Method of growing ultra-long carbon nanotubes

Abstract

A method for growing ultra-long carbon nanotubes includes operating a chemical vapor deposition (CVD) system to grow a carbon nanotube, monitoring in real-time the behavior of the catalyst (e.g., catalytic particle) of the CVD system, and dynamically adjusting process conditions for operating the CVD system based on said monitoring to maintain the catalyst (e.g., catalytic particle) active for a longer period of time and grow ultra-long carbon nanotubes that can be used to make yarn that can be used to make ropes, fabrics or macroscopic wires with higher strength that can be used in structural applications.

Description

METHOD OF GROWING ULTRA-LONG CARBON NANOTUBESINCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

[0001] Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 CFR 1.57.BACKGROUNDField

[0002] The present disclosure is directed to carbon nanotubes (CNTs) and more particularly to a process for growing ultra-long carbon nanotubes.Description of the Related Art

[0003] Carbon nanotubes can be grown using a chemical vapor deposition process. However, length of carbon nanotubes is limited (usually a few microns) due to catalytic activity degrading over time until it ceases.SUMMARY

[0004] Accordingly, there is a need for an improved method of growing nanotubes to grow ultra-long carbon nanotubes (e.g., having a length of several millimeters, such as greater than 5 mm), such as to produce longer nanotubes to make yarn to make ropes, fabrics and macroscopic wires with higher strength that can be used in structural applications.

[0005] In accordance with one aspect of the disclosure, a method of growing ultralong carbon nanotubes includes the steps of: operating a chemical vapor deposition (CVD) system to grow a carbon nanotube, monitoring in real-time the behavior of the catalyst (e.g., catalytic particle) of the CVD system, and adjusting process conditions for operating the CVD system based on said monitoring to maintain the catalyst (e.g., catalytic particle) active for a longer period of time and grow ultra-long carbon nanotubes that can be used to make yarn that can be used to make ropes, fabrics or macroscopic wires with higher strength that can be used in structural applications. In one example, said monitoring is performed using Raman spectroscopy. In one example, said adjusting of process conditions is performed using an electronic controller (e.g., a PID controller, a neural network controller, etc.).

[0006] In some aspects, the techniques described herein relate to a method for growing ultra-long carbon nanotubes, including: operating a chemical vapor deposition (CVD)system to grow a carbon nanotube; monitoring with one or more sensors a real-time behavior of a catalyst of the CVD system; and dynamically adjusting with an electronic controller operating process conditions of the CVD system in real-time based on the monitored real-time behavior of the catalyst to increase an amount of time the catalyst is active to facilitate growth of the carbon nanotube.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a schematic view of a chemical vapor deposition system for growing carbon nanotubes.

[0008] Figure 2 shows carbon deposition on a catalytic particle to form a carbon nanotube.

[0009] Figure 3 shows a schematic diagram of a process for real-time monitoring of catalytic particle behavior to grow ultra-long carbon nanotubes.

[0010] Figure 4 is a schematic of Raman spectroscopy.

[0011] Figure 5 is a schematic of Raman spectroscopy data used in real-time monitoring of catalytic behavior to grow ultra-long carbon nanotubes.DETAILED DESCRIPTION

[0012] Figure 1 shows a schematic view of a chemical vapor deposition (CVD) system 100 for growing carbon nanotubes. The system 100 includes a furnace 102, a catalyst (e.g., nano catalytic particle) 104 inside the furnace 102. The furnace can operate at temperatures of 500 C to 1200 C and pressures of 760 Torr (101 kPa) to 7600 Torr (1013 kPa). The catalyst (e.g., nano catalytic particle) 104 can be made of metal. In one example, the catalyst (e.g. nano catalytic particle) 104 can be made of iron. A conduit (e.g., tube, pipe) 106 with an inlet 107 and outlet 108 extends through the furnace 102 and can flow a carbon carrying gas (e.g., methane, other carbon carrying gas) through the furnace 104. As the carbon carrying gas flows through the furnace 102 and reaches the catalyst (e.g., the catalytic particle) 104, pyrolysis occurs, releasing hydrogen and depositing carbon atoms on the catalyst (e.g., on the catalytic particle) 104, which arrange and grow as a nanotube.

[0013] Figure 2 shows amorphous carbon deposition on the catalyst (e.g., catalytic particle) 104 in increasing amounts from (a) to (b) to (c). However, catalytic activity of the catalyst (e.g., catalytic particle) 104 degrades over time (e.g., catalytic particle becomesclogged) and the growth of the carbon nanotube stops when the catalyst no longer works (e.g., when the metal is fully covered with carbon).

[0014] Figure 3 shows a method or process 200 for growing ultra long carbon nanotubes using a chemical vapor deposition (CVD) process, such as using a CVD system similar to the CVD system 100. The method 200 includes the steps of operating 202 the CVD system (e.g., a system similar to the CVD system) to grow a carbon nanotube, monitoring 204 (e.g., with one or more sensors, such as temperature sensors, pressure sensors, flowrate sensors, etc.) in real time the behavior of the catalyst (e.g., of the catalytic particle), and adjusting 206 process conditions of operation for the CVD system based on the monitored catalyst behavior. For example, one or more of operating temperature (of the furnace), operating pressure (of the furnace), flow rate (of the carbon carrying gas), and composition of gas flow can be adjusted (e.g., adjusted electronically with an electronic controller that controls, for example, the operation of the furnace to adjust temperature and pressure, flowrates of carbon carrying gas or steam, such as by electronically controlling actuation of valves in a CVD system). With respect to the composition of gas flow, the real-time monitoring identifies an amount of carbon in the carbon carrying gas. If the real-time monitoring identifies that the carbon carrying gas flow has too much carbon, steam can for example be added to the gas flow. If instead the realtime monitoring identifies that the carbon carrying gas flow has too little carbon, additional carbon carrying gas can be added to the gas flow. In this manner, the process conditions are dynamically adjusted (in real-time) based on the real-time monitoring and do not remain constant throughout the chemical vapor deposition (CVD) process. The process conditions can be varied using an electronic controller (e.g., a proportional-integral-derivative or PID controller, a neural network controller, etc.).

[0015] The real-time monitoring discussed above can be performed using a Raman spectrometer. Figure 4 shows a schematic view of a Raman spectroscopy process. A laser is shined on the catalyst (e.g. on the catalyst particle) 104, and the resulting scattered light is filtered to provide a Raman spectrum that can be used to characterize the catalyst particle. Figures 5 shows, for example, a graph of example Raman spectrums for Iron Oxide. Analysis of the resulting Raman spectrum can be used to identify catalytic behavior, for example, when varying temperature and gas pressure, and / or the phase of operation the catalyst is in. For example, with reference to Figure 5, the Raman spectroscopy method can identify the operatingconfiguration of the catalyst. If it is not in the preferred operating configuration (e.g., Hematite if that is the preferred configuration), process conditions at which the CVD process is operated are dynamically varied (e.g., electronically using the electronic controller) based on such analysis, as discussed above, to have the catalyst in the preferred operating configuration. Advantageously, said real-time (electronic) monitoring of catalytic particle behavior and (electronic) modification of process conditions for the CVD process allows for the catalyst (e.g., catalytic particle) to remain active for a longer period of time and grow ultra-long carbon nanotubes (e.g., having a length of several millimeters, such as greater than 5 mm) that can be used to make yarn that can be used to make ropes, fabrics or macroscopic wires with higher strength that can be used in structural applications.Additional Examples

[0016] In examples of the present invention, a method for growing ultra-long carbon nanotubes may be in accordance with any of the following clauses:

[0017] Clause 1. A method for growing ultra-long carbon nanotubes, comprising: operating a chemical vapor deposition (CVD) system to grow a carbon nanotube; monitoring with one or more sensors a real-time behavior of a catalyst of the CVD system; and dynamically adjusting with an electronic controller operating process conditions of the CVD system in real-time based on the monitored real-time behavior of the catalyst to increase an amount of time the catalyst is active to facilitate growth of the carbon nanotube.

[0018] Clause 2. The method of clause 1, wherein the carbon nanotube is an ultralong carbon nanotube having a length greater than 5 mm.

[0019] Clause 3. The method of any preceding clause, wherein the catalyst includes one or more catalytic particles.

[0020] Clause 4. The method of any preceding clause, wherein monitoring the realtime behavior of the catalyst includes using Raman spectroscopy of the catalyst to characterize the catalyst or identify catalytic behavior.

[0021] Clause 5. The method of any preceding clause, wherein monitoring the realtime behavior of the catalyst includes monitoring in real-time one or more of an operating temperature of a furnace of the CVD system, an operating pressure of the furnace, a flow rateof a carbon carrying gas flowing through the furnace, and a composition of the carbon carrying gas flowing through the furnace.

[0022] Clause 6. The method of clause 5, wherein monitoring the real-time composition of the carbon carrying gas includes monitoring an amount of carbon in the carbon carrying gas.

[0023] Clause 7. The method of clause 6, wherein adjusting operating process conditions of the CVD system includes adjusting in real-time one or more of an operating temperature of a furnace of the CVD system, an operating pressure of the furnace, a flow rate of a carbon carrying gas flowing through the furnace, and a composition of the carbon carrying gas flowing through the furnace.

[0024] Clause 8. The method of clause 7, wherein adjusting the real-time composition of the carbon carrying gas includes adding an amount of steam to the carbon carrying gas if an amount of carbon in the carbon carrying gas is higher than desired or adding an additional amount of carbon carrying gas if an amount of carbon is lower than desired.

[0025] Clause 9. The method of any of clauses 1-8, wherein the electronic controller is a proportional-integral-derivative (PID) controller.

[0026] Clause 10. The method of any of clauses 1-8, wherein the electronic controller is a neural network controller.

[0027] While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosure. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the systems and methods described herein may be made without departing from the spirit of the disclosure. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosure. Accordingly, the scope of the present inventions is defined only by reference to the appended claims.

[0028] Features, materials, characteristics, or groups described in conjunction with a particular aspect, embodiment, or example are to be understood to be applicable to any other aspect, embodiment or example described in this section or elsewhere in this specification unless incompatible therewith. All of the features disclosed in this specification (includingany accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. The protection is not restricted to the details of any foregoing embodiments. The protection extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0029] Furthermore, certain features that are described in this disclosure in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations, one or more features from a claimed combination can, in some cases, be excised from the combination, and the combination may be claimed as a subcombination or variation of a subcombination.

[0030] Moreover, while operations may be depicted in the drawings or described in the specification in a particular order, such operations need not be performed in the particular order shown or in sequential order, or that all operations be performed, to achieve desirable results. Other operations that are not depicted or described can be incorporated in the example methods and processes. For example, one or more additional operations can be performed before, after, simultaneously, or between any of the described operations. Further, the operations may be rearranged or reordered in other implementations. Those skilled in the art will appreciate that in some embodiments, the actual steps taken in the processes illustrated and / or disclosed may differ from those shown in the figures. Depending on the embodiment, certain of the steps described above may be removed, others may be added. Furthermore, the features and attributes of the specific embodiments disclosed above may be combined in different ways to form additional embodiments, all of which fall within the scope of the present disclosure. Also, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described components and systems can generally be integrated together in a single product or packaged into multiple products.

[0031] For purposes of this disclosure, certain aspects, advantages, and novel features are described herein. Not necessarily all such advantages may be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that the disclosure may be embodied or carried out in a manner that achieves one advantage or a group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.

[0032] Conditional language, such as “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements, and / or steps. Thus, such conditional language is not generally intended to imply that features, elements, and / or steps are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without user input or prompting, whether these features, elements, and / or steps are included or are to be performed in any particular embodiment.

[0033] Conjunctive language such as the phrase “at least one of X, Y, and Z,” unless specifically stated otherwise, is otherwise understood with the context as used in general to convey that an item, term, etc. may be either X, Y, or Z. Thus, such conjunctive language is not generally intended to imply that certain embodiments require the presence of at least one of X, at least one of Y, and at least one of Z.

[0034] Language of degree used herein, such as the terms “approximately,” “about,” “generally,” and “substantially” as used herein represent a value, amount, or characteristic close to the stated value, amount, or characteristic that still performs a desired function or achieves a desired result. For example, the terms “approximately”, “about”, “generally,” and “substantially” may refer to an amount that is within less than 10% of the stated amount. As another example, in certain embodiments, the terms “generally parallel” and “substantially parallel” refer to a value, amount, or characteristic that departs from exactly parallel by less than or equal to 15 degrees.

[0035] The scope of the present disclosure is not intended to be limited by the specific disclosures of preferred embodiments in this section or elsewhere in this specification, and may be defined by claims as presented in this section or elsewhere in this specification or as presented in the future. The language of the claims is to be interpreted broadly based on thelanguage employed in the claims and not limited to the examples described in the present specification or during the prosecution of the application, which examples are to be construed as non-exclusive.

[0036] Of course, the foregoing description is that of certain features, aspects and advantages of the present invention, to which various changes and modifications can be made without departing from the spirit and scope of the present invention. Moreover, the devices described herein need not feature all of the objects, advantages, features and aspects discussed above. Thus, for example, those of skill in the art will recognize that the invention can be embodied or carried out in a manner that achieves or optimizes one advantage or a group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein. In addition, while a number of variations of the invention have been shown and described in detail, other modifications and methods of use, which are within the scope of this invention, will be readily apparent to those of skill in the art based upon this disclosure. It is contemplated that various combinations or subcombinations of these specific features and aspects of embodiments may be made and still fall within the scope of the invention. Accordingly, it should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the discussed devices.

Claims

WHAT IS CLAIMED IS:

1. A method for growing ultra-long carbon nanotubes, comprising: operating a chemical vapor deposition (CVD) system to grow a carbon nanotube; monitoring with one or more sensors a real-time behavior of a catalyst of the CVD system; and dynamically adjusting with an electronic controller operating process conditions of the CVD system in real-time based on the monitored real-time behavior of the catalyst to increase an amount of time the catalyst is active to facilitate growth of the carbon nanotube.

2. The method of Claim 1, wherein the carbon nanotube is an ultra-long carbon nanotube having a length greater than 5 mm.

3. The method of any preceding claim, wherein the catalyst includes one or more catalytic particles.

4. The method of any preceding claim, wherein monitoring the real-time behavior of the catalyst includes using Raman spectroscopy of the catalyst to characterize the catalyst or identify catalytic behavior.

5. The method of any preceding claim, wherein monitoring the real-time behavior of the catalyst includes monitoring in real-time one or more of an operating temperature of a furnace of the CVD system, an operating pressure of the furnace, a flow rate of a carbon carrying gas flowing through the furnace, and a composition of the carbon carrying gas flowing through the furnace.

6. The method of Claim 5, wherein monitoring the real-time composition of the carbon carrying gas includes monitoring an amount of carbon in the carbon carrying gas.

7. The method of Claim 6, wherein adjusting operating process conditions of the CVD system includes adjusting in real-time one or more of an operating temperature of a furnace of the CVD system, an operating pressure of the furnace, a flow rate of a carbon carrying gas flowing through the furnace, and a composition of the carbon carrying gas flowing through the furnace.

8. The method of Claim 7, wherein adjusting the real-time composition of the carbon carrying gas includes adding an amount of steam to the carbon carrying gas if an amount ofcarbon in the carbon carrying gas is higher than desired or adding an additional amount of carbon carrying gas if an amount of carbon is lower than desired.

9. The method of any of Claims 1-8, wherein the electronic controller is a proportional-integral-derivative (PID) controller.

10. The method of any of Claims 1-8, wherein the electronic controller is a neural network controller.

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