**1.4. The routes for synthesis of carbon nanomaterials**

There are several methods employed to obtain carbon nanomaterials. They are described very well by Tomanek in [14].

The nanotubes synthesis involve high energetic or temperature processes such as: arc evaporation (AE), chemical vapor deposition (CVD), conversion of carbon monoxide at high pressure in HiPCO process, ball milling (BM), as well as, the pulsed laser vaporization (PLV).

Arc discharge or arc evaporation (AE) can be used successfully for fullerenes, multi-wall carbon nanotubes and single-wall carbon nanotubes synthesis. Direct current of 10-20V is supplied to electrodes in a cooling inert gas environment. Nanotubes are formed on cathode during electrode evaporation in the direction of electric field lines. On the other hand fullerenes are founded in the soot on chamber walls. For syntheses of single-wall nanotubes the presence of catalyst into electrodes is required [2, 15].

The chemical vapor deposition (CVD) is a very common process for covert hydrocarbons gases into a diamond-like carbon (DLC) coating or carbon nanotubes. Conversion takes place at high temperature in thermal CVD, or can be assisted by plasma in plasma-enhanced CVD (PE-CVD). In the presence of water and by using a substrate (usually silicon) vertically aligned nanotube arrays (VANTAs) can be obtained by CVD. This process is called "Supergrowth".

A low-cost synthesis technique for nanotubes and related nanostructures from layered substances, such as graphite is the ball milling (BM). The BM is performed at room temperature, but the impact of a macroscopic ball on a powdered substance leads locally to a temperature increase that enables rearrangement of chemical bonds. Changes are induced in chemical bonding and structure by pressure, often introduced by hitting the material with a foreign object.

Pulsed laser vaporization (PLV) or laser ablation is a technique to produce high-quality carbon nanostructures. A laser beam is focused on a heated carbon target. The resulting plume and vapors are carried by an inert gas to a cooled cooper collector called cold finger (CF), where the raw material condenses. A sea urchin, also known as a dahlia structure, is a colloquial designation for the compact agglomeration of carbon nano-horns formed during the laser ablation process.

PLV or PLD (pulsed laser deposition) is the technique that will be in great detail described below along the results of the synthesis obtained using this method.
