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| Preparation of acoustic microspheres by electrostatic breakup and freeze-drying |
| WANG Xiaoying, PEI Jingxian*, WANG Dongbao, WANG Junfeng |
| School of Energy and Power Engineering, Jiangsu University, Zhenjiang, Jiangsu 212013, China |
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Abstract For the preparation of acoustic microspheres by electrostatic breakup combined with freeze-drying technology, a high-speed digital camera technique was used to visualize the slurry breakup process. The image analysis technique was applied to study the influence of different working parameters on the particle size and sphericity of the microspheres. A theoretical model based on a Back Propagation(BP)neural network was established to analyze the importance of each working parameter. The results show that as the voltage increases, the slurry appears in dripping mode, micro-dripping mode, and oscillating micro-dripping mode. In the dripping mode, microspheres of millimeter size are formed; In the micro-dripping and oscillating micro-dripping modes, the microsphere particle size differs from the dripping mode by an order of magnitude, being 1/4-1/3 of the inner diameter of the ca-pillary tube. In the dripping mode, there is little difference in the size of the microspheres when the flow rate is increased, and in the micro-dripping and oscillating micro-dripping modes, the size of the microspheres gradually increases with increasing flow rate. The particle size of the microspheres prepared in each breakup mode has varying degrees of increase as the nozzle diameter increases. Due to evaporation, the particle size of the microspheres is slightly smaller than the droplet diameter, and when low voltages(0 and 2 kV)are applied, the increase in flow rate has an irregular effect on the particle size of the microspheres The receiving distance is the decisive factor affecting the sphericity of the microspheres. Increasing the receiving distance, which leads to a wider distribution of roundness and a decrease in the sphericity of the microspheres. The BP neural network analysis shows that the effect of voltage, nozzle diameter, and flow rate on the particle size of the microspheres accounted for 87%, 10%, and 3% respectively. Voltage is the determining factor for particle size of microspheres.
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Received: 13 February 2023
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