Abstract The laboratory report examines the effect of ball milling on particle size distribution with the increasing time. Ball milling is a commonly used grinding method to reduce the size of particles in various materials. The study aims to understand the relationship between milling time and the resulting particle size distribution. The experimental results demonstrate that the particle size decreases as the milling time increases. The distribution becomes narrower, indicating a more uniform particle size. Keywords: particle size distribution, ball milling, size reduction, grinding Introduction Objective: ● To study the variation of the particle size distribution of aluminum oxide using a ball milling ● To analyze the effect of milling time on the particle size distribution (PSD) ● To compare the cumulative undersize, oversize Log Normal and Rosin-Rammler distributions for different time periods Hypothesis: It is expected that particle sizes decrease with the increasing time of ball milling. The frequency distribution of particle size might not obtain an accurate unimodal shape. Undersize or oversize cumulative distribution graphs may give more accurate results rather than frequency distribution. In log-normal and Rosin-Rammler distribution, the geometric mean, the geometric standard deviation, the scale parameter, and the shape parameters might have different patterns with milling time. Theory: Grinding is a process of particle size reduction, frequently used on laboratory and industrial scales. Particle size reduction is required when the particles are large, the sample is not homogeneous, etc. Processes such as analysis, division, and mixing require the samples to be small, uniform, and smooth [1]. The operating principles of laboratory mills for size reduction vary. The breaking characteristics of the sample material are always taken into account when choosing which kind of mill to utilize for a given size-reduction task. Impact, pressure, and friction work best for pulverizing hard, brittle materials, whereas cutting and shearing effects are good for comminuting soft, elastic materials. Size reduction is a crucial step in sample preparation for many applications [1]. Ball milling is a grinding method that grinds or blends materials. During the ball milling process, the collision between the rigid balls in a concealed container will generate localized high pressure [2]. Experimental Procedure Part 1. Milling Aluminum Oxide. 1. Dry metal pot and balls are prepared. 97 balls are taken and 180 ml bulk volume of balls is determined using a plastic measuring cylinder. 2. 45 g of Aluminum Oxide is measured using a scale. 3. Metal balls are placed in a jar and shaken to mix. After that, the material is inserted and the lid of the jar is closed. It is shaken again to make sure that the powder does not spill out. 4. The jar is fixed on rollers and the Roll Mill is launched. 5. The machine is turned on with the switch, and then the speed is adjusted in the range of 200 rpm. 6. The start button is pressed and the exact time is set at 15, 30, and 45 minutes. 7. Four labeled tubes are prepared and the first tube is filled with initial material. 8. After pressing the "Stop" button and complete silence, the sample is taken with a dry spoon. The Mastersizer 3000 size analyzer is used to determine their size. This is completed for each time period recorded. Part 2. Measuring PSD of initial Aluminum Oxide. 1. The PC is turned on. 2. On the desktop of the PC, the “Mastersizer 3000” software is opened. 3. New SOP is created and Hydro MV is chosen. 4. The SAMPLE NAME is filled and the spherical particle type is chosen. 5. Material name is “Aluminum Oxide” and then the dispersant is chosen from the database. 6. Required measurements are inserted. 7. Sample Dispersion is clicked and Accessories is opened, and Manual mode is selected. 8. The save button is pressed, and the SOP filename is filled. 9. RUN SOP is pressed on the panel and SOP is chosen. 10. Start button is pressed after checking the laser power (should be higher than 70%). 11. After reaching the Measure sample step, Aluminum Oxide is added into the hydro MV unit. Results The particle size is measured using the Malvern Mastersizer 3000 laser diffraction, and the effects of relative frequency and corresponding particle sizes are determined. The graphs of particle size distribution are plotted in Excel and provided below. Frequency distribution plots for the initial sample as well as after 15, 30, and 45 minutes of milling are given in Fig. 1. The initial sample particles have larger sizes than those after milling. In Figures 2 and 3, Cumulative undersize and oversize particle distributions are provided at initial, after 15, 30, and 45 minutes of the milling time. Figure 1. Frequency distribution graph for all four samples of particles. Figure 2. Cumulative undersize distribution graph for all four samples of particles. Figure 3. Cumulative oversize distribution graph for all four samples of particles. In table 1, the mode and median sizes of particles at different time intervals of milling (0, 15, 30, and 45 minutes) are summarized. According to the results, the largest mode size is seen before milling, which is 71.45 μm. Even though the frequency distribution graph for 45 min milling is shifted to the left side of the graph for 30 min, the peak for both is found to be the same. The median size decreases with increasing milling time, which means after each milling interval particles become smaller.
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