synthesis of carbon nanotubes, methods.pptx

synthesis of carbon nanotubes
methods
advantages
disadvantages
applications

1. SYNTHESIS OF CARBON NANOTUBES

2. Contents…… 2 What are carbon carbon nanotubes ? Classification of nanotubes. Sources of carbon Methods of synthesis of carbon nanotubes CVD Process Plasma enhanced CVD method Arc discharge method. Laser albation of metallic catalyst 5. Applications of carbon nanotubes.

3. 3 CNT can be described as a sheet of graphite rolled into a cylinder constructed by hexagonal rings of carbon . What are carbon nanotubes ?

4. CLASSIFICATION OF CNT 4

5. Sources of carbon 5 Typical organic /catalyst mixture xylene / ferrocene, toluene, benzene, mesitylene, xylene and n-hexane /ferrocene ethylene and ethanol / Fe, Co and Mo alloys. Typical carriers gases argon hydrogen

6. Properties of carbon nanotubes 6

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8. CHEMICAL VAPOUR DEPOSITION METHOD [CVD] 8 Source of Carbon atoms usually comes from an organic compound. Mixed with a metal catalyst and inert gas. Atomized and sprayed into reactor with temperatures ranging from 600 degree Celsius -1200 degree Celsius . Pyrolysis of organic compound deposits carbon [as soot] and CNT and reactor wall [usually a tube constructed from quartz.

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10. Advantages and disadvantages 10 Advantages thin film deposition  high-purity uniformity Scalability cost-effective Disadvantages high equipment and precursor gas costs potential hazards associated with precursor gases, high operating temperatures

11. Plasma enhanced CVD nanotube synthesis 11 Methane move toward the catalyst on the substrate. Heat of the reactor decomposes methane at the catalyst surfaces. Catalyst is at a slightly cooler temperature so carbon. is super saturated in a catalyst film so carbon precipitates out. Carbon forms nanotubes at the surface of the catalyst film.

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13. Advantages Low operating temperature Uniform coating of different shape Good step coverages High packing density -hard and environment stable Continuous variation of film characteristics of function of depth Stress reduction Disadvantage In stability against humidity and aging Existence of compressive of residual stress in the film Time consuming specially for super lattice structure Existence of toxic explosive gas e s in the plasma stream High cost equipment

14. . . 14 NANOTUBES SYNTHESIS BY ARC DISCHARGING IN A MAGNETIC FIELD In arc discharging method, graphite rods are used as electrodes. Electrodes are made of conducting materials. It has two high purity graphite electrodes as anode and cathode are held a short distance about 1-2mm. The anode is long rod of 6mm diameter, The cathode is short rod of 9mm diameter. Inert gas is meant for cooling of the sample.

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16. Current and voltage : DC power supply is given in the range of 50-100A and the discharge voltage is between 20-50V. A plasma is achieved by making a gas to conduct electricity by providing a potential differences across two electrodes. Arc evaporation technique involves evaporation of graphite anode rod and condensation of the deposit on the cathode rod under inert atmosphere Then it synthesis carbon nanotubes.

17. Applications Production of carbon nanotubes. Synthesis of nano metal oxides. Synthesis of nanowires e.g. Ag nanowires. Simple method of preparing graphene flakes.

18. CNT SYNTHESIS USING LASER ABLATION OF METALLIC CATALYST 18 In 1995 at rice university it was reported that synthesis of carbon nanotubes could be accomplished by vaporization Pulsed laser vaporize a graphite target in a high temperature reactor which has inert gas Nanotubes develop on the cooler surfaces on the reactor as the vaporized carbon condensed Water cooled surface may be included in the system to collect nanotubes The laser ablation method yield around 70%

19. . CNT SYNTHESIS USING LASER ABLATION OF METALLIC CATALYST 19 A well mixed acetylene air mixture is burned inside a tube furnace. A laser is used to vaporize a metal target [either Fe or Ni] The post flame exhaust gas is mixed with metallic vapour and allowed to cool. During cooling CNT are formed.

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21. Applications of carbon nanotubes 21 Enzymme immobilization Enzyme immobilization using CNTs improved the catalytic efficiency and stability even at higher pH, molar concentration, and temperature, which is further utilized for their potential applications (Li et al. 2018). Fuel cells The extraordinary high and reversible hydrogen adsorption in SWCNT materials has attracted much attention because of the possibility of using nanotubes as high-capacity hydrogen storage media (Gao et al. 1999) Drug delivery CNTs have also been utilized for drug delivery, wherein SWCNTs show lower accumulation as compared to the MWCNTs in the body. It efficiently delivers various drugs, peptides, DNA, etc. to the target sites (Bianco et al. 2005; Liu et al. 2009).

22. Effects of carbon nanotubes on plants 22

23. Limitations 23 Due to their small size carbon nanotubes are potential of causing more toxicity as compared to parent materials Not cost effective May affect human health and cause diseases like asthma, bronchitis and also lung cancer. Difficult to work with due to their small size Despite all the research scientists are still unable to understand how they work.

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