Extended Data Fig. 8: Quantitative microculture analyses assessing the role of heating rate.
a, To account for potential inhomogeneity of porosity distribution, we examined the microstructure at different positions through thickness. Here the quantity \((d\,/{d}_{0})\in (0,\,0.5)\) is introduced to enable systematic comparisons amongst different samples: \(d\) denotes the relative distance to the outer surface and \({d}_{0}\) the total thickness (close to 1.5 mm for all samples). SE images in a exemplify the microstructures of the specimen synthesized using 20 °C/min heating rate. b, Evolution trends of porosity and residual FeOx oxides under three different heating rates corresponding to the results in Extended Data Fig. 3. Despite the subtle gradient in the thickness direction, the increase in heating rate systematically elevates the residual FeOx content (incomplete reduction) and reduces the porosity (more eminent densification).
