Microwave is advantageous for nanoparticle synthesis because nanostructured crystals and mono-dispersed nanoparticle size can be obtained due to the rapid growth induced by quick thermal response. In previous studies, it has been confirmed that an individual application of two-stage irradiation and anti-solvent addition is effective in promoting stable nucleation and smaller particle generation. Nevertheless, to date no studies have been reported in applying the two methods above simultaneously and examining their synergistic effect. This study, therefore, aims to investigate the possibility of producing finer particles using a stable operation without any superheating and abrupt bubble growth. From the experimental data, it is evident that the beneficial combined effect of two-stage irradiation and addition of anti-solvent on the stable finer nanoparticle formation could be observed and confirmed. It is expected that the findings and recommendations from this work may be useful in optimizing two-stage microwave-assisted nanoparticle synthesis with an addition of anti-solvent.

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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.

Microwave (MW)-assisted de-emulsification has been attractive in processes of petroleum production and refining. However, the mechanism and optimal operation remain poorly understood. In this study, the behaviour of decane-inwater emulsion under MW irradiation was monitored in-situ through a size measurement system equipped with the reactor and surface tension profiles.The results indicated that the bubble was formed around the oil droplet during MW irradiation. The MW-induced bubbles can enhance de-emulsification in a similar mechanism as the flotation column. The efficiency of MW de-emulsification depends on emulsion content and MW power. Although a higher MW power is more effective, boiling caused by excessive energy must be considered due to the higher local heating. As a result, moderate power is more desirable. For the decane-in-water emulsions in this study, the optimal condition was determined to be around 500 W.

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