The proposed technology of carbon nanotubes manufacturing consists in performing the disproportionation Boudouard reaction (1)
CO(v) + CO(w) -> CO2 + C (1)
Ev + Ew >= 5.5 eV
of vibrationally excited molecules of carbon oxide CO (v) under greatly no equilibrium conditions at relatively low temperatures of some 500 degrees Celsius and at atmospheric pressure. To create such a no equilibrium conditions the Atmospheric Pressure High
Voltage Discharge (APHVD) is proposed.
The initial hydrocarbons/air mixture (synthesis gas, methane/air) is converted under APHVD conditions to the mixture of CO, H2, N2 and some other chemicals. Hydrogen plays an important role in carbon nanotubes synthesis, reducing synthesis by-products (carbon particles of graphite phase) to form methane and a small amount of iron evaporated from the cathode catalyses reaction (1). Below shows specimens of carbon nanotubes synthesized in APHVD.
Micro photos of carbon nanotubes and nanofibers with diameter 70-150 nm synthesized in Prototype of plasma reactor is below.
Stage of Pre-Design
Experimental demonstrated plasma reactor Experimental plasma reactor is capable of producing carbon product – Multi-Wall Carbon Nanotubes and Carbon Nanofiber with diameter 70-150 nm, at a rate of 100-200 g/h.
Uniqueness of these carbon nanomaterials lies in the fact that, even in small amounts (hundredth of a percent), they can considerably change physical and chemical properties of the materials and substances (e.g. strength, flexibility, endurance, aging resistance, in flammability threshold, adhesion, etc.).
Plasma-Chemical Reactor for the purification of semiconductor materials
Stage of R&D
In nowadays conversion of solar energy into electricity with solar cells and production of low-cost raw material for solar panels is the subject of the special interest. Plasma-arc technology is one of the methods, which has proven its effectiveness for removing acceptor group impurities from silicon.
The new design allows to receive using plasma treatment of up to 1.5 kg silicon per hour by using argon, water vapor, oxygen and other gases in predetermined proportions.
Particular attention paid to elimination of re-contamination silicon sources from the components of the plasma torch, gas supply system and the crucible. Tungsten cathode is used for plasma generation torches, which provide much less susceptible to erosion from plasma arc up to power of 40 KVA. Chemical contaminants in the raw material and in the purified silicon are controlled by means of ICP AES. Appropriate sample preparation allows measuring elements that contributed to the conductivity, as well as the lifetime of charge carriers in the concentration range from a few ppb.
The experiment demonstrated silicon plasma treatment effectiveness. The resistivity of the material has been increased from 0.1 to 8-10 ohm/cm. By controlling other impurities it is possible to select proper operational mode of reactor with minimum contamination. Prototype of plasma reactor is below.
1. Plasma arc torch; 2. Screen cooled by water; 3. Plasma jet; 4. Isolator; 5. Case; 6. Water-cooled shirt; 7. Plasma chamber; 8. Fuse; 9. Graphite electrode; 10. Ceramic support.