Multi-parametric study of heterogeneous kinetics and burn rate regime transitions in carbohydrate-KNO3 solid energetic mixtures

This study presents a parametric investigation into the physical, thermodynamic, and localized linear reaction kinetics of KNO 3 and carbohydrate-based renewable solid propellant formulations evaluated as sustainable alternatives to traditional pyrotechnic compositions. Five distinct fuel-oxidizer matrices, including Sorbitol, Sucrose, Dextrose, a 50/50 Sucrose-Sorbitol blend, and a classic black powder benchmark, were evaluated across twenty-five formulation variations to isolate the coupled effects of condensed-phase molecular structure, oxidizer particle size distributions, moisture-induced thermal sinks, and heterogeneous transition metal oxide catalysts (Fe 2 O 3 ) paired with reactive carbon additives. Structural packing characterization showed that sucrose-based matrices achieved peak packing efficiency, yielding a minimum baseline porosity of 4.73% and a relative density of 0.953. Linear burn rate testing conducted at 0.1 MPa demonstrated that shifting from fine ( 45 to 75 μ m ) to coarse ( > 250 μ m ) oxidizer fractions significantly depressed linear burn rates ( r b ) , while an average moisture uptake of ∼ 2.23 wt % introduced significant endothermic phase-change sinks that degraded r b by up to 46% in highly hygroscopic matrices. Pearson correlation tracking across grouped datasets reveals an exploratory statistical shift in the underlying combustion mechanisms: baseline carbohydrate formulations are heavily governed by a morphologically influenced regime dictated by bulk porosity and molecular complexity, whereas the incorporation of transition metal oxides (Fe 2 O 3 ) and reactive carbon black, transitions the flame front into a thermochemically dominated propagation regime heavily dictated by the adiabatic flame temperature ( R = + 0.933 ). Under optimized catalytic conditions, the sucrose-based matrix achieved a peak burn rate of 9.85 mm / s , fundamentally outperforming the metallized pyrotechnic benchmark ( 8 . 50 mm / s ). These findings provide a unified empirical framework explaining how physical inter-particle transport barriers interact with gas-phase thermochemical kinetics to dictate solid-phase deflagration behavior.