Low temperature CNT growth using gas-preheat method
A method for synthesizing carbon nanotubes (CNT) comprises the steps of providing a growth chamber, the growth chamber being heated to a first temperature sufficiently high to facilitate a growth of carbon nanotubes; and passing a substrate through the growth chamber; and introducing a feed gas into the growth chamber pre-heated to a second temperature sufficient to dissociate at least some of the feed gas into at least free carbon radicals to thereby initiate formation of carbon nanotubes onto the substrate.
1. A method comprising the steps of:
providing a growth chamber, the growth chamber being heated to a first temperature sufficiently high to facilitate a growth of carbon nanotubes (CNTs);
passing a substrate through the growth chamber;
heating an inert gas to a temperature exceeding a second temperture; and
mixing a feed gas comprising a carbon with the heated inert gas to create a pre-heated mixture of the feed gas and the inert gas that has a temperature of at least the second temperature, wherein the second temperature is sufficient to dissociate at least some of the feed gas into free carbon radicals; and
introducing the pre-heated mixture of feed gas and inert gas into the growth chamber wherein the free carbon radicals initiate formation of CNTs on the substrate.
2. The method of claim 1 wherein the second temperature is higher than the first temperature.
3. The method of claim 1 , further comprising controlling the first temperature in a range of from about 450° C. to about 650° C.
4. The method of claim 1 , further comprising controlling the second temperature in a range of from about 550° C. to about 1000° C.
5. The method of claim 1 wherein the substrate is comprises at least one material selected from the group consisting of: a carbon fiber, a graphite fiber, a cellulosic fiber, a glass fiber, a metal fiber, a ceramic fiber, an aramid fiber, and any combination thereof.
6. The method of claim 1 wherein the substrate is coated with at least one material selected from the group consisting of: a catalyst, and a sizing.
7. The method of claim 1 , further comprising diffusing the pre-heated mixture of feed gas and inert gas into the growth chamber.
8. The method of claim 1 , wherein the second temperature is within about 40% of the first temperature.
9. The method of claim 1 , wherein:
the substrate comprises a substrate of spoolable dimensions;
the growth chamber comprises an inlet and an outlet; and
the step of passing a substrate through the growth chamber comprises the substrate of spoolable dimensions entering inlet and exiting the outlet continuously.
10. The method of claim 9 , wherein the growth chamber comprises an open-air, continuous-operation, flow-through reactor.