A Generalized Vaporization-Nucleation-Growth-Coating (VNGC) Process Model for Atmospheric-Pressure Microwave-Plasma Nanoparticle Synthesis

Atmospheric-pressure microwave plasma synthesizes silicon nanoparticles, graphene, and graphene-coated silicon within milliseconds in a single electrode-free reactor, yet existing process models treat one precursor in one stage and cannot predict staged-residence or dual-precursor operation. We present a generalized vaporization-nucleation-growth-coating (VNGC) framework taking the reactor temperature field and carrier flow as inputs, switching each precursor between physical vaporization and chemical pyrolysis, and making stage count an explicit residence-time variable through an inter-stage hand-off. All inputs are measured or fixed by theory except a single disruption efficiency, calibrated on one measured stage-to-stage size change and held fixed thereafter, making the framework one-point-calibrated and semi-empirical. For carbon black, graphitization appears only once the stage count supplies enough cumulative thermal dose, <i>I</i>_2D/<i>I</i>_G rising from 0.32 to 0.51 between two and three stages. For micron-silicon, the mean diameter falls from 46.6 to 33.6 to 20.7 nm across one to three stages, all below the 150 nm lithiation-fracture limit; the net decrease is produced by the calibrated disruption term, coagulation alone acting to coarsen. For the graphene-coated core-shell, shell coverage follows an Arrhenius surface-deposition rate, rising with microwave power to about 0.9, while excess methane lowers it by forming free soot. Spanning one temperature-residence operating plane, the three cases establish the multi-stage reactor concept and the unified two-pathway framework as a scoped, semi-empirical design basis, validated at the trend level by predict-then-compare testing.