The effects of quantum interferences on the excitation dependence of the intensity of G modes have beeninvestigated on single-walled carbon nanotubes [Duque et al., Phys. Rev. Lett. 108, 117404 (2012)]. In this work,by combining optical absorption spectroscopy and Raman scattering on individual index identified double-walledcarbon nanotubes, we examine the experimental excitation dependence of the intensity of longitudinal opticaland transverse optical G modes of the constituent inner and outer single-walled carbon nanotubes. The observedstriking dependencies are understood in terms of quantum interference effects. Considering such effects, the excitation dependence of the different components of the G modes permits us to unambiguously assign each ofthem as originating from the longitudinal or transverse G modes of inner and outer tubes.

AlPO4-17, known as the oxide with the highest negative thermal expansion (NTE), was studied under high pressure by angle-dispersive X-ray diffraction (XRD), mid- and far-infrared (IR) spectroscopy. Upon increasing pressure, the closure of the (P–O–Al) angle destabilizes the porous AlPO4-17 structure, which drives the amorphization process. On the basis of the decrease in intensity of the XRD lines and broadening of the IR modes, the material was found to begin to amorphize near 1 GPa. XRD, mid- and far-IR analysis evidenced pressure-induced framework softening and complete irreversible amorphization near 2.5 GPa corresponding to the collapse of the pores. The bulk modulus and its first pressure derivative (B0 = 31.2(5) GPa and B′0 = −10.1(3)) at ambient temperature were determined by fitting a third order Birch–Murnaghan equation of state (EOS) to the pressure–volume data. The material is extremely compressible and exhibits an elastic instability. Anomalous (negative) values of B′0 are very rare and have been observed previously for cyanides and metal–organic frameworks. Such an instability appears to be characteristic of materials, which exhibit strong NTE behavior and indicates a link between NTE and anomalous compressibility behavior. Mid-IR, far-IR, nuclear magnetic resonance, and pair distribution function analysis of the new amorphous form allow an amorphization mechanism to be proposed corresponding to a collapse of the structure around its pores retaining the columns built up of cancrinite cages and hexagonal prisms, based on alternating AlO4 and PO4 tetrahedra. An increase in coordination number of 10% of the Al atoms was observed. The pressure-induced amorphization in the strong NTE material AlPO4-17 opens the door to the development of new technological applications as crystal–amorphous nanocomposites with zero or specifically selected thermal expansion coefficients.

The recycling process toward the elimination of varistor wastes into new electro-active silicon composites has been investigated. We studied the dependence of the E-J characteristics on the aggregate content in the polymer matrix. Formulations with 40 vol.% metal oxide varistor aggregates in the 100-200m range exhibit reliable nonlinear behavior with a switching voltage of 280 +/- 30V/mm. The breakdown voltage of the composite decreases as both filler's diameter and filler's volume fraction increases in the 550-220V/mm and 440-280V/mm range, respectively. This paves the way for the valorization of varistors based zinc oxide (ZnO) ceramics.

In situ and ex situ Raman measurements were used to study the dynamics of the populations of single-walled carbon nanotubes (SWCNTs) during their catalytic growth by chemical vapor deposition. Our study reveals that the nanotube diameter distribution strongly evolves during SWCNT growth but in dissimilar ways depending on the growth conditions. We notably show that high selectivity can be obtained using short or moderate growth times. High-resolution transmission electron microscopy observations support that Ostwald ripening is the key process driving these seemingly contradictory results by regulating the size distribution and lifetime of the active catalyst particles. Ostwald ripening appears as the main termination mechanism for the smallest diameter tubes, whereas carbon poisoning dominates for the largest ones. By unveiling the key concept of dynamic competition between nanotube growth and catalyst ripening, we show that time can be used as an active parameter to control the growth selectivity of carbon nanotubes and other 1D systems.

We show that the properties of thin conductive inkjet printed lines of single-walled carbon nanotubes (SWCNT) can be greatly tuned, using only a few deposition parameters. The morphology, anisotropy and electrical resistivity of single-stroke printed lines are studied as a function of ink concentration and drop density. An original method based on coupled profilometry-Raman measurements is developed to determine the height, mass, orientational order and density profiles of SWCNT across the printed lines with a micrometric lateral resolution. Height profiles can be tuned from 'rail tracks' (twin parallel lines) to layers of homogeneous thickness by controlling nanotube concentration and drop density. In all samples, the nanotubes are strongly oriented parallel to the line axis at the edges of the lines, and the orientational order decreases continuously towards the center of the lines. The resistivity of 'rail tracks' is significantly larger than that of homogeneous deposits, likely because of large amounts of electrical dead-ends.

Chalcogenide glasses and more importantly their glass-ceramics counterparts have been an interesting but very peculiar class of thermoelectric materials, with inherently low thermal conductivity (< 0.3 W/m.K). In this study, we report on the fabrication of glasses in the ternary system Cu-As-Te (Cu_xAs_55-xTe₄₅ [5 ≤ x ≤ 20], Cu₁₅As_85-yTe_y [45 ≤ y ≤ 70], and Cu₂₀As_80-yTe_y [45 ≤ y ≤ 65]) by melt-quenching and subsequent spark plasma sintering treatment. Their thermal and structural properties have been studied by differential scanning calorimetry and Raman spectroscopy, leading to give insights into the structural evolution of the glassy matrix. Coupling this information with the analysis of their electrical transport properties allowed us to deepen further our understanding of the compositional effect on their thermoelectric properties, and indirectly how the evolution of their electronic band structure is at play. Despite exhibiting low ZT values by themselves, Cu-As-Te glasses may still be interesting candidates for thermoelectricity through partial crystallization for which knowing the relationship between composition and properties remains essential.