PAAD experiments were run in consistent campaigns with one fixed set of input parameters per sample; aside the seven features used for subsequent model input, all other processing conditions were kept constant. Roughly 10 g of powder material were sampled for each run. As a trade of between experiment cost and overall dataset size, 51 individual PAAD campaigns (each running approximately one day) were finally included in the analysis. According to the XRD results, the as-received heteroaggregates consisted of four phases: δ-Al2O3 (JCPDS no. 98-002-3782), θ-Al2O3 (JCPDS no. 98-002-7283), α-Al2O3 (JCPDS no. 98-002-2959) and an amorphous fraction (denoted a-Al2O3, whereby no further distinction was made for the potential presence of multiple different amorphous phases). In particular, XRD did not reveal any residual nitrate or boehmite phases (nor the first decomposition product of boehmite, γ-Al2O3), further confirmed by simple elution and pH testing (see Figure . Furthermore, the presence of melt-quenched glassy alumina was excluded from the amorphous fraction in view of thermal considerations and reference experiments (see Figure ). The three crystalline phases represent the thermal evolution of boehmite , where the thermal stability window of δ-Al2O3 was reported at 750-950 o C ; α-Al2O3 has the most ordered structure up to its melting point of 2072 o C. The main crystalline phase was always δ-Al2O3, with a volume fraction of 60-90% relative to the overall crystallinity. The phase composition of all sample powders is summarized in Table .