Germanane (GeH), a hydrogen-terminated layered germanium structure, has recently been synthesized. Here, we employed a four-probe thermal transport measurement method to obtain the basal-plane thermal conductivity of thin exfoliated GeH flakes and correlated the measurement results with the crystal structure. The obtained thermal conductivity increases with increasing temperature, suggesting that extrinsic grain boundary and defect scattering dominate over intrinsic phonon-phonon scattering. Annealing a polycrystalline GeH sample at 195 °C caused it to become amorphous, reducing the room-temperature thermal conductivity from 0.53 ± 0.09 W m−1 K−1, which is close to the value calculated for 16 nm grain size, to 0.29 ± 0.05 W m−1 K−1, which approaches the calculated amorphous limit in the basal plane thermal conductivity.

A carbon nanotube (CNT) aerogel is a low-density network of small diameter single-walled CNTs held together by van del Waals forces. Due to the excellent mechanical, thermal, and electrical properties of individual CNTs and the potential to fuse the junctions in the aerogel, CNT aerogels are candidates for ultralight structural media, radiation detectors, thermal insulators, and electrical conductors. Using molecular dynamics (MD) simulation, we predict the thermal conductance of the junction formed between two CNTs. To access the range of conditions present in the aerogel, we test the effects of different boundary conditions, the CNT lengths, and the rotational angle of the CNTs. A 3-D network model of the aerogel is built that will be used with the MD predictions to estimate the aerogel thermal conductivity.

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