Bubble Mediated Spray-Antisolvent Crystallization Method for Preparation and Control of Ammonium Dihydrogen Phosphate Ultrafine Powder

The preparation of ultrafine particles with their high surface area and enhanced reactivity potential has garnered significant interest. Here, we propose a novel bubble mediated spray-antisolvent crystallization method for producing ultrafine particles of ammonium dihydrogen phosphate, an important precursor for fire extinguishing agents. In this method, micrometer-sized droplets were transported by carrier gas into the body of the antisolvent. By adjusting temperature, concentration, and gas flow rate, uniform square-shaped ultrafine particles ranging from 1 to 4 μm and 8–10 μm hollow spherical crystals with embedded block-shaped particles are obtained. This method achieves smaller particle sizes compared to antisolvent precipitation and greater energy efficiency than spray drying technology due to crystallization in the solution phase. For systems containing mixed rod-shaped particles, a reduction in particle size and distribution can be achieved with only slight grinding. This work demonstrates a new approach for producing ultrafine particles through bubble mediated spray-antisolvent crystallization, providing insights for material design.