Fig. 3

Porous carbon materials from SLSed whey powders; (a) micrograph of a cross-section of a carbonised SLSed structure, in which the rounded particles of the fresh whey (Fig. 1a) and sintered whey powder (Fig. 2b) are still clearly visible, with no layering at all; (b) carbonisation (850 ºC, 1.5 h) preserves the original form of SLSed whey powder structures, but with a significant (23%) isotropic contraction; accordingly, all the distances in the porous carbon artifact test (Fig. 2c) are reduced in approx. 23%, as shown in the different micrographs, reaching an outstanding printing precision; (c) examples of porous carbon with complex 3D structures (two fusilli-like helicoids, a Ugrinsky wind turbine, the aluminothermic mould and a pitch-blade turbine), presented as a proof of concept; typical ranges of C, N and ash contents (wt%, dry basis) of the SLS whey-derived carbons, depending on the specific whey powder used and/or porous carbon modification (e.g., acid washing). Whey powder SLS conditions: same as those detailed in Fig. 2.