Bubble formation around nucleated particle is inevitable when quick heating of microwave is employed in nanoparticle synthesis. Since these bubbles may cause bumping behavior, the bubble growth must be possibly suppressed to ensure stable microwave‐assisted operation. In this study, sequential and simultaneous ultrasound treatment and microwave irradiations on nanoparticle synthesis are proposed and investigated to assess the benefit of ultrasound in preventing superheating behavior and producing finer particles. Experimental results indicate that the inclusions of ultrasound treatment result in finer particle sizes and suppression of bumping behavior. Particularly, consecutive ultrasound treatment and microwave irradiation are recommendable due to its practicality and generating smallest bubbles and final particle sizes. This technique can therefore be expected as an innovative way to enhance industrial applications of quick thermal response induced by microwave.

Past studies report that nucleation promotion is induced by quick heating of microwave in nanoparticle synthesis. However, how the nucleation promotion quantitatively affects particle number density is still unclear. In this study, the number density is predicted using bubble size profiles measured under microwave irradiation. This idea is based on a finding that the maximum bubble size during the irradiation is closely related to the particle number density due to homogeneous distribution of microwave absorbance energy to the particles. The results indicate that when solute concentration or anti‐solvent concentration is higher, the particle number density also increases due to the nucleation promotion caused by microwave quick heating. This new approach can be expected as an innovative and rapid method for quantitative estimation of particle number density in microwave‐assisted nanoparticle manufacture.

To promote nucleation in nanoparticle synthesis, high-power operation is desirable. However, at high power, heat generation due to the rapid microwave absorbance of particles often results in rapid bubble growth, unstable nucleation, and superheating. Therefore, a trade-o between suppressing superheating and producing stable and ner nanoparticles is necessary. This study aims to investigate and con rm the synergistic e ect between the high power of microwaves and addition of different types of antisolvents. Results show that the addition of an antisolvent prevents superheating and produces ne-sized particles at high-power operation. In addition, it was observed that glycerin is a better antisolvent than ethylene glycol.