arXiv subjects

J. Bernardi

Publications and source records attributed to J. Bernardi.

4 recordsLinked to original sources

arXiv2019

Nanostructured clathrates and clathrate-based nanocomposites

Intermetallic clathrates are candidate materials for thermoelectric applications above room temperature. Here we explore whether their intrinsically low lattice thermal conductivities can be further reduced by nanostructuring and whether this can further enhance their thermoelectric performance.}{As bulk nanostructuring routes we studied melt spinning and ball milling. To optimize the compaction process and/or stabilize the nanostructure we varied the process parameters, used additives, and studied clathrate-based composites. Initial results on clathate nanowires as simpler model nanostructures are also presented.

cond-mat.mtrl-sci↗

arXiv2016

Assessing composition gradients in multifilamentary superconductors by means of magnetometry methods

We present two magnetometry-based methods suitable for assessing gradients in the critical temperature and hence the composition of multifilamentary superconductors: AC magnetometry and Scanning Hall Probe Microscopy. The novelty of the former technique lies in the iterative evaluation procedure we developed, whereas the strength of the latter is the direct visualization of the temperature dependent penetration of a magnetic field into the superconductor. Using the example of a PIT Nb3Sn wire, we demonstrate the application of these techniques, and compare the respective results to each other and to EDX measurements of the Sn distribution within the sub-elements of the wire.

cond-mat.supr-con↗

arXiv2006

Encapsulating C59N azafullerene derivatives inside single-wall carbon nanotubes

Filling of single-wall carbon nanotubes with C59N azafullerene derivatives is reported from toluene solvent at ambient temperature. The filling is characterized by high resolution transmission electron microscopy and Raman spectroscopy. The filling efficiency is the same as for C60 fullerenes and the tube-azafullerene interaction is similar to the tube-C60 interaction. Vacuum annealing of the encapsulated azafullerene results in the growth of inner tubes, however no spectroscopic signature of nitrogen built in the inner walls is detected.

cond-mat.mtrl-sci↗

arXiv2003

Low temperature fullerene encapsulation in single wall carbon nanotubes: synthesis of N@C$_{60}$@SWCNT

High filling of single wall carbon nanotubes (SWCNT) with C$_{60}$ and C$_{70}$ fullerenes in solvent is reported at temperatures as low as 69 $^{o}$C. A 2 hour long refluxing in n-hexane of the mixture of the fullerene and SWCNT results in a high yield of C$_{60}$,C$_{70}$@SWCNT, fullerene peapod, material. The peapod filling is characterized by TEM, Raman and electron energy loss spectroscopy and X-ray scattering. We applied the method to synthesize the temperature sensitive (N@C$_{60}$:C$_{60}$)@SWCNT as proved by electron spin resonance spectroscopy. The solvent prepared peapod samples can be transformed to double walled nanotubes enabling a high yield and industrially scalable production of DWCNT.

cond-mat.mtrl-sci↗