Laser-induced CVD Process

Si2NH(CH3)6) precursor, a filter holder for powder collection, a rotary vacuum pump and a continuous-wave C02 laser. 

For this system the oven is installed below the reactor. Liquid hexamethyl disilyamine (HMDS, Si2NHMe2), with a boiling point of 125°C, is contained in a 

The reactant gaseous streams are irradiated by a continuous-wave C02 laser beam. The laser power is usually between 600 and 1500 W, and the laser beam in the left reaction zone is typically 10 to 11 mm in diameter, while the right one is 9 to 10 mm in diameter. The chemical reaction of the HMDS precursor results in a bright yellow flame. The powders are conducted into a filter holder for collection driven by the vacuum pump. 

By use of this functionally gradient coating the carbon-fibre-reinforced aluminium composites (C/Al) exhibit excellent mechanical properties. The ultimate tensile strength reaches 1250 MPa when the fibre volume fraction is 35%. 

The fibre yam is fed and collected by two spools which should have a large diameter to prevent damage to the coated fibres. After a fibre yam is drawn from the feeding spool it is uniformly spread by Teflon pulleys with the help of tension indicators. The movement of the fibre yam is driven by a motor connected with the collecting spool at the upper position. In order to minimise and eliminate oxygen contamination from the air the reactor and two spools are placed within an enclosure which can be evacuated. In the system the heating temperature can reach a maximum temperature of 2000°C and the pressure is evacuated to 0.05 to 0.1 Torr during the CVD process by vacuum pumps. 

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