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In this paper there were studied the structure of multilayer carbon nanotubes by methods of X-ray diffraction and elector microscopy. Test samples were prepared by reacting the porous polycrystalline graphite, heated to 800, 850 or 900°C with distilled water at room temperature. As a result of X-ray analysis of the carbon residue obtained after evaporation of distilled water was found a slight decrease in the interlayer distance d 002 and increase in the average size of coherent scattering regions along the crystallographic c axis of graphite, compared with the same characteristics of the original graphite. This is indicates a small amount of formed carbon nanostructures in the samples at the hydrothermal synthesis. Electron microscopic studies have shown that the samples consist mainly of crystals of the original polycrystalline graphite, which contains on the surface of the tubular scrolled nanostructures. Probably tubular nanostructures was formed by the reaction heated to a high temperature of graphite with distilled water. The model calculations were made by the method of molecular mechanics MM+ and show that the folding of graphene layers in the rolls may occur as a result of the functionalization of graphene layers by not carbon atoms. It is revealed that graphene layers form the structure of scrolled carbon nanotubes as a result of junction hydrogen atoms and/or hydroxyl groups to the graphene layers. As a result it is revealed that the amount of the tubular nanostructures obtained by hydrothermal synthesis is less than 1 ÷ 2% of the initial amount of graphite.

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