METHOD AND APPARATUS FOR PRODUCING NANOMATERIAL

Abstract

A method for producing nanomaterial comprising carbon is disclosed. The method comprises introducing a combination of two or more carbon sources into a synthesis reactor; decomposing at least partially the two or more carbon sources in the synthesis reactor to release carbon from the two or more carbon sources; and synthesizing the nanomaterial comprising carbon from the released carbon in the synthesis reactor.

Claims

1. A method for producing nanomaterial comprising carbon, the method comprising: introducing a combination of two or more carbon sources into a synthesis reactor; decomposing at least partially the two or more carbon sources in the synthesis reactor to release carbon from the two or more carbon sources; and synthesizing the nanomaterial comprising carbon from the released carbon in the synthesis reactor.

2. The method of claim 1, wherein decomposing at least partially the two or more carbon sources in the synthesis reactor to release carbon from the two or more carbon sources is done by providing energy to the synthesis reactor and/or by introducing a decomposing reagent.

3. The method of claim 1, further comprising introducing one or more promoters into the synthesis reactor.

4. The method of claim 1, further comprising introducing one or more catalysts into the synthesis reactor, wherein synthesizing the nanomaterial comprising carbon comprises synthesizing the nanomaterial comprising carbon from the released carbon and the one or more catalysts.

5. The method of claim 1, further comprising purifying the synthesized nanomaterial comprising carbon by introducing a purifying reagent.

6. The method of claim 1, further comprising functionalizing the synthesized nanomaterial comprising carbon by introducing a functionalizing reagent.

7. The method of claim 1, wherein at least one of the carbon sources is introduced as a liquid, aerosol or gas into the synthesis reactor.

8. The method of claim 1, wherein at least one of the carbon sources is selected from a group of: elemental carbon, a molecule or polymer containing one or more carbon atoms SP, SP2 or SP3 bonded to each other and/or to oxygen, one or more hydroxyl groups, nitrogen, one or more nitroso groups, one or more amine groups and/or one or more sulfonate groups, an organic compound, an oxide of carbon, a carbide, a carbonate and a cyanide.

9. The method of claim 8, wherein one or more of the organic compounds is a hydrocarbon or a carbohydrate.

10. The method of claim 4, wherein the catalyst is a bulk metal or alloy, or a material comprising a metal or an alloy.

11. The method of claim 1, wherein providing energy into the synthesis reactor is performed by heating.

12. The method of claim 1, wherein a combination of two carbon sources including a first carbon source and a second carbon source is introduced into the synthesis reactor.

13. The method of claim 12, wherein the molar ratio of the first carbon source to the second carbon source in the synthesis reactor is between 1:10000000 and 10000000:1.

14. The method of claim 1, wherein a combination of three carbon sources is introduced into the synthesis reactor.

15. The method of claim 1, wherein at least one of the carbon sources is carbon monoxide (CO).

16. The method of claim 1, wherein at least one of the carbon sources is ethylene or toluene.

17. The method of claim 1, wherein the nanomaterial comprising carbon is a high aspect ratio molecular (HARM) material comprising carbon, graphene or fullerene.

18. The method of claim 17, wherein the high aspect ratio molecular (HARM) material comprising carbon is a carbon nanotube (CNT), a carbon nanobud (CNB), a carbon nanowire, a carbon nanoribbon, a graphinated, carbon nanotube, a carbon nanohorn, a carbon fiber, a carbon peapod, a carbon nitrogen nanotube or a carbon boron nanotube.

19. The method of claim 1, further comprising introducing a substrate into the synthesis reactor, wherein synthesizing the nanomaterial comprising carbon from the released carbon comprises synthesizing the nanomaterial comprising carbon from the released carbon on the substrate.

20. Use of the method according to claim 1 in fabrication of a transistor, a flexible electronic device, a touch screen, a sensor, a photonic device, an electrode for a solar cell, a lighting device , a sensing device or a display device.

21. An apparatus for producing nanomaterial comprising carbon, the apparatus comprising means for performing the method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] For a more complete understanding of example embodiments of the present invention, reference is now made to the following descriptions taken in connection with the accompanying drawings in which:

[0041] FIG. 1 shows the method according to an embodiment of the present invention.

[0042] FIG. 2 is a graph showing the improved performance of CNT material by the use of multiple carbon sources according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0043] An explanation of the main principles of the present invention follows based on the examples described below. These examples are for purposes of illustration only and are not intended to limit the scope of the invention in any way.

[0044] A method according to an exemplary embodiment of the invention is shown in FIG. 1. The method is carried out in a synthesis reactor 101. Two or more carbon sources are first introduced into the synthesis reactor. There are two carbon sources shown in FIG. 1, namely carbon source 1 and carbon source 2, however the present invention is not limited to two sources of carbon and may include three, four, five or more. It may be preferable that the carbon sources may have similar or different behavior in the synthesis reactor. For instance, it may be preferable that the two or more carbon sources have different decomposition temperatures or chemical decomposition dynamics so that, even if the reactor conditions vary in time or in space, synthesis of the nanomaterial can proceed uninterrupted or at an optimal or near optimal condition, thus improving the robustness of the production process. The carbon sources are materials which contain carbon that can be released for the formation of nanomaterials comprising carbon. For example, a carbon source can be carbon or carbon containing compounds including, but not limited to, carbon monoxide, alcohols, hydrocarbons and carbohydrates. An example of a carbon source is ethylene, styrene, toluene, and carbon monoxide. In case of two carbon sources, the molar ratio of the first carbon source to the second carbon source may vary between 1:1000000 and 1000000:1.

[0045] At least one of the carbon sources 1 and 2 may be introduced into the synthesis reactor 101 via an inlet 102. The inlet 102 may be a pipe, a nozzle or any other suitable structure. The carbon sources can be carbon or carbon containing compounds including, but not limited to, carbon monoxide, alcohols, hydrocarbons and carbohydrates. The carbon sources can be introduced as a liquid, aerosol, gas, aquasol or a solid substance.

[0046] According to the method, a means of releasing carbon from the carbon sources by carbon source decomposition is provided. According to the embodiment shown on FIG. 1, the synthesis reactor 101 may also comprise an energy source 103, for example a heater. Other energy sources are available according to the invention, for example (but not limited to) electrical, conductive, inductive, resistive, radio-frequency, electromagnetic radiation, laser, microwave, vibrational, mechanical, or acoustic sources. The energy source 103 is can be located inside the synthesis reactor 101, as shown in the Figure, or it may be part of the synthesis reactor 101 or located outside of it. Reactants can also be introduced into the reactor to react with a carbon source to release carbon or transform the carbon source into a form from which carbon can be more easily or more controllably released.

[0047] Next, energy may be provided to the reactor 101. The energy can be provided from any of the above listed sources or by other means from the energy source 103. When energy is provided and communicated to the carbon sources, carbon is released from the carbon sources as indicated by step 104. The carbon in step 104 may be released from both sources simultaneously or from one at a time, i.e. in a sequence. The combination of two or more sources increases the range of conditions in which carbon can be released into the synthesis reactor 101.

[0048] A chemical reagent that causes decomposition 104 of the carbon sources to release carbon can be provided into the reactor 101 in addition to, or instead of, the energy produced by the energy source 103.

[0049] A promoter and/or a catalyst may be introduced into the synthesis reactor 101 in an optional step 105 (as shown by a dashed arrow). The promoter and/or catalyst may be introduced before providing energy into the reactor 101, during this step or after this step. The promoter and/or catalyst may be introduced as pre-made promoter and/or catalyst particles, or as promoter and/or catalyst precursor particles which can be converted into promoter and/or catalyst particles in the synthesis reactor 101.

[0050] A catalyst can be heated to decompose and release or synthesize the catalyst material to form a catalyst particle. Alternatively, a catalyst precursor can be put in contact with a reagent to react with the catalyst precursor to synthesize the catalyst material to form a catalyst particle. Other means of conditioning a catalyst particle precursor particle is possible according to the invention. For the production of nanomaterials comprising carbon with further controlled properties, the catalyst particles can be classified according to, for instance, mobility or size and by, for instance, differential mobility analyzers (DMA) or mass spectrometers. Other methods and criteria for classification are possible according to the present invention and the preceding examples are not intended to limit the scope of the invention in any way.

[0051] A promoter covers all materials in gaseous, liquid, solid or any other form which promote, accelerate, or otherwise increase or improve the growth rate of nanomaterials or aid in controlling one or more properties of the nanomaterial produced or to be produced. Preferable promoters are sulfur, phosphorus or nitrogen elements or their compounds. For avoidance of doubt, CO.sub.2 acts as a promoter according to the present invention, and, although it contains carbon, it is not a carbon source since it does not release contribute carbon to the synthesis as do carbon sources according to the invention. The promoter can act as a reagent for the reaction with a carbon source to alter its decomposition rate, and e.g. hydrogen can be used as such promoter. Other promoter compounds known in the art can be used according to the present invention and these examples are not intended to limit the scope of the invention in any way.

[0052] As the next step shown on FIG. 1, nanomaterial comprising carbon is synthesized from the released carbon. The synthesis may take place in the gas phase, liquid phase or solid phase, e.g. on a substrate. If a catalyst and/or promoter are introduced, the nanomaterial comprising carbon can be synthesized from the released carbon as well as interaction with the catalyst and/or promoter.

[0053] The nanomaterial comprising carbon synthesized by the method according to the present invention may be a high aspect ratio molecular structure (HARMs), graphene or fullerene. In case of HARMS, the nanomaterial may be a carbon nanotube (CNT), a carbon nanobud (CNB), a carbon nanowire, a carbon nanoribbon, a graphinated, carbon nanotube, a carbon nanohorn, a carbon fiber, a carbon peapod, a carbon nitrogen nanotube or a carbon boron nanotube.

[0054] In an optional step 106, the synthesized nanomaterial may be purified and/or functionalized by introducing a purifying and/or functionalizing reagent. Purification can be done, for example, to remove undesirable amorphous carbon or other reaction by-products, coatings and/or catalyst particles encapsulated in the carbon nanomaterial. As a purifying reagent, any compounds or their derivatives or decomposition products formed in situ in the reactor, which preferably react with amorphous carbon or other synthesis by-products rather than with the synthesized carbon nanomaterial (e.g. graphitized carbon in the case of CNTs), can be used. Examples of such reagents include alcohols, ketones, organic and inorganic acids. Other reagents are possible according to the present invention. Other reagents are possible according to the present invention and these examples are not intended to limit the scope of the invention in any way.

[0055] A functionalizing reagent can be used to attach one or more chemical groups to the nanomaterial comprising carbon to alter its properties. Functionalization the nanomaterials may change such properties such as solubility and electronic structure (for example, varying from wide band gap via zero-gap semiconductors to CNTs with metallic properties). As an example, functionalization such as doping of CNTs by lithium, sodium, or potassium elements leads to the change of the conductivity of CNTs, namely, to obtain CNTs possessing superconductive properties. According to the present invention, the functionalizing reagent can be introduced before, during or after the nanomaterial synthesis.

[0056] Purification processes are generally used to remove undesirable by-products, precursors or catalyst, such as amorphous carbon coatings, intermediate reaction products and/or catalyst particles encapsulated in or dispersed around the carbon nanomaterial. This procedure may take significant time and energy, often more than required for the nanomaterial production itself. In the present invention it is possible to have one or more separated heated nanomaterial reactors/reactor sections, where one reactor or section of the reactor is used to produce the carbon nanomaterials and the other(s) are used for, for instance, purification or functionalization such as doping. It is also possible to combine the growth and functionalization steps. Amorphous carbon, deposited on the surface of carbon nanomaterial, can be removed in one or more subsequent reactors/reactor sections by, for instance, heat treatment and/or addition of special compounds which, for instance, form reactive radicals (such as OH), which react with undesirable products rather than with carbon nanomaterial. One or more subsequent reactors reactors/sections can be used for e.g. the removal of catalyst particles from the carbon nanomaterial by creating the conditions where the catalyst particles evaporate or react. Other processing steps are possible according to the present invention.

[0057] If the synthesis is carried out e.g. as an aerosol process, all or a sampled part of the resulting raw nanomaterial product can be collected directly from the gas phase by means known in the art, and/or incorporated into a functional product material which can further be incorporated in devices.

EXAMPLES

[0058] Unless otherwise stated, in the following examples, a resistively heated tubular furnace was used for carbon nanomaterial synthesis, ferrocene was used as precursor material for iron catalyst particles, carbon monoxide was used as carbon source 1, and the resulting aerosol product was collected on a nitrocellulose filter and transferred to a transparent polymer (PET) substrate for transmission and conductivity tests. The synthesized nanomaterial comprising carbon is carbon nanotubes (CNTs). The below examples are summarized in FIG. 2.

Example 0

[0059] Single Carbon Source Base Case. This example is provided for comparison purposes only.

[0060] Single Carbon Source (Mole Fraction): CO (0.978)

[0061] Catalyst Precursor (Mole Fraction): Ferrocene (9.65e-6)

[0062] Promoter (Mole Fraction): CO2 (0.02214)

[0063] Reactor Peak Set Temperature: 840 C

[0064] Sheet Resistance at 90% Transmission: 155 Ohm/sq.

Example 1

[0065] Carbon Source 1 (Mole Fraction): CO (0.986)

[0066] Carbon Source 2 (Mole Fraction): Toluene (1.03e-6)

[0067] Additional Carrier (Mole Fraction): N2 (2.76e-5)

[0068] Catalyst Precursor (Mole Fraction): Ferrocene (3.5e-6)

[0069] Promoter ((Mole Fraction): CO2 (0.01381)

[0070] Reactor Peak Set Temperature: 840 C

[0071] Sheet Resistance at 90% Transmission: 132 Ohm/sq.

Example 2

[0072] Carbon Source 1 (Mole Fraction): CO (0.984)

[0073] Carbon Source 2 (Mole Fraction): Toluene (5.85e-6)

[0074] Additional Carrier (Mole Fraction): N2 (1.58e-4)

[0075] Catalyst Precursor (Mole Fraction): Ferrocene (3.5e-6)

[0076] Promoter (Mole Fraction): CO2 (0.01381)

[0077] Reactor Peak Set Temperature: 840 C

[0078] Sheet Resistance at 90% Transmission: 148 Ohm/sq.

Example 3

[0079] Carbon Source 1 (Mole Fraction): CO (0.980)

[0080] Carbon Source 2 (Mole Fraction): Styrene (0.000503)

[0081] Additional Carrier (Mole Fraction): N2 (0.00051)

[0082] Catalyst Precursor (Mole Fraction): Ferrocene (4.6e-6)

[0083] Promoter (Mole Fraction): CO2 (0.01882)

[0084] Reactor Peak Set Temperature: 840 C

[0085] Sheet Resistance at 90% Transmission: 121 Ohm/sq.

Example 4

[0086] Carbon Source 1 (Mole Fraction): CO (0.983)

[0087] Carbon Source 2 (Mole Fraction): Ethylene (0.000157)

[0088] Additional Carrier (Mole Fraction): None

[0089] Catalyst Precursor (Mole Fraction): Ferrocene (3.5e-6)

[0090] Promoter (Mole Fraction): CO2 (0.01652)

[0091] Reactor Peak Set Temperature: 840 C

[0092] Sheet Resistance at 90% Transmission: 114 Ohm/sq.

Example 5

[0093] Carbon Source 1 (Mole Fraction): CO (0.662)

[0094] Carbon Source 2 (Mole Fraction): Ethylene (0.000208)

[0095] Additional Carrier (Mole Fraction): N2 (0.00051)

[0096] Catalyst Precursor (Mole Fraction): Ferrocene (8.2e-7)

[0097] Promoter 1 (Mole Fraction): CO2 (0.00621)

[0098] Promoter 2 (Mole Fraction): H2 (0.33115)

[0099] Promoter 3 (Mole Fraction): Thiophene (6.7e-7)

[0100] Reactor Peak Set Temperature: 860 C

[0101] Sheet Resistance at 90% Transmission: 83 Ohm/sq.

Example 6

[0102] Carbon Source 1 (Mole Fraction): CO (0.662)

[0103] Carbon Source 2 (Mole Fraction): Ethylene (0.000167)

[0104] Additional Carrier (Mole Fraction): N2 (0.00051)

[0105] Catalyst Precursor (Mole Fraction): Ferrocene (8.2e-7)

[0106] Promoter 1 (Mole Fraction): CO2 (0.00621)

[0107] Promoter 2 (Mole Fraction): H2 (0.33115)

[0108] Promoter 3 (Mole Fraction): Thiophene (6.7e-7)

[0109] Reactor Peak Set Temperature: 860 C

[0110] Sheet Resistance at 90% Transmission: 97 Ohm/sq.

Example 7

[0111] Carbon Source 1 (Mole Fraction): CO (0.662)

[0112] Carbon Source 2 (Mole Fraction): Ethylene (0.000125)

[0113] Additional Carrier (Mole Fraction): N2 (0.00051)

[0114] Catalyst Precursor (Mole Fraction): Ferrocene (8.2e-7)

[0115] Promoter 1 (Mole Fraction): CO2 (0.00621)

[0116] Promoter 2 (Mole Fraction): H2 (0.33115)

[0117] Promoter 3 (Mole Fraction): Thiophene (6.7e-7)

[0118] Reactor Peak Set Temperature: 860 C

[0119] Sheet Resistance at 90% Transmission: 131 Ohm/sq.

[0120] As can be seen on FIG. 2, multiple carbon sources are found to reduce the sheet resistance (i.e. increase the conductivity) at a given transparency. In the above examples 90% transmission of 550 nm wavelength light was the given transparency. Thus, and quality of conductive film is improved. Electrical Rate is defined as the conductivity produced over a given time or with a given material input. The increased conductivity also increases the yield and quality of conductive film by increasing the electrical rate.

[0121] The peak temperature used in the above examples, i.e. 860 C, is not to be understood as a limit or preferred temperature range for the method. Higher temperatures above 860 or other temperatures between 700 and 1300 C can further improve synthesis rates, yields and/or material quality, depending on, for instance, the decomposition temperature of the carbon sources used.

[0122] Similarly, a wider range of carbon source, reagent, catalysts and promoter mole fractions can be used. The examples above are not to be interpreted as a limit or preferred mole fraction range for the method. A wider range of conditions, e.g. mole fractions of carbon sources between 1:1 and 1000000:1, can further improve, for instance, synthesis rates, yields and/or material quality.

[0123] As it is clear to a skilled person, the invention is not limited to the examples described above but the embodiments can freely vary within the scope of the claims.