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CNT FLAME SYNTHESIS - Coggle Diagram

- - - - Fuel is crucial for inception and growth of CNT and affects the flame temperature
        
        Fuel with minimal pyrolysis is preferred to delay (PAH) formation and soot
        
        Unburnt C2 species and presence of PAH in flame affect yield and morphology of CNT
    - - Most studies focused on obtaining optimal gas phase composition , suitable temp is obtained by probing the location with a suitable temp in flame vicinity
        
        Composition is controlled with equivalence ratio and stoichiometric mixture fraction
        
        Equivalence ratio affects the post-flame gas composition which impacts CNT morphology and yield
      - CO and H2 play an important role in CNT formation CO concentration has to be kept below the soot formation
        limit.
    - - Premixed
      - Diffusion
        
        Co-flow
        
        Inverse
        
        CNT growth region is outside reacting zone (CNT wont be exposed to high temp at flame front and no thermal defects)
        
        Counter-flow
        
        1-D simple flame geometry enables accurate development of flame model
    - - Cant be controlled independently but can be manipulated by
        
        change sampling location for a diff temperature
        
        Increase concentration of fuel/oxidizer/diluent concentration
      - Wen et al suggested that temperature is
        one of the controlling parameters of SWNT yields.
        
        increase in SWNT yield is observed as the temperature decreased at increasing HAB
      - Contradicting reports in the literature on the effect of temperature on CNT diameter
    - - Dilute flame or oxidizer is proven to produce optimum flame
      - a study by Yuan et al. found that nitrogen dilution helps to increase MWNTs formation with increased diameter uniformity nd reduce carbon fibers formation
        
        uniform diameter is caused by reduction of reaction rate when flame temp is reduce by addition of diluent inert gas
      - experiment by wander et al
        
        SWNT are only synthesized with an addition of an inert gas into flame
        
        excess concentration of inert gas reduces the CNT yield due to the decrease of reactant concentration