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This study presents a controlled, side-by-side comparison of three widely used forming methods—uniaxial pressing (UP), isostatic pressing (IP), and gel casting (GC)—for fabricating porous alumina ceramics, using identical powder, milling conditions, and sintering schedules to isolate the inherent influence of each method on microstructure and performance. Alumina powders milled for 8 h and 12 h were consolidated through UP, IP, and GC, followed by sintering at 1430–1460 °C. Comprehensive characterization—including Archimedes porosity, SEM-based pore size analysis, Weibull strength statistics, and Darcy permeability—was conducted to establish a processing–structure–property map relevant to filtration, structural, and membrane applications. The results show that IP produces the highest and most uniform densification (relative density up to 85.3%) with the smallest mean pore size (0.22 μm), yielding the highest characteristic strength (186 MPa). UP provides intermediate densification and strength due to compaction gradients inherent to die-wall friction. In contrast, GC generates the highest interconnected open porosity (10.7–16.0%) and the greatest permeability (up to 0.004744 Darcy), making it ideal for fluid transport applications. Extended milling (12 h) significantly reduces pore size and improves reliability across all methods, while sintering at 1460 °C enhances densification without removing the fundamental differences imposed by forming method. Overall, the study reveals how forming-route-dependent green density, pore architecture, and defect population govern the final performance of porous alumina ceramics. The resulting comparative dataset provides new insight into selecting fabrication routes based on desired mechanical, microstructural, or permeability targets and establishes a foundation for further optimization of porous ceramic processing.
Paydar et al. (Thu,) studied this question.