Redox Route from Inorganic Precursor Li₂C₂ to Nanopatterned Carbon

Abstract

We present the synthesis route to carbon with hierarchical morphology on the nanoscale. The structures are generated using crystalline orthorhombic lithium carbide (LiC) as precursor with nanolamellar organization. Careful treatment by SnI oxidizes carbon at the fairly low temperature of 80 °C to the elemental state and keeps intact the initial crystallite shape, the internal lamellar texture of particles, and the lamellae stacking. The reaction product is amorphous but displays in the microstructure parallel band-like arrangements with diameters in the range of 200-500 nm. These bands exhibit internal fine structure made up by thin strips of about 60 nm width running inclined with respect to the long axis of the band. The stripes of neighboring columns sometimes meet and give rise to arrow-like arrangements in the microstructure. This is an alternative preparation method of nanostructured carbon from an inorganic precursor by a chemical redox route without applying physical methods such as ion implantation, printing, or ablation. The polymerization reaction of the triple bond of acetylide anions gives rise to a network of carbon sp species with statistically sized and distributed pores with diameters between 2 and 6 Å resembling zeolite structures. The pores show partially paracrystal-like ordering and may indicate the possible formation of carbon species derived from graphitic foams.

Extreme biomimetics: Preservation of molecular detail in centimeter-scale samples of biological meshes laid down by sponges

“…Because the largest lattice planes allowed C 60 amounts to 14.04 Å, we exclude this possibility and consider patterns corresponding to variants of graphitic foam. This kind of carbon may build up differently sized lattices depending on aromatic spacers (phenyl groups) between sp 3 blocks, giving rise to porous structures (28). The rectangle at the center is further enlarged in Fig.…”

Deciphering the Polymorphism of CaSi2: The Influence of Heat and Composition

“…Another remarkable finding is the transformation of 6R-CaSi 2 into 3R-CaSi 2 at low temperatures in ionic liquids (ILs) . This caught our attention, as our research project also aims to convert reactive Zintl phases in ionic liquids to metastable compounds (e.g., Zn 2 Si 5 ) or allotropes (e.g., Ge cF 136). − After a treatment of 6R-CaSi 2 in the IL DTAC/AlCl 3 , we also observed the conversion of 6R-CaSi 2 to well-crystalline 3R-CaSi 2 . The required temperature of no more than 80 °C seemed surprisingly low to us, and we decided to examine the transformation process of the CaSi 2 polytypes in greater detail.…”

Type‐II Clathrate Na24‐δGe136 from a Redox‐Preparation Route

“…In similar ways, other crystalline metastable allotropes of Si and Ge [24] without a thermodynamic existence field in the p-T diagrams, [25] as well as nanostructured and surface-stabilized forms of group-14 elements have been obtained. [18,[26][27][28][29] An intermetallic clathrate phase, which was discovered already within the early works by Hagenmuller et al, [2,30,31] is Na x Ge 136 . Its preparation, particularly with large Na concentration, has remained a challenge ever since, however.…”

“…In similar ways, other crystalline metastable allotropes of Si and Ge [24] without a thermodynamic existence field in the p ‐ T diagrams, [25] as well as nanostructured and surface‐stabilized forms of group‐14 elements have been obtained. [ 18 , 26 , 27 , 28 , 29 ]…”