Dense and homogeneous multi-walled carbon nanotube/metal composites are prepared by powder metallurgy [1,2]. The distribution of the nano-reinforcements in the matrix is studied by scanning electron microscopy and Raman spectroscopy, and the mechanical properties of the composites are determined by means of static tensile tests and Vickers micro-hardness measurements. We show that a homogeneous dispersion of the nanotubes at the micron scale is required in order to improve the mechanical properties of the metal matrix composite [1]. This can be achieved using ball-milling through the mechanisms of plastic deformation and cold-welding. Accordingly, we report significant improvements to the mechanical properties of composites prepared with a high-performance aluminium alloy AA5083 matrix. From the evolution of the composite Young’s modulus and yield strength as a function of carbon nanotube concentration, we get an estimate of the nanotubes Young’s modulus and aspect ratio [2]. We compare the results for single-walled and multi-walled carbon nanotubes, and discuss how to optimise the mechanical properties of carbon nanotube-reinforced aluminium alloy composites. 1. J. Stein et al, Carbon 50 (2012) 2264-22722. J. Stein et al, to be published

nanotubes or graphene particles. On the other hand, the organization of nanocarbons as liquid crystals providesnew methodologies for the still challenging structural characterization of such materials.In this talk, we will present a review of our recent results in the preparation and characterization of lyotropicLC made from concentrated aqueous suspensions, stabilized by surfactants, of single-walled carbon nanotubes(SWNT) or reduced graphene oxide (RGO) [1-5]. Homogeneously oriented SWNT LC can be prepared by shearinga drop between two glass plates [1]. The order parameter of SWNT LC was found to be very sensitive to wavinessand entanglement of the nanotubes and the best orientational order was achieved after disentangling, shorteningand sorting the nanotubes using ultrasonication and ultracentrifugation [2]. Anisotropic conductive films ofnanotubes can be prepared by drying the LC. The anisotropy of conductivity of the anisotropic layers can be relatedto the order parameter through a simple analytical model assuming that the electrical resistance in a percolationpath is proportional to the number of contacts [3].Homogeneous orientation of RGO LC was achieved by centrifugating capillaries. Structural and thermodynamiccharacterizations provide statistical information on the dimensions of the graphene flakes, which are found to becomparable with those of neat graphene oxide flakes [4,5].[1] C. Zamora-Ledezma et al., Nano Lett. 8 (2008) 4103-4107 [2] N. Puech et al., J. Phys. Chem. C. 115 (2011) 3272-3278 [3] C. Zamora-Ledezma et al., Phys. Rev. E 85 (2012) 062701(5) [4] C. Zamora-Ledezma et al., J. Phys. Chem.Lett., 3 (2012) 2425-2430 [5] C. Zakri et al., Phil. Trans. R. Soc. A. 371 (2013) 201204995(15)

Most of the current SWNTs production today is used to process bulk composite materials and thin films for exploiting their intrinsic properties at the macroscopic scale. However, the poor control of their distribution and orientation lead to unorganized architectures and limited properties [1]. Besides mechanical properties, electrical and optical properties are the most widely studied. However, various kinds of photoluminescent (PL) nanotube-based composites can be prepared only when the tubes are well dispersed as individuals in the composites [2-4]. Indeed, contacts between nanotubes quench the PL intensity. On the other hand, contacts are required to obtain some electrically conductive materials.In this work we propose and compare different strategies to sort and control the number and nature of contacts in order to control both the PL and electrical (conductivity) properties of SWNTs-based composites [2-4]. These approaches include the control of the quantity of SWNTs, the quantity and nature of the dispersing agents used to disperse them, and their orientational order. We especially work on thin films and thin layers of polymer composites, as well as inorganic gels. Different optical spectroscopy techniques, i.e. absorption, Raman and photoluminescence spectroscopies, are used to study the dispersion and orientation of the nanotubes [2-4]. Electrical measurements are achieved using two and four point probes.[1] Michael F. L. De Volder et al. Science 339, (2013) 535[2] C. Zamora-Ledezma et al, J. Phys. Chem. C, 116 (25), (2012) 13760[3] C. Zamora-Ledezma et al, Phys. Rev. E 84, (2011) 062701[4] C. Zamora-Ledezma et al, Carbon 46, (2008) 1253-1269

NEMATIC LIQUID CRYSTALS OF CARBON NANOTUBES AND GRAPHENE