Carbon
structures, unlike metals or polymers, can hardly be directly
implemented in additive manufacturing, and their sustainable nature
is extremely limited. In this work, we demonstrate that porous carbon
structures can be obtained by laser stereolithography of acrylate–tannin
mixed resins, followed by a pyrolysis step. By adjustment of the initial
acrylate/tannin ratio in the resin, the density and volume shrinkage
of the resultant carbon, and consequently the mechanical properties
of the corresponding carbon-based architectures, could be modified.
The moderate electrical conductivity of the structures, reaching about
7 S cm–1, and their broad-band absorption in microwaves
open up possibilities for electrochemical or electromagnetic applications.
Thus, the possibility of obtaining complex freestanding structures
with imperceptible warpage, low volume shrinkage, and adjustable density
offers an opportunity to develop 3D-printed carbon materials with
a significant proportion of bio-based precursors, which can be easily
adapted for a large number of applications.
In this work, porous carbons were prepared by 3D printing formulations based on acrylate–tannin resins. As the properties of these carbons are highly dependent on the composition of the precursor, it is essential to understand this effect to optimise them for a given application. Thus, experimental design was applied, for the first time, to carbon 3D printing. Using a rationalised number of experiments suggested by a Scheffé mixture design, the experimental responses (the carbon yield, compressive strength, and Young’s modulus) were modelled and predicted as a function of the relative proportions of the three main resin ingredients (HDDA, PETA, and CN154CG). The results revealed that formulations containing a low proportion of HDDA and moderate amounts of PETA and CN154CG gave the best properties. Thereby, the optimised carbon structures had a compressive strength of over 5.2 MPa and a Young’s modulus of about 215 MPa. The reliability of the model was successfully validated through optimisation tests, proving the value of experimental design in developing customisable tannin-based porous carbons manufactured by stereolithography.
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