flow rates may be attributed to the lower quantity of decomposed
carbon atoms at the 25 sccm flow rate, which was not sufficient for
all of the Pd catalysts passing through the heating zones to react.
When the flow rate of C2H2 increased to 50 and 100 sccm, more Pd
catalysts could participate in the reaction with the abundant carbon
atoms, resulting in an increased growth rate. Because the limit of
our C2H2 controller in the TCVD systemwas 100 sccm, we could not
identify the optimal value of the C2H2 flow rate. However, we expected
the growth rate to increase with the C2H2 flow rate, according
to the exponential function.
The spray pyrolysis method has many advantages such as the
possibility of a catalyst support-free, continuous reaction, and
shorter heating or cooling time for the furnace [19e22]. We have
compared the yield of our method to those using similar techniques,
as shown Table 1. The “yield”, in compliance with the
commonly adopted definition in other works, should be calculated
from the following equation: