Carbon foams with a triplex pore structure by compression molding of molten sucrose-NaCl powder pastes

A compression molding process for the preparation of carbon foams with a triplex pore structure has been studied. The pastes with moldable consistency, prepared by hot-blending of sucrose-NaCl powder mixtures of NaCl to sucrose weight ratios in the range of 0.7-1.2, set into solid bodies due to the caramelization of molten sucrose during the hot pressing. The caramelization in presence of NaCl results in carbon-enriched polymeric structure due to the enhanced α-elimination reactions along with the OH condensation as evidenced from torque-time measurements, IR, TGA and elemental analysis. The pyrolysis of compression molded bodies, followed by NaCl removal and further heat treatment results in carbon foams with a hierarchical triplex pore structure. The shrinkage during carbonization (28.5-24.2 vol%) and density (0.26-0.33 g/cm3), compressive strength (2.84-8.37 MPa), Young's modulus (170-370 MPa) and thermal conductivity (0.348-0.257 W/m.K) of the carbon foams depend on the NaCl to sucrose weight ratio. The carbon foams have a high specific surface area of ∼400 m2/g and a combination of macropores (414-70 μm), microcells (2-12 μm) and micropore texture.

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