Macroscopic rods from assembled colloidal particles of hydrothermally carbonized glucose and their use as templates for silicon carbide and tricopper silicide

Self-aggregated colloids can be used for the preparation of materials, and we studied long rod-like aggregates formed on the evaporation of water from dispersed particles of colloidal hydrochar. The monodispersed hydrochar particles (100–200 nm) were synthesized by the hydrothermal carbonization ofglucose and purified through dialysis. During the synthesis they formed colloidal dispersions which wereelectrostatically stable at intermediate to high pH and at low ion strengths. On the evaporation of water,macroscopically large rods formed from the dispersions at intermediate pH conditions. The rods formedat the solid-water interface orthogonally oriented with respect to the drying direction. Pyrolysis renderedthe rods highly porous without qualitatively affecting their shape. A Cu-Si alloy was reactively infiltratedinto the in-situ pyrolyzed hydrochars and composites of tricopper silicide (Cu3Si)-silicon carbide(SiC)/carbon formed. During this process, the Si atoms reacted with the C atoms, which in turned causedthe alloy to wet and further react with the carbon. The shape of the underlying carbon template wasmaintained during the reactions, and the formed composite preparation was subsequently calcined intoa Cu3Si-SiC-based replica of the rod-like assemblies of carbon-based colloidal particles. Transmission andscanning electron microscopy, and X-ray diffraction were used to study the shape, composition, andstructure of the formed solids. Further studies of materials prepared with reactive infiltration of alloysinto self-aggregated and carbon-based solids can be justified from a perspective of colloidal science, aswell as the explorative use of hydrochar prepared from real biomass, exploration of the compositionalspace in relation to the reactive infiltration, and applications of the materials in catalysis.