Analysis of carbon nanomaterial "Taunit" and composite materials on its basis

I.K.Nasyrov, Yu.N.Osin, D.N.Valeeva, Z.Y.Khalitov

Kazan State Technical University of A.N. Tupolev's name, Kazan, Russia

 

Object of research were samples of carbon nanomaterial "Taunit" (CNM).

Research of the object in scanning electron microscope has shown, that it practically completely represents entangled-fibrous globular formations from tubular nanoparticles, having rather homogeneous form. The insignificant presence of extraneous amorphous (by morphology) phases is observed.

The atomic-absorption analysis of samples has shown presence of Ni about 1 %. The X-ray spectroscopy microprobe analysis in scanning electron microscope has shown that Ni is located in the central areas of globular particles of CNM. In the same area the traces of presence of Al also are found out. It is obvious, that these impurities are relict of process of synthesis and by globular formations from the catalyst in an initial phase of their growth.

Were carried out, also, the microprobe chemical analyses of separate nanotubes, where the technogenegical impurities are observed too. Their most probable localization - internal cavities of nanotubes, and also the free bonds of carbon atoms at the edges of graphen layers.

Research of samples in projection electron microscope has shown presence in CNM nanotubes of two types: with the disordered-spiral form and rather rectilinear.

A prevailing type, forming the basic entangled-fibrous massif of a material, is nanotubes with the spiral form. The analysis of the electron-microscopic images of fragments of these nanotubes has shown, that these nanotubes have also spirally-cone internal structure.

Splitting of reflexes 00l on the microdiffraction pattern of single nanotube has confirmed its cone character. Four most intensive reflexes of a microdiffraction pattern with interlayer space d = 0,35 nm are reflexes 001 in three-value indexing, arising owing to scattering by packing of the cylindrically љbent pseudo-planes of graphen layers. In a case not cone nanotubes two reflexes 00l are observed, located symmetrically concerning a nanotube's axis on a straight line, which is taking place through an origin of reciprocal space. In this case each of these reflexes was split on a pair љowing to turn of pickings of graphen layers "on a cone".

The analysis of the X-ray patterns of CNM has established, that spiral nanotubes, forming the basic massif of a material, belong to a type "zigzag". This type of carbon nanotubes in comparison with types "armchair" and "chiral" should have rather less perfect structure and, thereof, - large elasticity and smaller strength. Thus, the raised љelasticity of a basic nanotubular phase of the investigated objects is a consequence of three factors: a structural type "zigzag", spiral-cone packing of layers in nanotube and spiral character of its external form.

The amorphous phase is shown on diffractogram of a sample as diffuse background of an appreciable level of intensity. In view of results of electron-microscopic research it is possible to make a conclusion, that this phase is more probable is amorphous carbon.

The analysis of the high resolution electron-microscopic images and microdiffraction patterns of rectilinear nanotubes from CNM samples, performed earlier, shows that such nanotubes belong to circular structural model. These nanotubes have the rather perfect structure "armchair" and can form strong monocrystals of significant length.

Agrees by the microdiffraction data, in structure of CNM on an external surface of nanotubes "armchair" takes place a phase, consisting from fragments of graphen layers and having the high density of free carbon bonds. It proves to be true by scanning electron microscope pictures of break surfaces of polyamide samples, modified by nanotubes, where the examples of armoring of polymer by long "armchair" nanotubes are shown.

The carried out researches allow formulating the following conclusions.

The carbon nanostructural material "Taunit" is rather perspective for use in composite materials, as consists of nanotubes of two types.

The first type - spiral-like nanotubes "zigzag" because of there cone structure have on the surface the edge of a graphen layer with high density of bonds, that allows them, after dispersing, effectively to bond structural elements of a matrix, for example, molecules of polymer, on the nanoscale distances. The elasticity, inhering nanotubes of such type, provides belonging of this property to a final composite material.

The second type - long and strong nanotubes "armchair" represent itself as armoring elements on distances about shares of micron as, on the one hand, their basis are the rather large and perfect cylindrical crystals, and, with another, the superficial phase with high density of free carbon bonds also provides effective bonding with a matrix.