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 for synthesizing carbon nanotubes (CNT) 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;
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 substrates;
wherein the feed gas is pre-heated to the second temperature by mixing a process gas along with the feed gas, the process gas having a temperature exceeding that of the second temperature, and whereby mixing of the feed gas and process gas achieves the second temperature as it enters the growth chamber.
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 feed gas mixture into the growth chamber.
8. A method for synthesizing carbon nanotubes (CNT) comprising the steps of:
providing a growth chamber, the growth chamber being heated to a first temperature;
passing a substrate through the growth chamber;
providing a feed gas pre-heated to a second temperature; and
introducing into the growth chamber the pre-heated feed gas wherein the second temperature is selected to achieve a desired temperature profile within the growth chamber to allow for the formation of carbon nanotubes on the substrate;
wherein the feed gas is pre-heated to the second temperature by mixing a process gas along with the feed gas, the process gas having a temperature exceeding that of the second temperature, and whereby mixing of the feed gas and process gas achieves the second temperature as it enters the growth chamber.
9. The method of claim 8 wherein the second temperature is within about 40% of the first temperature.
10. The method of claim 8 , further comprising diffusing the pre-heated feed gas into the growth chamber.