousands of shear and high-frequency mechanical effects per minute, ensuring efficient mixing, dispersion, and homogenization. This prepares the material's physical state for subsequent testing.

Ultrasonic Dispersion of Incoming Material

Original Particle Size Testing

The particle size laser detector used by the manufacturer is produced by Malvern Instruments, a globally recognized company for quality testing and control in various fields.

Through Malvern laser particle size detection, we determined the original particle size of the incoming material to be 3μm. Based on this information and the characteristics of the incoming material, we quickly selected the size of zirconia balls for grinding, reducing both experimental time and material usage.

Measurement of Original Particle Size using Malvern Detector

In this case, we chose 0.3mm 95Yttria-stabilized zirconia balls.

Five-Minute Pre-Milling Dispersion

With the selected equipment model and zirconia balls, we move on to the pre-milling dispersion of the incoming material. Pre-milling dispersion involves initially mixing the zirconia slurry to break up any agglomerates, ensuring uniformity and preparing it for the grinding process. Since the incoming material has already undergone pre-dispersion, a 5-minute dispersion is sufficient in this case.

Initial Grinding Test after Thirty Minutes

After dispersion, the zirconia slurry is transferred to the grinding machine through a measuring cup, entering the initial grinding stage. This stage typically lasts for 15-30 minutes, depending on the results of the original particle size test. Some materials may require longer grinding times, up to 1-2 hours, for periodic testing. For zirconia, based on its physical properties and the measured particle size, we decided on a 30-minute initial grinding.

Additionally, maintaining the temperature within the drum during grinding is crucial, as it directly affects the test results and may lead to chemical changes in the material. For this experiment, we controlled the drum temperature to ≤50°C with a rotation speed of 2500r/min.

The material is discharged statically in this experiment. A large-area discharge device is installed inside the hollow rotor, utilizing centrifugal force generated during high-speed rotation to propel the grinding balls outward. This design ensures efficient discharge, prevents blockages, and includes internal deformation prevention structures, thus preserving the integrity of the discharge device.

After 30 minutes, a small amount of zirconia is extracted using a pipette for the first post-grinding test. Malvern particle size detection revealed a particle size of 700nm, leading us to the secondary grinding stage.

Data from the Thirty-Minute Grinding Test

Secondary Grinding Test after Sixty Minutes

After 60 minutes, we conducted another test, resulting in a particle size of 280nm as per Malvern laser particle size detection. Based on the previous two tests, we anticipated achieving the desired grinding effect after an additional 30 minutes.

Data from the Sixty-Minute Grinding Test

Tertiary Grinding Test after Ninety Minutes

After 90 minutes and three rounds of grinding tests, the zirconia slurry achieved a particle size of 150 nanometers, meeting the customer's specified particle size range and exceeding expectations.

Data from the Ninety-Minute Grinding Test

With this, the entire grinding test process concludes, taking a total of 90 minutes. The next step is to package the material into designated containers and send it to the customer along with the test report.

From this testing report, it is evident that the zirconia grinding test met the customer's expectations, paving the way for swift production scaling. This also enables rational evaluation of production costs, budgets, investments, and processing times, among other factors.

Below is the inspection report for this evaluation (for other requirements, please contact the editor).