Aim: To synthesize Carbon Nanotubes (CNT) using Chemical Vapor Deposition (CVD) Method
- Reagents required: Toluene and FerTocene.
- Apparatus required: Weighing machine, beaker, CVD assembly, Quartz tube, 2 silicon cork, 2 silicon tubes, Argon gas cylinder, syringe, needle, syringe pump, cotton, foil, brush, gloves.
A carbon nanotube (CNT) is a tubular structure made of carbon atoms, having a diameter of nanometer order but length in micrometres. It has extraordinary properties such as it
is many-fold stronger than steel, harder than diamond, electrical conductivity higher than copper, thermal conductivity higher than diamond. Chemical vapour deposition (CVD) is the most popular method of producing CNTs nowadays. In this process, thermal decomposition of a hydrocarbon vapour is achieved in the presence of a metal catalyst. Hence, it is also known as thermal CVD or catalytic CVD.
CNT synthesis: The process involves passing a hydrocarbon vapour (typically 15-60 min)
through a tubular reactor in which a catalyst material is present at sufficiently high temperature (600-1200°C) to decompose the hydrocarbon. CNTs grow on the catalyst in the reactor, which is collected upon cooling the system to room temperature. Low-temperature CVD (600-900°C) yields MWCNTs, whereas high-temperature (900-1200°C) reaction favours SWCNT growth. An inert gas such as carrier gas is used to carry the vapours and deposit them on quartz tube’s surface near the region of 750°C.
- Switch on the CVD assembly and allow it to reach the temp. Of the first section to 350 degrees C and the second section to 750°C
- Take Toluene in a beaker and add Ferrocene to it till it reaches saturation.
- Make 2 holes in 1 cork (inlet) and 1 hole in outlet silicon cork.
- Maintain the pressure of Argon gas to 2L/hr. Argon gas act as a carrier gas.
- Put a silicon tube to the one hole of inlet silicon cork and attach other ends of it to the Argon gas cylinder.
- Put other silicon tubes in the hole of outlet cork and allow the gas to pass through the quartz tube.
- Now fill the syringe with the Toluene mixture and put it in other holes of inlet cork.
- Fix the syringe on the syringe pump and maintain the flow rate. Keep it around 10 15ml/hr.
- Press run on the syringe pump and mixture starts evaporating and deposit on quartz tube walls.
- Repeat steps 7 and 8 for a no. of times to get a significant amount of CNT.
- After completion of the above process allow the quartz tube to cool down to room temperature.
- With the help of brush scratch the CNT on a foil and collect it in a container.
Multiwalled CNTs of nanometer range are formed.
- Hold the quartz tube very carefully.
- Use gloves for scratching the CNT from the tube.
- Maintain Ar. Gas pressure with care.
- Avoid touching the tube or inner part of the assembly during the process as its temperature is very much high.
- Check the syringe continuously.
- Switch off the assembly and syringe pump on completion of the process and close the gas cylinder.