Scalable Synthesis of High-Density Ultrafine Spherical Silver Powders

Ultrafine spherical Ag powders with narrow particle size distribution, high tap density, and limited agglomeration are important conductive fillers for advanced photovoltaic paste formulation. Current liquid-phase reduction scale-up is limited by uncontrolled nucleation, secondary agglomeration, and precursor passivation. This study investigates a process-integrated synthesis chain from precursor preparation to pilot-scale powder production from precursor preparation to kilogram-scale production. A flow-field-enhanced dissolution process (70-80 °C, 30-40% HNO₃) alleviates silver ingot passivation, while a multi-stage NaOH spray system reduces NO_x emissions to 186 mg/m³, meeting GB31573-2015 standards. Ascorbic acid kinetically decouples nucleation and growth per the LaMer model. Molecular dynamics simulations and RDF analysis reveal a synergistic dispersion mechanism involving PVP and gum arabic. A purpose-built 20 L pilot reactor with optimized fluid dynamics and high-pressure cleaning eliminates supersaturation heterogeneity. Subsequent ethanol displacement and supersonic jet milling yield 1 kg-scale powder with D50 = 1.90 µm, tap density = 6.0 g/mL, specific surface area = 0.6 m²/g, and LOI (538 °C) = 0.98%. The obtained powder shows powder-level characteristics relevant to subsequent photovoltaic paste formulation, rather than direct device-level validation.